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GB/T 20840.14-2022Instrument transformers - Part 14: Additional requirements for current transformers for DC applications (English PDF)

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Issued by

State Administration for Market Regulation, China National Standardization Administration

Level / Type

National · Recommended

Issue date

October 14, 2022

Implementation date

May 1, 2023

Scope

GB/T 20840.14-2022 (Instrument transformers - Part 14: Additional requirements for current transformers for DC applications) is available as an English-translated PDF.

GB/T 20840.14-2022 — This document specifies the terminology for a DC current transformer (DCCT) whose output signal can be analog or digital using any technology and all supplementary technical requirements for definitions, ratings, design and construction, testing, etc. This document applies to newly manufactured current transformers for measurement, protection and/or control in DC power systems with rated voltages greater than 1.5kV sensor. Note 1.Figure 601 of GB/T 20840.6-2017 describes the general configuration of single-pole low-power transformers. This document does not apply to DCCTs used for current measurements on the VSC valve transistor branch (referred to in Figure 1403 and Table 1402 CT4a and CT4b). Note 2.This will be considered in future revisions.

Document preview — GB/T 20840.14-2022

National Standard of the People's Republic of China

ICS: 29.180
Classification: K 41

Issued by: State Administration for Market Regulation, China National Standardization Administration

foreword
Introduction
0.1 Overview
0.2 Grid Commutated Converter (LCC)
0.3 Voltage Source Converter (VSC)
1 Scope
2 Normative references
3 Terms and Definitions

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 of Standardization Documents"

drafted.

This document is part 14 of GB/T 20840 "Transformer". GB/T 20840 has released the following parts.

--- Part 1.General technical requirements;

--- Part 2.Supplementary technical requirements for current transformers;

--- Part 3.Supplementary technical requirements for electromagnetic voltage transformers;

--- Part 4.Supplementary technical requirements for combined transformers;

--- Part 5.Supplementary technical requirements for capacitive voltage transformers;

--- Part 6.Supplementary general technical requirements for low-power transformers;

--- Part 7.Electronic voltage transformers;

--- Part 8.Electronic current transformers;

--- Part 9.Digital interface of transformers;

--- Part 14.Supplementary technical requirements for DC current transformers;

--- Part 15.Supplementary technical requirements for DC voltage transformers;

--- Part 102.Ferromagnetic resonance in substations with electromagnetic voltage transformers;

--- Part 103.The application of transformers in power quality measurement.

This document is revised and adopted IEC 61869-14.2018 "Transformers - Part 14.Supplementary technical requirements for DC current transformers".

Compared with IEC 61869-14.2018, this document has more structural adjustments. List of structural changes between the two files

See Appendix 14A.

Compared with IEC 61869-14.2018, this document has many technical differences. In the outer margins of the clauses involved, vertical

A straight single line (|) is marked. See Appendix 14B for a list of these technical differences and their reasons.

The following editorial changes have been made to this document.

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

---The content of paragraphs 1 and 4 of Chapter 1 has been rewritten, and the content of paragraph 3 and the last sentence of paragraph 4 have been replaced by the text.

Adjusted to Note;

--- Adjust "Note 1" in 3.1.1402, 3.3.1401, 3.3.1403, 3.4.1401, 3.5.1402, 3.5.1403 to "Note";

--- Adjusted the footnote form and symbol description form of Tsr and Ts in Figure 1404 of 3.5.1401;

--- The order of symbols in 3.7 has been adjusted;

--- Modified the punctuation between the values in 5.5.602, 5.5.1401, 5.6.1402 and 5.6.1403;

--- Adjusted the content of Note 5.5.1401;

--- Added numbers to the two notes in 5.6.1404.1 and 5.6.1404.2 respectively;

--- The content of the note in 6.6.1 has been adjusted;

--- Adjusted the header format of Table 7 of IEC 61869-14.2018;

--- Adjusted the headings of 6.13.1401 and 6.13.1403, and added a header to Table 1404;

--- Adjusted the item serial number in 6.13.1404;

--- The order of the test items in Table 10 of IEC 61869-14.2018 has been adjusted;

--- Change the unit of resistivity in the symbol description of the "penetration depth" calculation formula in Appendix 14A of IEC 61869-14.2018 by

"ohm/m" is corrected to "ohm.m";

--- The formulas in the full text are numbered uniformly, and the capitalization of formula symbols and the writing form of formulas have been revised;

--- References have been adjusted.

Please note that some content of this document may be patented. The issuing agency of this document assumes no responsibility for identifying patents.

Introduction

0.1 Overview

The establishment of transformer standards is to establish a set of optimal evaluation criteria for transformers, and to provide transformers from raw material selection, design, production, etc.

