CB/T 1408 Insulating materials - Insulating materials - Test methods for electric strength includes the following three parts:
——Part 1: Tests 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 2 of GB/T 1408.
This part is drafted in accordance with the rules given in GB/T 1.1-2009.
This part replaces GB/T 1408.2-2006 Electrical strength of insulating materials - Test methods - Part 2: Additional requirements for tests using direct voltage; the following main technical changes have been made with respect to GB/T 1408.2-2006:
——The full text of GB/T 1408.1-2006 is modified to GB/T 1408.1-2016;
——10 cited documents including GB/T 1981.2-2003 are deleted;
——The contents of report is modified;
—— The “Bibliography” is added.
This part is identical with IEC 60243-2: 2013 Electric strength of insulating materials - Test methods - Part 2: Additional requirements for tests.(Edition 3)
This part was proposed by the China Electrical Equipment Industrial Association.
This part is under the jurisdiction of National Technical Committee on Insulating Materials of Standardization Administration of China (SAC/TC 301).
The previous editions of this part are as follows:
——GB/T 1408.2-2006.
Insulating materials - Test methods for electric strength - Part 2: Additional requirements for tests using direct voltage
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 direct voltage stress.
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 reference, the latest edition of the referenced documents (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.
4 Significance of the test
In addition to the requirements of Clause 4 of GB/T 1408.1-2016, the following points shall be considered when using direct-voltage tests.
For a non-homogeneous test specimen, with alternating voltage, the distribution of voltage stress within the test specimen is determined by impedance (largely capacitive). With an increasing direct voltage, the voltage distribution may still be largely capacitive but depends partly on the rate of voltage increase. The resistive voltage distribution, after constant voltage application, represents the steady-state condition. The choice between direct or alternating voltage depends upon the purpose for which the breakdown test is to be used and, to some extent, on the intended application of the material.
Upon direct voltage application, the following currents result: the capacitive current, the electric absorption current, the leakage current and, in some cases, partial discharge currents.
In addition, for materials with dissimilar layers or discontinuities, the voltage distribution across the test specimen is also influenced, as a result of interfacial polarization, by charges of opposite polarity, which may accumulate on the two sides of the interface and create local fields sufficiently strong to produce partial discharges and/or breakdown of the test specimens.
For most materials, the d.c. breakdown voltage is higher than the peak value of the power-frequency breakdown voltage; for many materials, particularly those which are non-homogeneous, the d.c. breakdown voltage will be three times higher than the a.c. breakdown voltage or even more.
5 Electrodes and 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 a power supply having the following characteristics and components.
A choice of voltage of either positive or negative polarity shall be provided, one of the connections to the electrodes being earthed.
The voltage ripple on the test voltage shall not exceed 2 % of the voltage at all values greater than 50 % of the breakdown voltage. The test voltage shall also be free from transients or other fluctuations exceeding 1 % of the applied voltage.
When testing test specimens of low capacitance, it may be necessary to add a suitable capacitor (for example, 1000 pF) in parallel with the electrodes in order to reduce the influence of transients in initiating premature breakdowns.
The controls on voltage shall be capable of varying the test voltage smoothly and uniformly between zero and the maximum test voltage and with the requested rate of voltage rise. The rate of voltage rise shall be controllable within ±20 % of the specified rate. Steps in voltage rise shall not exceed 2 % of the expected breakdown voltage value. Controls which automatically increase the voltage at a selectable rate are preferable.
A current-sensitive interrupting device shall be used for switching off the direct voltage source.
For many materials, a dangerous voltage may persist across the test specimen for a considerable time after the d.c. test voltage is removed. Disconnection of the power supply to the direct voltage source does not necessarily result in the output voltage or the voltage at the electrodes being reduced to zero. For this reason, it is essential that the electrodes be short-circuited and connected to earth for a period equal to minimum twice the total charging time to ensure that the charge is dissipated. For some large test specimens it will be necessary to maintain the shorted condition for 1 h or even longer.
A current-limiting resistance shall be used in series with the test specimen to prevent damage to the high-voltage supply and to limit as far as possible the damage to the electrodes on the test specimen when breakdown takes place. The maximum current permitted will depend on the material under test and on the amount of damage to the electrodes which can be tolerated.
Note: The use of a very high-valued resistor may result in breakdown voltages which are higher than those obtained with a lower-valued resistor.
When making tests where the value or increase in the value of the current is used as a criterion for breakdown, means of measurement of current through the test specimen shall be provided.
8.2 Voltage measurement
The measurement of applied voltage shall be made across the electrodes. The other requirements of Clause 8 of GB/T 1408.1-2016 shall be met.
