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Why do you want to carry out the Sichuan Electric Power annual inspection pre test, the electric Spirit tells you

Classification: FAQ ; release time: ; December 16, 2019 ; Author: Electric Genie
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Why is preventive testing of electrical equipment important? next Sichuan Electric Power annual inspection pre test company Give you an analysis!

1、 The position and function of pre test

1. Pre test is safe operation of power equipment**

The primary problem of safe operation of power equipment is to ensure the safety of power equipment and the reliability of relay protection. This is not only for the power equipment that has been put into operation, but also for the newly-built power equipment, although the handover acceptance test has been carried out at the time of delivery, the pre test is also very necessary. For the power equipment which has been used for many years, whether it can continue to be put into operation depends on the scientific conclusion provided by the pre test. When the power equipment is in long-term operation, its technical performance will gradually decrease, while in the state of intermittent operation or long-term shutdown, its insulation characteristics and mechanical properties will also deteriorate due to the influence of temperature, humidity, dust and other environmental factors. Only through pre-test can we determine whether these equipment can operate safely. According to the analysis of the pre test data, the equipment can be updated and repaired orderly according to the priority, so as to ensure the safe operation of the equipment.

 Sichuan Electric Power annual inspection and pre test company

2. Pre test is the premise of classified management of power equipment

Power equipment management is the same as equipment management in other industries or departments. It is often necessary to check the equipment and classify it according to its performance, which is dynamic. Similarly, the classification of power equipment depends not only on the appearance, but also on its performance, that is, the main performance parameters are measured by pre-test or the degree of equipment insulation meeting the standards, regulations and specifications.

3. Pre test provides scientific basis for the renovation of power equipment

The development of things always has a process from quantitative change to qualitative change, and the deterioration of equipment performance is no exception. Through the test of relevant parameters of equipment, through year-on-year accumulation, comparison and statistical analysis, we can find out the law of equipment performance change, predict its life, and combine with the operation situation, give full play to the equipment function, strive for active maintenance, and greatly reduce losses and improve Benefits. It is of great economic significance to predict the insulation life of important equipment such as generator, transformer and so on. The premise of "over life" equipment is to estimate its residual life reliably. The pre-test directly provides the basis for the maintenance and replacement of power equipment. Due to the gradual aging of power equipment, it is necessary to carry out partial maintenance or full renewal. Especially for the old equipment which is out of service, the pre test results can provide manual information for the decision of equipment renewal and transformation.

2、 DC leakage current and DC withstand voltage test

DC leakage current test is to measure the DC leakage current value of the tested object under different DC voltage. The DC withstand voltage test is a kind of electrical strength test for a certain period of time when the test object is higher than several times the working voltage. The principle of DC leakage current and DC withstand voltage test is exactly the same as that of insulation resistance test. However, the advantage of DC leakage current and DC withstand voltage test is that the test voltage is high and can be adjusted at will, which can more effectively detect the situation of insulation damp and local defects. During the test, the insulation status can be known at any time according to the indication of micro ampere meter.

3、 Measuring the tangent of dielectric loss angle

Dielectric loss angle test is one of the effective methods to evaluate the insulation condition of high voltage electrical equipment. Through the dielectric loss angle test, it can be found that the insulation is damp, the insulation contains gas, and the impregnation and oil are uneven or dirty. It is suitable for the test object with large volume and composed of a variety of insulation materials. It can detect the serious local defects and the overall defects such as damp and insulation aging sensitively and effectively.

4、 AC withstand voltage test

Although the test voltage of DC withstand voltage test is also high, it is not enough for safe operation of * * equipment. Therefore, in order to further expose the equipment defects, check the insulation level of the equipment and determine whether the equipment can be put into operation, AC voltage withstand test should be carried out. AC withstand voltage test can better simulate the actual operation of the test object under overvoltage, and compared with DC withstand voltage, it can often find some local defects of the test object more effectively. Since the test voltage of AC withstand voltage test is generally much higher than the operating voltage, it is a destructive test for the subject with poor insulation. Therefore, before this test, insulation resistance, DC leakage current and DC voltage withstand test should be measured to preliminarily check the insulation condition. If the insulation defects are found, the AC withstand voltage test shall be conducted after the research and treatment. AC withstand voltage test is a direct method to identify the insulation strength of electrical equipment. It is of decisive significance to judge whether the electrical equipment can be put into operation, and it is also an important means to avoid insulation accidents.

