Electric Operations 2008 Capacity & Reliability Plan June 12, 2008

1. Att. DPU-2-1 Electric Operations2008 Capacity & Reliability PlanJune 12, 2008

2. NSTAR Team • Kerry Britland Government Affairs • Vera Admore Maintenance & Construction West • Rob Billet Substation Operations • Amin Jessa Distribution Engineering • Greg Sullivan System Planning • Steve Sullivan Maintenance & Construction Central • Leanne Landry Investment Planning

3. 2008 Electric OperationsSystem Investment Strategy • Capital System Improvements • Improve system reliability • Continued expansion & upgrade of distribution automation • Increase electric system capacity • System Maintenance • Physical inspections of plant • Methodical operation of devices to ensure operability • Planned maintenance of assets • Infra-red surveys of equipment • Repair and/or replacement as required • Network Feeder Response Procedure: Re-commence 6/15/08 • Network Protector Load Reporting: Re-commence 6/15/08 • Voltage Reduction Test: Performed 4/30/08 • Total 2.4% load reduction (0.7 AM testing, 1.7 PM testing) • Load Shed Procedure Review: Completed • Procedures and associated SCADA displays reviewed • May 9th, 337 line event, Real time review and preparation for load shedding was implemented • ISO/LCC joint operator training • Review emergency procedures OP-4, OP-7 & MLCC #2 • Summer shift starts June 15th

4. 2008 Distribution Work PlanCapital System Improvements • Approximately 207 Projects on 2008 Plan • 41% expected to be completed for summer • Approximately 61% of the plan is focused on reliability improvements and the remaining 39% investments are directed at capacity expansion • Capacity Projects Include: • Circuits/lines projected to be at or over normal/contingency ratings • Network System (Boston and Cambridge) • Feeders and transformers projected to be at or over normal/contingency ratings • Secondary grid upgrades to support transformation • Distribution projects in support of substation capacity projects • Project Work Includes: • Wire and cable upgrades • Replacement of switches and equipment • Distribution Automation to enhance switching capability • Reliability & Community Improvement Projects Include: • OH circuit rebuilds • New wire, equipment, and poles as required • Overhead Conversions • Converting older, 4 kV areas to 13.8 and/or 25 kV • UG DSS reconductoring • Replacing existing cable and splices with new equipment • 4kV UG conversion projects • Upgrading customers from 4 kV to open loop, 13.8 kV system of new cable, switches and transformers • Circuit Reliability Program • Includes tree trimming, new high voltage connectors, cut-outs, and other equipment

5. Distribution SystemInspections & Maintenance Program • Infra-Red Circuit Surveys • Network Manhole Inspections • Key Distribution Equipment Inspections • Capacitor Banks • Voltage Regulators • Scada-mate Switches • Pole-top Reclosers • Pad Mounted Switches • Sectionalizers • Radio-Controlled Equipment • Repairs Prioritized and Completed

6. Vegetation Management Program • Distribution System Tree Pruning & Removal Program • 1, 286 miles planned for 2008 • Engineering assessment of reliability data for priority circuits • 6Reliability Program Circuits identified for tree pruning and/or profiled tree removals. • Clearance standards and hazard tree removal program accepted in most communities • All circuits are audited for compliance to clearance specification • Communities creating standards or regulations that challenge a successful vegetation management reliability program • Acton, Boston, Brewster, Orleans, Sandwich, Waltham, Wayland, Winchester & Weston • Removals require additional rights and permission under state law MA Gen. Chapters 40,87 & 131 • Anticipated long term reliability impact from insects causing high tree mortality south of Boston. Most notable Freetown, Lakeville, Carver, Plympton, Kingston, Duxbury • Transmission Right-of-Way Vegetation Management • 140 Miles planned for 2008 • Working in cooperation with local conservation commissions and MassWildlife for mutual benefits of vegetation maintenance of ROW’s • Adherence to NERC requirements • Helicopter & ground patrols completed in North, scheduled for South in June ’08

7. Vegetation Management Program

8. Substation Capital Improvements - 2008 • Phase 2 of the 345kV Project • Mystic Station • 115kV breaker additions and replacements, (2) 115kv breakers complete, (4) remaining 115kv breakers due in the Fall. • New 345kV Reactor – Civil work to complete in 08, install reactor by Spring 09 • Canal Station • 345kV breaker upgrades • Carver Substation Upgrade • Civil work commenced in April. Major civil in new 345kv and 115kv yard during summer. First series of outages to commence in Fall for full station construction. • Brook Street Substation Upgrade • Complete station rebuild complete in April. Lines 116, 117, 132, 133 energized. Line 191 (Auburn St to Kingston) and new Line 194 (Brooks St. to Auburn St.) to be energized early June. - COMPLETE • Walpole Station Upgrade • All equipment installation scheduled to be complete in early June. Total of three (3) 62.5Mva transformer, new lineup of switchgear, overhead bus replacement, and two (2) 115kv breakers replaced. - COMPLETE

