Functional Characteristics of Generator Low Excitation Limits
The generator's low excitation limit is used to prevent the excitation level from being too low to threaten the safety of the unit itself and the system.
There will be a low level of excitation in the generator operation:
(1) power grid in the low load period, the conventional inductive reactive power compensation equipment input is insufficient when there is a high voltage problem, this time to take the generator to reduce the excitation phase of the regulator operation;
(2) the system due to disturbance or fault voltage suddenly rises, the generator excitation regulator will automatically respond to reduce the excitation;
(3) excitation regulator failure caused by lower excitation level.
There are several problems with the generator working in the low excitation area. First, the heat generation of the generator stator core increases significantly due to the increase of the magnetic flux leakage, so that the temperature may rise beyond the maximum allowable value. Secondly, Deep, the excitation current is too small, it is possible to achieve the system static stability limit, the occurrence of stable damage accident; in addition to increase the possibility of loss of magnetic protection malfunction. As an important auxiliary function of the generator excitation control system, the low-limit limiter, also known as the under-excitation limiter, is proposed for the above-mentioned problem. When the low-excitation limiter detects that the excitation level of the unit is reduced to the action value, Large excitation to the unit operating point back to allow the scope to improve the safety of the unit and the system.