automatic capacitance and power factor field test set 12 kv 2.4 … · 2013-11-22 · xp, the so...

Presco AGZürcherstrasse 70 -CH 8104 Weiningen Tel. + 41 44 750 63 63 Fax + 41 44 750 63 66P.O. Box 155 Switzerland www.prescoag.com [email protected]

FT12_Marketing-Englisch_neu_neu.DOC / KF/16.08.2004 of 17

Automatic Capacitance and Power FactorField Test Set 12 kV –2.4 kVA

Type FT-12

Description –Technical Data –Features –Accessories –Options

www.prescoag.com

Presco AG


1. General

1.1 Features

Measurement and operation according IEEE standard 62Screened HV supply with ground capacitance lower than 1 pFMeasurement of grounded and ungrounded objects without any reconnectionBuilt-in extremely stable standard capacitor 100 pF / 12 kVBuilt-in automatic interference suppressionFully automatic measurementsMeasurement of capacitance, tanDelta, Power Factor, Specimen current (real, imagi-

nary, absolute), Powers (apparent, active, reactive), Inductance, Quality Factor, TestVoltage, Frequency.

Highest resolutionData storage feature (internal NVRAM)RS 232 interface for data download as standardThe system with the lightest weight on the marketComplete system including all cablesLarge number of optionsIncluding test certificate with traceability to international standards

Presco AG


2. Function PrincipleThe measuring instrument compares the current of the test object CX (unknown capacitor)with the current of the so called standard capacitor CN.

Fig. 1 shows the principle of the comparison.

Fig.. 1

The “Current Comparator" is a magnetic "comparison instrument”. On a iron core of high permeability with the shape of a ring there are several windings. If the sum of the amperewindings is zero, the magnetic flow in the core becomes zero too. The voltage on the "Ni"-winding is proportional to the magnetic flux. If the flux becomes zero the voltage on the Ni

winding will also be zero. The very low voltage on the Ni winding is amplified with amplifier"Ai" and then displayed on bar graph.

For the balanced state the following conditions are valid :

The current Ix trough the test object is:

I U G j Cx t xp xp .( . . ) (1)

The current IN trough the standard capacitor is:

I U j CN t N . . . (2)

The IN current is transformed by a current transformer and a current-voltage converter intovoltage which is proportional to IN. By the analog-digital-converter A/DC (in Phase) andA/Dtg (90 ° phase lag) a part of the IN current is fed into the current comparators windingNb.

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If the windings Nx and NN as well as the analog-digital-converters A/DC and A/Dtgare setproperly, the magnetic flux in the iron core becomes zero. This is the so called balancedstate.

Mathematically, the condition for the balanced state is :

U N j C G U j C N k j Nt x xp xp t N N b. .( . . ) . . . . .( . ). (3)

By application of equation (3), the values of Cxp and Gxp can be calculated. In practice,instead of Gxp, the so called dissipation factor, or tangent delta (tan) is calculated. Thedissipation factor is defined as the ratio of the reactive power in the test object to the ac-tive power. In case of a sinusoidal signals and in the complex notation the dissipation fac-tor corresponds of the rest-angle of the impedance vector :

tgG

Cxp

xp

.

From the equation (3) follows :

C CN k N

Nxp NN b

x

.. .

(4)

and

tgN

N k Nb

N b

. .

. (5)

If the values k and Nb are chosen correctly, Cxp can be determined with a very high resolution: the winding NN can be adjusted over two decades (10x10 + 10 x 1) and the A/D-Converter(12-bit) adds 3 digits. The overall resolution is more than 5 decades (<10 ppm ).

For measurements of inductance and quality factors of an high voltage the system will re-verse the polarity of the Ix current. In this case a negative capacitance value is displayed. Byselecting Inductance with one of the hot keys, the corresponding values of inductance LX andthe quality factor Q can are calculated by using the following formulas :

LCx

x

1

2 .

and

Qtg

1

The micro controller reads the value of the standard capacitor CN from the EPROM, then cal-culates the Cx and tanvalues using equations (4) and (5) and displays these values on the"= Cx " and "= tg" displays.

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For calculation and display of the test voltage Ut the micro controller samples some periodsof the signal "Utg", calculates the peak value (Utgp) and under consideration of CN value andthe measuring frequency determines the value to be displayed (Udp):

UU T

a C Rdptgp

N c

*

*.

