Southwest Rhode Island Transmission Supply Study Long Term Needs and Solutions

Southwest RI Transmission Supply Study Study initiated in 2001 due to recognition of voltage and thermal concerns. Identified Short-term and Long-term upgrades to ensure reliability of service. SWRI area supplied primarily by 115 kV lines looped between Kent County in RI and Montville in CT.

Geographic Location of Southwest RI New England Power Company Map redacted due to Critical Energy Infrastructure Information Available upon request

Southwest RI Area Reliability Concerns Voltage Concerns – Loss of G-185S – Voltages drop to unacceptable values of less than 0.9 p.u. and potential collapse Thermal Concerns – Loss of 1280 – G-185S overloads over STE rating for loss of 1280.

Existing Concerns New England Power Company Map redacted due to Critical Energy Infrastructure Information Available upon request

Short-term Upgrades Short Term upgrades addressed immediate voltage concerns – 7 distribution station capacitors – total of 38.7 MVars – In service for Summer 2003 Other Actions – Planned G-185S Uprate for Summer 2005

Recommended Solution New England Power Company Map redacted due to Critical Energy Infrastructure Information Available upon request

West Kingston Substation

Recommended Solution Extend L-190 from Davisville Tap to West Kingston substation (2007) – Total of 12.3 miles ACSR – Install load break switch at Davisville Tap – Total $6.0M Connect L-190 at West Kingston substation (2007) – Install new 115 kV bus structure – Install 2 nd Breaker and two disconnect switches – Reterminate T2 transformer to L-190 for better load management – Replace existing breaker and disconnect switches at West Kingston substation – Install motor operated air break switch on L-190 within substation fence. – Replace air break switch on G-185S with a motor operated air break switch within substation fence – Total $2.6M

Recommended Solution (contd) Reconductor L-190 from Kent County to Davisville Tap (2007) – 2 miles of 795 AAC on single circuit towers reconductored to 1590 ACSR (2007) – 3.26 miles of 795 ACSR on DCT reconductored to 1113 ACSR (2007) – Total $1.9M Future Upgrade: Reconductor G-185S from Kent County to Davisville Tap by 2012 – 2 miles of 795 ACSR on single circuit towers reconductored to 1590 ACSR – 3.26 miles on DCT reconductored to 1113 ACSR – Total $2.0M Total $14.6M – TCA Application $10.5M – Short Term Completed Non-PTF $ 2.1M – Future Work $ 2.0M

Other Alternatives Studied Alternative 2 – 115 kV Capacitors (6x10 MVAr) – Reconductor G-185S from Davisville Tap to West Kingston to 795 ACSR (2006) – Reconductor G-185S from Kent County to Davisville Tap with 1113 ACSR and 1590 ACSR (2008) – Additional Reinforcement Reqd by 2016 – Estimated Total $15.7M Alternative 3 – FACTS Devices (60 MVAr) – Reconductor G-185S from Davisville Tap to West Kingston to 795 ACSR (2006) – Reconductor G-185S from Kent County to Davisville Tap with 1113 ACSR and 1590 ACSR (2008) – Additional Reinforcement Reqd by 2016 – Total $19.9M

Other Alternatives Studied (contd) Alternative 4 – 345 kV line Kent County to Montville – Total $108.1M

Assessment of Alternatives Recommended L190 Alternative : – Technically Superior to Alternatives 2 and 3 – Economically preferred – least cost – Future Expansion – in-line with long term plans to continue 2 nd 115 kV tie into Connecticut. – Potential operational impacts during construction – less impact than Alternatives 2 and 3. – West Kingston substation will contain new standard equipment for additional breaker and replacement of existing breaker and switches. Alternatives 2 and 3 – Switching voltage variations are an issue on weak system Alternative 4 – Cost excessive for local needs – Longer construction time

Upcoming Applications New England Power Company Map redacted due to Critical Energy Infrastructure Information Available upon request