GB/T 16935.4-2011Insulation coordination for equipment within low-voltage systems -- Part 4: Consideration of high-frequency voltage stress (English PDF)

Foreword

GB/T 16935 Insulation coordination for equipment within low-voltage systems

consists of the following 4 parts.

- Part 1.Principles, requirements and tests;

- Part 3.Use of coating, potting or molding for protection against

pollution;

- Part 4.Consideration of high-frequency voltage stress;

- Part 5.Comprehensive method for determining clearances and

creepage distances equal to or less than 2 mm.

This Part is Part 4 of GB/T 16935.

This Part was drafted in accordance with the rules given in GB/T 1.1-2009.

This Part uses translation method of identically adopt IEC 60664-4.2005

Insulation coordination for equipment within low-voltage systems - Part 4.

Consideration of high-frequency voltage stress.

This Part shall be used in conjunction with GB/T 16935.1-2008 Insulation

coordination for equipment within low-voltage systems - Part 1.Principles

requirements and tests (IEC 60664-1.2007, IDT) and GB/T 16935.5-2008

Insulation coordination for equipment within low-voltage systems - Part 5.

Comprehensive method for determining clearances and creepage distances

equal to or less than 2 mm (IEC 60664-5.2007, IDT).

This Part was proposed by China Electrical Equipment Industrial Association.

This Part shall be under the jurisdiction of National Technical Committee on

Low-voltage Equipment with Insulation of Standardization Administration of

China (SAC/TC 417).

The drafting organization of this Part. Shanghai Electric Science Research

Institute.

Main drafters of this Part. Zhang Jianbing, Bao Ge, Wu Qingyun.

1 Scope

This Part of GB/T 16935 specifies the requirements for clearances, creepage

distances and solid insulation for equipment based upon their performance

criteria. It includes methods of electric testing with respect to insulation

coordination.

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 60112.2003, Method for determining the comparative and the proof

tracking indices of solid insulating materials under moist conditions

3 Terms and definitions

For the purposes of this document, the terms and definitions given in IEC

60664-1, as well as the following terms and definitions, apply.

generic term for both partial discharge inception voltage Ui and partial

discharge extinction voltage Ue

4 Clearances

As a conclusion from A.2.1, the critical frequency fcrit, at which the reduction of

the breakdown voltage occurs, depends upon the value of the clearance as

follows.

5 Creepage distances

Measuring data for three different frequency ranges up to 100 kHz, up to 1

MHz and up to 3 MHz are shown in Figure 2 (measurement) together with

limiting curves (dimensioning).

6 Solid insulation

The following method of dimensioning can be used instead of high-frequency

testing according to Clause 7.

7 High-frequency testing

If not otherwise specified by technical committees, the test shall be performed

with a new test specimen. Conditioning of the specimen by temperature and

humidity treatment is intended to

No breakdown shall occur during the test duration. After the test, no visible

damage (burning, melting etc.) shall occur.

8 Non sinusoidal voltages

For dimensioning of the clearances, the peak value of the non-sinusoidal

voltage and the repetition frequency of the voltage peaks are relevant.

In the case of a maximum voltage frequency of 10 MHz, if the field strength is

approximately uniform and no voids or air gaps are present in between the

solid insulation, the dimensioning procedure described in 6.3 may be applied

instead of testing.

Annex A

(Informative)

Insulation characteristics of clearances at high-frequency voltages

Breakdown of clearances usually occur in less than one microsecond. With

respect to that time scale, an a.c. voltage of power frequency has an

essentially constant amplitude.

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