| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optimal protection method for an insulation level monitoring device against a ground fault current flowing through a class B ground line. <P>SOLUTION: An insulation level monitoring device includes: a monitoring signal generating circuit 18 that generates a monitoring signal whose frequency is different from a commercial frequency; a monitoring signal injection circuit 15 that injects the monitoring signal into a class B ground line 19 through a transformer 10 for injection; a voltage detection circuit 14 and a switching element 13; a current detection circuit 12 provided between the monitoring signal injection circuit 15 and voltage detection circuit 14; a circuit cutoff relay 11 provided between the voltage detection circuit 14 and transformer 10 for injection; and a control circuit 17 that controls the circuit cutoff relay 11. The insulation level monitoring device has a first protection method in which when the current in the current detection circuit becomes a predetermined value, the circuit is cut off by the circuit cutoff relay 11, and a second protection method in which when the voltage across the voltage detection circuit 14 becomes a predetermined value, the switching element 13 performs an on-operation and the circuit is cut off by the circuit cutoff relay 11. <P>COPYRIGHT: (C)2013,JPO&INPIT |
