system planning telecontrol protection & control civil … · 2010. 8. 16. · telecontrol...

A REPORT TO

THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES

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System Planning

REPLACE 69 kV SF6 Breakers

St. Anthony Airport Terminal Station

April 2010

newfoundland labrador

h d rok ya nalcor energy company

Replace 69 kV SF6 Breakers

6 Table of Contents

1 INTRODUCTION 1

2 PROJECT DESCRIPTION 23.1 Age of Equipment or System 43.2 Major Work and/or Upgrades 43.3 Anticipated Useful life 43.4 Maintenance History 53.5 Outage Statistics 63.6 Industry Experience 63.7 Maintenance or Support Arrangements 63.8 Vendor Recommendations 63.9 Availability of Replacement Parts : 73.10 Safety Performance 73.11 Environmental Performance 73.12 Operating Regime 7

4 JUSTIFICATION 84.1 Net Present Value 84.2 Levelized Cost of Energy 84.3 Cost Benefit Analysis 84.4 Legislative or Regulatory Requirements 84.5 Historical Information 94.6 Forecast Customer Growth 94.7 Energy Efficiency Benefits 94.8 Losses During Construction 94.9 .......................................................................Status Quo 94.10 Alternatives 9

5

CONCLUSION 115.1

Budget Estimate 115.2

Project Schedule 12

Newfoundland and Labrador Hydro


1

INTRODUCTION

The Great Northern Peninsula (GNP) is connected to the Island Interconnected System

through a 138 kV transmission line TL-239 and a 69 kV transmission line TL-226. Both lines

originate at the Deer Lake Terminal Station. Transmission line systems, in general, get

renamed when they terminate at a terminal station before continuing on to another

terminal station. The 69 kV transmission system serving the GNP is composed of four

individual transmission lines, TL-226, TL-227, TL-262 and TL-221. The 138 kV transmission

system serving the GNP is composed of five individual transmission lines, TL-239, TL-259, TL-

241, TL-244 and TL-256. The St. Anthony Terminal Station is supplied by TL-256. The

terminal station has a 15/20/25 MVA, 138/69kV power transformer.

The six 69kV circuit breakers at the St. Anthony Terminal Station are SF6 breakers. Figure 1

shows a typical 69 kV SF6 circuit breaker in use on Hydro's transmission system.

Figure 1: Typical Westinghouse 69kV SF6 Breaker


Page 1


2

PROJECT DESCRIPTION

This project is a two-year plan to replace two 69 kV SF6 circuit breakers, B1T1 and B1L57, at

the St. Anthony Airport Terminal Station. These two breakers will be replaced with new

69kV SF6 breakers.

The scope of work for this project includes the following:

• Purchase and delivery of the new breakers;

• Removal of the old breakers and installation of the new breakers;

• Reconnection of the protection and control equipment; and

• Commissioning of new breakers.

The replacement of breaker B1T1, scheduled for 2011, requires diesel generation at St.

Anthony Diesel Plant to maintain service to a total of 3,700 customers in the St. Anthony,

Roddickton, and Main Brook distribution systems while transmission line TL-256 is taken out

of service. It is expected that diesel generation will be required for approximately 2 weeks

during the off-peak load period.

The replacement of breaker B1L57, scheduled for 2012, does not require diesel generation

as power from the grid can be rerouted through a breaker bypass disconnect to the 930

customers on the Roddickton distribution system and the 260 customers on the Main Brook

distribution system. As no diesel generation is required, the costs for the 2012 portion of

the project are lower than the 2011 costs.


Page 2


3

EXISTING SYSTEM

St. Anthony Airport Terminal Station is the major terminal station on the Great Northern

Peninsula. It is the termination point for the 138 kV transmission line TL-256 from Bear

Cove. The terminal station does not directly provide electrical power to customers but

supplies power to terminal stations at Main Brook and St. Anthony via 69 kV transmission

lines TL-257 and TL-261 respectively. Figure 2 shows a portion of the Island Interconnected

System where the St. Anthony Airport Terminal Station is located on the Great Northern

Peninsula.

