GB/T 18494.3-2023Converter transformers - Part 3: Application guide (English PDF)

foreword

This document is in accordance with the provisions of GB/T 1:1-2020 "Guidelines for Standardization Work Part 1: Structure and Drafting Rules for Standardization Documents"

drafting:

This document is part 3 of GB/T 18494 "Converter Transformers": GB/T 18494 has issued the following parts:

--- Part 1: Industrial converter transformers;

--- Part 2: Converter transformers for HVDC transmission;

--- Part 3: Application guidelines:

This document replaces GB/T 18494:3-2012 "Converter Transformers Part 3: Application Guidelines", and is consistent with GB/T 18494:3-2012

In addition to structural adjustments and editorial changes, the main technical changes are as follows:

---Changed the scope of application (see Chapter 1);

--- Added the need to distinguish between sinusoidal and non-sinusoidal grid-side voltages in the design of converter transformers (see Chapter 5);

---In the 12-pulse wave connection group diagram, the DyYy and DdYd connection methods are added; the third winding with filtering and compensation is added

Industrial equipment needs to consider the fact that the actual current is larger than the rated value (see 6:1);

---Optimized the style of the connection diagram; added the types of autotransformer introduction, including the autotransformer with coarse adjustment and fine adjustment

Open-phase schematic diagram, closed-phase schematic diagram of double-winding transformer with coarse adjustment and fine adjustment, etc: (see 6:2 and 6:3);

---Changed the temperature rise limit of hybrid insulation from "105°C" to "Refer to the limit allowed in 6:2 of GB/T 1094:2-2013",

Prompt that the application method of the new insulating material can be obtained from GB/T 1094:14 (see 8:1:2);

--- Increased the current distribution, loss and hot spot temperature rise of high-current windings (see 9:1:3);

--- Added the content of the stray increase in the loss of the loose coupling of the rectifier (see 9:1:5);

--- Increase the introduction of the transformer connected to the voltage source converter (see 9:1:8);

--- Increased the content considered in the temperature rise test of industrial converter transformers (see 9:2:5);

--- Added content about hot spots of oil tanks of industrial converter transformers (see 9:2:6);

--- Added the relevant content of the saturable reactor iron core and the balanced reactor iron core in the fuel tank (see 10:1:1);

--- Added the influence of harmonics on the core of the converter transformer (see 10:1:2);

--- Added content about the impact of the balanced reactor core design on noise (see 10:2:1);

--- Change the oil breakdown voltage and acid value test from once every two years to at least once a year (see 14:2:2);

--- Added a chapter on the design review of industrial and HVDC converter transformers (see Chapter 16):

This document is modified to adopt IEC 61378-3:2015 "Converter Transformers Part 3: Application Guidelines":

The technical differences between this document and IEC 61378-3:2015 and their reasons are as follows:

---In order to adapt to the technical conditions of our country, IEC 60076-5, IEC 60076-5,

GB/T 1094:14 replaces IEC 60076-14:2013 (see 8:1:2, Chapter 12 and 16:3:4:3);

---Considering the different requirements for rated current in GB/T 18494:1-2014 and GB/T 18494:2-2022, in order to take into account my

According to the actual situation in China, the interpretation of ILN and Kh has been adjusted according to the situation in my country, and the current ratio kh, rated current

Symbol and interpretation of flow Ir and resistive loss IrR at rated current (see Clause 4);

---Considering the different requirements for rated current in GB/T 18494:1-2014 and GB/T 18494:2-2022, in order to take into account my

According to the actual situation of the country, the content of the rated value has been revised respectively (see the first paragraph, the second paragraph and the last paragraph in Chapter 5);

---In order to avoid misunderstanding, the words "when one converter transformer is connected as positive sequence" and "another converter transformer" in the original text of IEC are deleted:

The letter mark given in the brackets behind it when the connection is negative sequence" (see paragraph 1 above Figure 4 in 6:1);

---Considering that the marking habits of transformer terminals in my country are different from those in foreign countries, in order to take into account the actual situation in our country, the three-phase terminals of transformers are marked

The flag is changed from "U, V and W" to "A, B and C" (see Figures 7 to 12 in 6:2:3);

---Considering the difference in impedance deviation requirements for industrial converter transformers and HVDC power transmission converter transformers in my country, for

In order to take into account the actual situation in our country, the content of impedance deviation has been modified: For industrial converter transformers, the requirements are the same as

The original text of IEC is consistent; for HVDC power transmission converter transformers, the requirements are in accordance with the provisions of GB/T 18494:2-2022 (see paragraph 6 of 7:2);

---The rated power frequency of the power supply in our country is 50Hz: In order to meet the actual situation in our country, the 60Hz in the original IEC text is deleted, and only 50Hz is reserved (see 9:1:6);

--- In order to be compatible with the technical content of our standards, the monitoring item "repetitive shock waveform (RSO) or low

Impulse voltage test response" (see 15:3:3):

The following editorial changes have been made to this document:

--- The content of the introduction has been adjusted;

--- Adjusted the order of titles and symbols in Chapter 4;

--- Deleted the last paragraph in 8:2:2;

