Please help explain the reasons why a 10kV high-voltage metering cabinet was struck by lightning
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This year, our unit’s 10kV high-voltage metering cabinet was struck by lightning twice; in both cases, inspections revealed that the high-voltage fuses inside the cabinet had been burned out. Due to a lack of expertise in the circuits inside the high-voltage cabinet, it is not possible to determine the root cause of the lightning strike. Therefore, I’m not sure what preventive measures should be taken; please advise
The lightning protection measures aren’t properly in place, I guess. . Could it be a problem with the lightning protection grounding or the surge protection device? ?
This post was last edited by zhaohh3211 on 2010-10-29 at 16:55. What is the high-voltage power supply method used by the poster? Is lightning current being introduced into the system?
First, are there any lightning protection measures?； Second, the high-voltage incoming line method ； Third, whether there are any issues with the lightning protection equipment.
Fourth, the metering cabinet is located in front of the arrester
Lightning arrester? Ground resistance? Are all qualified?
Let me explain this to you. I have spent many years researching lightning protection and the issue of explosions caused by PT insurance devices, and I have also consulted numerous experts in this field. In general, wherever overvoltage can occur, lightning protection and overvoltage mitigation measures are necessary. For example, lightning arresters should be used at both ends of cable connections, on the circuit breakers in high-voltage switchgear, as well as on capacitors and PT devices. But have you noticed that the voltage levels vary from one place to another? Capacitors usually use R-type arresters; for instance, the HY5WR-17/45 type has a discharge voltage of 17 KV and a maximum allowable voltage of 45 KV. PT devices use Z-type arresters, while lines use S-type arresters. Enough of the background information – let’s get to your problem. First, check the model of your PT device and the duration for which its fuses have been in use. The allowable overvoltage level for the PT device is very important, as it can cause explosions in both the PT device and its fuses if the voltage exceeds 1.73 times the rated voltage, especially when there is no overload capacity to handle such conditions. Second, check whether there are lightning rods outside the facility and whether there are lightning arresters inside. Also, test the grounding resistance at the grounding points – it should not exceed 4 Ω. It is most important to check whether a harmonic suppressor has been installed on the third PT; the suppressor should be a high-sensitivity resistor – not one with a high resistance value. It must remain at a low resistance level under normal conditions, but turn into a high-resistance element once the voltage rises to a certain level. If all of the above issues are resolved without problems, then it’s a problem with the quality of the insurance.