Ultra-low frequency insulation withstand voltage test various use methods and precautions
Cable ultra-low voltage withstand test method
1. Remove all electrical equipment connected to the test sample from the test cable.
2. The insulation resistance test was performed on each phase of the test cable using a 10000V megohmmeter, and the test value was recorded.
3. Test voltage peak: Umax = 3Uo, where Uo is the rated operating voltage between the cable conductor to ground or the metal shield. For example: rated voltage is 10KV cable, single-phase rated voltage Uo:
Phase rated voltage Uo:
Uo=10/√3kV
So the test voltage peak is: Umax=3Uo
=3×10/√3kV
=√3×10kV
=17.32kV
4. Test time: 60 minutes.
5. It can be tested by phase separation. When the capacitance value of the test cable is within the load capacity capability of the test equipment, the three-phase core of the test cable can be connected in parallel and the withstand voltage test can be performed at the same time.
6. Connect the test equipment to the test cable using the supplied special flexible connection cable. Close the power supply, set the test frequency, time and voltage, and the overcurrent protection value and overvoltage protection value on the high voltage side, and then start the boost test. The boosting process should closely monitor the high voltage circuit and monitor the test cable for abnormal noise. When the test voltage is raised, the test time is recorded and the test voltage value is read.
7. After the test time is up, the instrument will automatically stop. If no destructive discharge occurs during the test, it is considered to pass the withstand voltage test.
8. In the process of boosting and withstand voltage, if the output waveform is abnormally distorted, and the current is abnormally increased, the voltage is unstable, the sample cable is odorous, smoke or abnormal noise or flashing, etc., the boost should be stopped immediately, after the shutdown find out the reasons. If these phenomena are caused by the weak insulation of the test cable, the pressure test is considered unacceptable. If it is determined that the test cable is due to air humidity or surface contamination, the test cable should be cleaned and dried before testing.
9. During the test, if the cable insulation fault of the non-test product is encountered, the instrument will have over-current protection. After the cause is found, the full-time connection withstand voltage test should be re-executed. It is not allowed to carry out only the “sufficient time†test. The ultra-low frequency withstand voltage test method of large high-voltage generators The operation method of the ultra-low-frequency withstand voltage test of the generator is similar to the operation method of the above cable. The following is a supplementary explanation for different places.
1. This test can be performed during handover, overhaul, partial replacement of windings, and routine testing. The motor is subjected to a withstand voltage test with a 0.1 Hz ultra low frequency, and the defect of the end insulation of the generator is more effective than the power frequency withstand voltage test. The reason is that at the power frequency voltage, since the capacitor current flowing from the wire rod causes a large voltage drop when flowing through the semiconductor antihalation layer outside the insulation, the voltage on the wire rod insulation at the end is reduced. In the case of ultra-low frequency, the capacitance current is greatly reduced, and the voltage drop on the semiconductor antihalation layer is also greatly reduced, so the voltage on the end insulation is high, which is convenient for detecting defects.
2. Connection method: The test should be carried out in phase separation, the test phase is pressurized, and the non-test phase is shorted to ground.
3. According to the requirements of the relevant regulations, the peak value of the test voltage can be determined by the following formula:
Umax=√2βKUo
Where Umax: the peak value (kV) of the test voltage of 0.1 Hz
:: The equivalent coefficient of 0.1Hz and 50Hz voltage, according to the requirements of China's regulations, take 1.2K: usually take 1.3∽1.5, generally take 1.5
Uo: generator stator winding rated voltage (kV), for example: rated voltage is 13.8 kV generator, the ultra-low frequency test voltage peak calculation method is:
Umax=√2×1.2×1.5×13.8≈35.1(kV)
4. Test time according to relevant regulations
5. In the process of pressure resistance, if there is no abnormal sound, smell, smoke and unstable data, it can be considered that the insulation has withstood the test of the test. In order to better understand the insulation, the surface condition of the insulation should be monitored as completely as possible, especially for air-cooled units. Experience has pointed out that appearance monitoring can detect abnormal generator insulation, such as surface corona and discharge, which cannot be reflected by the instrument.
Precautions
1. The booster equipped with this instrument shall not be used for other purposes.
2. Do not disassemble the machine to avoid accidents. If the instrument is faulty, contact our company for repair.
3. After the shutdown, apply the discharge rod to fully discharge the sample, and then disconnect the line.
Umax=√2×1.2×1.5×13.8≈35.1(kV)
4. Test time according to relevant regulations
5. In the process of pressure resistance, if there is no abnormal sound, smell, smoke and unstable data, it can be considered that the insulation has withstood the test of the test. In order to better understand the insulation, the surface condition of the insulation should be monitored as completely as possible, especially for air-cooled units. Experience has pointed out that appearance monitoring can detect abnormal generator insulation, such as surface corona and discharge, which cannot be reflected by the instrument.
