IEC 60214-2

Tap-changers - Part 2: Application guide

Assists in the selection of tap-changers designed in accordance with IEC 60214-1 for use in conjunction with the tapped windings of transformers or reactors. Also assists in understanding the various types of tap-changers and their associated equipment available. Covers both on-load tap-changers and off-circuit tap-changers.

Odcepni preklopniki - 2. del: Navodilo za uporabo

General Information

• Status: Not Published
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: SC 14 - Data element principles
• Current Stage: PPUB - Publication issued
• Start Date: 14-Oct-2004
• Ref Project: oSIST IEC 60214-2:2009 - Tap-changers - Part 2: Application guide

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Odcepni preklopniki - 2. del: Navodilo za uporaboTap-changers - Part 2: Application guide29.180Transformatorji. DušilkeTransformers. ReactorsICS:Ta slovenski standard je istoveten z:IEC 60214-2oSIST IEC 60214-2:2009en01-december-2009oSIST IEC 60214-2:2009SLOVENSKI
STANDARD



oSIST IEC 60214-2:2009



INTERNATIONAL STANDARD IEC60214-2 First edition2004-10 Tap-changers – Part 2: Application guide
 IEC 2004

Copyright - all rights reserved No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. International Electrotechnical Commission,
3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, SwitzerlandTelephone: [phone] Telefax: [phone] E-mail: [e-mail]
Web: www.iec.ch W For price, see current cataloguePRICE CODE
Commission Electrotechnique InternationaleInternational Electrotechnical CommissionoSIST IEC 60214-2:2009



– 2 – 60214-2  IEC:2004(E)
CONTENTS FOREWORD.4 INTRODUCTION.6
1 Scope.7 2 Normative references.7 3 Terms and definitions.7 4 Symbols and abbreviations.7 5 Types of tap-changer.8 5.1 General.8 5.2 On-load tap-changers.8 5.3 Off-circuit tap-changers.15 5.4 Liquid-immersed tap-changers.15 5.5 Dry-type tap-changers.16 5.6 Other types.17 5.7 Protective devices.18 6 Selection of tap-changers.21 6.1 General.21 6.2 On-load tap-changers.22 6.3 Off-circuit tap-changers.27 7 Location of liquid-immersed tap-changers.29 7.1 Tap selectors.29 7.2 Diverter and selector switches.29 8 Fittings.29 8.1 Valves, air-release vents and liquid sampling devices.29 8.2 Liquid level gauges.29 8.3 Low liquid level alarms.30 8.4 Nameplate and other plates.30 8.5 Devices to aid maintenance.30 8.6 Dehydrating breathers.30 9 Field service (operation, maintenance and monitoring).30 9.1 Operation.30 9.2 Maintenance.32 9.3 Monitoring in service.32 10 Information to be provided by the transformer manufacturer.34 10.1 Information required at the enquiry or order stage for an on-load tap-changer.34 10.2 Information required with enquiry or order for off-circuit tap-changers.36 10.3 Documentation.36 11 Protection and safety.37 11.1 Protection.37 11.2 Safety aspects.37 11.3 Immersing medium.37
oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 3 –
Figure 1 – External separate selector and diverter compartments (for mounting on the end or side of the transformer).9 Figure 2 – External mounted selector switch tap-changer (for mounting on the end or side of the transformer).10 Figure 3 – External mounted in-tank with separate barrier board.10 Figure 4 – In-tank separate selector and diverter switch.12 Figure 5 – In-tank selector switch tap-changer.13
oSIST IEC 60214-2:2009