Circuit breaker B1T1 at the St. Anthony Airport Terminal Station protects the 15/20/25 MVA

138/69 kV transformer and circuit breaker B1L57 protects the 69 kV transmission line TL-

257 that provides power to the Main Brook Terminal Station.

Both breakers are experiencing gas leaking problems and need to be replaced. Breakers

B1T1 and B1L57 are leaking SF6 gas and as a result have to be topped up with gas at varying

rates. Over the last five years breaker B1T1 had to be topped up a total of 37 times or an

average of once every two months. Breaker B1L57 was topped up a total of ten times over

the last five years, for an average top up period once every six months. When the gas

becomes low in the breaker, the breaker will fail to operate and therefore the reliability of

the system is compromised.


Page 3

Rep/ace 69 kV SF6 Breakers

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Figure 2: GNP Portion of the Island Interconnected System

3.1 Age of Equipment or System

Circuit breakers Bill and B1L57 were manufactured in 1982 and 1983 respectively. Both

were originally put in service at the Plum Point Terminal Station in the year they were

manufactured. They were moved to their current location at the St. Anthony Airport

Terminal Station in 1996 when the Great Northern Peninsula (GNP) intertie was completed.

Both breakers will be 29 years old at the time of replacement.

3.2 Major Work and/or Upgrades

There have been no major upgrades since installation of these breakers.

3.3 Anticipated Useful Life

The normal service life of power circuit breakers is 30 years.


Page 4


3.4 Maintenance History

The five-year maintenance history for breaker B1T1 is shown in Table 1. The costs include

labour and SF6 gas. Fuel costs for diesel generation required for each time maintenance is

performed on breaker B1T1 are not reflected in Table 1. A typical gas refill would require

three hours of diesel generation. This amounts to fuel costs ranging from $22,050 to

$31,500 per year depending on the number of refills needed each year.

Table 1: Five-Year Maintenance History for B1T1

YearPreventive

MaintenanceCorrective

MaintenanceTotal

Maintenance($000) ($000) ($000)

2009 0.0 7.4 7.42008 0.0 5.4 5.42007 0.0 1.5 1.52006 0.3 0.5 0.82005 0.0 1.5 1.5

The five-year maintenance history for breaker B1L57 is shown in Table 2. The costs include

labour and SF6 gas.

Table 2: Five-Year Maintenance History for B1L57Preventive

MaintenanceCorrective

MaintenanceTotal

MaintenanceYear ($000) ($000) ($000)

2009 0.0 0.1 0.1

2008 0.0 0.1 0.1

2007 0.0 2.8 2.8

2006 0.4 1.0 1.4

2005 0.0 0.1 0.1


Page 5


3.5 Outage Statistics

Table 3 lists the five-year average for the performance of 66/69kV SF6 circuit breakers. A

comparison is made between Hydro's last available five-year performance and the latest

CEA five-year average (2003 - 2007). The CEA statistics for 2008 are not yet available.

There have been no forced outages due to problems with these breakers over the past five

years.

Table 3: Outage Statistics Five-Year AverageNumber of

OutagesFrequency

(per annum) 1Unavailability

(%)266/69 kV Breakers (2004 - 2008) 3 0.025 0.023

CEA 66/69kV Breakers (2003 - 2007) 5 0.010 0.008

Frequency (per annum) is the number of failures per year.2 Unavailability is the percent of time per year the unit is unavailable.

3.6 Industry Experience

Hydro regularly consults with the other major Canadian utilities on utility operations and

maintenance matters. These consultations confirm that other utilities have experienced

similar problems with gas leakage in aging SF6 circuit breakers.

3.7 Maintenance or Support Arrangements

All Operation and maintenance work is performed by Hydro personnel.

3.8 Vendor Recommendations

The vendor (Westinghouse) recommends replacing or upgrading power circuit breakers

after 30 years of normal service fife.


