Standby Diesel Generator - Switching Loads Question 1

[scott88]

All,

I have a 3 phase, 415V, 1100kVA diesel generator as an emergency standby,the diesel engine is 1000KW. Currently I have 7 distibution boards that are supplied by 2 incoming feeders from the 6.6kV board. 1 feeder is supplying 2 boards that are conected together by the busbar tie and it is showing 102A 415V load, the other feeder is supplying the remaining 5 boards connected together by the busbar ties and that is showing 383A 415V. We have a board ouage planned on the 6.6kV and I plan to run up the emergency standby diesel and then switch boards across onto it in order to prevent loss of supplies. What is the maximum I can switch onto a generator of that size in one switch? Is their a calculation to show the maximum DOL load at any given time?

Many Thanks.

 

[davidbeach]

The genset manufacturers provide software for just that purpose.

 

[scott88]

Can anyone offer any assitance with the absence of software? This is a permanent standby generator and I do not have access to software. Whilst looking into this I have given consideration to the sizing of a generator for a DOL motor and it is apparent that the required generator is approximately 3 x the size of the motor, is this a good indication if I calculate back from that?

 

[racookpe1978]

As above: Who made the genset and its breakers/speed controller?

 

[catserveng]

If you can access the web you have access to the software, since you didn't provide much detail, start here,

http://www.csemag.com/single-articl...oftware/f6d2adcc3243b14d1e5a2b740e8d6e6d.html

This is a good article that compares the features of some of the software's available the what you need to look for in sizing a generator to a system.

Virtually all of the USA genset manufacturers offer sizing software's for free (all you have to do is register), such as CAT, Cummins, Kohler and Generac.

There are a lot of things that come into to play in sizing a standby for multiple loads, including types of loads, load sizes, and what your system tolerance is for voltage and frequency deviations during transient events.

MikeL.

 

[scott88]

The genset is Rolf Janssen, comprising of a Leroy Somer generator and MTU diesel engine. Protection relay is a Siemens 7UM62 with Siemens controller and synchro relay. The generator is already part of a system, my question is when switching regarding what load I can switch onto the generator supply utilising the bus transfer system at any given time? The generator is designed to provide emergency power in the event of loss of power, I guess this is different because the generator will be ran up, synced and then have loads switched across to it.

 

[waross]

The rated generator output looks like 1530 Amps.
That should have no trouble in accepting a 102 Amp load and a 383 Amp load.
If you are able to sync the standby generator to the grid, then, with the governor in droop mode, you can advance the speed setting until the generator has picked up all the load (or 95% of the load to avoid the chance of getting into power export issues).
Once the load is picked up by the generator, drop out the grid connection. (Or the 6.6 kV feeder.)
The transfer will be easy and seamless.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[crshears]

I agree with Bill, but with one caveat: your local AHJ / utility may not permit the synchronization of your generator with its system / grid; you will therefore want to confirm that paralleling generation with the the grid for a short period to facilitate load transfers is allowed within your local market rules, if there are any...

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[powerjunx]

I saw one commissioning of generator: Maximum load is a composite calculation on each motor started at a time,as;

sQRT3 x V x starting current x PF at starting, Starting current depends starting methods (DOL, Y/D, Auto-trans, etc.)


"..the more, the merrier" Genghis Khan