Cable ultra-low voltage withstand test method
1. Remove all electrical equipment connected to the test sample from the test cable.
2. The insulation resistance test was performed on each phase of the test cable using a 10000V megohmmeter, and the test value was recorded.
3. Test voltage peak: Umax = 3Uo, where Uo is the rated operating voltage between the cable conductor to ground or the metal shield. For example: rated voltage is 10KV cable, single-phase rated voltage Uo:
Phase rated voltage Uo:
Uo=10/√3kV
So the test voltage peak is: Umax=3Uo
=3×10/√3kV
=√3×10kV
=17.32kV
4. Test time: 60 minutes.
5. It can be tested by phase separation. When the capacitance value of the test cable is within the load capacity capability of the test equipment, the three-phase core of the test cable can be connected in parallel and the withstand voltage test can be performed at the same time.
6. Connect the test equipment to the test cable using the supplied special flexible connection cable. Close the power supply, set the test frequency, time and voltage, and the overcurrent protection value and overvoltage protection value on the high voltage side, and then start the boost test. The boosting process should closely monitor the high voltage circuit and monitor the test cable for abnormal noise. When the test voltage is raised, the test time is recorded and the test voltage value is read.
7. After the test time is up, the instrument will automatically stop. If no destructive discharge occurs during the test, it is considered to pass the withstand voltage test.
8. In the process of boosting and withstand voltage, if the output waveform is abnormally distorted, and the current is abnormally increased, the voltage is unstable, the sample cable is odorous, smoke or abnormal noise or flashing, etc., the boost should be stopped immediately, after the shutdown find out the reasons. If these phenomena are caused by the weak insulation of the test cable, the pressure test is considered unacceptable. If it is determined that the test cable is due to air humidity or surface contamination, the test cable should be cleaned and dried before testing.
9. During the test, if the cable insulation fault of the non-test product is encountered, the instrument will have over-current protection. After the cause is found, the full-time connection withstand voltage test should be re-executed. It is not allowed to carry out only the “sufficient time†test. The ultra-low frequency withstand voltage test method of large high-voltage generators The operation method of the ultra-low-frequency withstand voltage test of the generator is similar to the operation method of the above cable. The following is a supplementary explanation for different places.
1. This test can be performed during handover, overhaul, partial replacement of windings, and routine testing. The motor is subjected to a withstand voltage test with a 0.1 Hz ultra low frequency, and the defect of the end insulation of the generator is more effective than the power frequency withstand voltage test. The reason is that at the power frequency voltage, since the capacitor current flowing from the wire rod causes a large voltage drop when flowing through the semiconductor antihalation layer outside the insulation, the voltage on the wire rod insulation at the end is reduced. In the case of ultra-low frequency, the capacitance current is greatly reduced, and the voltage drop on the semiconductor antihalation layer is also greatly reduced, so the voltage on the end insulation is high, which is convenient for detecting defects.
2. Connection method: The test should be carried out in phase separation, the test phase is pressurized, and the non-test phase is shorted to ground.
3. According to the requirements of the relevant regulations, the peak value of the test voltage can be determined by the following formula:
Umax=√2βKUo
Where Umax: the peak value (kV) of the test voltage of 0.1 Hz
:: The equivalent coefficient of 0.1Hz and 50Hz voltage, according to the requirements of China's regulations, take 1.2K: usually take 1.3∽1.5, generally take 1.5
Uo: generator stator winding rated voltage (kV), for example: rated voltage is 13.8 kV generator, the ultra-low frequency test voltage peak calculation method is:
Umax=√2×1.2×1.5×13.8≈35.1(kV)
4. Test time according to relevant regulations
5. In the process of pressure resistance, if there is no abnormal sound, smell, smoke and unstable data, it can be considered that the insulation has withstood the test of the test. In order to better understand the insulation, the surface condition of the insulation should be monitored as completely as possible, especially for air-cooled units. Experience has pointed out that appearance monitoring can detect abnormal generator insulation, such as surface corona and discharge, which cannot be reflected by the instrument.
Precautions
1. The booster equipped with this instrument shall not be used for other purposes.
2. Do not disassemble the machine to avoid accidents. If the instrument is faulty, contact our company for repair.
3. After the shutdown, apply the discharge rod to fully discharge the sample, and then disconnect the line.
Umax=√2×1.2×1.5×13.8≈35.1(kV)
4. Test time according to relevant regulations
5. In the process of pressure resistance, if there is no abnormal sound, smell, smoke and unstable data, it can be considered that the insulation has withstood the test of the test. In order to better understand the insulation, the surface condition of the insulation should be monitored as completely as possible, especially for air-cooled units. Experience has pointed out that appearance monitoring can detect abnormal generator insulation, such as surface corona and discharge, which cannot be reflected by the instrument.
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