Study On The Asynchronous Self-Excitation Protection For Generators

Asynchronous self-excitation will occur in synchronous generator if the capacitive load is too large, which will result in overvoltage, overcurrent, electromagnetic torque, and even the destructive transient torque. All of these will cause fatal damage to the synchronous generator and the electric devices, so it is of great importance to find an approach to prevent the generator from such kind of damage. Through the analysis of phenomenon of asynchronous self-excitation which occurred in DATANG TUOKETUO power plant via mounting the block filter, the basic reason which causes the asynchronous self-excitation is found out, and an effective solution-a protective device that can prevent the damage from asynchronous self-excitation is studied in this thesis.Through the deliberation on the principle behind the asynchronous self-excitation, the physical process of asynchronous self-excitation has been studied from the standpoint of parametric resonance, in addition the factors of asynchronous self-excitation occurring has also been analyzed. Based on further analysis, a protection principle which can prevent the damage from asynchronous self-excitation is presented and the modal current which can be acquired from generator stator current is selected as the core reference electric value. An effective filter to extract the modal current is proposed as well. On this basis, the proposed algorithm has been implemented by using the graphical program method which is composed by function blocks on the standard IEC61131-3, and the protective device's hardware has been assembled by the method of hardware configuration. Thus, a set of asynchronous self-excitation system is developed which can be applied in practical engineering. Finally, according to the field tests and RTDS simulation experiment, the validity of the protection method is verified.