正確保護發電機很重要

　　Proper protection of the generator is crucial

　　如何正確的保護發電機對于發電機可能發生的故障和不正常工作狀態,應根據發電機的容量有選擇地裝設以下保護。

　　How to correctly protect the generator from possible faults and abnormal working conditions? The following protections should be selectively installed according to the capacity of the generator.

　　(1)縱聯差動保護:為定子繞組及其引出線的相間短路保護。

　　(1) Longitudinal differential protection: It is a phase to phase short circuit protection for the stator winding and its outgoing lines.

　　(2)橫聯差動保護:為定子繞組一相匝間短路保護。只有當一相定子繞組有兩個及以上并聯分支而構成兩個或三個中性點引出端時,才裝設該種保護。

　　(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)單相接地保護:為發電機定子繞組的單相接地保護。

　　(3) Single phase grounding protection: provides single-phase grounding protection for the stator winding of the generator.

　　(4)勵磁回路接地保護:為勵磁回路的接地故障保護。

　　(4) Excitation circuit grounding protection: provides grounding fault protection for the excitation circuit.

　　(5)低勵、失磁保護:為防止大型發電機低勵(勵磁電流低于靜穩限所對應的勵磁電流)或失去勵磁(勵磁電流為零)后,從系統中吸收大量無功功率而對系統產生不利影響,100MW及以上容量的發電機都裝設這種保護。

　　(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 below the static stability limit) or loss of excitation (excitation current is zero), generators with a capacity of 100MW and above are equipped with this protection.

　　(6)過負荷保護:發電機長時間超過額定負荷運行時作用于信號的保護。中小型發電機只裝設定子過負荷保護;大型發電機應分別裝設定子過負荷和勵磁繞組過負荷保護。

　　(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.

　　(7)定子繞組過電流保護:當發電機縱差保護范圍外發生短路,而短路元件的保護或斷路器拒絕動作,這種保護作為外部短路的后備,也兼作縱差保護的后備保護。

　　(7) Stator winding overcurrent protection: When a short circuit occurs outside the longitudinal differential protection range of the generator, and the protection of the short-circuit component or the circuit breaker refuses to operate, this protection serves as a backup for external short circuits and also serves as a backup for longitudinal differential protection.

　　?(8)定子繞組過電壓保護:用于防止突然甩去全部負荷后引起定子繞組過電壓,水輪發電機和大型汽輪發電機都裝設過電壓保護,中小型汽輪發電機通常不裝設過電壓保護。

　　(8) Stator winding overvoltage protection: used to prevent stator winding overvoltage caused by sudden shedding of all loads. Both hydro generators and large steam turbine generators are equipped with overvoltage protection, while small and medium-sized steam turbine generators usually do not have overvoltage protection.

　　(9)負序電流保護:電力系統發生不對稱短路或者三相負荷不對稱(如電氣機車、電弧爐等單相負荷的比重太大)時,會使轉子端部、護環內表面等電流密度很大的部位過熱,造成轉子的局部灼傷,因此應裝設負序電流保護。

　　(9) Negative sequence current protection: When an asymmetric short circuit or three-phase load asymmetry occurs in the power system (such as in electric locomotives, arc furnaces, etc. where the proportion of single-phase loads is too high), it can cause overheating in areas with high current density such as the rotor end and the inner surface of the protective ring, resulting in local burns to the rotor. Therefore, negative sequence current protection should be installed.

　　(10)失步保護:反應大型發電機組與系統振蕩過程的失步保護。

　　(10) Out of step protection: It reflects the out of step protection of large generator sets and system oscillation processes.

　　(11)逆功率保護:當汽輪機主汽門誤關閉,或機爐保護動作關閉主汽門而發電機出口斷路器未跳閘時,從電力系統吸收有功功率而造成汽輪機事故,故大型機組要裝設用逆功率繼電器構成的逆功率保護,用于保護汽輪機。

　　(11) Reverse power protection: When the main steam valve of the steam turbine is mistakenly closed, or when the boiler protection action closes the main steam valve but the generator outlet circuit breaker does not trip, it absorbs active power from the power system and causes a steam turbine accident. Therefore, large units need to install reverse power protection composed of reverse power relays to protect the steam turbine.

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