Connection Impact Assessment

[ConEng11]

Hi Guys,

This is my first time here. I recently got laid off and am looking for a possible opportunity with utility. I came across an opportunity that deals with connection impact assessment when an independent power producer(Hydro) wants to connect to a utility.
I was wondering, People here who work for utilities might be able to advise me the steps for analysis a utility takes or the procedure it follows for assessing a connection in terms of fault level, protection and stability. How utility makes sure that this connection is good to go. There are lot of documents available on web but none of them talks about what utility does. Most of them talk about what a utility expects like anti-islanding protection etc.

I would appreciate a word.

Thanks

 

[marks1080]

Are you sure you don't mean Customer Impact Assessment? I did that work for a few months during a university work term. It was interesting work. The utility will often do the Customer Impact Assessment (CIA) and then the System Impact Assessment would be done by either the utility or an authority (market operator for example).

The good news for you is that there is a lot of work in the industry dealing with this, so jobs are out there.

The typical CIA would use a program like PSS/E for example to determine voltage limits and short circuit currents for different contingencies and then determine the effect that the extra generation would have on customers already connected to the grid. The SIA is similar but more involved and would look at the effect of the extra generation on the power systems stability etc...

At the end of the day all you are looking at from the CIAs point of view in determining a new generator is ok to connect to specific circuit are voltage levels and short circuit currents within a determined 'region' of the power system for atleast two contingencies. If the numbers are within acceptable limits the generator can move on to the next stage of the process.

 

[redfurry]

Here in Ontario, Canada it is indeed called a Connection Impact Assessment when considering the addition of distributed generation.

Typical things to consider include:
- effects of generation on system voltages. This includes both effects on steady state voltage at max and min system loading levels, as well as the momentary change in voltage that would be experienced as the generator connects/drops off (especially important for wind)
- effects on fault levels due to generator and resulting effects on equipment withstand levels and protection function

May also want to consider:
- effect on feeder losses (can increase for large generation projects at end of feeder)
- effects of transformer inrush (some solar projects disconnect their transformers every day to reduce no-load losses)
- presence/absence of anti-islanding, transfer-trip, etc.

 

[ConEng11]

Appreciate the comment Mark. This is what I exactly need.

I know a little bit of PSS/E but I might end up using CYME-DIST. Well may be I should rephrase; I will use it if and only if I get the job What exactly I am looking is that what procedure is followed. Is there a document that might possibly give me an insight in to this process.

Thanks

 

[marks1080]

I am also in Ontario redfurry. It's a common mistake for the CIA to be called a Connection Impact Assessment. It is a Customer Impact Assessment. In Ontario HydroOne would complete the Customer Impact Assessment and the IESO would complete the System Impact Assessment.

 

[marks1080]

The procedure is not that complicated. First you pick your 'zone' of interest. I was involved with Tx studies (as opposed to Dx), so if Generator X wanted to connect to circuit Y you would define your study area - usually no more than 2 stations away from the circuit Y terminals, although that is only a rule of thumb. Next you find the limitations of all the elements within your study area. You are looking for short circuit ratings of breakers, overload limits on lines, etc... Then the fun begins. You run studies (i used PSS/E). You take your system base case with the added proposed new generation and run every contingecy and double contingency you can within your study area. This involved taking out lines, or transformers. Depending on the study area you will get mountians of information from this. Now the not so fun part... You need to go through all the numbers generated by PSS/E which include voltages - transient and stead state, SC currents, etc... The voltages are allowed to varry by a certian % for each contingency and obviously you must remain below your SC ratings for each peice of equipment.

That is a quick summary, every situation is obviously unique in some way and special considerations may have to be given.

I would post some of the CIAs that I completed for you but they are technically confidential.

 

[ConEng11]

Thank you.

 

[redfurry]

Not to be too pedantic, but the proper term really is Connection Impact Assessment (see the following Hydro One page)

http://www.hydroonenetworks.com/en/...neration_connections/distribution/default.asp

This is what is required for a generator between 10kW and 10MW connecting to an LDC in Ontario. The LDC or a designated consultant will be responsible for the study. The generation owner just has to pay for it.

 

[marks1080]

Yes redfurry you are correct. I think I was confused as I worked on the transmission side of things.

For smaller gen sets the studies are not as in depth and the general study is called a Connection Impact Assessment. The IESO does not get involved with these.

For larger gen sets (>10MW) there is a Customer Impact Assessment and a separate System Impact Assessment.

I think rigth now the Connection Impact Assessment would be more common.

 

[Ishrit]

Hi Mark,
Some how my earlier log-in got blocked or some thing. I was wondering about those studies if I could use as an example. I would appreciate if you could help.

Thanks

Redfurry,
I am in Ontario as well and was wondering if this kind of CIA studies give a good insight from learning perspective. I have never worked for a utility before. Will there be a lot of work of this nature for a while in the market ?

 

[redfurry]

Doing CIAs provides great experience if you want to get involved with utilities. You'll do fault studies, load flow studies and get familiar with typical equipment, load levels, etc.
As marks1080 noted, you will need some kind of analysis software to do this work properly. The most commonly used packages in Ontario are CymDist and DESS, although you could also use ETAP, EDSA, Synergy, Milsoft, etc.

There are a fair number of utilities who have neither the resources nor the expertise to do their own CIAs, and I don't see this changing anytime soon so the need for these type of studies will continue as long as the government (OEB) regulations encourage development of distributed generation. Also, many utilities which were initially resistant to having distributed generation attached to their feeders are becoming more comfortable with it and placing less obstacles in the way of applicants.
Right now, with wind paying $0.20/kWh and solar paying $0.40/kWh under the standard offer program, there's a pretty good incentive for generators.