Page 6


3.9 Availability of Replacement Parts

Replacement parts for the existing breakers are generally available.

3.10 Safety Performance

A safety hazard to personnel is created when the breaker, which is low on gas, could

explode if subjected to fault conditions.

3.11 Environmental Performance

There are no environmental issues related to this project.

3.12 Operating Regime

Both breakers are in continuous operation.


Page 7


4

JUSTIFICATION

This project is justified on the requirement to replace failing or deteriorated infrastructure

in order for Hydro to provide safe, least-cost, reliable electrical service. The SF6 gas leaks in

the 69 kV breakers, B1T1 and B1L57 cause them to be unreliable and unsafe. The leaks

cause a drop in the breaker's operating pressure which, if left unattended, will result in the

breaker failing to operate when required. A failure could lead to other equipment damage

because the protection normally afforded by the breakers is removed. This would result in a

reduced level of customer service and create safety hazards for personnel.

4.1 Net Present Value

A net present value calculation was not performed as there is no viable alternative.

4.2 Levelized Cost of Energy

This project will not affect the levelized cost of energy because no new generation source is

being considered.

4.3 Cost Benefit Analysis

A cost benefit analysis is not required for this project proposal because there are no

quantifiable financial benefits.

4.4 Legislative or Regulatory Requirements

There are no legislative or regulatory requirements for this project.


Page 8


4.5 Historical Information

A similar project to replace a 69kV SF6 breaker at the Howley Terminal Station was

completed in 2009. It was budgeted at $198,500 and completed at $251,000.

4.6 Forecast Customer Growth

Forecast customer load growth has no effect on this project.

4.7 Energy Efficiency Benefits

There is no energy efficiency benefit 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 current breakers have safety and reliability

issues. The breaker cannot be relied upon to operate in the event of a fault.

4.10 Alternatives

An alternative to replacement of the SF6 breakers is to complete an overhaul in order to fix

the leaks. This is impractical for two reasons. First, leaks are occurring in the pressurized gas

receiver tanks as well as the breaker seals. The cost of replacement parts exceeds the cost

of replacing the whole unit. Second, Hydro's experience with replacing parts has shown that

this provides only a temporary fix. The tank replacement in the Howley Terminal Station in

2007 lasted to 2009 when complete replacement of the breaker was required. The breakers


Page 9

Replace 69 kV SFb Breakers

are 29 years of age and at the end of their useful life, therefore, a complete replacement is

the preferred alternative.


Page 10


5

CONCLUSION

This project is necessary to address the reliability and safety concerns with the SF6 breakers

in the St. Anthony Airport Terminal Station. The breakers are leaking SF6 gas and cannot be

relied upon to operate when necessary. They are at the end of their useful life and need to

be replaced.

5.1 Budget Estimate

The budget estimate for this project is shown in Table 4.

Table 4: Budget Estimate

Project Cost:($ x1,000) 2011 2012 Beyond Total

Material Supply 86.0 86.0 0.0 172.0

Labour 119.5 86.2 0.0 205.7

Consultant 0.0 0.0 0.0 0.0

Contract Work 0.0 0.0 0.0 0.0

Other Direct Costs 218.1 30.2 0.0 248.3

O/H, AFUDC & Escln. 34.9 56.4 0.0 91.3

Contingency 31.3 31.3 0.0 62.6

TOTAL 489.8 290.1 0.0 779.9


Page 11


5.2 Project Schedule

The anticipated project schedule is shown in Table 5.

Table 5: Project Schedule

Activity Milestone

Project Start January 2011

Planning, Site Visit, and Equipment Tendering February 2011

Equipment Delivery B1T1 June 2011

Equipment Installation and Commissioning B1T1 July 2011

Equipment Delivery B1L57 July 2012

Equipment Installation and Commissioning B1L57 August 2012

Project In Service September 2012

Project Completion and Close Out October 2012

Newfoundland and Labrador Hydra

Page 12

system planning telecontrol protection & control civil … · 2010. 8. 16. · telecontrol...

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