Abstract
The Gas-insulated Line (GIL) is a technical equipment that allows power transmission underground at high voltage level. The UHV GIL-overhead hybrid transmission line is an essential way for power transmission in complicated landscapes. Because of the distributed capacitance of the UHV transmission line and the difference of the structure and the electrical parameters between GIL and overhead transmission line, the distance protection based on uniform lumped parameters cannot be applied to this hybrid transmission line directly. In order to overcome the shortcomings, this paper studies and proposes a new principle of distance protection for the UHV GIL-overhead hybrid transmission line based on frequency domain lossless transmission line equation, with the distributed capacitance accounted. Then, the paper presents a setting scheme for this distance protection with the hybrid line parameters considered. Finally, tests are carried out on the Power Systems Computer Aided Design (PSCAD) platform, and the accuracy and reliability of the distance protection method proposed are verified by simulation results.
Highlights
The Gas-insulated Line (GIL) is a power equipment for the electricity transmission at high voltage level, with the conductor kept in the center of the metallic enclosure and SF6 -N2 gas mixture as the insulating medium [1]
Considering that the inductance of GIL is smaller than overhead transmission line, and the capacitance is larger than overhead transmission line, the measured reactance will decrease when a part of overhead line is replaced by GIL
GIL is is smaller than overhead line, and and the the Considering smaller than overhead transmission transmission line, capacitance is larger than overhead transmission line, the measured reactance will decrease when capacitance is larger than overhead transmission line, the measured reactance will decrease when aa part of of overhead line is is replaced replaced by by GIL
Summary
The Gas-insulated Line (GIL) is a power equipment for the electricity transmission at high voltage level, with the conductor kept in the center of the metallic enclosure and SF6 -N2 gas mixture as the insulating medium [1]. High voltage level and distributed capacitive current of the UHV transmission line, the conventional distance protection based on lumped parameters cannot be applied. The electrical parameters of GIL and overhead transmission line are quite different, so the protective zone of the conventional distance protection will change, further causing maloperation in serious cases It is of great practical significance for enhancing the safety and the stability of the power system to study the distance protection algorithm for UHV GIL-overhead hybrid line. Considering the distributed capacitance of the UHV GIL-overhead hybrid line, this paper proposes a distance protection algorithm applicable to this hybrid line, presents a setting scheme with the hybrid line parameters considered and further examines the accuracy of this method through simulation in PSCAD
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