REPLACE UNIT 3 RELAY PANELS - Pub · in the three relay panels on Unit 3 with a distributed control system (DCS) that will allow more dependability and better operator control functionality

A REPORT TO

THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES

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System Planning

REPLACE UNIT 3 RELAY PANELS

Holyrood Thermal Generating Station

April 2010

newfoundland labrador

h d roa nalcor energy company

Holyrood - Replace Unit 3 Relay Panels

Table of Contents

1 INTRODUCTION 1

2 PROJECT DESCRIPTION 3

3 EXISTING SYSTEM 43.1 Age of Equipment or System 93.2 Major Work and/or Upgrades 93.3 Anticipated Useful life 93.4 Maintenance History 93.5 Outage Statistics 103.6 Industry Experience 103.7 Maintenance or Support Arrangements 103.8 Vendor Recommendations 113.9 Availability of Replacement Parts 113.10 Safety Performance 113.11 Environmental Performance 133.12 Operating Regime 13

4 JUSTIFICATION 144.1 Net Present Value 154.2 Levelized Cost of Energy 154.3 Cost Benefit Analysis 154.4 Legislative or Regulatory Requirements 174.5 Historical Information 174.6 Forecast Customer Growth 184.7 Energy Efficiency Benefits 184.8 Losses during Construction 184.9 Status Quo 184.10 Alternatives 18

5

CONCLUSION 225.1

Budget Estimate 225.2

Project Schedule 23

Newfoundland and Labrador Hydro


1

INTRODUCTION

The Holyrood Thermal Generating Station (Holyrood) is an essential part of the Island

Interconnected System, with three units providing a total capacity of 490 MW. The

generating station was constructed in two stages. In 1971, Stage I was completed bringing

on line two generating units, Units 1 and 2, each capable of producing 150 MW. In 1979

Stage II was completed bringing on line one additional generating unit, Unit 3, capable of

producing 150 MW. In 1988 and 1989, Units I and 2 were up-rated to 170 MW. Holyrood

(illustrated in Figure 1) represents approximately one third of Hydro's Island Interconnected

system total generating capacity.

Figure 1: Holyrood Thermal Generating Station

The electrical interlock controls for Unit 3 are composed of 167 electromechanical relays

that are installed in one large three compartment enclosure commonly referred to as the

Unit 3 Relay Panels. The hardwired controls contained within these panels allow either the


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manual or automatic operation of all motors, drives and valves installed on Unit 3. As a

result of several modifications that were made to these circuits since they were installed in

1978, the panels that contain these relays have become overcrowded to the point where

the panel doors can no longer be closed. The condition of these panels is considered by the

plant as being a significant safety hazard and a potential point of failure that could result in

an outage on Unit 3.


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2

PROJECT DESCRIPTION

The project is required to replace the existing hardwired relay logic infrastructure contained

in the three relay panels on Unit 3 with a distributed control system (DCS) that will allow

more dependability and better operator control functionality. The installation will be

completed by removing the existing field wiring that terminates inside the existing relay

panels. A new junction box will be installed to house the cabling required for the existing

DCS control to remain functional. A new electrical enclosure containing all the required DCS

hardware will be installed at the existing location and the field wiring will be re-terminated

inside the new DCS control panels. The existing hardwired relay logic will be converted to a

software based operating logic that will allow the system to function as it currently does.

This new DCS hardware will be an expansion to the existing Foxboro DCS control system and

will offer all the benefits of having a single reliable control system operating the entire

plant. This will result in an ergonomically acceptable enclosure layout that will be more

reliable and safer to maintain.


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3

EXISTING SYSTEM

The existing Unit 3 Relay Panels consist of a three section panel or electrical enclosure that

is located inside the Stage Two Relay Room in Holyrood (see Figure 2). This panel makes up

the control logic section of the plant interlock system and controls the operation of most

motors, valves and drives associated with generating Unit 3.

