What should insulation resistance be

Degradation of the insulation between two or more charged potions as shown in Figure 2 poses the risk of a short-circuit. Higher insulation resistance values indicate more effective insulation.

II Conductor to Earth Insulation. Rotate the handle of megger or press push button of megger. The reading of meter will show the insulation resistance of the conductors. Location: From. Length: …………………….. Name of the manufacturer:. Core No. Date of Test ……… Temperature……. NOTE : These measurements shall be recorded in two copies.

One copy each shall be kept in SE Sig. But testing programme shall be followed as per policy guidelines issued by Railway Board as under: ref. Spare conductors will be tested every year. During Meggering: Make sure when testing for earth, that the far end of the conductor is not touching, otherwise the test will show faulty insulation when such is not actually the case. Make sure that the earth used when testing for earth and open circuits is a good one otherwise the test will give wrong information Spare conductors should not be meggered when other working conductors of the same cable are connected to the respective circuits.

After completion of cable Meggering: Ensure that all conductors have been reconnected properly. In case of signals, aspect should be verified personally. In case of points, verify positions at site.

Buka menu navigasi. Tutup saran Cari Cari. Pengaturan Pengguna. Lewati carousel. Karusel Sebelumnya. Karusel Berikutnya. Actually our "modern" regs some years ago also specified just a 0. That sounds like the old Electricity Supply Regulations - they permitted a maximum leakage of one ten thousandth part of the installation's max demand. Earlier regs did have various different ways of calculating the IR limit - often based on the number of points.

Indeed, as my very old black and white illustrated book "Electricity" by The Bennett College states, the requirements of the I. AJJewsbury : original requirement was based on a fraction of the total load the installation was to be loaded with.

Harry Macdonald. However, if you do get 1Mohm on a new, clean, dry bit of wiring it is probably a good idea to investigate why before saying "OK, it passes". But is it is on a circuit with several old motors and contactors then no need to investigate further. A local church asked me to do their PAT, they had never had it done before and I condemned several items including the bell ringers electric heater because I could see the copper conductors through the gaps in the cable insulation and also I also put an advisory note on the churchyard Christmas tree lights because they had an insulation value of around 1 Mohm despite having been on top of a cupboard in the vestry for several months.

They have not asked me to do the PAT again. Andy Betteridge. Andy Betteridge Obviously you did not convert them to see the light of truth. So they remain in the ignorance of darkness. You could have a pair of uninsulated 25 mm meter tails which are absolutely lethal, but they could easily pass an insulation test. Indeed - and if it came to a choice, I'd rather forego the insulation test in favour of a thorough inspection.

Eyes, ears fingertips and nose can be very good at detecting things meters can miss. I think a few years ago there was a discussion about which test was the most important, in a sort of Desert Island Discs way ' if you could only take one meter with you?

We decide that an R2 test was the most useful, as any other fault would become obvious in a safe way on switch on. Zoomup : Wombat : What is the science behind the 1 MOhm minimum insulation resistance? Thank you for this comment. Where you mentioned "It was set to limit current leakage to safe levels.. Difficulty in breathing. Reversible disturbances of heart function. Generally, to minimise the risk of damaging RCDs it may be appropriate to test circuits in groups but where necessary circuits may need to be tested individually.

It should be recognised that, due to the parallel relationship, the total insulation resistance of a group of circuits or a whole consumer unit will be less than the lowest individual circuit value. Consequently, where circuits are tested collectively and a low reading is obtained, individual circuit testing should be undertaken to identify whether it is an individual circuit that is responsible for the low reading. It should be noted that where an existing consumer unit is intended to be replaced the condition of the existing cables should be determined before proceeding with the replacement.

Otherwise, insulation defects that previously were undetected may cause the operation of RCDs.