ABB Network Partner

User´s manual andTechnical description

SGR

SGB

SGF

SPCD 3D53

TRIP

RESETSTEP

0021

A

PROGRAM

IRFL3L2L1

3 >I∆

n1 II /

n2 II /

nd II /

d1fd5f II / %> [ ]

d1fd2f II / %> [ ]

S %[ ]

nI/P %[ ]

n2tp II /

2IdI1I

>>

d1fd5f II / %[ ]>>

SGR

SGB

SGF

SPCD 2D55

TRIP

PROGRAM

RESETSTEP

0029

A

>I∆ 01>I∆ 02

1 n/

2 n/

>2f 1f/ %[ ]( )01

>2f 1f/ %[ ]( )02

IRFd1I01I d2I 02IΣ 1I Σ 2I

n/ %[ ]2 IP

n/ %[ ]1 IP

I I

I I

01 n/I I

02 n/I I

I I I

I I I

01 s[ ]>t

02 s[ ]>t

01 / Σ 1 %[ ]I I

02 / Σ 2I I %[ ]

SGR

SGB

SGF

SPCJ 4D28

TRIP

PROGRAM

RESETSTEP

L1 L2 L3 o IRF

3 >II

IIII

> nI I/

k

n>>I I/

k 0

n0 >I I/

0023

A

nI/I >>>

>>t [ ]s

st >>> [ ]

s0 >t [ ]

0t s[ ]n0I I/>>

>t [ ]s

>t [ ]s∆>I∆

>>

%[ ]

RS 621 Ser.No.

SPAD 346 C

2

5

0199

A

18...80 V –

80...265 V ~–

fn = 50Hz

60Hz

U1

0

SPCD 3D53

123

45678A

/

BS1

BS2

BS3

BS4

BS5

0 00

nI = 1A 5A

nI = 1A 5A ( )02I

nI = 1A 5A

nI = 1A 5A ( )2I( )1I

( )01I

0

SPCD 2D55

000

1234567890IIA

BS1

BS2

U3

SPCJ 4D28

CBFP Trip

I > Start

I 0 > Start

I > Trip∆

1234567890IIA

I 0 > Trip

I > Trip

>>I Start

>>I Trip

>>>I Start

>>>I Trip

>>I 0 Start

>>I 0 Trip

OPERATION INDICATORS

U2

0 000

BS4CBFP Trip

BS5

CBFP Trip

I 01 > Start∆I 01 > Trip∆

I 02 > Start∆I 02 > Trip∆

BS3

I 2f ( )I 02 >Block

I 2f ( )I 01 >Block

3 I > Trip∆>>

I d2f > Block

3 I Trip∆

I d5f > Block

auxU

SPAD 346 CStabilized Differential Relay

2

1MRS 750096-MUM EN

Issued 96-08-08Version D (replaces 34 SPAD 5 EN1)CheckedApproved

Data subject to change without notice

StationAutomation

SPAD 346 CStabilized

Differential Relay

Contents Features .......................................................................................................................... 3Application ..................................................................................................................... 4Description of function .................................................................................................. 4

Three-phase stabilized differential relay module SPCD 3D53 ................................... 4Earth-fault relay module SPCD 2D55....................................................................... 6Combined overcurrent and earth-fault relay module SPCJ 4D28.............................. 8

Connection diagram ....................................................................................................... 9Connections ................................................................................................................. 10Control input and output relay module ........................................................................ 11Intermodular signals ..................................................................................................... 12Power supply module ................................................................................................... 13Operation indicators ..................................................................................................... 14Technical data .............................................................................................................. 15Recommendations for current transformers .................................................................. 18Circuit-breaker control ................................................................................................. 20Application examples .................................................................................................... 21Setting instructions ....................................................................................................... 25Commissioning ............................................................................................................ 28Testing ......................................................................................................................... 28Maintenance and service ............................................................................................... 33Spare parts .................................................................................................................... 33Delivery alternatives ..................................................................................................... 33Order numbers ............................................................................................................. 34Information required with order ................................................................................... 34Dimensioned drawings and mounting .......................................................................... 35

In addition to this general part the complete manual of the stabilized differential relay includesthe following individual documents:

Stabilized differential relay module SPCD 3D53 1MRS 750097-MUM ENEarth-fault relay module SPCD 2D55 1MRS 750098-MUM ENCombined overcurrent and earth-fault relay module SPCJ 4D28 1MRS 750093-MUM ENGeneral characteristics of D-type SPC relay modules 1MRS 750066-MUM EN

3

Features Integrated three-phase differential relay, over-current relay and earth-fault relay

Stabilized three-phase differential relay provid-ing winding short-circuit and interturn faultprotection for two-winding transformers andgenerator-transformer units and winding short-circuit protection for generators.

Earth-fault protection for transformer HV andLV side windings according to the desired prin-ciple: the stabilized differential current princi-ple, the high-impedance principle, the calcu-lated or measured residual current principle orthe neutral current principle

Three-stage overcurrent protection for trans-formers and generators and two-stage back-upprotection for earth-fault protection

The operation characteristic of the differentialrelay easily adapted for different applications

Short operate times, even with partially satu-rated current transformers

Stabilization prevents unwanted operations atfaults outside the protected area and trans-former inrush currents

Blocking based on the ratio of the second har-monic and the fundamental component of thedifferential current prevents unwanted opera-tions at transformer inrush currents

Blocking based on the ratio of the fifth har-monic and the basic frequency component ofthe differential current prevents operation inharmless situations of transformer overexcitation- can be eliminated if the ratio of the fifthharmonic and the basic frequency componentincreases at high overvoltages

No interposing transformers are needed for theprotection of two-winding transformers - nu-merical vector group matching on HV and LVside

Wide CT ratio correction range - accurate cor-rection allowed by digital setting

Sensitive phase current and phase angle displaysfacilitate the checking of measurement circuitconnection and vector group matching

Four trip and four signal relay outputs availableto the protection design engineer

Five programmable external control inputs in-tended for the indication and retransmission ofalarm and trip signals of gas relays, oil tempera-ture sensors and other sensors of transformerauxiliary devices

Adjustable CBFP operate time to improve reli-ability of operation

Integrated disturbance recorder capable of re-cording currents and digital signals - signals tobe used for triggering selectable

High immunity to electrical and electromag-netic interference allows the relay to be used insevere environments

High availability and system reliability due tocontinuous supervision of hardware and soft-ware

4

Application The stabilized differential relay SPAD 346 C isdesigned to be used to protect two-windingtransformers and generator-transformer unitsagainst winding short-circuit, interturn fault,earth fault and short circuit and to protect

generators against winding short-circuit andshort circuit. The relay can also be used for theprotection of a three-winding transformer pro-vided 75% of the short circuit power is fed fromthe same direction.

Description ofoperation

The integrated differential relay SPAD 346 Cincludes three independent relay modules: athree-phase stabilized differential relay moduleSPCD 3D53, an earth-fault relay module SPCD2D55 and a combined overcurrent and earth-fault relay module SPCJ 4D28. The rated cur-rents of the relay are 1 A and 5 A. The HV and

LV side may use the same or different ratedcurrents.

Below a short description of the features of theprotection relay modules. The manuals for theseparate relay modules describe the modulesmore in detail.

In power transformer protection differentialcurrent is caused by CT errors, varying tapchanger positions, transformer no-load current,transformer inrush currents, transformeroverexcitation in overvoltage and underfre-quency situations, and CT saturation at highcurrents passing through the transformer. Dif-ferential current caused by CT errors and tap-changer position grows at the same per cent ratioas the load current increases. In the protection ofgenerators the differential current is caused byCT errors and saturation of the CTs in situa-tions where high currents pass through thetransformer.

High currents passing through the object to beprotected may be caused by short circuits out-side the protected area, large currents fed by thetransformer or the generator in motor start-up

The differential relay module SPCD 3D53 pro-vides protection for winding short-circuit andinterturn faults. The differential relay comparesthe phase currents on both sides of the object tobe protected. Should the differential current ofthe phase currents in one of the phases exceedthe setting of the stabilized operation character-istic or the instantaneous protection stage of themodule, the module provides an operate signal.Different amplitudes or phase difference of thecurrents may be the reason for the differentialcurrent.

Interposing current transformers have normallybeen used in the differential protection of trans-

formers to obtain vector group matching and tomatch the secondary currents of the main trans-formers. Interposing CTs have also been used toeliminate the zero-sequence components of thephase currents at earth faults occurring outsidethe protected area. The differential current relaySPAD 346 C eliminates the use of interposingtransformers for the protection of two-windingtransformers as the differential relay moduleallows the transformer vector group matching,the CT ratio correction and the elimination ofthe zero-sequence component of the phase cur-rents to be digitally implemented on the HVand/or the LV side.

Three-phasestabilizeddifferentialrelay moduleSPCD 3D53

Stabilizeddifferentialcurrent stage

or transformer inrush situations. Due to thesecircumstances the operation of the differentialrelay has been stabilized in respect of the loadcurrent. In a stabilized differential relay thedifferential current required for relay operationis higher, the higher the load current is. Thestabilized operation characteristic of the differ-ential relay module and the setting range of thecharacteristic is presented in the description ofthe differential relay module SPCD 3D53.

The operation of the differential relay moduleSPCD 3D53 is based on the fundamental fre-quency components. Operation based on fun-damental frequency components is accurate andstable: the DC component and harmonics of thecurrent do not cause unwanted operation of theprotection stage.

5

Blocking basedon the second har-monic of the differen-tial current

The blocking also prevents unwanted operationat recovery and sympathetic magnetizing in-rush. At recovery inrush the magnetizing cur-rent of the transformer to be protected increasesmomentarily when the voltage returns to nor-mal after clearance of a fault outside the pro-tected area. Sympathetic inrush is caused by atransformer, which runs in parallel with theprotected transformer already connected to thenetwork, being energized.

The connection of the power transformer againsta fault inside the protected area does not delaythe operation of the relay module, because insuch a situation the blocking based on thesecond harmonic of the differential current isprevented by a separate algorithm based on thewaveform and the rate of change of the differen-tial current.

Transformer magnetizing inrush currents occurwhen energizing the transformer after a periodof deenergization. The inrush current may bemany times the rated current and the halvingtime may be up to several seconds. To thedifferential relay inrush current represents dif-ferential current, which would cause the relay tooperate almost always when the transformer isconnected to the network. Typically, the inrushcurrent contains a large amount of second har-monics. Blocking of the operation of the stabi-lized stage of the relay at magnetizing inrushcurrent is based on the ratio of the amplitudes ofthe second harmonic digitally filtered from thedifferential current and the fundamental fre-quency Id2f/Id1f.

Inhibition of relay operation in situations ofoverexcitation is based on the ratio of the fifthharmonic and the fundamental component ofthe differential current Id5f/Id1f. At dangerouslevels of overvoltage which may cause damageto the transformer, the blocking can be auto-

matically eliminated by a separate blocking in-hibiting setting Id5f/Id1f>>. When required, theblocking based on the second and fifth har-monic of the differential current can be disa-bled.

In addition to the stabilized stage the differentialrelay module SPCD 3D53 has a separate adjust-able instantaneous stage the operation of whichis not stabilized. The instantaneous differentialcurrent stage operates when the fundamentalcomponent calculated from the differential cur-rent exceeds the set operate limit Id/In>> orwhen the instantaneous value of the differentialcurrent exceeds the level 2.5 x Id/In>>. The

setting range of the instantaneous stage Id/In>>is 5...30.