– 4 – 60214-2  IEC:2004(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
TAP-CHANGERS –
Part 2: Application guide
FOREWORD 1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any misinterpretation by any end user. 4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications transparently to the maximum extent possible in their national and regional publications. Any divergence between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter. 5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any equipment declared to be in conformity with an IEC Publication. 6) All users should ensure that they have the latest edition of this publication. 7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and members of its technical committees and IEC National Committees for any personal injury, property damage or other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is indispensable for the correct application of this publication. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 60214-2 has been prepared by IEC technical committee 14: Power transformers.
This standard cancels and replaces IEC 60542 (1976) and its amendment 1 (1988). This first edition constitutes a technical revision of that standard. The text of this standard is based on the following documents: FDIS Report on voting 14/490/FDIS 14/492/RVD
Full information on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 5 –
IEC 60214 consists of the following parts, under the general title Tap-changers: Part 1: Performance requirements and test methods Part 2: Application guide
The committee has decided that the contents of this publication will remain unchanged until the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in the data related to the specific publication. At this date, the publication will be
• reconfirmed; • withdrawn; • replaced by a revised edition, or • amended.
A bilingual version of this publication may be issued at a later date.
oSIST IEC 60214-2:2009



– 6 – 60214-2  IEC:2004(E)
INTRODUCTION The recommendations in this application guide represent advice to the tap-changer manufacturer and purchaser.
It is stressed that the responsibility for the correct application of the fully assembled tap-changers in connection with the transformer lies with the manufacturer of the transformer. oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 7 –
TAP-CHANGERS –
Part 2: Application guide
1 Scope This part of IEC 60214 is intended to assist in the selection of tap-changers designed in accordance with IEC 60214-1 for use in conjunction with the tapped windings of transformers or reactors. It is also intended to assist in understanding the various types of tap-changers and their associated equipment available. The application guide covers on-load tap-changers (resistor and reactor types) and off-circuit tap-changers. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60076-1:1993, Power transformers – Part 1: General
Amendment 1(1999)1 IEC 60076-3:2000, Power transformers – Part 3: Insulation levels, dielectric tests and external clearances in air IEC 60076-5:2000, Power transformers – Part 5: Ability to withstand short circuit IEC 60076-11:2004, Power transformers – Dry-type transformers
IEC 60214-1:2003, Tap-changers – Part 1: Performance requirements and test methods IEC 60296:2003, Fluids for electrotechnical applications – Unused mineral insulating oils for transformers and switchgear IEC 60354:1991, Loading guide for oil-immersed power transformers IEC 60599:1999, Mineral oil-impregnated electrical equipment in service – Guide to the interpretation of dissolved and free gases analysis
3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60214-1 apply. 4 Symbols and abbreviations DGA Dissolved gas analysis
HVDC High-voltage direct current
PST Phase-shifting transformer
___________ 1 There exists a consolidated edition 2.1 (2000) that includes edition 2.0 and its amendment. oSIST IEC 60214-2:2009



– 8 – 60214-2  IEC:2004(E)
5 Types of tap-changer 5.1 General Tap-changers are devices that will vary the turns ratio of a transformer and hence regulate the voltages of that transformer. Tap-changers that can perform this operation can broadly be divided into two fundamental types as follows: – on-load tap-changers; – off-circuit tap-changers. 5.2 On-load tap-changers 5.2.1 General The on-load tap-changer is designed to change tap position and hence vary the turns ratio of the transformer whilst it is both energized and on load. It performs this function without any interruption of the supply. This is achieved with mechanically operated devices that will select the various tap positions and switch the load currents and step voltages. On-load tap-changing can be employed by using various switching principles. The two most common switching principles are: – high-speed transition resistor type switching; and – transition reactor (preventive autotransformer) type switching. 5.2.2 Resistor-type on-load tap-changers 5.2.2.1 General Resistor-type on-load tap-changers can be divided into two distinctive types: – external out-of-tank tap-changers (air environment), as described in 5.2.2.2; – in-tank tap-changers (liquid environment), as described in 5.2.2.3. The operating sequences of the different resistor type tap-changers are shown in IEC 60214-1, Table A.1. 5.2.2.2 External resistor-type on-load tap-changers 5.2.2.2.1 General These tap-changers are self-contained in their own tanks (except dry-type tap-changers) and mounted on the side or end of the transformer. Four types of tap-changer arrangements are considered, all employing the high-speed transition resistor switching principle. 5.2.2.2.2 External separate selector and diverter compartments This type of tap-changer has two separate compartments, one for the pre-selection of the transformer taps called the tap selector compartment and the other for the on-load switching called the diverter switch compartment. The two compartments have separate liquid chambers and both are isolated from the liquid in the main transformer tank, although the tap selector compartment and the main tank may share the same conservator. The taps from the transformer are taken to the selector contacts through a liquid-tight barrier board. The tap selector compartment contains clean liquid enabling it to withstand the required higher voltages across the contacts. The diverter switch compartment isolates the carbonized liquid and gases. As can be seen from Figure 1, the tap-changer bolts on the side or end of the transformer. This arrangement is generally used for the larger MVA transformers.
oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 9 –
1 24 5 6 3IEC
1390/04
Key 1 Transformer windings 3 Liquid and gas tight barrier 5 Drive mechanism 2 Tap leads 4 Diverter switch compartment 6 Tap selector compartment
Figure 1 – External separate selector and diverter compartments (for mounting on the end or side of the transformer) The switching can be by arc extinction in the liquid or by vacuum interrupters/power electronics. 5.2.2.2.3 External mounted separate selector and diverter in single compartment This type of tap-changer uses separate selector and diverter contact systems in a similar way to the double compartment arrangement in 5.2.2.2.2 but combines them in a single compartment.
The switching can be by arc extinction in the liquid or by vacuum interrupters/power electronics. 5.2.2.2.4 External mounted selector switch tap-changers Selector switch tap-changers are contained in a single compartment, normally bolted on the side or the end of the transformer (see Figure 2). Again, the transformer taps are taken to the tap-changer contacts through a liquid-tight barrier board. The selection and switching are carried out using common contacts in the same liquid and chamber. These tap-changers tend to be used on the smaller MVA and voltage class transformers. oSIST IEC 60214-2:2009



