Way to Save Energy Bill By Power Down STand-by Transformers

[chlee-penang]

Hi,

I have a question seeking member's advice pertaining to operational safety and energy saving.

We have 4 sub-station each equipped with 2 transformers (1 station 11KV/6.6KV 10 MVA, 3 other stations 11KV/.433KV 2MVA) on 2x100% stand-by configuration , secondary feeding to two bus sections with a bus-coupler. Currently both transformers are supplying concurrently to the load with Bus-coupler OFF in one Sub-station, others carrying total connected load by one of the two transformers only.

As an effort to reduce energy cost, I intend to switch out one transformer on each Sub-station to de-energized stand-by mode, when carrying out schedule 11KV stand-by generator load test each month, taking that opportunity to rotate the duty/stand-by transformers too, by doing so, the Free Load losses of transformer can be eliminated.

The question is whether safe to leave the transformer in de-energize state for 1 to 2 month, switch it ON and OFF alternate month?

 

[Besoeker]

We’re back to that again. There’s a big difference between a hospital and an industrial plant where the loss of power is no great shakes.

If the plant can cope with an outage why waste money on unnecessary expensive equipment? Admittedly it’s inconvenient but it’s not the end of the world.

How many places are there with no standby power at all? They manage.

Of course there's a difference. One could potentially cost lives.
The other - well, just jobs.

It is a big deal in a production plant.
I remember sitting having a cup of tea in the electricians' shop in a paper mill. It was during the commissioning phase of some new drives. The usual hurry up and wait that such projects inevitably entail.

Had done a few crosswords, took a spin on Fred's Cotton motorbike. He wasn't far wrong when he said it handled like a wheelbarrow. Slight disagreement on that one - I've had wheelbarrows that handled better.
Bored electrical engineer. So, in the absence of anything more interesting to do, started to read the notices on the notice board. Yes, it can be that bad and sad.. Middle of the night, just waiting and waiting and waiting for a mechanical problem to be resolved.

Picture painted.
Back to the noticeboard. Something that caught my attention - and has stuck with me. "Down time on this machine costs £77 a minute."
The message was clear.
It goes wrong, you move. You get your arse in gear. Instantly.

That was in 1977. In today's money it would equate to quarter of a million a day.

And that's just down time. A power outage? Who knows......

 

[Engineer54]

Back to the noticeboard. Something that caught my attention - and has stuck with me. "Down time on this machine costs £77 a minute."
The message was clear.
It goes wrong, you move. You get your arse in gear. Instantly.

Yep, i can remember during my training days when depending on which line was down, it cost the company between 1500 to 3000 pounds every couple of minutes. After 5 minutes of a line being down it warranted the plant managers presence as well as a host of other dignitaries. Let's just say it didn't happen too often!! lol!!

 

[Besoeker]

Yep, i can remember during my training days when depending on which line was down, it cost the company between 1500 to 3000 pounds every couple of minutes. After 5 minutes of a line being down it warranted the plant managers presence as well as a host of other dignitaries. Let's just say it didn't happen too often!! lol!!

You will probably have gathered by now that we do do variable speed drives, mostly for production machinery. If you hadn't, please pay better attention from now on!!!!!

Because of the cost of down time, we have 24/7 call-out contracts with a number of major customers with guaranteed mobilisation times. That is, someone on their way within a specified time from when the call is made - enough time to get up, have a shower, and not a lot else.

Of course with a continuous process it runs 168 hours a week, Saturdays, Sundays, day and night, high days and holidays. So there is a better than 75% chance that if anything goes wrong it will be anti-social timing.

And, if any of my guys have a problem, they are not averse to calling me at two in the morning. Windmill theatre here it seems like at times.
"We Never Closed"

 

[chlee-penang]

 

[chlee-penang]

Dear Gentlemen,

Thanks for all your kindness in sharing your opinion. I must apologize for not giving the entire picture, I several attempts to paste the MV/LV Distribution Network but failed upload the message, I will try again and hope with the image can clear your doubt.

As we are not allowed to parallel with the national grid, and there is electrical and mechanical interlock to prevent so doing, therefore each time test run the generator with load, at least a section of bus bar has to be completely powered down; it is a common practice here, no generator is allowed to parallel with the grid, with some exception such as handful of Independent Power Producers. Recently there are Solar Power sold to Utility company being export to the grid.

I did commissioned a black start generator for the Utility company, the diesel generator is designed to parallel with station MV Distribution System which is connected to the grid, the site acceptance test with load is done by parallel with station MV Distribution System without power interruption.

 

[chlee-penang]

I paste the entire MV/LV Distribution Network image in Editing mode, it pops up following message:

"The text that you have entered is too long (29790 characters). Please shorten it to 20000 characters long."

I guess there is restriction to the size of image that one can post.

 

[chlee-penang]

Hi Tony,

Thanks for sharing. I see your point now. I learn a lot from you.

