Section 1 General Rules

Norms of acceptance tests. Measuring voltage transformers

Encyclopedia of radio electronics and electrical engineering / Rules for the installation of electrical installations (PUE)

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1.8.18. 1. Electromagnetic voltage transformers.

1.1. Measurement of winding insulation resistance.

The insulation resistance of the HV winding of voltage transformers is measured with a megohmmeter for a voltage of 2500 V.

The insulation resistance of the secondary windings, as well as the connecting windings of cascade voltage transformers, is measured with a megohmmeter for a voltage of 1000 V.

The measured insulation resistance values ​​must be no less than those given in table. 1.8.15.

1.2. Test with increased voltage frequency 50 Hz.

Testing the insulation of the HV winding with increased voltage at a frequency of 50 Hz is carried out for voltage transformers with insulation of all terminals of the HV winding of these transformers at the rated voltage.

The values ​​​​of the test voltage of the main insulation are given in table. 1.8.15.

Duration of testing of voltage transformers - 1 min.

The value of the test voltage for insulating the secondary windings together with the circuits connected to them is assumed to be 1 kV.

The duration of the test voltage application is 1 min.

1.3. Measurement of winding resistance to direct current.

The DC winding resistance is measured at the connecting windings of cascade voltage transformers.

The deviation of the measured DC winding resistance from the rated value or from that measured on other phases should not exceed 2%. When comparing the measured value with the nameplate data, the measured resistance value must be reduced to the factory test temperature. When comparing with other phases, measurements on all phases must be carried out at the same temperature.

1.4. Testing of transformer oil.

When commissioning voltage transformers, the oil must be tested in accordance with the requirements of Table 1.8.32, paragraphs 1-6.

For oil-filled cascade voltage transformers, the condition of the oil in individual stages is assessed according to standards corresponding to the operating voltage of the stage.

2. Capacitive voltage transformers.

2.1. Testing capacitors of voltage dividers.

Voltage divider capacitors are tested in accordance with the requirements of Section 1.8.27.

2.2. Measuring the insulation resistance of an electromagnetic device.

The measurement of the insulation resistance of the windings is carried out with a megohmmeter for 2500 V.

The insulation resistance should not differ from that indicated in the passport by more than 30% for the worse, but be at least 300 MOhm.

2.3. Testing an electromagnetic device with increased voltage at a frequency of 50 Hz.

The insulation of the secondary windings of the electromagnetic device is subjected to tests.

Test voltage - 1,8 kV.

Duration of voltage application - 1 min.

2.4. Measurement of winding resistance to direct current.

During commissioning, the DC winding resistance is measured at all positions of the switching device.

The measured values, normalized to temperature during factory tests, should not differ from those indicated in the passport by more than 5%.

2.5. Measurement of current and no-load losses.

Current and no-load losses are measured at voltages specified in the factory documentation.

The measured values ​​should not differ from those indicated in the passport by more than 10%.

2.6. Testing transformer oil from an electromagnetic device.

The value of the breakdown voltage of the oil must be at least 30 kV.

When commissioning, fresh dry transformer oil for filling (topping up) the electromagnetic device must be tested in accordance with the requirements of Table 1.8.33, paragraphs 1-6.

2.7. Testing valve arresters.

Carried out according to the instructions of section 1.8.31.

Table 1.8.15. Insulation resistance of voltage transformers

* Insulation resistances of the secondary windings are given:

• without brackets - when secondary circuits are off;
• in brackets - together with connected secondary circuits.

See other articles Section Rules for the installation of electrical installations (PUE).

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