why did not apply the PLC in the electric power industry

[ymh]

in electric power system,there exist a large number of relay circuits,why isn't the PLC applied at large? Are there some infeasible technologe reason? I would be appreciate if you could tell me.

 

[rsdoran]

Its simple

MONEY

AND the old philosophy of "IF IT AINT BROKE DONT FIX IT"

 

[Jnelson]

I used to work on printing presses like komori, heidelberg, miller, etc. It always amazed me that even up until that time, they never changed over to plc's. Still had large relay panels, and this was only a couple of years ago. I think RS hit it on the head!

If it aint broke, don't fix it.

John

 

[Jiri Toman]

not so

I don't know what specifically you are refering to, but in as far as the Cogeneration systems go you can certainly specify PLC to be at the heart of your controls. In fact you would be stupid not to.
Fairly modest cogen system would need hundreds of relays to accomplish the required control tasks.
You will also need traditional safety and protective relays in addition to PLC. If you are refering to these devices I don't think that they will be a part of the PLC system anytime soon.

 

[rsdoran]

I made my reply because I took it that ymh was refering to system(s) he has seen in use within the electric utility industry. I took electric power system to mean the electric company. This may be incorrect maybe ymh can clarify.

On the other hand a power system has to have fail safes (hardwired circuits) in many situations which is why relays and mechanical devices are and will probably continue to be used for a long long time.

I agree in a sense with Jiri that a plc could be specified in many applications...without more details on what power systems you are refering to it would be hard to say. Using a plc is not an automatic decision, many factors have to be considered. In some cases a plc would be overkill, in others it may not have the processing capabilities needed.

The real reason is it DEPENDS.

The OTHER reason I have already stated.

 

[Gerry]

ymh,

If you ever visit New Zealand, then there is an abundance of examples of PLC use in generation, distribution, and system control all around.

 

[BobB]

I do a lot of co-generation and SCTT (soft transfer) projects and all are PLC controlled. I also much prefer to use an Australian made generator controller manufactured by Dawson Technologies. They have several models of Si-TEC, TGC (total generator control), CGC (co-generation control), a master controller for up to 32 CGC controlled sets and a time module to make up time for power outages in power stations.
I have also implemented several power stations with PLC control. I am going back to one of them shortly to upgrade all the HV protection with GE-Multilin SR489 generator protection relays and GE-Multilin 750 feeder protection relays.
The power station is fully automatic with 6 diesel generators, 3 x 1.5mW, 1 x 2.8mW and 2 x 4.1mW sets. Generation is at 11kV. Automatic load control, frequency shedding, lead set selection, lock out set for maintenance etc etc, all from a SCADA computer running Citect. 9 networked Omron PLCs with remote I/O, fuel system control etc etc.
If a set falls over and there is a blackout, the PLC system starts up another set and re-establishes the supply to the customers.
Also, in the state of New South Wales where I live, much of the control of the power stations is by PLC. The whole grid for the state is also controlled by PLCs. The system is based on Toshiba brand. Control of power to about 10 million people.
beerchug

 

[Allen Nelson]

Who says that they don't use PLCs in the electric power industry?

Aboout a year and a half ago I was on a startup of a new coal-fired power plant. The technology - DCS and PLCs.

My old company used to sell their own brand of PLC for monitoring/control of substations (http://www.tasnet.com/ - I think that they're defunct now. If anyone has any dealings with them, tell them that they owe me money).

At a chiller plant for a university that I put in four years ago, the switchgear was controlled by a GE PLC.

A decade ago, I actually had to deliver a PDP-11 to a nuke plant, because that was what they used to control things, and it had been validated, and so that was what they had to use. OK, a PDP-11 isn't exactly a PLC (more like a vintage XT IBM PC, about the size of desk. I think today you can buy a wristwatch with more computing power. I have no idea where we dug that beast up.). But when the place was built, PLC's weren't even a glimmer in Dick Morley's eye yet.

And that's the other answer - time (along with money). Most of the electrical infrastructure was built pre-PLC. It works (except for an incident in the northeast this past summer) and hasn't NEEDed changing.

But that goes back to what Ron and 'cousin' John said, "If it ain't broke, don't fix it".

 

[Terry Woods]

HOLY $HIT, ALLEN !!! A PDP-11 ???

I used one when I worked in Television/Radio/Data Microwave Communications. I haven't used one of those for years! I had to enter code, in 1's and 0's by TOGGLE-SWITCH / ENTER !!!

Talk about yer Bit-Weenie !!!