Affections of Ground Fault on the Cable and Grounding System in the Large Plants with Long Cpble Interconnections

• Main Authors: Ying-Chang Tzeng, 曾盈昌
• Other Authors: jin-Maun Ho
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/83722025886121400561

碩士 === 中原大學 === 電機工程研究所 === 94 === Abstract In the large plant with long cables interconnection between generator units and switchyard , large current and high voltage will appear on the cable shielding conductors and grounding system during ground fault on switchyard. Form which the cable and equipment may be damaged even hurt personnel. In this thesis , typical plant with the above problems is studied , The circuit model based on electromagnetic transient program/alternative transient program (EMTPATP) is constructed and analyzed for ground fault on the switchyard at transient state and steady state . The ground grids of switchyard and generator units , the phase conductor and shielding conductors of cable and the main transformer of generation unit are all considered in the modal . In which , the cable shielding conductor with cross-transposition-connection and grounded by arrester in the cable-cover-protection unit (CCPU) are detailly considered in the model . The grounded types of neutral points of mantransformers of generator unit and starting transformer include solid-grounded and arrester-grounded type which are considered is the analysis of ground fault . The transient state and steady state currents and voltages distributed on the cable shielding conductors and the grounding points of cable shielding conductors and transformer neutral point on the ground grids can be obtained from the simulation by ATP . Finally , the affections of ground fault on the cable and grounding system are evaluated lased on the simulation results. In which , the damages on the connections and CCPU arresters of cable shielding conductor are surveied and the electromagnetic characteristics of ground grids are further analyzed by a software package, namely, “current distribution electromagnetic grounding and soil structure analysis”(CDEGS). From which ,we can obtain the electromagnetic the distribution of ground potential rises (GPR) , touch voltage ,step voltage and electromagnetic field on the ground surface of ground grids of switchyard and generate unit . Based on the electromagnetic characteristics , their affections on personnel and equipment are assessed . In the whole ,the study results have shown that the personnel and equipments will be danger at switchyard and touch to cable may shielding conductor during ground fault , and the cable may be damaged by large current with several kA and high voltage kV on the shielding conductors if their connection parts are not treated well.