Should the stabilizing current be less than 30%of the differential current, there is most certainlya fault in the protected area. In such a situationthe set operate value Id/In>> will be halved andthe blockings of the stabilized stage are auto-matically prevented.

The differential relay module SPCD 3D53 isprovided with an integrated disturbance re-corder that is capable of recording six phasecurrents, the internal trip and blocking signalsof the module and the control input signals.Recording can be triggered by the rising orfalling edge of these signal. The recording length

is 38 cycles. The recording memory has thecapacity of storing one recording at a time.Sampling frequency is 40 samples/cycle. Therecording is downloaded by using a PC pro-gram. The recording memory has to be resetbefore a new recording is possible.

Blocking based on thefifth harmonic of thedifferential current

Instantaneousdifferentialcurrent stage

Disturbance recorder

6

Earth-faultrelay moduleSPCD 2D55

When single-phase or two-phase earth faultsoccur in the area to be protected the sensitivityof the differential protection measuring phasecurrents may not be sufficient, in particular, ifthe star point of the transformer is resistance-earthed.

The earth-fault relay module SPCD 2D55 pro-tects the HV and LV side windings of a two-

winding transformer. The earth-fault protec-tion can be implemented by four principles: thehigh-impedance principle, the numerical stabi-lized differential current principle, the residualovercurrent principle, or the neutral overcur-rent principle. The HV and LV side earth-faultprotection are quite independent of each other,so the protection principle on the HV side doesnot have to be the same as that of the LV side.

The numerical differential current stage oper-ates exclusively on earth faults occurring in theprotected area, i.e. in the area between the phaseCTs and the CT of the neutral connection. Anearth fault in this area appears as a differentialcurrent between the residual current of thephase currents and the neutral current of theconductor between the star point of the trans-former and earth. The relay measures a differen-tial current as the difference between the re-sidual current of the phase currents and neutralcurrent. An external stabilizing resistor is notrequired. (See application example 1)

At an earth fault in the protected area the phasedifference between the residual current of thephase currents and the neutral current is greaterthan 90°, i.e. the directions of the residualcurrent and the neutral current are towards theprotected area. In the calculation of the differen-tial current the directions of the residual currentand the neutral current are so weighted thatoperation is possible only if the phase differencebetween the residual current of the phase cur-rent and neutral current exceeds 90°. Thesmaller the phase difference, i.e. the closer it is to90°, the higher the differential current requiredfor operation.

The operation characteristic for the differentialprinciple is presented in the document describ-ing the earth-fault relay module SPCD 2D55.The setting range of the basic settings P1/In andP2/In is 5...50%. The operation of the numeri-cal differential current principle is stabilized inrespect of the phase currents (load current) onthe side of the winding to be protected so thatthe higher the average of the phase currents onthe concerned side the higher is the differentialcurrent required for starting.

Should the residual current of the phase currentsbe zero the neutral current exceeding the oper-

ate limit, an earth-fault has occurred in theprotected area and the relay operates when thepreset operate time has elapsed. Such a situationmay arise when the transformer is connected tothe network on the HV side against an internalearth fault on the LV side. So, in this situationthe LV side protection will operate.

When the numerical stabilized differential cur-rent principle is used the ratio of the neutralcurrent and the residual current of the phasecurrents must be greater than the setting I01/∑I1 on the HV side and greater than the settingI02/∑I2 on the LV side to allow starting of theearth-fault protection on the respective side.The settings secure the selectivity of the protec-tion taking into account the distribution of theearth-fault current between the transformerneutral and the network. The distribution of theearth-fault current depends on the ratio of thezero-sequence impedances of the transformerand the supplying network and also on theposition of the earth fault in the winding. Inaddition, the number and the location of theother star-points of the network influence thedistribution of the earth fault.

The transformation ratio correction settingsI01/In and I1/In allow correction of the neutralconnection CT and phase CT ratios on the HVside, whereas the settings I02/In and I2/In areused for the corresponding ratio corrections onthe LV side.

When the stabilized differential current princi-ple is used, the saturation of the current trans-formers in asymmetrical inrush situations doesnot cause any problems, if the operation of theearth-fault relay is set to be blocked in inrushsituations. This blocking is based on the ratio ofthe second harmonic and the fundamental fre-quency component of the neutral current I01 orI02.

Numerical stabilizeddifferential currentprinciple

7

High-impedance typeprotection

Restricted earth-fault protection (REF protec-tion) is often implemented by the high-imped-ance principle. When this principle is employedthe relay operates exclusively on faults occurringwithin the protected area. At external faultsrelay operation is inhibited by a stabilizing resis-tor mounted in the differential current circuit inseries with the matching transformer of the relay(see application examples 2 and 3).

The operation of high-impedance type protec-tion, when a fault occurs in the protected area,is based on the fact that the impedance of thecurrent transformer rapidly decreases when thecurrent transformer is saturated. The reactanceof the magnetizing circuit of a fully saturatedtransformer is zero and the impedance is formedof the winding resistance. Due to the resistorfitted in the differential current circuit the sec-ondary current of an unsaturated transformer

flows through the secondary circuit of the un-saturated transformer. The start value of theearth-fault protection is set high enough toprevent operation due to differential currentcircuit currents caused by faults outside theprotected area. The basic settings P1/In and P2/Inare used for setting the start values on the HVside and the LV side, when the high-impedanceprinciple is used. The relay starts when thedifferential current flowing to the relay exceedsthe setting. The operation is not stabilized in therelay.

At faults occurring within the protected area thecurrent transformers try to feed current into thedifferential current circuit, in which case therelay operates. To keep the resistance of thesecondary circuit as low as possible, the sum-ming point of the currents should be located asclose to the current transformers as possible.

The residual overcurrent method can be usedfor the earth-fault protection of delta-connectedwindings connected to the network which in-cludes earthed neutral points. Three phase cur-rent transformers are used. The sum of the phasecurrents, i.e. the sum of the zero-sequence cur-rents in the phases, is calculated in the relaymodule on the basis of the phase currents linkedto the relay. The three phase currents will notsum to zero for internal earth faults. Specialattention has to be paid to the operate timesettings in order to avoid unwanted operations,when the phase CTs saturate at external faults orin inrush situations.

Earth-fault protection based on neutral currentcan be used as back-up protection for the earth-fault protection.

Earth-fault protection based on these principlesstarts when the residual current or neutral cur-rent exceeds the set start limit P1/In or P2/In.The operation has a definite-time characteristic.

A blocking function based on the second har-monic of the neutral current I01 or I02 can beused in combination with the neutral currentprinciple. This blocking can also be used if thethe residual current of the phase currents isformed via an external connection by connect-ing the neutral terminals of the windings of therelay’s phase current matching transformers tothe 5 A or 1 A terminal of the neutral currentmatching transformer I01 or I02. Should theresidual current be numerically formed insidethe relay module, this blocking function cannotbe used.

Residual overcurrentprinciple and neutralovercurrent principle

The definite operate time t01> and t02> can beseparately set for the the HV side and the LVside in the range 0.03...100 s.

The earth-fault relay module SPCD 2D55 isprovided with an integrated disturbance re-corder capable of recording six phase currents,two neutral currents, the internal start and block-ing signals of the module and the control inputsignals. Recording can be triggered by the risingor falling edge of these signals. The length of the

recording is about 30 cycles and the capacity ofthe recording memory is one recording at atime. The sampling frequency of the distur-bance recorder is 40 samples/cycle. A PC pro-gram can be used for downloading the recordingfrom the memory. The recording memory hasto be reset before a new recording is possible.

Operate time

Disturbance recorder

8

Combined over-current and earth-fault relay moduleSPCJ 4D28

The overcurrent unit of the combined overcur-rent and earth-fault relay module SPCJ 4D28 isdesigned to be used for single-phase, two-phaseand three-phase short-circuit protection of powertransformers and generators. The overcurrentprotection includes three overcurrent protec-tion stages: stage I>, stage I>> and stage I>>>. Anovercurrent stage starts once the current on oneof the phases exceeds the setting value of thestage. If the overcurrent situation lasts longenough to exceed the operate time set for themodule, the stage that started provides a tripsignal to the circuit breaker.

The earth-fault unit of the combined overcur-rent and earth-fault relay module SPCD 4D28is intended to be used for non-directional earth-fault protection and it is well suited for earth-fault back-up protection for power transform-ers. The earth-fault unit is provided with twoprotection stages: a low-set stage I0> and a high-set stage I0>>. The starting of the stage providesa start signal which can be linked to the desiredoutput signal. If the earth fault still persists,when the set operate time elapses, the concernedstage provides an operate signal.

The low-set stages (I> and I0>) may have eithera definite time or an inverse time operatingcharacteristic, whereas the high-set stages onlyhave a definite time mode of operation. Theoperation of the different stages can be totallyinhibited by selecting the appropriate setting forthe configuration switches.

In addition, the combined overcurrent and earth-fault relay module SPCJ 4D28 provides protec-tion against phase discontinuity ∆I>. The phasediscontinuity protection monitors the mini-mum and maximum phase current and calcu-lates the differential current ∆I between thephases. The phase discontinuity protection unitcan be used for monitoring the condition of thenetwork. In the protection of Yy-connectedpower transformers the phase discontinuity pro-tection can have a signalling function at least. Incertain cases the phase discontinuity protectioncan be used for unbalance protection of smallgenerators.

The combined overcurrent and earth-fault relaymodule SPCJ 4D28 measures currents appliedto the HV side phase current inputs IL1, IL2 andIL3 and the LV side neutral current input I02 ofthe relay.

The relay modules SPCD 3D53, SPCD 2D55and SPCJ 4D28 are provided with integratedcircuit-breaker failure protection (CBFP), al-

lowing a secured circuit breaker trip system tobe implemented.

Circuit-breakerfailure protection

9

Connectiondiagram

Fig. 1. Connection diagram for the stabilized differential relay SPAD 346 C.

