Power Lines Phasing Ddentification

The nature of the question indicates the poster is not ready to carry out safely any test that would present that identification!

"For example, top to button? left to right?"

No, here's the ways it works,

If shorted out against your thumb;

A phase blows fingers off from long to short:

B phase blows fingers off from short to long:

C phase blows fingers from the outside, in.

Seriously, get professional help! Don't listen to strangers.

Re: "No, here's the ways it works,..."

True story. I once got a big contract to test and commission 62 overhead bridge cranes at a new aircraft mfg plant. All the cranes ran around in the ceilings and were powered by power rails and brush connections. When working on a crane, my partner and I had a clearly defined and careful procedure of locking out power on the sectionalized power rails before working on anything. But the union plant electricians were never around when we went through this, they would always show up an hour later than us (donut meetings every morning).

One day they arrived after we had moved a crane to a new section of rail and one of them asked me how we knew the phase rotation was correct on the rail sections as we moved from section to section. Before I could answer, my partner looked at me and winked then reached up and put his hand between two (dead) bars. He then immediately jerked it back like he had been shocked and said;

"See that? If you were paying attention, you saw that my hand twisted to the right, that means it was A-B. If it had twisted to the left, it would have been B-A. It's called the Right Hand Rule. Haven't you ever heard of that?"

The electricians were all dumbfounded, they stood there with their mouths gaping open for what seemed like an eternity. Then one said "I have heard of the Right Hand Rule, it did know that's what it meant!".

My partner was stoicly serious and said "Yep, that's where that comes from." I couldn't hold it in though, it was too funny and besides, I didn't want to let them leave thinking that was real. They never asked him another question that whole time.

As stated the answer is no. my question is why would you want to know?

For example, top to button? left to right? (where applicable)

Regarding your this Part of question, (may be what you are trying to know )it is often observed that and also often use that if you are standing in front of a Electric machine (Motor, Transformer) in a three phase system, you have

Left Arm = Red Phase

Head = Yellow

Right Arm = Blue Phase

Phase sequence is more important than phase identity for motors which will rotate whether you give red or yellow or blue to L1,L2 or L3. If reverse rotation should be avoided phase sequence relay should be used and phase sequence meter could be used to verify phase sequence before giving connections. Your question is regarding convention or standard practice.

Reading your question, I understand you want to find out when looking at a high power over head transmission pylon, with 6 (or more) steel core aluminium wrapped conductors hung between each pylon suspended by 3 foot of glass/ceramic insulator at least 20 meters off the ground, each pylon surrounded with warning sign of high voltage - danger of death etc, you want to know which phase is which? Yes?

Why?

The naming or color coding of the supply lines is done only for convenience of identification and has only a local significance, that too only for a particular piece of equipment or a group of equipments. In absolute terms A,B,C or for that matter R,Y,B are meaning less and do not indicate any special feature of the supply line. No body tries to name the transmission lines for the above reason.

When you energise two sections of busbars for paralleling and when feeding two transformers for paralleling phase identity is required

GA Pnaban.

I couldn't think of a practical example where the phase ID might be as important as rotation.

Parallel trafos from same (or synchronised) source is definitely a prime contender.

I work with genset synchronisation where rotation (really) matters but ID is only relative to the synchronised state's arbitrary datum....

I'm not sure if the OP is asking about ID conventions or if they really have to know which phase is which in order to do something on an undisclosed something else.

Wal,

I have a 1.5MVA, 12.47kV/480Y-277V transformer.

An electrical subcontractor needs to install a cutout at the power pole and connect

MV cables from cutout to primary side of transformer.

I need to verify before energization:

Phase A connected to H1.

Phase B connected to H2.

Phase C connected to H3.

Have you contacted the supply company? It would seem a sensible place to start.

We(europeans/Indians) normally write (in paper) from left to right and top to bottom except arabs(I don't know how chinese, koreans,japanese or any other race write) who write from right to left. Therefore naturally phase sequence should be in the same way,left to right/top to bottom.

