( pages) ICM Prject Statin Infrastructure and Equipment Statins Switchgear Transfrmer Statins Segment Trnt Hydr Electric System Limited (THESL)
I EXECUTIVE SUMMARY 0. Prject Descriptin Switchgear perating at.kv in many dwntwn Transfrmer Statins (TS) are past the end f their useful lives and rely n bslete technlgy such as brick and mrtar enclsures, nn arc resistant designs with air blast r air magnetic circuit breakers and mechanical relays and are in pr cnditin (See Sectin II, ). The existing nn arc resistant switchgear des nt channel the energy released during an internal arc fault t minimize ptential injury t persnnel and minimize damage t surrunding equipment. As a result, this switchgear can cause damage that impacts the entire statin, interrupting service t thusands f custmers. This equipment has been kept in service via increased maintenance, custm fabricatin and harvesting parts frm spares. The asset cnditin cntinues t deterirate and safety cncerns are increasing. Switchgear requiring replacement in 0, 0, and 0 include the A T switchgear at Strachan TS, A E switchgear at Carlaw TS, A W and A W switchgear at Wiltshire TS, A WR switchgear at Windsr TS and A DX at Duplex TS. All but ne f these are mre than years ld. The ttal cst f this segment is apprximately $. millin fr the jbs shwn in Table 0 Table : Jb Csts Estimate Jb Title Year Custmer Jb Year Cst Number Installed Lad Estimate Served ($M) (MVA) Strachan TS A switchgear 0 0. replacement preparatin Strachan TS A switchgear 0. replacement
Estimate Jb Title Year Custmer Jb Year Cst Number Installed Lad Estimate Served ($M) (MVA) S0 Strachan TS Lad Transfer frm A T t A T Switchgear 0 0.0 0 Carlaw TS A E switchgear 0. replacement 0 Wiltshire TS A W 0 0.0 switchgear replacement Wiltshire TS A W 0. switchgear replacement Windsr TS A WR 0. switchgear replacement 0 Duplex TS A DX switchgear 0. replacement Ttal. These switchgear were selected fr replacement based n the fllwing cnsideratins: Obslescence (brick structures, nn arc resistant design, bslete breakers) Age Cnditin Space available fr transitin switchgear, and Statin egress fr cabling All the switchgear listed are t be replaced with,000a air insulated, arc resistant type C switchgear with duble bus, duble breaker r breaker and half cnfiguratin except Duplex
switchgear which will be replaced with gas insulated switchgear (GIS) due t space cnstraints. These switchgear will be fitted with mdern vacuum circuit breakers and digital relays.. Why the Prject is Needed Nw 0 Mst f the equipment prpsed fr replacement is ver 0 years ld ( years n average) and well past their design useful life. THESL has been able t cntinue perating this equipment because it has paid particular attentin t equipment maintenance and has had veteran statin mechanics ver the years that have been able t harvest spare equipment fr parts that are n lnger manufactured. In sme cases, THESL has been frced t custm fabricate certain parts which is expensive, unreliable, and unsustainable. The cst t repair bslete equipment using custm fabricated parts is mre than twice the cst when spare parts are supplied by manufacturers. THESL has had several incidents f internal arc faults in its nn arc resistant switchgear. Fr example, an internal arc fault at Terauley TS in 00 resulted in an explsin in the circuit breaker cmpartment and caused the frnt dr t fly away frm its munts as shwn in Figures and, damaging ther equipment in the vicinity. Frtunately n THESL persnnel were in the vicinity when the explsin ccurred.
Figure : [00] Pthead failed inside Terauley TS switchgear Figure : [00] Impact f internal arc fault in a switchgear Internal arc faults can be destructive because f the energy levels reached within the cnfined cmpartment. The risk f this type f event n nn arc resistant switchgear increases as switchgear ages. This incident resulted in a lss f service t, custmers fr hurs.
