Measurement of insulation resistance of electrical installations

Electrical insulation is the most important means for ensuring the safety of work with electrical installations and their uninterrupted functioning. The effect of an alternating current not exceeding 0.5 mA is practically insensible to the human body. According to current regulations, alternating current with a frequency of fifty hertz, flowing through the human body, should not exceed the value of 03 mA. Therefore, a systematic measurement of the insulation resistance is a necessary measure designed to ensure electrical safety when working with high-voltage equipment.

The most important characteristic of an insulation coating in this aspect is the index of its electrical resistance. In electrical installations of high voltage , several different types of insulation are used. The working coating is designed to ensure the normal operation of the unit. It is chosen taking into account the technical features of each electrical installation. Therefore, regular measurement of insulation resistance of this type is necessary to control the integrity of the coating, which ensures the normal operation of the equipment.

Additional insulation, performing a purely protective function, is designed to exclude even the slightest likelihood of electric shock in the event of any damage to the main coating. Measurement of insulation resistance of this type is of key importance in terms of safe operation of electrical installations.

In addition, in some types of electrical equipment, double insulation is used, which is a combination of the two above-mentioned types of coating. The peculiarity of this combination is that the parts of the unit accessible for touch will not get dangerous voltage even if one of the insulation layers (working or supplementary) is damaged. Measurement of insulation resistance of this type is reduced to monitoring the overall integrity of the shell and each of its components separately.

The need for regular monitoring and measuring activities is caused by factors that worsen the condition of the insulation coating and contribute to its degradation. To such harmful factors, first of all, electrical and mechanical damages are listed; The effect of aggressive chemical compounds, which is not uncommon in industrial production; Thermal damage.

The device for measuring insulation resistance is called a mega-meter. This device is intended not only for measuring the resistance of insulating material, but also for testing its electrical strength (in other words, a test for the absence of electrical breakdowns). Before conducting tests, the electrical equipment must be de-energized. The very method of measuring insulation resistance of electrical installations consists in the formation in the depths of the device by means of a special built-in electromechanical generator of direct current a certain control voltage that is applied to the object under test. In this case, the measuring voltage must exceed the analogous index of the electrical network.