7vh80

8/7/2019 7VH80

1/16

High impedance differential relay 7VH80

Fig 1. High impedance differential protection relay 7VH80

Features

l Robust solid state design.l Inrush stabilization through

filtering.l Auxiliary dc supply monitor.l

Fast operating time (15ms).l Voltage operated target

indicator.l

Simple voltage setting.Applications

The 7VH80 relay is designed forfast and selective differentialprotection based on the highimpedance circulating currentprinciple. It is used for theprotection of machine statorwindings, busbars andtransformer and reactorwindings against phase to phase

and phase to earth short circuits.

Design

The withdrawable module ishoused in a 7XP2010 metalcase suitable for flush mounting.The plug connector at the rear ofthe case has one screw and onesnap on terminal for eachconnection point. The plugconnector is marked with a co-ordinated system depending onthe mounting location e.g. 4A1denoted row 4, block 1, column

1. The individual connectionsare marked sequentially from leftto right (viewed from the rear).See fig. 3.

Mode of Operation

The 7VH80 relay is a single pole

sensitive current relay. The ACinput impedance of the relay isadjusted by means of a series ofhigh wattage resistors. Therelay setting is a voltage pick-upvalue that is set by means ofconnecting pins that are insertedin the front of the relay module.When the pin is inserted, thecorresponding series resistor isshorted out and when the pin iswithdrawn, the resistor is incircuit. Each pin socket has avoltage value. The relay voltagesetting is determined by addingup the socket value all of thewithdrawn pins (series resistorsin circuit) plus the minimum basevoltage setting. These seriesresistors are termed stabilizingresistors and the setting on therelay determines the steadystate rms voltage required forrelay operation.

The input from the CTs isconnected to terminals 1A1 and1A2. The relay input transformergalvanically isolates the relay

static measurement circuit fromthe main current transformers.

The AC measured current isband pass filtered and rectifiedto a proportional dc voltage.This voltage is monitored by aSchmidt trigger circuit. If the set

dc voltage, equivalent to therelay nominal operating currentof 2OmA is exceeded, then thetrigger operates to energise thecommand output relay as well asthe operation indicator.

The auxiliary dc supply isconnected to terminals 4A1(+ve)and 4A2(-ve). An auxiliary dcsupply monitoring circuitconsisting of a green LED and aN/C relay contact is provided toindicate the status of the dcsupply.

The relatively simple electronicdesign of the 7VH80 provides arobust and reliable relay suitablefor all high impedance circulatingcurrent protection applications.

The employ of a solid statemeasurement circuit ensures arelatively constant and fastoperating time.

See fig. 2 for the connection

diagram.

8/7/2019 7VH80

2/16


2

Fig 2. Connection diagram for 7VH80 relay

Fig 3. 7VH80 relay in flush mount case

8/7/2019 7VH80

3/16


3

Technical Data

CT CircuitsNormal Frequency 50 Hz or 60 Hz

Thermal Withstand1 sec 5 x setting (volts)Continous 2 x setting (volts)

Measuring Circuit

Setting Range:24 Volt version 24+24+24+24+24+120 Max 240 Volt6 Volt version 6+6+6+6+6+30 Max 60 Volt

Tripping Time2 x setting 30 ms3 x setting 20 ms5 x setting 13 ms

Pick up to drop out ratio 0.95

Reset Time 20 ms

Supply and Reset voltages24V dc 20%3OV dc 20%48V dc 20%110/125V dc 20%22OV dc 20%

Supply Burden (at rated voltage)

For all voltagesQuiesent 4 WPicked up 5 W

Contacts Command Output Alarm

Number of Contacts 2 N/O 1 N/CMake 1 000 W/VA 3OW/VABreak 3OW/VA 3OW/VACarry 30A for 0,5s and 5A continuous

Max. Switching Voltage 25OV AC/dc

Indication 1 off voltage operated target indicator

Environmental Withstand

Max. Temperatures, duringService - 10C to + 55CStorage - 25C to + 55CTransport - 25C to + 70C