The purpose of this panel is to house the relays, pneumatic timers, current transducers and

terminal blocks that interface the Holyrood Central Control Room controls to the field

mounted equipment that monitors and controls the generating unit. It also houses various

relays that provide the existing automated systems with remote feedback indication. It

serves as an interface panel for equipment that was incorporated into the Foxboro DCS in

2004.

The Unit 3 Relay Panels have become a major safety and operational concern as these

panels are overloaded and crowded. The problem of overcrowding has escalated to the

point where the enclosure equipment doors can no longer be closed. Figures 3, 4 and 5 are

pictures showing the amount of wiring contained in each of the three sections of this panel.

Figure 6 shows how each of the enclosure doors are prevented from closing by the excess

wiring contained inside each enclosure. A custom made plexiglass cover was installed in

2005 to prevent personnel working in the area from accidentally contacting energized

electrical sources (see Figure 7). This plexiglass cover also prevents anyone from trying to

close the doors on this cabinet which could possibly result in a wire being pulled out of a

terminal block resulting in a unit outage.

The physical condition of the terminal blocks inside these panels have deteriorated and are

no longer acceptable. These compression type terminal blocks have become brittle and


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have the tendency to crack whenever maintenance crews tighten them. In some cases, the

bases of several of these blocks have cracked leaving these terminal blocks no longer

connected to the mounting rail that is used to support them inside the cabinet (see Figure

8). As a result, several terminal blocks that contain energized conductors are often left

hanging inside the panel risking exposure to anyone working on the control system.

Figure 2: Unit 3 Relay Panels


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Figure 3: Unit 3 Relay Panels - Compartment 1 of 3



Page 6



Figure 6: Unit 3 Relay Panels - showing doors prevented from closing

Newfoundland and Labrador Hydra

Page 7


Figure 7: Unit 3 Relay Panels - showing temporary plexiglass cover

Figure 8: Unit 3 Relay Panels - showing poor condition of terminal blocks


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3.1 Age of Equipment or System

The Unit 3 Relay Panels were installed in 1978 and commissioned in the spring of 1979

when Stage Two came on line.

3.2 Major Work and/or Upgrades

There have been no major upgrades to the existing Unit 3 Relay Panels since they were

installed in 1978. There have been, however, additions to this panel over the years that

have caused overcrowding to the point that the enclosure doors will no longer close. These

additions include the installation of several motor current transducers in 1993 when the

original Unit 3 control system was converted to a Westinghouse DCS. There have also been

other minor operating logic changes and alarm installations since 1993.

In addition, in 2004, the plant changed the Westinghouse DCS into a Foxboro DCS platform.

At that time, several relays were removed from this panel and placed in the DCS logic. As a

result of this upgrade, new cables had to be installed and terminated in these cabinets

making the cabinets overcrowded and untidy.

3.3 Anticipated Useful life

The Unit 3 Relay Panels is composed mainly of terminal blocks, electromechanical relays

and timers that have an estimated life span of 25 years.

3.4 Maintenance History

Hydro does not separately track maintenance costs for the relay panels. Maintenance costs

for the Unit 3 Relay Panels are included in the costs of other electrical systems.


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Ho/yrood - Replace Unit 3 Relay Panels

3.5 Outage Statistics

There have been no outages directly related to the Unit 3 Relay Panels. However, as this

panel serves as one of the main interface panels to the existing DCS and the plant

equipment, due to the current condition of the panel and the overcrowding of wires, the

panel is considered by Hydro to be a major risk that could lead to an outage on Unit 3.

3.6 Industry Experience

The industry standard is that every electrical enclosure should be designed and sized to

allow for safe access and easy troubleshooting of individual electrical components to enable

performance, reliability, and maintainability of any electrical system.

Utilities are upgrading the older relay based electrical control systems to programmable or

distributed logic control systems. These newer systems offer fault tolerant designs that can

remain operational despite a single point fault failure. In addition, they have a smaller

footprint design, provide easier maintenance and allows for future logic changes without

having to make wiring changes.

