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parallel utility for load bank 5
- Thread starter ronnied
- Start date
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1
- #2
davidbeach
Electrical
The generator controls will need the capability of controlling the watts and vars out of the generator; machines intended only to supply standby load, whether paralleled with other standby generators or only stand alone, may not have this capability.
An autosynchronizer that can synchronize the group of generators to the utility. Right now your installation is likely to have individual autosynchronizers that sync the second and third generators to the first generator, but without the capability of controlling the whole group.
Protection at the point of common coupling that meets the requirements of the serving utility. Since that point of common coupling doesn't exist now, that protection is unlikely to exist. IEEE 1547 applies in the US and probably Canada and would be a useful starting point elsewhere. I not know what IEC standard(s) would be a starting point in that part of the world.
An interconnection agreement with the serving utility. The agreement will include the protection requirements, but will have a number of other requirement that can vary from utility to utility and region to region.
An autosynchronizer that can synchronize the group of generators to the utility. Right now your installation is likely to have individual autosynchronizers that sync the second and third generators to the first generator, but without the capability of controlling the whole group.
Protection at the point of common coupling that meets the requirements of the serving utility. Since that point of common coupling doesn't exist now, that protection is unlikely to exist. IEEE 1547 applies in the US and probably Canada and would be a useful starting point elsewhere. I not know what IEC standard(s) would be a starting point in that part of the world.
An interconnection agreement with the serving utility. The agreement will include the protection requirements, but will have a number of other requirement that can vary from utility to utility and region to region.
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1
- Moderator
- #3
I am not sure what you mean by "Sync" Do you mean running in parallel or load sharing? Are you trying to improve load sharing on standby generators? What type of governors do you have?
To connect to the utility:
You will need a synchroscope to be able to synchronize with the utility. One synchroscope and a three way selector switch is the cheapest.
You will need a wattmeter on each generator to monitor the loading. This is probably included in the generator instrumentation.
You will need an ammeter on each generator to monitor the current. This is probably included in the generator instrumentation.
You will need a voltmeter on the mains and on each generator to set the voltage. This is probably included in the generator instrumentation.
YOU WILL NEED THE PERMISSION OF THE UTILITY.
The utility will probably have additional requirements.
When the utility turns you down;-
Consider a couple of dumpsters filled with salty water. Use leaf springs from a heavy truck for electrodes. Obtain the springs at the scrap yard. It's a very economical load bank for a one time use. Be prepared to use lots of water.
I've boiled a lot of water this way.
Note; If load sharing is a problem, the solution is often to sdjust the "Droop" characteristic of the governors. This can be donw one machine at a time. If these are standby sets and you can connect one at a time to the utility and call it peak sharing you can set the droop quite easily.
good luck
yours
To connect to the utility:
You will need a synchroscope to be able to synchronize with the utility. One synchroscope and a three way selector switch is the cheapest.
You will need a wattmeter on each generator to monitor the loading. This is probably included in the generator instrumentation.
You will need an ammeter on each generator to monitor the current. This is probably included in the generator instrumentation.
You will need a voltmeter on the mains and on each generator to set the voltage. This is probably included in the generator instrumentation.
YOU WILL NEED THE PERMISSION OF THE UTILITY.
The utility will probably have additional requirements.
When the utility turns you down;-
Consider a couple of dumpsters filled with salty water. Use leaf springs from a heavy truck for electrodes. Obtain the springs at the scrap yard. It's a very economical load bank for a one time use. Be prepared to use lots of water.
I've boiled a lot of water this way.
Note; If load sharing is a problem, the solution is often to sdjust the "Droop" characteristic of the governors. This can be donw one machine at a time. If these are standby sets and you can connect one at a time to the utility and call it peak sharing you can set the droop quite easily.
good luck
yours
- Thread starter
- #5
I hear a lot of people talk like the utility will not allow paralleling but at my company we have gotten approvals, but never used it. However, the people here believe too that the day we ask for it we will get "what did you say, or I can't hear you, or your are breaking up call back later, etc." Is that what you guys are saying?
- Moderator
- #6
Hello ronnied
I agree, many companies are selling power to the utilities.
Getting permission may be fairly straightforward. That doesn't mean it will be fast or cheap.
Your proposal will most likely have to be evaluated.
The utility will have protection requirements to protect their system in the event of a fault. They will probably re-assess the available fault current levels in their system in the area that will be affected by the extra available current from your generator. The Utility will certainly demand that you install a protective relay system and that won't be cheap.
The utility may well allow paralleling and backfeeding, but the conditions that must be met make it very unlikely that the utility will even consider it for a few hours or days of load testing.
Rent one or more 40 cubic yard dumpsters (The big ones, 20 feet long) buy a 50 lb. sack of salt and 10 rolls of "Duck" tape to seal the tailgate. Use scrap iron for electrodes.