Humidity, acc. to DIN 40 040 class F

8/7/2019 7VH80

4/16


4

Vibration, service 0.5g between60 to 500 Hz

0.035 mm amplitudebetween 1 0 to 60 Hz

Vibration, transport 2 g between8 to 500 Hz7,5 mm amplitudebetween 5 to 8 Hz

Insulation TestsHV Test IEC 255-5 2kV (rms)., 50/60 Hz; 1 minImpulse Test IEC 255-5 5kV (peak); 1,2/50 s; 0,5J; sec

3 positive and 3 negativeshots at intervals of 5s

High Frequency Test 2,5 kV (pea k); 1 MHz;IEC 255-22-1 = 1,5 s; 400 shots/sClass Ill duration 2s

EMI Test

IEC 801-3 20 MHz to 1000 MHz at 10V/m fieldANSI/IEEE C37.90.2 strength

Weight Dimensions

Withdrawable Module 3U; 12 slots of 5.08 mm

Case

Standard metal case for 7XP2010-2Cflush mounting

Size 1/6 of 19" rack

Extra frame for surface 7XP21mounting

Enclosure protection IP51Mass Approx. 1kg

Modular Terminal Block

Each terminal provides one snap-on 1.5 mm2

wireconnection one tunnel type screwconnection

8/7/2019 7VH80

5/16


5

Ordering Data

Order No.High impedance differential relay 7VH80 - C ASupply Frequency50 Hz60 Hz

01

Voltage Range24V Steps with Flag6V Steps with Flag

01

Auxiliary Supply Voltage (Not Isolated)24V dc30V dc

48V dc110/125V dc220V dc

12

345

Case OptionModule in Case C

With VaristorWithout Varistor

01

Reset Voltage24V dc30V dc48V dc

110/125V dc220V dc

123

45

ORDERING DATAPlease specify the varistor type required for your application or consult your nearest Siemens office.

8/7/2019 7VH80

6/16


6

Fig 4. Restricted earth fault protection of power transformer windings

8/7/2019 7VH80

7/16


7

Fig 5. Phase and earth fault protection of a generator

Relay setting

8/7/2019 7VH80

8/16


8

List of abbreviations

IE = Current transformer exciting current at relay setting voltage.(referred to the CT secondary current)

IF = Maximum value of primary through fault current for which protection must remain stable.

IFM = Maximum value of primary fault current for internal fault.

lp = Primary current for operation of protection.

IR = Relay operating current.

ISH = Current in shunt resistor at relay setting VR.

N = Turns ratio of current transformer.

n = No. of current transformers in parallel with relay.

RCT = Secondary resistance of current transformer.

RL = Lead resistance between furthest current transformer and relay connection point.

RR = Relay impedance.

RSH = Value of shunt resistor.

VF = The theoretical voltage which would be produced across the relay circuitunder internal fault conditions. V

I

N R R R

F

FM

CT L R + +( )2

VK = Knee point voltage of current transformer.

VP = Peak voltage across relay circuit under maximum internal fault conditions.

VS = Minimum Setting voltage. (Calculated)

VR = Relay setting voltage.

K = Varistor constant.

B = Varistor constant.

8/7/2019 7VH80

9/16


9

Calculation of relay setting

The minimum setting voltage toensure stability is

( )VI

NR R

S

FM

CT L + 2

The relay plug setting voltage VRmust be set to the nearest tapabove Vs. The minimum knee

point voltage must be VK 2VR.The operating current of therelay is 20mA irrespective of thevoltage selected excluding thecurrent drawn by the externalvaristor. When a standardvaristor is included with therelay, the relay operating current

including the varistor is given inthe table below (Fig 1.). It mustbe appreciated that varistorshave large tolerances and thesefigures are given for guidanceonly.

Setting Voltage VRin volts

24 48 72 96 120 144 168 192 216 240

Relay current IR(including varistor) in mA

20 20 20 22 22 23 25 26 28 30

Table 1

The primary current foroperation is given by

lP = N (IR + nIE)If the resultant value of lP is toolow it may be increased by theaddition of a shunt resistor RSHto give a current of ISH = VR/ RSHThe new increased value ofprimary current lP = N (IR + nIE + ISH)

Setting advice

With particular reference tohigh impedance busbar

protection, the plant andequipment should haveprotection with the followingfeatures:

adequate sensitivity

fast response time

stability, when external faultsoccur

selectivity to allowdisconnection of only thefaulted section

permanent supervision of thecurrent transformers(optional)

Relay operation shall notoccur on:

saturation of the CTs by thetransient dc componentwhen a serious fault occursoutside the zone

accidental open or shortcircuit of the secondary ofone or more CTs

Two types of configurationare generally provided:

single phase faults; requiringone 7VH80 relay

polyphase faults; requiring agrouping of three (3) 7VH80relays

Current transformersupervision, if called for,protects against the accidentalopening of a CT connection.This occurrence normallycauses a fault current that istoo low to activate the relaycircuits, however the condition

should be signalled before theappearance of an actual fault.The supervision would registerthe low unbalanced current andcontrol a time delayed outputalarm.