3.7 Maintenance or Support Arrangements

The Unit 3 Relay Panels are maintained by Hydro. In the event of a failure, there are

currently no maintenance or support arrangements in place to provide assistance on the

existing control system. However, after this upgrade, the existing service agreement with

Invensys Systems (Foxboro) will cover the new control system for continued operational

support. Hydro personnel will have unlimited access to the Foxboro system support

program, remote system support, and ten hours of on site support per year as well as


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reduced training cost benefits.

3.8 Vendor Recommendations

Invensys Systems, the manufacturer of the existing plant wide DCS control system,

recommends replacing the Unit 3 Relay Panels by moving the hardwired logic into the

existing plant DCS platform.

3.9 Availability of Replacement Parts

Replacement parts are readily available for the existing Unit 3 Relay Panels.

3.10 Safety Performance

The Unit 3 Relay Panels are considered by Hydro as being a significant safety hazard. The

sub standard condition of these panels resulted in the submittal of a safe workplace

observation program (SWOP) condition. The results of the investigation into this condition

revealed that the panels contain sub-standard or poor wiring that present shock hazards to

personnel working inside these panels. It also revealed that the amount of wiring located

inside these panels will impede or delay future maintenance.

Rule number 2-118 of the Canadian Electrical Code states that "Electrical equipment shall

be installed as to ensure that after installation there is ready access to nameplates and

access to parts requiring maintenance". Rule number 12-3034 (2)(a)(ii) of the Canadian

Electrical Code states that enclosures identified shall be only permitted to be used as

junction boxes "where wiring is being added to an enclosure forming part of an existing


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installation and the conductors, splices and taps do not fill the wiring space at any cross

section to more than 75 percent of the cross sectional area of the space". Rule 11.2.1.1 of

the National Fire Protection Association (NFPA) 79 Electrical Standard for Industrial

Machinery states that "Ail items of control equipment shall be placed and oriented so that

they can be identified without moving them or the wiring. " Rule 11.2.1.2 of this same code

states that terminal blocks shall be mounted to provide unobstructed access to the

terminals and their conductors. As a result of these deficiencies, it is evident that the

condition of the Unit 3 Relay Panels does not meet Canadian Electrical Code or other

electrical standards and is thus a potential safety hazard to anyone working inside these

enclosures.

In addition to the code deficiencies outlined above, the physical condition of the terminal

blocks located inside the panels have deteriorated and are no longer acceptable. These

compression type terminal blocks have become brittle and have the tendency to crack

whenever maintenance crews tighten them. In some cases the bases of several of these

blocks have cracked leaving these terminal blocks no longer connected to the mounting rail

that is used to support them inside the cabinet. As a result, terminal blocks that contain

energized conductors are often found floating inside the panel risking exposure to workers.

The plant standard for Electrical Equipment Enclosures (standard MSTD-059) states that

enclosures shall be National Electrical Manufacturers Association (NEMA) 12 rated or

greater when installed in any area of the plant not exposed to damp or corrosive

environments. NEMA 12 is a standard from the National Electrical Manufacturers

Association, which defines enclosures with protection against dirt, dust, splashes by non-

corrosive liquids, and salt spray. The panels do not meet this requirement, since the doors

of the enclosures will no longer close. As a result, air borne dust, fibers or splashing water is

free to enter these enclosures. In addition, since the doors of these enclosures no longer


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close, if an electrical fire was to occur inside these panels, it would spread to the

surrounding areas with the possibility of causing significant equipment damage and

personnel injury or death. Although the plexiglass barrier does provide some additional

protection, it is a temporary installation that does not meet Hydro standards.

3.11 Environmental Performance

There are no environmental issues associated with the existing relay panels.

