Factors leading to demagnetization include: rotor winding failure, exciter failure,误tripping of the active demagnetization switch, damage to certain components or circuit failures in the semiconductor excitation system, and human errors, among others.

Magnetic demagnetization of electromagnets primarily manifests in damage to the generator itself and the power system!

Damage to the generator itself:

(1) After the generator lost magnetic flux, the leakage flux at the stator end increased, causing overheating of the components and the end core.

(2) After asynchronous operation, the generator's equivalent reactance decreases from to . Consequently, the added reactive power absorbed from the system causes the stator windings to overheat.

(3) The differential frequency current exhibited by the generator rotor winding results in rated losses within the winding, causing the rotor winding to overheat.

(4) For large direct cooling steam turbine generators, the average asynchronous torque values are low, and the inertial constant is relatively reduced, with the rotor being significantly asymmetric in both longitudinal and transverse axes. Due to these factors, under heavy load conditions, the torque and active power of the demagnetized generator will experience severe fluctuations. This effect is more severe for hydraulic generators.

Damage to the power system:

(1) Following the demagnetization of a generator, the fluctuation of active power and the decrease in system voltage may have caused the loss of synchronization between a neighboring generator operating normally and the system, resulting in system vibration.

(2) The generator's demagnetization results in numerous reactive power shortages within the system. When the system lacks sufficient reactive power reserves, it will lead to a decrease in voltage. In severe cases, it can cause the voltage to collapse and the system to split.

A generator lost magnetism, resulting in a voltage drop. Under the active adjustment of excitation equipment by other generators in the system, their reactive power output will increase. This has led to overcurrent conditions in certain generators, transformers, and transmission lines, potentially triggering backup protection due to overcurrent actions, which has expanded the scope of the fault.