AC testing

[eejacky]

Dear all experts,

I heard that the present equipment used to perform AC testing for power cable (132kV or 400kV) have a specified capacitance tolerance such as 40pF. Why AC testing is not preferable for LONG cable length?


Thank you!

 

[DanDel]

I am not familiar with test equipment for 132kV or 400kV cables, but AC hipotential testing of long cables is usually not possible due to the reactive component of the cable which limits the test voltage. A DC test does not have this problem. Some AC testing can be accomplished using a resonant inductor to compensate for the capacitance of the cable(typically used with Doble PF test equipment). I'm not sure if any of this applies to your situation.

 

[RRaghunath]

Eejacky,

HV testing using AC power supplies requires that the kit shall have enough kVA capacity to supply the cable capacitance charging currents. These currents are directly proportional to the length of the cable and also on the pu capacitance (which indirectly depends on the voltage rating) of the cable. This imposes restrictions on the test.

In other words, higher the voltage rating of the cable / longer the cable we need to go in for bigger size test equipment.