TEP’S RAS MODELING PRESENTATION
So we all know TEP likes to be different, so naturally our RAS scheme is different as well. We use a load shed scheme like some of the rest of you, but the operation of it is unique. The reason for the method is due to the fact that the TEP load pocket is served by remote generation that is located anywhere from 240 to 450 miles away. This makes the TEP system subject to voltage instabilities.
The LAPS we use is called tie open load shed or TOLS. TOLS utilizes a set of fast switched reactive devices and direct load tripping to protect the system. I’m only going to speak about the creation of the load tripping portion of this today. The reality way it works is planners determine the amount of load that needs to be armed in EMS for a predetermined set of contingencies. This is done utilizing a set of epcls created by TEP for PSLF. We have a contingency list that has the tols activating contingencies identified. So when our contingency processor is evaluating it looks at category first, then if it’s a tols activating contingency, then it looks to see if the case solves following the contingency or if there are thermal overloads. Now the set up I’m discussing is based on the previous TPL 1 through 4 standards. TPL 1-4 has changed things some, but the process will be similar. If the contingency is a cat c or d and is tols activating and the case doesn’t solve or there is a thermal overload the contingency processor will scale a set of loads by a block of 20 MW. this process is continued until the thermal overload is alleviated or if it was a case solving issue until the case solves and then it evaluates for overloads.
So to model this in Powerworld took some discussion but finally a method was determined through the help of the Powerworld personnel and those who attended the RAS modeling workshop. To start with an Injection Group was created. The reason for this is to place the scalable loadshed loads in a group together so they can be scaled. This is done by going to Explorer, Aggregations, and Injection Groups. Right click, then click on Advance filters, right click – insert, right click again – insert, select a category, select an element and add the element.
Once that is done then you move on to your Model Conditions. This one was a little more difficult. At the workshop I started with inserting each of our lines. This wasn't correct and upon discussion with Powerworld, I discovered I could insert Areas. So while this demonstration uses the preset up lines when we actually finish modeling this we will be looking at all the elements in the Areas surrounding and connecting to TEP. Model Conditions are set up similarly to Injection Groups. Go to Explore, Case Information and Auxiliary, Right Click - insert, set the filter for this one it was branch, then company, this will change to area at a later date, then set the conditions and name it. The abbreviations you see here are the line abbreviations.
At this time you define which of the conditions you just created cause the scheme to activate, this is the Model Filters. For what is demonstrated the overload of any of the lines will cause loadshed to occur. This is done by going to Explorer, Case Information and Auxiliary, Model Filters, Right click, Insert, choose conditions and name it. You'll see we named ours TOLS.
Now the contingencies in which this loadshed scheme is to occur is created. Go to Run Mode, Tools, Contingency Analysis, Right click, insert add new element, save and name it. I only did one contingency, but it is one I knew would cause an overload thus activating our RAS.
Once you have created the contingencies you click start run and it will do its thing and spit out results. You look at your results, see if it's what was expected and then go from there. So I know that was quick and brief. Are there any questions?