NETA 7.3.3

[ee84]

I have a question on NETA 7.3.3 interpretation and on some of the testing methods listed. It states in 7.3.3 B.2,

Perform an insulation-resistance test individually on each conductor and each shield with all other conductors and shields grounded. Apply voltage in accordance with manufacturer’s published data. In the absence of manufacturer’s data, use Table 100.1.

It does not state by which method, is stated somewhere in the standard? Is megger the only option? Megger is not referenced in the standard. It states to perform on each conductor with all other conductors and shields grounded. This to me implies it is referencing a multi conductor cable. In a typical medium voltage application in power plants, each phase is a separate conductor. So does this statement apply in the case of a solar power plant where each phase conductor is laid out separately?

It later states in 7.3.3.B.5 several different testing methods for diaelectric withstand and baseline diagnostics test, where DC insulation is listed under the latter. These are the possible tests that can be performed. Does the VLF tan delta test provide information on the outer jacket? A third-party indicated that the VLF tan delta or VLF tests only tests the inner insulation, and do not evaluate the conditions of the outer jacket. Is this true? Any references are appreciated.

 

[MrJLH]

Take a look at IEEE 400.2 Guide for Field Testing of Shielded Power Cable Systems Using Very Low Frequency (VLF)

"Megger" is a name of a manufacturer of test equipment.