How to Use an Insulation Resistance Tester
The insulation resistance meter, commonly known as a megger, is an insulation resistance testing instrument powered by a hand-cranked generator. Currently, most use a power supply type, and its external structure is shown in Figure 9-12. The usage method is as follows:
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Figure Insulation resistance meter
(1) Cut off the power supply of the device under test and ground it for discharge.
(2) Calibrate the meter. Calibration should be done in two steps: first calibrate the zero point, then calibrate the full scale.
Calibrate zero point: Short-circuit the line and ground terminals; the needle should immediately point to zero, indicating that the meter's performance is normal and the zero reading is correct.
Calibrate full scale: After separating the line and ground terminals, the needle points to infinity, indicating that the infinity reading of the meter is normal.
Specific method;
1. Preparation
Insulation resistance tester Before wiring, first turn the 'Power Switch' to the off position, and the 'High Voltage Control' button should be released! The object under test must be disconnected from the power grid, and all terminals under test must be connected to the ground through an artificial discharge rod. Only after proving safety can wiring be done!
Especially for objects under test in substations and power plants that are strongly interfered by grid leakage induction, multiple artificial discharge rods connected to the ground should be properly connected to all line terminals under test in advance to avoid electric shock to wiring personnel. After the wiring of this meter is completed, remove the artificial discharge rods from the terminals under test.
2. Wiring:
Connect the two 'E' terminals of the meter to the ground or neutral terminal of the object under test, and to the earth.
Connect the 'L' terminal of the meter to the line terminal under test, such as transformer windings or cable cores.
Connect the 'G' terminal of the meter to the guard ring that needs to eliminate the influence of surface resistance leakage in the circuit under test.
3. Preselect the test power supply voltage:
Turn the 'High Voltage Preselection' rotary switch to the desired test power supply voltage. If you need to start from 0V, turn the 'High Voltage Adjustment' knob counterclockwise to the end.
4. Turn on the working power supply:
Turn the 'Power Switch' of this meter to the on position, the indicator light above the switch will light up, and the 'kV' voltmeter should display 0.00kV.
5. Test start:
Press the 'High Voltage Control' button, then high voltage is output from the L terminal, the 'kV' meter displays the voltage value between L-E, and the 'stopwatch' starts timing.
6. Fine adjustment of test power supply voltage:
Adjust the 'High Voltage Adjustment' knob to smoothly adjust the voltage to the specified value.
7. Resistance range selection:
Turn the resistance range switch to the desired range, or step from the MΩ range up to the 200GΩ range. If the meter continuously alarms, it indicates that the measured resistance is too low, and you should switch to a lower range for measurement.
8. Reading:
After the reading stabilizes, read the resistance value from the display. For analog meters, read the value on the dial according to the selected range.
9. After the test:
First press the 'High Voltage Control' button to release it, then turn off the 'Power Switch'. Discharge the object under test with an artificial discharge rod before disconnecting the wires.
10. Precautions:
(1) During the test, do not touch the test leads and the object under test to avoid electric shock.
(2) When testing large capacitance equipment, discharge it fully before and after the test.
(3) The test leads should be well insulated and not twisted together to avoid measurement errors.
(4) The meter should be placed on a stable and level surface, away from strong magnetic fields.
(5) If the meter is not used for a long time, remove the battery to prevent leakage and damage.
11. Maintenance:
Keep the meter clean and dry, and avoid dust and moisture. If the meter is damaged, it should be repaired by professionals.
12. Common faults and troubleshooting:
(1) The power indicator does not light up: check whether the power cord is connected properly and whether the fuse is blown.
(2) The voltage cannot be adjusted: check whether the high voltage adjustment knob is damaged or whether the internal circuit is faulty.
(3) The reading is unstable: check whether the test leads are in good contact and whether the object under test is well grounded.
(4) The meter alarms continuously: check whether the measured resistance is too low or whether the range selection is incorrect.
13. Technical parameters:
(1) Test voltage: 100V, 250V, 500V, 1000V, 2500V, 5000V, etc.
(2) Resistance range: 0-200GΩ.
(3) Accuracy: ±5% of reading.
(4) Power supply: AC 220V or DC 12V.
14. Notes:
(1) Before use, read the instruction manual carefully and understand the operation methods and precautions.
(2) During the test, strictly follow the steps to avoid damage to the meter or personal injury.
(3) If any abnormality is found, stop the test immediately and check the cause.
15. Storage:
Store the meter in a dry, ventilated place, avoiding high temperature, humidity, and corrosive gases.
16. After-sales service:
If the meter has quality problems within the warranty period, it can be repaired free of charge. For details, please contact the manufacturer.
17. Contact information:
If you have any questions, please contact our technical support team. We will be happy to serve you.
18. Copyright notice:
The copyright of this manual belongs to the manufacturer. No part may be reproduced without permission.
19. Version history:
V1.0 (2020-01-01): Initial release.
20. Disclaimer:
The manufacturer is not responsible for any loss or damage caused by improper use of the meter.
21. References:
[1] GB/T 18216.1-2012, Insulation resistance testing equipment.
[2] IEC 61010-1:2010, Safety requirements for electrical equipment for measurement, control, and laboratory use.
22. Appendix:
Appendix A: Wiring diagram.
Appendix B: Troubleshooting flowchart.
23. Contact us:
Address: No. 123, Changjiang Road, High-tech Zone, Hefei City, Anhui Province, China.
Tel: +86-551-12345678
Email: service@yzdr2.com
24. Website:
For more information, please visit our website: www.yzdr2.com
25. Thank you for choosing our product. We look forward to providing you with quality service.
26. Note: The content of this manual is subject to change without prior notice. The final interpretation right belongs to the manufacturer.
27. End of manual.