The asset cnditin assessment fr switchgear have cnfirmed that their cnditin is categrized as pr, based n the 00 Kinetrics study reprt. That reprt recmmends that switchgear in the pr categry be replaced within three years. 0 In additin t the cnsequences f in service failures, the existing circuit breakers in all f the switchgear, except Duplex TS, are air blast circuit breakers which are bslete. These breakers have much higher maintenance csts. The maintenance f air blast circuit breakers is labur intensive and takes at least twice as lng as mdern vacuum circuit breaker. Replacement parts fr the air blast circuit breakers are n lnger manufactured, and they must be custm manufactured when required. In additin, the air supply systems assciated with the air blast breakers have als reached end f life. At least ne air supply system ut f a ppulatin f fails per year and the average cst f repair is $,000 per incident n tp f the planned maintenance which csts $,00 per year per statin.. Why the Prject is the Preferred Alternative 0 THESL cnsidered the fllwing ptins, which are fully discussed in Sectin IV: ) Cntinue t maintain and perate the existing equipment ) Transfer lad t adjacent TS ) Replace Existing Switchgear with an Arc Resistant Design and Vacuum Breakers Optin is essentially a run t failure scenari with replacement f existing switchgear when failure ccurs. This ptin has the ptential t defer capital investment, but replacement will eventually be required and will cst apprximately 0% mre if dne n an emergency basis. In the interim, the ptential fr damage t ther equipment and injury will remain (See Sectin IV, ). Given the age and cnditin f this switchgear and the difficulty in btaining spare parts, this ptin is nt preferred. 0 Optin is nt feasible because in rder t undertake a transfer, the receiving TS wuld require spare capacity, sufficient feeder psitins, and physical space fr additinal infrastructure. The
lcatin f the receiving statin wuld als need t be sufficiently clse t the lad centre t avid a vltage drp. These cnditins cannt be met fr any f the TS addressed by this segment (See Sectin IV, ). 0 Optin, which wuld install new arc resistant design switchgear and vacuum breakers is the preferred alternative because it ffers the fllwing benefits (See Sectin IV, ): Mitigate the safety risk t the perating persnnel and damage t equipment in the TS due t the arc resistant design f the switchgear. Minimize the maintenance and perating cst since the new switchgear will eliminate the air blast circuit breakers alng with the air supply system (air cmpressrs) whse maintenance cst is at least twice that f mdern vacuum circuit breakers. The cnfiguratin f the switchgear will als be duble bus duble breaker r breaker and half and this type f cnfiguratin cuts maintenance and perating time at least by half. Increase reliability because arc resistant switchgear with duble bus duble breaker r breaker and half cnfiguratin is mre reliable. In cntrast t the existing switchgear, the new switchgear will allw any circuit breaker t be taken ut f service withut requiring lad transfer. 0 Carrying ut immediate wrk n this asset class is expected t result in the avided estimated risk cst f apprximately $ millin, as ppsed t executing this wrk in 0 as shwn in the Business Case Evaluatin in Appendix. Therefre, there are ecnmic benefits t ratepayers fr executing this wrk nw. As a practical matter given available resurces, jbs are scheduled ver three years t allw engineering, prcurement, cnstructin and cmmissining and are clsely crdinated with feeder transfers t minimize custmer utages and limit single supply cntingency.
