But if you allow 5% voltage drop in that part of the installation, you have already gone 2% beyond the total 3% voltage drop you are allowed for the house lighting circuits. Voltage drop is measured from the origin. Regards Bruce
By the end of this process, you?ll have one mighty strong ferret.
Is that a guess or a fact?
It has zero impact on the thousands of miles of double and quad conductor circuits on the HV grid system
He read it in the ladybird book of electrics.
They are protected by constantly monitoring the load, temp, etc. of each cable. Actually each cable span between pylons, if you look you will see a sensor next to each insulator. It measures the angle of the cable, from which you can deduce the operating conditions to see if its safe.
How to do that was a question that came up in my interview for the cegb while I was doing my final year at uni.
so far so good
Fail
Not at all (although for underground cables there are CT's on each 'core')
Now that is really funny.
Ever heard or arcing horns or stockbridge dampers? Evidently not.
Ever considered that the number of pylons with any sensors or with any accesible communication infrastructure is a tiny fraction of the total?
Hilarious
Thank f*ck you never made the grade otherwise the lights would have gone out years ago.
It's dennise, what else do you expect
"His eyes are open, the mouth moves, but Mr. Brain has long since departed"
So more than each cable then.
yes.
No.
Evidently wrong.
So you are denying that it works then, you had better tell NG.
Maybe.
In article , dennis@home scribeth thus
But did you get the job;?..
No, just a VT and a CT on each phase at both ends for all two and four conductor overhead lines everywhere on the 400kV and 275kV network.
The conductors are commoned as they come off the terminal tower before they even meet any measuring or monitoring device.
The VT's and CT's, being bits of inert materials, have no knowledge of the conductor construction. Restring an overhead line from four to two conductor and the VT's and CT's don't need to change.
Then, by your own admission, you know sweet FAl about pylons and the conductors strung from those insulators and the dangly bits situated next to those insulators.
You've failed again.
There is no need to deny anything. They aren't fitted.
Out of curiosity only, is it permissible to add a tapchanger transformer at the house to resolve excess Vdrop? I'm not suggesting it as practical, just wondering what the 17th's position on it is.
NT
Is the OP using underground ducting for the cable or direct burial?
- Direct burial is cheapest, you need the trench clear of stones, marking tape & depth suitable for the intended use of the ground.
- Cheap corrugated ducting soon adds up at 350m, makes replacement AND theft of the cable easier, and may have considerable friction for pulling if not a straight relatively level route. Manufacturers specify limits on pull tension.
- Twinwall corrugated ducting is more expensive, has a perfectly smooth bore, making pulling of cables somewhat easier.
TLC sell a lubricant which eases cable pulling. Farmer offering to direct plough the cable with an attachment?
You can get lockable outdoor cabinets, more commonly used at sides of roads, they can be heavy gauge steel or thickwall plastic. Whack on a concrete base with suitable ducting, they use ground anchors to fix. If the price is outrageous you might be able to weld one up (4mm steel unless v-grooved needs a decent welder).
Apart from BS7671 requirements on voltage drop post meter, and DNO ability to adjust tappings, if the meter is at the pole then you are going to pay for power dissipation in a very long cable. That loss is over only about 10-12 units a day at baseline load, but if you use E7 heating or E7 heatpumps the current draw and thus power lost becomes more onerous. Cost out carefully.
Providing the conductors are all the same size and length (and hence same resistance), and have good connections, and are long enough that the conductor resistance is large relative to the connection resistance, they will take equal currents.
The earlier versions of the 16th Ed wiring regs had a section on conductors in parallel. (30/32A ring circuits are specifically excluded, due to derating.)
That goes some way (but you have to use an interlocked breaker). When you have more than two in parallel, you also have to allow for backfeeding a fault from the far end. (So if I have 4 runs in parallel protected at 100A each, and I short one of them to ground, I can get 100A from the supply plus 300A backfed from the far end down a single 100A cable, without tripping the circuit protection.) For long runs, you also have to be careful of meeting disconnect times when some of the runs are broken.
?
I spoke to the electrician. He has allowed 5% voltage drop from the meter to the house. He claims this is a supply cable and does not factor into final circuit v-d calculations.
He is also exporting the earth from the meter in 35mm green/yellow wire. There will be a new transformer on a pole, so I'm guessing that the supply company will put an earth spike or something in there.
So, given that the system will be earthed 350m away, is it possible that the neutral and the earth in the house will be at a different potential to the surrounding ground?
LGF
In article , Andrew Gabriel scribeth thus
No need to "?" it, in Dennis's world there are his very own set of laws Ohm's is outa the window;!..
Your electrician is wrong if that is what he said and the cable is part of the consumer installation. If the cable is before the meter it is a supply cable under DNO control and does not count in the voltage drop calculations in a consumer's installation. If it is after the meter then it does feature in the voltage drop calculations.
The reason is that that the DNO will make sure the voltage is within spec at the supply terminals/meter, wherever that is. So if it is at the low end of the acceptable range 350m from the house, then by the time it reaches the house it could be under.
Relevant regulation is 525.101: "The above requirements are deemed satisfied if the voltage drop between the origin of the installation (usually the supply terminals) and a socket outlet or the terminals of current-using equipment does not exceed that stated in Appendix 4 section 6.4." (The latter states the 3% and 5% requirements)
There is a get out for your electrician under 525.1 if he knows (for example by measurement) the voltage will "be greater than the lower limit corresponding to the product standard relevant to the equipement." In that case he could allow more than the 3% and 5% drops. But if in future it was ever lower than you wanted then the DNO would have no interest in raising it for you provided it was within range at the supply terminals.
On your latter point, yes it is possible the earth voltage will be different over that distance. If it was a DNO PME supply then they would probably bury an additional earth rod in the trench where the mains cable joined the service cable just before it entered your house or meter box. You are not allowed to have any connection betwen neutral and earth within the installation as a consumer, but you could add a connection to a local earth rod from say the consumer unit in the house.
My advice remains have the dno supply terminals in the house or as close to the house as possible.
Regards Bruce
Its ohm's law that makes it that way. Unless you have exactly the same resistance down the two cables you don't get equal currents. If you don't have equal currents you can't run the wires at their maximum so the current capacity of parallel conductors is less than the nominal area would allow.
Of course you could just add some known resistance in to balance them. 8-)
Best not mention impedance then.
You are Forrest Gump AIKMFP
Your skull has high resistance. Nothing enters your brain.
Let me make it abundantly clear that this is not my new fancy house or my electrician. I'm simply a concerned friend. There is absolutely no way I would consider this just to "save" =A310k. I mean, each of their solid basalt baths is going to cost that much! This house is in a prominent beauty spot, mostly underground, and will be finished to a very high standard. Skimping on the electricity supply is madness, but then I suppose it would mean the kitchen won't have all those fancy gadgets...
I completely agree with your advice, which is basically what I've been trying to tell them. The NICEIC "Approved Contractor" is seeing pound signs I think, and is out of his depth.
LGF
acknowledged. my poor wording.
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