9. Substation Capital Improvements - 2008 • Station Transformer Capacity Upgrades • Station # 311, Mattapan • Station # 124, Watertown • Station # 976, Wellfleet • Station # 146, Walpole • Station # 292, Newton • Station # 617, Hathaway • Station # 933, Falmouth ( civil, w/ transformer in 2009) • Network Transformer Capacity Upgrades • Upgrade 9 Network Transformers in Boston & Cambridge • Emergency Stock Inventory • 10 Transformers rated from 6 through 300MVA and 4kV through 345kV • 12 Breakers rated from 4kV through 345kv

10. Substation System MaintenanceHow We Improve Reliability • Performed operational testing at all 80 NSTAR North 4kV substations • Trip tested and timed 644 4kV circuit breakers • Field operated every automatic bus throw over system & breaker reclosing relay • Repairing variances • Enhanced substation inspection program • Enhanced & directed inspections with follow up audits by Engineering & Ops • Variances prioritized and repairs tracked • Meetings with supervisors and employees to discuss quality of inspections • Enhanced circuit breaker PMs • Increased assessments to in determine future PMs • Trip testing relays and breakers • Survey & repair of @3,800 transformer fans and 245 transformer pumps • Network Monitoring is installed on all network equipment • Installing enhanced monitoring to improve reliability & increase productivity • Less return visits • Transformer Reconditioning & Repairs-caring for expensive assets • Reviewed condition assessment with Engineering & prioritizing repairs • Processed six transformers during the 1st half

11. NERC /NPCC Transmission Standards • 4 NERC standards relate specifically to Transmission System Planning • TPL-001-0 (facilities within ratings for Normal operating conditions) • TPL-002-0 (facilities within ratings for N-1 events) • TPL-003-0 (facilities within ratings for N-2 events) • TPL-004-0 (evaluation of extreme contingencies) • NSTAR Planning employs these standards in its transmission planning and coordinates with the ISO in regional planning • NPCC Audit of NSTAR in its capacity as a Transmission Planner determined that NSTAR was fully compliant with NERC Standards and Requirements

12. Transmission System Capital Improvements - 2008 • Brook St. & Auburn Street Transmission System Enhancements • Added New Structures & Reconfigured Line # 191 & 194 at New Brook Street Substation • Provides Greater Flexibility & Sectionalizing Capability • Utilized Internal NSTAR Crews for Transmission Line Construction • Installed OPGW (Fiber Optic Static Wire) on Line # 117 • Provides Control & Protection Communication Link for new Brook Street Substation • Enhances NSTAR’s Overall Telecommunication Capability in South Region • Capital Replacement of Transmission Cross-Arms • Line #: 447-508, 246-01, 240-510* & 391-508* • *Utilized Internal NSTAR Crews for Transmission Cross-Arm Replacement • Transmission Line Reliability – Line # 389 • Replace Transmission Structures • In Progress – Scheduled for Completion Prior to July 1st • Transmission Auto-Sectionalizing Switches • Initial (Pilot) Switch on Line # 108 Available For Use In 2008 • Improves Reliability by Isolating “Faulted” Portion of Line & Keeps “Un-Faulted” Portion In Service • Eight (8) Additional Switches On Order – Scheduled for Installation in the Fall of 2008 • Replacement of Five (5) Pipe Type Cable Pressure Maintenance Plants • Ensures Reliable Pressurization & Operation of UG Transmission System • Station 148-Needham = Complete • Station 250(A)-Mystic = Complete • Station 211-Woburn = July 08 • Station 385(A)-K-Street = October 08 • Station 71-Carver St = November 08