Uaux Auxiliary voltageTS1...TS4 Output relay (heavy-duty types)SS1...SS4 Output relayIRF Self-supervision output relayBS1...BS5 External control inputsU1 Three-phase stabilized differential relay module SPCD 3D53U2 Earth-fault relay module SPCD 2D55U3 Combined overcurrent and earth-fault relay module SPCJ 4D28U4 I/O relay module SPTR 9B31U5 Power supply module SPGU 240A1 or SPGU 48B2U6 Energizing input module SPTE 8B18TS1...TS4 Output signals (for heavy-duty output relays)SS1...SS4 Output signalsSERIAL PORT Serial communication portSPA-ZC_ Bus connection moduleRx/Tx Receiver (Rx) and transmitter (Tx) for the connection of optical fibres

X1/18

L1

L2

L3

P1P2

S1S2 S2S1

P2P1

U1 IRF

+ -

U5

+

-

(~)

(~)Uaux

U6

BS1BS2BS3BS4BS5

S1

S2

P1

P2

S1

S2

P1

P2

SS1SS2SS3SS4TS1TS2TS3TS4

SPAD 346 C

SS2

SS1

SS3

SS4

TS1

TS2

TS3

IRF

TS4

I / O

∆I >01

BS1

BS2

BS3

BS4

BS5

X1/1

X1/2

X1/3

X1/4

X1/5

X1/6

X1/7

X1/8

X1/9

X1/10

IRFX2/18X2/17X2/16

X2/14X2/15

X2/10X2/9

X2/13

X2/11X2/12

X2/8X2/7

X2/5X2/6

X2/3X2/4

+

+

+

+

+

+

+

+X1/14X1/13X1/12X1/11

TRIP

+

TRIP

TRIP

3∆I>

U4

X2/

1

X2/

2

X0/

1

X0/

2X

0/3

X0/

4

X0/

5X

0/6

X0/

7

X0/

8X

0/9

X0/

13X

0/14

X0/

15X

0/16

X0/

17X

0/18

X0/

19X

0/20

X0/

21

5 AN

X0/

25X

0/26

X0/

27

X0/

37

X0/

38X

0/39

I / O

Y / ∆

Y / ∆

U2 IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

U3

BS1BS2BS3BS4BS5

BS2BS1

1 A

5 AN

1 A

5 AN 1 A

5 AN

1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

3∆I>>

∆I >02

≅

SP

A-Z

C_

Rx Tx

X1/17X1/16X1/15

TRIP

SERIALPORT

3I>I

∆I>BS3

IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

10

Terminals The terminals of the differential relay SPAD346 C are as follows:

Terminal Contact Functiongroup interval

X0 1-2 HV side or stator star-point side phase current IL1 (5 A)X0 1-3 HV side or stator star-point side phase current IL1 (1 A)X0 4-5 HV side or stator star-point side phase current IL2 (5 A)X0 4-6 HV side or stator star-point side phase current IL2 (1 A)X0 7-8 HV side or stator star-point side phase current IL3 (5 A)X0 7-9 HV side or stator star-point side phase current IL3 (1 A)X0 13-14 LV side or stator network side phase current IL1’ (5 A)X0 13-15 LV side or stator network side phase current IL1’ (1 A)X0 16-17 LV side or stator network side phase current IL2’ (5 A)X0 16-18 LV side or stator network side phase current IL2’ (1 A)X0 19-20 LV side or stator network side phase current IL3’ (5 A)X0 19-21 LV side or stator network side phase current IL3’ (1 A)X0 25-26 HV side neutral current I01 (5 A)X0 25-27 HV side neutral current I01 (1 A)X0 37-38 LV side neutral current I02 (5 A)X0 37-39 LV side neutral current I02 (1 A)

X1 1-2 External control input BS1X1 3-4 External control input BS2X1 5-6 External control input BS3X1 7-8 External control input BS4X1 9-10 External control input BS5X1 11-12-13-14 Output relay TS4

(heavy-duty two-pole relay, see "Circuit breaker control")X1 15-16-17-18 Output relay TS3

(heavy-duty two-pole relay, see "Circuit breaker control")

X2 1-2 Auxiliary power supply. The positive pole of the dc supply isconnected to terminal 1. Auxiliary power range is marked onthe rating plate.

X2 3-4 Output relay TS2 (heavy-duty type)X2 5-6 Output relay TS1 (heavy-duty type)X2 7-8 Output relay SS4X2 9-10 Output relay SS3X2 11-12-13 Output relay SS2X2 14-15 Output relay SS1X2 16-17-18 Self-supervision (IRF) output relay

The protection relay is connected to the fibre-optic bus via a bus-connection module, typeSPA-ZC 17 or SPA ZC 21, fitted to the Dconnector on the rear panel of the relay. The

optical fibres are connected to the counter con-tacts Rx and Tx of the module through snap-onconnectors. The selector switches are set in theposition "SPA".

11

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

X2

X1

Serial Port

SPA

TS4BS2 BS3 BS4 BS5BS1

IRF SS1 SS2 SS3 SS4 TS1 U

Made in Finland

- +TS2

X0

1

I'L1

I'L2

I'L3

IL1

IL2

IL3

TS3

I01 I02

2

3

4

5

6

7

8

9

25

26

27

13

14

15

16

17

18

19

20

21

37

38

39

aux

The control input and output relay module ofthe differential relay SPAD 346 C is fitted to therear panel of the relay in the same direction asthe mother board. To remove the module, thefixing screws have to be undone and the protec-tive earth cable of the module plus the flat cableconnecting the mother board to the modulehave to be disconnected.

The control input and output relay modulecontains the output relays (8 pcs + IRF), thecontrol circuits of the relays, the electroniccircuits of the external control inputs (5 pcs) andthe D connector required for serial communica-tion. A flat cable links the output and inputsignals of the module to the mother board. Therelay module locations U1, U2 and U3 areidentical.

The output signals SS1...SS4 and TS1...TS4 ofthe mother board control an output relay withthe same designation. The operation of theprotection stages of the relay module is not fixedto any specific output relays, but the stages canbe linked to the desired output signals. In con-trast, the output relays TS1, TS2, TS3 and TS4are the only output relays capable of circuitbreaker control (see "Circuit-breaker control").The configuration of the output relay matrixswitchgroups of the relay modules is describedin the manuals of the relay modules.

Five external inputs BS1, BS2, BS3, BS4 andBS5 are available to the differential relay SPAD346 C. For example, the alarm and trip signalsfrom the power transformer gas relay and thewinding temperature sensor can be linked to theexternal control inputs. The external controlinputs can be used for:- blocking one or several protection stages of the

relay modules- direct output relay control- the indication of the primary protection relay

signals or operations- resetting the operation indicators, latched

output relays, registers and recording memory- changing the actual setting values of the relay

modules. i.e.switching from main setting val-ues to second setting values and vice versa.

The switchgroups of the relay modules are usedto specify the influence of the external controlinputs BS1...BS5 on the operation of the relayand the active state of the control inputs.

The activation of a protection stage, a blockingfunction and an external control input is indi-cated on the display of the relay module by thered code representing the event. The codes areexplained in the manuals of the relay modules.Event information is also received over the serialbus, when a protection stage, a blocking func-tion, an external control input or an outputsignal is activated.

Fig. 2. Rear view of the stabilized differential relay SPAD 346 C

Control input andoutput relaymodule

12

Intermodularsignals

The signals BS INT1, BS INT2 and BS INT3are blocking signals for the relay modules SPCD3D53 and SPCD 2D55. These blocking signalsallow one relay module to prevent the operationof another relay module fitted in another relaymodule location. An intermodular blocking sig-nal is activated when the corresponding block-ing signal of one relay module is activated. Theblocking signals BS INT1...3 are not capable ofcontrolling output relays, nor can they be used

for blocking the relay module SPCJ 4D28. Thefigure below shows how the the external controlinputs, the start, operate and blocking signals ofthe relay modules can be configured to obtainthe desired functions of the relay modules. Theswitches to be used for selecting the active stateof the signals and for configuring the latchingfeature of the output relays and the operation ofthe circuit-breaker failure protection have beenomitted.

Fig. 3. The energizing inputs, external control inputs, intermodular signals, output signals andoutput relays of the differential relay SPAD 346 C.

23

45

67

8

3∆I>

3∆I>

>

12

34

56

78

SG

B2

SG

B3

2nd

or 5

thha

rmon

icbl

ocki

ng

SG

F6

SG

F7

SG

F8

SG

F9

SG

F10

SG

F11

SGR1

SGR2

SGR3

SGR4

SGR5

SGR6

SGR7

SGR8

AR

1

∆I

>01

∆I

>02

t >

01t

>02

1 1 1 1 1 1

SG

F6

SG

F7

SG

F8

SG

F9

SG

F10

SG

F11

SGR1

2 2 2 2 2 2 SGR2

3 3 3 3 3 3 SGR3

4 4 4 4 4 4 SGR4

SG

B2

2nd

harm

.bl

ocki

ng(H

V s

ide)

5 5 5 5 5 5 SGR5

2nd

harm

.bl

ocki

ng(L

V s

ide)

6 6 6 6 6 6 SGR6

7 7 7 7 7 7 SGR7

8 8 8 8 8 8 SGR8

SGR9

SGR10

SGR11

SS

2S

S1

SS

3S

S4

TS

1T

S2

TS

3T

S4

X2/14X2/15

X2/10X2/9

X2/13

X2/11X2/12

X2/8X2/7

X2/5X2/6

X2/3X2/4

++

++

++

+

X1/18X1/17

+

X1/14X1/13

X1/12X1/11

X1/16X1/15

I ,

I ,

IL1

L2L3

I' ,

I' ,

I'L1

L2L3 I 0

1I 0

2

BS

1

SPCD 2D55 (U2)

SPCD 3D53 (U1)

AR

1

AR

2

AR

3

SS

1

SP

AD

346

C

BS

2B

S3

BS

4B

S5

AR

2

AR

3

BS

INT

1

BS

INT

2

BS

INT

3

TS

1

SS

2

TS

2

SS

3

TS

3

SS

4

TS

4

SS

1

TS

1

SS

2

TS

2

SS

3

TS

3

SS

4

TS

4

AR

1

AR

2

AR

3

BS

INT

1

BS

INT

2

BS

INT

3

SG

B3

1 1 1 1 1 1

2 2 2 2 2

3 3 3 3 3

4 4 4 4 4

5 5 5 5 5

6 6 6 6 6

7 7 7 7 7

8 8 8 8 8

12

34

56

78

12

34

56

78

12

34

56

78

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

I>I>

>

SPCJ 4D28 (U3)

I>>

>∆I

>

SG

F7

12

34

56

SG

F8

12

34

SGB1 1 2 3 4 6

SGB2 1 2 3 4

SGB3 1 2 3 4

I >

0I

>>

0

t>t>

>t>

>>

∆t>

t >

0t

>>

0

SGR1

SGR2

SGR3

SGR4

SGR5

SGR6

SGR7

SGR8

SGR9

SGR10

SGR11

SS

1

TS

1

SS

2

TS

2

SS

3

TS

3

SS

4

TS

4

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

1 2 3 4 5 6 7 8

56

78

SG

F6

12

34

56

SG

F8

SS

1 TS

1 SS

2 TS

2

SS

3 TS

3

SS

4 TS

4

AR

2

AR

1

AR

3

13

Power supplymodule

The power supply module forms the voltagesrequired by the relay modules. The power sup-ply module, which is a separate unit, is locatedbehind the system front panel. The module canbe withdrawn after the system panel has beenremoved.

The power supply module is available in twoversions, SPGU 240A1 and SPGU 48B2 , whichhave different input voltages:

SPGU 240A1- rated voltage

Un = 110/120/230/240 V acUn = 110/125/220 V dc

- operation rangeU = 80...265 V ac/dc

SPGU 48B2- rated voltage

Un = 24/48/60 V dc- operation range

U = 18...80 V dc

The power supply module type SPGU 240 A1can be used for both ac voltage and dc voltage,whereas type SPGU 48 B2 is designed for dcvoltage only. The voltage range of the powersupply module of the relay is marked on thesystem panel of the relay.

The power supply module is a transformer con-nected, i.e. galvanically isolated primary andsecondary side, flyback-type dc/dc converter.The primary side of the power supply module isprotected with a fuse, F1, located on the PVCboard of the module. The fuse size of SPGU240A1 is 1 A (slow) and that of SPGU 48B2 is4 A (slow).

Fig. 4. Voltage levels of the power supply module

A green LED indicator Uaux is lit when thepower supply module is operating. The supervi-sion of the voltages supplying the electronics isintegrated into the relay modules. Should asecondary voltage deviate from its rated value by

more than 25% a self-supervision alarm will beobtained. An alarm signal will also be receivedif the power supply module has been removed orthe power supply to the module is interrupted.