5、 Non destructive test

Non destructive test is to measure various characteristics of insulation under low voltage or other methods that will not damage the insulation, so as to judge the internal defects of insulation. The simple and common non-destructive test is to measure the insulation resistance of the tested object. When DC voltage acts on any medium, the current passing through it can include three parts: leakage current, capacitance current and absorption current. The latter two parts are time-dependent, which decrease with the increase of pressurization time and tend to zero after a certain period of time. At this time, the total current tends to a stable value, which is the leakage current. Generally, in the insulation prevention test, in order to facilitate calculation, it is not to measure the current directly, but to measure the change of insulation resistance with a megger. Since the DC voltage in the megger is constant, the insulation resistance is inversely proportional to the current. When there is a through concentration defect in the insulation of the tested object, the insulation resistance reflecting the leakage current decreases obviously, which can be found when checking with the megger. For example: the pin type support insulator commonly used in substation. The common defect is that the porcelain bottle cracks, and the insulation resistance drops obviously after cracking, which can be detected by megger. For equipment with large capacitance, such as motor, transformer, capacitor, etc., absorption phenomenon can be used to measure the change of insulation resistance with time to judge the insulation condition. The absorption test is sensitive to reflect the local defects and damp degree of class B insulation and class B impregnated insulation. For example, the phenomenon of insulation absorption of generator stator is very obvious. We usually use absorption ratio to express it as: k = R06 / R15, that is, the ratio of the reading of megger at 60s to that of megger at 15s. K value is the ratio of two insulation resistance values, which is helpful to reflect the insulation state. For example, for the dry generator stator coil with class B insulation, the absorption ratio is far greater than 1.3 at 10-30 ℃; if it is seriously damped, the resistance value of the insulation will decrease significantly, which will greatly reduce the K value, K ≈ 1; if K < 1.3, it can be judged that the insulation is damp. When the insulation has serious defects, K value can also be reflected. However, some concentrated defects have been developed so seriously that they are broken down in the withstand voltage test. However, the insulation resistance and absorption ratio measured before the withstand voltage test are very high. This is because although these defects are very serious, they have not penetrated through. Therefore, it is not reliable to judge the insulation condition only by measuring the insulation resistance. The principle of leakage current test is the same as that of insulation resistance measurement. The leakage current test is carried out at higher voltage (higher than 10kV). Due to the convenience of detecting leakage current value in the process of boosting voltage, it is easy to find centralized defects.

6、 Destructive test

Destructive test is also called AC withstand voltage test. AC withstand voltage test is to test the insulation withstand various overvoltage capacity of the tested object. Its voltage, waveform, frequency and the distribution of voltage inside the insulation of the tested object are in line with the actual operation situation, and can effectively find insulation defects. This kind of test is strict for insulation, especially can contain those dangerous concentrated defects, and it can * * insulation have a certain level or margin Degree. The disadvantage is that the insulation may be damaged during the withstand voltage test. In order to avoid the equipment damage, the withstand voltage test should be carried out after the non-destructive test, that is, it can be carried out after the non-destructive test is qualified. The breakdown voltage of insulation is related to the duration of pressurization, especially for organic insulation, and the breakdown voltage decreases with the increase of pressurization time. According to the relevant standard, the withstand voltage time is 1min. On the one hand, it is convenient to observe the condition of the tested object, so that the weak insulation can be exposed in time. On the other hand, the insulation will not be broken down for too long.

In the maintenance, repair and operation of electrical equipment, it is necessary to seriously implement the preventive test procedures of electrical equipment, continuously improve the quality, adhere to the prevention first, so that the equipment can operate in a long period, safely and reliably, and prevent the occurrence of accidents. In addition, we should adhere to the scientific attitude, comprehensively and historically analyze the test results, master the law and trend of the performance change of electrical equipment, so that the insulation performance of electrical equipment is always under monitoring, mastering and management. Only in this way can we truly realize the necessity of preventive test of electrical equipment, limit the expansion of electrical fault, reduce the damage of equipment, and improve the safety and stability of electrical system. Only in this way can we change from checking after the event to active prevention, from passive management to active management, from managing results to managing process, and realizing total quality management.

Through the above contents, I believe that you have a certain understanding of Sichuan Electric Power annual inspection and pre-test. If you have business needs, you can contact us, and we will serve you wholeheartedly!

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