Knee-point voltage of currenttransformers

The CTs will not be saturatedby the short-circuit current if theknee-point voltage is greaterthan twice the maximumvoltage likely to be applied

across the terminals of therelay during the fault.

V V V V RMAX K F K

= 2 2 ( )

At the maximum secondarythrough fault current thevaristor should limit the voltageto 1 5OOV rms if possible.

Determination ofmagnetizing current IE

The manufacturer of thecurrent transformer suppliesthe magnetic characteristics

from which the magnetizingcurrent curve versus the

secondary voltage is shown.From this curve, it is easy todetermine the magnetizingcurrent IE for a secondaryvoltage of V.

CT supervision circuit

If the CTs have broken orshorted connections, theprotective relay may detect thiscondition as a busbar fault andtherefore trip all the circuitbreakers in that zone.If several CTs are associatedin the zone, the disconnectionof one of them (correspondingperhaps to a lightly loadedfeeder) will result in a very lowfault current measurement.If this unbalance is lower thanthe 7VH80 setting, thiscondition will not be detected.Therefore a more sensitivemonitoring circuit is required forCT supervision.

This supervision circuitoperates with a time delay to

avoid a false alarm signal incase of a busbar fault. Whenchoosing a setting the followingrule should generally beadopted:The supervision relay must besensitive to an unbalancecorresponding to a busbarcurrent of 25A or to 10% of thecurrent in the least loadedingoing or outgoing feeder. Thehighest current value will beadopted.Further details may be providedon request.

8/7/2019 7VH80

10/16


10

Ammendment 1 to page 10 of 7VH80 Publication G 53300-Y33-U19-1-18

Varistor Selection

Each 7VH80 relay is normallyapplied with an external varistor

which must be connectedacross the relay input terminals.The varistor limits the voltagedeveloped across the CT andrelay terminals under faultconditions.A varistor is a non-linear orvoltage dependent resistor. It isa ceramic semi-conductingresistance material in which the

relationship between resistanceand applied voltage is non-linear,

i.e. an increase in the appliedvoltage will result in a decreasein the resistance and hence anincrease in the current. Thechange in resistance occursinstantaneously.The electrical characteristics canbe expressed as V = KI

Bwhere

K and B are constant for any onevaristor.

If the current transformersecondary voltage is to be

limited to a safe levelduring maximum internal faultconditions then a varistor maybe required. Generally if

VRMAX > 2KVthen a varistor is required

V V V V RMAX K F K

= 2 2 ( )

Relay Voltage Setting K B Varistor type

Up to 125V rms 450 0.25 600A/S1/S256

125 - 240 rms 900 0.25 600A/S1/S1088

Table 2

K Characteristic Max.Continuous Rating - rms

450 2OOV

900 35OV

Varistor Assembly Type Unit K Value Short Time Rating

Standard 600A/S1/S256 450 22A for 3 seconds

30A for 2 seconds

45A for 1 second

Standard 600A/S1/S1088 900 17A for 3 seconds

30A for 1.5 seconds

39A for 1 second

Table 3

Installation andCommissioning Instructions

Installation

Protective relays, althoughgenerally of robust construction,require careful treatment prior toinstallation. By observing a fewsimple rules the possibility ofpremature failure is eliminatedand a high degree ofperformance can be expected.

The relays are either despatchedindividually or as part of apanel/rack mounted assembly incartons specifically designed toprotect them from damage.Relays should be examinedimmediately they are received toensure that no damage has been

sustained in transit. If damagedue to rough handling isevident, a claim should bemade to the TransportCompany concernedimmediately and the nearestSiemens Office should bepromptly notified. Relays whichare supplied unmounted andnot

8/7/2019 7VH80

11/16


11

intended for immediateinstallation should be returned totheir protective cartons.

