From time to time isolation of cables and wires needs to be checked as the quality of protective cover over the years worsens because of periodic heating, influence of the atmospheric phenomena, the wrong distributing and soldering, etc. If not to find problem in time, it is possible to appear unexpectedly before the fact of failure of all system.
It is required to you
- - megohm meter;
- - electrician with group of safety III or IV.
Instruction
1. To check isolation of wires, find experienced specialists electricians with group on electrical safety not lower than III or IV. When carrying out all works be guided by the Regulations for Electrical Installation (REI) and the User Rules for Operating Electrical Equipment (UROEE).
2. Pick up the suitable device. For measurement of insulation resistance of cable with a section less than 16 quarter of mm take the megohm meter on 1000 V, for thicker or armored cable – on 2500 V. Isolation of any wire can be measured by the megohm meter on 1000 V.
3. To check isolation of electrical wiring with insulation resistance less than 1 megohm, test them alternating current of 1 kV of mains frequency. In order that measuring results had official character, devices have to undergo annual checking in bodies of Gosstandart of the Russian Federation.
4. Pay attention, measurements have to is carried out at isolation temperature above +5C and at low degree of moisture content. To learn moisture content degree, calculate absorption factor, having separated the measured insulation resistance in minute after application of tension of the device into insulation resistance in 15 seconds. This coefficient should not differ from factory data more, than for 20%.
5. Connect the megohm meter to wire by means of flexible wires with restrictive rings in front of probes of contact and handles on the ends for isolation. The less there will be connecting wires, the more precisely there will be measurements, resistance of their isolation should not be less than 10 megohms.
6. Before measurements check the tested object, on it there has to be no tension. If there is need, carry out grounding (after connection of the device).
7. In the place of connection of the device clean isolation from dirt and dust. Connect wire to slots of the megohm meter. Choose the voltage output which will correspond to the tested wire or cable.
8. If you measure insulation resistance by means of the device of generating type, rotate the generator handle with speed of 120-140 revolutions per minute. To start work of digital meter it is enough to press the button.
9. Take of instrument reading and write down. If it is several measurements, after everyone remove capacity charge, grounding those parts of object on which tension moved.