– 10 – 60214-2  IEC:2004(E)
1 245 3IEC
1391/04
Key 1 Transformer windings 3 Liquid and gas tight barrier 5 Drive mechanism 2 Tap leads 4 Selector switch compartment
Figure 2 – External mounted selector switch tap-changer (for mounting on the end or side of the transformer) 5.2.2.2.5 External mounted in-tank with separate barrier board By using an in-tank tap-changer in a separate pocket with a liquid-tight barrier board between the tap-changer and the transformer, it effectively becomes a separate bolt-on type of tap-changer. The liquid from the selector is totally isolated from the transformer although the selector compartment and the main tank may share the same conservator. Figure 3 shows how this arrangement works and gives all the advantages of the separate tank tap-changer for the higher voltage classes.
1 2346 5IEC
1392/04
Key 1 Transformer windings 3 Liquid and gas tight barrier 5 Diverter switch 2 Tap leads 4 Tap selectors 6 Drive mechanism Figure 3 – External mounted in-tank with separate barrier board oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 11 –
5.2.2.2.6 Advantages and disadvantages of external mounted on-load tap-changers External mounted on-load tap-changers generally have the advantage of being easier for the user to maintain. Access to the complete tap-changer and all contacts is obtained by removal of inspection covers. Because the selectors are always in a separate chamber, the DGA of the transformer is not affected by capacitive sparking of the selector and change-over of selector contacts. Monitoring of the separate selector compartments can be carried out in isolation allowing early diagnosis of selector problems and the ability to differentiate between selector and main transformer defects. Due to voltage clearance considerations, external mounted out-of-tank on-load tap-changers have the disadvantage of not being practical for line-end applications above 145 kV. 5.2.2.3 In-tank resistor type on-load tap-changers 5.2.2.3.1 General As their name implies, these tap-changers are fitted inside the transformer. They are normally suspended from the lid of the transformer either at one end in the case of a single three- phase pole or along the side when three single-phase poles are used. A pole can consist of one, two or three phases. Two poles can also be used for some Delta applications. Three types are considered, all of them having high speed resistor switching. 5.2.2.3.2 In-tank separate selector and diverter switch With this type of tap-changer, separate selectors are mounted underneath the diverter switch and operate in the same liquid as the transformer. There are two selector rings per phase, one containing the odd-numbered taps and the other the even-numbered taps, and moving contact arms radially pre-select a tap position without current flowing prior to the diverter switching to that position. The diverter switch is mounted in a gas- and liquid-tight insulated compartment which separates the arcing gases and carbonized liquid from the transformer liquid. Usually the diverter compartment is equipped with a separate conservator breathing to atmosphere. This type of tap-changer is used for the higher MVA ratings and voltage classes. Figure 4 shows how this arrangement works. oSIST IEC 60214-2:2009