13. Transmission System Maintenance - 2008 • Helicopter Inspections • Comprehensive Semi-Annual Visual Inspection (Entire 700 miles) • Identifies Deteriorated Pole Tops, Cross-Arms & Insulators • Spring & Fall – Spring Inspections Complete – Corrective Repairs In Progress • Infra-Red Survey of System • Identifies Deteriorated Electrical Connections & Insulators • Spring & Summer – Spring Survey Complete – Corrective Repairs in Progress • Hi-Definition Digital Photography of Transmission Structures • Identifies Physical Deterioration Un-Detectable By Visual or IR Inspection • One-Third of System per Year – 2008 Program Scheduled for June • Right of Way Foot Patrols • Comprehensive Bi-Annual Inspection • Identifies Deterioration of Poles, Cross-Arms, Ground Wires & Braces • One-Half of System per Year – 2008 Program In Progress • Detailed Pole Groundline Inspections • Identifies Pole Decay At Ground Level & Treats with Insecticide • Performed on an 8 year cycle – 2008 Program In Progress (Cape District) • Vegetation Inspections– Tree Conflicts Observed During OH Transmission Inspection Programs are Referred to NSTAR’s Arborist for Corrective Action

14. Distribution Planning Criteria • Radial lines • All lines in • Typically no element loaded beyond normal rating • Voltages within +/- 5% of nominal (ANSI A range) • Loss of one element • Load is transferred manually or remotely to alternative circuits whenever practical to limit service interruptions • Remaining elements shall not exceed Long Term Emergency (LTE) rating • Voltages shall be within +/- 10% of nominal ( ANSI B range) • Secondary Network Lines • All lines in • Limit feeders, transformers and secondary mains to 100% of Normal rating • Loss of one element • Limit to 100% of emergency rating

15. Substation and Distribution Load Forecasting • Substation • Company peak load is econometrically modeled relating historic peaks to temperature-humidity index to produce a 90:10 forecast • While annual energy use incorporates economic, demographic and weather conditions, the peak is more focused on time and weather conditions at the peak. The Company peak forecast is developed by regressing historic data against time and Temp-humidity • Econometric models developed for each substation and its relationship to the Company peak is incorporated • Adjustments to specific substation peaks are made for known step loads- large projects • Distribution • Apply the rate of increase projected for the station to each circuit • Review that increase and identify known step loads and relate them to the appropriate circuit, adjusting the remaining circuits accordingly

16. Load Flow Analysis – Update • Distribution Load Flow • As identified by NSTAR in 2007 the Company is working to improve load flow diagram capability for the closed loop lines and secondary networks in the Northern portion of the system with a target to present a full analysis and results to eh Department in 2010. A spreadsheet method has been used for radial lines. A technical session has been requested with Department Staff to discuss this methodology • Modeling of the South using Cyme-Dist is nearly complete • Network Load Flow • The Secondary Networks System, is presently analyzed for each possible N-1 contingency event using an Excel database. Load flow model has been completed for Station 2 and model development on Station 12 has begun. • Real-time data is inputted using the following systems: • SCADA & PI (Plant Information Application) • Hazeltine (network transformer load and protector position) • NSTAR continues to evaluate its GIS data to link with CYME for computerized modeling of Networks

17. Mobile Generator Availability • NSTAR has a contract in place to obtain mobile generators • A representative list of the sizes available:

18. Additional Discussion Topics • Annual T & D Report Content • Open Questions & Discussion

19. Appendix

20. Budget and Project Planning Process • The Company’s project planning and approval process has several elements • Load Forecast developed in February- March • The Annual Operating Plan provided to the Department in May includes: • The most recent system and station load forecasts looking out ten years, and • Preliminary assessments of potential need for transmission looking ahead 10 or more years, for substations for 3 to 5 years and for distribution 1 to 2 years • The Capital project ranking project is then populated with projects based on the new load forecast over the Summer and focuses on Distribution over a 1 to 2 year span and other major projects through at least three years to be consistent with Capital budgeting • The Capital budget is prepared and approved in the late Fall for the next 1-2 years • Specific projects given broad approval in the budget are then engineered in detail and analyses and justifications are forwarded for corporate approval, individually • The following represents the specific projects and spending budgeted for 2008. This was produced by the 2007 budgeting process.

21. 2008 Distribution Projects Capital Spending Plan

22. 2008 Distribution Projects Capital Spending Plan

23. 2008 Distribution Projects Capital Spending Plan

24. 2008 Distribution Projects Capital Spending Plan

25. 2008 Distribution Projects Capital Spending Plan

26. 2008 Distribution Projects Capital Spending Plan

27. 2008 Distribution Projects Capital Spending Plan

28. 2008 Distribution Projects Capital Spending Plan

29. 2008 Distribution Projects Capital Spending Plan

30. 2008 Distribution Projects Capital Spending Plan

31. 2008 Distribution Projects Capital Spending Plan

32. High Profile Community Projects

33. ARLINGTON • Issues: Excellent performance over the past 18 months. Several complaints from the Board of Selectmen were received in mid-February in response to tree-related outages. Significant conversion and rebuild work will continue a multi-year project and improve system performance in Arlington. • Conversion/Rebuild Work: Phase four of the Arlington rebuild project will take place in 2008 and 2009. This project includes the rebuild and conversion of 4kV circuits in Arlington to improve reliability of service and add new capacity. This project will establish a new circuit, 320-H7, to come from Station 320 and extend into Arlington. • Trim Plan: Tree profiling and removals in various areas of Arlington • Annual Work: Infrared inspection of all overhead lines

