IR value of bus bar

The infrared value of a bus bar will closely approximate the black body radiation curve for any object. Your mega ohm leakage path resistance readings have nothing to do with the current times resistance (IR) voltage drop that an infrared measurement of how much self heating of the bus bar would safely reveal.

Now if you mean anything other than my proposed interpretations of your acronyms, I propose that you politely correct me and/or start again with complete English verbiage.

IR value means Insulation Resistance value.

i asked about the insulation resistance value of sf6 bus bar (the bus bar placed inside the sf6 chamber)

What is sf6? Sulphur hexafluoride? Did you really mean 100T ohm = 100 x 10¹² ohm between phases? Not being an electrical engineer I don't know whether that's reasonable, but it seems very high, and there's a big discrepancy with the phase-to-earth figure. Perhaps somebody can comment.

Codey

As you can see from both of the previous posts, it is important to DEFINE ALL ACRONYMS the first time they are used in any communication.

If you have 20-40MΩ between Phase and earth, then you would expect to have no more than 40-80MΩ between any two phases. Therefore your value of 100TΩ between phases is HIGHLY questionable! Of course it is conceivable that the 20-40MΩ is in error, but I doubt it.

If you measure 40 M-ohm for one phase to earth and 20 m-ohm to earth in another Phase, you are likly to get a megger value of 60 M-ohm for the measurement between phases.

please check the correctness of the scale selected.

It all depends what you are measuring . . and what you are measuring with . . .

It would be most worthwhile to describe you isolated phase bus . . voltage . . . current . . . complexity . . .

Similarly, . . . it would be worthwhile to describe your "megger" and your connections. Is it a 3-terminal "insulation tester" . .?? Do you have the GUARD TERMINAL connected to ground?? . . . If so, then you should be reading close to INFINITY between phases . . . and 100T ohms is close to infinity . . .

Oleh

hi please note that phase to earth value should be in milli ohm or micro ohm and phase to phase value should be infinite. in fact what your phase to phase value is almost correct but phase to earth values are totally wrong. please check the value once again and kindly note that the value should be in milli ohm or micro ohm

Oh, no. Phase to earth should be milliohms only if there is still a neutral to ground connection present somewhere. This might be a completely isolated Δ power feed or other circuit. It is critical to know what the circuit you anticipate to have when doing a megger test. So far we only know that this is not an Infrared thermal measurement concern. We do not know at all anything about the expected circuit. We still don't know why sulphur hexafluoride is being used in the cabinet.

For your information the purpose of doing the megger test is to finding the insulation resistance value.

If the resistance value between the phase is high than only it is possible to avoid the short circuit.

simileraly if the value between the phase and earth is low than only it is possible to avoid damage during short circuit condition.

Please note that the purpose of providing the sf6 gas is for providing the isolation between circuit/instument.

Trust me when I say that I know very well what a megger test does and depending on the manufacturer how it works. I do appreciate though you pointing out the purpose of the test. You see it's the test itself that has yet to be well defined here. The gas sulfur hexafluoride is the only insulating material that has been mentioned here. It does a very good job of keeping moisture away from conductors by displacing the atmosphere in an enclosed chassis. However, being a gas it will not mechanically support any solid metal. (Well one can make a hand size aluminum foil boat to float on this gas but it certainly won't stay in a fixed location.) So there has to be something else providing mechanical support of the busbars while maintaining the electrical isolation.

Also at the very high resistances that one needs for safe power distribution the effect of unintended interference signals producing a false but still high resistance reading is very common. So while Ohm's and Kirchoff's laws do still apply, it can get complicated quickly in the >10E8 ohm range.

So the only one who can accurately answer the OP's question is somebody on site with experience and the trained eyes to see exactly how the circuit and test is configured.

please note that IR value should be in G-ohm or T-ohm for both phase to phase and phase to earth measurement.

Sigh, for what circuit? If the phase has a grounded neutral (department of redundancy department standard B14741B) connected to an unenergized transformer then both the hot and neutral of the phase should read a short to ground. It all depends on the circuit in place.

pprrrrr.......

Hi, i think your values are OK, and the system would run fine... for instant the thumb (or the lay man rule, as u say) is 1 Mohm for 1 KV system.....