For possible faults and abnormal working conditions of the generator, the following protections should be selectively installed according to the capacity of the generator.
(1) Longitudinal differential protection: It is a phase to phase short circuit protection for the stator winding and its outgoing lines.
(2) Horizontal differential protection: It is used for short circuit protection between one phase and one turn of the stator winding. This type of protection is only installed when a phase stator winding has two or more parallel branches forming two or three neutral point terminals.
(3) Single phase grounding protection: provides single-phase grounding protection for the stator winding of the generator.
(4) Excitation circuit grounding protection: provides grounding fault protection for the excitation circuit.
(5) Low excitation and demagnetization protection: To prevent large generators from absorbing a large amount of reactive power from the system and causing adverse effects after low excitation (excitation current lower than the excitation current corresponding to the static stability limit) or loss of excitation (excitation current zero), generators with a capacity of 100MW and above are equipped with this protection.
(6) Overload protection: The protection applied to the signal when the generator operates beyond its rated load for a long time. Small and medium-sized generators are only equipped with set sub overload protection; Large generators should be equipped with stator overload and excitation winding overload protection separately.
