Electric wire protection device

An electric wire protection device comprising:

• a pyrotechnic cutoff switch, provided partway along an electric wire connecting a load to a vehicle-mounted power supply connected to a reference potential, the pyrotechnic cutoff switch including a conductive part that conducts current between the vehicle-mounted power supply and the load, a cutting blade that cuts the conductive part, a drive part that propels the cutting blade in a direction that cuts the conductive part using the explosive power of gunpowder, and two terminals that input and output current that drives the drive part;
• a conductive wire, one end of the conductive wire being connected to the electric wire and another end of the conductive wire being connected to one of the terminals;
• a diode, an anode of the diode being connected to the reference potential and a cathode of the diode being connected to the other of the terminals;
• a switch, one end of the switch being connected to the other of the terminals and another end of the switch being connected to the reference potential;
• a control unit that opens and closes the switch;
• a current detecting unit that detects current flowing in the electric wire;
• and
• a temperature detecting unit that detects a surrounding temperature,
• wherein the control unit:
• includes a temperature calculating unit that calculates a temperature of the electric wire on the basis of the value of the current detected by the current detecting unit and the surrounding temperature detected by the temperature detecting unit;
• and
• a comparing unit that compares the temperature calculated by the temperature calculating unit with a threshold, and wherein the control unit closes the switch in the case where the temperature is greater than or equal to the threshold;
• a timer unit that measures a time for which current flows in the electric wire;
• a remaining lifespan calculating unit that calculates a remaining lifespan of the electric wire on the basis of the temperature calculated by the temperature calculating unit and the time measured by the timer unit;
• and
• a remaining lifespan communicating unit that communicates information based on a length of the remaining lifespan calculated by the remaining lifespan calculating unit.