REPLACE COMPRESSED AIR SYSTEM

A REPORT TO

THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES

Electrical

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Mechanical

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9 RMAN J.: UNGAY

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Transmission & Distribution

Telecontrol

System Planning

REPLACE COMPRESSED AIR SYSTEMBay d'Espoir Terminal Station 1

April 2010

newfoundland labrador

h d roa nalcor energy company

Replace Compressed Air System Bay d'Espoir Terminal Station I

Table of Contents

1 INTRODUCTION 1

2 PROJECT DESCRIPTION 2

3 EXISTING SYSTEM 33.1 Age of Equipment or System 63.2 Major Work and/or Upgrades 63.3 Anticipated Useful life 63.4 Maintenance History 63.5 Outage Statistics 73.6 Industry Experience 73.7 Maintenance or Support Arrangements 73.8 Vendor Recommendations 73.9 Availability of Replacement Parts 83.10 Safety Performance 83.11 Environmental Performance 83.12 Operating Regime 8

4 JUSTIFICATION 94.1 Net Present Value 94.2 Levelized Cost of Energy 94.3 Cost Benefit Analysis 94.4 Legislative or Regulatory Requirements 104.5 Historical Information 104.6 Forecast Customer Growth 104.7 Energy Efficiency Benefits 104.8 Losses during Construction 104.9 Status Quo 104.10 Alternatives 11

5

CONCLUSION 125.1

Budget Estimate 125.2

Project Schedule 13

Newfoundland and Labrador Hydro

Replace Compressed Air System Bay d'Espoir Terminal Station 1

1

INTRODUCTION

Bay d'Espoir Generating Station is Newfoundland and Labrador Hydro's (Hydro's) largest

hydroelectric generating station serving the Island Interconnected System, with seven

generating units producing a total capacity of 604 MW. Bay d'Espoir represents

approximately forty percent of Hydro's total Island Interconnected System generating

capacity. The power generated at Bay d ' Espoir is transmitted to the Island Interconnected

System via Bay d'Espoir Terminal Station 1 (Bay d'Espoir).

Circuit breakers play an integral role in the operation of the Island Interconnected System.

The circuit breakers provide fault protection to transmission lines and transformers. They

also provide isolation for the safe execution of work on the same equipment. On the Island

Interconnected System there are 66 air blast circuit breakers, 13 of which are installed at

Bay d'Espoir. There are no plans to replace the 13 230 kV air blast circuit breakers located

at Bay d'Espoir Terminal Station. These breakers are in good working condition and with

overhauls, are expected to last an additional 20 years. These circuit breakers require

compressed air to open and close as well as to extinguish the arc generated by the circuit

breaker operation. To ensure the reliable and optimal operation of these circuit breakers,

high quality compressed air is required.


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2

PROJECT DESCRIPTION

The Bay d'Espoir compressed air project is required to replace the existing terminal station

compressed air distribution system in order to improve the quality of the air supplied to the

air blast circuit breakers.

This project will replace the existing copper, brazed joint air distribution system with

stainless steel piping and welded joints. The supply lines from the plant will be replaced

along with all compressed air lines within the terminal station yard. The compressed air

header enclosure, shown in Figure 1, is the termination point of the supply line from the

plant. Inside the enclosure is a piping arrangement called the header from which

compressed air is distributed to the circuit breakers. The structure also contains

instrumentation such as pressure reducing valves. The enclosure is in disrepair and does

not provide sufficient space to construct a new piping system while keeping the existing

piping system in service. Therefore, a new enclosure will be constructed in the terminal

station yard to house the new header piping and instrumentation for the new compressed

air system.

