Force excitation protection circuit suitable for direct-current injection type rotor grounding protection measurement loop

Abstract

The invention discloses aforce excitation protection circuit suitable for a DC injection type rotor grounding protection measurement loop. The measurement loop comprises an injection DC source connected in series between a rotor large shaft and a rotor negative electrode, at least two resistors, a controllable switch connected in parallel to two ends of one of the resistors, and a diode. The forceexcitation protection circuit comprises a relay K2 and a rotor voltage detection unit. The relay K2 comprises a normally-closed contact which is connected in series in the DC injection type rotor grounding protection measurement loop, and the two ends of a coil of the relay K2 are connected with the rotor voltage detection unit. The rotor voltage detection unit is connected with a rotor positiveelectrode and a rotor negative electrode to detect a rotor voltage, and is communicated with the rotor positive electrode, the rotor negative electrode and a coil of the relay K2 according to a comparison result of the rotor voltage and a set voltage threshold value, so that a rotor winding forms a current loop with the coil of the relay K2 through a rotor voltage judgment unit. According to the invention, when the rotor is forcibly excited and the positive electrode is in metallic grounding, components of the measurement loop are prevented from being damaged by a large current flowing throughthe measurement loop.

Description

technical field [0001] The invention relates to the technical field of generator operation monitoring and protection, in particular to a forced excitation protection circuit suitable for a DC injection type rotor grounding protection measurement circuit. Background technique [0002] As an important part of the generator, the generator rotor winding provides the generator with a rotating rotor magnetic field, cuts the stator winding, and generates electricity. The common fault forms of rotor winding insulation damage are one-point grounding of the rotor winding and two-point grounding of the rotor winding. The grounding fault of one point of the rotor winding does not cause harm to the generator, but if the second point grounding occurs successively, it will cause vibration of the generator. In severe cases, the shafting and turbine may be magnetized, so it is necessary to configure injection or ping-pong rotor grounding protection to protect the rotor from a single groundin...

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Problems solved by technology

[0004] However, there are still some problems with the above protection methods. For example, when the rotor is strongly excited and the positive pole is metallically grounded, a large current will flow through the measurement circuit, which may easily cause the measurement circuit to The components are damaged, but if the circuit parameters are designed according to the maximum strong excitation voltage, the resistance measurement accuracy will be insufficient

[0005]In addition, when the rotor has no ground fault, the measurement circuit has no path, and the rotor leakage current is always zero, so the self-test of the measurement circuit cannot be performed, and the measurement cannot be obtained in time and accurately Whether there is a fault in the circuit, it is easy to cause the protection to refuse to operate when the rotor has a ground fault

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