关于耐压测试和Breakdown.
[原创]关于耐压测试和Breakdown.1. 本帖主要讨论耐压测试中如何判断Breakdown(主要是固体绝缘).
2. 引用标准 IEC 60243-1:1998, IEC 60664-1:2007, IEC 60335-1: 2001+A1:2004+A2:2006,
IEC 61180-1:1992 和IEC 61180-2:1994.
对于IEC 60335-1, 我想这是一本大家都比较熟悉的标准了, 就不多解释了. 下面介绍一下另外几本本标准.
IEC 61180-1 High-voltage test techniques for low-voltage equipment
Part 1: Definitions, test and procedure requirement
这本标准主要给出了一些定义测试环境,测试电压的要求和测试程序.
IEC 61180-2 High-voltage test techniques for low-voltage equipment - Part 2: Test equipment
这个是测试设备的要求
IEC 60664-1 Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
这本标准主要是讲固体绝缘特性之间的关系, 并给各个TC(技术委员会)制定标准给出了指导性的说明.
scope如下:
1 Scope and object
This part of IEC 60664 deals with insulation coordination for equipment within low-voltage
systems. It applies to equipment for use up to 2 000 m above sea level having a rated voltage
up to a.c. 1 000 V with rated frequencies up to 30 kHz, or a rated voltage up to d.c. 1 500 V.
It 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.
The minimum clearances specified in this standard do not apply where ionized gases occur.
Special requirements for such situations may be specified at the discretion of the relevant
technical committee.
This standard does not deal with distances
– through liquid insulation,
– through gases other than air,
– through compressed air.
NOTE 1 Insulation coordination for equipment within low-voltage systems with rated frequencies above 30 kHz is
given in IEC 60664-4.
NOTE 2 Higher voltages may exist in internal circuits of the equipment.
NOTE 3 Guidance for dimensioning for altitudes exceeding 2 000 m is given in Table A.2.
The object of this basic safety standard is to guide technical committees responsible for different equipment in order to rationalize their requirements so that insulation coordination is achieved.
It provides the information necessary to give guidance to technical committees when specifying clearances in air, creepage distances and solid insulation for equipment.
Care should be taken to see that manufacturers and technical committees are responsible for application of the requirements, as specified in this basic safety publication, or make reference to it, where necessary, in standards for equipment within their scope.
In the case of missing specified values for clearances, creepage distances and requirements for solid insulation in the relevant product standards, or even missing standards, this standard is applicable.
IEC 60243-1:1998 Electrical strength of insulating materials –Test methods –Part 1:Tests at power frequencies
这本标准讲的是关于在市电频率下进行耐压测试方法.
Scope 如下:
1.1 Scope
This part of IEC 60243 gives methods of test for the determination of the short-time electric strength of solid insulating materials at power frequencies, that is, those between 48 Hz and 62 Hz. It does not consider the testing of liquids and gases, although these are specified and used as impregnants or surrounding media for the solid insulating materials being tested.
NOTE – Methods for the determination of breakdown voltages along the surfaces of solid insulating materials are
included
3. 几种耐压测试.
IEC 60664-1中讲述了爬电距离, 电气间隙,固体绝缘和耐压测试之间的关系,其中主要使用的是脉冲电压(impulse voltage dielectric test),直流电压, 交流电压高频电压.而IEC 60335-1 主要使用的是交流电压来进行耐压测试的. 本帖的讨论主要以交流电压为主.
4. 耐压测试结果的判断
以IEC 60335-1的16.3条款为例, 耐压测试的判断结果的方式只有一个breakdown.
原文最后一句如下:
“No breakdown shall occur during the test.”
除了breakdown没有其他方式没有其他方式可以用来判断结果.
5. 关于breakdown的定义.
IEC 60335-1, IEC 61180-1 和IEC 61180-2中没有给出这个定义, 但是IEC 60243-1 和IEC 60664-1分别给出了定义. 对于跨标准引用定义是不合适的,但是在家电,灯具,工具,多媒体的各个IEC标准中都没有这个定义, 那么合适的定义只有从其参考的标准来看了.
IEC 60335-1 的条款2中将IEC 60664-1作为参考标准的.(不过是1992版的)
而IEC 60664-1 中的定义是
electrical breakdown
failure of insulation under electric stress when the discharge completely bridges the insulation, thus reducing the voltage between the electrodes almost to zero
除此之外没有更进一步的说明.
