The protection of power transformers may be divided intotwo groups: against overloads and against short circuits (whichmay or not involve earth) The main protection of powertransformers is usually performed by differential relays (87)，gas relays installed in the main tank (63) and in the on load tapchanger tank (63C) and safety devices for pressure relief(63VS) On the other hand， usually non-directionalovercurrent relays (51) with inverse or very-inverse timecurves are applied to provide backup Theseovercurrent relays in most cases also have an instantaneousunit (50)保护电力变压器可分为两组：对超载和短路（其中可能或不涉及地球） 。主要保护的权力变压器通常是由差动继电器（ 87 ） ， 气体继电器安装在主坦克（ 63 ） ，并在上载分接开关换罐（ 63C ）及安全装置的减压 （ 63VS ） 。另一方面，通常非定向过流继电器（ 51 ）与逆或非常逆时间曲线的应用提供备份保护。这些过流继电器在大多数情况下，也有瞬间单位（ 50 ） 。Overcurrent and differential relays should be fed byindependent current The operation of any of thepreviously cited relays should trip the circuit breakersresponsible for disconnecting the power In orderto avoid unnecessary outages， these relays should not operateduring magnetizing transients or when overloads are Gas and differential relays are considered selective， so theiroperation usually implies the existence of internal faults in thetransformer and the necessity of Consequently，when they detect a fault they not only send trip signals tocircuit breakers in order to interrupt the fault， but also lockthem open through the lockout relay (86) Since nondirectionalovercurrent relays may operate when the fault isexternal， they only switch circuit breakers to the open positionthrough the operation of an auxiliary relay (94)差动继电器过流和美联储的应独立的电流互感器。这次行动的任何前述继电器应行的断路器负责断开电源变压器。为了以避免不必要的中断，这些继电器不应在磁化瞬态或超载时，是不能容忍的。 天然气和差别继电器被认为是有选择性的，因此其手术通常意味着存在内部故障的变压器和维修的必要性。因此， 当他们发现的故障，他们不仅派出行信号断路器，以中断的故障，而且还锁定他们打开通过锁定继电器（ 86 ） 。自nondirectional 过流继电器操作时可能的故障isexternal ，他们只开关断路器的公开立场通过操作辅助继电器（ 94 ） 。This typical protection scheme is shown in figure Part ofthe previously cited protective devices are supplied with thetransformer (63， 63C， 63VS) and part are installed in panelslocated in the substation control room (87， 51， 86， 94) Moreinformation on these relays and on power transformerprotection systems may be found in [3] 这种典型的保护计划是如图1所示。一部分前述保护装置的供应变压器（ 63 ， 63C ， 63VS ）和部分安装在面板位于变电站控制室（ 87 ， 51 ， 86 ， 94 ） 。更多有关这些继电器和电力变压器保护系统中可以找到[ 3 ] 。
