Load Shedding & Mangement Specification 1

[Kiribanda]

Hello to all members,

Could any member, kindly furnish a good Specification for a Load Shedding & Load Management System suitable for a medium sized industrial plant having in-house power generation with a utility backup. ( A web site or some relevant IEEE papers are also welcome)

Thanks in advance!

Kiribanda

 

[advidana]

Try the transfer switch manufactures, the have a lot of information these issues and guide specs.

 

[mikhe]

SEG-AVK are very good at this, a search on the web will find them.

 

[dede61]

I believe that you'll find what you need concerning hardware at

http://www.vamp.fi

All protections, power monitoring all have very wide communication possibilities.

 

[GerH]

From our experience, first thing is that Load Shedding can mean different things. Are you trying to manage the load for commercial reasons, is it to avoid overload + blackout when islanded?

Next point is that Load Shedding as you go into Island is very tricky, with no time to evaluate. The strategy that works is to take a conservative small island load that will ensure load is within on-site generation and then slowly build back up to optimise on-site generation.

The Grid disconnect mechanism are important. We use df/dt and Vector shift. Underfrequency is fitted but it never comes into play. The faster you disconnect the better but I guess it also depends on the type of on-site generation.

PLC control is quite adequate for load management but the key is to avoid spurious breaker trips. E.G. require two outputs to activate to trip a breaker and monitor both for pre-activation. Put an external watchdog on each PLC.

Software structure that avoids errors is probably the last area. A step structure that activates bit-patterns of the breakers to be open/closed is what we use. Can you make changes on the run without mistakes.

I could go on...

 

[margaret695]

kiribanda: Like GerH mentioned, load shedding and load management can have lots of different meanings. Are you trying to keep down energy costs? Are you trying to avoid an overload during a black out? Are you trying to avoid an overload even when connected to the utility? Or are you trying to avoid having to upgrade the main electrical entrance from the utility and/or the size of the generator? In my opinion, you have to have your aims quite clearly defined before you get to the actual specification scheme.

Also you have to get accurate information from the plant operators and the mechanical engineers and/or process engineers (if applicable) on what specific equipment has to work in unison with other specific equipment.

You also have to clearly define what equipment and lighting, etc., has to remain operational during as per the applicable codes. Stuff like fire pumps, sump pumps, emergency lighting, fire alarm systems, security systems and often some ventilation equipment, etc.

And often the computer systems of an plant are required to remain operational... at least in part. Just what circuits are essential for a computer system, along with the associated cooling equipment, UPS equipment, etc., have to be worked out with the operators of the computer system.

Having accurate an up to date engineering drawings of an existing plant, or the finalized engineering drawing for a new facility, are also obviously required.

Also, in my opinion, you have to make some value judgements between the connected loads involved and the demand loads. Some stuff has a lot of diversity... and some has nada. Having an electrical contractor take a number of readings .... during the time when the loads should be at their peak... is a good idea.

Then the accounting types some times get involved, because often the cost implications of keeping a certain sector on, should be analysed. The basic notion being... how much money will be lost if this certain process, or whatever is not kept operational. And sometimes the time spent restarting equipment is implicated.

And if you aim is to save energy costs, often mechanical engineers can come up with some possible solutions, like changing older boilers with limited numbers of steps, to ones with lots of steps and possibly changing the types of starters for some motors installing a DDC system for HVAC equipment, etc.

If you concern is about connecting more load to an existing generator, finding out the number of "steps" for the existing loads and then adding some more steps. Meaning the sequence and timing of the starting of the loads when connected to the generator, so that the inrush on the generator is deminished, etc.

Most generator manufacturer give away programs that help engineers calculate the loading and the steps for their generators.... but you still have to make a lot of different judgements while inputting the data. If you are talking about an existing generator, then contact the manufacturer and ask if they have load calculation programs. If you are specifying a new generator, then doing the load calculation with several different programs is a good idea, in my opinion.

Concerning the specification of the load shedding... as avidana mentioned... the companies who sell transfer switches usually have standard specifications... and some times the controls associated with the generator can also do load shedding... so asking the generator manufacturer is also a good idea.

I also tend to use the Canadian Government's Master Specification for stuff that my office hasn't written a spec for..... and adjust it to suit the specific project. But then again... I am Canadian.

Also there are companies out there that specialize in manufacturing load shedding equipment for electrical loads. I have specified equipment by this company a number of times...

http://www.gentec.ca/en/a/a_index.html

but they are located in my area... in my opinion, it is usually better to go with a company that operates in the area where the plant is. Just check how long the manufacturer of loading shedding equipment has been in business and ask for a list of plants where their equipment has been installed. I tend to like to specify, companies that have been around for over 10 years and have long lists of places were their equipment has been installed.

And I went on and on, eh.

Margaret

 

[meggar]

An FKI company in the UK, Brush Electrical machines, manufacture a Power Management System called PRISMIC. This is widely used in the Petrochem and Oil and Gas inducsties.

 

[jbartos]

Suggestion: Visit

http://www.gepower.com/dhtml/energyconsulting/en_us/wizard/group_10.jsp

etc. for more info

 

[littlesparky]

Its off the subject, but what kind of in house generation do you use?

 

[EddyEE]

Specifications are normally based if not totally copied by consultants/designers (Upps.. sorry for my words.) from equipment manufacturers' catalogues and manuals. In practice, some are specifying to recommend (a specific product and earn extra bucks).

About load shedding and load management, why not take a look at

http://www.woodward.com

or contact any of its authorized independent service facilities. They also have a product (tutorial on CD-ROM) regarding this.

Regards.

(This is my personal view. I'm currently unemployed and not connected to any company stated above.)

 

[WattsNew]

Check this one out

http://www.etap.com/psms_ils.htm

 

[alehman]

choiEE: "Specifications are normally based if not totally copied by consultants/designers.."

I take excption to this comment. I think it gives us consultants a bad wrap. Yes it does happen, and sometimes that's what is really wanted by our clients. But this is not the proper way to write a specification and will inevitably lead to a product from the manufacturer who furnished the model spec or extensive exceptions or both. I think most engineers recognize this problem and will try very hard to it.