GB/T 1408.1-2016Insulating materials -- Test methods for electric strength -- Part 1: Test at power frequencies (English PDF)

Foreword

GB/T 1408 Insulating Materials – Test Methods for Electric Strength can be divided

into the following 3 parts.

--- Part 1.Test at Power Frequencies;

--- Part 2.Additional Requirements for Tests Using Direct Voltage;

--- Part 3.Additional Requirements for 1.2/50µs Impulse Tests.

This Part belongs to Part 1 of GB/T 1408.

This Part replaced GB/T 1408.1-2006 Electrical Strength of Insulating Materials - Test

Methods - Part 1.Tests at Power Frequencies. Compared with GB/T 1408.1-2006, this

Part has the major technical changes as follows.

--- Modify "Normative References" (see Clause 2 of this Edition; Clause 2 of 2006

Edition);

--- Add the test requirements for "sphere-plate electrode" (see 5.2.1.3 of this Edition);

--- Add the test requirements for "elastomer" (see 5.2.6.2.4 of this Edition);

--- Add "test in solid materials" (see 7.4 of this Edition);

--- Add schematic diagram of "sphere-plate electrode" [see Figure 1c) of this Edition];

--- Delete Annex B (see Annex B of 2006 Edition).

This Part uses translation method to equivalently adopt IEC 60243-1.2013 Electric

Strength of Insulating Materials – Test Methods – Part 1.Tests at Power Frequencies

(3rd Edition).

The Chinese documents that have a consistency relationship with the international

documents quoted in the Normative References of this Part are as follows.

--- GB/T 1981.2-2009 Varnishes Used for Electrical Insulation - Part 2.Methods of

Test (IEC 60464-2.2001, MOD)

--- GB 2536-2011 Fluids for Electrotechnical Applications - Unused Mineral

Insulating Oils for Transformers and Switchgear (IEC 60296.2003, MOD)

--- GB/T 5471-2008 Plastics - Compression Molding of Test Specimens of

Thermosetting Materials (ISO 295.2004, IDT)

--- GB/T 7113.2-2014 Flexible Insulating Sleeving - Part 2.Methods of Test (IEC

60684-2.2003, MOD)

--- GB/T 9352-2008 Plastic - Compression Moulding of Test Specimens of

Thermoplastic Materials (ISO 293.2004, IDT)

--- GB/T 10580-2015 Standard Conditions for Use Prior to and During the Testing

of Solid Electrical Insulating Materials (IEC 60212.2010, IDT)

--- GB/T 15022.2-2007 Resin Based Reactive Compounds Used for Electrical

Insulation - Part 2.Methods of Test (IEC 60455-2.1998, MOD)

--- GB/T 17037.3-2003 Plastics - Injection Moulding of Test Specimens of

Thermoplastic Materials - Part 3.Small Plates (ISO 294-3.2002, IDT)

--- GB/T 21218-2007 Specifications for Unused Silicone Insulating Liquids for

Electrotechnical Purposes (IEC 60836.2005, IDT)

This Part was proposed by China Electrical Equipment Industrial Association.

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

Standardization of Electrical Insulation Materials and Insulation System Evaluation

(SAC/TC 301)

Drafting organizations of this Part. Suzhou Taihu Electric Advanced Material Co., Ltd.;

Yantai Metastar Special Paper Co., Ltd.; Machinery Industry Beijing Electrotechnical

Institute of Economic Research; Shanghai Electric Cable Research Institute; Zhuzhou

Times Electric Insulation Co., Ltd.; and Guilin Electrical Equipment Scientific Research

Institute Co., Ltd.

Chief drafting staffs of this Part. Wu Hao, Zhang Chunqi, Guo Zhenyan, Wang Dianxin,

Xu Xiaofeng, Xia Junfeng, Liu Yali, Zeng Zhi, Zhang Junha, Wang Yiliang, Wu Bin, and

Wang Xianfeng.

The historical editions replaced by this Standard are as follows.