II DESCRIPTION OF WORK. Strachan TS A T Switchgear.. Jb Descriptin The bjective f these jbs is t design and install.kv switchgear t replace the existing A T switchgear at Strachan TS with 000A air insulated arc resistant type C switchgear with duble bus, duble breaker r breaker and half switchgear in 0 0. 0.. Scpe f Wrk A T... Scpe f wrk in 0 Remve the existing decmmissined A T switchgear frm Building A Prepare the space vacated by the A T switchgear in Strachan TS building A t install new A T that will replace existing A T switchgear 0... Scpe f wrk in 0 Design, prcure, and purchase a new.kv, MVA, wire air insulated arc resistant type C switchgear and fit int the space vacated by A T switchgear Install, cmmissin and energize the new A T switchgear Crdinate with Hydr One n purchase, installatin and cmmissining f incming feeder cells and cnfiguring the new bus as wire
... Scpe f wrk in 0 Transfer lad frm the existing A T switchgear t the new A T switchgear. Decmmissin the existing A T switchgear.. Jb Cst Table : Strachan TS Csts Jb Estimate Number Jb Title Jb Year Ttal Estimated Cst ($M) Strachan TS A T switchgear 0 0. replacement preparatin Strachan TS A T switchgear 0. replacement S0 Strachan TS Lad Transfer frm A T t A T Switchgear 0 0.0
Figure : Lcatin f Strachan TS
. Carlaw TS A E.. Jb Descriptin Carlaw TS A E The bjective f this jb is t cmplete the secnd part f a tw part replacement jb f the Carlaw TS A E switchgear. The first part f this jb invlved purchasing f the switchgear in 0. The secnd part invlves cmmissining f the new switchgear and the statin lad transfer frm the existing t the new switchgear in 0. 0.. Scpe f Wrk A E Prepare drawings t cmmissin the switchgear Cmmissin and energize the new switchgear Transfer lad frm the existing A E t new A0 E switchgear Decmmissin and remve existing A E switchgear.. Jb Csts Table : Carlaw TS Csts Jb Estimate Number Jb Title Jb Year Ttal Estimated Cst ($M) 0 Carlaw TS A E switchgear 0. replacement 0
Figure : Lcatin f Carlaw TS. Wiltshire TS A W and A W Switchgear 0.. Jb Descriptin The bjective f these jbs is t design, purchase and install.kv switchgear t replace the bslete A W and A W switchgear at Wiltshire TS with 000A air insulated arc resistant type C switchgear with a breaker and half cnfiguratin in 0, and 0, respectively. Preparatin f flr space in Building A is required t accmmdate the new switchgear in place f the decmmissined switchgear.
0.. Scpe f Wrk A W Design the prpsed new A W switchgear t fit int the space that is currently ccupied by the bslete A W switchgear Prcure and purchase a new.kv, MVA, wire, air insulated, arc resistant type switchgear and replace the aging and bslete A W ( wire) switchgear Prepare the flr space where the decmmissined A W was lcated t make space fr installatin f the prpsed A W switchgear Mdify and/ r cnstruct any necessary civil infrastructures within Wiltshire statin prperty bundary t facilitate the feeder transfer frm the existing and bslete A W switchgear t the prpsed new switchgear A W Install and cmmissin the new A W switchgear Crdinate with Hydr One t prvide supprt fr relcatin f the HONI incming LV supply cables frm the existing lcatin t the new switchgear lcatin Energize and transfer lad frm the A W t the new A W switchgear Decmmissin and remve the A W switchgear 0.. Scpe f Wrk A W Design the prpsed new A W switchgear t fit int the space that is currently ccupied by the bslete A W switchgear Prepare the flr space by remving the decmmissined A W t make space fr installatin f the prpsed A W switchgear Prcure and purchase a new.kv, MVA, wire, air insulated, arc resistant type switchgear t replace the aging and bslete A W ( wire) switchgear Install and cmmissin the new A W switchgear Transfer lad frm the existing A W switchgear t the new A W switchgear Crdinate with Hydr One t prvide supprt fr relcatin f the HONI incming LV supply cables frm the existing lcatin t the new switchgear lcatin Decmmissin the A W switchgear and remve the brick structure frm Wiltshire TS
.. Jb Csts Table : Wiltshire TS Csts Jb Jb Title Jb Ttal Cst Estimate Year ($M) Number 0 Wiltshire TS A W switchgear replacement 0.0 WiltshireTS A W switchgear replacement 0. Figure : Lcatin f Wiltshire TS
. Windsr TS A WR Switchgear.. Jb Descriptin The bjective f this sjb is t replace the existing A WR switchgear at Windsr TS with 000A air insulated, arc resistant type C type switchgear with duble bus, duble breaker r breakerand half switchgear in 0. 0.. Scpe f Wrk A WR Design the prpsed new A 0WR switchgear t fit int the space that is currently ccupied by the bslete A 0WR Decmmissin and remve the A 0WR nce lad is transferred t Bremner TS Prcure new.kv, MVA, wire, air insulated arc resistant type switchgear Install and cmmissin the new A 0WR switchgear Energize the A 0WR and transfer lad frm the A WR switchgear Crdinate with Hydr One n purchase, installatin and cmmissining f incming feeder cells and cnfiguring the new bus as wire Decmmissin and remve the existing A WR switchgear in Windsr TS building.. Jb Csts 0 Table : Windsr TS Csts Jb Estimate Number Jb Title Jb Year Ttal Estimated Cst ($M) Windsr TS A WR switchgear replacement 0.
