Electric wire protection device

An electric wire protection device comprising:

• a voltage adjuster that adjusts voltage on a power source side to be supplied to a load;
• and
• a controller that includes a temperature calculation part which calculates temperature information of an electric wire which connects a power source with the load based on a current value flowing through the voltage adjuster, and that is configured to cause the voltage adjuster to be in an interrupted state to interrupt connection between the power source and the load based on the temperature information, wherein
• the controller is configured to set a first time constant as a time constant which is used to calculate the temperature information while the voltage adjuster is in the interrupted state, and to set a second time constant as a time constant which is used to calculate the temperature information while the voltage adjuster supplies power to the load,
• the first time constant has a value larger than the second time constant and equal to or larger than an actual time constant of the electric wire, and
• the second time constant has a value smaller than the actual time constant of the electric wire.