--- Correct the clause number 9:1:5 mentioned in 9:2:3 to 9:1:6;

--- Deleted the second paragraph of 13:2:1;

--- The letter C representing the valve side is added to Figure 25a) of 13:2:5;

--- Deleted footnote 3 in 15:3:3;

--- The references have been adjusted:

Please note that some contents of this document may refer to patents: The issuing agency of this document assumes no responsibility for identifying patents:

Introduction

0:1 Overview

The formulation of the converter transformer standard is to establish a set of optimal evaluation criteria for the converter transformer, and provide a basis for the production of the converter transformer from the production materials:

Provide guidance on matters needing attention in selection, product design, product production, product inspection, product selection and operation and maintenance:

GB/T 18494 aims to establish principles and relevant regulations applicable to the design, manufacture, test methods, operation and maintenance of converter transformers, etc:

Then, it is proposed to consist of 3 parts:

--- Part 1: Industrial converter transformers: The purpose is to establish applicable to various industries (such as: copper, aluminum smelting and some gas power plants)

solution) with the technical requirements and test requirements of the converter transformer:

--- Part 2: Converter transformers for HVDC transmission: The purpose is to establish suitable for all kinds of high voltage direct current (HVDC) transmission

Converter transformer technical requirements and test requirements, etc:

--- Part 3: Application guidelines: The purpose is to give the technical background of Parts 1 and 2, and to provide a general introduction to various types of industrial rheology:

Provide guidance on the practical application of transformers and various converter transformers for HVDC transmission:

GB/T 18494 clarifies the technical requirements of various industrial converter transformers and HVDC power transmission converter transformers through three parts:

Sum test requirements, and provide guidance for the practical application of these two types of products: By establishing clear scope, terminology, and technical requirements for various products,

Requirements, test methods, practical application guidance, etc:, so that producers, users and relevant test personnel can operate more clearly and accurately, so that

Design and manufacture high-quality products, and make them reasonably applied, better promote trade, exchanges and technical cooperation, and contribute to the normalization of my country's power grid

Guaranteed regular operation:

This document contains two types of products applicable to GB/T 18494:1-2014 and GB/T 18494:2-2022, applicable to 0:2~

0:14 covered content: GB/T 18494:1-2014 applies to power converters of any capacity (typical applications include crystal

Thyristor rectifiers, diode rectifiers for electrolysis, thyristor rectifiers for high power drives, thyristor rectifiers for scrap furnaces and variable speed drives

Diode rectifiers for inverters), also suitable for step-down regulators or autotransformer voltage regulation units, the maximum voltage of the valve side winding equipment is not

More than 40:5kV: GB/T 18494:2-2022 applies to converter transformers for HVDC power transmission: There are two types of HVDC power transmission systems

type, one of the "back-to-back" type and the other of the "transmission" type, the operation and evaluation of the converter transformers operating in both systems are covered in

GB/T 18494:2-2022 and this document:

Both GB/T 18494:1-2014 and GB/T 18494:2-2022 do not explicitly include the current conversion related to the voltage source converter (VSC)

transformer: Because the use of VSC is becoming more and more common, this document provides some guidance:

0:2 Ratings (Chapter 5)

In GB/T 18494:1-2014, the regulation on the rated value of the converter transformer is different from the traditional method: in tradition

In the method, the rated value of the transformer nameplate current is defined by the root mean square value of the current: GB/T 18494:1-2014 on converter transformers

The method of rating definition presents a fundamental change: Clarifies converter transformer nameplate ratings in terms of fundamental components of voltage and current

as the basis: The nameplate rating derived from the fundamental component is the basis for guaranteed impedance and loss values: In GB/T 18494:2-2022, the amount

The constant current is the root mean square of the fundamental current and the 49th harmonic and all harmonic currents before it under rated load conditions:

0:3 Winding structure (Chapter 6)

A large number of winding connections and principles have been applied to converter transformers for industrial and HVDC power transmission: Over the years, they have been continuously

development of: Most of the operating characteristics of various rectification couplings have been included in GB/T 3859 (all parts): In this document, the link

The effect of the junction on the structure of the converter transformer and some aspects of its operation are discussed:

Different pressure regulation methods are common in industrial applications, and this document provides schematic diagrams of several pressure regulation methods:

0:4 Tapping and Impedance (Chapter 7)

The impedance of the converter transformer for HVDC transmission requires special attention and requires special design schemes: The main concern is to tap across the

Limits for impedance variations within the range and for impedance differences between different converter transformers, and in some applications star and delta junctions

Limit for impedance difference between windings: This document discusses these limits and their practical application:

Usually, the tap range of a converter transformer is larger than that of a conventional transformer: This document discusses the impact of such a large tapping range on converter transformers and taps:

The effect of the switch:

0:5 Insulation and insulation test (Chapter 8)

This chapter deals with two aspects, the first is to increase the use of "hybrid insulation" insulation structures in industrial applications: Followed by HVDC power transmission

Insulation capacity of the insulation structure of the converter transformer in the external DC voltage test and in operation:

The basic principles, test methods and test voltage levels of AC and DC voltage tests are discussed: Compatible with the recommended test specification

