1、7APPLICATION GUIDE FOR ON-LOAD TAP-CHANGERSScopeThis application gde is intended to assist in the selection of suiable on-load tap-changers for use in conjunctionwith the tapped windings of transformers or reactors which,in the following text,are referred to as transformers.As in the second ealition
2、 of I E C Publication 214,On-load Tap-changers(revision of Publication 214(1966),the designation on-oad tap-changeris shortened to tap-cbangerin the remainder of this guide and all thetap-changers referred to shall be presumed to comply with the requirements specified in I E C Publication 214.The re
3、commendations of the application guide are not mandatory and only represent advice to the tap-changermanufacturer and purchaser.The responsibility for the correct application of the fully assembled tap-changer.inconnection.with the transformer is with the manufacturer of the transformer.2.Selcction
4、of a tap-changer2.1 General remarksthe tapchanger representsonya small part of the total cost of the equipment in which it is used,it shoudbesfreely chosen to suit the equipment.However,account should be taken of the available standard types oftar changers.2Insulation levelThe following values occur
5、ring on all tapping positions of the transformer should be checked aganst the tap-changer manufacturers declared values in accordance with Sub-clause 8.6.4 of I E C Publication 214:1)Normal power-frequency operating voltages appearing on the tap-changer in service.2)Power-frequency voltages appearin
6、g on the tap-changer during tests on the transformer.3)Impulse voltages appearing on the tap-changer during tests on the transformer or in service.Note.-With some winding arrangements,the voltages appearing on the transformer can be abnormally high,c.g.:-neutral point tappings in auto-transformers,-
7、line-end tappings,aud-booster transformer arrancsments.These voltages can be affected considerably by the choice of lincer,coarse/fine or reversing tapping arrangements.Methods ofcatering for voltage variation which involve variations in the magnetic flux in the transformer core can also affect the
8、voltagesappearing on various parts of the tap-changer(see I EC Publication 76,Power Transformers).2.3 CurrentThe tap-changer should satisfy the following conditions:1.3.1 Rated through-currentThe rated through-current of the tap-changer as defined in Sub-ciause 4.17 of I E.C Publisation 214 should bentot less than that resulting from the bighest value of tapping current of the tapped winding of the transformer(inaccordance with Sub-clause 4.2 of I E C Publication 76-1,Part 1:General).
