The invention discloses a selective electric leakage
protection system for a low-
voltage power grid of an underground
coal mine, and relates to an electric leakage
protection system for the underground
coal mine. The
system comprises a selective electric leakage protection addition
DC source method electric leakage detection
system, a zero-sequence power direction type electric leakage detection
system, and a selective electric leakage
protection system. The selective electric leakage protection addition
DC source method electric leakage detection system is provided with an independent DC power supply between a three-phase
power grid and the ground. The zero-sequence power direction type electric leakage detection system judges an electric leakage fault
branch circuit through a zero-sequence
voltage and a zero-sequence current. The selective electric leakage protection system selects a single-
chip microcomputer in the C8051F040 series, and a CAN2.0B controller is integrated in a
chip and has a mode of external
crystal oscillation. A power supply circuit of the system achieves the selective switching-off of an electric leakage circuit through the detection of a zero-sequence current
signal, and the whole power
supply network is not
cut off. The system is reliable in performance, is convenient and effective, is safe and stable, is high in
cost performance, and achieves the optimization of power supply.