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Over-current relays (OCR) are the most popular protecting devices utilized in 6kV mining grids of open-pitch mines, QuangNinh province, VietNam. Depending on time of operation of OCR, there are many operating mode catergorized as: Instantaneous OCR, Inverse time OCR, Inverse definite minimum time (IDMT) OCR, Very invese relays, Extremely Inverse relays. Nowaday, to give protection against: Phase faults,...
Single phase earth-fault in MV grids usually causes overvoltage that harm to human being and electric equipments. In 6kV mining grids of Vietnam, earth fault which is majority incident accounts 55% to 73% of the total faults. When earth fault occurs many grids’ eco-technical parameters will be affected. Moreover, the overvoltage and earthing current can lead to serious electric shock accidents caused...
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