20180208PAC to Staff Dave Johnston Assessment.docx

PacifiCorp Main Grid Planning
PRC-(012 through 014)-WECC-CRT2
Attachment B RAS Assessment
RAS Name
Dave Johnston 230/115kV Transformer Trip
Reporting Party
PacifiCorp
Group Conducting Assessment
PacifiCorp Main Grid Planning
Assessment Date
12/31/2014
Review the scheme purpose and impact to ensure proper classification, is it (still) necessary, does it serve the intended purposes, and does it continue to meet current performance requirements.
SchemeDave Johnston 230/115kV Transformer TripScheme is designed to prevent overloads on the 115 kV system between Dave Johnston and Casper substations following theloss of both Dave Johnston to Casper 230 kV lines.
The scheme is manually armed via a selector switch in the Dave Johnston switching yard. For a prior outage of the Dave Johnston to Casper 230 kV line, the scheme is designed to trip for loss of either the Windstar to Latigo230 kV line or the Latigo to Casper 230 kV line. For a prior outage of either the Windstar to Latigo230 kV line or the Latigo to Casper 230 kV line, the scheme is armed to trip for loss of the Dave Johnston to Casper 230 kV line. For system normal the scheme is armed to trip for loss of both the Dave Johnston to Casper 230 kV line and either the Windstar to Latigo230 kV line or the Latigo to Casper 230 kV line.
The Dave Johnston 230/115 kV Transformer TripSchemeis classified as a Local Area Protection Scheme (LAPS). This designation is appropriate, as there are no system impacts for inadvertent operation of the scheme. Impacts of a failure of the scheme to operate are limited to thermal overloads on the local 115kV system.
The study results indicate that the Dave Johnston 230/115 kV Transformer TripScheme is still necessary to mitigate thermal overloads on the 115 kV transmission system near Dave Johnston substation. The scheme is effective, and no performance violations are seen.
Study Years
2014
System Conditions
Any load conditions (heavy, normal, and light)
Contingencies analyzed
(select what applies)
N-1
N-1-1
N-2
Extreme
N-2, N-1-1
Date when the technical studies were completed
2014
Does the RAS comply with NERC standards and WECC Criteria?
Yes
Discuss any coordination problems found between this RAS and other protection and control systems during this (most recent) assessment.
None
Provide a Corrective Action Plan if this RAS was found to be non-compliant or had coordination problems during this (most recent) assessment (should be NA for owner’s initial assessment).
N/A
Additional Notes
N/A