The relevant security measures were commented on:

0:6 Loss (Chapter 9)

This document details the principles, test methods and calculation methods used in considering the effects of non-sinusoidal load currents on various types of converter transformers:

relevant content of the law:

The principle of dual-frequency test in HVDC application is described in detail with calculation examples: These loss values obtained from tests and calculations are determined as

Used in temperature rise tests as a basis for establishing oil and winding temperature gradient test currents:

0:7 Iron Core and Noise (Chapter 10)

The effects of voltage harmonics and DC bias current on core structure and performance are discussed and summarized:

The causes of noise generation and expected differences between conventional plant sound level measurements and field measurements and expectations are reviewed:

The latest methods for estimating sound levels of converter transformers are discussed:

0:8 Technical Specifications (Chapter 11)

The specifications for converter transformers differ significantly from those for power transformers: The detailed points are part of the guidance document for the preparation of technical and functional specifications:

Some guiding principles are given for which specified content should be put forward by the user and the manufacturer in the order bidding stage:

0:9 Short Circuit (Chapter 12)

In a conventional power transformer, the calculation of the short-circuit current inside the winding is only related to the reactance and resistance components of the transformer and the power supply connected to the transformer:

However, for converter transformers, it is necessary to consider that the fault current peak value generated in the converter may be higher than that of conventional power transformers:

The case of the short-circuit current peak value of the device: This situation is detailed in this document:

0:10 Components (Chapter 13)

The selection and operation of on-load tap-changers is a critical issue when designing converter transformers for industrial and HVDC transmission applications:

question: This document enumerates some principles for tap-changers to be used in these applications:

In HVDC applications, the design of the valve side bushing and its integration with the overall body are key issues:

The general requirements for bushings, structural suggestions, combination of bushings and converter transformers and test requirements are described in detail:

0:11 Maintenance (Chapter 14)

Statistics show that HVDC power transmission converter transformers require high standards of maintenance: Particular attention must be paid to the on-load tap-changer and valve side bushings:

This document presents requirements for maintenance:

0:12 Monitoring and field research (Chapter 15)

If you want to reduce on-site problems, it is recommended to conduct on-site monitoring of the converter transformer: In this context, only condition monitoring is discussed: this document

Suggestions are also put forward on the working procedures and practical operations that should be carried out after the on-site accident: These recommendations are based on investigation and research

In the initial stage, those important evidence and data will not be lost or damaged:

This chapter also discusses condition monitoring suitable for this application purpose:

0:13 Supplementary Information

When formulating this document, especially the content of HVDC converter application in GB/T 18494:2-2022, it was obviously influenced by CI-

GRE Joint Working Group 12/14:10 Impact of each monograph:

Converter transformers part 3 : guidelines for application

1 Scope

This document provides users with information on the design, structure, test and operation of industrial converter transformers and HVDC power transmission converter transformers:

information on how operating conditions differ from conventional transformers used in power systems: In addition, GB/T 18494:1-2014 and

Technical background of GB/T 18494:2-2022:

This document is applicable as a supplement to GB/T 13499-2002, but does not replace GB/T 13499-2002, because GB/T 13499-

The general principles covered in:2002 apply equally to converter transformers:

2 Normative references

The contents of the following documents constitute the essential provisions of this document through normative references in the text: Among them, dated references,

Only the version corresponding to the date applies to this document; for undated references, the latest version (including all amendments) applies to this document:

GB/T 1094:1-2013 Power Transformers Part 1: General Rules (IEC 60076-1:2011, MOD)

Note: There is no technical difference between the referenced content of GB/T 1094:1-2013 and the referenced content of IEC 60076-1:2011:

GB/T 1094:5 Power transformers Part 5: Short-circuit withstand capability (GB/T 1094:5-2008, IEC 60076-5:2006, MOD)

GB/T 1094:14 Power transformers Part 14: Liquid-immersed transformers using high-temperature insulating materials (GB/T 1094:14-

2022, IEC 60076-14:2013, MOD)

GB/T 18494:1-2014 Converter Transformers Part 1: Converter Transformers for Industrial Use (IEC 61378-1:2011, MOD)

Note: There is no technical difference between the referenced content of GB/T 18494:1-2014 and the referenced content of IEC 61378-1:2011:

GB/T 18494:2-2022 Converter Transformers Part 2: Converter Transformers for High Voltage Direct Current Transmission (IEC /IEEE 60076-57-19:2017, MOD)

Note: There is no technical difference between the referenced content of GB/T 18494:2-2022 and the referenced content of IEC /IEEE60076-57-19:2017:

3 Terms and Definitions

The terms and definitions defined in GB/T 18494:1-2014 and GB/T 18494:2-2022 apply to this document:

4 symbols

The following symbols apply to this document:

FSE --- additional coefficient of stray loss in structural parts;

FWE --- eddy current loss additional coefficient in the winding;

fh --- frequency of h harmonic (Hz);

fX --- the frequency used to determine the distribution of eddy current losses (not less than 150Hz, only applicable to converter transformers for HVDC power transmission);

f1 ---Rated frequency, that is, the fundamental frequency (50Hz or 60Hz);

h --- harmonic times;