Figure : Lcatin f Windsr TS. Duplex TS A DX Switchgear.. Jb Descriptin The bjective f this jb is t design and purchase new.kv 000A gas insulated switchgear (GIS) t replace the existing A DX switchgear in 0. 0.. Scpe f Wrk A DX Design the prpsed A DX switchgear Prcure and purchase a new.kv, MVA, gas insulated switchgear Install and cmmissin the new A DX switchgear Transfer lad frm the existing A DX switchgear t the new A DX switchgear Crdinate wrk with Hydr One t migrate the HONI incming LV supply cables frm the existing switchgear t the new switchgear lcatin.
Decmmissin the A DX switchgear and remve it frm Duplex TS.. Jb Csts Table : Duplex TS Csts Jb Estimate Jb Title Jb Year Ttal Cst ($M) Number 0 Duplex TS A DX switchgear replacement 0. Figure : Lcatin f Duplex TS
III Need 0. Overview All the switchgear in this segment are nn arc resistant designs and past their useful lives. Nnarc resistant designs d nt cntain the energy released during fault cnditins. When an internal arc fault ccurs in this type f switchgear, the energy released has the ptential t damage adjacent equipment and pse ptential safety risks t persnnel wrking in the vicinity. Even thugh statin wrkers are nt present inside statins n a daily basis, they d mnthly rutine inspectins in all THESL statins and d planned maintenance and capital wrk in statins. If an internal arc fault ccurs while statin wrkers are in the vicinity there is a ptential that a wrker culd be injured. A catastrphic failure als increases the severity f cllateral damage t adjacent equipment and culd ptentially cause a cmplete statin utage. The prbability f failure cntinues t increase with time as the cnditin f the equipment cntinues t deterirate. Table prvides the impact resulting frm the failure f ne switchgear and the impact resulting frm a whle statin utage frm cllateral damage. The impact is presented in terms f lad at risk and expected duratin f utage. Table : Lad at Risk and Duratin Substatin Name Failure f One Switchgear Lad at Risk Duratin(hurs) (MVA) Failure f the Entire Substatin Lad at Risk Duratin (hurs) (MVA) Strachan TS Carlaw TS Wiltshire TS 0 0 Duplex TS Windsr TS 0 Failure f any switchgear is expected t result in extended utages given that the lading and cnditin f the ther switchgear within the statin limits the ability t pick up the lad.