12

with a = ratio of the current transformer in the IN circuit

Rc = resistance in the current voltage converter

T = integration time of the phase shifter

+

NxN

N

NRJ

C Cx N

CT

90 deg

Rxp

I

I

x

N

b

~

a

+/- 1

IU Phase

Shifter

+/- 1Nbal

IU

+

90 deg

PhaseShifter

+/- 1 ~

+/- 1

AC frommains

IU

voltagemeasurement

NRJ

IU

NNI

IU

NullIndicator

High Voltage

Ungrounded Test Object

GUARD

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3. Maintenance measurements on transformersThe below statements are to be taken as an example as beside transformers, a lot of differ-ent objects, such as CTs, PTs, switch gear, insulators, grading capacitors, bushings or evenmotors and generators can be measured.

To increase the reliability of energy systems it is proposed to periodically test the differentobjects of an energy generation, transportation and distribution system. The main task is todetect deterioration / ageing of an insulation BEFORE there is a breakdown. A breakdown ofa big transformer could lead to losses of around CHF 50'000 per hour due to the fact that incase of a breakdown the energy cannot be sold. Not to talk about the losses because ofmissing energy.

Fig.1.

To prepare a transformer for measurements, the following is proposed according to the stan-dards (please refer to the above drawing):

- Measure between the windings (CA, CB) and between the windings and the tank (CG)

- All windings must be fully immersed in oil

- Each group of windings must be individually shortened

- All bushings have to be installed

- Winding temperature should be near 20 °C

In addition it is proposed to disconnect all overhead lines from the transformer under test toavoid to pick up noise / interference and in order not to have a stray capacitance in parallelwith the test object when measuring grounded objects such as e.g. CG (HV winding to tank).

CA

CB

CG

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By selecting the different test modes, all combinations of measurements according theANSI/IEEE Standard 62 can be measured without any rewiring (see Fig. 1 on previouspage) :

UST A : Ungrounded specimen test cannel A, capacitance measured = CA , (CB andCG guarded)

UST B : Ungrounded specimen test cannel B, capacitance measured =CB , (CA andCG guarded)

UST A+B : Ungrounded specimen test cannel A + B, capacitance measured = CA + CB

GST A+B: Grounded specimen test, cannel A + B, capacitance measured = CA + CB +CG

GSTgA: Grounded specimen test with guarded A (connected to "V"), capacitancemeasured = CB + CG

GSTg B: Grounded specimen test with guarded B (connected to "V"), capacitancemeasured = CA + CG

GSTg A+B: Grounded specimen test with guarded A and B (connected to "V"), capaci-tance measured = CG

The measurement results are displayed on a graphic LCD display. The display helps theuser to perform tests with minimal steps of operation.

The measurement results can be stored in the RAM of the processor for a later download toa PC. The data storage feature allows to store up to 10 Files with up to 50 measurement re-cords each.

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4. Technical Data (basic unit)

Power FactorRange -0.995 - + 0.995Resolution 0.0001Uncertainty 1% of rdg 1 … 2 digits

Dissipation FactorRange 0–10 (1'000%)Resolution 1 10-4 (via software 1 x 10-6)Uncertainty 1 % of rdg 1 … 2 digits

CapacitanceRange 0 - 1 FResolution 0.01pFUncertainty 0.1% of rdg

InductanceRange 191H - infiniteResolution 0.1 mHUncertainty 0.2 % of rdg

Test voltage (peak/2)Range 0 - 12 kVResolution 1 VUncertainty 1 % of rdg

Test Current (absolute, real part and imaginary part)Range 0 - 5 AResolution 1 nAUncertainty 1 % of rdg

Active PowerRange 0 - 999.9 kWResolution 0.1 nWUncertainty 1.5 % of rdg

Active Power (recalculated for 10 kV)Range 0 - 999.9 kWResolution 0.1 nWUncertainty 1.5 % of rdg

Reactive PowerRange 0 - 999.9 kVarResolution 0.1 nVarUncertainty 1.5 % of rdg

Apparent PowerRange 0 - 999.9 kVAResolution 0.1 nVAUncertainty 1.5 % of rdg

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FrequencyRange 45-65 HzResolution 0.1HzUncertainty 1 % of rdg

Measuring modes UST A, UST B, UST A+B, GST A+B, GSTgA, GSTg B, GSTg A+B

Automatic Noise Suppression Suppresses interference up to 30 times ofmeasuring signal (automatically)

Safety FeaturesZero Start InterlockHand Held Safety Switch with indicationGround Loop Check with indication

