EFFECTS OF NEUTRAL GROUNDING METHODS ON ELECTRICAL EQUIPMENT AND RELAY PROTECTION OF 473E7 FEEDER, THUA THIEN HUE POWER COMPANY

Abstract

There are different methods of neutral point grounding in medium voltage electric power distribution networks in practice, such as isolated neutral point, direct grounding, low-impedance grounded neutral point, and high-impedance grounded neutral point (Peterson Coil). Each of these methods has advantages and disadvantages, and the decision on the method also depends on the safe, technical and economical point of views. This paper presents brief calculations, analysis, and assessments on the changes of short-circuit current and voltage between the low-resistance grounded neutral point switched to solid grounded neutral point of 473E7 feeder on the networks of Thua Thien Hue Power Company. The impacts of these changes on equipment, relay protection are also analyzed with three-phase and phase-to-ground short-circuit.