Table belw includes a list f substatins in the area and the spare capacity. Table : Substatins with Spare Capacity % Rated Peak Available Name f Supprting (MVA) Lad Capacity In Statin Substatin Substatin Name Capacity (MVA) Supprting Substatin (MVA) Strachan TS Dufferin TS Carlaw TS Gerrard TS and Main TS Wiltshire TS 0 Dufferin TS Duplex TS Glengrve TS and Leaside TS Windsr TS 0 0 Terauley TS 0 In additin t being nn arc resistant design, the existing circuit breakers that are fitted in these switchgear are f air blast type (with the exceptin f Duplex), and are bslete. The maintenance fr this type f circuit breaker is labur intensive. Replacement parts fr the air blast circuit breakers are n lnger manufactured. Any parts required must be custm manufactured and are btained at high cst. The air blast system has additinal $,00 maintenance cst per year t maintain the air supply system needed fr breaker peratin. In additin t the switchgear being nn arc resistant design, past their useful lives, and fitted with bslete air blast breakers, the replacement f switchgear included in this segment is als driven by the fllwing cncerns:. Strachan TS This switchgear was installed in. Frm the Asset Cnditin Assessment ( ACA ) update reprt in 0 and 0, these switchgear were assigned a Health Index (HI) f (ut f 00) which is cnsidered in the Pr categry as per the Asset Cnditin Assessment ( ACA ) f
00. As per Kinetrics s recmmendatin, switchgear in pr categry shuld be replaced within the next three years. If the A T switchgear fails MVA f lad will be lst 0. Carlaw TS The A E switchgear was installed in. Frm the Asset Cnditin Assessment ( ACA ) update reprt in 00, the A E switchgear has a (ut f 00) which is cnsidered as pr categry. As per Kinetrics s recmmendatin, switchgear in pr categry shuld be replaced within the next three years. The basic design f the switchgear is an pen brick structure. This design pses safety cncerns. While cntrls and PPE are in place t address risk, nnetheless, the nature f the equipment requires that during maintenance persnnel are expsed t live high vltage parts f the switchgear. During peratin, persnnel must stand clear since there is n barrier between them and the high vltage equipment. Unlike ther types f switchgear such as metal clad switchgear where the different parts f the switchgear are lcated inside a metal enclsure and are perated frm utside f the enclsure, the switchgear in an pen brick structure has t be pened first while it is live and then perated as shwn in Figure belw.
Figure : Carlaw TS.kV live parts f a switchgear in an pen brick structure If the A E switchgear fails MVA f lad will be lst. 0. Wiltshire TS The existing Wiltshire TS A W and A W switchgear were installed in. Frm the Asset Cnditin Assessment ( ACA ) update reprt in 0, these switchgear were assigned a Health Index (HI) f 0 and (ut f 00) respectively which is cnsidered in the Pr categry, which means they require replacement within three years. These switchgear are als in an pen brick structure with similar limitatins t thse at Carlaw TS. The Wiltshire TS switchgear supplies a large pumping statin, which is a critical custmer. If the A W r A W switchgear fails, MVA and 0 MVA lad will be lst, respectively. 0
. Duplex TS In additin t the age f the switchgear, there is additinal risk f the basement being flded with water frm the Hydr One deluge system which is lcated n the main flr abve the switchgear. T mitigate this risk, and t address the aging issue f the switchgear, THESL plans t replace in stages all the switchgear at Duplex TS which are lcated in the basement with water resistant, gas insulated switchgear (GIS). The A DX switchgear is the first t be replaced. If the A DX switchgear fails, MVA f lad will be lst. 0. Windsr TS The A WR switchgear was installed in. Frm the Asset Cnditin Assessment ( ACA ) update reprt in 0, Windsr TS A WR switchgear was assigned a Health Index (HI) f 0 (ut f 00) which is cnsidered in the Pr categry, and it needs replacement within three years. The Windsr TS switchgear supprts the financial district, which includes many large custmers. If the A WR switchgear fails, MVA f lad will be lst.
