Which earthing system?

[Engineer54]

Think you had better tell the mining industry and every hospital/medical centre in the UK, (and a few other area's i can think of) that they are using ''Illegal Supply'' systems!! lol!! IT systems are used where security of supply is recognised as a critical criteria, and are to be maintained, even in the event of a fault!!!

Now i don't happen to know how critical the security of the power supply is for an unmanned natural gas pumping station. I also don't partially know what sort of safety shut down features these pumping stations incorporate. But an Isolating Transformer is usually a prerequisite for an IT earthing system, where the supply is being brought in with it's own TN earthing arrangement!!

I simply have no experience with such sudo petro-chem gas pumping stations, so i'm not going to make any wild guess statements.

 

[Outspoken]

Think you had better tell the mining industry and every hospital/medical centre in the UK, (and a few other area's i can think of) that they are using ''Illegal Supply'' systems!! lol!! IT systems are used where security of supply is recognised as a critical criteria, and are to be maintained, even in the event of a fault!!!

Now i don't happen to know how critical the security of the power supply is for an unmanned natural gas pumping station. I also don't partially know what sort of safety shut down features these pumping stations incorporate. But an Isolating Transformer is usually a prerequisite for an IT earthing system, where the supply is being brought in with it's own TN earthing arrangement!!

I simply have no experience with such sudo petro-chem gas pumping stations, so i'm not going to make any wild guess statements.

I think you need to stop digging a hole here ET, I already mentioned I have worked in the NHS, and whilst some individual items of equipment may be connected up as an IT system via an Isolating Tx (Such as Medical Scanners - Nuclear Medicine) the overwhelming systems in a Hospital are either TN-S or TN-C-S depending on the age of the building and the services. I have worked in mining situations and my Brother-In-Law was a mining Engineer for 39 years and I can assure you that they are NOT IT systems and have not been for many decades (Just spoke to Steve on the phone to confirm as he now works as a Mining Consultant). Perhaps outside of the UK this is different. He explained that sub-surface electrical systems are fed via 1:1 Isolating Tx's, but they are most certainly not IT, the subsurface systems are TT and have been since at least the early 1970's..these days they are TT'ed with RCD's on everything.

What the hell are you going on about pumping stations for? No-one has mentioned a Transco Pumping station (Because in the UK it would be Transco) and i also happen to know that many of these are PME because they are connected to the local grid...but what relevance they have to this discussion I am unsure...Tate and Lyle make Sugar if that has confused you?

 

[Engineer54]

Digging a hole, ...lol!! Perhaps you should have taken more notice of the operating suites in the hospital you were working in, or you would have known that these areas all operate on an IT supplied monitored system!!
Now having been involved in the building of several Hospitals now (including my present project), ranging from small 150 bed, to 600 bed, and on what was the largest medical city project in the world at 1550 beds, i doubt very much, if you could tell me anything about hospitals there services and hospital supplies!!!


As for the mining situations, maybe your right about the UK, or maybe not, as according to our Mechanical Engineer here, who spent a good many years with the National Coal Board (or whatever they called it) on the coal mines in Wales, tends to think otherwise from many of his past stories/experiences that he's passed on to me...
But have no fear, i WILL definitely confirm or otherwise with him tomorrow!! Now just thinking logically about what you have posted, i would have thought, the very last thing they would want below ground, on what may be life support systems, is bloody RCD's tripping out!!

I'm only going by what the OP has stated in his post #17 eg, ....

Thanks for all replies so far, to clarify the site is a gas agi... (whatever a gas agi is)/ ... The isolating transformer supplies all of the essential equipment to do with the gas pumping as far as I am aware.

Sounds pretty much like a gas pumping station to me, ...What do you think?? lol!!

What Tate & Lyle and sugar has to do with any of this, i haven't a clue!! lol!!

 

[Engineer54]

Ok, i've had a bit of a chat on the phone with our Mechanical Engineer (Forgot he was off on a factory materials inspection to Changsha Saturday), and gather that the low voltage supplies for the coal mines he was involved with, had high impedance neutral earthing (aka a form of IT) in which the TX neutral point, is connected to earth through a resistor of a value sufficient to limit earth fault current to a few amperes, generally no more than 25 A and normally much less!! Reasons given, to limit earth fault currents and arc flash, which is/was the largest cause of electrical injuries in mines!! As with an un-earthed system, an earth fault to an energised phase will not operate an OCPD, so supplemental ground-fault detection is required to outgoing circuits and overall leakage/tripping monitoring at the supply source....

I'll be having a more in-depth chat with him when he returns to site, maybe tomorrow or Tuesday... I personally have no experience or knowledge of mine electrical systems, and very limited Quarry experience. But it sounds very much like NER IT earthing is used in mine situations, and for what sounds like, very good and sound reasons...