Figure 1: Bay d'Espoir compressed air header enclosure and three compressed air tanks


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1Replace Compressed Air System Bay d'Espoir Terminal Station

3

EXISTING SYSTEM

To ensure the reliable and optimal operation of these circuit breakers, high quality

compressed air is required. The compressed air must be free of moisture and residue for

proper circuit breaker operation. At Bay d'Espoir, this is provided by a high pressure

compressed air system located in the Bay d'Espoir Generating Station which is maintained

and operated by Hydro personnel. Ambient air is compressed to a pressure of 2.48

megapascals (MPa). Upon leaving a compressor, air is filtered and moisture is removed by

an air dryer. The existing compressed air system includes two air dryers (one primary and

one backup), which dry air to a target dew point temperature of -40 Celsius. This dew point

temperature has historically been Hydro's standard. From the air dryer, the compressed air

flows through distribution piping to supply four receiver tanks. One receiver tank is located

in the power house to operate governors, devices that control the speed of the generators,

and the 13.8 kilovolt (kV) switchgear. Three more receiver tanks are located in the Bay

d'Espoir terminal station. When needed, compressed air flows from the air dryer through

two copper tubes to the receiver tanks in the terminal station yard, approximately 100

metres away. When air is consumed by any of the breakers, replacement air is provided by

these receiver tanks through two pressure reducing valves which reduce air pressure to 1.6

MPa, the operating pressure required for the circuit breakers. One of the two copper tubes

is unable to serve the terminal station and is presently isolated due to high air losses

because of leaks. Leaks in compressed air piping cause air compressors and air dryers to

operate more frequently and for longer periods which result in increased wear on the

equipment, and increased operating and maintenance costs.

High quality compressed air is free of residue and moisture. The water content of

compressed air is expressed as the dew point temperature, i.e. the temperature at which

water vapour starts to condense into liquid water, or form ice when the temperature is

below zero degrees Celsius, for a given volume of air at a constant pressure. The

compressed air supplied to air blast breakers is required to have a very low dew point


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temperature. Hydro has historically accepted -40 Celsius due to standards in equipment

design, however, lower dewpoints are being used by other utilities for the same application.

-50 degrees Celsius is now the adopted standard for all of Hydro's air blast circuit breakers

and is consistent with other utilities' standards and manufacturers' recommendations. If

the dew point temperature of the compressed air exceeds ambient temperatures,

condensation or frost will form in the system. Frost may restrict air flow or block air lines

completely. When frost melts, liquid water can cause corrosion on internal surfaces and

short circuiting. Figure 2 shows internal corrosion on a high voltage breaker's receiver

tank. In a dry air system, this tank should appear as new with no corrosion. This can also

result in catastrophic, explosive failure of a circuit breaker potentially resulting in injury to

any personnel in the area and damage to other equipment. Hydro has experienced two

circuit breaker failures which have been attributed to moisture contamination. One

occurred at the Stony Brook Terminal Station in 1992 and the other at the Hardwoods

Terminal Station in 2002. Figures 3 and 4 show the damage done at the Hardwoods

Terminal Station. Fortunately, those incidents did not result in any personal injury. Repairs

have been made at those sites to fix leaks in the compressed air systems.

Figure 2: Corroded Air Blast Circuit Breaker from Hardwoods Terminal Station


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Figure 3: Breaker B1L36 Failure Due to Moisture Ingress at the Hardwoods Terminal Station.

Figure 4: Failure of Phase B (middle phase) Breaker B1L36 at Hardwoods Terminal Station

It is possible for moisture to enter the existing system downstream of the dryer through

leaks in the tubing. The consequence of these leaks is that the dew point temperature at

the point of use (the circuit breakers) can be higher than at the compressed air source. The

piping joints of the terminal station compressed air system have deteriorated allowing leaks

to develop. In addition, frost heave has displaced trenches and tubing runs, putting stress

on the tubing and joints, which increases the incidence of joint failure and additional leaks.