3.12 Operating Regime

Unit 3 has the capability to operate in generation or synchronous condense modes. This

unit operates predominately in the generation mode in the winter and in synchronous

condense mode for summer months to provide voltage support to the Island

Interconnected System.

The controls in the Unit 3 Relay Panels are vital to the operation of the generating unit

whether it is in generation or synchronous condense mode. In addition, there are relays and

wiring contained in this panel that monitor and control auxiliary functions of the turbine

that are required even when the generating unit is not in service. The relay panels are

essential to the daily operation of the plant whether or not Unit 3 is operating.


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4

JUSTIFICATION

This project is justified on the need to replace sub-standard equipment and eliminate safety

hazards. Unit 3 Relay Panels are overcrowded with wiring which prevents the doors from

being able to close. There is a risk of an electrical fire occurring inside the panels that could

spread to the surrounding areas of the plant leading to significant equipment damage and

potential personnel injury or death.

There are several direct violations of the Canadian Electrical Code and other applicable

standards pertaining to the condition of these panels. In addition, the plant maintenance

personnel have identified the panels as an area of significant safety concern and expressed

direct concerns about working inside these panels.

As a result of the age of these panels and the amount of wiring contained inside them, the

terminal blocks that are used to terminate energized conductors inside the panel have

become very brittle. This has lead to them cracking in the areas that hold the conductors

and on the bases that hold the block to the mounting rail inside the panel. As a result,

energized terminal blocks are hanging inside the panel. In addition, maintenance crews

have also found non terminated energized conductors inside this enclosure.

Also, by integrating the relay controls into the existing DCS system, the future availability of

Unit 3 will be improved. The Foxboro DCS control system offers a fault tolerant design and a

redundant communication network that will continue to operate despite a single point

failure. The proposed upgrade will also allow easier system troubleshooting after a failure

and offers the advantage of being able to make future changes in software as opposed to


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having to make physical wiring changes.

4.1 Net Present Value

A net present value analysis was not performed considering two alternatives. Please see

section 4.3 `Cost Benefit Analysis' for details.

4.2 Levelized Cost of Energy

A levelized cost of energy analysis is not applicable since no new generation sources are

being evaluated.

4.3 Cost Benefit Analysis

The following two viable alternatives were evaluated in a cost benefit analysis:

• Alternative 1: Replacement with DCS System. Replace the existing relay panels and

relay logic with a new panel equipped with a DCS controlled system (total proposed

capital cost of $830,700);

• Alternative 2: Replacement with Electromechanical Relays. Replace the existing relay

panels and relay logic with a new relay panel equipped with electromechanical

relays (total proposed capital cost of $676,500).

These two alternatives were evaluated using a cost benefit analysis. The analysis included

the following assumptions:

• The study period for the cost benefit analysis is 25 years, (2012 to 2037).

• Electromechanical relays have an anticipated useful life of 25 years.

• The DCS option has an anticipated useful life of 15 years and carries an additional

cost of $75,000 in year 2027 to replace any obsolete hardware after the 15 years.


Page 15


• To assure that both alternatives are compared equally, it is assumed that 1/3 of the

value remaining in the DCS system hardware to be installed in 2027 can be

recovered at the end of 25 years (2037) since it has an anticipated lifespan of 15

years and has only been in service for ten years.

• $3,500 per annum is allowed for engineering to investigate electrical faults in the

electromechanical relay alternative since there would be no single common plant

wide control system equipped with Sequence of Events monitoring.

+ $4,100 per annum after year ten is allowed for maintenance work in the

electromechanical relay alternative.

• An extra $50,000 every ten years is allowed for completing wiring changes inside the

electromechanical relay panels for major upgrades that require significant rewiring

as opposed to simple logic changes required if the DCS alternative was installed.

+ Electromechanical relays do not offer internal diagnostics that quickly indicate the

source of a failure. In the event of an outage of unit 3 prior to 2020, as a result of an

electromechanical relay failure, requiring the gas turbines to be dispatched for 15

hours would cause the cost benefit analysis to be in a virtual break even position.

