A REPORT TO THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES. Electrical. Mechanical. Civil. i Protection & Control. b^n Telecontrol.

Transcription

1 A REPORT TO THE BOARD OF COMMISSIONERS OF PUBLIC UTILITIES Electrical ^ Q ^pfi;sslo4rq Mechanical Civil R LE GD SiG ira rte, E pv/a-07 ^^ O i Protection & Control ^ Gi + 0'''' Transmission & Distribution NfWE b^n Telecontrol System Planning REPLACE UNIT 3 RELAY PANELS Holyrood Thermal Generating Station April 2010 newfoundland labrador h d ro 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 13 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 18 5 CONCLUSION Budget Estimate Project Schedule 23 Newfoundland and Labrador Hydro

3 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 Newfoundland and Labrador Hydro Page 1

4 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. Newfoundland and Labrador Hydro Page 2

5 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. Newfoundland and Labrador Hydro Page 3

6 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 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 Newfoundland and Labrador Hydro Page 4

7 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 Newfoundland and Labrador Hydro Page 5

8 Figure 3: Unit 3 Relay Panels - Compartment 1 of 3 Figure 4: Unit 3 Relay Panels - Compartment 2 of 3 Newfoundland and Labrador Hydro Page 6

9 Figure 5: Unit 3 Relay Panels - Compartment 3 of 3 Figure 6: Unit 3 Relay Panels - showing doors prevented from closing Newfoundland and Labrador Hydra Page 7

10 Figure 7: Unit 3 Relay Panels - showing temporary plexiglass cover Figure 8: Unit 3 Relay Panels - showing poor condition of terminal blocks Newfoundland and Labrador Hydro Page 8

11 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 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 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. Newfoundland and Labrador Hydro Page 9

12 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 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 Newfoundland and Labrador Hydro Page 10

13 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 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 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 (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 Newfoundland and Labrador Hydro Page 11

14 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 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 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 noncorrosive 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 Newfoundland and Labrador Hydro Page 12

15 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 Environmental Performance There are no environmental issues associated with the existing relay panels 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. Newfoundland and Labrador Hydro Page 13

16 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 Newfoundland and Labrador Hydro Page 14

17 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. Newfoundland and Labrador Hydro Page 15

18 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. Newfoundland and Labrador Hydro Page 16

19 HRD relay panels Alternative Comparison Cumulative 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, , 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. Newfoundland and Labrador Hydro Page 17

20 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 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); Newfoundland and Labrador Hydro Page 18

21 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 Newfoundland and Labrador Hydro Page 19

22 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 rewiring 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 Newfoundland and Labrador Hydro Page 20

23 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. Newfoundland and Labrador Hydro Page 21

24 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) Beyond Total Material Supply Labour Consultant Contract Work Other Direct Costs O/H, AFUDC & Escln Contingency TOTAL Newfoundland and Labrador Hydro Page 22

25 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 Newfoundland and Labrador Hydro Page 23

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