Insulation monitoring device

An insulation monitoring device that detects leakage current flowing back via a ground insulation resistor of a power system or load apparatus connected to the power system, calculates from the leakage current a resistance component current of a same phase as a reference voltage superimposed on the power system, and detects an insulation failure caused by a decrease in a ground insulation resistance when the resistance component current exceeds a monitoring setting value, the insulation monitoring device configured to monitor the power system to which a noise filter including a capacitor is connected when the load apparatus operates, the insulation monitoring device comprising:

• an operated quantity acquisition unit that acquires an operated quantity of the load apparatus;
• and
• a monitoring setting value computing unit that computes the monitoring setting value using a unit setting value of one load apparatus, the operated quantity, and a base setting value in accordance with a resistance component error current flowing in accordance with a ground insulation capacitance of the power system, wherein
• the insulation monitoring device is configured to use the monitoring setting value computed by the monitoring setting value computing unit in a comparison with the resistance component current to detect insulation failure.

An insulation monitoring device that detects leakage current flowing back via a ground insulation resistor of a power system or load apparatus connected to the power system, calculates from the leakage current a resistance component current of a same phase as a reference voltage of the power system, and detects an insulation failure caused by a decrease in a ground insulation resistance when the resistance component current exceeds a monitoring setting value, the insulation monitoring device configured to monitor the power system to which a noise filter including a capacitor is connected when the load apparatus operates, the insulation monitoring device comprising:

• a capacitance component current extraction unit that extracts a capacitance component current whose phase is further advanced than that of the resistance component current from a current with the same frequency component as a supervisory signal;
• and
• a monitoring setting value computing unit that computes the monitoring setting value using the capacitance component current extracted by the capacitance component current extraction unit, a unit setting value of a unit capacitance component current or unit electrical capacitance, and a base setting value in accordance with a resistance component error current flowing in accordance with a ground insulation capacitance of the power system, wherein
• the insulation monitoring device is configured to use the monitoring setting value computed by the monitoring setting value computing unit in a comparison with the resistance component current to detect insulation failure.

An insulation monitoring device that detects leakage current flowing back via a ground insulation resistor of a power system or load apparatus connected to the power system, calculates from the leakage current a resistance component current of a same phase as a reference voltage of the power system, and detects an insulation failure caused by a decrease in a ground insulation resistance when the resistance component current exceeds a monitoring setting value, the insulation monitoring device configured to monitor the power system to which a noise filter including a capacitor is connected when the load apparatus operates, the insulation monitoring device comprising:

• a capacitance component current extraction unit that extracts a capacitance component current whose phase is further advanced than that of the resistance component current from a current with a same frequency component as a supervisory signal;
• an electrical capacitance conversion unit that converts the capacitance component current extracted by the capacitance component current extraction unit into electrical capacitance;
• a temperature correction computing unit that corrects the electrical capacitance converted by the electrical capacitance conversion unit using an electrical capacitance rate of change in accordance with a type of the capacitor and an ambient temperature measurement value;
• and
• a monitoring setting value computing unit that computes the monitoring setting value using a resistance component error current that flows in accordance with the electrical capacitance corrected by the temperature correction computing unit and a base setting value in accordance with a resistance component error current flowing in accordance with a ground insulation capacitance of the power system, wherein
• the insulation monitoring device is configured to use the monitoring setting value computed by the monitoring setting value computing unit in a comparison with the resistance component current to detect insulation failure.