Electricity is an invariable companion of a modern person; one has to constantly deal with it both in everyday life and at work. So that electricity continues to be an assistant and does not turn out to be an enemy of man, does not threaten his property with fire, there is a set of electrical safety measures. Its main element is considered to be the quality of insulation of conductive conductors, equally concerning:
- insulating sheaths of conductive cores in power cables;
- insulation of control conductors in control cables;
- dielectric protection of wiring of internal power grids (insulation of electrical wiring).
Of no small importance is the quality of the insulation of electrical equipment, which ensures the protection of its conductive bodies from the ingress of dangerous phase voltages on them and the possible damaging effect of electric current.
Unfortunately, there are many factors contributing to the loss of insulating properties:
- the harmful effects of the external environment (high humidity, temperature drops, the presence of aggressive components, radiation, including solar radiation);
-regular excess of the load capacity of the conductors, causing them to warm up;
- long-term operation with inevitable aging of insulation;
- the appearance of mechanical damage during operation or repair, latent manufacturing defects (factory defect).
Deterioration of the insulating properties is accompanied by lowered insulation resistances, therefore routine operational tests of electrical equipment always accompany measurements of insulation resistance.
Technique and frequency of measurements of insulation resistance
Requirements for the values of insulation resistance are set out in a number of regulatory documents, in particular, they are regulated by Table 38 of Appendix 3.1 PTEEP. Its minimum value should not be omitted, for example:
- below 0.5 MΩ for lighting networks;
- less than 1 megohm for stationary electric cookers.
When measuring insulation resistance in single-phase networks, measurements are taken between the following pairs of conductors:
- zero and phase wires;
-phase and protective grounding PE;
- zero and earthen.
Thus, three measurements are made, while in three-phase voltage circuits, the insulation resistance will have to be measured 10 times.
For the safety of electrical equipment and in order to ensure the safety of personnel, the insulation resistance is measured by completely disconnecting the electrical wiring from the power circuits of the equipment and disconnecting all loads. If a line with a low insulation resistance is detected, the defective area is localized by sequential disconnection of the line sections in the direction opposite to the source. All measurements end with the registration of measurement protocols.
Insulation resistances are measured with a megohmmeter, a special device for measuring high resistance values.
The frequency of carrying out control measurements of insulation for resistance depends on the purpose of electrical networks, their significance and operating conditions. So for especially dangerous rooms with high air humidity, temperature, and the presence of earthed floors, it is necessary to measure insulation at least once a year. Children's and medical institutions, elevators and a number of other important facilities are equated with similar conditions.
At less hazardous facilities (institutions, apartment buildings), measurements are taken less often - once every three years.
Given the strict requirements, complexity and high responsibility of conducting insulation measurements, this type of service should be trusted exclusively by certified companies. Customers from Moscow and the Moscow Region should pay attention to CenterEnergoEkspertizy LLC, a licensed, state-of-the-art electrical laboratory and highly qualified personnel guarantee the safety of your networks. Services can be ordered on the company's website https://cenerg.ru/