 

[chlee-penang]

I made several attempts but fail to paste the MV Dist. Network.

You are right, the generators power is fed through 11KV Bus Bar, but with electrical and mechanical interlock. the interlock is so set up to prevent 1) parallel between two transformers, 2) Parallel between Utility power with generator power.

I am glad to know that you been based in Penang! I wish you did enjoy your stay then.

I am curious how did you bring the stand-by facility without brief power interruption, unless the base is granted the right to parallel the generator with the national grid (I guess is then call NEB or LLN) first before opening Utility Incoming breaker.

 

[Knobhead]

Yep, i can remember during my training days when depending on which line was down, it cost the company between 1500 to 3000 pounds every couple of minutes. After 5 minutes of a line being down it warranted the plant managers presence as well as a host of other dignitaries. Let's just say it didn't happen too often!! lol!!

The joys of being a bad grumpy git. Enter manager “who’s on the job” "TNT" exit manager.

My shift fitter was also called Tony. We didn’t get the nickname TNT for nothing!

 

[Knobhead]

I made several attempts but fail to paste the MV Dist. Network.

I'll PM my e-mail address, send the drawing to me and I'll post it for you. You don't seem to be having a lot of luck.

 

[Knobhead]

This gives a more of an idea of what we had to contend with. It wasn’t the easiest to get your head around.

Again the grid operators equipment is in red our equipment in blue.

The four 33KV main feeds and the two 11KV standby feeds were under the control of the grid operators with but we could lock them out. The grid operators had to isolate them if needs be.

Emergency generators shown in purple at 660V stepped up to 11KV. The generators operated in islanded mode so no synchronisation needed. Only three substations had generators.

E54:
You asked what company would put up with a distribution system that is far from ideal. I’ll ask you, how many companies would pay to totally rebuild that system?
We would need 30MW to keep some semblance of production going. To build a power plant of that size = £XX million. It just isn’t going to happen.

 

[Knobhead]

I’ve had to chop this about a bit but the main bits are here.

I’ll leave it to our friend to add the description.

 

[Engineer54]

Obviously a bit late now after the horse has bolted, like donkey's years ago!! lol!! But where they seemed to think that a standby generator was deemed necessary, then why not incorporate a black start system to cover just the 2 or maybe even 3 VCB'S necessary to accommodate a black start system.

Personally if it was only for the LV distribution system i would have thought the stand-by genny's would be better off being on final LV buses, that are not shown, but i don't know the system being used....

Besides it looks like you'd rarely if ever, loose the total supply on the system you posted above, especially if those 4 incomers were from separate supply sources....

 

[Engineer54]

I’ve had to chop this about a bit but the main bits are here.

I’ll leave it to our friend to add the description.

Gonna have to look at this single line a bit later on ....off to site now, ...yet another bloody meeting!! ..lol!!

 

[Engineer54]

Tony, Can you email the un chopped about layout so i make a bit more sense of the overall layout??

I'll also need wait for the OP systems description too....

 

[Knobhead]

Have fun. Just keep thinking of the bank balance.

 

[Engineer54]

Have fun. Just keep thinking of the bank balance.

Never been much good with cyptic clues?? lol!!

 

[Knobhead]

Tony, Can you email the un chopped about layout so i make a bit more sense of the overall layout??

I'll also need wait for the OP systems description too....

Sent

Now I’ve seen the system it doesn’t make a lot of sense to me either. But like many things, if you don’t know the history, you don’t know how the system evolved.

You once asked me about the systems I worked on saying they were badly designed, they weren’t designed they evolved over many years. Bits added, bits chopped out, it was never ending change. While ever it worked we had to make do with it.

That last drawing of mine, the generators must have moved house more times than me. Originally they were on a plant that was demolished many years ago.

 

[chlee-penang]

I’ve had to chop this about a bit but the main bits are here.

I’ll leave it to our friend to add the description.

Hi Tony,

Thanks for helping out to upload the single line diagram, instead of adding the description, I will probably asking permission from E54 for sending the native PDF file to him for review too.

The red node defines VCB in close position at this moment.

 

[shanky887614]

Hi Tony,

Thanks for helping out to upload the single line diagram, instead of adding the description, I will probably asking permission from E54 for sending the native PDF file to him for review too.

The red node defines VCB in close position at this moment.

could you upload to dropbox and post the link?

 

[Besoeker]

The joys of being a bad grumpy git. Enter manager “who’s on the job” "TNT" exit manager.

My shift fitter was also called Tony. We didn’t get the nickname TNT for nothing!

More bang for your buck??

 

[Engineer54]

Sent

Now I’ve seen the system it doesn’t make a lot of sense to me either. But like many things, if you don’t know the history, you don’t know how the system evolved.

