Increasing installation of transmission facilities underground has led utilities to place greater emphasis on the qualification, acceptance and maintenance testing of high voltage cables. In particular, there is an urgent need for more searching probes of latent defects than are presently furnished by high voltage (AC or DC) withstand testing. As an alternative to this type of test, partial discharge (PD) testing can provide information on the existence of those latent defects known to cause premature in-service failure of high voltage cables. However, in order to realize the benefits of PD testing, the measurement system must be sufficiently sensitive, which implies for field testing, a high noise rejection capability. The present work addresses these key issues in designing a credible PD test for transmission class cables. The major noise sources are identified and methods to counter them are described.
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