High Voltage SupplyContinuously adjustable from near Zero up to 12 kVOutput Current 200 mA 5 Min. on, 15 Min. offOutput Current 100 mA continuousReversal switchBuilt-in extremely stable standard capacitor 100 pF / 12 kVEarth capacitance of the high voltage < 1 pF

Additional FeaturesBuilt-in RS232 interfaceData Storage Feature : Possibility to save up to 10 files with up to 50 measurement re-cords each for later download to PCList function to display the internally stored records as a tableSelectable Power factor display : as tanDelta, Power Factor, direct, in per-

cent or permilRugged construction, built-in robust flight cases, no need for additional transport boxes.Includes a box for cables / accessoriesTest certificate with traceability to international standards included

Download Softwarethis software is compatible with Windowsfunctions:down load of dataprocessing the measurementsdisplaying the measurementsprintingsavingtransfer to Exceldata transfer via RS232 interface

Presco AG


Reference conditions

Minimal current through standard capacitor 35 ATemperature 23° C 2° CHumidity, non condensing 45 ... 75%Altitude (pressure) 101.3 kPa

Rated range of use

According IEC 359Temperature 5° C ... 40° CHumidity, non condensing 20 ... 95%Altitude (pressure) 70 ... 106 kPa

5. Applicable StandardsIEEE C57.12.90-1987 test code for liquid-immersed distribution,

and regulating transformers and guide forshort circuit testing of distribution andpower transformers

IEEE Std 62-1978 IEEE Guide for Field Testing Power Appa-ratus Insulation

IEC 348 Safety requirements fro electronic measur-ing apparatus

IEC 359 Expression of the performance of electricaland electronic measuring equipment

6. PhysicalDimensions HV unit 432 x 266 x 330 mm, 17 x 10.5 x 12.9 inchDimensions CTR unit 432 x 266 x 330 mm, 17 x 10.5 x 12.9 inchWeight of HV unit approx. 28 kgWeight of CTR unit approx. 23 kgRugged construction, built-in robust flight cases, no need for additional transport boxes.Includes a box for cables / accessories

Presco AG


7. Scope of Supply / Options

7.1 Included AccessoriesShielded measuring cables 2 pcs., 20 m eachShielded HV cable with hook 20 mLarge alligator clips 2 pcs.Small alligator clips 2 pcs.Ground cable with large alligator clip 20 mCable with safety switch 20 mPower supply cable 1 p.Instruction manual 1 p.Calibration Certificate 1 p.Download software 1 p.

8.2 OptionsResonating Inductor Type FT-12RI

For range extension of type FT-12 Capacitance and Power Factor Field Test Set

Rated Voltage 12 kVMax. current 4.5 AMax. reactive power 50 kVarRange extension @ 50 Hz up to 1.1 FRange extension @ 60 Hz up to 880 nF

With current indication for easy tuningProvision for safety interlockWith built-in over temperature protection

Weight approx. 85 kgDimensions (W x D x H) approx. 350 x 480 x 700 mm

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Unit for measurement of short circuit impedance of transformers Type FT-12CI

to be used together with FT-12 CTNominal output 0 ... 200 V, max. 10 A

0 ... 60 V, max. 20 A0 ... 20 V, max. 25 A0 ... 2 V, max. 35 A

Rating 1 min on 2 min. offInput voltage 0 ... 230 V, 50 or 60 HzBuilt-in standard capacitor 100 nF Remark : the specified value of the stan-

dard capacitor is matched to the respective meas-uring ranges.

Inductance measurement range 0.1 mH ... 100 H fully auto ranging4 terminal measurementWeight app. 25 kgDimensions w d h 432 x 266 x 330 (in mm), 17 x 10.5 x 12.9 (in inch)

Presco AG


Oil Test Cell Type OT-SCL12

Measurements according to IEC 250 and IEC 247Volume of oil sample approx. 0.75 lInter electrode distance 9 mmCapacitance of the empty cell approx. 60 pFtanof the empty cell < 1 * 10-4Maximum voltage for empty cell 5 kVTest voltage of empty cell 10 kV / 1 Min.Maximum voltage for filled cell 10 kVTest voltage filled cell 12 kV / 1 Min.Field strength at 10 kV 10 kV / cmConnector LEMO 3Weight approx. 4.2 kgDimensions approx. 330 mm height x 185 mm diameter

Presco AG


Calibration Standard Type TG-CALNominal Voltage 10 kVNominal capacitance 100 pFtanDelta values 0, 0.1, 0.05, 0.01. 0.005, 0.001 (0, 10%,