IV Preferred Alternative THESL cnsidered three alternatives: Cntinue t Maintain and Operate the Existing Equipment; Transfer lad t adjacent statins; and Replace the existing switchgear with arc resistant design. 0. Optin : Cntinue t Maintain and Operate the Existing Equipment This ptin is essentially a run t failure scenari with replacement f existing switchgear when failure ccurs. This ptin will defer capital investment but cntinuus repair f the switchgear will be required as it will cntinue t deterirate. This ptin is expected t result in: Decreased system reliability. N mitigatin f ptential safety risks t THESL persnnel Increased maintenance and perating csts Increased system reliability risk Increase risk f damaging equipment in the surrunding area in an eventful failure. It is estimated that replacement f switchgear under emergency cnditins versus planned equipment replacement will increase the csts by at least 0%. 0 0. Optin : Transfer Lad t Adjacent Statins Transferring lad frm the switchgear planned t be replaced t ther switchgear in the vicinity and decmmissin these switchgear was cnsidered. This ptin wuld defer mst f the capital investment required, if feasible. Fr this ptin t be feasible, fur cnditins need t be met: (a) The supprting switchgear must have spare capacity t take additinal lad. This cnditin cannt be met because there is nt enugh capacity at the receiving statins t accmmdate the required lad transfer. The receiving statins wuld be verladed when lad is transferred r will reach capacity shrtly as lad grws as shwn in Tables and belw.
0 (b) The supprting switchgear must have enugh feeder psitins t accept the transferred feeders. This cnditin cannt be met fr all f the switchgear prpsed t be replaced. As shwn in Table, Gerrard TS, Main TS, and Terauley TS dn t have enugh spare feeder psitins t transfer lad frm Carlaw and Windsr TS, respectively. There are enugh feeder psitins in the receiving statins fr the rest f the switchgear prpsed t be replaced. Hwever, as discussed in the previus paragraph (a), there is insufficient available capacity in the receiving statins. (c) Physical space fr undergrund infrastructure must be available if lad is t be transferred t anther statin. THESL shares undergrund space with ther utilities such as Enbridge, Bell, Rgers, and Water and Sewer. Finding space t build undergrund infrastructure in rder t install cables t transfer the lad is challenging. (d) Vltage drp prblem des nt ccur as a result f lad transfer t neighbring statin. This cnditin cannt be met as the supplying statin will be far frm the lad center and vltage drp will be a prblem. Table : Switchgear Lad Transfer t switchgear within statin Switchgear t be Cnnected Lad t be % Lading at the Decmmissined Custmers transferred(mva) Receiving Statin(s) After Lad transfer Strachan TS A switchgear,0 Carlaw TS A E switchgear, 0 Wiltshire TS A W switchgear, Duplex TS A DX switchgear,0 Wiltshire TS A W switchgear 0, 0 00 Windsr TS A WR switchgear.
Table : Switchgear Lad Transfer t Neighbring Statin(s) Switchgear T be Lad t be Lad t be Cmbined Statins Decmmissined transferred (MVA) transferred t Percentage (%) Lading After Lad transferred Strachan TS A Dufferin TS 0 switchgear Carlaw TS A E switchgear Wiltshire TS A W switchgear Duplex TS A DX switchgear Wiltshire TS A W switchgear Gerrard TS, Main TS Dufferin TS, Bridgeman TS, Glengrve TS, Leaside TS, 0 Dufferin TS, Bridgeman TS 0 Windsr TS A WR Terauley TS 0 switchgear
