The typical RTU configuration for I/O counts is as DI- 32 nos. , DO- 60 nos., AI- 56 nos.

We need to select a RTU/PLC which is required for load shedding application in electrical substation. Total loop response time should be less than 200 msec including breaker opening time. considering breaker opening time and interposing relay pickup time requirement is that selected PLC should give overall response time of equal or less than 100 msec. Can anyone suggest which make of PLC/RTU should be selected for such application?

 

I recommend any of the PACs from Wago (758 IPC) or Beckhoff (CX series) with integrated IO. Create your program with the code generator from www.icd.no or CoDeSys from Wago. In a modern PAC the processing capacity is never a problem!

A typical 600 MHz controller costs about USD 2000 (plus IO)

Bjørnar

 

You are talking about something that is well within the capabilities of virtually any PLC currently being sold. My guess is a decision on what controller to choose is going to be based on other factors like price, communications requirements, and familiarity.

 

please what is diff. between shedding and sharing load ?

 

Load sharing is distributing the electrical load between multiple generators.

Load shedding is where you selectively remove electrical load from your distribution network to prevent a generator overload.

 

For given I/O count will it give scan time of less than 100 Msec???

 

Most PLC manufacturers will give you specifications for scan rate. It will depend on a number of factors, including the size of the program, the number of I/O installed, I/O and communications configuration, etc. Pick out a PLC that you think you will like, and go through the documentation. If the specs aren't in the manuals, contact the dealer and get him to dig them up for you.

I can't think of any PLCs that wouldn't meet that spec in terms of basic scan rate provided everything is in the local rack and your program isn't too unusual. However, you have a lot of analogue inputs, so the question will be whether the resulting I/O would overflow the local rack and need a rack connector, which in turn may have an asynchronous scan.

You're going to have to do the engineering work on this to get an answer. You need some PLC manuals, a notepad, a calculator, and a bit of patience to get this answer.