Plan on having a hose for makeup water. you are going to be boiling a lot of water.
respectfully
I agree, many companies are selling power to the utilities.
Getting permission may be fairly straightforward. That doesn't mean it will be fast or cheap.
Your proposal will most likely have to be evaluated.
The utility will have protection requirements to protect their system in the event of a fault. They will probably re-assess the available fault current levels in their system in the area that will be affected by the extra available current from your generator. The Utility will certainly demand that you install a protective relay system and that won't be cheap.
The utility may well allow paralleling and backfeeding, but the conditions that must be met make it very unlikely that the utility will even consider it for a few hours or days of load testing.
Rent one or more 40 cubic yard dumpsters (The big ones, 20 feet long) buy a 50 lb. sack of salt and 10 rolls of "Duck" tape to seal the tailgate. Use scrap iron for electrodes.
Plan on having a hose for makeup water. you are going to be boiling a lot of water.
respectfully
davidbeach
Electrical
It all depends on the utility. Some make it easy, other make it difficult. If you have an interconnect agreement with your utility, go for it; if the agreement is in place and you comply with your requirements, they will not keep you from running in parallel.
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1
- #8
rcw retired EE
Electrical
I have worked on many systems like you are describing, and placed many into service. Other facilities could not succeed for the reasons already mentioned.
One facility could not parallel with the utility because their circuit breaker closing device was too slow. The generators would get out of synch in the 5-7 seconds it took the breaker poles to close after the the synchronizer sent the clsoe signal. Replacing the breaker was too expensive so the project was abandoned.
Others failed because the cost of converting a transfer switch to a circuit breaker was too high.
At another facility the resulitng short circuit duty with both the utilty and the generators on line was greater than the equipment ratings, so the project was halted.
Another one paralleled fine, but the protection system coordination was lousy. Relays and fuses that coordinated well with current flow in one direction did not coordinate at all with power flow the other way.
Two other systems paralleled OK with the uility at 4160 kV with no problem until a ground fault occurred. The wye-wye step up transformers and solidly grounded generators caused selectivity problems and dumped the hospital for every minor utility system fault. Another one tripped the emergency room feeders due to circulating neutral currents between the utility transformer and the generator.
One new plant paralleled fine through the A bus several times, then blew the gear apart when they tried to synch to the "B" bus through the tie breaker. A phasing problem in the controls and the "B" transformer was not picked up by the engineer. (We were called in after the smoke was let out.)
So - talk to the utility, check your generator controls, check the short circuit ratings, do a load flow study, check the protective relay settings and review them with the utility. Then check it all again and hire a good startup and testing team to verify everything.
One facility could not parallel with the utility because their circuit breaker closing device was too slow. The generators would get out of synch in the 5-7 seconds it took the breaker poles to close after the the synchronizer sent the clsoe signal. Replacing the breaker was too expensive so the project was abandoned.
Others failed because the cost of converting a transfer switch to a circuit breaker was too high.
At another facility the resulitng short circuit duty with both the utilty and the generators on line was greater than the equipment ratings, so the project was halted.
Another one paralleled fine, but the protection system coordination was lousy. Relays and fuses that coordinated well with current flow in one direction did not coordinate at all with power flow the other way.
Two other systems paralleled OK with the uility at 4160 kV with no problem until a ground fault occurred. The wye-wye step up transformers and solidly grounded generators caused selectivity problems and dumped the hospital for every minor utility system fault. Another one tripped the emergency room feeders due to circulating neutral currents between the utility transformer and the generator.
One new plant paralleled fine through the A bus several times, then blew the gear apart when they tried to synch to the "B" bus through the tie breaker. A phasing problem in the controls and the "B" transformer was not picked up by the engineer. (We were called in after the smoke was let out.)
So - talk to the utility, check your generator controls, check the short circuit ratings, do a load flow study, check the protective relay settings and review them with the utility. Then check it all again and hire a good startup and testing team to verify everything.
- Thread starter
- #9
Can you explain how to do the procedures you have referenced and provide the Manufacturers part numbers for the components/equipment you recommend?
The test procedure to use the utility load was to save money over buying load banks, so I can not use the salt water test, but it will be a good reference for another project.
The test procedure to use the utility load was to save money over buying load banks, so I can not use the salt water test, but it will be a good reference for another project.
- Moderator
- #11
While many of our members have first hand experience paralleling with utilities, it is the utility who dictates the protection that is required. Then, there is a lot of engineering required to select, adjust and co-ordinate the various protection devices.
This is not something that you can safely or legally do without co-ordination with the power company.
The utility will notice and investigate if you try to sneak 3 two kilowatt loads onto the system.
yours
This is not something that you can safely or legally do without co-ordination with the power company.