With these mechanisms for ingress of moisture into the compressed air system, the ability

to maintain the target dew point has been compromised. A leak free compressed air

system should show consistent dew point temperatures throughout the year. Dew point

records for 2009 show a trend for higher dew points during the summer months when


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humidity is higher. This is an indicator of moisture ingress through leaks in the piping

system. Between April 2009 and August 2009, dew points have regularly exceeded -40

Celsius, and have exceeded -35 Celsius on three occasions with a maximum of -31 Celsius

recorded. The sources of moisture ingress will be eliminated by replacing the copper tube

with stainless steel pipe and welded connections. Stainless steel pipe is stronger, more

durable and more corrosion resistant than the existing copper tube and welded joints are

stronger than brazed joints.

3.1 Age of Equipment or System

The Bay d'Espoir Terminal Station air distribution system was constructed in 1968, however,

the power house compressors and air dryers have been replaced since that time. One

compressor was replaced in 1997 and the other compressor was replaced in 2001. The

main air dryer was replaced in 1993 and the back up air dryer was replaced in 2008.

3.2 Major Work and/or Upgrades

There have been no major upgrades to the terminal station air distribution system since

construction. The power house compressors and air dryers have been replaced in recent

years as detailed in Section 3.1.

3.3 Anticipated Useful life

Compressed air systems are depreciated over 40 years.

3.4 Maintenance History

There is no detailed maintenance history available for this asset as Hydro does not maintain

records for these components.


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3.5 Outage Statistics

There have been no forced outages attributed to problems or failures with the compressed

air distribution system.

3.6 Industry Experience

Hydro participates in a discussion forum managed by Doble Engineering, a company that

aids clients in the electric power industry to improve operations and optimize system

performance. Utilizing this forum, Hydro posted a questionnaire to other utilities regarding

moisture problems for air blast circuit breakers. One respondent to the questionnaire,

Manitoba Hydro, addressed air quality issues at their terminal stations by replacing hose

and copper piping with stainless steel pipe and welded connections. This immediately

corrected moisture problems and improved the dew point temperature from -20 degrees

Celsius to -80 degrees Celsius.

The current standard for Hydro Quebec is -80 degrees Celsius at atmospheric pressure

which corresponds to approximately -62 degrees Celsius at the 1.6 MPa operating pressure

in Bay d'Espoir.

3.7 Maintenance or Support Arrangements

Bay d'Espoir is maintained by Hydro personnel.

3.8 Vendor Recommendations

Recommendations vary by source. Air blast circuit breakers are no longer manufactured

and so there is no longer active development or refinement of the requirements of these

breakers. ABB, the manufacturer, has made sometimes conflicting recommendations that

vary from moisture removal by high pressure compression, to one recommendation of -45


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Replace Compressed Air System Bay d'Espair Terminal Station 1

Celsius. Atelier AHR, a manufacturer of replacement parts for the air blast circuit breakers,

recommends an atmospheric dew point temperature of -80 degrees Celsius as used by

Hydro-Quebec. Veronics Instruments, a supplier of dew point monitoring equipment

recommends stainless steel piping for best air quality.

3.9 Availability of Replacement Parts

Replacement parts are readily available for all components of the compressed air system.

3.10 Safety Performance

There is risk of catastrophic failure of a circuit breaker if the dew point temperature rises

above minimum seasonal temperatures, allowing condensation to form inside breakers. A

breaker failure could result in metal and sharp ceramic debris being thrown from the circuit

breaker during an explosive failure which poses a serious risk to personnel in the area at the

time of failure. Hydro has experienced two such failures at other terminal stations.

Fortunately, there were no injuries as a result of these failures. Adequate control and

monitoring of the dew point temperature will reduce this risk.

3.11 Environmental Performance

There are no environmental concerns with the compressed air system.

3.12 Operating Regime

This compressed air system operates continuously.


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4

JUSTIFICATION

This project is justified on the requirement to replace deteriorated infrastructure in order

for Hydro to provide safe and reliable electrical service.

The compressed air distribution system is approximately 42 years old. Leaks have become

common in the brazed joints and compromise compressed air quality. Replacement is

required to restore the integrity of the system.

