RPEWG Report to PCC Seattle, WA June 2003

RPEWG June Agenda 1.SRP Double PV-WW PBRC Adjustment Seven Step Process 2.Phase 1 PBRC Adjustment Review: Robust Line Design

RPEWG June SRP Double PV-WW PBRC Adjustment Request Salt River Project requests a PBRC Adjustment from Category C to Category D for the double Palo Verde to Westwing line outage Evaluated using Seven Step Process

RPEWG June SRP Double PV-WW PBRC Adjustment WW Step 1: Provide Project Description Detailed report provided.

RPEWG June SRP Double PV-WW PBRC Adjustment PV-WW performance has been excellent No double outage One line 2 outages and second line 0 outage Sample developed from SGS data for SW EHV lines Very few SW EHV line on shared corridors Step 2: Identify the Statistical Base

RPEWG June SRP Double PV-WW PBRC Adjustment Sample from matching terrain, weather conditions and structure type 39 circuits MTBF N-2 Weibull method of analysis Coincident Independent events = 500 years N-2 Dependent event analysis = NA Step 3: Uncorrected MTBF

RPEWG June SRP Double PV-WW PBRC Adjustment #1. MTBF Analysis: Lines w/<1.5 outage/year except Mead-Phoenix included 17 corridors 2 instances of N-2 events N-2 Weibull MTBF Coincident Independent events = 2,824 years N-2 Dependent event analysis = NA Step 4: Corrected Estimate of MTBF 1. MTBF analysis ……….. 2. Robust Line Design Features

RPEWG June SRP Double PV-WW PBRC Adjustment #2. Robust Line Design Features: RPEWG used its Robust Line Design Features working paper to evaluate the robustness of the line design. The analysis compared thirteen factors in examining the line robust features. Two areas of concern were critically evaluated Mead Phoenix line crossing over PV-WW Circuit separation preventing towers falling into each other Step 4: continued

RPEWG June SRP Double PV-WW PBRC Adjustment The conclusion from the Robust Line Design Features evaluation was that the PV-WW lines meet or exceed the Robust Line Design Features required for PBRC adjustment. Step 4: continued

RPEWG June SRP Double PV-WW PBRC Adjustment 2% of time double PV-WW will be critical outage Existing safety net will remain in place during time when PV-WW double outage is the critical outage Step 5: Exposure Analysis

RPEWG June SRP Double PV-WW PBRC Adjustment Step 6: Consequences of Outage System safety net will remain in place Operating studies show that voltage dip with PV-WW outage will not exceed 30% voltage dip criterion

RPEWG June SRP Double PV-WW PBRC Adjustment RPEWG members voted to approve and recommend that PCC also approve SRPs request for PBRC Adjustment for the double PV-WW line outage from Category C to Category D. RPEWG cannot make a recommendation regarding MTBF of greater than 300 years. Step 7: Recommendation

RPEWG June SRP Double PV-WW PBRC Adjustment PCC discussion & vote

RPEWG June Phase 1 PBRC Adjustment Review: Robust Line Design

RPEWG June Risk Factors The following is a list of risk factors to be considered in ROW planning for cases where it is the goal that the N-2 outage be of very low probability. Generally risk increases with common ROW distance. R1 Risk of fire affecting both lines R2 Risk of one tower falling into another line R3 Risk of a conductor from one line being dragged into another line R4 Risk of lightning strikes tripping both lines R5 Risk of an aircraft flying into both lines R6 Risk of station related problems resulting in loss of two lines for a single event R7 Risk of snow or earth slides R8 Risk of loss of two lines due to an overhead crossing

RPEWG June Design Variables The following are design variables which affect the credibility of each of the above Risk Factors: V1 Substation breaker configuration (R6) V2 Circuit centerline spacing (R1,R2,R3,R8) V3 Span length (R3) V4 Tower design (R2,R7,R8) V5 Use of shield wires for lightning (R4) V6 Conductor support systems (R8) V7 Use of dead-end versus suspension towers (R3) V8 Use of single pole reclosing (R4) V9 Vegetation management (R1) V10 Fire watch curtailments (R1) V11 Shortening of line on common ROW (R1-R8) V12 Tower grounding (R4) V13 Protective relaying design and settings (R6)