Distribution Voltage Problems

It sounds as though the distribution grid upstream is facing maximum capacity issues that haven't been addressed. The only thing to do is to moan at the utility supply company and push for an upgrade.

Buy your own generator.

Ok, now that I have said it . . . Buy your own power generator . . . lets explain why. You are in a "brown out" condition. Projection of needs for electric power rarely is accurate . . . combine that with the current world awareness of CO2 release . . . combine that with governmental (be it local or national) environmental restrictions and license requirements . . . construction of large generations stations take years and years . . . oh my, oh my . . . if you are in a brown out, which you obviously are . . . all the evidence indicates only worsening conditions . . . if you don't provide for your own needs and do it now!!! . . . then the time is coming when the voltage fluctuations on the grid will take you to a black out condition . . . and then you will be OUT of Business. I suggest you look back in history it happens and the only answer is to "provide for your own needs".

I agree with and nuke. What is the load on the 3mva transformer?Another thing you might try is to have the utility install regulators on the 33 kv system outside your plant. These can be pole mounted such as the ones found here. http://www.geindustrial.com/cwc/Dispatcher?REQUEST=PRODUCTS&id=vr-1&lang=en_US

Together you may be able to keep the voltage at a reasonable level.

Where are you located?

To step-up or step-down of the 33KV or 11KV voltages to the acceptable range for a power requirement of 3 MVA needs transformer and auto tap changer that will weigh more than 6,000KG.It cannot ( should not ) be pole mounted.The link provided is for problems involving several hundred KVA of power only.

In this case it is clear that the power supplier is not supplying the power at the promised voltage range and they should be given a writen complain so that the authority responsible has to rectify it quickly and any subsequent losses (damaged equipment or loss of production) due to the lower than the minimum level of contracted voltage can be claimed against the energy provider.The same is applicable to over voltage conditions.Install a voltage recorder to gather proof of such condition.

Regards,

Khor.

If you can get the utility to install 10% regulator, when the voltage dips to 375 volts the regulator will adjust the primary voltage so that you voltage at the transformer will be 412 volts. Your regulator should be able to correct this level to 440 volts.

Khor Quote

"To step-up or step-down of the 33KV or 11KV voltages to the acceptable range for a power requirement of 3 MVA needs transformer and auto tap changer that will weigh more than 6,000KG.It cannot ( should not ) be pole mounted.The link provided is for problems involving several hundred KVA of power only".

I did not mention anything about a transformer and tap changer. The product shown is auto-transformer that can be pole mounted. At 33 KV the amperage is only 52 amps. A load of 3 MVA or 3000 KVA is a small load. Utilities in the US do this all the time to improve voltage levels.

Yes, I do agree with the other posts concerning installation of a voltage regulation/auto tap transformer . . . and also that you need to file the necessary paperwork with the supplier of electric power, whether that be a national power company, utility, or private power supplier. You also should be alert to the situation within your municipality, regional or national utitlity or supplier. If you can "see" and I mean look at it!!!; the new construction, or know where the new plant is located and are confident that you will eventually be supplied with a reliable source, even then I would be looking into a "self supplied" source of power. From my personal experience of having been "in the trenches" with the problems in the Philippines during the "brown outs" of the mid-1980's if you wait until the need demands that you have your own source . . . you WILL be out of business . . . simply because once the demand for the "self contained" systems goes up then you will not be able to find one at any price, period!

17 steps on load tap changer is a common design with 0% on the middle tap.8 steps of + 1.5% each and 8 steps of -1.5% on the 33kv side.However in places where brown-out or voltages are often lower than normal levels,it is better to order transformers that has more -ve steps and less number of +ve steps.The price of transformer is about the same for both designs.As on load tap changer which is normally used for power transformer rather than distribution transformer is costlier than the 3 MVA transformer.You may consider using 7 steps x ( 1 step of +2.5% and 5 steps of -2.5% ) off load tapchanger,0 % at tap no:2 .3 MVA 33/0.433KV Dyn11,50Hz,( Primary : 52.48A,Secodary:4173.74A @ 415V.) oil transformer is more affordable.However,the source should not have too high voltage at another time.

Regards,

Khor

If you are in India, the supply system would be hopelessly overloaded. Changing the tapping will only go so far because the increased load of your system will reduce the voltage further. We have been facing this problem for long. We ended up installing our own diesel generators, with a cost per unit at four times the utility supply rate. The state government has aggressively gone in for industrialization of the area to generate employment without planning for the infrastructure. There is no simple control solution for this situation. There just is not enough power to supply all the units.

Indeed there is no simple solution to this situation which also happen in some developing countries.About 15 years ago a friend of mine was trying to arrange for the sale of a power generating plant in the order of 40MVA that was built on a sea going barge which could be towed and anchored in a Vietnamese port and provide quick MV power supply.

