Something about WindLDR (had me fooled)

Hi

I have spent almost a week trying to catch bugs in this program done with the Idec Microsmart PLC. At first I thought I found some but end up back at square one after finding that it's not an error at all. Let me explain the problem faced by an engineer on the site itself:

There are 2 generator sets running only when needed, and its plc communicating with a master control plc. The master plc deals with load demand (for the callup of these 2 gen sets as well as to shut them down when not needed). Gen number 1 holds first piority when a startup is given and gen number 2 gets the second pirority for a follow call-up. When gen number 1 is already running and gen number 2 is being called up to assist gen number 1, a synchronizing process will take place before the breaker could close to start load take up. The process will be that a call up will be initiated when a load percentage has reached 80% or more, and a shut-down when a load percentage has reached 35% or less.

Problem now is that the engineer there maybe did not know the load operation. He wrote "G-1 and G-2 run parallel over half an hour event though Load percent is only 50% on G-1 at this paralleling period and G-2 did not exit to cooldown." If he was expecting one gen to unload and cooldown when total load on gen number 1 is at 50%, then he is wrong. 2 generators are running, so I had assumed that the total load had been pretty high (assumed above 80%), and later it went down to 50%. So in this given case, gen number 2 will continue to run and share the load with gen number 1 until load has furthered reduced to less than 35%.

So I explained the same to the site engineer but he insisted it has a problem with the master program. I told him de-energise and re-energise the PLC and see if it is a short software jam. (that problem has happened before). So here I attached a pdf format of the program for all to share. I looked at it and it seem alright to me. But please direct me if you guys can detect any faults. I think a different group of people can better see the flaws than I do. Let it also be a good study reference for those interested.

I hope it isn't any big problem. Enjoy!

regards
Sherine T.

Syncronizing generators is a big deal. You can screw **** up quickly. My dad was EE power distribution for big ships (now retired). You need some very good switch gear. In general you syncronize frequency (within a range) and bring on line the generator you just started at a higher voltage. I see that your problem is more on deciding when to bring additional capacity on line and when to take it out. Commets and labels would be nice.

Forgot to tell you that some generators behave as loads if you don't bring them on line correctly.

Yes danpantea.

That would be a cause of reverse power, due to phase difference, load ratio, power factor etc.
Lucky this one controls only the smaller generators. I should think it's the Catepillar G3512E.
I am so sorry this program has come to such a mess, but it's an upload from the plc itself, and i only managed to insert a few labels and comments..most of it being codings for easier read through for the rest of my colleagues.

regards
Sherine T.

My main business is generator control. Once used to it, it is really pretty easy. I find the secret is to use very good generator controllers. My preference, by far, are the Si-TEC controllers made in Ozz but they are expensive. Second choice is Woodward EGCP2 but they have their problems. Deep Sea are good for only the very simplest of projects.

Favourite PLC is Omron CJ1 - no rack and cheap but with awesome function list and great comms.