Oops. should have said "automatically"
Generator earthing
- Thread starter RF Lighting
- Start date
Oops. should have said "automatically"
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Even if only used as standby, there are benefits to being able to do this - one of them being the ability to fully load the genny for periodic runs using your own load (and perhaps even exporting some) to load it properly. Otherwise, all you're going to do it run it on light load for a while and then shut it down all oiled up.
On that, I recall a tale which still has me in stitches at the image it creates.
At my last place, we had our own 500kVA transformer on the end of a long series of overhead lines. We had a planned outage for tree cutting, and one of hte utility guys came to our site to make sure we couldn't backfeed the line. I got talking to him, and he showed me the local network maps - and just what a tortuous route our supply made.
But he told me how they were doing some works in a town not far away which required them to bring in generators to keep the town on. His manager appeared, covered head to foot in black splodges ! They'd had these containerised gennies running for some time with no load - which meant the engines got cold and the upper cylinders got quite oily. Then they hit the switch, the gennies picked up the load, opened the taps, and the manager was walking past just as all this oil and sh*t came out the exhaust
Knowing what my tired old Land Rover used to be like, I can just imagine what it would be like for something that size.To your 3 I'll add - being able to sell your standby capacity to the grid as STOR (short term operating reserve).
While trying to find out what "G59" is in relation to hooking up small power sources (one of our customers at work mentioned it), I came across this outfit http://www.flexitricity.com
Quick summary - if you have a standby generator, and the right switching arrangement (must be capable of parallel operations) you can sign up with them, they'll aggregate capacity, and then sell it to the grid for STOR. In times of trouble (big generator tripped out, spike in demand) they can call up your genny (along with many others) to add distributed supply to the grid until something more conventional can be brought online or the demand reduced. You get paid a retainer for having your genny available, and extra (I assume a per-unit charge) for when it's used.
In their blurb they make a big thing of exercising your genny under load, and turning over your fuel stock, to improve reliability - which all sounds quite reasonable.
There's a similar scheme if you have a large load that can be turned off on demand as a means of reducing load.
You can buy small control modules that do it all automatically - I recall reading up on one range ... ooh ... must be getting on for 20 years ago now (so not new !). Little box of tricks (or collection of boxes) that will take care of starting your engine, running it up, adjusting the throttle, and closing the main breaker at the right moment. After that, they'll manage the throttle(s)* to share the load according to your settings.We used to do something like that years ago with 3 lamps at college
Far cry from watching the lights and (I assume, never done it**) getting a big flash and bang if you time it wrongly.
* Some will manage multiple gennies with load sharing etc.
** There was a demonstration/test rig in the labs at uni, but we didn't do that part in our course. I did note that they had a solenoid plunger behind the mechanism which I assume locked it unless the red light was out.
I recall doing at least two labs on machines, one with an Amplidyne (or was it the Metadyne, they had both), the other was exploring the torque-phase angle relation in a synchronous genny - and seeing what happens if you over-drive it and break it out of lock, made interesting patterns on the chart recorder (which was the recording technology of the day).
I can imagine a few youngsters having to hit ${favourite_search_engine} to find out what Amplidynes and Metadynes were.
Or hands off if you screw up badly enough.
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Nope, but I did see similar involving a 1650kVA unit after we blew one of it's cylinder heads off!
We had similar at a site I used to do some maintenance work at. The was a DNO power cut, so the ATS did it's stuff and brought two 400KVA diesel generators on line and dumped the load onto them.
There was an office over the road who when the power went off, looked out of their window, saw all the black smoke, and called the fire brigade, who promptly attended site!
As for my generator that started this thread, I have been back this week doing some of the prep work, and we've installed a 4 pole centre off changeover switch, so there is no way any of our live conductors can come into contact with the DNO's, and I've installed an earth rod. We ended up driving in 2.4 meters of rod to get down to a reading just over 15Ω which when connected up with some old under ground lead water pipes gives us a reading just over 3Ω, so I'm happy with that.
We have connected our earthing to the MET along with the DNO's TN-S supply and the installation earthing.
Just waiting on the generator now to actually test the system.
There was an office over the road who when the power went off, looked out of their window, saw all the black smoke, and called the fire brigade, who promptly attended site!
As for my generator that started this thread, I have been back this week doing some of the prep work, and we've installed a 4 pole centre off changeover switch, so there is no way any of our live conductors can come into contact with the DNO's, and I've installed an earth rod. We ended up driving in 2.4 meters of rod to get down to a reading just over 15Ω which when connected up with some old under ground lead water pipes gives us a reading just over 3Ω, so I'm happy with that.
We have connected our earthing to the MET along with the DNO's TN-S supply and the installation earthing.
Just waiting on the generator now to actually test the system.
Just a loop tester at the moment, but I will be hiring a proper electrode tester when my wholesaler decides to pull their finger out!
You just need the DNO approval now !
All this though does answer another question that is occasionally asked, "Can I install separate earth rods & connect them to the DNO earthing?"
If it is acceptable in this case I would suggest it is generally acceptable (at least to the DNOs)
!All this though does answer another question that is occasionally asked, "Can I install separate earth rods & connect them to the DNO earthing?"
If it is acceptable in this case I would suggest it is generally acceptable (at least to the DNOs)
Are there likely to be any issues from the DNO? Have you had to deal with a similar situation your self?
I guess I must be missing something here. Apart from maybe 'sounding better' to have used a 'proper electrode tester', what is to be gained? In other words, under what circumstances could a measurement obtained by loop testing be significantly 'wrong'?
Kind Regards, John
Can't see any, if any questions refer them to the stuff I quoted earlier
Where the electrode resistance areas can clash, loop testing is only for use where you are testing an electrode on a TT system which has RCD protection.
An electrode used as the means of earthing of a system needs to be done the old fashioned way.
The method is completely alien to a majority of sparks bar the likes of Westies men and lightning conductor men who will probably do this a lot. I would have to consult my books on this type of testing as I have never needed to do it before.
I'm hoping the tester comes with instructions. We did cover electrode testing at college, but that was a lot of years ago now!
Should do, or they might be available on-line. The modern digital types are remarkably easy to use.
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