Capacitor Switching Transients Calculation

[LaliGuras]

I am plannig to install a capacitor Bank at 69/12.47 kV substation. The bank is 2700 kVAR three stage bank with 900 kVAR in each stages. I am wondering how you estimate the voltage transients due to 900 kVAR capacitor switching?

Substation transformer: 14/20 MVA, Impedance, 9%
Source Impedance (Ohms):

R X
+veSeq, 0.85 6.5
-ve seq, 0.85 6.5
0 Seq, 1.92 11.31

Thanks.

 

[ePOWEReng]

I would recommend doing an ATP study of the switching transients. There are a number of things that should be looked at: voltage transient on capacitor bank close, possible voltage magnification looking down the feeders and back-to-back switching transients. ATP is a free program.

Assuming that your system is Y-grounded, the worst case votlage transient is 2PU. Adding damping into the circuit will determine how fast the transient decays which means the voltage won't reach 2PU.

 

[davidbeach]

ATP is a free program.

True enough, but simply gaining access to the program will hardly get one started.

Preinsertion resistors can drastically reduce the capacitor switching transients.

 

[ePOWEReng]

ATP is not difficult to learn with the windows based GUI. If one doesn't have time to learn and apply a transient analysis program then one should hire a consultant.

 

[smur]

I have always wanted to learn ATP. i have dreams of doing a transformer inrush study, stabilty studies, motor starting study, voltage collapse study etc. it will be pure fun to watch these things. But I hear that learning EMTP or ATP can be quite a task ? or I am imagining this? If you folks know how to do this, PL give me some examples or hints to get started. thanks
murli

 

[davidbeach]

I learned a bit of ATP in a semester "Electrical Transients" class through the University of Idaho's engineering outreach program. That was mostly just scratching the surface though. I've since learn a bit about using TACS (control modeling within ATP) and have built some relay models. There is still much to learn.

To perform a transformer inrush study you would need the data from a B-H curve for the transformer. ATP is probably not the tool for stability studies, one second is a very long time for an ATP study as the time step will usually need to be 100[μ]s or less.

 

[smur]

Pl give some sites where they give instructions for TACS. This outreach program, Is it available as a distance education? Pl pass on some information to help tutor myself
thanks

 

[davidbeach]

http://www.outreach.uidaho.edu/eo/

 

[mc5w]

How can I download this nifty program? might ber something that I could learn while business is slow.

But, I would not be too terribly interested in going to the University of Idaho. The electrical contractor licensing law there says that I have to prove that I am RICH in order to get a license and by that time I would be making enough money that I would not need to go there.

Virginia, for instance, says that I must have at least $15,000 in net positive assets to get an electrical license to do an electrical project that is worth more than $1,000. They do not want poor people to come in from the Rust Belt and take theri jobs. This is no different than how they one time had a law that said that Catholics could not own land because of how much money Spain and Italy were sending to Vatican Hill.

There are some cities such as Warrensville Heights, Ohio that demand that electricians pay them $150 per year for registration. We do not have quite full blown state licensing in Ohio because itty bitty alleged cities are still allowed to demand tribute from us unlike Massachusetts. Need another year of experience maybe even 6 to get a license in Massachusetts.

Yes, electrical engineering is a political science and politics is a mental illness that revolves around money.

Mike Cole

 

[hvcad]

I'd recommend PSCAD-EMTDC for this type of calculation.

http://www.pscad.com

Dr K S Smith
Mott-MacDonald, Power Systems Division
Glasgow, Scotland.

 

[smur]

Is PSCAD the same as EMTP or atp ? How much does this cost?
thanks

 

[davidbeach]

PSCAD is the front end for EMTDC. There is a limited capability student edition available for free, otherwise it is very expensive. ATP is free, with registration and a license, from

http://www.atp.org.

Despite one smart aleck response, nothing was said about needing to go to Idaho to take advantage of U of I's engineering outreach program. It is a complete distance learning program means of earning a masters degree without the need to go there to attend classes. They also have a certificate program in Power System Protection.