Method and device for estimating an angle of a zero sequence voltage when a single phase earth fault occurs in a distribution network. The present invention relates to a method and a device for estimating zero sequence voltage angle (s330) when single phase ground fault occurs in distribution network with decentralized generating devices. The method for estimating zero sequence voltage angles comprises: detecting (s310) angles of respective phase voltages at three phase voltages; determine (s320) a type of neutral grounding of the distribution network; and estimating the zero sequence voltage angle when the single phase earth fault occurs in the distribution network with the detected angles of the respective phase voltages, according to the type of neutral grounding of the network. The zero sequence voltage angle can be estimated with the angles of the three phase voltages provided by the existing vpis without precise magnitudes of the three phase voltages, so that single-phase ground fault detection is simpler and easier, and The cost of ground fault detection device is reduced.
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