SCADA system 1

[bdn2004]

I'm working at an old plant that is considering putting in a SCADA system. It will display real time operations of the power system as well as record events. Also with proper permission will allow some remote control.

The consulting firm is recommending capturing data from as many around 5000 points of all different types of signals ie. analog, digital and temperatures. Needless to say it is very expensive.

The system they recommend incorporates annunciators and PLCs, RTUs, fiber networks, etc. With as much data that is being monitored I just wonder when a DCS becomes a better option. Or if all this stuff is really necessary.

Can anyone offer thoughts on their experience with SCADA or direct me to some webpage to help me ask intelligent questions? Thanks.

 

[zaza123]

There is a difference between Scada & DCS.Both are very expensive. DCS is normally used for control rooms where operation group operates the plant through that. The SCADA is basically for the Electrical Group.SCADA is used for control & monitoring If you only want to record events you can also go for SER(Sequence Event recorders) their prime function is to provide the sequence of eevents, which is required for the critical troubleshooting.
The system you want to opt depends on your need.

 

[itsmoked]

You should probably have a consulting firm or engineer who, would not benefit monetarily from the installation, do an analysis of the points that need to be monitored.

Most plants would not benefit from that many points. That much data can become a horrible mountain of cr@p to save, cart around, and to search thru.

Some one should look very carefully at what really would be useful to monitor.


BTW What kind of plant is this?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Eleceng01]

Do you have microprocessor based relays on the system already? What type of plant? What are you really wanting to do with the information? Both of the previous posts are right, many more questions need to be answered but it is hard to say if 5000 points is excessive without more information.

 

[waross]

While you were trying to decide whether to go with a Cadillac system or a Volkswagen system, your consultants may have proposes the Lear Jet solution.
How many instrumentation loops does your plant use now?
How does the cost/benefit analysis look?

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

 

[bdn2004]

This is a metals plant. There are many lines that have the same functions and the same inputs and that is why the large number of I/O. This is not a fully automatic/batch operation.

If we estimate by how many I/O points are proposed and assume that cost is accurate, the cost-benefit analysis would conclude that the project is worth it if we have more like 500 points, or 1/10 of the amount proposed.

One of the issues they are trying to solve is to quickly pinpoint a problem anywhere in the system and to show it graphically on the screens in the control room. A line going down is major money, and time is critical. This project is approved for the incoming power system but is obviously bleeding into the production equipment...

I'm still gathering info, but thanks for the help.

 

[jraef]

The way I would look at it, a DCS would be used where you are making a product that involves complex reactions and monitoring of high volumes of analog data and using it in large numbers of PID control loops. PLCs (as a part of a SCADA system) are not particularly good at that when the numbers of loops range into the hundreds or thousands, as they would in a chemical plant for example.

But if you are in a power facility, you are not using your analog data for a large number of control loops, you essentially have very few analog outputs, even if you have a lot of inputs. So as a monitoring system, a SCADA package is a better way to go. Individual sub-processes can be controlled by PLCs, i.e. cooling water feed pumps, air monitor fans, coal conveyors, breaker closing schemes etc. Then the SCADA software package can simply monitor all those existing control points for data along with stand-alone power transducers if you are planning on including that into your data reporting.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[slavag]

Hi bdn2004.
zaza123 was a very correct in definitions what is a SCADA or DCS.
Please provide a more data, and we can recommend something.
Eleceng01 was asked :
Do you have microprocessor based relays on the system already?
This is a very important point. Please answer.

Best Regards.
Slava

 

[bdn2004]

Slava,

The protective relays are not microprocessor based. We want to display on a monitor in the control room the the existing status of the power plant, that is amps, volts, power, etc, for each of the major lines. We also want to know the contact positions of power circuit breakers, some air break switches, and temperatures and pressures on the main transformers.

Should the state of a relay or switch change, that information will record on a sequence of events recorder.

Also, we want this information to be available over the Internet so that the power systems engineers can monitor the system from anywhere.

 

[racobb]

If the relays are not some type of IED comm capable, then you will need to add tranducers to get the data....maybe given the cost of those, it might be time to upgrade the relays. At least something to consider.

For remote access, if the SCADA system uses PC's as operator workstatiions with internet access, I would suggest gotomypc and an option. Cheap, Secure, and works great. I use it on about 10 systems in the US.

You do not need special software on your PC to get to the system, so it will grant access from any PC on the net, given you have the proper passwords.

Alan

 

[slavag]

OK.
bdn2004, more or less situation is clear.
Its SCADA. Im not sure if you need dedicated SER, you need RTUs with 1ms resolution and I think it will be good for you, power meters with communication, simple to outgoing feeders and with DR. THD, etc.. capability to infeeds.

Internet, isn't issue, you connect remote station to your local serever via firewall, not someting special.

If you don't need 1ms resolution for event recorder and enough for you only status and analogue data, you can build a cheap SCADA with Modbus, but w/o time tags.

Godd Luck.
Slava

For the option of RTU ( a high level products):
ABB-RTU560
Siemens - TM1703

 

[Peer95]

This maybe can help you when you decide, This 7 questions can be for any vendor.

http://www.automation.siemens.com/w2/efiles/pcs7/support/marktstudien/PAWP00015.pdf

Best Regards
Peer95