To measure the insulation resistance of a 10kv transformer, a 2500v megohmmeter should be used.
Qualification standards for insulation resistance
1. Comparing the insulation resistance value of this remote measurement with the last value when converted to the same temperature, this value must not be lower than the last value by 30%.
2. The absorption ratio R60/R15 (that is, focusing on the ratio of insulation resistance at 60 seconds and 15 seconds) should be more than 1.3 times at 10℃-30℃
3. The qualified values of insulation resistance of 3-10kv transformer at different temperatures are as follows:
| temperature(℃) | 10 | 20 | 30 | 40 | 50 | 60 | 70 | 80 |
| good value(MΩ) | 900 | 450 | 225 | 120 | 64 | 36 | 19 | 12 |
| lowest value(MΩ) | 600 | 300 | 150 | 80 | 43 | 24 | 13 | 8 |
Telemetry projects
1 The insulation resistance of high-voltage winding to low-voltage winding and shell is referred to as high-to-low and ground.
2 The insulation resistance of the low-voltage winding to the high-voltage winding and shell is referred to as low to high and ground.
Measurement process
1. Remove the remote-measured transformer from operation, and implement technical safety measures such as power outage, power inspection, discharge, installation of temporary grounding wires, and hanging signs.
2. Remove the high and low voltage busbars of the transformer.
3. Wipe the high and low voltage porcelain bushings of the transformer clean, then wind 2-3 turns around the porcelain skirt of each porcelain bushing with bare copper wire to connect the high and low voltage porcelain bushings respectively.
4. Short-circuit the high-voltage A, B, C (U, V, W) and low-voltage 0, a, b, c (n, u, v, w) terminals of the transformer with bare copper wires.
5 Remotely measure the high-voltage winding and the low-voltage winding and shell. The E of the megohmmeter is connected to the low-voltage winding and shell, G is connected to the porcelain skirt of the high-voltage winding porcelain bushing, and L is connected to the high-voltage winding.
6 Remotely measure the low-voltage winding and the high-voltage winding and shell. The E of the megohmmeter is connected to the high-voltage winding and shell, G is connected to the porcelain skirt of the low-voltage porcelain bushing, and L is connected to the low-voltage winding.
7. During telemetry, first connect E and G to the object being measured, use an insulator to pick up the L line, and when the megohmmeter reaches 120 revolutions per minute, connect the L line to the high-voltage winding (low-voltage winding). , the meter is placed horizontally during telemetry, and telemetry is performed at a constant speed of 120 rpm. Wait for the needle to stabilize for one minute before taking a reading, remove the L line, and then stop rocking the meter.
8. The winding should be discharged to the ground before and after telemetry. After the telemetry is completed, remove the phase-to-phase short circuit and restore the original wiring.