GB/T 1408 Insulating Materials - Test Methods for Electric Strength is classified into the following three 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 is Part 3 of GB/T 1408.
This part is developed according to the rules specified in GB/T 1.1-2009.
This part replaces GB/T 1408.3-2007 Insulating Materials - Test Methods for Electric Strength - Part 3: Additional Requirements for 1.2/50μs Impulse Tests; the following technical changes have been made with respect to GB/T 1408.3-2007 (the previous edition):
——"GB/T 1408.1-2006" is revised as "GB/T 1408.1-2006" in full text;
——The word “impulse” (脉冲) in full text is changed to “impulse” (冲击);
——The word "virtual" (虚) in Terms is changed to "virtual" (视在) (see 3.3~3.6, 3.3~3.6 of edition 2007);
——Terms "impulse breakdown voltage" and "withstand voltage" are added (see 3.7 and 3.8);
——"Report content" is modified.
The translation method used in this part is identical to IEC 60243-3: 2013 Electric Strength of Insulating Materials - Test Methods - Part 3: Additional Requirements for 1,2/50 μs Impulse Tests (edition 3).
This standard was proposed by the China Electrical Equipment Industrial Association.
This part is under the jurisdiction of SAC/TC 301 Technical Committee on National Electrical Insulating Material and Insulation System Evaluation of Standardization Administration of China.
The previous edition of the standard superseded by this part is:
——GB/T 1408.3-2007.
Insulating Materials - Test Methods for Electric Strength -
Part 3: Additional Requirements for 1.2/50μs Impulse Tests
1 Scope
This part of GB/T 1408 gives requirements additional to those in GB/T 1408.1 for the determination of the electric strength of solid insulating materials under 1,2/50 µs impulse voltage stress.
2 Normative References
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
GB/T 1408.1-2016 Insulating Materials - Test Methods for Electric Strength - Part 1: Test at Power Frequencies (IEC 60243-1: 2013, IDT)
3 Terms and Definitions
For the purposes of this document, the terms and definitions given in GB/T 1408.1-2016 apply.
3.1
full impulse-voltage wave
aperiodic transient voltage that rises rapidly to a maximum value, then falls less rapidly to zero (see Figure 1)
3.2
peak value of an impulse-voltage wave
Up
maximum value of voltage
3.3
virtual peak value of an impulse-voltage wave
U1
value derived from a recording of an impulse-voltage wave on which high-frequency oscillations, or overshoot of a limited magnitude, may be present
3.4
virtual origin of an impulse-voltage wave
O1
point of intersection O1 with the line of zero voltage of a line drawn through the points of 0,3 and 0,9 times the virtual peak value on the front of an impulse-voltage wave
3.5
virtual front time of an impulse-voltage wave
t1
equal to 1,67 times the interval tf between the instants when the voltage is 0,3 and 0,9 times the peak value (tf, Figure 1)
3.6
virtual front time to half-value
t2
time interval t2 between the virtual origin O1 and the instant on the tail when the voltage has decreased to half the peak value
3.7
impulse breakdown voltage
nominal peak voltage that the wave causing breakdown would have reached if breakdown had not occurred
3.8
withstand voltage
highest nominal peak voltage of a set of three impulses which did not cause breakdown
Figure 1 Full Impulse-voltage Wave
4 Significance of the Test
In addition to the information of Clause 4 of GB/T 1408.1-2016, the following points are of importance in connection with impulse-voltage tests.
High-voltage equipment may be subjected to transient voltage stresses resulting from such causes as nearby lightning strokes. This is particularly true of apparatus such as transformers and switchgears used in electrical power transmission and distribution systems. The ability of insulating materials to withstand these transient voltages is important in establishing the reliability of apparatus insulated with these materials.
Transient voltages caused by lightning may be of either positive or negative polarity. In a symmetrical field between identical electrodes, the polarity has no effect on the electric strength. However, with dissimilar electrodes, there may be a pronounced polarity effect. When asymmetrical electrodes are used for testing materials with which the tester has no previous experience or knowledge, it is recommended that comparative tests be made with both directions of polarity.
The standard wave shape is a 1,2/50 µs wave, reaching peak voltage in approximately 1,2 µs, and decaying to 50 % of peak value in approximately 50 µs after the beginning of the wave. This wave is intended to simulate a lightning stroke that may strike a system without breakdown.
Note: if the object being tested has appreciable inductive characteristics, it may be difficult or impossible to attain the specified wave shape with less than 5 % oscillations, as prescribed in 8.2. However, the procedures given in this standard are for capacitive specimen only. Testing of more complex configurations, such as between coils of completed apparatus or models of such apparatus, should be performed in accordance with the specifications for that apparatus.
Because of the short time involved, dielectric heating, other thermal effects and the influence of injected space-charges may be reduced during impulse testing of most materials. Thus, impulse tests usually give higher values than the peak voltage of short-term ac tests. From comparisons of the impulse electric strength with the values drawn from longer time tests, inferences may be drawn as to the modes of failure under the various tests for a given material.
5 Electrodes and Test Specimens
Clause 5 of GB/T 1408.1-2016 is applicable.
6 Conditioning before Tests
Clause 6 of GB/T 1408.1-2016 is applicable.
7 Surrounding Medium
Clause 7 of GB/T 1408.1-2016 is applicable.
