Megger measures insulation resistance absorption ratio
Measurement steps:
1) Select a megohmmeter: For the test product with a rated voltage below 1KV, a 1000KV megohmmeter should be selected; for a test product with a rated voltage above 1KV, a 2500KV megohmmeter should be selected.
2) First disconnect terminal L and grounding terminal E, and turn the megohmmeter to the rated speed. At this time, the pointer should point at; then short-circuit the L and E terminals, turn the megohmmeter to the rated speed, and the pointer should point at. Points to "0". Otherwise, the megohmmeter is defective and should be replaced or repaired until it is qualified before use.
3) Before the test, the wiring between the tested product and other equipment should be removed and fully discharged. The discharge time for large-capacity tested products should be no less than 2 minutes.
4) Select the correct wiring method according to the surface condition of the test product, pay attention to the wiring should not be too long, and ensure that there is sufficient insulation distance between the wiring and the equipment shell. How to measure insulation resistance absorption ratio with megohmmeter
5) If only the insulation resistance is measured, turn the megohmmeter to about the rated speed, wait for the pointer to stabilize, read the value after 1 minute, and record the insulation resistance value; if the absorption ratio needs to be measured, a knife switch should be connected in series in the circuit Switch, first crank the megohmmeter to the rated speed, close the knife switch, and time at the same time, read the insulation resistance values at 15s and 60s, and then calculate the absorption ratio K.
6) After the measurement is completed, the line terminal wiring should be disconnected first, and then the megohmmeter should be stopped to prevent the test object with a large capacitance from discharging the megohmmeter and damaging the megohmmeter.
7) Use a discharge rod to discharge the electrode of the test product to the ground. In order to reduce discharge sparks, appropriate resistors should be connected in series in the discharge circuit, and the discharge time should be sufficient, generally not less than 2 minutes.
8) Record and organize test data: pay attention to record the name, serial number, nameplate, operating position of the equipment, insulation temperature, ambient temperature, insulation resistance and absorption ratio of the test product.
Attached, the difference between the methods of measuring insulation absorption ratio and measuring insulation resistance
Procedure for measuring the insulation resistance absorption ratio of a transformer:
1) Remove the primary and secondary busbars or wires of the transformer;
2) Wipe the high and low voltage porcelain bushings clean and check the megger correctly;
3) Correct wiring according to the requirements of the telemetry project;
4) Two people operate, one person turns the handle of the megohmmeter, and the other person holds the insulated part of the test line at the "L" end, turns the megohmmeter to: 120r/min, and the pointer points to ∞;
5) Touch the "L" test wire firmly to the terminal of the transformer, read one number (R15) at 15s, read another number (R60) at 60s, and record the shake measurement data;
6) Read the value after the meter needle is basically stable, first withdraw the "L" measuring line and then stop shaking the megohmmeter;
7) Use a discharge rod to discharge the transformer winding to the ground before and after shaking measurement (the transformer is an inductive load);
8) Record the transformer temperature;
9) Shake test another item;
10) After the shaking test work is completed, remove the interphase short-circuit wires and restore them to their original state.
11) The measured R60 is the insulation resistance of the transformer; the result of R60/R15 (R60 divided by R15) is the absorption ratio of the transformer.