I Know India has many capable engineers and commercial/business people.What is needed perhaps is political will and change of legislation and law that can encourage and allow Independent Power Producers who can raise the fund and invest in power generation and retailing in the planed Industrial zones.Certain percentage of the surplus capacity can be sold to the main grid owner who has transmission line but has insufficient power to distribute.The unit price of electrical energy can be predetermined and contracted.The energy price will go up.This is a way to solve a part of the big problem that will get worse because India's economy is now progressing fast.I hope this problem which is more than a technical problem can be solved in the near future,somehow.

Regards,

Khor

Hello Sirs,

Thanks for the prompt reply, we already have three Diesel generators in the plant for standy. But the real problem is that they have to be started manually i mean they do not have the AMF panel, so no auto operation is possible. And the fluctuation in voltage is also very dynamic, and this problem is from 33kv side and is out of our control it is upto power distribution companies hand and even they say they are helpless. so we need to find a solution from our side.

Be very careful here. You haven't stated how much the 33 KV actually fluctuates under extreme load, and how long this condition lasts when it occurs. If your solution doesn't take enough voltage sag into account you could find only a short time solution or worse, an incorrect solution altogether. If you have to use a supplemental power source the duration could change your choices altogether.

Overall . . . I think this discussion has presented bmadhu srao with some very insightful and valuable information on the situation he is in. Generally what we advised industrial clients in the Philippines . . . evaluate you maximum hotel load and add 20 to 50% margin to that. Additionally we looked closely at the individuals specific industry . . . for instance if you are a steel fabrication industry you needs for reliable power are significantly lower than a manufacturer of electronic equipment . . . computer chips as and example. Other response could be to shift your major production efforts to "off peak" times, work more night shifts, less days. In some cases in the Philippines companies went to working from 10pm to 10pm . . . with actual maximum production only until 7 am. If you are going for your own power source . . . go gas turbine . . . yes Diesel driven is less high tech . . . but gas turbines are much more reliable. If you can live with the lower reliability diesels . . . then make sure your controls are modern. An ABT (automatic bus transfer) can be set-up to break you from the off site and bring on the on-site power supplies automatically. The best advice I can give you is get a really good engineer/consultant that has extensive experience in doing this . . . without the support of a really top notch engineer you are only creating a false security that your power is reliable. What ever you do . . . do it as soon as you can.

nukesub629,

You have good experience in surving/tackling poor supply system.I once changed the old diesel engine driven palm oil kernel crushing to electrical motor driven crushers .The factory save a lot of money because the per unit electrical energy at 11kv ( intake supply) is cheaper than 415v supply ( partly used in the office and some new crushers) and very much cheaper than diesel fuel and the maintenance of diesel engines.Another huge incentive was that the national electricity board charged at almost half price per unit during off-peak hours from 10pm to 8am.The worker start the crusher only during the 3rd shift.The complete investment was recovered within 2 years.Another example for using cheaper off-peak power was the cold air conditioning for shopping complexes.Ice sludge of water and some chemical solution (glycol ?) is produced and stored by running the compressors at full capacity during off peak hours.Cold water is circulated to the AHU half an hour before the huge complexes ( 3 to 6 million sq ft ) are opened at 10 am.Aircon consume more that 50% of the energy bill.

Regards,

Khor.

Quote bmadhu " And the fluctuation in voltage is also very dynamic, and this problem is from 33kv side and is out of our control it is upto power distribution companies hand and even they say they are helpless. so we need to find a solution from our side."

I don't see a solution from your side. You have said the generators are not a solution and the utility can not provide the solution. So you have to take some other steps. The solution is the see that your primary voltage level is close to the 33 kv level. When you voltage is 375 volts the utility is at 28 kv. If you installed a 10% voltage boosters in you sub yard you could regulate the voltage and maintain the voltage at 31 kv. This would solve your problem. From your comments the utility is not able to supply the proper voltage so you will have to do it yourself. This is not a major engineering issue. Just do it.

What you simply need now is a good three phase voltage stabilizer with supply of 360v to 450v and output of 420v.Though you did not mention your expected output,but i hope 420v stabilized can take care of your equipment in your production block.

Patrick Whowha

To throw more light on the issue,i would agree with wareagle that you install a 10% voltage booster as said to boost your voltage value at the HT side or LT side in your sub yard.AMF does not matter here.However,since you already have capacitor bank(PFC-Panel) in place,i advise again that you may also calculate your present total load as suggested by nukesub,add 25% tolerance and buy a good three phase industrial voltage stabilizer(Automatic Voltage Regulator) which should be connected in your sub yard.The industrial stabilizer input should be between 360v to 450v with output of 440,420 or 415v whichever suits your expected output voltage since you did not state it.Remember running your plant on utility supply is much more cheaper and will save you cost than burning diesel on generators,as well as the gen.set maintenance costs.Gen.sets are mostly for standby or emergency.

Patrick Whowha