– 12 – 60214-2  IEC:2004(E)
1 235 4 IEC
1393/04
Key 1 Transformer windings 3 Tap selectors 5 Drive mechanism 2 Tap leads 4 Diverter switch
Figure 4 – In-tank separate selector and diverter switch The switching can be by arc extinction in the liquid or by vacuum interrupters/power electronics. 5.2.2.3.3 In-tank selector switch tap-changers In-tank selector switch tap-changers carry out their selection and switching in the one compartment using the same contacts and liquid. The fixed contacts are radially mounted around a vertical insulated compartment with the three phases mounted one above the other. The carbonized liquid and gases are separated from the main transformer liquid by the liquid- tight compartment. The moving contacts are fixed to a central insulated drive shaft. This type of tap-changer tends to be used for the lower MVA and voltage class transformers (see Figure 5). oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 13 –
1 235 4 IEC
1394/04
Key 1 Transformer windings 3 Selector switch terminals 5 Drive mechanism 2 Tap leads 4 Change-over selector terminals
Figure 5 – In-tank selector switch tap-changer 5.2.2.3.4 In-tank separate selector and diverter switch in single compartment This type of tap-changer uses separate contacts for the selection of the taps and different contacts for the switching. Normally, all moving selector contacts would pre-select a tap before the diverter contacts switch to that tap. The sequence of operation would be similar to a tap-changer described in 5.2.2.3.2 but both sets of contacts are contained in the one compartment. The switching can be by arc extinction in the liquid or by vacuum interrupters/power electronics.
5.2.2.3.5 Advantages and disadvantages of in-tank on-load tap-changers In-tank on-load tap-changers have the advantage of being more suitable for the higher voltage class line-end applications. They can also benefit the transformer manufacturer by allowing the tap-changer to be connected to the transformer prior to processing. For a given power rating, an in-tank tap-changer will generally have a smaller oil volume. This has the advantage of smaller oil volumes to handle during maintenance but a disadvantage that more frequent maintenance may be required. Where in-tank tap-changer types have their selectors and change-over selectors in particular, operating in the same liquid as the transformer, the DGA of the transformer can be influenced by capacitive arcing from the contacts. 5.2.3 Reactor-type on-load tap-changers 5.2.3.1 General Reactor-type on-load tap-changers are normally designed to be applied to the low voltage winding of the transformer. They can be divided into two distinctive types: – external out-of-tank tap-changers (air environment), as described in 5.2.3.2; – in-tank tap-changers (liquid environment), as described in 5.2.3.3. oSIST IEC 60214-2:2009



