A REPORT TO THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES. Electrical. Mechanical. Civil. Protection & Control. Transmission & Distribution

Transcription

1 A REPORT TO THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES Electrical.1_ UFSS#p A:_. DAVID/ IC, L re Mechanical Civil Protection & Control an LAND& 4^ Transmission & Distribution Telecontrol System Planning REPLACE 230 KV CIRCUIT BREAKER Sunnyside Terminal Station April 2010 newfoundland labrador h dro a nalcor energy company

2 Table of Contents 1 INTRODUCTION 1 2 PROJECT DESCRIPTION 3 3 EXISTING SYSTEM : Age of Equipment or System : : Major Work and/or Upgrades Anticipated Useful life Maintenance History Outage Statistics Industry Experience Maintenance or Support Arrangements Vendor Recommendations Availability of Replacement Parts Safety Performance Environmental Performance Operating Regime 8 4 JUSTIFICATION Net Present Value Levelized Cost of Energy Cost Benefit Analysis Legislative or Regulatory Requirements Historical Information Forecast Customer Growth Energy Efficiency Benefits Losses during Construction Status Quo Alternatives 10 5 CONCLUSION Budget Estimate Project Schedule 13 Newfoundland and Labrador Hydro

3 1 INTRODUCTION Newfoundland and Labrador Hydro (Hydro) owns and operates 54 terminal stations in the Island Interconnected System. A critical element in a terminal station is the circuit breaker. The circuit breakers protect the transformers and transmission lines from overloading. They operate automatically in the same way as circuit breakers or fuses operate to protect the circuits in a normal household electrical system. The circuit breaker senses excessive current and uses a compressed spring arrangement to open the breaker contacts and cut off the power flow to the circuit. This protects the electrical equipment from damage caused by high currents that occur during an electrical fault. The circuit breakers that operate at 230 kv interrupt currents up to 4,000 Amperes. In the Island Interconnected System, Hydro owns and operates kV circuit breakers of which 53 are air blast circuit breakers. Figure 1 shows a picture of a typical 230 kv air blast circuit breaker in use on the Island Interconnected System. When the Island Interconnected System was originally constructed, the standard technology for circuit breaker design was air blast technology. As the electrical utility industry developed, advances in circuit breaker technology changed from air blast technology to Sulphur Hexafloride (SF 6) technology. The main difference in the two technologies is that air blast circuit breakers use a compressed air system to operate whereas SF6 circuit breakers use an inert gas. An inert gas is a chemically stable gas that can be used to extinguish electrical arcing at high temperatures. Since the mid 1980's, SF6 gas technology has been used. The SF6 gas is contained inside the sealed chamber of the breaker. This inert gas extinguishes the arc across the breaker contacts when the circuit is being interrupted. The advancement to SF6 gas means that breakers can be self contained and do not need a centralized compressed air supply to operate as required by air blast breakers. Also, SF6 circuit breakers have the ability to Newfoundland and Labrador Hydro Page 1

4 interrupt larger currents and withstand higher voltages than the air blast circuit breakers. The utility industry is switching to SF6 technology. The 230 kv circuit breakers that required replacement on the Hydro system over the last twenty years have been replaced by SF6 gas breakers. Figure 1: Typical 230 kv Air Blast Circuit Breaker Newfoundland and Labrador Hydro Page 2

5 2 PROJECT DESCRIPTION This project consists of the replacement of the existing 230 kv air blast circuit breaker L03L06 at the Sunnyside Terminal Station with a new 230 kv SF6 circuit breaker. The scope of the work involves the following: Removal and retirement of the existing breaker Purchase and installation of a new breaker Supervision of the factory acceptance test of the new breaker Construction of a new foundation for the circuit breaker structure Installation of new protection equipment and control cables Commissioning of the new breaker. Newfoundland and Labrador Hydro Page 3

