How to use VLF testing equipment to test hv cables?
Comparison Table of Power Cable's Capacitance
Test Regulations
The device is mainly used in the AC voltage withstand test of cables within 35kV. The test voltage and test time of cables with different specifications are determined according to relevant regulations. The contents of the regulations in this respect are basically the same at home and abroad. The following is a summary of the main contents of Q / ED116501-2004 code for rubber and plastic power cable connection and preventive test for users' reference:
1. Test time: 60mins
2. Withstand voltage test voltage of various cables are as follows:
 Rated VoltageUo／U | Acceptance Test Voltage | Preventive Test Voltage | ||
| Times | Voltage (kV) | Times | Voltage (kV) | |
| 1.8/3 | 3Uo | 5 | 3Uo | 5 |
| 3.6/3 | 3Uo | 11 | 3Uo | 11 |
| 6/6 | 3Uo | 18 | 3Uo | 18 |
| 6/10 | 3Uo | 18 | 3Uo | 18 |
| 8.7/10 | 3Uo | 26 | 3Uo | 26 |
| 12/20 | 3Uo | 36 | 3Uo | 36 |
| 21/35 | 3Uo | 63 | 3Uo | 63 |
| 26/35 | 3Uo | 78 | 3Uo | 78 |
Cable testing mothods
1. Removing the electrical equipments connected with test cable.
2. Measuring insulation resistance of each cable phase with a megohm meter,then VLF withstand test can be taken if test cable is considered to be in good condition.
3. Test peak voltage formula: Ｕmax＝3Ｕo, Ｕo: A fixed value of cable phase. For example: A rated voltage 10kV cable, single-phase rated voltage: Ｕo＝10÷ √3 kV＝5.774kV, so the test voltage peak value: Ｕmax＝3Ｕo＝17.32kV.
4. Test time: according to test requirements. For instance: A new cable test should be tested 60 minutes.
5. Each phase test can be measured. Cable test can be synchronously taken after paralleling cable cores of 3-phases if Cable capacitance doesn't exceed the rated capacitance of VLF Tester.
6. Cable test connection according to the method as below 2 figures. Supplying the power, setting the test voltage and test time (The equipment is equipped with overvoltage and overcurrent protection, the frequency is automatically changed according to the capacitance of device under testing) , then start to “Withstand Test”. After a few seconds,the LCD willstart to display test voltage and test time.
7. When test time is up, the instrument will automatically be shutdown. It is considered to be passed the test if there is no damaging discharging.
8. Please stop the equipment immediately if finding the following things during boosting: output waveform distortion abnormally, abnormal increasing strong current, voltage instability, cable peculiar smell/smoke/abnormal noise/flashover. If these phenomena are caused by poor cable insulation, it is considered that the withstand test failed; should be clean and dry handling test materials cable, then testing if determining test cable caused by air humidity or surface dirt and others.
Find more information about RDVLF-80 very low frequency HV Test Set.
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