+8V

+12V

-12V

+24V

Uaux

80...265 V ac & dc18...80 V dc

Unstabilized logicsvoltage

Operation amplifier voltage

Output relay coilvoltage

14

Operationindicators

SGR

SGB

SGF

SPCD 3D53

TRIP

RESETSTEP

0021

A

PROGRAM

IRFL3L2L1

3 >I∆

n1 II /

n2 II /

nd II /

d1fd5f II / %> [ ]

d1fd2f II / %> [ ]

S %[ ]

nI/P %[ ]

n2tp II /

2IdI1I

>>

d1fd5f II / %[ ]>>

SGR

SGB

SGF

SPCD 2D55

TRIP

PROGRAM

RESETSTEP

0029

A

>I∆ 01>I∆ 02

1 n/

2 n/

>2f 1f/ %[ ]( )01

>2f 1f/ %[ ]( )02

IRFd1I01I d2I 02IΣ 1I Σ 2I

n/ %[ ]2 IP

n/ %[ ]1 IP

I I

I I

01 n/I I

02 n/I I

I I I

I I I

01 s[ ]>t

02 s[ ]>t

01 / Σ 1 %[ ]I I

02 / Σ 2I I %[ ]

SGR

SGB

SGF

SPCJ 4D28

TRIP

PROGRAM

RESETSTEP

L1 L2 L3 o IRF

3 >II

IIII

> nI I/

k

n>>I I/

k 0

n0 >I I/

0023

A

nI/I >>>

>>t [ ]s

st >>> [ ]

s0 >t [ ]

0t s[ ]n0I I/>>

>t [ ]s

>t [ ]s∆>I∆

>>

%[ ]

RS 621 Ser.No.

SPAD 346 C

2

5

0199

A

18...80 V –

80...265 V ~–

fn = 50Hz

60Hz

U1

0

SPCD 3D53

123

45678A

/

BS1

BS2

BS3

BS4

BS5

0 00

nI = 1A 5A

nI = 1A 5A ( )02I

nI = 1A 5A

nI = 1A 5A ( )2I( )1I

( )01I

0

SPCD 2D55

000

1234567890IIA

BS1

BS2

U3

SPCJ 4D28

CBFP Trip

I > Start

I 0 > Start

I > Trip∆

1234567890IIA

I 0 > Trip

I > Trip

>>I Start

>>I Trip

>>>I Start

>>>I Trip

>>I 0 Start

>>I 0 Trip

OPERATION INDICATORS

U2

0 000

BS4CBFP Trip

BS5

CBFP Trip

I 01 > Start∆I 01 > Trip∆

I 02 > Start∆I 02 > Trip∆

BS3

I 2f ( )I 02 >Block

I 2f ( )I 01 >Block

3 I > Trip∆>>

I d2f > Block

3 I Trip∆

I d5f > Block

auxU

Fig. 5. Front panel of stabilized differential relay SPAD 346 C

1. The green LED Uaux on the system panel is litwhen the power supply module is operating.

2. The displays of the relay modules indicatemeasured data, setting values and recordedinformation. The operation indicators of therelay modules consist of a red digit or code onthe display and LED indicator "TRIP". Theoperation indicators, their internal prioritiesand means of resetting are explained in themanuals for the relay modules.

3. A measured value or setting value being pre-

sented on the display is recognized by yellowLED indicators on the front panel and redcodes on the display. The measured valuesand setting values are explained in the manu-als for the relay modules.

4. A permanent fault detected by the self-super-vision system is indicated by the IRF indica-tors on the separate relay modules. The faultcode appearing on the display of the modulewhen a fault occurs should be stated whenservice is ordered. The fault codes are ex-plained in the manuals of the relay modules.

15

Technical data Measuring inputsRated current In 1 A 5 ATerminal numbers X0/1-3, 4-6, 7-9 X0/1-2, 4-5, 7-8

X0/13-15, 16-18 X0/13-14, 16-17X0/19-21, 25-27 X0/19-20, 25-26X0/37-39 X0/37-38

Thermal current withstand- continuously 4 A 20 A- for 10 s 25 A 100 A- for 1 s 100 A 500 ADynamic current withstand- half-vawe value 250 A 1250 AInput impedance <100 mΩ <20 mΩRated frequency fn 50 Hz or 60 Hz

Output relaysHeavy-duty output relaysTerminal numbers X1/11-12-13-14, 15-16-17-18

X2/3-4, 5-6Rated voltage 250 V ac/dcContinuous current carrying capacity 5 AMake and carry for 0.5 s 30 AMake and carry for 3 s 15 ABreaking capacity for dc when the control circuittime constant L/R ≤40 ms at the control levels48/110/220 V dc 5 A/3 A/1 AContact material AgCdO2

Signal relaysTerminal numbers X2/7-8, 9-10, 11-12-13, 14-15

16-17-18Rated voltage 250 V ac/dcContinuous current carrying capacity 5 AMake and carry for 0.5 s 10 AMake and carry for 3 s 8 ABreaking capacity for dc when the control circuittime constant L/R ≤40 ms at the control levels48/110/220 V dc 1 A/0.25 A/0.15 AContact material AgCdO2

Control inputsTerminal numbers X1/1-2, 3-4, 5-6, 7-8, 9-10Control voltage- rated voltages Un = 24/48/60/110/220 V dc

Un = 110/220 V ac- operation range 18...265 V dc and 80...265 V acCurrent drain 2...20 mASelectable mode of activation in the relay modules- input activated when Energized- input activated when Non-energizedTime between activation of control input andrelay operation (control input active when energized,to be programmed in the relay module) <30 msTime between activation of control input andrelay operation (control input active when non-energized, to be programmed in the relay module) <50 ms

16

Power supply moduleTerminal numbers X2/1-2Type SPGU 240A1- rated voltages Un = 110/120/230/240 V ac

Un = 110/125/220 V dc- operation range 80...265 V ac/dcType SPGU 48B2- rated voltage Un = 24/48/60 V dc- operation range 18...80 V dcCurrent consumption under quiescent/operationconditions about 10 W/15 W

Stabilized three-phase differential relay module SPCD 3D53- see "Technical data" of the manual 1MRS 750097-MUM EN.

Earth-fault relay module SPCD 2D55- see "Technical data" of the manual 1MRS 750098-MUM EN.

Combined overcurrent and earth-fault relay module SPCJ 4D28- see "Technical data" of the manual 1MRS 750093-MUM EN.

Data communicationsTransmission mode Fibre-optic serial busCoding ASCIIData transfer rate 4800 or 9600 BdOptical bus connection module- for plastic core cables SPA-ZC 21 BB- for glass fibre cables SPA-ZC 21 MMOptical bus connection module power from aninternal power source- for plastic core cables SPA-ZC 17 BB- for glass fibre cables SPA-ZC 17 MM

Software support for SPAD 346 CSubstation monitoring program SMS 010Disturbance recorder PC program DR-COM

Test voltagesDielectric test voltage (IEC 255-5) 2.0 kV, 50 Hz, 1 minImpulse test voltage (IEC 255-5) 5 kV, 1.2/50 µs, 0.5 JInsulation resistance (IEC 255-5) >100 MΩ, 500 V dc

17

Disturbance testsHigh-frequency disturbance test (IEC 255-22-1)- common mode 2.5 kV, 1 MHz, 2 s- differential mode 1.0 kV, 1 MHz, 2 sElectrostatic discharge test (IEC 255-22-2 andIEC 801-2), class III:- air discharge 8 kV- contact discharge 6 kVFast (5/50 ns) transients (IEC 255-22-4), class III;IEC 801-4, level IV:- power supply inputs 4 kV- other inputs/outputs 2 kV

Environmental conditionsService temperature range -10...+55°CTransport and storage temperature range(IEC 68-2-8) -40...+70°CTemperature influence 0.1%/°CRelative humidity (IEC 68-2-30) 93...95%, +55°, 6 cyclesDegree of protection by enclosure of flush-mountedrelay case (IEC 529) IP 54Weight of fully equipped relay about 6 kg

18

Recommenda-tions for currenttransformers

The more important the object to be protected,the more attention should be paid to the currenttransformers. Normally, it is not possible todimension the current transformers so that theyrepeat currents with high DC components with-out saturating, when the residual flux of thecurrent transformer is high. The differentialrelay SPAD 346 C operates reliably, even though

the current transformers are partially saturated.The purpose of the following current trans-former recommendations is to secure the stabil-ity of the relay at high through-currents, andquick and sensitive operation of the relay atfaults occurring in the protected area, where thefault currents may be high.

The accuracy class recommended for currenttransformers (IEC 185) to be used with thedifferential relay SPAD 346 C is 5P, in whichthe limit of the current error at rated primarycurrent is 1% and the limit of the phase displace-ment is 60 minutes. The limit of the compositeerror at rated accuracy limit primary current is5%.

The approximate value of the accuracy limitfactor Fa corresponding to the actual CT burdencan be calculated on the basis of the ratedaccuracy limit factor Fn (ALF) at the ratedburden, the rated burden Sn, the internal bur-den Sin and the actual burden Sa of the currenttransformer as follows:

Fa = Fn x

In the example the rated burden Sn of the LVside CTs 5P20 is 10 VA, the secondary ratedcurrent 5 A, the internal resistance Rin = 0.07 Ωand the accuracy limit factor Fn (ALF) corre-sponding to the rated burden is 20 (5P20). Thusthe internal burden of the current transformer isSin = (5 A)2 x 0.07 Ω = 1.75 VA. The inputimpedance of the relay at a rated current of 5 Ais <20 mΩ. If the measurement conductors havea resistance of 0.113 Ω the actual burden of thecurrent transformer is Sa =(5 A)2 x (0.113 +0.020) Ω = 3.33 VA. Thus the accuracy limitfactor Fa corresponding to the actual burdenwill be about 46.

The CT burden may grow considerably at ratedcurrent of 5 A. At 1 A rated current the actualburden of the current transformer decreases, atthe same time as repeatability improves.

At faults occurring in the protected area on theHV side of the transformer, the fault currentsmay be very high compared to the rated currentsof the current transformers. Thanks to the in-stantaneous stage of the differential relay mod-

ule it is enough that the current transformers arecapable of repeating, during the first cycle, thecurrent required for instantaneous tripping.

Thus the current transformers should be able toreproduce the asymmetric fault current withoutsaturating within the next 10 ms after the occur-rence of the fault, to secure that the operatetimes of the relay comply with the times statedin the manuals of the modules

The accuracy limit factors corresponding to theactual burden of phase current transformer to beused in differential protection shall fulfil thefollowing requirements:

Fa > 40 andFa > 4 x Imax1

The setting Id/In>> of the instantaneous differ-ential current stage is used as the factor Imax1.

The use of auto-reclosing to clarify a fault occur-ring outside the protected area may produce asubstantial residual flux in the CT core. Toguarantee that the differential protection re-mains stable in an auto-reclose situation also atlarge currents when the residual flux is great, theaccuracy limit factors corresponding to the ac-tual burden of the HV and LV side CTs shouldfulfill the requirements mentioned above and beof the same order, if possible.

In generator protection it is important that therepeatability of the phase current transformerson the neutral side and on the network side ofthe generator correspond, that means that theburdens of the current transformers on bothsides are as equal as possible. Should, in connec-tion situations following synchronization, highinrush or start currents containing high DCcomponents pass through the protected genera-tor, special attention should be paid to theperformance and the burdens of the currenttransformers and to the settings of the relay.

Differentialprotection

Sin + SnSin + Sa

19

The sensitivity and reliability of differentialcurrent protection stabilized through a resistorare strongly related to the current transformersused. The number of turns of the current trans-formers that are part of the same differentialcurrent circuit should be the same. The currenttransformers should have the same transforma-tion ratio.