6 3 EXISTING SYSTEM The Sunnyside Terminal Station (Sunnyside) is located just off the Trans Canada Highway near the junction to the community of Sunnyside. The terminal station is approximately 20 kilometers east of Clarenville. Sunnyside is one of Hydro's major terminal stations. It is the termination point for the 230 kv transmission lines TL-202 and TL-206 from Bay d'espoir. It is the focal point for transmission of power to the Avalon Peninsula. The 230 kv transmission line TL-203 originates at Sun nyside and transmits power to the Western Avalon Terminal Station. Also, the 230 kv transmission line TL-207 transmits power from Sunnyside to the Come By Chance oil refinery. Electrical power to the Burin Peninsula is supplied from the Sunnyside Terminal Station via 138 kv transmission lines TL-212 and TL Also, Sunnyside supplies power to Clarenville and surrounding area via Newfoundland Power's transmission system. Figure 1 shows part of the Island Interconnected System and indicates the location of Sunnyside. CLARENVILLE M MILTON \ Figure 2: Portion of the Island Interconnected System showing Sunnyside At Sunnyside, there are five 230 kv air blast circuit breakers. L03L06 is a 230 kv circuit breaker used as part of the protection scheme at the terminal station for transmission lines Newfoundland and Labrador Hydro Page 4

7 TL-203 and TL-206. This breaker has deteriorated and requires replacement in order for Sunnyside to continue its vital role as part of the Island Interconnected System. Figure 3 shows some of the deterioration of L03L06. Figure 3: Corrosion on Breaker at Sunnyside 3.1 Age of Equipment or System Circuit breaker L03L06 was manufactured by Brown Boveri and was installed in It is 44 years old. Newfoundland and Labrador Hydro Page 5

8 3.2 Major Work and/or Upgrades An overhaul of this breaker was done in 2000 at a cost of $115,800. A complete relubrication was done on the breaker in 2007 at a cost of $19, Anticipated Useful Life The anticipated useful life of a power circuit breaker is 30 years. 3.4 Maintenance History The maintenance history for Breaker L03L06 is shown in the following Table 1. Table 1: Maintenance History Preventive Maintenance Corrective Maintenance Total Maintenance Year ($000) ($000) ($ 000) Outage Statistics Table 2 below lists the previous 5 year average for the performance of 230 kv Air Blast Breaker. A comparison is made between Hydro's last 5 year performance to the latest CEA five year average ( ). There has been one forced outage of the Sunnyside L0306 circuit breaker in the last 15 years. There have been 25 forced outages due to problems with the air blast breakers over Newfoundland and Labrador Hydro Page 6

9 the last 15 years, throughout the Hydro system. 230 kv Air-Blast Breakers ( ) CEA 230 kv Air-Blast Breakers ( ) Table 2: Outage Statistics Number of Forced Frequency Outages (per a) 1 Unavailability (percent) Frequency (per a) is the number of failures per year. 2 Unavailability is the percent of time per year the unit is unavailable. 3.6 Industry Experience Through consultations with other Canadian utilities, Hydro has confirmed that the 230 kv air blast circuit breakers of other utilities present similar operational problems as those on the Hydro system. Such problems are corrosion, leaking seals, porcelain failures, malfunctioning valves and unreliable controls. These operational problems begin to occur when the breakers have reached between 20 and 30 years of service. In addition, Hydro consulted with the manufacturer, Asea Brown Boveri who confirmed the existence of the above mentioned problems are typical among utilities using these breakers. Other utilities are either replacing or upgrading the air blast circuit breakers. 3.7 Maintenance or Support Arrangements Normal operation and maintenance work is performed by Hydro Operations personnel. 3.8 Vendor Recommendations The vendor, Asea Brown Boveri, recommends replacing the breaker because of the condition of the tank. If the tank was in a better condition the breaker could be upgraded. Newfoundland and Labrador Hydra Page 7