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Significance of the test
5 Electrodes and specimens
6 Conditioning before tests
7 Surrounding medium
8 Electrical apparatus
9 Procedure
10 Mode of increase of voltage
11 Criterion of breakdown
12 Number of tests
13 Report
Bibliography
ICS 29.035.99
K 15
GB
中华人民共和国国家标准
GB/T 1408.2—2016/IEC 60243-2：2013
代替GB/T 1408.2—2006
绝缘材料 电气强度试验方法
第2部分：对应用直流电压试验的附加要求
Insulating materials—Test methods for electric strength—
Part 2：Additional requirements for tests using direct voltage
(IEC 60243-2：2013，Electric strength of insulating materials—
Test methods—Part 2：Additional requirements for tests
using direct voltage，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 发布
中国国家标准化管理委员会
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2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 1408.2—2006《绝缘材料电气强度试验方法 第2部分：对应直流电压试验的附加要求》，与GB/T 1408.2—2006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”；
——删除了GB/T 1981.2—2003等10个引用文件；
——修改了报告内容；
——增加了参考文献。
本部分使用翻泽法等同采用IEC 60243-2：2013《绝缘材料电气强度 试验方法 第2部分：对应用直流电压试验的附加要求》(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。
本部分所代替标准的历次版本发布情况为：
——GB/T 1408.2—2006。
绝缘材料 电气强度试验方法
第2部分：对应用直流电压试验的
附加要求
1 范围
GB/T 1408的本部分GB/T 1408.1补充了在直流电压应力下测定固体绝缘材料电气强度的要求。
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。
4 试验的意义
当应用直流电压试验时，除GB/T 1408.1—2016第4章要求外，还应考虑以下要求。
对于非均质试样，在交流电压下，试样内部电应力分布取决于阻抗(大部分为容性)。在升压过程中的直流电压下，电应力分布可能仍然大部分由容性阻抗决定，但这部分取决于升压速率。在直流电压稳定后，阻性电压分布则呈现稳定状态。选择直流或交流电压取决于拟采用的击穿试验的目的，在某种程度上还取决于材料被应用的场合。
在施加直流电压时，产生电容电流、电吸收电流、泄露电流以及在某种情况下局部放电电流。
此外，对含有不同层或不均匀的材料，在整个试样上的电压分布还受到因相反极性电荷而引起的界面极化影响。极性相反的电荷可能积聚在界面的两边，并产生足够大的局部电场。从而引起试验局部放电和/或击穿。
对于大多数材料，直流击穿电压高于工频击穿电压的峰值；对许多材料，特别是那些不匀质材料，直流击穿电压会比交流击穿电压高三倍或更多。
5 电极和试样
见GB/T 1408.1—2016第5章。
6 试验前的条件处理
见GB/T 1408.1—2016第6章。
7 周围媒质
见GB/T 1408.1—2016第7章。
8 电气设备
8.1 电源
施加于电极间的试验电压应由具有下列参数和元件的电源提供。
可以选择正或负极性电压，其中一个电极应接地。
在试验电压值大于50％击穿电压值的整个范围内，试验电压上的交变电压波纹应不超过试验电压的2％。试验电压还应没有超过1％施加电压的暂态或其他波动。
当测试电容值很小的试样时，有必要附加一个合适电容器(例如，1 000 pF)与电极并联，以减少暂态预击穿的影响。
控制电压装置应能平滑均匀地从零调节到最大试验电压，并具有所要求的升压速度。升压速度应能控制在规定速度的±20％以内。电压上升的每一个阶跃量应不超过预期击穿电压的2％，优选能在某一选择速度下自动升压的控制装置。
应使用电流感应式的断路装置来切断直流电压源。
对许多材料，在移除直流试验电压后的相当长的时间内，在整个试样上可能继续存在着危险电压，切断接到直流电压源的工频电源未必会导致输出电压或电极处电压降到零。由于这个原因，应将两电极短路并接地，其时间最少等于两倍的总充电时间，以确保电荷消失。对某些大的试样，有必要保持短路状态1h或更长时间。
最好应用限流电阻与试样串联，以防止试样发生击穿时对高压电源造成损坏并尽可能限制对试样上电极造成损坏。最大允许电流将取决于被试材料以及允许的对电极造成损坏的程度。
注：应用某种很高值的电阻器可能导致击穿电压比应用低值电阻器的时击穿电压高。
当进行的试验是以电流值或以电流的增加值为击穿判断标准时，应具有测量通过试样的电流的装置。
8.2 电压测量
应在电极两端测量所施加的电压，并满足GB/T 1408.1—2016第8章的其他要求。
9 程序
见GB/T 1408.1—2016第9章。
10 升压方式
除非另有规定，应按GB/T 1408.1—2016的10.1(短时试验)、10.3或10.5(慢速和很慢速升压)或10.6(检查试验)施加电压。
11 击穿判断标准
GB/T 1408.1—2016第11章适用于直流电压试验。可以通过电流突变或者电流超过某一规定值判断击穿。
12 试验次数
见GB/T 1408.1—2016第12章。
13 报告
除非另有规定，报告应包括以下内容：
a) 被试材料的完整鉴别，试样描述和制备方法；
b) 试验电压的极性；
c) 电气强度和/或击穿电压的中值；
d) 每一试样的厚度(见GB/T 1408.1—2016的5.4)；
e) 试验过程的周围媒质及其性能；
f) 电极系统；
g) 施加电压的方式；
h) 电气强度和/或击穿电压的各个值；
i) 在空气或其他气体中试验过程的温度、压力和湿度；或当周围媒质是液体时，该媒质的温度；
j) 试验前的条件处理；
k) 击穿类型和位置的说明。
参考文献
[1] IEC 60674-2，Specification for plastic films for electrical purposes—Part 2：Methods of test
[2] IEC/TR 60727-1：1982，Evaluation of electrical endurance of electrical insulation systems—Part 1：General considerations and evaluation procedures based on normal distributions
[3] (withdrawn)
[4] IEC/TR 60727-2：1993，Evaluation of electrical endurance of electrical insulation systems—Part 2：Evaluation procedures based on extreme-value distributions(withdrawn)
[5] IEC 62539：2007，Guide for the statistical analysis of electrical insulation breakdown data
[6] IEEE 930-1987(R1995)，IEEE guide for statistical analysis of electrical insulation voltage endurance data(Available from IEEE Operations Center，445 Hoe Lane，P.O. Box 1331
[7] Piscataway，NJ 08855-1331，USA，or in some countries outside the USA，from local offices of the Global Info Center)
[8] Special Technical Publication 926，Engineering Dielectrics，Volume IIB：Electrical Properties of Solid Insulating Materials：Measurement Techniques—Chapter 7：Statistical Methods for the Evaluation of Electrical Insulating Systems，American Society for Testing and Materials，100 Barr Harbor Drive，West Conshohocken，PA 19428-2959，USA