To be able to feed the differential current circuitwith the current required for starting, when afault occurs in the protected area, the currenttransformers need a knee-point voltage that isabout twice the stabilizing voltage required fromthe relay at faults outside the protected area. Thestabilizing voltage Us of the relay and the knee-point voltage Uk of the current transformer iscalculated as follows:

Us =

Uk = 2 x Us

where Ifmax is the maximum through-goingfault current at which the protection is notallowed to operate. The factor two is used whenno operation delay whatsoever is permitted forthe protection. To prevent the knee-point volt-age of the current transformers to grow too high,it is recommended to use current transformerswhose secondary winding resistance is of thesame level as the resistance of the measurementcircuit.

The technical features of class X (BS 3938)current transformers are determined by the knee-point voltage and the resistance of the secondarywinding. The knee-point voltage is the value ofthe CT secondary voltage at which a further10% increase in the secondary voltage wouldcause a 50% increase in the excitation current.The knee-point voltages Uk of current trans-formers used in differential protection shouldfulfil the following requirement:

Uk>

wheren is the transformation ratio of the current

transformerRin is the secondary resistance of the current

transformerRL is the total resistance of the longest loop

measured (outgoing and return lead)Imax2 is the setting of the instantaneous differ-

ential current stage Id/In>> multiplied bythe rated current of the protected object.

4 x Imax2 x (Rin + RL) n

The recommendations for current transformersused in earth-fault protection based on thestabilized differential current principle are thesame as for differential protection. The accuracylimit factor corresponding to the actual burden

of the neutral current transformer should be asclose as possible to the accuracy limit factorcorresponding to the actual burden of the phasecurrent transformers.

Earth-faultprotection

The sensitivity requirements for the protectionare jeopardized if the magnetizing current of thecurrent transformers is allowed to rise too muchcompared to the knee-point voltage. The Iprimvalue of the primary current at which the relayoperates at certain settings can be calculated asfollows:

Iprim = n x (Ir + Iu + m x Im)

wheren = the transformation ratio of the current

transformerIr = the current value representing the relay

settingIu = is the current flowing through the protec-

tion varistorm = the number of current transformers in-

cluded in the protectionIm = the magnetizing current of one current

transformer

A protection varistor connected in parallel withthe differential current prevents the voltage gen-erated in the differential circuit at faults occur-ring in the protected area from rising too high.The resistance of the varistor depends on thevoltage applied to it: the higher the voltage thesmaller the resistance.

Earth-fault protectionbased on the high-impedance typeprotection

Ifmax x (Rin + RL) n

The recommendations for current transformersused in overcurrent protection are the same as

those used in differential current protection, i.e.there are no special requirements.

Overcurrentprotection

20

Circuit-breakercontrol

The opening of the circuit-breaker can be im-plemented as double-pole control or single-polecontrol. The stabilized differential relay SPAD346 C is provided with two heavy-duty one-polerelays (TS1 and TS2) and two heavy-duty dou-ble-pole relays (TS3 and TS4).

When double-pole circuit-breaker control isused, the control voltage is linked to both sidesof the tripping coils of the transformer. If theheavy-duty output relay TS3 is used for double-pole control, for example, terminal X1/15 isconnected to negative control voltage and ter-minal X1/18 is connected to positive controlvoltage. The terminals X1/16 and X1/17 areconnected to the open coil of the circuit breaker.If the heavy-duty output relay TS4 is used for

two-pole control, the terminal X1/11 can beconnected to negative control voltage and ter-minal X1/14 can be connected to positive con-trol voltage. Terminals X1/12 and X1/13 areconnected to the open coil of the circuit breaker.

If the output relay TS3 is used for single-polecontrol, the terminals X1/16 and X1/17 shouldbe connected together, that is, the relays shouldbe connected in series. Terminal X1/15 isconnected to the open coil of the circuit breakerand terminal X1/18 to the positive controlvoltage. Should output relay TS4 be used forsingle-pole control, terminals X1/12 and X1/13should be connected together. Terminal X1/11is connected to the open coil and terminal X1/14 to the positive control voltage.

+ + +

+

0

SS1 SS2 SS3 SS4 TS1 TS2 TS3

++++

14 15 11 12 13 9 10 7 8 5 6 3 4 15 16 17 18X1X2X2X2X2X2X2

OPEN

+

TS4

11 12 13 14X1

-

Double-pole circuit-breaker control

+ + +

+

0 -

SS1 SS2 SS3 SS4 TS1 TS2 TS3

++++

14 15 11 12 13 9 10 7 8 5 6 3 4 15 16 17 18X1X2X2X2X2X2X2

OPEN

+

TS4

11 12 13 14X1

Single-pole circuit-breaker control

Fig. 6. Double-pole and single-pole circuit-breaker control

21

Applicationexamples

The following application examples show thedifferential relay SPAD 346 C used for theprotection of power transformers.

All the three relay modules have been used insolutions presented.

Differential relay SPAD 346 C used for the protection of a YNyn0-connected power transformer.

X1/18

L1

L2

L3

P1P2

S1S2 S2S1

P2P1

U1 IRF

+ -

U5

+

-

(~)

(~)Uaux

U6

BS1BS2BS3BS4BS5

S1

S2

P1

P2

S1

S2

P1

P2

SS1SS2SS3SS4TS1TS2TS3TS4

SPAD 346 C

SS2

SS1

SS3

SS4

TS1

TS2

TS3

IRF

TS4

I / O

∆I >01

BS1

BS2

BS3

BS4

BS5

X1/1

X1/2

X1/3

X1/4

X1/5

X1/6

X1/7

X1/8

X1/9

X1/10

IRFX2/18X2/17X2/16

X2/14X2/15

X2/10X2/9

X2/13

X2/11X2/12

X2/8X2/7

X2/5X2/6

X2/3X2/4

+

+

+

+

+

+

+

+X1/14X1/13X1/12X1/11

TRIP

+

TRIP

TRIP

3∆I>

U4

X2/

1

X2/

2

X0/

1

X0/

2X

0/3

X0/

4

X0/

5X

0/6

X0/

7

X0/

8X

0/9

X0/

13X

0/14

X0/

15X

0/16

X0/

17X

0/18

X0/

19X

0/20

X0/

21

5 AN

X0/

25X

0/26

X0/

27

X0/

37

X0/

38X

0/39

I / O

Y / ∆

Y / ∆

U2 IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

U3

BS1BS2BS3BS4BS5

BS2BS1

1 A

5 AN

1 A

5 AN 1 A

5 AN

1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

3∆I>>

∆I >02

≅

SP

A-Z

C_

Rx Tx

X1/17X1/16X1/15

TRIP

SERIALPORT

3I>I

∆I>BS3

IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

Fig. 7. Application of example 1.

Example 1.

22

The stabilized stage and the instantaneous stageof the three-phase differential relay moduleSPCD 3D53 are used to protect the powertransformer against winding short circuit andinterturn faults. In an inrush situation the trip-ping of the stabilized stage is inhibited by ablocking function based on the second har-monic of the differential current. In cases wherethe transformer is not allowed to be discon-nected from the network in a situation of over-excitation, a blocking arrangement based on thefifth harmonic of the differential current is used.

The stabilized differential current principle orthe high-impedance principle of the relay mod-ule SPCD 2D55 is employed for protecting theHV and LV side winding against earth fault.When the stabilized differential current princi-ple is used, the inverse time stage I0> of the relaymodule SPCJ 4D28 can be used as back-upprotection on the LV side. The blocking basedon the ratio between the second harmonic andthe fundamental frequency component of theneutral current is permitted both on the HVside and on the LV side. If the high-impedanceprinciple is used on the LV side, no back-upprotection can be arranged for the earth-faultprotection.

The relay module SPCJ 4D28 provides three-phase, three-stage overcurrent protection andearth-fault back-up protection. The modulemeasures the phase currents on the HV side andneutral current on the LV side. The definitetime overcurrent stage I>>> is set to operate onshort circuits occurring on the HV side of thetransformer. The overcurrent stage I>> isconfigured to operate on short circuits in the

poles of the LV side and serves as back-up atshort circuits in the LV side busbar system. Afacility of automatic doubling of the settingvalue of the I>> stage at magnetizing inrushcurrents is available. The overcurrent stage I> ofthe module can be employed as inverse timeearth-fault back-up protection for the LV sidefeeders.

Blocking based on the second harmonic of thedifferential current of the relay module SPCD3D53 can be used for blocking the overcurrentstages I> and I>> of the relay module SPCJ4D28 at transformer magnetizing inrush cur-rents. The blocking is programmed in the relaymodule SPCD 3D53 for the desired outputrelay, from which it is linked to the externalcontrol input BS1, BS2 or BS3. The concernedcontrol input is programmed to block the opera-tion of the overcurrent stage I> and/or I>> of therelay module SPCJ 4D28. The operation of theovercurrent stage I>>> will not be blocked.

In combination with protection of YNyn-con-nected power transformers the phase disconti-nuity protection ∆I> of the relay module SPCJ4D28 can be used for network supervision, atleast as alarming protection. Then it should benoticed that the phase discontinuity protectioncan provide an alarm signal at earth fault as well.

The operate signals of the integrated circuit-breaker failure protection of the relay modulesare linked to a heavy-duty output relay that iscapable of operating the circuit breaker preced-ing the HV side circuit breaker in the supplydirection.

Differential relay SPAD 346 C used for the protection of a YNd11-connected power transformer.

The principle of the winding and the interturnfault protection and the overcurrent protectionis the same as in example 1. The high-imped-ance protection principle of the module SPCD2D55 is used for protecting the HV side windingsagainst earth fault.

The stage I0>, operating with inverse time char-acteristic, of the relay module SPCJ 4D28 servesas back-up for the earth-fault protection. Thenthe neutral current from the second neutralconnection transformer on the HV side is con-nected to the terminals XO/37-38 or X0/37-39,as illustrated in the figure. When the HV sidestar point is directly earthed the definite timestage I0>> can also be used as earth-fault back-up protection.

The neutral current principle is programmed tobe used on the LV side in the relay moduleSPCD 2D55. Then the blocking function basedon the second harmonic of the neutral currentcan be used. The blocking function can be usedfor blocking the stages I0> and I0>> of the relaymodule SPCJ 4D28 in transformer inrush situ-ations. In the relay module SPCD 2D55 theblocking is programmed to the desired outputrelay, from which it is externally linked to thecontrol input BS1, BS2 or BS3. The concernedcontrol input is programmed to block the opera-tion of the desired earth-fault stage of the mod-ule SPCJ 4D28.

Example 2.