Provide guidance on matters needing attention in production, inspection, selection, operation and maintenance. GB/T 20840 aims to specify the

The principles and related rules for design, manufacture, test, operation and maintenance are planned to be composed of 13 parts.

--- Part 1.General technical requirements. The purpose is to specify the requirements applicable to the design, manufacture and production test of various types of transformers.

General technical requirements to follow.

--- Part 2.Supplementary technical requirements for current transformers. The purpose is to specify complementary technologies applicable to various types of current transformers

Require.

--- Part 3.Supplementary technical requirements for electromagnetic voltage transformers. The purpose is to specify the application to various types of electromagnetic voltage transformers

supplementary technical requirements.

--- Part 4.Supplementary technical requirements for combined transformers. The purpose is to specify supplementary techniques applicable to various types of combined transformers.

technical requirements.

--- Part 5.Supplementary technical requirements for capacitive voltage transformers. The purpose is to stipulate that it is suitable for all kinds of capacitive voltage transformers

supplementary technical requirements.

--- Part 6.Supplementary general technical requirements for low-power transformers. The purpose is to specify the compensation applicable to various types of low-power transformers.

charging technical requirements.

--- Part 7.Electronic voltage transformers. The purpose is to specify supplementary technical requirements applicable to various types of electronic voltage transformers.

--- Part 8.Electronic current transformers. The purpose is to specify supplementary technical requirements applicable to various types of electronic current transformers.

--- Part 9.The digital interface of the transformer. The purpose is to specify the technical requirements applicable to the digital interface of various electronic transformers.

--- Part 14.Supplementary technical requirements for DC current transformers. The purpose is to specify the compensation applicable to various types of DC current transformers.

charging technical requirements.

--- Part 15.Supplementary technical requirements for DC voltage transformers. The purpose is to specify the compensation applicable to various types of DC voltage transformers.

charging technical requirements.

--- Part 102.Ferromagnetic resonance in substations with electromagnetic voltage transformers. The purpose is to

Provide guidance on the generation mechanism and suppression of ferromagnetic resonance in transformer substations.

--- Part 103.The application of transformers in power quality measurement. The purpose is to analyze the application of various transformers in power quality measurement.

Provide guidance on usage.

This document is consistent with GB/T 20840.1-2010 "Transformer Part 1.General Technical Requirements" and GB/T 20840.6-2017 "Mutual Inductance"

Part 6.Supplementary general technical requirements for low-power transformers. This document follows GB/T 20840.1-2010 and

The writing structure of GB/T 20840.6-2017 is an addition and modification to its corresponding clauses. When GB/T 20840.1-2010 or

When the terms of GB/T 20840.6-2017 are not mentioned in this document, as long as they are reasonable, these terms also apply to this document. Dangben

When the document indicates "addition", "modification" or "replacement", it means the relevant

The terms have been adapted accordingly in this document.

For the chapters, clauses, figures, tables, notes and appendices supplemented on the basis of GB/T 20840.1-2010 and GB/T 20840.6-2017, this

Documents use the following numbering format.

--- The numbering of chapters, bars, figures, tables and notes starts from 1401;

---Appendix numbers are 14A, 14B, etc.

GB/T 20840 clarifies the technical specifications of various transformer products through 13 parts, and gives specific technical requirements, test items

Items, test procedures, test methods and operation instructions. By establishing clear scope, terminology, technical requirements and test requirements for various products

etc., so that the personnel engaged in the design, production, testing and use of related products can operate more clearly and accurately, so as to provide

It lays the foundation for designing and manufacturing high-quality products, better promotes trade, exchanges and technical cooperation, and provides support for the normal operation of my country's power grid.

Assure.

This document specifies the supplementary technical requirements for DC current transformers, mainly applicable to DC application fields with at least one of the following functions

Closed current transformer.

--- measure DC current (including significant harmonics);

--- Withstand DC voltage.

Depending on their location in the DC system, current transformers have different application requirements, the following are the voltages or currents associated with them

Waveform for a brief introduction.

Note. This document includes, but is not limited to, the applications of the examples described below.

0.2 Grid Commutated Converter (LCC)

The grid-commutated converter (LCC) is based on a thyristor converter (see Figure 1401), and features adjustable unidirectional current and voltage polarity.

There are significant voltage and current harmonics, and the frequency can reach about 3kHz~4kHz.

Figure 1401 Example of LCC scheme

This example distinguishes between three different current measurement functions.

---CT1.Measurement of the AC side current of the converter;

---CT2.Measurement of the DC side current of the converter;

---CT3.Measurement of the current in the DC filter.

