tool PCM600. The inputs Qx_EXy on the interlocking modules are used to add thesespecific conditions.The input signals EXDU_xx shall be set to true if there is no transmission error at thetransfer of information from other bays. Required signals with designations ending inTR are intended for transfer to other bays.12.3 Voltage control12.3.1 FunctionalityAutomatic voltage control for tap changer TR8ATCC and Tap changer control andsupervision, 6 binary inputs TCMYLTC are used for control of power transformerswith a on-load tap changer. The functions provide automatic regulation of the voltageon the secondary side of transformers or alternatively on a load point further out in thenetwork.Control of a single transformer, as well as control of up to two transformers within asingle RET650, or parallel control of up to four transformers in two or even fourseparate RET650 is possible. Note that the last alternative is achieved by using theGOOSE interbay communication on the IEC 61850-8-1 protocol. For parallel controlof power transformers, three alternative methods are available, the master-followermethod, the circulating current method and the reverse reactance method.Voltage control includes many extra features such as possibility of to avoidsimultaneous tapping of parallel transformers, extensive tap changer monitoringincluding contact wear and hunting detection, monitoring of the power flow in thetransformer so that for example, the voltage control can be blocked if the powerreverses etc.In manual operating mode it is possible to give raise- or lower-commands to the loadtap changer from the local HMI. Such facilities are pre-defined in the factory.The Automatic voltage control for tap changer TR8ATCC function controls thevoltage on the LV side of a transformer either automatically or manually. Theautomatic control can be either for a single transformer, or for a group of paralleltransformers.The Tap changer control and supervision, 6 binary inputs (TCMYLTC) gives the tapcommands to the tap changer, and supervises that commands are carried throughcorrectly. It has built-in extensive possibilities for tap changer position measurement,as well as supervisory and monitoring features. This is used in the voltage control andcan also give information about tap position to the transformer differential protection.12.3.2 Automatic voltage control for tapchanger, parallel controlTR8ATCC1MRK 504 135-UEN A Section 12Control331Technical manual
