Protection method for DG grid-connected transformer grounding system

Abstract

The invention discloses a protection method for a DG grid-connected transformer grounding system, comprising the steps of: considering DG capacity and balanced capacity on local load, and selecting a DG grid-connected transformer, namely selecting a primary winding ungrounded transformer or a primary grounded grid-connected transformer winding; choosing the primary grounded grid-connected transformer winding, when system zero-sequence protection sensitivity is reduced through a protection constant value verification to cause the situation that the faults at the tail end of a feeder line cannot be correctly judged, additionally installing a recloser on the grid-connected transformer; and when the primary winding ungrounded transformer is selected, adopting a way of zero-sequence overvoltage warning. By analyzing the induction overvoltage problem caused after introducing the DG, and the matching problem in system protection matching relations, different modes of connection of the grid-connected transformer winding, and corresponding protection schemes are proposed for different DG access conditions; and in facing the condition that the current distribution network protection typical design is not specific to the high degree of permeability of DG access, new effective thoughts and solutions for protection configuration for the DG access are provided by the protection method.

Description

technical field [0001] The invention relates to a protection method for a grounding system of a DG grid-connected transformer, in particular to a grounding method based on a DG grid-connected transformer and selection of related zero-sequence protection schemes. Background technique [0002] Distributed generation (DG) requires protection not only in the event of a short circuit, but also in abnormal operating conditions. Many abnormal conditions are imposed on DG by the system. These abnormal operating conditions include overexcitation, overvoltage, unbalanced currents, frequency anomalies, and shaft torque damage when the system recloses automatically. When the above situation occurs, DG damage or complete generator failure will occur within a few seconds [1-5]. DG damage is a concern for owners. The power supply company is generally concerned about the damage to the power grid equipment after the DG is connected. Appropriate protection configuration and protection sch...

AI Technical Summary

Problems solved by technology

[0004] For many small DGs, dedicated fault feedback current detection is generally not provided

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