Paralleling power without switchgear

[Jide A.]

I wanted to know if it is possible to parallel power form the utility and a generator without the use of a switch gear.

thanks.

 

[iwire]

At the very least you would need a cogeneration agreement with the power company and some sort of controls to match sync the two sources.

But this question worries me, what do you have in mind?

 

[Jide A.]

i recommended using a switch gear but the boss wants to know if a manual transfer switch can be used to achieve the same thing.

 

[ron]

Is this a pure functional question or a code compliant method question?

You can do it with a closed transition ATS, or circuit breaker pairs in Switchboards / Switchgear with proper protection and control.

 

[Jide A.]

it is a functional question.

 

[eHunter]

I wanted to know if it is possible to parallel power form the utility and a generator without the use of a switch gear.

thanks.

Not reliably or safely.
Paralleling switchgear that synchronizes voltage, frquency and phasing on all buses before closing the connections and incorporates the proper protection relays is required. Anything less would be unsafe and a catastrophy waiting to happen.

See NEC article 705.
Connecting generating devices to a regulated utility also has legal elements as well, usually at the state, possible at the federal level.
The utility also has rules and requirements for connecting generating equipment to their system and are usually on a contractual basis.

 

[GoldDigger]

i recommended using a switch gear but the boss wants to know if a manual transfer switch can be used to achieve the same thing.

Pretty much by definition a transfer switch will not allow the two inputs to be paralleled, except maybe for a strictly limited time during the contact switching transition. But even then it would not really be suitable for all purposes.
Some uses will require a break-before-make transfer switch. Like, among others, if you do not have the capability to synchronize before transferring.

 

[eHunter]

i recommended using a switch gear but the boss wants to know if a manual transfer switch can be used to achieve the same thing.

If the job is permitted and inspected, the simultaneous connection of a generator and the utility will have to meet certain standrds set forth by UL and the NEC, meet the requirements of the utility and the AHJ.
That will entail the proper installation of the proper UL listed equipment including paralleling switchgear.

A manual transfer swith is designed to prevent simultaneous connections of the power sources ie the generator and utility, so no a manual transfer switch will not operate as you described.

How large of a system and what nominal voltage?

 

[Bwas]

There are multiple generator manufacturers that claim they can parallel with utility or multiple generators with their control panels. I have never used one though.

 

[RichB]

I disremember all the details but,,, back in the Navy days I remember being told that when doing testing someone brought two generators in parallel and I think they said it was 180 degrees out, that it ripped one genny out of its mounts and blew the switchgear off the wall--like I said--I disremember all the details but I do know bringing a 1750KW Stewam generator on line one fine day as an EM2--I came in around 10 or 15 degrees out of phase and the whole carrier knew it--BAAAWAAANNNNGGG!!!-- never until then knew sound powered phones could go absolutely silent--not even background static:ashamed:

 

[zog]

I disremember all the details but,,, back in the Navy days I remember being told that when doing testing someone brought two generators in parallel and I think they said it was 180 degrees out, that it ripped one genny out of its mounts and blew the switchgear off the wall--like I said--I disremember all the details but I do know bringing a 1750KW Stewam generator on line one fine day as an EM2--I came in around 10 or 15 degrees out of phase and the whole carrier knew it--BAAAWAAANNNNGGG!!!-- never until then knew sound powered phones could go absolutely silent--not even background static:ashamed:

I was test guy in the Navy when we were testing a static replacement for MG sets (PWM Based). One of our tests was to see how far out of phase we could paraell them, at 10 degrees they required about 20 fire extinguishers.

 

[GoldDigger]

There are multiple generator manufacturers that claim they can parallel with utility or multiple generators with their control panels. I have never used one though.

And their "control panels" contain the same functional elements as "paralleling switchgear"!

 

[RichB]

I was test guy in the Navy when we were testing a static replacement for MG sets (PWM Based). One of our tests was to see how far out of phase we could paraell them, at 10 degrees they required about 20 fire extinguishers.

I was guessing at the 10 -15 degrees--it was at the 1 to 1:30 o'clock position on the synchro meter--12 o'clock being dead on and 6 o'clock being 180 out

We had the design engineer from Radiation Systems Inc on board upgrading our 400hz MG's(300kw units--only had them on the Kitty Hawk and constellation)--when we went to put one of them online I was getting permission from the load dispatcher to parrallel and he just reached over and closed the Gen CB-:jawdrop:-we freaked out--the load dispatcher was yelling at us-:rant:-then we explained our procedures to him after everyone calmed down a bit and he then proceeded to tell us that "it's 400 cycle--it'll lock in--don't worry:thumbsup:"

 

[zog]

Our 400hz sets were horrible, always had issues with them.

 

[Bwas]

And their "control panels" contain the same functional elements as "paralleling switchgear"!

Yes but without the separate switchgear. Hence paralleling power without switchgear.

 

[eHunter]

Yes but without the separate switchgear. Hence paralleling power without switchgear.

OK, name the manufacturers and the models.

 

[RichB]

Our 400hz sets were horrible, always had issues with them.

our 300kw sets were ok--but when they went down they went down hard--the 100's seemed to just chug along forever no matter what--and all the little 5 and 10's just ran and ran--kinda like the energizer bunny

 

[kingpb]

OK, name the manufacturers and the models.

My guess is they are referring to the control panels on the DEG sets that do have the ability to talk to each using a single shielded twisted pair, and set operating mode, etc. and work as master/slave arrangement, but they have limits.

This should not be confused with paralleling switchgear with protection functions and metering.

I am fairly certain in saying you will not be legally paralleling with the utility unless you have a power purchase agreement in place and the design meets their interconnection requirements.

If you do parallel illegally, prepare yourself for a lwasuit and damages when someone is injured or killed do to you feeding power into the utility system unbeknown to them as a worker is working on the line and the gen decides to run.