Using the average required gas turbine energy values for this period (637 MWh) it

was determined that the incremental cost of fuel for gas turbine operation over the

No. 6 Heavy oil which is burned in Holyrood, will result in an additional cost of

$93,668 in the electromechanical relay option.

Using these assumptions, the results of the cost benefit analysis showed that the

Electromechanical Relay Alternative is slightly more expensive over the 25 year anticipated

useful life of the project. Figure 9 shows the results.


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HRD relay panelsAlternative ComparisonCumulative Net Present Value

To The Year

2037

Alternatives

Cumulative

Net Present

Value [CPW[

CPW Difference between

Alternative and the

Least Cost Alternative

DCS Alternative

Electromechanical Relay Alternative

776,237

778,032

0

1.795

Figure 9: Cost Benefit Analysis 1 Summary Table

4.4 Legislative or Regulatory Requirements

As stated in rule 478(1) of the Newfoundland and Labrador Occupational Health and Safety

Regulations 2009 "an electrical installation, equipment, apparatus and appliance shall

conform to the requirements of the Canadian Electrical Code as adopted in the Electrical

Regulations under the Public Safety Act". As a result of the existing Canadian Electrical Code

deficiencies outlined in the safety performance section of this report, Hydro has decided

that this installation should be brought up to standard.

4.5 Historical Information

There is no historical information associated with this proposal as there have been no

similar replacements of the existing control systems.


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4.6 Forecast Customer Growth

Forecast customer growth has no impact on this project.

4.7 Energy Efficiency Benefits

There are no energy efficiency benefits associated with upgrading the existing relay control

panels.

4.8 Losses during Construction

There will be no anticipated energy losses while upgrading the existing control systems. The

electrical controls in the panels will be integrated into the Foxboro DCS during the planned

annual outage.

4.9 Status Quo

The status quo relay based control system is not an acceptable alternative. Due to safety

concerns with the existing system, the age and condition of the equipment, the relay panels

need to be replaced.

4.10 Alternatives

When evaluating this project, Hydro has considered the following two alternatives:

+ Replacement of the existing relay panels and relay logic with a new panel equipped

with a DCS controlled system (total proposed capital cost of $830.7K);


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• Replacement of the existing relay panels and relay logic with a new panel

equipped with electromechanical relays (total proposed capital cost of $676,500).

Despite the fact that the upfront capital cost of the DCS alternative is more than

the electromechanical relay alternative, in the event of a single electromechanical

relay failure that results in Unit 3 becoming unavailable, the DCS alternative

becomes the more cost effective option. As a result of this fact and the following

benefits gained with going with the DCS alternative, Hydro has decided to proceed

with the DC5 alternative:

• Overall safer system since maintenance and troubleshooting can be completed

from the safety of the control room - The DCS system allows maintenance crews

to observe the status of input and outputs from an engineering workstation

located inside the control room. However, in the electromechanical relay

alternative, maintenance crews would have to work inside energized electrical

panels when trying to perform maintenance and troubleshoot problems.

• More dependable system as solid state relays contain no moving parts -• DCS

outputs operate using an electronic switch or transistor which contains no moving

parts. As a result, fewer faults will occur on the DCS system which will result in

more dependable operation of the Unit 3 generator;

• Easier troubleshooting capabilities since there is less wiring and electrical

components to fail - In the event that an electromechanical relay was to fail,

several hours or possibly days would be spent trying to determine the source of

the problem. This will lead to extended system unavailability or possibly a Unit 3

outage. The DCS alternative offers built in internal diagnostics, that will alert

operators of a problem immediately;

• Built in fault tolerance that can accept some single point control system failures

- Since the DCS option contains redundant processors and communications, the


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system will continue to operate despite a failure on any of these critical

components;