That's potentially a very dangerous assumption! What if it's wrong?

So.....

Phase B connected to H1.

Phase C connected to H2.

Phase A connected to H3.

OR

Phase C connected to H1.

Phase A connected to H2.

Phase B connected to H3.

....is not acceptable? Do you need more than just correct rotation?

It might matter for the purposes of consistency in the network mapping. In order to do this you need to define (or discover) a reference.

It would seem that you are not the first person to have to make a call on this. Tools have been developed that help folk to do this.

Are you sure there is no phase identification on the MV side? Follow the line to the next few poles and look for tabs or coloured heat shrink sleeving or paint or...or...have a beer with somebody from the utility company.

Thanks for the information.

In addition to correct rotation, the phases need to match the distribution switchboard

buses and need to be color coded. I have a low voltage rotation meter, but I would

like to get it right the first time and before energization. The tool you have referenced

will do the job, but it wont be used that often, and I cannot afford it.

I will try the utility and see if there is a consistency in the power lines.

Thank you all for your time.

<...cannot afford it...>

What's the cost of not doing it?

Frankly speaking I still do not see why you need to identify the phases on the MV side.You can connect the primary lines any way you want, which generally depends upon the manner in which the lines come upto your supply point. If you have a common MV bus, still you do not need this exercise. Even the supply company may not be able to tell you which is A,B,C etc.because these identifications are meaning less since there is nothing called as line A or line B or line C. I would request you to make it more clear why you need this, so that somebody can gude you.

Then get the subcontractor to verify which one is which.

Some utilities have a rule of thumb they use for identifying which phase is which in distribution systems (34 kV and below). This can be useful to help balance single phase loads along a feeder, and also when rebuilding a circuit after extensive damage (earthquake, tornado, etc.). Transmission lines are usually rotated every mile or so to minimize capacitance effects, so any type of thumb-rule would be ineffective and dangerous. The ONLY way to verify phasing is to go back to a known phase identification (such as the source substation) and walk out the circuit, visually verifying the phase identification along the entire route. I would strongly recommend contacting the engineering group at the utility to identify the phasing at the nearest substation then walking the entire route yourself.

If the secondary of the new transformer will parallel to an existing bus, another method is possible. Install the new transformer and make up all connections, but leave the transformer secondary breaker open and locked out. The load side of the breaker should be energized from the existing bus. Energize the new transformer and check for voltage across each breaker pole, and between poles on opposite sides of the breaker. Matching phases will have very little voltage difference, while unmatched phases will have nominal phase-to-phase voltage. Once you have identified common phases, check that the phase rotation is the same on both sides of the breaker. To avoid damage, both the phase matching across each breaker pole and the phase rotation on each side of the breaker must agree. If they do not, reconnect the high voltage leads to correct the problem, then retest.

For those who question why phase identification is necessary, consider that for locations with multiple incomers the separate feeds are usually paralleled at some point upstream (generating station, HV substation, or other other source). Matching rotation in NOT sufficient unless the local point of connection is the only interconnection at any voltage. If you connect phase A of one transformer secondary to phase B of another when both are ultimately fed from the same transmission grid, you will get a very bright flash and very loud bang, often followed by a frantic call to the local fire brigade.

Phase rotation or "transposition" of the 3 conductors is normally done in HV long transmission lines. I have seen red/yellow/blue discs mounted on towers to identify phases. They should do it in substation equipment,on transformer bushings,LV lines,cable end boxes,motor terminals,heat shrinks,use of coloured insulation tapes even inside switchboards,motor starter etc. Once, in an airport, where there are about 5 or 6 electrical engineers work,while splicing cables for 2 nos 11kV/LV transformers the cable jointer wrongly identified two cables for one of the transformers. As a result after energising they could not parallel the two transformers because the voltage difference between identical phases in the LV side, which should actually be zero. They said the vector groups of the 2 transformers were not matching. After about 2years they brought an engineer from the utility and checked and found the vector groups were matching but splicing(identifying phases) was wrong.