5%, 1%, 0.5%. 0.1%). other values possibleupon request

Dimensions : approx. 150 x 150 x 300 mmWeight approx. 4 kg

Reference conditions

minimal current through standard capacitor 35 Atemperature 23° C ± 2° Chumidity 45 ... 75%altitude (pressure) 101.3 kPa

Rated range of use

according IEC 359temperature 5° C ... 40° Chumidity, non condensing 20 ... 95%altitude (pressure) 70 ... 106 kPa

Adapter for ext. Standard capacitor Type FT-12AD

To be used instead of the FT-12 HV together with an external HV Power Supply

Connectors : LEMO 3 for Standard Capacitor

Banana socket for Standard Capacitor (inparallel with the LEMO3)

banana socket for GUARD

banana socket for EARTH

incl. over voltage protection

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Professional Partial Discharge Field Measuring System Type FT-12PD

DetectorPD ranges 10 - 100 - 1000 - 10’000 - 100’000 pCPD input impedance 50 PD readout LCD graphics digital, analogue or phase re-

solved patternPD uncertainty ± 3% of rangePD output ± 1V, 50 Low pass of broadband filter selectable 200 kHz / 6 dB or 400 kHz / 6dBHigh pass of broadband filter selectable 20 kHz / 6 dB or 100 kHz / 6dBMiddle frequency of narrow band filter tuneable 60... 250 kHzBandwidth of narrow band filter 9 KHzGating up to 6 individual adjustable gates (hardware

gating)Auto calibration 10 pC–10 000 pCAuto ranging PD and voltage measurementOscilloscope output Voltage proportional sine and PD proportional

signalVoltage measurement 100 V... 1 MVFrequency range of voltage measurement 45 ... 150 HzVoltage scale factor 1 ... 10' 000Uncertainty of voltage measurement 1 % of readingDisplay analogue, digital, PD activities as y(t) plot as

lines or dots, persistent or cumulated, PD pat-tern

Interface RS232 (for data transfer and remote control)Power mains 230/115 V / 50/60 Hz / 25 VA

Coupling devicePD and AC signal are mixed in a single 50 coax cable

input impedance of PD-channel 200 AC channel input impedance 1 MBandwidth of PD-channel 20 kHz ... 2 MHz / 6 dBBandwidth of AC-channel 45 Hz ... 450 HzMax. AC input voltage 100 Vpeak/2AC divider capacitance 1 FOutput impedance 50 / 20 kHz ... 2 MHz

Battery Calibrator

Supplied with calibration certificate

Charge values 5 - 10 - 100 - 1000 pCOutput capacitance < 150 pFRise time < 60 nsPower supply 9 V battery type 6LR61Battery life > 20 hours of continuous operationSynchronisation optical pick-up of power frequency from

nearby lampsUncertainty ± 3%

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High Voltage Cable

Coaxial high flex / 20 m, with hook

Built-in Coupling Capacitor

Nominal Capacitance 1'000 pF 20 %Nominal voltage 15 kVPD level < 5 pC

Dimensions of system approx. 510 x 490 x 450 mmWeight approx. 17 kg

Cable accessories Type FT-12CA

High voltage cable with adapter for hook, big and small crocodile clips, incl. hook andcrocodile clips.

Warning lamp Type FT-12WL

Red flashing lamp with 20 m cable.

Is ON when HV is switched on

Presco AG


FT-12 System in various configurations

FT-

12C

T

FT-

12C

T

FT-

12C

T

FT-

12C

T

FT-

12C

T

FT-

12H

V

FT-

12C

I

FT-

12H

V

FT-

12H

V

FT-

12H

V

FT-

12R

I

FT-

12R

I

FT-

12P

D

FT-

12P

D

FT-

12F

ield

Test

Sys

tem

Mea

suri

ng

Ran

ges

atfu

ll12

kV/5

0H

z(6

0H

z)

C:u

pto

53nF

(44

nF)

L:1

91H

(159

H)

...in

finite

PD

mea

sure

men

ton

Mot

ors

/Gen

erat

ors

L:0

.1m

H...

200

H

C:u

pto

1F

(0.8

8F

)

C:u

pto

1F

(0.8

8F

)

PD

mea

sure

men

ton

Mot

ors

/Gen

erat

ors

C:u

pto

53nF

(44

nF)

L:1

91H

(159

H)

...in

finite

automatic capacitance and power factor field test set 12 kv 2.4 … · 2013-11-22 · xp, the so...

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