Cable diagnostic testing is predictive in nature, determining the relative degradation level of a cable against it’s newly manufactured condition. It establishes the likelihood that the cable will continue to perform properly at any point in the cables lifetime. For asset managers, assessing aging and the overall condition of service-aged cable systems is instrumental for planning purposes such as determining what needs to be replaced or what upgrade work should be carried out on the network.
Principal cable diagnostic tests include partial discharge (PD), Tan Delta (and variations of Tan Delta), return voltage method (RVM), and isothermal relaxation current (IRC) tests. Tan Delta tests and their variants can be categorised as tests sensitive to global or local problems, whereas PD is a measurement sensitive to local problems only. It should be noted that PD is not detectable in the field as a result of water trees directly. However “Water trees cause electrical trees, which are detectable as a result of system voltage impulses and operational switching surges occurring, or when excessive test voltage levels are applied.” (IEEE 400.2 – 2013)
Megger employs some of the world’s greatest experts in cable test and diagnostics; with such a variety of possible testing and diagnostic methods, Megger can help you determine the appropriate techniques and equipment for your cable assessment needs.