| 摘要 |
PURPOSE:To measure insulation resistance in a hot-line conditions irrespectively of suspension capacity, by seeking amplitude of a noneffective component automatically and making out a compensating signal matching the magnitude. CONSTITUTION:Leak currents are obtained from a ZCT and a buffer amplifier BA, and a voltage V2sin(omega0t) is obtained from a transformer TRO. Phase of an output of the TRO is shifted by 90 deg. by a PS to become V2cos(omega0t). It is further converted to -V2cos(omega0t) by a polarity inversion circuit INV. An output of a multiplier MULT1 is converted to D=omega0CV0V2/2 through a low-pass filter LPF1, multiplied by 2/V2<2> by a coefficient calculator CF and added to an MULT3. At this MULT3, a signal matching an output -omega0CV0cos(omega0t) is obtained and the signal is added to an adder ADD. By multiplying outputs of the ADD and the TRO by the MULT2 and obtaining a current portion thereof by an LPF2, a value of V0V2/R which is inversely proportional to an insulation resistance is obtained. |