23

X1/18

U1 IRF

+ -

U5

+

-

(~)

(~)Uaux

U6

BS1BS2BS3BS4BS5

SS1SS2SS3SS4TS1TS2TS3TS4

SPAD 346 C

SS2

SS1

SS3

SS4

TS1

TS2

TS3

IRF

TS4

I / O

∆I >01

BS1

BS2

BS3

BS4

BS5

X1/1

X1/2

X1/3

X1/4

X1/5

X1/6

X1/7

X1/8

X1/9

X1/10

IRFX2/18X2/17X2/16

X2/14X2/15

X2/10X2/9

X2/13

X2/11X2/12

X2/8X2/7

X2/5X2/6

X2/3X2/4

+

+

+

+

+

+

+

+X1/14X1/13X1/12X1/11

TRIP

+

TRIP

TRIP

3∆I>

U4

X2/

1

X2/

2

X0/

1X

0/2

X0/

3X

0/4

X0/

5X

0/6

X0/

7

X0/

8X

0/9

X0/

13X

0/14

X0/

15X

0/16

X0/

17X

0/18

X0/

19X

0/20

X0/

21

5 AN

X0/

25X

0/26

X0/

27

X0/

37

X0/

38X

0/39

I / O

Y / ∆

Y / ∆

U2 IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

U3

BS1BS2BS3BS4BS5

BS2BS1

1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

5 AN 1 A

3∆I>>

∆I >02

≅

SP

A-Z

C_

Rx Tx

X1/17X1/16X1/15

TRIP

SERIALPORT

3I>I

∆I>BS3

IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

L1

L2

L3

P1P2

S1S2

S1

S2

P1

P2

S1

S2

P1

P2

P1P2

S1S2

YNd11

Fig. 8. Application of example 2

24

Example 3. Differential relay SPAD 346 C used for the protection of a YNd11-connected power transformerand a zigzag-connected earthing transformer.

The winding and interturn fault protection andthe overcurrent protection are arranged in thesame manner as in example 1. The high-imped-ance principle or the stabilized differential cur-

rent principle can be used for the earth-faultprotection. The figure below shows the connec-tion when the high-impedance principle is used.

X1/18

U1 IRF

+ -

U5

+

-

(~)

(~)Uaux

U6

BS1BS2BS3BS4BS5

SS1SS2SS3SS4TS1TS2TS3TS4

SPAD 346 C

SS2

SS1

SS3

SS4

TS1

TS2

TS3

IRF

TS4

I / O

∆I >01

BS1

BS2

BS3

BS4

BS5

X1/1

X1/2

X1/3

X1/4

X1/5

X1/6

X1/7

X1/8

X1/9

X1/10

IRFX2/18X2/17X2/16

X2/14X2/15

X2/10X2/9

X2/13

X2/11X2/12

X2/8X2/7

X2/5X2/6

X2/3X2/4

+

+

+

+

+

+

+

+X1/14X1/13X1/12X1/11

TRIP

+

TRIP

TRIP

3∆I>

U4

X2/

1

X2/

2

X0/

1X

0/2

X0/

3X

0/4

X0/

5X

0/6

X0/

7X

0/8

X0/

9

X0/

13X

0/14

X0/

15X

0/16

X0/

17X

0/18

X0/

19X

0/20

X0/

21

5 AN

X0/

25

X0/

26X

0/27

X0/

37

X0/

38X

0/39

I / O

Y / ∆

Y / ∆

U2 IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

U3

BS1BS2BS3BS4BS5

BS2BS1

1 A

5 AN 1 A

5 AN

1 A

5 AN 1 A

5 AN 1 A

5 AN

1 A

5 AN 1 A

5 AN 1 A

3∆I>>

∆I >02

≅

SPA

-ZC

_

Rx Tx

X1/17X1/16X1/15

TRIP

SERIALPORT

3I>I

∆I>BS3

IRFSS1SS2SS3SS4TS1TS2TS3TS4I / O

L1

L2

L3

P1P2

S1S2

S1

S2

P1

P2

S1

S2

P1

P2

YNd11

S2S1

P2P1

Fig. 9. Application of example 3.

25

Settinginstructions

Three-phasedifferentialrelay moduleSPCD 3D53

A table in the manual of the differential relaymodule presents the vector group matchingsettings corresponding to the most general powertransformer vector groups. The vector groupmatching shown in the table is programmedinto the relay module via the switches of switch-group SGF1. To be able to use the table youmust know the vector group of the power trans-former to be protected and the connection typeof the current transformers, which also has to beconsidered in the protection of generators.

In the application example 1 (Fig. 7) the phasecurrent transformers are connected according toconnection type I, in which case the phasedifference of HV and LV side phase currentsapplied to the relay is 180°. The phase differenceis matched in the differential relay module onthe LV side (SGF1/3=1, SGF 1/4=1 and SGF1/5...8=0). The star points of the transformer HVside and LV side windings are earthed, so thezero-sequence component occurring in earthfaults outside the protection area is set to beeliminated from the HV and LV side phasecurrents (SGF1/1=1, SGF 1/2=1). The check-sum of swichgroup SGF1 will be 15.

In the application example 2 (Fig. 8) the con-nection of the current transformers is in accord-ance with connection type II, so the connectionof the current transformers does not cause phasedifference between the currents linked to therelay. On the HV side the zero-sequence com-ponent of the phase currents is eliminated in thematching of the phase difference in the numeri-cally implemented delta connection (SGF1/6=1,SGF1/7=0 and SGF1/8=1). The checksum ofswitchgroup SGF1 will be 160.

Should the required vector group matching notappear from the table, the vector group match-ing is set by means of the additional tables. Allthe vector groups of two-winding transformerscan be matched in the relay module irrespectiveof the earthing method of the transformer andthe network.

The setting of the vector group matching shownin the application example 3 (Fig. 9) takes intoaccount not only the vector group of the maintransformer but also the earthing transformer inthe protected area on the LV side. The connec-tion of the phase current transformers is inaccordance with connection type I. In the pro-tected area there is an earthed neutral point bothon the HV side and on the LV side and thus thezero-sequence component of the phase currentshas to be considered in the vector group match-ing. On the HV side the zero-sequence compo-nent is eliminated in the phase difference match-ing (SGF1/6=0, SGF1/7=1 and SGF1/8=0).

On the LV side the zero-sequence componenthas to be set to be calculated and eliminatedfrom the phase currents separately (SGF1/1=1).The checksum of switchgroup SGF1 will be 65.

If the rated primary current of the HV and LVside current transformers is not equal to therated current of the power transformer on theconcerned side, the settings I1/In and I2/In areused for correcting the transformation ratios. Inthe example the rated power of the power trans-former is 40 MVA and the rated voltage is 110 kV/10.5 kV. The transformation ratio of the HVside current transformers is 300 A/1 A and thatof the LV side current transformers is 2500 A/5A.

The rated HV side current I1n of the powertransformer is

I1n = = = 210 A

Correspondingly, the rated LV side current I2nis

I2n = = = 2199 A

The settings for the transformation ratio correc-tion are calculated on the basis of these ratedcurrents and the rated primary currents of theHV and LV side current transformers:

I1/In = 210 A / 300 A = 0.70 andI2/In = 2199 A / 2500 A = 0.88

The basic setting P/In is used to set the maxi-mum sensitivity of the differential relay. Thissetting takes into account the differential cur-rents caused by a no-load situation and a smalloverexcitation of the transformer. The basicsetting can also be used to influence the level ofthe whole operation characteristic. The basicsetting P/In for transformer protection is typi-cally 20...40%. In generator protection the ba-sic setting is typically 5...20%.

When setting the starting ratio S the accuracyclass of the current transformers to be used, theaccuracy limit factors corresponding to the ac-tual burden of the current transformers, theregulation range of the tap changer of the powertransformer and the location of the second turn-ing point I2tp/In of the operation characteristichave to be considered. The bigger the errors ofthe current transformers used, the greater thevalue of S. Should, for instance, the accuracyclass of the HV and LV side current transform-ers be 5P, the composite error at rated accuracylimit primary current would be maximum 5%on both sides.

40 MVA√

–3 x 10.5 kV

Sn√

–3 U2n

Sn√

–3 U1n

40 MVA√

–3 x 110 kV

26

The transformation ratios of the current trans-formers on the HV and LV side of the powertransformer are normally matched to corre-spond to the middle position of the tap changer.The maximum error will be caused by the tapchanger position, when the tap changer is in theextreme position. One setting factor for thestarting ratio is the regulation range of the tapchanger, which may be for example ±9 x 1.67%= 15%. Another factor to be considered in thestarting ratio setting is the error caused by thematching transformers of the relay and theinaccuracy of the A/D converters. This error isabout 2% at a maximum.

The starting ratio is set by means of abovesetting factors. In the case of the example theappropriate setting of the starting ratio is 25...35%. Should the accuracy limit factors corre-sponding to the actual burden of the currenttransformers to be used on the HV side and LVside clearly deviate from each other, the startingratio S must be given a greater value than in thecase where the concerned accuracy limit factorsare nearly the same.

The setting I2tp/In of the second turning pointof the operation characteristic influences on thetripping sensitivity at values above the ratedcurrent. If the short circuit power is mainly fedfrom one direction at a fault occurring in theprotected area, the appropriate setting of I2tp/Inis 2.0...2.5. Should the short-circuit power befed both from the HV side and the LV side whena fault accurs in the protected area, the secondturning point can be given a smaller value with-out the sensitivity being reduced. In the protec-tion of the block transformer of the generatorthe short circuit power is normally fed from twodirections and then, when a fault occurs in theprotection area, the phase difference of thecurrents increases and the stabilizing currentdecreases. In the case of the block transformerthe recommended setting of I2tp/In is 1.5...2.0.

The instantaneous tripping limit Id/In>> is setso that the differential relay module does nottrip when the transformer is energized. Theinstantaneous stage trips, when the fundamen-tal frequency component of the differential cur-rent exceeds the set tripping limit Id/In>> orwhen the instantaneous value of the differentialcurrent exceeds the limit 2.5 x Id/In>>. Whenthe differential current is below 2.5 x Id/In>> theDC component and the harmonics of the cur-rent do not affect the operation of the relay.Normally, the peak value of the asymmetricinrush current of the power transformer is con-siderably greater than the peak value of thesymmetric inrush. At asymmetric inrush cur-

rent the DC component is great. The amplitudeof the fundamental frequency component istypically only half of the peak value of the inrushcurrent. Thus the instantaneous tripping valueId/In>> of the relay can be set below the peakvalue of the asymmetric inrush. In power trans-former protection the setting value of the in-stantaneous differential current stage is typically6...10. In generator protection the appropriatesetting value for instantaneous tripping is 5...8.

Blocking of the stabilized stage based on theratio between the second harmonic and thefundamental frequency component of the dif-ferential current is enabled when the switchSGF2/1 = 1. In power transformer protectionthe blocking should always be enabled. Theappropriate setting of the blocking ratio Id2f/Id1f> in power transformer protection is usually15%. When SGF2/2 = 1, the operate time of therelay is not getting longer in a situation when thetransformer is connected against a fault in theprotected area.

Blocking based on the second harmonic of thedifferential current should be allowed in thedifferential relay of a generator in such situa-tions where a relatively large block transformeror power transformer is energized through thegenerator after synchronization. The inrushcurrent passing through the generator may satu-rate the current transformers, thus causing dif-ferential current that typically contains a highamount of second harmonic. In this situationthe main and second settings of the relay can beused. In a connection situation the actual set-tings of the differential relay module are re-placed by the second settings, in which theblocking is enabled. After damping of theinrush current the main settings, which do notallow the blocking function, are used.

When setting the blocking of the fifth harmonicit has to be specified whether blocking is to beallowed at all (SGF2/3=0 and SGF2/4=0),whether only the blocking ratio Id5f/Id1f>(SGF2/3=1 and SGF2/4=0) is to be set for thedifferential relay module or whether both theblocking ratio Id5f/Id1f> and the deblockingratio Id5f/Id1f>> (SGF2/3=1 and SGF2/4=1) areto be set. In the last case mentioned the opera-tion of the stabilized stage will be blocked, if theratio between the fifth harmonic and the funda-mental frequency component of the differentialcurrent is between the setting values Id5f/Id1f>and Id5f/Id1f>>. Should only the blocking facil-ity be used the blocking ratio is set high enoughto prevent the module from blocking its opera-tion at high overvoltages, which might causedamage to the transformer.