IEC 60243-1 作为IEC 60664-1的参考标准列入了条款2. 并且也给出了定义:
electric breakdown
severe loss of the insulating properties of test specimens while exposed to electric stress, which causes the current in the test circuit to operate an appropriate circuit-breaker
NOTE – Breakdown is often caused by partial discharges in the gas or liquid medium surrounding the test specimen and the electrodes which puncture the specimen beyond the periphery of the smaller electrode (or of both
electrodes, if of equal diameter).
这个两个定义很相似, IEC 60243-1中指出了绝缘击穿造成circuit breaker 动作, 但是这个circuit breaker 是不是很多网友所说的100mA动作的脱扣器呢? IEC 61180-2关于测试设备的要求中完全没有提到这个circuit breaker.关于这个100mA动作的脱扣器我稍后再解释,各位网友可以查一下自己的耐压测试设备, 一般情况这个100mA的脱扣器是一个通过电流传感动作的继电器.
IEC 60243-1中除了定义之外,在第10章给出了更详细的解释.
10 Criterion of breakdown
10.1 Electric breakdown is accompanied by an increase of current flowing in the circuit and by a decrease of voltage across the specimen. The increased current may trip a circuit-breaker or blow a fuse. However, tripping of a circuit-breaker may sometimes be influenced by flashover, specimen charging current, leakage or partial discharge currents, equipment magnetizing current or malfunctioning. It is therefore essential that the circuit-breaker is well co-ordinated with the characteristics of the test equipment and the material under test, otherwise the circuit breaker may operate without breakdown of the specimen, or fail to operate when breakdown has occurred and thus not provide a positive criterion of breakdown. Even under the best conditions, premature breakdowns in the ambient medium may occur, and observations shall be made to detect them during tests. If breakdowns in the ambient medium are observed, they shall be reported.
NOTE – For materials for which the sensitivity of the fault-detecting circuit is of particular significance, the standard for that material should so specify.
从这里可以看出circuit breaker动作和breakdown也没有直接的关系.
10.2 Where tests are made perpendicularly to the surface of a material, there is usually no doubt when breakdown has occurred and subsequent visual inspection readily shows the actual breakdown channel, whether this is filled with carbon or not.
Breakdown还需要找到哪个地方击穿了.
10.3 If in tests parallel to the surface it is required that failure by puncture and failure across the surface are differentiated (see 4.2), this can be done by examination of the specimen or in some cases by reapplying a voltage less than that of the first apparent breakdown. A convenient practice that has been found is the reapplication of half the breakdown voltage, followed by increasing the voltage until failure is reached by the same procedure as in the first test.
找不到哪个地方击穿了,用这个方法再次确认.
虽然无法确认这个脱扣器和这个circuit breaker 是不是同一个东西但是这个装置的动作是不能用来判定breakdown的.(如果有其他网友有这方面的资料,欢迎提出来一起讨论)
查了一下, 没有额定电流为100mA的断路器, (断路器上标的30mA是对漏电流的), 这个断路器应该是固定布线上的
6. 关于100mA的问题
关于这个100mA的问题也有很多人在讨论. 从IEC 60335-1的条款13.3来看.
“The high-voltage source used for the test is to be capable of supplying a short circuit current Is between the output terminals after the output voltage has been adjusted to the appropriate test voltage. The overload release of the circuit is not to be operated by any current below the tripping current Ir. The values of Is and Ir are given in Table 5 for various high-voltage sources.”
Table 5中指出对于4000V以下的, Is为200mA, Ir为100mA.其中200mA是以high-voltage sources(也即是耐压仪)的容量为 800VA来定的(IEC 61180-2要求的是100mA).100mA这里写得很清楚, 这个是过载装置的动作电流.而且也可以设置得比100mA高.这个装置的设定很明显是用来保护设备的.
关于routine test中动作电流的设定可以参考IEC 60664-1中条款6.1.5.2
6.1.5.2 Sampling and routine tests
Sampling tests and routine tests are intended to ensure production quality. It is the responsibility of the relevant technical committee, and in particular of the manufacturer, to specify these tests. They shall be carried out with the waveforms and voltage levels such that faults are detected without causing damage to the equipment (solid insulation or components).
Technical committees specifying sampling and routine tests shall in no case specify test voltages higher than those required for type testing.
所以你可以认为这个电流的设定是用来避免耐压击穿直接损坏产品(有的产品可是很贵的)
这里再讲一下，耐压测试中泄漏电流和击穿的关系：
如果耐压击穿则泄漏电流必然很大。（很大意味则超过100mA，也就很多人说的那个限值）。泄漏电流超过100mA，不一定击穿。
也就是说，泄漏电流大不是击穿的充分条件。
为了证明A+B不等于C，下面给出一个反例，也就是说泄漏超过100mA，耐压仪报警也不一定是击穿。
根据60950的
1.5.9.4 Bridging of basic insulation by a VDR
It is permitted to bridge BASIC INSULATION by a VDR provided that one side of the VDR is earthed in accordance with 2.6.1 a).
