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POTENTIAL
TRANSFORMER TEST SET
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P. T. testing set is meant for determination of PHASE ANGLE ERROR AND RATIO ERROR of Potential Transformer having secondary rated for 110 volts or 110/ 3volts which are intended to be used on 50 Hz. The measurement is on principle of comparison and null indication on magnetic balance bridge.
The basic unit is sensitive magnetic comparator and also it incorporates electronic null detector to facilitate the balance. The reference voltage 110 volts or 63.5 volts obtained from standard potential transformer and in comparison to that the vector length and phase displacement is measured. The ratio error in percentage and phase displacement in minutes are directly compared and indicated on dials.
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The two voltage vectors, one from Standard Potential Transformer and the other from the Potential Transformer under test energies the high permeability magnetic core and then associated windings try to annual the residual magnetism which occurs due to error. The differential vectors will be proportional to phase error and ratio error magnitudes. The Standard Potential Transformer injects proportional voltage in phase and also of controllable value. The control is done by ratio error dial. The injection voltage tries to annual in phase component of differential vectors.
The high resolution quadrature circuit fed from the same standard potential transformer also injects proportional and controllable voltage in quadrature. Due to this injection the quadrature of differential vector is annualed. The phase angle dial controls this magnitude. |
The amount of injection will be proportional to phase error and ratio error and thus two quantities can be measured directly if perfect balance is achieved. The electronic null detector circuit measures the flux value picking up voltage from the balancing magnetic circuit. At perfect balance condition fundamental frequency flux in the comparator is negligible and the null is achieved.
The P.T. Testing Set provides the following ranges:-
PHASE ANGLE ERROR
RATIO ERROR:
0 to ± 20 min. with x 1 range.
0 to ± 0.5 % with x 1 range.
0 to ± 100 min. with x 5 range.
0 to ± 2.5 % with x 5 range.
0 to ± 200 min. with x 20 range.
0 to ± 10.0% with x 20 range.
The set provides the following components:
1. Separate terminals to connect Standard Potential Transformer and Potential Transformer under test.
2. Ratio error and phase angle error calibrated dials.
3. Range selecting switch.
4. Polarity check indicator.
5. Voltmeter to indicate voltage injected.
6. Null detector with sensitivity control.
7. Terminals to connect Burden Box.
8. Power supply to energise electronic null detector.
9. High permeability magnetic core.
10. Secondary voltage selector switch for 110 V. and 63.5 V.
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THE
PT TEST SET REQUIRES THE FOLLOWING ACCESSORIES
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1. STANDARD
POTENTIAL TRANSFORMER
PRIMARY RANGES
: 11 kV / 22 kV / 33 kV or 3V
SECONDARY
: 110 V or 110 3V
BURDEN
: 7.5 VA.
CLASS OF ACCURACY : 0.2 |
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2. P.T. BURDEN BOX
P.T. Burden Box suitable for 110 Volts and 110 3V 50 Hz., power factor 0.8 lagging. Range selection through selector switch. Range 5 VA , 10 VA, 25VA, 50VA & 100 VA.
—do— but range 25 VA , 50 VA , 75 VA , 100 VA , 125 VA , 150 VA , 175 VA &
200 VA.
—do— 25 VA , 50 VA , 75 VA , 100 VA , 150 VA , 200 VA , 250 VA & 300 VA. |
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3. HIGH VOLTAGE INJECTING TRANSFORMER
Voltage injecting transformer unit 230/240 Volts, A.C. 50 Hz., output 0-40 kV suitable for injecting any voltage upto 40,000 Volts with control panel. |
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PHASE SEQUENCE INDICATOR ROTATING DISC TYPE
SUITABLE FOR OPERATION ON 50-500V, 25-60 Hz, A.C. WITH
CONNECTING LEADS. |
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Vibrating read type Frequency Meter 96 mm square flush mounting type or 144 mm square flush mounting type operating voltage 240 Volts or 415 Volts range 45-50-55 Hertz, 13 reeds, mode of indicator is by vibration of reeds
Portable laboratory type Ohms meter is a sensitive self contained battery operated moving coil type instrument. The antiparallax mirror scale and knife edge pointer provide accurate reading. Press to read switch avoids battery drain. An infinity adjusting potentiometer will helps for accurate reading without effecting variation in battery voltage. A zero adjuster is provided on the front. Shunt type Ohms Meter, ranges available 0-25 Ohms, or 0-50 Ohms or 0-100 Ohms or 0-300 Ohms or 500 Ohms or 0-1000 Ohms or 0-2000 Ohms or 0-5000 Ohms.
Details as above, but Series type Ohms meter ranges as above. |
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