A non-linear overvoltage limiter (hereinafter referred to as a surge arrester), regardless of the voltage value, is subject to mandatory tests. This product can be used for protection against switching overvoltages and applied in electrical installations with voltages of 0.4 kV, 6 kV, 10 kV, 35 kV, 110 kV and above. Depending on the operating voltage, tests are regulated by different regulatory documents. For example, IEC 60099-4: 2004 is an international standard, as well as GOST R 52725 - 2007 approved on its basis and in force. A variety of technical conditions and GOSTs for checking high-voltage equipment are also taken into account. In this article, we will briefly review the methods, standards and scope of testing arresters.
Content:
- The importance of testing
- Measurement of the conduction current
- Insulation resistance measurement
The importance of testing
Perhaps the main regulatory document that we use and which we most often encounter in the production of acceptance tests is the PUE. With regard to overvoltage arresters, it contains chapter 1.8, and specifically paragraph 1.8.3. It sets the standards and scope of tests for surge arresters and valve arresters.
In addition to acceptance tests, in accordance with the above documents, the following tests can be carried out:
- periodic;
- qualification;
- typical.
The qualification check of these devices is needed in order to determine whether the enterprise is ready to manufacture products in a given volume. This applies to the first industrial series or the pilot batch. An important step here is the explosion safety check. During the operation of the arrester, due to the influence of various factors, one of which is the off-design mode of use, an increased pressure may occur inside it. As a result, an explosion is possible, which entails damage to equipment that is installed nearby, as well as, most importantly, people working at the facility.
Let's take a closer look at the acceptance tests. As noted above, they are regulated by Chapter 1.8 of the PUE p. 1.8.3. If we combine all the data from it, we get a convenient table:
Thus, for surge arresters, there is a method for measuring resistance and conduction current. We will consider below how to check these parameters.
Measurement of the conduction current
The picture shows various connection diagrams for testing surge arresters related to the measurement of conduction current:
Basically, the manufacturer specifies the standard value of the conduction current in the technical data sheet for the product. This value is taken on the basis of tests carried out at the enterprise and directly depends on the highest continuous voltage applied.
The current is measured with an ammeter or milliammeter. A laboratory power supply is connected to the terminals of the assembled circuit. When the load is applied, current measurements are taken. The load must correspond to the value of the highest permissible continuous voltage.
It should be noted that the work should be carried out at a steady ambient temperature of 20 ± 15 ° С, at overvoltage arresters that have been cleaned and wiped dry, which must first be disconnected from networks.
Insulation resistance measurement
Based on the data given in the above table, it can be seen that when testing surge arresters up to 3 kV, it is necessary to use a 1000 V megohmmeter, if over 3 kV, a 2500 V megohmmeter is needed. The measured resistance for arresters up to 3 kV must be above 1000 mΩ, with a voltage of 3 to 35 kV - must be within the manufacturer's recommended value, above 110 kV - should be at least 3000 mΩ, at the same time the result should not differ by more than ± 30% from the previously performed tests or the values specified by the manufacturer.
About, how to use a megohmmeter correctly, we told in the corresponding article, which we strongly recommend to read!
Remember that only an electrical laboratory that has a certificate for carrying out this type of activity can guarantee the safe and high-quality performance of work. At the end of the measurements, a test report for the arrester is drawn up. It indicates the name and type of the limiter, the values of measurements of the insulation resistance and conduction current, weather conditions, as well as the instruments with which the measurements were made. A sample protocol is shown below:
Finally, we recommend that you familiarize yourself with the useful material provided in the video (the quality of the video is not very good, but nevertheless the information is presented clearly):
That's all we wanted to tell you about the arrester test method. Now you know how the work is carried out and why it needs to be done!
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