– 14 – 60214-2  IEC:2004(E)
5.2.3.2 Reactor-type external on-load tap-changers 5.2.3.2.1 General These tap-changers are self-contained in their own tanks and mounted on the side or end of the transformer. The taps from the transformer regulating winding are taken to the tap selector contacts through a liquid tight barrier board (component of the on-load tap-changer). The liquid from the tap-changer is totally isolated from the transformer main tank and, therefore, can be checked separately by liquid sampling. Three types of tap-changer arrangements are considered. 5.2.3.2.2 Diverter switch and tap selector This type of tap-changer consist of change-over selectors and tap selectors, designed to select tap connections, and transfer switches (diverter switches or vacuum interrupters), designed to break and make current and, therefore, perform the arcing duty of the tap- changing operations. The separate devices are normally located in a common liquid compartment similar to that shown in Figure 1. This design of a tap-changer tends to be used on the larger MVA transformers. The operating sequence of a reactor type tap-changer with diverter switch and tap selector is shown in IEC 60214-1, Figure B.5. 5.2.3.2.3 Selector switch (arcing tap switch) tap-changers This type of tap-changer will incorporate a selector switch (arcing tap switch) which performs the functions of making/breaking current and selection of tap connections, combining the duties of a tap selector and a diverter switch. The selector switch and the change-over selector, if they exist, are contained in one single compartment. This design of a tap-changer tends to be used on the smaller MVA transformers. The operating sequence of reactor type tap-changers with selector switch is shown in IEC 60214-1, Figure B.1. 5.2.3.2.4 Vacuum interrupter (with by-pass switches) and tap selector This tap-changer design also consists of a single liquid compartment containing change-over and tap selectors to select taps and one vacuum interrupter per phase to break and make current. In addition, they may be equipped with by-pass switches, mainly designed to by-pass the vacuum interrupter when the tap-changer is not performing a tap-change operation. By using vacuum interrupters to perform the breaking duty of the tap-changing operations, the carbonization of the insulating liquid is minimized which enables the device to withstand higher voltages. This arrangement is generally used for the larger MVA transformers. The operating sequence of a reactor-type tap-changer with vacuum interrupter and tap selector is shown in IEC 60214-1, Figure B.7. 5.2.3.3 Reactor-type internal on-load tap-changers
These designs are exclusively used in voltage regulators. The tap-changer is fitted inside the transformer tank and is normally located on top of the transformer adjacent to the preventive autotransformer (reactor).
This type of tap-changer will incorporate a load transferring selector switch (arcing tap switch) which performs the functions of switching current and tap selection. Since tap changing is performed in the same tank as the main transformer windings the insulating liquid should be checked frequently to insure the dielectric integrity of the transformer. The transformer taps are taken to the tap-changer contacts that are located on an insulated board. The selection and switching are carried out using common contacts. oSIST IEC 60214-2:2009



60214-2  IEC:2004(E) – 15 –
The transformer manufacturer needs to take into account the potentially heavy carbonization of the liquid in the main transformer tank.
5.3 Off-circuit tap-changers The off-circuit tap-changer is designed to change tap position and hence vary the turns ratio of the transformer whilst it is de-energized.
This is achieved with mechanically operated devices that will select the various taps. The fixed contacts may be arranged in a circular configuration (for rotary types) or in a straight line (for rack and slide types). Normally, the drive mechanism is manual, but motor drive units are also available. This type of tap-changer is usually mounted inside the transformer tank with the drive mechanism mounted on the transformer lid or on the wall of the transformer tank. 5.4 Liquid-immersed tap-changers 5.4.1 General Liquid-immersed tap-changers cover all the types described in 5.2 and 5.3 that require a liquid for use as either insulation or arc quenching during the switching operation. A typical, and the most common, liquid is mineral oil (transformer oil) according to IEC 60296. Other types of liquids may be employed for insulation and switching purposes but care has to be exercised to ensure its compatibility with the tap-changer under consideration. 5.4.2 Liquid immersed on-load tap-changers The liquid used for on-load tap-changers, as well as having electrical insulation and switching functions, also acts as a lubricant and coolant. The most commonly used liquid for tap-changers is mineral oil to IEC 60296. Although this oil has relatively poor lubricating properties, it is nevertheless essential for the mechanical operation of the tap-changer. It is therefore recommended that the tap-changer manufacturer be consulted before operating mechanically off circuit in a non-immersed (unfilled) condition.
Other liquids that are sometimes used in transformers for fire-retardant and environmental purposes may not be suitable for on-load tap-changers. Silicone fluids have very poor lubricating properties and no arc-quenching ability and cannot be used for on-load tap-changers. Synthetic esters and High Molecular Weight (HMW) paraffins have good lubrication and arc extinction properties and may be suitable for some on-load tap-changers. The temperature operating range may be restricted due to higher viscosities than transformer oil at lower temperatures. Where a liquid other than mineral oil according to IEC 60296 is being considered, the tap-changer manufacturer should be consulted to establish its suitability. Liquid immersed on-load tap-changers tested to IEC 60214-1 are suitable for operation down to –25 °C in transformer oil according to IEC 60296. For temperatures below –25 °C, the tap-changer manufacturer may recommend a lower viscosity oil, the installation of heaters in the switching and mechanism compartments or other precautions to proh
...