--- GB/T 1408-1978, GB/T 1408-1989, GB/T 1408.1-1999, GB/T 1408.1-2006.

Insulating Materials - Test Methods for Electric

Strength - Part 1.Test at Power Frequencies

1 Scope

This Part of GB/T 1408 provides test methods for the determination of short-time

electric strength of solid insulating materials at power frequencies between 48 Hz and

62 Hz.

2 Normative References

The following documents are essential to the application of this document. For the

dated documents, only the versions with the dates indicated are applicable to this

document; for the undated documents, only the latest version (including all the

amendments) are applicable to this document.

ISO 293 Plastics – Compression Moulding of Test Specimens of Thermoplastic

Materials

ISO 294-1 Plastics – Injection Moulding of Test Specimens of Thermoplastic

Materials – Part 1.General Principles, and Moulding of Multipurpose and Bart Test

Specimens

3 Terms and Definitions

For the purposes of this document, the following terms and definitions apply.

Loss of the insulating properties of the gas or liquid medium surrounding a test

specimen and electrodes while exposed to electric stress, which causes the current in

the test circuit to operate an appropriate circuit-breaker.

Quotient of the breakdown voltage and the distance between the electrodes between

which the voltage is applied under the prescribed test conditions.

4 Significance of the Test

Electric strength test results obtained in accordance with this standard are useful for

detecting changes or deviations from normal characteristics resulting from processing

variables, ageing conditions or other manufacturing or environmental situations.

Materials with high electric strength will not necessarily resist long-term degradation

processes such as heat, erosion or chemical deterioration by partial discharges, or

electrochemical deterioration in the presence of moisture, all of which may cause

failure in service at much lower stress.

5 Electrodes and Specimens

If a fixture is employed, which accurately aligns upper and lower electrodes within 1.0

mm, the diameter of the lower electrode may be reduced to (25.0±1.0) mm, the

diameters of the two electrodes differing by no more than 0.2 mm, as shown in Figure

1b).

The outer electrode shall be a band of metal foil (75.0±1.0) mm wide and the inner

electrode, a disk of metal foil (25.0±1.0) mm in diameter, flexible enough to conform

with the curvature of the cylinder. The arrangement is shown in Figure 3.

Two parallel holes are drilled perpendicularly to the surface, with centers (25±1) mm

apart and of such a diameter that, after reaming with a reamer having a taper of

approximately 2 %, the diameter of each hole at the larger end is not less than 4.5 mm

and not greater than 5.5 mm.

6 Conditioning before Tests

The electric strength of insulating materials varies with temperature and moisture

content. Where a specification is available for the material to be tested, this shall be

followed.

7 Surrounding Medium

If it is intended that the tests evaluate the behavior of a material in another medium,

that medium may be used.

Tests at elevated temperature may be made either in a container of liquid in an oven

(see 7.1) or in a thermostatically controlled bath using the insulating liquid for heat

transfer. In this case, suitable means for circulating the liquid, so that the temperature

is substantially uniform and maintained within ±2°C of the specified temperature

around the test specimen, shall be provided.

8 Electrical Apparatus

to 5 kVA for voltages up to 100 kV.

The controls on the variable low-voltage source shall be capable of varying the test

voltage smoothly, uniformly and without overshoots. When applying voltage in

accordance with Clause 8, the incremental increase produced, e.g. by a variable

autotransformer, shall not exceed 2 % of the expected breakdown voltage.

It is desirable for the reading that the maximum applied test voltage be retained on the

voltmeter after breakdown so that the breakdown voltage can be accurately read and

recorded, but the indicator shall not be sensitive to transients which can occur at

breakdown.

9 Procedure

The document calling for the test shall state the following.

Electrodes complying with Clause 5 shall be applied to the specimen in such a manner

that damage to the specimen is avoided. Using apparatus providing a voltage

complying with Clause 8, a voltage is applied between the electrodes and increased

in accordance with 10.1 to 10.5.It is observed whether specimens suffer breakdown

or flashover (see Clause 11).

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