27

Earth-faultrelay moduleSPCD 2D55

The type of earth-fault protection to be usedon the HV and LV side of the transformer isselected with the configuration switches SGF1/1...8. The switch positions corresponding to thedifferent protection principles are presented inthe manual of the module.

The basic settings P1/In and P2/In are used forselecting the start value of the earth-fault protec-tion. When the numerical stabilized differentialcurrent principle is used the basic setting influ-ences the level of the whole operation character-istic.

When the stabilized differential current princi-ple is used the setting of the operate time t01> ort02> should be longer than the DC time con-stant of the network. The smaller the basicsetting, the longer the operate time setting shouldbe. If the high-impedance type protection isused, the operate time of the earth-fault relaymodule should be set at the minimum value, i.e.0.03 s.

When the protection principle is based on theresidual current of the phase currents the oper-ate time has to be long enough (up to severalseconds) to prevent unwanted tripping due tothe very asymmetric inrush or start-up currentpassing through the protected object.

The connection of the phase CTs and neutralconnection CT can cause a 180° phase displace-ment between the residual current of the phasecurrents and the neutral current at external earthfaults (see Fig. 6 in the manual of the moduleSPCD 2D55). When the stabilized differential

current principle is used the phase difference hasto be matched in the relay module (switchesSGF2/1 and SGF2/2).

When the differential current principle is usedthe transformation ratio corrections I01/In, I02/In,I1/In and I2/In are set in the same way as thetransformation ratio correction of the differen-tial relay module. The settings can also be usedfor scaling the start values when other protec-tion principles are used.

The settings I01/∑I1 and I02/∑I2 are deter-mined on the basis of the zero-sequence imped-ances of the transformer and the supplyingnetwork. If the star point of the transformer isdirectly earthed, the earth-fault current and theratio between the neutral current and the re-sidual current of the phase currents are typicallygreater than in a situation where the concernedstar point is earthed through a resistor or achoke. When the star point of the power trans-former is directly earthed the recommendedsetting is 5...15%. The position of the earthfault in the winding and also the number andposition of the other star points of the network,too, affect the distribution of the earth-faultcurrent.

Blocking based on the ratio between the secondharmonic and the fundamental frequency com-ponent of the neutral current should be used incombination with the stabilized differential cur-rent principle and the neutral current principle.The blocking is enabled by the switch settingsSGF2/3=1 and SGF2/4=1. The blocking limitsare typically 20...30%.

Combined over-current and earth-fault relay moduleSPCJ 4D28

The settings of the combined overcurrent andearth-fault relay module are dependent on theobject to be protected and the use of the protec-tion stages. The low-set stages (I> and I0>) canhave a definite time or an inverse time operationcharacteristic. Four international standardizedtime/current characteristics and two special-type time/current characteristics are availablefor the inverse time operation (IDMT). Theswitch SGF1 is used for selecting the operationmode and the time/current characteristic. Theoperation of the high-set stages I>>, I>>> andI0>> is based on the definite time characteristiconly. The operation of the individual stages canbe blocked by means of the concerned configu-ration switches.

In transformer protection the setting of theovercurrent stages should be at least 1.5 x In, tobe able to utilize the overload capacity of thetransformer. The setting value of the high-setstage I>> can be set to automatically doublewhen the transformer is energized. The opera-tion of the overcurrent stages I> and I>> and theearth-fault stages I0> and I0>> can be blocked bythe control signals BS1, BS2 and BS3. Theswitches SGB1/1...4, SGB2/1...4 and SGB3/1...4are used for configuring the blocking signals.

When required, the blocking signal BS1 can beused to block the operation of the phase discon-tinuity protection ∆I> of the relay module SPCJ4D28. The switch SGB1/6 is used for confi-guring the blocking. The phase discontinuityprotection supervision can be set out of opera-tion (SGF3/1).

28

Commissioning The differential relay module SPCD 3D53 iscapable of reliably measuring the amplitudes ofthe phase currents and the differential currents,the phase angles between the phase currents andthe phase differences of the HV and LV sidephase currents when the current supplied to therelay is above 1% of the rated current. Even atlower currents it is possible to measure the phasedifferences. The amplitudes and phase anglesmeasured are presented on the display of themodule. The amplitudes are expressed as rela-tive values (x In and % In). The values displayedtake into account the vector group matchingand the transformation ratio correction set forthe relay.

After mounting the following low-voltage testcan be made on the relay to verify the connec-tion, phase sequence, vector group matchingand transformation ratio correction of the dif-ferential relay: Connect three-phase low-voltageto the primary poles of the current transformerson the HV side of the power transformer so that

the HV side current transformers are includedin the circuit. By making a three-phase short-circuit on the LV side of the transformer so thatthe LV side current transformers are included inthe circuit a three-phase current of some mAs isinjected into the relay.

During the test the HV and LV side currentamplitudes and phase angles measured by therelay module are shown for the individual phaseson the display of the differential relay module(or over the serial bus). If the connection, vectorgroup matching and the transformation ratiocorrections of the relay are correct the followingapplies to each phase:

- the phase currents are equally high- the differential currents are 0%- the phase differences of the HV and LV side

phase currents are 0°- the phase differences between the phase cur-

rents on the same side are 120°.

The relay should be subject to regular tests inaccordance with national regulations and in-structions. The manufacturer recommends aninterval of five years between the tests.

The test is recommended to be carried out as asecondary test. Then the relay has to be discon-nected during the test procedure. However, it isrecommended to check the condition of thesignal and trip circuits as well.

WARNING!Do not open the secondary circuits of the cur-rent transformers when disconnecting and test-ing the relay, because the high voltage producedmay be lethal and could damage insulation.

The test should be carried out using the normalsetting values of the relay and the energizinginputs used. When required, the test can beextended to include more setting values.

As the settings of the relay modules vary indifferent applications, these instructions presentthe test procedure in general. Ordinary currentsupply units and instruments for measuringcurrent and time can be used for the tests.

During the test procedure the relay recordscurrents and relay operations. The registersshould be read before the test is started andduring the test.

The relay settings may have to be changedduring testing. A PC program is recommendedto be used to read the relay settings beforestarting the test, to make sure that the originalsettings are being restored when the test hasbeen completed.

Testing

29

HV side vector group Separate zero-sequence Current displayed by thematching elimination relay module

Yy No x

Yy Yes x x

Yd No x x

Testing of differen-tial relay moduleSPCD 3D53

The following values and functions of the stabi-lized differential current stage 3∆I> and theinstantaneous differential current stage 3∆I>>should be tested:

- operate value (to be measured on all threephases)

- operate time (to be measured on one phase atleast)

- operation indication and operation of outputrelays

Note!When testing the three-phase differential relaymodule the effect of the vector group matching,elimination of the zero-sequence componentand transformation ratio corrections on theoperation of the stabilized differential currentstage and the instantaneous differential currentstage have to be taken into account.

If Yd vector group matching has been selectedfor the HV or LV side, the current measured bythe relay module for the concerned side will,after matching of the vector group, be 1/√

–3 of

the current applied to the relay at single-phasetesting.

Example 1. Vector group matching of a YNd11-connected power transformer on the HV side.CT connection according type II.

-IL1m =

-IL2m =

-IL3m =

At single-phase testing the HV side currentsinjected are IL1 = 1 A, IL2 = 0 A and IL3 = 0 A.After vector group matching the amplitudes ofthe currents are IL1m = 0.58 A, IL2m = 0 A andIL3m = 0.58 A.

If the zero-sequence component has been se-lected to be numerically reduced from the phasecurrents on the HV side or the LV side, i.e.SGF1/1 = 1 or SGF1/2 = 1, the current meas-ured by the relay module on that side will be2/3 of the current applied to the relay at single-phase testing.

Example 2. On the HV side of the YNyn-con-nected transformer zero-sequence current is setto be eliminated as follows (SGF1/2 = 1):

-IL1m =

-IL1 – x (

-IL1 +

-IL2 +

-IL3)

-IL2m =

-IL2 – x (

-IL1 +

-IL2 +

-IL3)

-IL3m =

-IL3 – x (

-IL1 +

-IL2 +

-IL3)

At single-phase testing the HV side currentsinjected are IL1 = 1 A, IL2 = 0 A and IL3 = 0 A.After the zero-sequence current elimination thecurrents are IL1m = 0.67 A, IL2m = 0.33 A andIL3m = 0.33 A.

The table below shows how the HV side settingsof the relay module affect the values measured atsingle-phase testing. I is the one-phase current(A) applied to the relay, In is the rated current (1A or 5 A) of the matching transformer and I1/Inis the setting of the HV side transformation ratiocorrection (the corresponding HV side setting isI2/In).

-IL1 –

-IL2

√–3

-IL2 –

-IL3

√–3

-IL3 –

-IL1

√–3

13

13

13

I 1In I1/In

I 1 2In I1/In 3

I 1 1In I1/In √

–3

30

Instantaneous differ-ential current stage3∆I>>

The testing of the module should be started withthe differential current stage 3∆I>>. To preventoperation of the stabilized differential stage dur-ing the testing of the differential current stage itsoperate signal should be disconnected at theoutput relays, that is, the switches of switch-group SGR1 should be set in the position 0.Alternatively, the operation of the stage can beinhibited by applying an external blocking sig-nal to the stage.

The operation of the instantaneous differentialcurrent stage is not stabilized. The instantane-

ous stage can be tested by applying one or twocurrents to the relay. When two currents areused, it should be noted that the setting valuerequired for the operation of the instantaneousstage will be reduced by 50%, if the stabilizingcurrent (average of the HV and LV side cur-rents) calculated by the relay module falls below30% of the differential current ( the differencebetween the HV and LV side currents).

When the instantaneous differential currentstage has been tested the original settings shouldbe restored.

The stabilized differential current stage can betested by applying one or two currents to therelay. If one current is used the phase currentinputs of the HV and LV side are tested one byone until all of six inputs have been tested.

Two currents have to be used to verify theoperation characteristic of the stabilized differ-ential current stage of the module. At least onestabilizing current value has to be selected fromeach of the three parts of the operation charac-teristic. Apply the current to the HV side andthe LV side on one phase so that the currentscalculated by the relay module initially are thesame. First the differential current is zero, and

the stabilizing current is the average of thecurrents applied. Then increase the differentialcurrent by raising one current and decreasingthe other current so that the stabilizing currentremains constant. Increase the differential cur-rent until the module operates when the differ-ential current exceeds the value of the operationcharacteristic. Repeat the test on all three phases.The test can also be made by raising one currentand keeping the other at a constant value.

The table below shows the differential currentrequired for operation in the different parts ofthe operation characteristic.

Stabilized differentialcurrent stage 3∆I>

Part of operating Stabilizing current Ib/In Differential current Id/In required forcharacteristic operation

1 0...0.5 P/In

2 0.5...I2tp/In P/In + S x (Ib/In – 0.5)

3 > I2tp/In P/In + S x (I2tp/In – 0.5) + (Ib/In – I2tp/In)

Note! The effect of the transformation ratiocorrection, vector group matching and zero-sequence component elimination on the cur-rents to be applied to the relay should be consid-ered when using the table.

