1. Removal of Fraser RAS from RAS Databse
August 1st, 2017

2. Fraser RAS Purpose
The Fraser RAS mitigates overloads of the Fraser 138/115 kV transformer by opening the transformer low-side circuit breaker, CB-162.
Overloads are caused by various N-1 and N-1-1 outage combinations, but usually involve the loss of the Gore Pass – Blue River 230 kV line.
Outages causes an increase in thru-flows in the underlying 138 kV and 115 kV systems

3. Fraser RAS Background
Looped 115 kV
230 kV Transmission Path

4. Fraser RAS Background

5. Fraser RAS Implementation
Primary Protection is accomplished via inputs from the transformer bushing CT’s to a SEL-551 Overcurrent Relay
Back-up Protection is accomplished via inputs from breaker bushing CT’s to a SEL-387 Differential Relay
Both Primary and Back-up open CB-162 after 60 seconds of sustained loading above 125 MVA 30-Min Emergency Limit.

6. Fraser RAS Implementation

7. Fraser RAS Implementation

8. Fraser RAS Removal
Based on the implementation of the Fraser RAS, Tri-States finds that the Fraser RAS no longer meets the NERC RAS definition:
E. Schemes applied on an Element for non-Fault conditions, such as, but not limited to, generator loss-of-field, transformer top-oil temperature, overvoltage, or overload to protect the Element against damage by removing it from service.

9. Fraser RAS Removal
Tri-State does not intend to disable this protection scheme, but is requesting that the Fraser RAS be removed from the WECC RAS Database.