| 摘要 |
PROBLEM TO BE SOLVED: To precisely detect, in an operating state, a leak current Igr flowing from a voltage application part of a load device fed from a switching power supply to a grounding part through grounding insulation resistance. SOLUTION: A processing calculation part 16 is equipped with: a signal processing part 3; and a calculation part 14. The signal processing part 3 performs signal processing of one of line voltages E<SB>VU</SB>, E<SB>WV</SB>, E<SB>UW</SB>generated between terminals U, V, W of switching power supply outputs as an input voltage or one of line voltages E<SB>SR</SB>, E<SB>TS</SB>, E<SB>RT</SB>of three-phase distribution lines or a line voltage of single-phase distribution line, and a zero-phase current I<SB>0</SB>detected by a zero-phase current transformer 9 as a vector sum of currents flowing from a distribution power supply to a load device through the switching power supply, and also performs the signal processing by measuring a phase difference between the input voltage and the zero-phase current. The calculation part 14 calculates a phase angleθrelative to the input voltage of the zero-phase current I<SB>0</SB>, calculates active and reactive components A and B to the input voltage on the basis of the phase angleθand the value of the zero-phase current I<SB>0</SB>, and calculates the value of the leak current Igr that is approximate to the sum of respective phases excluding the sound one phase flowing through the ground leak resistances ru, rv, rw on the basis of the root-mean-square value. COPYRIGHT: (C)2011,JPO&INPIT |