Table : Number f feeder psitins required and available Switchgear Lad t be Number f Statin lad t be Number f available transferred frm feeders t be transferred t spare feeder psitins transferred Strachan TS A T switchgear Dufferin TS 0 Carlaw TS A E switchgear Gerrard TS and Wiltshire TS A W switchgear Main TS 0 Dufferin TS and Bridgemen TS Duplex TS A DX switchgear Glengrve TS and Wiltshire TS A W switchgear Leaside TS Dufferin TS and Bridgemen TS Windsr TS A WR Terauley TS switchgear 0. Optin : Replace the Existing Switchgear with Arc Resistant Design with Vacuum Breakers Replace existing switchgear with air insulated, arc resistant switchgear r gas insulated switchgear (GIS) with duble bus duble breaker r breaker and half cnfiguratin is recmmended. This ptin requires capital investment t replace the switchgear and is expected t: Mitigate the safety risk t the perating persnnel f THESL due t the arc resistant design f the switchgear. Arc resistant switchgear cntains the pressure due t internal arc fault and channels the energy thrugh the vents lcated n tp f switchgear. This is expected t mitigate the safety risk t persnnel and damage t equipment in the vicinity including causing utage t the whle statin. Minimize the maintenance and perating cst since the new switchgear will eliminate the air blast circuit breakers alng with the air supply system (air cmpressrs) whse
maintenance cst is at least twice that f mdern vacuum circuit breakers. The cnfiguratin f the switchgear will als be duble bus duble breaker r breaker and half and this type f cnfiguratin cuts the maintenance and perating time at least by half. Therefre, the verall maintenance and perating cst will be reduced. Increase reliability because switchgear that is arc resistant with duble bus duble breaker r breaker and half cnfiguratin is mre reliable. Unlike in the existing switchgear, any circuit breaker may be taken ut f service withut requiring lad t be transferred. 0 THESL cnsidered the fllwing five bus cnfiguratins fr this replacement ptin:.. Single bus Lwest cst Failure f bus r any circuit breaker results in shutdwn f entire statin Difficult t d any maintenance withut shutting dwn statin.. Duble bus, duble breaker 0 Has flexibility in permitting feeder circuit t be cnnected t either bus Either f the main buses can be taken ut f service at any time fr maintenance All switching is dne remtely Bus failure des nt remve any feeder circuits frm service High reliability, circuit is supplied frm either bus and circuit breaker Easier circuit breaker maintenance; any breaker can be taken ut f service fr maintenance withut interrupting the lad f a circuit. Mst expensive, each circuit has tw dedicated breakers.. Duble bus, single breaker Lw initial cst Switching is smewhat cmplicated Less flexible, failure f either the tie breaker r bus results in the switchgear ut f service Bus tie breaker failure takes entire statin ut f service 0.. Ring bus Lw initial cst
Flexible peratin during circuit maintenance, any breaker can be taken ut f service withut interrupting lad Each circuit requires ne circuit breaker Autmatic reclsing and prtective relaying circuitry is rather cmplex Fault in ne circuit takes tw breakers ut f service.. Breaker and a half 0 Mst flexible High reliability peratin Breaker and half per circuit All switching is dne remtely using circuit breakers Simple peratin Either main bus can be taken ut f service at any time Bus failure des nt remve any feeder circuits frm service Breaker failure f bus side remves nly ne circuit Breaker can be taken ut f service withut discnnecting lad 0 The tw types f bus cnfiguratins that are preferred are duble bus duble breaker and breaker and half cnfiguratins in rder t btain high reliability and flexibility in the heavily laded dwntwn area. Breaker and half cnfiguratin is hwever, preferable if existing circuits can be cnnected in a back t back setting, but this is nt always pssible in an existing statin with multiple switchgear. The egress f the feeders may make it difficult t rerute feeder cables t cnnect them back t back s switchgear cnfiguratin will be selected depending n the site. As such, the site specific cnditins dictate the bus architecture. 0.. Avided Risk Cst The recent Dufferin transfrmer statin utage in 00 assciated with a failed water deluge system prvides insight int ptential reliability impacts assciated with a cmplete statin utage. Ttal peak lad fr Dufferin TS n January, 00 was MW. In that case,, custmers were interrupted (CI) and withut service fr ver hurs resulting in,,0 custmer minutes f utage (CMO).
