# Presentation: 143751

## SWAT Short Circuit Study Group Update

- May 10, 2006
- Albuquerque, New Mexico

**Notes:**
This is the first update of the SWAT SCWG since they started work in January of 2006.

## Short Circuit – System Reliability

- Relay Misoperations – Fail to Operate or Operate When They Shouldn’t
- Equipment Damage due to Failure to Operate Relays
- Circuit Breakers and Other Equipment Failure because not Properly Rated

**Notes:**
System Reliability is the operational reliability of the system.
The operational reliability depends on relays to properly sectionalize the system during a disturbance and for the equipment to be able to handle the available short circuit current.
The settings of the relays and the ratings of the equipment depend on the correct fault current values in the Short Circuit case.
If the short circuit case is not coordinated with all of the utilities, the fault current values will not be accurate and the relays may be improperly set.
If the relays are not properly set, they may cause an outage when there is not a need to do so.
If the relays are not properly set, they may fail to operate during a disturbance and cause loss of a larger part of the system or even equipment damage.
If the short circuit case is not coordinated with all of the utilities, the fault current used for equipment ratings could be below what is available and cause further outages in a disturbance due to equipment damage which could also cause a larger part of the system to be outaged.
The Short Circuit Working Group is a Reliability Function which should be considered by WECC.
Since WECC has a void in operational reliability by not coordinating the short circuit case like they do the loadflow cases, the regional planning groups are setting up their own short circuit working groups. 

## SWAT Short Circuit Working Group (SCWG) Accomplishments

- Webpage setup and linked to SWAT Website
- Charter (Scope) Finalized
- All SWAT Transmission Owners joined
- 4 meetings held since starting in January
- Monthly meeting schedule
- Impedance Map Plan Developed
- Working on Combining First Case

**Notes:**
The Short Circuit working group setup a webpage that is linked to the main SWAT webpage.
This webpage contains all of the work done by the working group and is updated after each monthly meeting.
The Charter for the working group was finalized at the first meeting in January.
All of the transmission owners in SWAT are now members of the SWAT SCWG.
The SCWG has held 4 meetings since January. The meetings are scheduled for  the 3rd Thursday of each month.
The meeting schedule is a rotating schedule at the different members facilities.
The Impedance Map plan was completed at the 3rd meeting in March.
The group started working on the combined case at the 4th meeting in April.

## SWAT SCWG Webpage

**Notes:**
You can click on a link from the main SWAT Webpage  to go to the SCWG webpage.

## SWAT SCWG Webpage

**Notes:**
This is how the webpage appears.

I will cover the items on the webpage as I go through the presentation.

The items which can be clicked on in the lower left side of this view will bring you to the different sections.

The Charter link is shown here at the bottom in blue.

## 4 Main Areas of Work

- Impedance Maps
- Annual Operating Case
- Common Study Methodologies
- Annual Standards Review

**Notes:**
There are 4 main parts to the work that the short circuit working group will perform.

These four parts are the impedance maps, the annual operating case, common study methodologies for jointly owned stations, and an annual standards review for the standards related to the common methodologies.

## SWAT SCWG Charter

**Notes:**
This is the charter that was finalized by the group.

This is very similar to the draft charter presented to SWAT last year.

There are copies of this being passed around right now.

## SWAT SCWG Webpage

**Notes:**
The minutes of each meeting, the agenda of the meeting, the attendance list, and the presentation material are put in pdf format and loaded on the website after each meeting.

Since these are lengthy documents with a lot of technical details, I will leave it up to anyone interested in the details of the work to download the notes and go through them at your own liesure.

The documents for common methodologies and standards review will be developed later and placed on the website.

## Meeting Locations

- January 26, 2006 – WAPA - Phoenix
- February 16, 2006 – TEP/UES – Tucson
- March 16, 2006 – NPC/SPPC – Las Vegas
- April 20, 2006 – SRP – Phoenix
- May 18, 2006 – SWRTA – Casa Grande

**Notes:**
This shows the meeting schedule and locations.

The June meeting may be here in New Mexico. This will be decided at the May meeting.

## SWAT SCWG Webpage

**Notes:**
Each member submitted their current impedance maps. 
A list of the items that the group wanted on the combined set of impedance maps is in the top link. 

All of the maps are encrypted with a password. The primary contact for each member has the password. Please ask the contact at your company for the password if you need it.

If other planning study groups, such as DPV2, are formed in the future and require a short circuit working group, the SWAT SCWG will form a task force to represent SWAT. 

The information from this task force will be posted here when such a task force is formed in the future.

## Impedance Maps Work

- Most Impedance Maps Are Out of Date
- List of Items to be Placed On Maps Developed
- A Single Set of Impedance Maps to be Generated
- Requested SWAT to Develop WestConnect  Funding of Impedance Map Generation
- Only 2 WestConnect Members not Members of SWAT SCWG

**Notes:**
The group found that many of the members impedance maps have not been updated for several years.
Each member made maps differently.
The group developed a common set of items that everyone agreed to for a common set of impedance maps.
This will relieve each utility from having to update individual maps which had a lot of information about other members annually.
After the list was developed, the group contacted SWAT and requested that SWAT work with WestConnect to pursue funding of the development of a common set of impedance maps by WestConnect.
The WestConnect method of funding was pursued because there are only 2 members of WestConnect that are not SWAT SCWG members and each member stated that they do not have the resources to generate a common set of impedance maps.
The 2 WestConnect members that are not SWAT SCWG members did not want to participate because they did not want to duplicate the work they are doing in the CCPG SCWG.

## SWAT Letter – 3/24/06

**Notes:**
This is the request for WestConnect funding  that was sent to SWAT by the group.

I am passing around a copy of this now for you to view the details and comment.

