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
中華人民共和國國家標準
GB/T 1408.2—2016/IEC 60243-2：2013
代替GB/T 1408.2—2006
絕緣材料 電氣強度試驗方法
第2部分：對應用直流電壓試驗的附加要求
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發布 2017-07-01實施
中華人民共和國國家質量監督檢驗檢疫總局 發布
中國國家標準化管理委員會
前言
GB/T 1408《絕緣材料 電氣強度試驗方法》分為以下三個部分：
——第1部分：工頻下試驗；
——第2部分：對應用直流電壓試驗的附加要求；
——第3部分：1.2/50μs沖擊試驗補充要求。
本部分為GB/T 1408的第2部分。
本部分按照GB/T 1.1—2009給出的規則起草。
本部分代替GB/T 1408.2—2006《絕緣材料電氣強度試驗方法 第2部分：對應直流電壓試驗的附加要求》，與GB/T 1408.2—2006相比主要技術變化如下：
——全文將GB/T 1408.1—2006修改為“GB/T 1408.1—2016”；
——刪除了GB/T 1981.2—2003等10個引用文件；
——修改了報告內容；
——增加了參考文獻。
本部分使用翻澤法等同采用IEC 60243-2：2013《絕緣材料電氣強度 試驗方法 第2部分：對應用直流電壓試驗的附加要求》(第3版)。
本部分由中國電器工業協會提出。
本部分由全國電氣絕緣材料與絕緣系統評定標準化技術委員會(SAC/TC 301)歸口。
本部分所代替標準的歷次版本發布情況為：
——GB/T 1408.2—2006。
絕緣材料 電氣強度試驗方法
第2部分：對應用直流電壓試驗的
附加要求
1 范圍
GB/T 1408的本部分GB/T 1408.1補充了在直流電壓應力下測定固體絕緣材料電氣強度的要求。
2 規范性引用文件
下列文件對于本文件的應用是必不可少的。凡是注日期的引用文件，僅注日期的版本適用于本文件。凡是不注日期的引用文件，其最新版本(包括所有的修改單)適用于本文件。
GB/T 1408.1—2016 絕緣材料 電氣強度試驗方法 第1部分：工頻下試驗(IEC 60243-1：2013，IDT)
3 術語和定義
GB/T 1408.1—2016界定的術語和定義適用于本文件。
4 試驗的意義
當應用直流電壓試驗時，除GB/T 1408.1—2016第4章要求外，還應考慮以下要求。
對于非均質試樣，在交流電壓下，試樣內部電應力分布取決于阻抗(大部分為容性)。在升壓過程中的直流電壓下，電應力分布可能仍然大部分由容性阻抗決定，但這部分取決于升壓速率。在直流電壓穩定后，阻性電壓分布則呈現穩定狀態。選擇直流或交流電壓取決于擬采用的擊穿試驗的目的，在某種程度上還取決于材料被應用的場合。
在施加直流電壓時，產生電容電流、電吸收電流、泄露電流以及在某種情況下局部放電電流。
此外，對含有不同層或不均勻的材料，在整個試樣上的電壓分布還受到因相反極性電荷而引起的界面極化影響。極性相反的電荷可能積聚在界面的兩邊，并產生足夠大的局部電場。從而引起試驗局部放電和/或擊穿。
對于大多數材料，直流擊穿電壓高于工頻擊穿電壓的峰值；對許多材料，特別是那些不勻質材料，直流擊穿電壓會比交流擊穿電壓高三倍或更多。
5 電極和試樣
見GB/T 1408.1—2016第5章。
6 試驗前的條件處理
見GB/T 1408.1—2016第6章。
7 周圍媒質
見GB/T 1408.1—2016第7章。
8 電氣設備
8.1 電源
施加于電極間的試驗電壓應由具有下列參數和元件的電源提供。
可以選擇正或負極性電壓，其中一個電極應接地。
在試驗電壓值大于50％擊穿電壓值的整個范圍內，試驗電壓上的交變電壓波紋應不超過試驗電壓的2％。試驗電壓還應沒有超過1％施加電壓的暫態或其他波動。
當測試電容值很小的試樣時，有必要附加一個合適電容器(例如，1 000 pF)與電極并聯，以減少暫態預擊穿的影響。
控制電壓裝置應能平滑均勻地從零調節到最大試驗電壓，并具有所要求的升壓速度。升壓速度應能控制在規定速度的±20％以內。電壓上升的每一個階躍量應不超過預期擊穿電壓的2％，優選能在某一選擇速度下自動升壓的控制裝置。
應使用電流感應式的斷路裝置來切斷直流電壓源。
對許多材料，在移除直流試驗電壓后的相當長的時間內，在整個試樣上可能繼續存在著危險電壓，切斷接到直流電壓源的工頻電源未必會導致輸出電壓或電極處電壓降到零。由于這個原因，應將兩電極短路并接地，其時間最少等于兩倍的總充電時間，以確保電荷消失。對某些大的試樣，有必要保持短路狀態1h或更長時間。
最好應用限流電阻與試樣串聯，以防止試樣發生擊穿時對高壓電源造成損壞并盡可能限制對試樣上電極造成損壞。最大允許電流將取決于被試材料以及允許的對電極造成損壞的程度。
注：應用某種很高值的電阻器可能導致擊穿電壓比應用低值電阻器的時擊穿電壓高。
當進行的試驗是以電流值或以電流的增加值為擊穿判斷標準時，應具有測量通過試樣的電流的裝置。
8.2 電壓測量
應在電極兩端測量所施加的電壓，并滿足GB/T 1408.1—2016第8章的其他要求。
9 程序
見GB/T 1408.1—2016第9章。
10 升壓方式
除非另有規定，應按GB/T 1408.1—2016的10.1(短時試驗)、10.3或10.5(慢速和很慢速升壓)或10.6(檢查試驗)施加電壓。
11 擊穿判斷標準
GB/T 1408.1—2016第11章適用于直流電壓試驗。可以通過電流突變或者電流超過某一規定值判斷擊穿。
12 試驗次數
見GB/T 1408.1—2016第12章。
13 報告
除非另有規定，報告應包括以下內容：
a) 被試材料的完整鑒別，試樣描述和制備方法；
b) 試驗電壓的極性；
c) 電氣強度和/或擊穿電壓的中值；
d) 每一試樣的厚度(見GB/T 1408.1—2016的5.4)；
e) 試驗過程的周圍媒質及其性能；
f) 電極系統；
g) 施加電壓的方式；
h) 電氣強度和/或擊穿電壓的各個值；
i) 在空氣或其他氣體中試驗過程的溫度、壓力和濕度；或當周圍媒質是液體時，該媒質的溫度；
j) 試驗前的條件處理；
k) 擊穿類型和位置的說明。
參考文獻
[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