8 Electrical Apparatus
8.1 Voltage source
The test voltage applied to the electrodes shall be provided by an impulse generator having the following characteristics.
A choice of either positive or negative polarity shall be provided, one of the connections to the electrodes being earthed.
Controls within the generator shall be capable of adjusting the shape of the wave applied to the test specimen under test to have a virtual front time t1 of (1,2 ± 0,36) µs, and virtual time to half-value t2 of (50 ± 10) µs (see Figure 1).
The voltage capability and energy-storage capacity of the generator shall be sufficient to apply impulse waves of the proper shape to any test specimens to be tested, up to the breakdown voltage or specified proof voltage of the material.
The peak value of the voltage is taken as the virtual peak value, provided that the conditions of 8.2 are satisfied.
Foreword i 1 Scope 2 Normative References 3 Terms and Definitions 4 Significance of the Test 5 Electrodes and Test Specimens 6 Conditioning before Tests 7 Surrounding Medium 8 Electrical Apparatus 9 Procedure 10 Application of Voltage 11 Criterion of Breakdown 12 Number of Tests 13 Report
绝缘材料 电气强度试验方法 第3部分：1.2/50μs冲击试验补充要求 Insulating materials—Test methods for electric strength— Part 3：Additional requirements for 1.2/50μs impulse tests (IEC 60243-3：2013，Electric strength of insulating materials— Test methods—Part 3：Additional requirements for 1.2/50 μs impulse tests，IDT)
2016-12-13发布 2017-07-01实施
中华人民共和国国家质量监督检验检疫总局 中国国家标准化管理委员会 发布
前言 GB/T 1408《绝缘材料 电气强度试验方法》分为以下三个部分： ——第1部分：工频下试验； ——第2部分：对应用直流电压试验的附加要求； ——第3部分：1.2/50μs冲击试验补充要求。 本部分为GB/T 1408的第3部分。 本部分按照GB/T 1.1—2009给出的规则起草。 本部分代替GB/T 1408.3—2007《绝缘材料电气强度试验方法 第3部分：1.2/50μs脉冲试验补充要求》，与GB/T 1408.3—2007相比主要技术变化如下： ——全文将“GB/T 1408.1—2006”修改为“GB/T 1408.1—2016”； ——将全文中的“脉冲”改为“冲击”； ——将术语中的“虚”改为“视在”(见3.3~3.6，2007年版的3.3~3.6)； ——增加了“冲击击穿电压”和“耐受电压”术语(见3.7和3.8)； ——修改了“报告内容”。 本部分使用翻译法等同采用IEC 60243-3：2013《绝缘材料电气强度 试验方法 第3部分：1.2/50μs冲击试验补充要求》(第3版)。 本部分由中国电器工业协会提出。 本部分由全国电气绝缘材料与绝缘系统评定标准化技术委员会(SAC/TC 301)归口。 本部分起草单位：机械工业北京电工技术经济研究所、嘉兴市新大陆机电有限公司、佛山市顺德区质量技术监督标准与编码所、桂林电器科学研究院有限公司、北京北重汽轮电机有限责任公司。 本部分主要起草人：刘亚丽、陆云峰、陈昊、吴化军、周到、刘晖、王先锋、刘凤娟。 本部分所代替标准的历次版本发布情况为： ——GB/T 1408.3-2007。 绝缘材料 电气强度试验方法 第3部分：1.2/50μs冲击试验补充要求 1 范围 GB/T 1408的本部分对GB/T 1408.1补充了在1.2/50μs冲击电压应力下，对固体绝缘材料电气强度测定的补充要求。 2 规范性引用文件 下列文件对于本文件的应用是必不可少的。凡是注日期的引用文件，仅注日期的版本适用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改单)适用于本文件。 GB/T 1408.1—2016 绝缘材料 电气强度试验方法 第1部分：工频下试验(IEC 60243-1：2013，IDT) 3 术语和定义 GB/T 1408.1-2016界定的术语和定义适用于本文件。 3.1 全冲击电压波 full impulse-voltage wave 迅速升到最大值，然后迅速回落到零的非周期性暂态电压(见图1)。 3.2 冲击电压峰值 peak value of an impulse-voltage wave Up 电压的最大值。 3.3 冲击电压波视在峰值 virtual peak value of an impulse-voltage wave U1 从一个具有高频振荡或限制量级过冲的冲击电压波形记录中衍生的数值。 3.4 冲击电压波视在电压起始点 virtual origin of an impulse- voltage wave O1 交点O1是一条在冲击电压波前端，通过0.3倍视在峰值和0.9倍视在峰值的直线与零电压的交点。 3.5 冲击电压波的视在波前时间 virtual front time of an impulse- voltage wave t1 t1 的1.67倍，其中t1是0.3倍与0.9倍峰值之间的时间间隔(t1见图1)。 3.6 冲击电压波的视在半峰值时间 virtual front time to half-value t2 视在电压起始点O1和当电压下降到峰值一半时与波尾交点之间的时间间隔。 3.7 冲击击穿电压 impulse breakdown voltage 未击穿情况下，冲击波导致击穿产生的标称峰值电压。 3.8 耐受电压 withstand voltage 未引发击穿的一组三个冲击的最高标称峰值电压。