34. SOMERVILLE • Issues: Customer complaints in the Union Square area of Somerville related to outages in the first quarter of the year. Significant work ongoing and upcoming in the Union Square area of the City, including duct bank construction, secondary main work, and transformer upgrades to increase capacity in the square. Additional improvements throughout Somerville to provide increased capacity and system performance. • Rebuild Work: • Re-roof manhole in Union Square, perform the conduit work, transformer upgrades, switching station installations, and secondary main improvements • Install 6-5” PVC conduits along Somerville Avenue from Porter Square to Union Square, +/-8000’ and 15 new manholes • DSS Work: Transfer 2.0MVA of load from DSS line 250-1N90H to DSS line 250-1N38H • Distribution Automation: Three communication/controls to non-radio controlled reclosers • Conversion Work: Convert a portion of 13N33 in Union Square • Annual Work: Infrared inspection of all overhead lines

35. CAMBRIDGE • Issues: Excellent reliability over the past18 months. Several customer complaints have been received mainly as a result of permit outages related to reliability and capacity improvement projects. • Capacity Upgrades: • Reconductor 831-1388 – Replace 10 sections of 500/3c with 3-1000FS and 3-700FS 1500’ of power cable along Putman Street • Install a new DSS line to Belmont, +/-1500Ft of 3-1000FS and 3800’ of 3-700FS. • Relieve existing circuits 828-1325 and 828-1371 by transferring NSTAR load from Belmont lines. • Rebuild Work: 814-12, 817-08 • Network Projects: • Relieve SNV5075 – Replace/upgrade transformer and install additional secondary mains • Relieve City Hall Network – Replace/upgrade transformer, install additional secondary mains, perform conduit upgrades, relocate portions of 4kV primary cable • Station Projects: Transfer the remaining circuits 850-1322, 850-1329, 850-1352 and 850-1386 from H and Q to N and K buses at Station 850 (Kendall) • Additional Circuit Work: Install automated underground switches in various locations, Replace underground oil switches in various locations • Trim Plan: 812-16, 820-24, 822-27, 825-20, 825-27, 827-19, 827-31, 829-19, 829-31 • Annual Work: Infrared inspection of all overhead lines

36. DORCHESTER • Issues: Pockets of poor performance. Multiple conversion projects are ongoing, along with the installation of automated switches for faster sectionalizing and restoration. • 4kV Conversion Projects: 143-02, Convert portions of 321-02, Convert portions of 321-03, Convert portions of 321-05, 483-01, 67-06 • Rebuild Work: Reconductor underground feeder section of circuit 483-H3, Reconductor underground feeder section of circuit 483-H4 • DSS Work: Reconductor DSS line 43-1490H • Additional Circuit Work: Establish tie 466-1482H2/43-1491H, Install automated underground switches in various locations, Replace overhead oil switches in various locations, Rebuild split fiber main areas in various locations, Establish circuit 385-H18 • Tree Trim Plan: • 100% Complete: 143-151H1, 321-02, 321-03, 483-03, 483-H3, 483-H4, 483-H7, 511-1497H2, 511-1497H3 • Ongoing: 139-08, 321-01, 321-05, 441-02, 441-06, 441-07, 466-1482H1 • Annual Work: Infrared inspection of any overhead lines

37. WEST ROXBURY • Issues: Pockets of poor performance.Several complaints in 2008 related to split fiber main areas. Multiple conversion projects are ongoing, along with the installation of automated switches for faster sectionalizing and restoration. • 4kV Conversion Projects: Multi-year project to convert 13-01, 311-08, and 441-05, 284-04, 516-07 • Additional Circuit Work: Circuit capacity project on 344-08, Installation of automated underground switches in various locations, Split fiber main rebuild projects in various locations, Overhead oil switch replacements in various locations • Network Improvements: Capacity project for TNV 649 • Tree Trim Plan: • 100% Complete: 468-01, 468-03, 516-07, 536-76H1 • Ongoing: 284-02, 284-06, 284-08, 374-01, 374-06 • Annual Work: Infrared inspection of any overhead lines