• Smaller equipment footprint that frees up valuable plant real estate - When

replacing the existing system with electromechanical relays, a much larger panel

would be required to house all the relays and wiring than what would be required

if the DCS alternative was used. Currently, there is very little extra room inside the

Stage 2 relay room for a larger enclosure;

• Easier future upgrade capabilities that will not involve wiring changes for simple

logic changes - The DCS alternative will allow technicians to make simple logic

changes by re-configuring software as opposed to spending hours or days re-

wiring relays. In addition, it will allow more complicated logic processes to be

installed in the event that any future plant upgrades take place. The

electromechanical relay option only supports discrete relay logic and does not

offer any advanced control capabilities such as analog inputs, analog outputs,

closed loop control, accurate timing functions and counting functions;

• Reduced commissioning time required to fix errors as small logic changes are

made much easier in software than in hardwired systems - If during

commissioning, any logic changes are required, the DCS alternative will allow these

changes to be made without having to change any of the wiring or equipment

inside the panel. However, if changes are required when using the

electromechanical relay alternative, this could result in hours or days of re-wiring

and if the change is significant enough, there may not be any extra space inside

the panel to add extra relays;

• Better automation capabilities and much faster control processing speeds

available in DCS controlled system - The DCS alternative will allow engineering to

program alarms and other automation logic into the system that will inform


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operators when something has gone wrong in the process. It will also operate at

much faster speeds than relay logic allowing the process to respond to changes

much faster than they currently do;

+ Common plant wide control system that allows operators to analyze faults and

historically trend and display any information required -The existing DCS is

equipped with sequence of events recording capabilities and historical trending of

all inputs and outputs. These features will allow operators and engineering to

quickly analyze faults and disturbances by knowing exactly what events occurred

at the time of a fault.

• DCS system allows for remote monitoring and control of systems via HMI

computers or operator workstations -The DCS alternative will allow the

operators inside the control room to see the entire process on one Human

Machine Interface (HMI) computer screen. This system will allow automatic

alarming capabilities and will reduce the amounts of lights, switches and

pushbuttons currently installed inside the control room. It will therefore

streamline the operation of the process and will reduce the chances of operator

error. In addition, it will allow future control room modernization to take place

without having to replace any of these systems.


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5

CONCLUSION

The Unit 3 Relay Panels must be upgraded to ensure the safety of Hydro's maintenance

crews and the overall operational reliability of the Holyrood plant. The existing hardwired

control panels are over 30 years old and are overcrowded with wiring to the point that the

doors of this panel will no longer close. These panels are in direct violation of several

Canadian Electrical Code rules and pose significant safety hazards to anyone working inside

these panels.

Hydro is proposing that the existing panels be replaced and the hardwired controls be

integrated into the existing plant wide Foxboro DCS control system.

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 23.0 10.0 0.0 33.0

Labour 107.2 157.5 0.0 264.7

Consultant 0.0 0.0 0.0 0.0

Contract Work 112.5 210.4 0.0 322.9

Other Direct Costs 0.6 13.5 0.0 14.1

O/H, AFUDC & Escln. 33.8 98.7 0.0 132.5

Contingency 0.0 63.5 0.0 63.5

TOTAL 277.1 553.6 0.0 830.7


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5.2 Project Schedule

The anticipated project schedule is shown in Table 2.

Table 2: Project Schedule

Activity Milestone

Project Initiation January 2011

Review existing drawings and develop I/O list March 2011

Develop contract for Foxboro and issue Purchase Order June 2011

Finalize Engineering Drawings and Design September 2011

Develop DCS Programming November 2011

Develop Electrical Installation Contract February 2012

Complete Factory Acceptance Testing April 2012

Complete Installation and Commissioning July 2012

In Service September 2012

Project Completion and Close Out December 2012


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Documents

REPLACE UNIT 3 RELAY PANELS - Pub · in the three relay panels on Unit 3 with a distributed control system (DCS) that will allow more dependability and better operator control functionality