The compressed air header enclosure is in disrepair and there is insufficient space within

the enclosure to construct a new piping system while maintaining compressed air service to

the terminal station with the old piping system. There is also insufficient clearance between

electrical equipment and piping inside the enclosure to perform modification,

replacements, or repairs to either electrical wiring or piping in close proximity to the

electrical equipment. As a result, it is recommended to construct a new enclosure with

sufficient separation between mechanical and electrical equipment to allow future

replacement or repairs as needed and transfer service to the new system upon completion.

4.1 Net Present Value

A Net Present Value calculation was not performed as there are no viable alternatives.

4.2 Levelized Cost of Energy

Levelized cost of energy is not applicable as there is no new generation source considered.

4.3 Cost Benefit Analysis

A cost benefit analysis is not applicable for this project as there are no quantifiable benefits.


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4.4 Legislative or Regulatory Requirements

There are no legislative or regulatory requirements for this project.

4.5 Historical Information

Hydro received approval, under Board Order No. P.U. 1 (2010), to replace the Holyrood

Terminal Station compressed air system in 2010/2011. The budget cost estimate of the

project is $496,000.

4.6 Forecast Customer Growth

This project is not impacted by forecast customer growth.

4.7 Energy Efficiency Benefits

It is expected that energy efficiency benefits will be realized through reduced operating

hours on the power station compressors. Leaks in the compressed air system result in a

pressure drop in the system. This causes the compressors to operate more often in order to

re-pressurize the system. Implementation of this project will reduce compressed air leaks

and result in lower compressor operating hours. However, the leakage rate has not been

measured; therefore, the benefits can not be quantified.

4.8 Losses during Construction

There will be no losses during construction.

4.9 Status Quo

If the status quo is maintained, the integrity and reliability of the compressed air system


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and thus the circuit breakers and ultimately the Island Interconnected System will continue

to be compromised and the safety risk will remain high.

4.10 Alternatives

There is no viable alternative to replacement of the compressed air distribution system.

As an alternative to replacing the supply line from the powerhouse to the enclosure in the

Bay d'Espoir Terminal Station, Hydro considered construction of a new terminal station

compressed air supply independent of the existing one in the powerhouse. This alternative

would be brought up to the same functional design standard as the replacement option.

However, the cost estimate for new construction exceeds the cost estimate of the

replacement of the existing system by $106,500 which is 16.4 percent higher. The

operating and maintenance cost of this alternative is estimated to be the same or

marginally higher than the proposed new installations.


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5

CONCLUSION

Replacement of the copper piping with stainless steel piping will eliminate air leaks and

reduce the probability of piping failure. This will eliminate moisture ingress in the

compressed air distribution piping and reduce compressor run time. It will also ensure that

consistently dry air is provided to the air blast circuit breakers for optimal, safe operation.

This will improve the reliability and safety of the Bay d'Espoir Terminal Station by reducing

the probability of moisture related breaker failure.

5.1 Budget Estimate

The budget estimate for this project is shown in Table 1.

Table 1: Budget Estimate

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

Material Supply 11.5 0.0 0.0 11.5

Labour 28.0 105.4 0.0 133.4

Consultant 0.0 0.0 0.0 0.0

Contract Work 33.0 318.3 0.0 351.3

Other Direct Costs 4.5 33.2 0.0 37.7

O/H, AFUDC & Escln. 6.9 53.3 0.0 60.2

Contingency 0.0 53.4 0.0 53.4

TOTAL 83.9 563.6 0.0 647.5


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5.2 Project Schedule

The project schedule is shown in Table 2.

Table 2: Project Schedule

Activity Milestone

Project Initiation March 2011

New enclosure construction July 2011

Engineering and Design of Piping System December 2011

Tender for Piping System May 2012

Piping Installation Complete July 2012

Project Closeout August 2012


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REPLACE COMPRESSED AIR SYSTEM

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