Foreign substance detection device, electric power transmission device, electric power reception device, and electric power transmission system

A foreign substance detection device comprising:

• a plurality of sensors;
• and
• a detector that repeatedly executes consecutive comparison processes in which individual comparison processes of comparing values for comparison based on output values from the sensors and a threshold value are executed in predetermined order for the plurality of sensors, and that determines presence or absence of a foreign substance based on comparison results of the individual comparison processes,
• wherein in a case in which an excess sensor, among the plurality of sensors, which is a sensor in which the value for comparison exceeds the threshold value is present in one of the consecutive comparison processes, the detector determines that the foreign substance is present when a number of times of excess, which is a number of times at which the value for comparison exceeds the threshold value in the excess sensor reaches a first number of times;
• and in a case in which the excess sensors of which a number is a first count that is more than one are present in one of the consecutive comparison processes, the detector determines that the foreign substance is present when the number of times of excess in each of the excess sensors of which the number is the first count reaches a second number of times, which is less than the first number of times.