Table 1401 summarizes the current and voltage waveforms and their main characteristics of current transformers in different applications.

Table 1401 Current and Voltage of Current Transformers in LCC Applications

Category Current Waveform Voltage Waveform Characteristics

CT1

Alternating current

AC and DC voltage

Lots of current harmonics

Mainly used for protection

CT2

Pure DC

High accuracy measurement

Harmonic measurement

For measurement, control and protection

CT3

DC voltage with harmonics

DC current=0A

Harmonic measurement

Mainly used for protection

0.3 Voltage Source Converter (VSC)

Voltage source converters (VSCs) are based on transistor converters and feature bidirectional current flow and single voltage polarity. Voltage and current harmonics

The frequency of the waves can be up to about 20 kHz.

Typical VSC schemes come in two forms. symmetrical unipolar (using one inverter) and asymmetrical unipolar or bipolar (using one inverter per pole)

streamer).

Two schemes are shown in Figure 1402 and Figure 1403.

Figure 1402 Example of a typical VSC scheme --- Symmetrical unipolar

Figure 1403 Example of a typical VSC scheme - asymmetrical unipolar or bipolar

This example distinguishes between three different current measurement functions.

---CT4.Measurement of the current in the transistor branch of the converter. Current transformers can be placed before (CT4a) or after the transistor branch

(CT4b).

---CT2.Measurement of the DC side current of the converter.

---CT3.Measurement of the current in the DC filter (not always present in this scheme).

Table 1402 summarizes the current and voltage waveforms of current transformers in different applications and their main characteristics.

Table 1402 Current and Voltage of Current Transformers in VSC Applications

Category Current Voltage Characteristics

CT2

Pure DC

High accuracy measurement

Harmonic measurement

For measurement, control and protection

Short step response time

CT3

DC voltage

DC current=0A

Harmonic measurement

Mainly used for protection

Table 1402 Current and Voltage of Current Transformers in VSC Applications (continued)

Category Current Voltage Characteristics

CT4a

Symmetrical monopole.

Asymmetric monopolar/bipolar.

pure AC voltage or

DC AC voltage

DC AC current

High accuracy measurement

Short step response time

CT4b

DC voltage

DC AC current

High accuracy measurement

Short step response time

Transformer Part 14.

Supplementary technical requirements for DC current transformers

1 Scope

This document specifies the terminology for a DC current transformer (DCCT) whose output signal can be analog or digital using any technology

and all supplementary technical requirements for definitions, ratings, design and construction, testing, etc.

This document applies to newly manufactured current transformers for measurement, protection and/or control in DC power systems with rated voltages greater than 1.5kV

sensor.

Note 1.Figure 601 of GB/T 20840.6-2017 describes the general configuration of single-pole low-power transformers.

This document does not apply to DCCTs used for current measurements on the VSC valve transistor branch (referred to in Figure 1403 and Table 1402

CT4a and CT4b).

Note 2.This will be considered in future revisions.

2 Normative references

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

documents, only the version corresponding to that date applies to this document; for undated references, the latest edition (including all amendments) applies to

this document.

Chapter 2 of GB/T 20840.6-2017 and the following supplementary content are applicable.

GB/T 2423.3 Environmental Test Part 2.Test Method Test Cab. Constant Damp Heat Test (GB/T 2423.3-

2016, IEC 60068-2-78.2012, IDT)

GB/T 3954 Electrician round aluminum rod

GB/T 5585.1 Copper, aluminum and their alloy busbars for electricians - Part 1.Copper and copper alloy busbars

GB/T 20840.6-2017 Transformers Part 6.Supplementary general technical requirements for low power transformers (IEC 61869-6.

2016, MOD)

GB/T 20840.8-2007 Transformers Part 8.Electronic Current Transformers (IEC 60044-8.2002, MOD)

GB/T 20840.9-2017 Transformer Part 9.Digital Interface of Transformer (IEC 61869-9.2016, MOD)

GB/T 26218.4-2019 Selection and dimensioning of high-voltage insulators used in dirty conditions - Part 4.For DC systems

insulator

3 Terms and Definitions

Chapter 3 of GB/T 20840.1-2010, Chapter 3 of GB/T 20840.6-2017 and Chapter 3 of GB/T 20840.9-2017

The defined terms and definitions, as well as the following additions and modifications, apply to this document.

......
This preview omits tables, figures, formulas and parts of the technical clauses. The complete document — all pages — is available in the English PDF.

Referenced standards

Normative references

GB/T 20840.6-2017 · GB/T 2423.3 · IEC 60068 · IEC 61869 · GB/T 20840.8-2007 · IEC 60044 · GB/T 20840.9-2017

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