## SWAT Response – 4/16/06

**Notes:**
The response from SWAT reported to the working group at the April meeting was positive as shown here.

## SWAT SCWG Webpage

**Notes:**
The primary contacts of the working group are shown on the SCWG webpage. 
These are the contacts for your companies that are responsible for distribution/security of the password.

You will notice that the CCPG SCWG has formed a liaison with the SWAT SCWG.

It is hoped that other regional planning groups that form a SCWG will also form a liaison with the SWAT SCWG.

The benefit of a liaison is in combining cases to eliminate equivalents at the boundaries which will result in more accurate fault current calculations.

This is the void that is currently in WECC. As stated earlier, this void needs to be filled to increase our reliability.

## SWAT SCWG Participants

**Notes:**
This is a spreadsheet showing the participants by each SWAT SCWG member.
Each person listed has participated in at least one meeting.

## STEP SCWG Proposal

**Notes:**
STEP is considering forming a short circuit working group.
This is the first slide of a presentation given to STEP last week.
Again, it is hoped that they will form a liaison and be listed along with CCPG for improving the accuracy of our case and their case.

##  Member Programs

- APS - Cape
- SRP – Aspen
- WAPA – PTI and Aspen
- TEP/Unisource – Aspen
- SWTC – Aspen
- IID – Aspen
- EPE – Aspen
- PNM – Aspen
- NPC/SPPC – Aspen

**Notes:**
This is a list showing which short circuit programs the different members use.
Because there are different programs, the combined case developed has to be able to be converted in a way that gives the same results to each member.

## SWAT SCWG Webpage

**Notes:**
The group is currently working on developing a combined case.
They are currently investigating the conversion between different programs. 

The main programs used by the members are Aspen and Cape. 
Outside groups, such as the DPV2 SCWG, use PSS/E.
Therefore, the conversions of cases between PSS/E, Aspen, and Cape have to be checked before continuing work.

There is a complete fault level comparison of the differences between the DPV2 PSS/E case and the converted Aspen case in the second link shown.

## DPV2 SCWG Findings

- 442 of 1481 buses with 10 A or higher difference
- Some Transformers not Modeled as Transformers in the DPV2 SCWG PSS/E case
- Type 2 Buses in PSS/E Do Not Stay Constant

**Notes:**
The group found that the PTI case had many buses which gave differences in fault current from that of Aspen when the PTI case was converted.

The group is currently narrowing down all of the differences and will then request that the vendors fix differences that are required and the group will understand what needs to be changed manually after a conversion.

## DPV2 PSS/E Converted Aspen Worst Differences

**Notes:**
This shows some of the major differences. 
As you can see, these could lead to the difference between buying a breaker and not buying a breaker depending on what the margin is at a particular location.

## Combined Case

- Plan Developed
- Conversions Currently being Checked
- Zones for Members being Developed
- Equivalents to be Checked
- Cases to be Combined

**Notes:**
The group developed a plan at the April meeting on how to combine the cases. 

The combination will require 7 of the 9 members to combine 2 cases to develop the final case.

The group will check the equivalents in each program after the conversions are checked.

The group is currently determining which zones they want to use to represent their information in the combined case.

The cases will be combined after the conversions and equivalents are finalized and the zones are input by each member in their case.

## Future Work

- Combine CCPG SCWG Case
- Combine STEP SCWG Case (if developed)
- Develop Common Methodologies
- Review of Standards
- Start on next Annual Case and Impedance Maps Update (refinements)

**Notes:**
After the group has a combined case, they will combine their case with the CCPG case.
If STEP develops a case, the group will combine their case with the STEP case.
After the case is developed, the common methodologies will be developed.
After the common methodologies are developed, a review of the standards used by the common methodologies will be performed.
After this, the next annual case and impedance map updates will be developed. These will include refinements to the current case and maps.

## Future Refinements

- Add Mutual Coupling
- Add Line Charging Capacitance
- Add Motors
- Check Transformer, Line, Shunt, Generator, and Load Data

**Notes:**
Some of the refinements for a future case will be to add the mutual coupling between lines, to add line charging capacitance, to add more motor data, and to check the transformers, generators, lines, shunts, and loads in their current case.

This will be an ongoing process by each member based on the time they have to check all of their data.

## Refinement Example: Line Charging Capacitance

**Notes:**
As an example of the improvement from the refinements in the data, a comparison was run between the current case and cases with line charging capacitance added 1 bus out from a few stations.
As you can see, some fault current levels dropped by over 2.5%.

When all of the line charging capacitance values are added, the levels will drop even lower.

Only positive sequence capacitance was used for both positive and zero sequence in this comparison. However, positive and zero sequence line charging capacitance will be added in the refinement.

## Potential Load Flow Help

- Impedance Maps for Load Flow Operating Case
- Possible WECC Evolution of Regional SCWGs
- If WECC Bus Numbers Used Later, Import of More Accurate SC Case Data into Load Flow Cases

**Notes:**
There are other advantages to the SCWG work that could be realized by the planning groups of each member.

The impedance maps are currently used by some planning groups. When they are combined and updated, this will be a better tool for  the planning groups to visually see and check data in cases as well as to make changes.

The future plan is for the group to evolve into a WECC group. This means the case may, someday, be included in a WECC loadflow case since they both need the same data.

Some members have stated that the short circuit case usually has more accurate data because it is based on as built data whereas the planning cases usually have a lot of conceptual estimates that never get changed to as built data.
If the same bus numbers are used at some point in time, the data could be imported into the planning cases to improve the accuracy of the data in the plannning cases and the results of the planning studies.