The utility will notice and investigate if you try to sneak 3 two kilowatt loads onto the system.
yours
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2
- #12
Don't you hate when you do that waross?
I do it all the time.![[cry]](/data/assets/smilies/cry.gif "[cry] [cry]")
Keith Cress
Flamin Systems, Inc.-
I do it all the time.
Keith Cress
Flamin Systems, Inc.-
- Moderator
- #13
- Thread starter
- #14
I guess I was unclear; I am not trying to get around the utility. The plant has failing loadbanks and are considering purchasing new, but someone said if we were paralleling with the utility we did not need to purchase the loadbanks just use the utility - is this islanding?
I was asking for more details of what to look for or ask for when talking to the manufacturers of the new components you all said I would need like the master sync, or autosync and 3way switch. Also, how can I perform task like short-circuit calcualtions, or protective relay coordination without an expensive program?
Finally, can anyone explain manual sync using the Operator Window technique and a sync check relay, it is supposed to be a dummyproof method to sync the gensets to each other and/or the utility, and how should that work with the gensets in a 2+1 configuration?
I was asking for more details of what to look for or ask for when talking to the manufacturers of the new components you all said I would need like the master sync, or autosync and 3way switch. Also, how can I perform task like short-circuit calcualtions, or protective relay coordination without an expensive program?
Finally, can anyone explain manual sync using the Operator Window technique and a sync check relay, it is supposed to be a dummyproof method to sync the gensets to each other and/or the utility, and how should that work with the gensets in a 2+1 configuration?
- Moderator
- #15
1> If you are paralleling with the utility already, just open the governors up a little and you will back feed and load up the sets.
2> Synchronizing. The basic method is synchronizing lights. The next step is a synchroscope. This tells the operator whether the unit coming online is running fast or slow, and when the phase relationship is right for synchronizing. Both these methods check phase relationships only. It is the responsibility of the operator to check that the voltages are equal before closing. There are relays to completely automate this procedure and also check and adjust the voltages.
"Also, how can I perform task like short-circuit calcualtions, or protective relay coordination without an expensive program?" This is a little more than we may be able to teach you in this forum. Much of the shortcircuit calculations will be preformend by the utility engineers to determine how the added capacity will affect the utility system. If you are already paralleling, this will have already been done.
You need to talk to an expert.
The first experts will be the engineers at the utility. They will tell you what they require for protection. Then you will need an engineer to design and install the system.
I understand that you may be in a position such that you have to gather a lot of basic information and pricing before you can get authorization to spend any money. There are still experts available that will help you at no cost. They are called "Sales Reps."
First, talk to the utility, then, start looking for sales reps for information and pricing on the equipment.
A quick run through, you will need a breaker or contactor to connect the plant to the utility. You will need a breaker or contactor to connect the plant to the genset. This is fairly straight forward. Now if you close both breakers at the same time, you are paralleled.
When the plant was originally designed, short circuit calculations were done to ensure that all the breaker were selected and co-ordinated so that a serious short curcuit could be interupted without any of the breakers failing.
Now, if you add 6 megawatts of power to the system by paralleling, the available fault current increases for the system. The original calculations for both your plant and for neighboring industrial plants is no longer valid. This maens that with your generators on-line, a serious short circuit at another plant may result in a breaker exploding rather than interupting the current.
Among other things, the utility will now meter current in both directions.
Paralleling is done one step at a time. Once a set is paralleled with the system it is part of the system. Then the next set is paralleled with the system.
You don't parallel all three sets and then connect them as a group to the system. There is another recent thread where a gentleman is trying to do some tests with unloaded gensets in parallel. To find out why you don't want to parallel unloaded generators check out thread238-153502
I hope this helps
yours
2> Synchronizing. The basic method is synchronizing lights. The next step is a synchroscope. This tells the operator whether the unit coming online is running fast or slow, and when the phase relationship is right for synchronizing. Both these methods check phase relationships only. It is the responsibility of the operator to check that the voltages are equal before closing. There are relays to completely automate this procedure and also check and adjust the voltages.
"Also, how can I perform task like short-circuit calcualtions, or protective relay coordination without an expensive program?" This is a little more than we may be able to teach you in this forum. Much of the shortcircuit calculations will be preformend by the utility engineers to determine how the added capacity will affect the utility system. If you are already paralleling, this will have already been done.
You need to talk to an expert.
The first experts will be the engineers at the utility. They will tell you what they require for protection. Then you will need an engineer to design and install the system.
I understand that you may be in a position such that you have to gather a lot of basic information and pricing before you can get authorization to spend any money. There are still experts available that will help you at no cost. They are called "Sales Reps."
First, talk to the utility, then, start looking for sales reps for information and pricing on the equipment.
A quick run through, you will need a breaker or contactor to connect the plant to the utility. You will need a breaker or contactor to connect the plant to the genset. This is fairly straight forward. Now if you close both breakers at the same time, you are paralleled.