Special equipment is required for testing theblockings based on the ratio between the secondharmonic and the fundamental frequency com-ponent or the fifth harmonic and the funda-

mental frequency component of the differentialcurrent. The weighting factors, 4, 1 and 1, to beused between the different phases have to betaken into account when testing the secondharmonic blocking. During the testing of theblocking based on the second harmonic of thedifferential current the blocking inhibit algo-rithm based on the waveform of the differentialcurrent should be set out of use, that is, theswitch SGF2/2 is set to 0.

31

Operate times Apply current to the relay by closing the currentswitch so that the differential current is about 2times the differential current required for opera-tion. Then measure the operate time, i.e. thetime from closing the switch until the relayoperates. The operate times of the instantane-ous differential current stage and the stabilized

differential current stage plus the selected oper-ate time of the circuit breaker failure protectioncan be separately tested. The operate time of theinstantaneous differential current stage can betested at various differential current levels, say,1.5 x Id/In>> and 4 x Id/In>>.

Check that the operation indicators and theoutput relays (alarm and heavy-duty) operateproperly during the testing of the relay module.

Operation indicators,alarm and trip signals

Test the following values and functions of theprotection stages ∆I01 and ∆I02:

- start value- operate time- operation indication and operation of output

relays

Note!The earth-fault protection for the HV side andthe LV side is identical and, therefore, tested inthe same way. The test procedure depends onthe protection principle employed. The switchesSGF1/1...8 are used to select the protectionprinciple for the HV and LV side. The effect ofthe transformation ratio correction settings onthe currents calculated by the relay module haveto be considered when the module is tested.

Testing of the earth-fault relay moduleSPCD 2D55

Testing of thestabilizeddifferentialcurrent principle

The stabilized differential current principle istested by applying one or two currents to therelay. When one current is used, inject thecurrent into the neutral current input I01 or I02.The neutral current does not affect the stabiliz-ing current. Increase the current until the mod-ule starts. The start value of the module is thesame as the basic setting of the concerned side.

When testing the differential current principleusing two currents, inject one current into thephase current input and the other into theneutral current input of the same side. Then theresidual current calculated by the relay modulewill be the same as the current injected into thephase current input. At single-phase testing thestabilizing current calculated by the relay mod-ule (average of the amplitudes of the three phasecurrents) will be 1/3 of the phase current appliedto the relay. Repeat the test on each phasecurrent input.

The phase difference of the currents applied tothe relay should be considered in the test (see thefunctions of switches SGF2/1 and SGF2/2 inthe manual for the earth-fault relay module andthe specification of the sign of the cosϕ term).

The module starts, if the following conditionsare fulfilled at the same time:- the ratio of the neutral current and the residual

current of the phase currents is above thesetting I01/∑I1 on the HV side or the settingI02/∑I2 on the LV side

- the directional differential current exceeds thevalue of the operation characteristic

- the blocking based on the second harmonicand external blocking do not prevent starting

Note!When the setting I01/∑I1 or the setting I02/∑I2is greater than 0%, the minimum value of theneutral current required for tripping on thatside is 2% of the rated current.

The directional criterion cosϕ = 1, if the residualcurrent or the neutral current of that side is lessthan 4% of the rated current.

Verify the operation characteristic of the stabi-lized differential current principle by selecting apoint on either part of the characteristic. Keepthe stabilizing current at a constant value andincrease the differential current until the mod-ule starts.

Special equipment is required for testing theblockings based on the ratio of the secondharmonic and the fundamental frequency com-ponent of the neutral current.

32

Test the high-impedance principle by injectingcurrent into the neutral current input of the

relay. The start value of the module is equal tothe basic setting of the concerned side.

Test the residual overcurrent principle by in-jecting current into the phase current inputs oneby one. Increase the current until the module

starts. The start value of the module is equal tothe basic setting of the concerned side.

Test the neutral current principle by injectingcurrent into the neutral current input of theconcerned side. Raise the current until the mod-

ule starts. The start value of the module is equalto the basic setting of the concerned side.

Apply a current of 1.5...2 times the currentrequired for starting to the module by closingthe current switch. Measure the operate time,i.e. the time from closing the switch until the

relay module operates. The operate times mustbe within the specified tolerances. The operatetime of the circuit breaker failure protection is tobe separately tested.

Check that the operation indicators and theoutput relays operate properly during the test-ing of the relay module.

Testing of high-impedance principle

Testing of residualovercurrent principle

Testing of neutralcurrent principle

Operate times

Operation indicators,alarm and operatesignals

Testing of thecombined over-current and earth-fault relay moduleSPCJ 4D28

When the relay module SPCJ 4D28 is tested, itshould be noted that the module measures thetransformer HV side or the generator star pointside phase currents, i.e. the phase currents con-nected to the terminals X0/1...9, and the trans-former LV side neutral current, i.e. neutralcurrent connected to the terminals X0/37...39.

The tests should include the following valuesand functions of the protection stages (I>, I>>,I>>>, I0>, I0>>, ∆I>) used:

- start value (for the high-set stages to be meas-ured for all three phases)

- resetting value (when desired/required)- start time (for one phase)- operate time (for one phase)- resetting times (when desired/required)- operation indication, circuit breaker opening

and signalling

Start value:Check the start value by raising the current,starting from zero, until the relay starts. Thestart value should be within the permitted toler-ances.

To measure the resetting value, raise the currentenough to make the relay start. Then decreasethe current until the relay resets.

When multi-stage protection relays are tested,the operation of the low-set stages may disturbthe testing of the high-set stages. In conse-quence, the operation of the lower current levelstages, generally, has to be inhibited or delayedby changing their setting values, to enable test-ing of the high-set stages. In such a case it isrecommended to start the testing from the stagewith the highest current setting and then moveon to the lower current stages. Thus the originalsettings of the stages are restored during the test.

Apply a current of about 1.5...2 times the settingof the protection stage by closing the currentswitch. Measure the operate time, i.e. the timefrom closing the switch until the relay operates.The operate times should be within the permit-ted tolerances. When inverse times are meas-

ured the measurements can be made with sev-eral current values (for example 2 x and 10 x thesetting value).

The reset time is the time from opening thecurrent switch until the relay resets.

Start and operatetimes

Operation indicators,alarm and operatesignals

Check that the operation indicators and theoutput relays (signalling and tripping) operateproperly during the testing of the relay module.

33

Maintenanceand repairs

When the protection relay is used under theconditions specified in "Technical data", it re-quires practically no maintenance. The relayincludes no parts or components that are sensi-tive to physical or electrical wear under normaloperating conditions.

Should the temperature and humidity at the sitediffer from the values specified, or the atmos-phere contain chemically active gases or dust,the relay should be visually inspected during thesecondary testing of the relay. This visual in-spection should focus on:

- Signs of mechanical damage to relay case andterminals

- Collection of dust inside the relay case; to beremoved with compressed air

- Signs of corrosion on terminals, case or insidethe relay

If the relay malfunctions or the operating valuesdiffer from those specified, the relay should beoverhauled. Minor measures can be taken bythe customer but any major repair involving theelectronics has to be carried out by the manufac-turer. Please contact the manufacturer or hisnearest representative for further informationabout checking, overhaul and recalibration ofthe relay.

The protection relay contains circuits that aresensitive to electrostatic discharge. If you have towithdraw a relay module, ensure that you are atthe same potential as the module, for instance,by touching the case. Detached modules shouldalways be transported and stored in antistaticplastic bags.

Note!Static protective relays are measuring instru-ments and should be handled with care andprotected against moisture and mechanical stress,especially during transport.

Spare parts

Deliveryalternatives

Three-phase stabilized differential relay module SPCD 3D53Earth-fault relay module SPCD 2D55Combined overcurrent and earth-fault relay module SPCJ 4D28Power supply modules- U = 80...265 V ac/dc (operative range) SPGU 240A1- U = 18...80 V dc (operative range) SPGU 48B2I/O module SPTR 9B31Connection module SPTE 8B18Case (including connection module) SPTK 8B18Bus connection module SPA-ZC 17_

SPA-ZC 21_

Equipment Type designation

Basic version, including all modules SPAD 346 CVersion excluding the combined overcurrent andearth-fault relay module SPCJ 4D28 SPAD 346 C1Version excluding earth-fault relay module SPCD 2D55 SPAD 346 C2Version including the stabilized differentialrelay module SPCD 3D53 only SPAD 346 C3

34

Orderingnumbers

SPAD 346 C without test adapter RS 621 002-AARS 621 002-CARS 621 002-DARS 621 002-FA

SPAD 346 C provided with test adapter RTXP 18: RS 621 202-AARS 621 202-CARS 621 202-DARS 621 202-FA

The letter combinations of the order number denote the rated frequency fn andauxiliary voltage Uaux of the protection relay:

Designation Rated frequency fn Operative range ofpower module of the relay

AA 50 Hz 80...265 V ac/dcCA 50 Hz 18...80 V dcDA 60 Hz 80...265 V ac/dcFA 60 Hz 18...80 V dc

Example1. Quantity and type designation 2 relays SPAD 346 C2. Ordering number RS 621 002-AA3. Rated frequency fn = 50 Hz4. Auxiliary voltage Uaux = 110 V dc5. Accessories 2 bus connection modules SPA-ZC 17 MM2A6. Special requirement -

Order data

35

Dimensiondrawings andmounting

The basic model of the protection relay case isdesigned for flush-mounting. When required,the mounting depth of the case can be reduced.Three types of raising frames are available: type

SPA-ZX 301 reduces the depth by 40 mm, typeSPA-ZX 302 by 80 mm and type SPA-ZX 303by 120 mm.

Raising frame

SPA-ZX 301SPA-ZX 302SPA-ZX 303

219179139

74114154

a b

226

162

136

229

293259

3034

a b

Panel cut-out

214 ±1

139

±1

Fig. 10. Dimension and mounting drawings for differential relay SPAD 346 C.

The relay case is made of grey anodized profilealuminium.

The rubber gasket fitted to the mounting collarprovides an IP 54 degree of protection by enclo-sure between the relay case and the mountingbase.

The hinged cover of the case is made of transpar-ent, UV-stabilized polycarbonate polymer andprovided with two sealable locking screws. Therubber gasket of the cover provides an IP 54degree of protection between the case and thecover.

The required input and output connections aremade to the screw terminals on the rear panel.The energizing currents are linked to the termi-nal block X0 which consists of fixed screwterminals. Each terminal screw is dimensionedfor one wire of maximum 6 mm2 or two wires ofmaximum 2.5 mm2.

The terminal blocks X1 and X2 contain dis-connectable multi-pole screw terminals. Themale part of the disconnectable terminal blocksis attached to the I/O module. The female parts,which are included in the delivery, can be lockedto the male part with fixing accessories andscrews.

The external control inputs of the modules areconnected to the terminal block X1. The tripsignals are obtained from the the terminal blocksX1 and X2. The alarm signals are obtained fromX2. Each terminal of X1 and X2 is dimensionedfor one wire of max 1.5 mm2 or two wires ofmax. 0.75 mm2.

The 9-pole D-type connector is intended forserial communication.

ABB Transmit OyRelays and Network ControlP.O.Box 699FIN-65101 VAASAFinlandTel. +358 10 224 000Fax. +358 10 224 1094

1MR

S 7

5009

6-M

UM

EN

Communications

Services

Meter & LoadManagementInformation

Management

NetworkManagement

StationAutomation

Panorama is the standard for a comprehensive rangeof integrated solutions for efficient and reliablemanagement of power networks. Using innovativeinformation technology, Panorama delivers total controlof the power process, from generation to consumption.The Panorama standard covers six application areas,each offering specific solutions.