10 3.9 Availability of Replacement Parts Replacement parts for the existing breaker are generally readily available Safety Performance Regular maintenance inspections of the circuit breaker indicate that the compressed air tanks no longer meet current safety codes. The minimum tank wall thickness for this type of breaker under ASME Section VIII Division 1, UG-27 is 3.84 mm. The minimum measured thickness of the tank wall is 2.94 mm Environmental Performance There are no specific environmental issues regarding the air blast breakers Operating Regime Circuit breaker L03L06 is in continuous operation. Newfoundland and Labrador Hydro Page 8

11 4 JUSTIFICATION This project is justified on the requirement to replace failing or deteriorated infrastructure in order for Hydro to provide safe, reliable electrical service. Because of corrosion, the tank walls for circuit breaker L03L06 are not up to industry standards. This creates the risk of a tank rupture which is a major safety and reliability concern. Also, the circuit breaker is 44 years old and beyond its anticipated useful life of 30 years. The only practical option is to replace the breaker. 4.1 Net Present Value A net present value calculation was not required for this project as there is only one viable alternative. 4.2 Levelized Cost of Energy This project does not affect the levelized cost of energy because it does not involve any new sources of generation. 4.3 Cost Benefit Analysis A cost benefit analysis is not required because there are no quantifiable benefits. 4.4 Legislative or Regulatory Requirements There are no legislative and regulatory requirements for this project. Newfoundland and Labrador Hydro Page 9

12 4.5 Historical Information Hydro has not replaced any 230 kv circuit breakers within the past five years. 4.6 Forecast Customer Growth The forecast customer load growth has no affect on this project. 4.7 Energy Efficiency Benefits There are no energy efficiency benefits associated with this project. 4.8 Losses during Construction There are no losses during construction associated with this project. 4.9 Status Quo The status quo is not an option because the circuit breaker has safety and reliability problems Alternatives A repair of the corroded sections on the compressed air tank was considered. This was not possible because the existing tanks are glass lined and any attempt to weld them would damage the lining and further damage the breaker. As well, any attempt to repair the tanks would require a complete disassembly and reassembly of the breaker. The labour and materials costs for this option, plus the outage time required for the work, is expected to Newfound/and and Labrador Hydro Page 10

13 exceed the costs for a replacement by approximately $200,000. Because the major deficiency is in the tanks, it is not cost effective to try to repair the breaker. The most effective means to correct the problem is to completely replace the breaker. Hydro's air blast breaker upgrade program which has been ongoing for the last five years involves upgrade of the interrupters, resistors and capacitors. This type of upgrade is possible only if the breaker tank is in good condition. If the breaker tanks are damaged or corroded then the upgrade option is not practical or feasible. Thus, there are no viable alternatives to correcting the problem described in this proposal other than to replace the breaker completely. Newfoundland and Labrador Hydro Page 11

14 5 CONCLUSION This project is necessary to address the reliability and safety concerns identified on Breaker L03L06 in the Sunnyside Terminal Station. Maintenance inspections have shown that the compressed air tank on the breaker is corroded and the tank walls no longer meet industry standards. Because of the corrosion there is a risk of the tank rupturing and causing a safety hazard. Repair of the breaker is not practical or feasible. The only viable alternative is a complete replacement of the breaker. 5.1 Budget Estimate The budget estimate for this project is shown in Table 3. Table 3: Budget Estimate Project Cost:($ x1,000) Beyond Total Material Supply Labour Consultant Contract Work Other Direct Costs O/H, AFUDC & Escln Contingency TOTAL Newfoundland and Labrador Hydro Page 12

15 5.2 Project Schedule The project schedule is shown in Table 4. Activity Table 4: Project Schedule Milestone Project Start April 2011 Initial Planning and Equipment Tendering August 2011 Equipment Delivery May 2012 Equipment Installation July 2012 Commissioning July 2012 Project In Service August 2012 Project Completion and Close Out December 2012 Newfoundland and Labrador Hydro Page 13