Care must be taken when

unpacking and installing therelays so that none of the partsare damaged or their settingsaltered and must at all times behandled by skilled persons only.

Relays which have beenremoved from their cases shouldnot be left in situations wherethey are exposed to dust ordamp. This particularly appliesto installations which are beingcarried out at the same time asconstruction work.

If relays are not installedimmediately upon receipt theyshould be stored in a place freefrom dust and moisture in theiroriginal cartons and wheredehumidifier bags have beenincluded in the packing theyshould be retained.

The action of the dehumidifiercrystals will be impaired if thebag has been exposed to dampambient conditions and may berestored by gently heating the

bag for about an hour, prior toreplacing it in the carton.

Dust which collects on a cartonmay, on subsequent unpacking,find its way into the relay; indamp conditions the carton andpacking may becomeimpregnated with moisture andthe de-humidifying agent willlose its efficiency.The storage temperature range

is -25 and +55C.

The installation should be clean,dry and reasonably free fromdust and excessive vibration.The site should preferably bewell illuminated to facilitateinspection. The relay should bemounted in the cut-out or rackprovided (Fig 3.) and wiredaccording to Figure 2 or therelevant drawing or schematicdiagram.

Commisioning preliminaries

Inspection

Carefully examine the moduleand case to see that no damagehas occurred during transit.Check that the relay serialnumber on the module, caseand cover are identical, and thatthe model number and ratinginformation are correct.

Check that the external wiring iscorrect to the relevant relaydiagram or scheme diagram.

Particular attention should bepaid to the correct wiring and

value of any external resistorsindicated on the wiringdiagram/relay rating information.

Note that shorting switchesshown on the relay diagram arefitted internally across therelevant case terminals andclose when the module iswithdrawn. It is essential thatsuch switches are fitted acrossall CT circuits.

If a test block is provided, theconnections should be checkedto the scheme diagram,particularly that the supplyconnections are to the live sideof the test block.

Earthing

Ensure that the case earthingconnection at the rear terminalblock, is used to connect therelay to a local earth bar.

Insulation

The relay, and its associatedwiring, should be insulationtested between:

all electrically isolated circuits

all circuits and earth

An electronic or brushlessinsulation tester should be used,having a dc voltage notexceeding 1000V. Accessibleterminals of the same circuitshould first be strappedtogether. Deliberate circuitearthing links, removed for the

tests, must subsequently bereplaced.

It is only necessary to check therelay at the setting on which it is

to be used. The relay must notbe used at any setting other thanthat for which the setting hasbeen calculated.

Commissioning TestsTest Equipment

1 Secondary injection testequipment capable ofproviding an AC voltagesupply of up to at least120% of the relay setting.

1 Test plug for use with test

block if fitted.3 Calibrated multimeters 0-10amp AC 0 - 400 volt AC.

1 Set of primary injectiontesting equipment

.

General

If the relay is wired through atest block it is recommendedthat all secondary injection testsshould be carried out using thisblock.

Ensure that the main systemcurrent transformers are shortedbefore isolating the relay fromthe current transformers inpreparation for secondaryinjection tests.

Danger

Do not open circuit thesecondary circuit of a currenttransformer since the highvoltage produced may belethal and could damage

insulation.

Secondary injection testing

Connect the circuit as shown inFigure 6 and ensure that thecurrent transformer primary isopen circuit and that if anyearthing connections are fitted,they do not short out theprimaries of any currenttransformers.

Increase the voltage until the

relay just operates.

8/7/2019 7VH80

12/16


12

Record the current at which therelay operates (A2). It should beapproximately 2OmA at setting.

Note also the voltage at whichthe relay operates which shouldcorrespond to the setting VR ofthe relay with a tolerance of 10%. The total secondarycurrent for operation will begiven on ammeter A1.This testshould be repeated for eachpole of the relay.

Record the value at which therelay picks up and then reducethe voltage until it drops off.From these two values calculate

the drop off/pick up value. Itshould be approximately 0,95.

Primary injection testing

It is essential that primaryinjection testing is carried out toprove the correct polarity ofcurrent transformers.Before commencing any primaryinjection testing it is essential toensure that the circuit is dead,isolated from the remainder ofthe system and that only those

earth connections associatedwith the primary test equipmentare in position.