也就是说VDR是可以跨接在基本绝缘两侧的。如果我们进行针对基本绝缘的耐压测试，假设基本绝缘耐压1500V，VDR型号为S14K385MOV，测试中耐压仪报警并指示泄漏电流超过100mA,这时我们需要检验是不是真正击穿，重新对这个VDR测试耐压但是耐压调到500V，如果没有击穿说明VDR只是在耐压测试过程中动作了并没有击穿。
如果500V依然报警，说明VDR在先前测试中击穿。
回帖的讨论希望有标准和实验数据作为参考..
原创, 版权所有不得转载!!
楼主主要引用的IEC标准。
E文困难，又想了解其内容的可参考：
GB1408 （IEC 60243）
GB/T 16935 （IEC 60664）
GB/T 17627 （IEC 61180）
GB4706.1(iEC 60335-1) 高手啊, 受教了!
目前, 我所接触过的实验室都是以耐压测试时设备的过流触发电流100mA作为breakdown的判定依据的. 我想, 估计这是因为IEC60664-1中的定义中, 对breakdown的判断目前没有很统一的可实际操作的方式, 而100mA是一个比较直观量化的判断标准, 大家就将其作为一个默认的方式了.
在实际生产中, 安全标准上routine test通常只有规定耐压电压的一半, 但大部分工厂都将其测试电压提高到规定耐压值稍高一些, 同时将测试时间减短, 不知道LZ有没有此类变通方法的出处?
另外, 很多标准有提到Flashover, 不知LZ能否也给大家讲讲其定义和判断方式呢? 当人体流过100mA以上电流时，人就会呼吸困难，心脏停跳 对于击穿问题，目前还是没有很好的解析。 IEC 60335-1通用标准，要结合具体产品标准。13.3和16.3章测试的电压是不一样的。 要理解耐压测试中的Breakdown(绝缘击穿), 就必须了解几个概念.
首先, 我们来看看标准是如何定义绝缘击穿的.
GB4943(IEC60950) 5.2.2中描述到"当由于加上试验电压而引起的电流以失控的方式迅速增大,即绝缘无法限制电流时, 则认为已发生绝缘击穿. 电晕放电或单次瞬间闪络不认为是绝缘击穿." 从物理角度来理解, 就是施加到绝缘材料上的电压迅速降到接近0V, 而电流达到无穷大, 我们则认为该绝缘出现击穿了.
第二, 绝缘击穿(Breakdown)与短路(Short)的区别;
短路(short)是指电源输出端由导线直接闭合成回路. 对于耐压测试来说, 短路是绝缘非常严重的缺陷, 绝对不允许的. 然而, 我们经常将绝缘击穿与短路混淆. 那它们两者之间有何区别呢? 据试验表面, 绝缘击穿往往发生在电压施加过程中, 绝缘材料的电介质发生了变化, 而且造成施加电压的不稳定. 当电压超过了绝缘限制电流的临界点, 就会发生击穿的现象, 而且这种现象往往伴有瞬间闪络的情况发生. 而短路就是电源输出端直接导通;
第三, 在耐压测试时,如何判定绝缘击穿?
耐压测试的原理就是施加一高电压于绝缘上, 量测流经绝缘材料的电流值. 因此, 耐压测试是以漏电流值来判定产品的绝缘性能. 那么, 我们应该将漏电流设定为多少来判定产品的绝缘击穿呢? 在这里我们还需要了解2个概念----物理击穿&逻辑击穿. 物理击穿就是我们上面描述的定义, 而我们更多的情况以逻辑击穿来定义的, 就是在绝缘两端施加试验电压后, 流过绝缘的电流超过某个预定值; 我们通常以这个预定值(10mA, 100mA...)来判定产品绝缘是否"击穿". 绝缘击穿是永久性破坏，不能恢复, 之后即使施加1/2 或更低试验电压，仍然会击穿 IEC60335-1中电流的设置标准中是有写100mA，但是有些耐压测试仪是没有办法设置到100mA的，那么这种情况下设置多少合适呢?另外美标里面只写出了电压值，电流值却没有写，哪位大哥能告诉我在标准上哪里有写啊，或者应该设置多少合适。谢谢！ 请教一问题，电机的耐电压，1秒钟用多少伏的点？
