Causes of generator magnetic loss

Synchronous generators in the operation of sudden full or partial loss of excitation is often due to the following reasons:

(1) excitation circuit, excitation device and its power supply failure;

(2) exciter failure;

(3) Rotor loop failure;

(4) false action of magnetic switch;

(5) Misoperation.

What HAPPENS:

(1) send “generator magnetic loss” signal;

(2) Rotor voltage and current are significantly lower than normal values;

(3) the generator stator voltage is usually reduced, and the reactive power meter indicates a negative value;

(4) Active power meter and stator ammeter swing;

Process:

(1) After the loss of magnetic protection action, the automatic switching of excitation mode, reducing active load is ineffective and acting on the trip, according to the accident stop treatment;

(2) If the loss of magnetism is caused by the wrong trip of the magnetic switch, the magnetic switch should be immediately coincided, and the coincidence is unsuccessful, the generator will be disconnected immediately.

(3) If the loss of magnetism is due to the failure of the excitation regulator AVR, the AVR should be immediately switched from the working channel to the standby channel, and the automatic mode is switched to the manual mode of operation;

(4) After the generator loses magnetism and the generator does not trip, the active load should be reduced to 120MW within 1.5min, and the allowable running time after the loss of magnetism is 15min;

(5) If the loss of magnetism causes the generator to oscillate, the generator should be immediately disconnected and shut down, and re-power after the excitation is restored.

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