关于耐压测试和Breakdown.
本帖被 fasten 执行加亮操作(2009-04-12)
[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!!
[ 此贴被大侠风清扬在2009-06-01 16:05重新编辑 ]
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