Primary fault setting

The primary fault setting of anybalanced scheme can bechecked using the circuit shownin Figure 7. The primary currentis injected into each currenttransformer in turn andincreased until the relay

operates. The voltage at whichthe relay operates should bewithin 10% of the relay setting

voltage VR. The primary currentfor operation and relay currentshould be noted.

In the case of machineprotection similar tests must becarried out by injecting first intoeach current transformer in turnto determine the primary faultsetting.

For large machines the machineitself can be used to provide thefault current to check the primaryfault setting as shown in Figure

10. The machine should be runup to speed with no excitation.The excitation should then beincreased until the relays haveall operated. The primarycurrent, relay current and relayvoltage should be noted as eachrelay operates.

Through fault stability

With any form of unbalancedprotection it is necessary tocheck that the current

transformers are correctlyconnected. For this purposewith a restricted earth faultscheme the circuit shown inFigure 6 may be used. Duringthis test the relay is shorted outand the spill current through therelay circuit A2 is measured.The current is increased up to asnear full load as possible andthe spill current noted. The spillcurrent should be very low, onlya few milliamps if the

connections are correct. A highreading (twice the injectedcurrent, referred through the

current transformer ratio)indicates that one of the currenttransformers polarity is reversed.

Injection should be carried outthrough each phase to neutral.

Where primary injection is notpracticable as in the case ofrestricted earth fault protectionon a transformer it may bepossible to check stability bymeans of back energising thetransformer from a low voltagesupply as shown in Figure 9.

(eg. 38OV)In the case of machineprotection similar stability testsmust be carried out by injectinginto one and out of anothercurrent transformer connectedon the same phase.

For large machines, the machineitself can be used to provide thefault current, but the short circuitmust now be fitted as shown inFigure 11. The machine shouldbe run up to normal speed andthe excitation increased until theprimary current is approximatelyfull load, when the spill currentshould be checked.

All other types of balancedprotection should be tested in asimilar manner.

At the conclusion of the testsensure that all connections arecorrectly restored and anyshorting connections removed.

ADDENDUM COMMISSIONING TEST RECORD DATEHIGH STABILITYCIRCULATING CURRENT RELAYTYPE 7VH80STATION CIRCUITRELAY MODEL NO. SERIAL NO.SETTING RANGE CT RATIOSETTING VOLTAGE RELAY SETTING

SHUNT RES.OHMS (if fitted)

TYPE OF EXT. CALCULATED PRI.VARISTOR OP CURRENT

8/7/2019 7VH80

13/16


13


TEST RESULTS

Relay CT Shorting SwitchSecondary Voltage to operate relay

Phase Total Current (A1) Relay Current (A2) P.U. Volts D.O. Volts

A

B

C

Drop off / Pick up ratio check

Table 5

Primary Current to operate relay

Phase Primary Current A1 Relay Current A2 Relay Voltage

AB

C

N

Table 6

Stability check by primary injection

Restricted Earth Fault

PhasesA1

Primary CurrentA2

Spill Current

A - N

B - NC - N

Table 7

Circulating Current between two or more sets of current transformers

PhasesA1

Primary CurrentA2

Spill Current

Al -A2

Bl - B2Cl -C2

Table 8

Where more than two sets ofcurrent transformers areinvolved, injection should becarried out between set 1 andeach other set in turn.

Maintenance

Periodic maintenance is not mounted in poor environmentalnecessary. However, periodic conditions.inspection and test is Repeat secondary injection testsrecommended. This should be to prove correct operation,carried out every 12 months or making sure the circuit breaker

more often if the relay is trips when the relay operates.operated frequently or is

8/7/2019 7VH80

14/16


14

Fig 6. Secondary injection test

Fig 7. Primary fault setting test

8/7/2019 7VH80

15/16


15

Fig 8. Through fault stability test


8/7/2019 7VH80

16/16


16

Fig 10. Primary fault setting test


The information contained in this publication is subject to change without prior notice.

Siemens LimitedP O Box 207 lsando 1600South AfricaTelephone (011) 921-7000

Issued by Energy and Automation Group - Power Transmission and Distribution

7vh80

Documents