1. Reliability of GIS EHV epoxy insulators: the need and prospects for more stringen. acceptance criteria
- Author
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Braun, J.M., Ford, G.L., Fujimoto, N., Rizzetto, S., and Stone, G.C.
- Subjects
Electric discharges -- Detection ,Electric insulators -- Testing ,Reliability (Engineering) -- Research ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
High reliability of gas insulated switchgear (GIS) is essential. However, more demanding partial discharge (PD) acceptance criteria for GIS insulators are required at the higher voltage classes to maintain these high levels of reliability. In addition to increased operating stresses and greater manufacturing difficulties, fundamental limitations exist which lessen PD detection sensitivity of large physical objects. PD scaling relationships are presented, based on a recently developed theory, which enable prediction of PD magnitude in equivalent defects in different insulators. For example, PD magnitudes of 2 to 5 pC (the current acceptance criterion) in a 138 kV insulator correspond to magnitudes of 0.5 to 1.2 pC for 550 kV insulators, based on certain assumptions. In effect, defects with greater severity would thus be passed in present factory tests for 550 kV insulators. To maintain the high levels of reliability that manufacturers and users alike have come to expect, PD acceptance criteria of 0.5 to 1.0 pC are proposed for 550 kV insulators to obtain a standard of severity equivalent to that in existence at 138 kV. To achieve this level of testing, a number of techniques, including ultra wideband measurements, are proposed to improve present PD detection technology by at least two orders of magnitude. Sensitivities of better than 0.01 pC at up to 400 kV were routinely achieved in a factory-like environment.
- Published
- 1993