الفهرس يوجد فقط 14 صفحة متاحة للعرض العام
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المستخلص
The thesis aims to investigate the earthing system in electrical power networks. The earthing system differs in its philosophies and operation according to the required performance of electrical network during abnormal conditions. The selection criteria involve many aspects: Technical Characteristics (system function, overvoltage, fault current, etc.), operation (service continuity, maintenance), safety, cost (maintenance and operating expenses) and local & national customs. In particular, there are two major technical considerations, which are, in fact contradictory: Reducing the level of overvoltage versus the earth fault current. This thesis aims to analyze the two considerations throughout different methods of earthing.
The thesis also emphasis to resonant - earthed system which is suitable to the general system under study (transmission line), it quantifies the transient and steady-state phase-to-earth and phase¬to-phase over-voltages that arise on a resonant -earthed system under normal and fault conditions using computer software called (EMTDC). The studies involve simulations of small 6.6 kV generic system and also one industrial power system in one of the Egyptian petroleum companies. The resonant earthed system is taken as the suitable earthed method.
Chapter (1) explains the motivation behind earthing system in electrical power networks with a brief history about its development.
Chapter (2) introduces a review of the different methods of treating the system neutral. The advantages and disadvantages of each method include the steady state and transient performance of the different earthing system under a single-phase-to-earth fault, which are investigated by carrying out simulations on a simple 6.6kV system.
Chapter (3) introduces the steady state and transient performances of a resonant-earthing system under a single-phase-to-earth fault. This case is investigated and compared with that of an unearthed system. The transient studies consider both arcing and solid earth-fault conditions.
Chapter (4) introduces the network performances under phase-to-earth fault, which passes through resistance (tree fault) at a resonant-earthed system. Quantifying the neutral and phase voltages with respect to earth investigate the effect of fault resistance. Also the effect of fault resistance in case of off-resonance (over-under compensation) is quantified.