EARTH FAULT DETECTING DEVICE, AND ELECTRICITY STORAGE SYSTEM

A capacitor (C1) is connected between an output terminal of an impedance element (R1) and an electricity storage unit (3) mounted in a vehicle and insulated from the vehicle chassis. An earth fault determining unit (13) determines that an earth fault has occurred if a detected value based on a peak-to-peak value of a connecting point voltage between the impedance element (R1) and the capacitor (C1) is equal to or less than a first reference value set on the basis of the peak-to-peak value of the connecting point voltage when an insulation resistance (R2) between the electricity storage unit (3) and the vehicle chassis is at the lowest allowable value thereof, and is equal to or greater than a second reference value set on the basis of the peak-to-peak value of the connecting point voltagewhen the electricity storage unit (3) and the vehicle chassis are completely earthed. 电容器(C1)连接在阻抗元件(R1)的输出端子和与车辆的底盘绝缘地搭载于所述车辆的蓄电部(3)之间。接地判定部(13)在基于阻抗元件(R1)和电容器(C1)的连接点电压的峰峰值的检测值为第1基准值以下且第2基准值以上时，判定为发生了接地，其中，该第1基准值是基于蓄电部(3)和车