You once asked me about the systems I worked on saying they were badly designed, they weren’t designed they evolved over many years. Bits added, bits chopped out, it was never ending change. While ever it worked we had to make do with it.

That last drawing of mine, the generators must have moved house more times than me. Originally they were on a plant that was demolished many years ago.

Can't remember remarking that your system was badly designed in the past, this is the first time i've seen it. And yes, systems that evolve over time where factory needs get chopped, changed and extended etc, etc do tend to end up not making much sense design wise.

It happened at the company i did my training with, and that had it's own power station. During my time there, virtually the whole system (Well 3 of the main 5 factory MV distribution systems) were completely upgraded and reconfigured including remote and automated switching facilities from main control room. The work was undertaken over 3 years of annual shut down programmes. the main infrusture work being conducted by contractors between the shutdowns....Then 3 weeks of 24 hours a day of pure pandamonium!! lol!!

Most of the costs associated to those changes and upgrades were offset by company tax allowances and incentives....

 

[Knobhead]

Tell me about it.

Rebuild a complete substation in a fortnight. I only went to install a new transformer. I damn near lived at work.

 

[chlee-penang]

Hello Gentlemen,

Thanks for all your interest in this topic. I encounter problem of even uploading small portion of diagram and symbols.

Here is the description, hope it helps.

Red Node : VCB in Close position;
Black Cross : VCB in Open position;
Cross in Circle : Bus Tie;
Green Switch Symbol ; Earth Switch

The Single Line Diagram is showing currently switching status.

 

[Engineer54]

Hello Gentlemen,

Thanks for all your interest in this topic. I encounter problem of even uploading small portion of diagram and symbols.

Here is the description, hope it helps.

Red Node : VCB in Close position;
Black Cross : VCB in Open position;
Cross in Circle : Bus Tie;
Green Switch Symbol ; Earth Switch

The Single Line Diagram is showing currently switching status.

Only had time for a quick overview at the moment, but i find the VCB and COUPLER Open/Closed positions on the 11KV and 6.6 KV switch boards a little confusing. I take it that P1-P2 and P5-P6 are out of service at this time??

What industry is this distribution system supplying power to?? By the looks of things you have 4 incoming 11KV utility supplies coming in to the site, are these incomers supplied from the same utility substation or are they derived from two different utility substations??

I'll have another look at your single line drawing later on....

 

[chlee-penang]

Only had time for a quick overview at the moment, but i find the VCB and COUPLER Open/Closed positions on the 11KV and 6.6 KV switch boards a little confusing. I take it that P1-P2 and P5-P6 are out of service at this time??

What industry is this distribution system supplying power to?? By the looks of things you have 4 incoming 11KV utility supplies coming in to the site, are these incomers supplied from the same utility substation or are they derived from two different utility substations??

I'll have another look at your single line drawing later on....

P1-P2, P5-P6 are outgoing feeder to load, the VCB are always in "ON" position.

Actually there are 2 location sites, site "A" and site "B" about 3KM away form each other. Each site Sub-station is supplied from 2 incoming feeders tapping off from MV Ring Main of Utility company.

The stand-by generators are located in site "A", its back power is feeding to both "site "A" and site "B".

Due to company confidential policy, pardon me not disclosing its details here, one thing I can assure you is, it is a legal facility.

 

[Knobhead]

That explains a great deal, VCB 4 is the open point in the utility local ring.

 

[Engineer54]

P1-P2, P5-P6 are outgoing feeder to load, the VCB are always in "ON" position.

Actually there are 2 location sites, site "A" and site "B" about 3KM away form each other. Each site Sub-station is supplied from 2 incoming feeders tapping off from MV Ring Main of Utility company.

The stand-by generators are located in site "A", its back power is feeding to both "site "A" and site "B".

Due to company confidential policy, pardon me not disclosing its details here, one thing I can assure you is, it is a legal facility.

I was referring to the supply breakers, .... eg, Site 'A' Main Utility Incomer VCB (8) Open, Bus Coupler (7) Open on Main switchboard and Bus Coupler (5) Open on 6.6KV switchboard, means no power to P1-P2 and P5-P6. Also TX 4 doesn't seem to be being utilised.... Yet you show VCB 12 and VCB 6 Closed for TX 2??

As i say, i'm just a little confused with some of the main VCB Open / Closed positions through out the single line drawing....

 

[Knobhead]

To make any sense of the system another drawing is needed showing the condition during normal operation. The last drawing can’t be right.

 

[chlee-penang]

My sincere apology, it is my oversight that the red dot was accidentally moved away from VCB #8.

Normal operation conditions:

Site "A", VCB "ON" position are #6 & #8; #2 & #12;#4 & #6, feeding generator power will require changing over between #4 - #6, or #8 - #10.

Site "A", VCB "ON" position are #5 & #8; #1 & #11;feeding generator power will require changing over between #3 - #5, or #8 - #10.