Protection device

A protection device comprising:

• a detection circuit that detects an output current value of a current amplifier circuit and outputs a first abnormality detection signal when the output current value is an abnormal current value;
• a maintenance circuit that outputs a second abnormality detection signal continuously for predetermined maintenance time that is started from output timing of the first abnormality detection signal;
• a relay device that cuts connection between the current amplifier circuit and a load from timing that supply of driving voltage is cut and after recovery time that is mechanism cutting delay time;
• a protection mute unit that outputs a mute control signal at timing that the second abnormality detection signal is received;
• a mute circuit that includes function to turn down an input voltage value to the current amplifier circuit at timing that the mute control signal is received;
• and
• a protection relay command unit that cuts supply of the driving voltage at timing that the second abnormality detection signal is received, wherein
• the detection circuit includes
• a load line detection unit that detects abnormality by a current value on a load line based on a power source voltage value of the current amplifier circuit and a resistor value of the load, and
• a pulse response characteristic changing unit that changes pulse response characteristic of abnormality detection operation by the load line detection unit.