The invention discloses an insulating detection device for a direct-current power supply, which comprises an insulating detection circuit, an earthing
abnormality detection circuit and a
voltage adopting circuit, wherein the insulating detection circuit comprises a first detection
branch circuit, a second detection
branch circuit and a first earth wire K1; the earthing
abnormality detection circuit comprises a third detection
resistor R3, a fourth detection
resistor R4, a third switch S3 and a second earth wire K2; and the
voltage sample circuit is used for measuring
voltage of two ends of the third detection
resistor R3 or the fourth detection resistor R4. The invention also discloses an earthing
abnormality detection method and an insulating detection method adopting the insulating detection device for the direct-current power supply. By adopting the device and method disclosed by the invention, no matter whether the
signal earth of the insulating detection device for the direct-current power supply in a suspension state or a fixed potential state, the abnormal condition of the earth wire can be accurately detected; and furthermore, a unilateral
branch circuit insulating detection method is provided, so that the insulating detection accuracy is improved and the
polling time is shortened.