When the plant was originally designed, short circuit calculations were done to ensure that all the breaker were selected and co-ordinated so that a serious short curcuit could be interupted without any of the breakers failing.
Now, if you add 6 megawatts of power to the system by paralleling, the available fault current increases for the system. The original calculations for both your plant and for neighboring industrial plants is no longer valid. This maens that with your generators on-line, a serious short circuit at another plant may result in a breaker exploding rather than interupting the current.
Among other things, the utility will now meter current in both directions.
Paralleling is done one step at a time. Once a set is paralleled with the system it is part of the system. Then the next set is paralleled with the system.
You don't parallel all three sets and then connect them as a group to the system. There is another recent thread where a gentleman is trying to do some tests with unloaded gensets in parallel. To find out why you don't want to parallel unloaded generators check out thread238-153502
I hope this helps
yours
What you are talking about - "just" using the utility as a "loadbank" - will be at least as expensive (in my guesstimate) as buying one new load bank you share between the four units.
Assuming the utility allows it, it's likely that you'll have to present a grounded source to the utility (that means a wye-delta or some other grounding source for the high-side of your utility connection), that you'll need distance relays (not cheap), bus differential relays and many other protective functions for both the utility and your generators that you probably do not currently have, you may have ground-fault concerns, available fault-current concerns, you may need different utility and generator control switchgear, you'll need power-factor and generator loading controls, special synchronizing controls, probably a PLC or set of PLC's to control this whole deal, plus a whole new set of safeties designed to trip your plant and/or generators off line in case of a fault.
There are good reasons to go through all these steps, I would not think "load banking" would be one of them. The cost is not justified.
Assuming the utility allows it, it's likely that you'll have to present a grounded source to the utility (that means a wye-delta or some other grounding source for the high-side of your utility connection), that you'll need distance relays (not cheap), bus differential relays and many other protective functions for both the utility and your generators that you probably do not currently have, you may have ground-fault concerns, available fault-current concerns, you may need different utility and generator control switchgear, you'll need power-factor and generator loading controls, special synchronizing controls, probably a PLC or set of PLC's to control this whole deal, plus a whole new set of safeties designed to trip your plant and/or generators off line in case of a fault.
There are good reasons to go through all these steps, I would not think "load banking" would be one of them. The cost is not justified.
davidbeach
Electrical
tommom, in general all good points except that it is highly unlikely that a distance relay would be required. Utilities don't, in my experience, use distance on distribution circuits and IEEE 1547 does not require distance for an interconnect.
Why can't you just use your "plant" as a load bank?? Find a reasonable chunk of your plant, something/area under 2000kW and isolate it. Run it with one of your three generators then as time passes start the next generator, parallel them and drop the first.
Step through each one as needed. This lets you get the full value for your electricity whereas the utility will probably discount what you send to them. You shouldn't need much else perhaps some work to properly section part of your plant. You wouldn't need any permissions from the utility.
You could possibly use tommom's PLC suggestion to shut down the part of your plant briefly and bring it back up on the generator.
Keith Cress
Flamin Systems, Inc.-
Step through each one as needed. This lets you get the full value for your electricity whereas the utility will probably discount what you send to them. You shouldn't need much else perhaps some work to properly section part of your plant. You wouldn't need any permissions from the utility.
You could possibly use tommom's PLC suggestion to shut down the part of your plant briefly and bring it back up on the generator.
Keith Cress
Flamin Systems, Inc.-
A star for Keith (itsmoked). duh, why did not I think of that?
Utiltiy co. is more likely to accept a closed trasition (soft) transfer than someone feeding back power to them at their convenience. And you need the same parallleing protective relaying, only slightly less complicated than runninng in parallel with utiltiy for extended time.
Utiltiy co. is more likely to accept a closed trasition (soft) transfer than someone feeding back power to them at their convenience. And you need the same parallleing protective relaying, only slightly less complicated than runninng in parallel with utiltiy for extended time.
davidbeach
Electrical
The problem with using the plant as the load is the need to drop the plant twice, often unacceptable. I fully understand the desire for using the utility as the load, the plant would actually supply at least the bulk of the load, if not all of it, but it is necessary to parallel to the utility to get to the plant load. Having the ability to parallel to the utility also makes it possible to come back from a utility outage without the need for a second interruption (the first being when the utility dropped out); a parallelable system can also be smoothly moved from the utility to local generation as a storm avoidance measure. All valid reasons to want to parallel, but the paralleling has to be done correctly. This forum probably isn't the best place to learn how to do that however. There have statements from ronnied that suggest he (she?) is getting in over his head and should really engage the services of a local consultant who understands the details of parallel operation with the utility and the requirements of the specific serving utility.
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