Method for detecting disconnection of machine-end PT (potential transformer) loop without being influenced by operation condition of generator

Abstract

The invention relates to a method for detecting disconnection of a machine-end PT (potential transformer) loop without being influenced by operation condition of a generator, and belongs to the technical field of voltage transformer disconnection detection. According to the method, firstly, an external 20Hz injection type low-frequency square wave power supply is coupled to the primary side of a generator through a generator neutral point grounding transformer or a grounding arc suppression coil, and then is converted to the secondary side through a machine-end PT; then, the 20Hz three-phase phase voltage, frequency and interphase voltage of the secondary side of the PT at the generator end of the generator are detected in real time; and finally, the intact condition of the machine-end PT loop is judged according to a detection result. The method for detecting disconnection of a machine-end PT loop of the generatoris not influenced by the operation condition of a unit, effectively eliminates the PT disconnection detection dead zone in the shutdown state of the generator, can quickly judge the generator terminal PT disconnection fault range, improves the equipment defect elimination efficiency, and has very high practicability and popularization and application value.

Description

technical field [0001] The invention belongs to the technical field of disconnection detection of voltage transformers, and in particular relates to a method for detecting disconnection of a PT circuit at a generator end which is not affected by the operating conditions of a generator. Background technique [0002] CN201310007274.9 discloses a method for judging a primary disconnection of a generator terminal voltage transformer, which is characterized in that: the protection device detects the negative sequence voltage (3U2) of the generator terminal voltage transformer (TV), the open triangle fundamental wave zero Sequence voltage (3U0), and zero-sequence voltage (Un0) or zero-sequence current (In0) of generator neutral point, according to the following formula, compare these detection quantities with corresponding fixed values ​​respectively: [0003] Formula 1: Un0<U0.set1 or In0<I0.set1; [0004] Formula 2: 3U2>U2.set2; [0005] Formula 3: 3U0>U0.set2; ...

AI Technical Summary

Problems solved by technology

When the generator is in the shutdown state, idling state, or in some cases, the PT disconnection occurs due to the vibration change of the unit and the change of the ambient temperature during the start-up and shutdown of the generator. Since there is no 50Hz power frequency voltage and current at the generator end, there is a PT disconnection. Line detection dead zone, unable to quickly and effectively detect PT disconnection at the generator end, resulting in failure to start the generator

[0019] 2) The current disconnection detection method at the PT terminal of the generator cannot effectively determine whether the disconnection fault of the PT circuit occurs in the primary circuit or the secondary circuit of the PT, and manual on-site inspection is required step by step, and the efficiency of maintenance personnel to eliminate defects is low

Images