Price Of 3 Phase Electricity Transformer

[simon43]

For my small hotel project in Phuket, I need to install a 3 phase transformer to convert the 33,000 volt power line supply adjacent to the hotel down to 400/220 volts. The rating is 50KVA.

I've been quoted about 400,000 baht for this, with 350,000 of this being for the transformer.

Does this price seem about right? Sounds rather high to me, but I'm no expert!!

Thanks for any input.

Simon

[GuestHouse]

Simon,

I think you've been quoted way over the top.

If you can wait a few days I'll contact our electrical engineering group in Thailand and get a quotation for you. (The price we pay)

[RamdomChances]

Sounds way over to me, last time I looked into it for the farm it was going to be about 150,000 (I think) and that was with about 300m of cable as well. That was from the electricity company.

Edit, I just noticed you said 350,000 was for the tramsformer, might just depend on what size it is, we we're looking at the smallet

Edited July 28, 2006 by RamdomChances

[simon43]

Guesthouse - that would be much appreciated. AFAIK, the local electricity company has to do the installation work, but I can source the transformer myself.

Do you need any more details for the quote? My architect plans quote 'Transformer 50KVA by PEA 33KV/400V-230V 3 PHASE, 50Hz Oil type'

(I think PEA must be the name of a manufacturer?)

Also, please note that there is no 400v equipment at my hotel. Everything is 220v and we just need the 3 phases so as to 'balance' everything out.

But PM me if you need more details

Thanks again

Simon

[Crossy]

(I think PEA must be the name of a manufacturer?)

PEA is the Provincial Electricity Authority, the out of town version of MEA (Metropolitan EA).

[monty]

I just paid a little over 500,000 Baht for a 100KVA transformer.

I had 3 companies make price, and all were within a 5% margin, so I just went with the one who had the most recommendations...

The actual transformer is not all that expensive, but there are a lot of extra costs (compulsary) involved!

In my case the price included around 170 meter of high tension lines, including the poles, insulators, high voltage fuses etc, the transformer, the electricity meter including the deposit (bank guarantee) for the electricity company, around 40 meters of underground 3 phase cable (400V) and the main breakerbox (big one with volt and amp meters, main 150 amp breaker and four 50 amp breakers (all 3 phase) to feed the seperate parts of the building.

Seems like your quote is a bit too expensive if no high tension lines / poles are required, but not by a huge margin though (if all the extras like the meter, guarante, etc are included)

Another advantage you have with your own transformer is that you get a TOU meter.

Basically means you pay around 4.3 Baht/unit between I think 9 am and 10 pm on weekdays, and just a little over 1 Baht/unit at all the other times.

Bad news if you have factory producing during the daytime but pretty good in the hotel business where a very big part of electricity consumption is during the night (aircons in the rooms).

Weekends also tend to be busier, and everything at a little over 1 Baht/unit!

Edited July 29, 2006 by monty

[simon43]

OK - thanks for the info.

Also, can anyone advise me how important it is to try to 'balance' the 3 phases? I have 5 bungalows and 3 other buildings. Since I have no idea which rooms will be occupied and which appliances will be used at any particular time - should I just wire 3 of the buildings to phase 1, 3 to phase 2 and 2 buildings (plus miscellaneous stuff) to phase 3?

Simon

[elkangorito]

OK - thanks for the info.

Also, can anyone advise me how important it is to try to 'balance' the 3 phases? I have 5 bungalows and 3 other buildings. Since I have no idea which rooms will be occupied and which appliances will be used at any particular time - should I just wire 3 of the buildings to phase 1, 3 to phase 2 and 2 buildings (plus miscellaneous stuff) to phase 3?

Simon

Hi Simon,

I think what you have been quoted for your txer (transformer) sounds quite reasonable. I feel that others reading your post may not fully understand the "33kV" part. A txer of such a high step-down ratio & KVA rating can certainly NOT be compared to that of a standard 3.3 or 11kV txer.

As far as phase balance is concerned, it is impossible to achieve a perfect load balance under domestic/commercial conditions. Subsequently, the secondary winding of the txer will be in "star" configuration & the "star point" is used as the neutral. The "out of balance" current for a 3 phase load will therefore run through the neutral. Theoretically, if a 3 phase load is perfectly balanced, current should not be flowing through the neutral. Since the txer secondary will also supply single phase loads, the neutral conductor will always carry "out of balance" current.

Also, the "star point" of the txer secondary should be earthed at the location of the txer. This is to facilitate the use of the MEN links in downstream installations.

Also, you may find it advantagous to conduct a maximum calculation before you decide on how many phases to connect to each building etc. See the link below.

http://www.thaivisa.com/forum/index.php?ac...st&id=10619

Edited August 17, 2006 by elkangorito

[simon43]

Thanks for the info Elkangorito. Yes, the 3 phase will be in star configuration, so I can ground the star point as suggested.

I already have a maximum calculation for the resort. I was just thinking along the lines of 'what if bungalow 1 is empty and bungalow 2 is occupied but the aircon is off and bungalow 3 is occupied with aircon and water heater on etc etc'.

As you say, it is impossible to completely balance the system at all times. So I will distribute the single phase supply to each bungalow between the 3 available phases.

The primary supply is 33KV, and because it is apparently not allowed for 33KV lines to cross the road to us, (we are directly opposite these lines), the PEA has to run the supply some 65 metres from the nearest accessible point on our side of the road.

Simon

[chownah]

Couldn't you put the transformer directly across from you on the road and run the lowered voltage across the road?

[simon43]

Chownah - can't do that. Across the road is on airport land......

Simon

[elkangorito]

Thanks for the info Elkangorito. Yes, the 3 phase will be in star configuration, so I can ground the star point as suggested.

I already have a maximum calculation for the resort. I was just thinking along the lines of 'what if bungalow 1 is empty and bungalow 2 is occupied but the aircon is off and bungalow 3 is occupied with aircon and water heater on etc etc'.

As you say, it is impossible to completely balance the system at all times. So I will distribute the single phase supply to each bungalow between the 3 available phases.

The primary supply is 33KV, and because it is apparently not allowed for 33KV lines to cross the road to us, (we are directly opposite these lines), the PEA has to run the supply some 65 metres from the nearest accessible point on our side of the road.

Simon

Hi Simon.

Forgot to tell you that even though you may be paying for the transformer, you may not have any influence upon how it will be connected. I refer to the earthing of the "star point". This matter will most likely be totally controlled by the PEA, which is yet another reason why the MEN system is not widely used here. If only the local electrical authorities would install this 1 very important cable on more transformers . Of course, an MEN system can still be used without hazard but it is less effective (higher earth fault impedances without this cable).

[Colin horn]

Can any one tell me how much is it to service a 50kva transformer that supplies my house