The anticipated effectiveness f the Switchgear TS replacement segment can be highlighted by determining hw much cst is avided by executing this wrk immediately as ppsed t executing in 0 as explained in the Business Case Evaluatin fund in Appendix. These avided csts include quantified risks, taking int accunt the assets prbability f failure, and multiplying this with varius direct and indirect cst attributes assciated with in service asset failures, including the csts f custmer interruptins, emergency repairs and replacement. 0 Carrying ut immediate wrk n this asset class is expected t result in the avided estimated risk cst f apprximately $ millin, as ppsed t executing this wrk in 0. Therefre, there are ecnmic benefits t ratepayers fr executing this wrk nw. As a practical matter given available resurces, jbs are scheduled ver three years t allw engineering, prcurement, cnstructin and cmmissining and are clsely crdinated with feeder transfers t minimize custmer utages and limit single supply cntingency. 0. Preferred Alternative Based n a cmparisn f the alternatives, replacement f existing switchgear is the preferred ptin based n reduced utage risk, technical viability and because it is the mst cst effective ptin.
Appendix Statins Switchgear TS Business Case Evaluatin (BCE) Prcess 0 The business case evaluatin (BCE) prcess invlves the calculatin f the net benefit f a capital jb and incrprates quantified estimated risk, which is calculated based upn the assets prbability and impact f failure. The prbability f asset failure is determined based upn the asset s age and cnditin. The impact f asset failure is derived based upn the varius direct and indirect cst attributes assciated with in service asset failures, including the csts f custmer interruptins, emergency repairs and replacement. The multiplicatin f the prbability and impact f asset failure respectively prvides the quantified estimated risk f asset failure.. Life Cycle Cst and Optimal Interventin Timing Results 0 Calculatin f the prbability f failure relies n the assets Hazard Distributin Functin ( HDF ), which represents a cnditinal prbability f an asset failing frm the remaining ppulatin that has survived up till that time. These functins are validated either directly by THESL r thrugh the assistance f asset life studies frm third party cnsultants. The impacts f failure are then quantified by accunting fr the direct csts assciated with the materials and labur required t replace an asset upn failure, as well as the indirect csts. These indirect csts wuld include the csts f custmer interruptins, emergency repairs and asset replacements. The final estimated risk cst is prduced that represents the prduct f a hazard rate functin fr the given asset and its crrespnding impact csts. Lastly, as shwn in Figure, the lifecycle cst is prduced, representing the ttal perating csts fr a new asset, taking int accunt the annualized risk and capital ver its entire lifecycle. The ptimal interventin time wuld then be the red marker at which the Equivalent Annualized Cst ( EAC ) is at its lwest.
New Asset Ttal Csts ($) Annualized Risk Cst Annualized Capital Cst Life Cycle Cst EAC 0 0 0 0 0 Age (years) Figure : Typical Example f Optimal Interventin Time (New Assets) This EAC value frm the lifecycle cst curve wuld then need t be crss referenced against the ttal csts f the existing asset t determine ptimal replacement timing, as shwn by the green marker in Figure. This specific pint in time wuld indicate that the existing asset has reached its ecnmic end f life at years f age and requires interventin. Nte that fr the existing asset, there is n capital cst cmpnent, as this is a sunk cst. Therefre, the existing asset csts are cmprised exclusively f the estimated risks that are remaining. 0
Ttal Csts ($) New Asset Existing Asset Ttal Csts ($) years 0 0 0 0 0 0 0 0 0 0 Age (years) Age (years) Annualized Risk Cst Annualized Capital Cst Life Cycle Cst EAC Risk Cst (Existing Asset) Optimal Interventin Time Figure : Typical Example f Optimal Interventin Time (Existing Assets) Nte that fr the example in Figure, shuld the asset be replaced prir t the year ptimal interventin time, this wuld represent a sacrificed life t the asset. Shuld the asset be replaced after the ptimal interventin time, this wuld represent an excess estimated risk.. Prject Evaluatin Results 0 The Statins Switchgear TS segment represents an in kind replacement prject in which the existing switchgear assets are being replaced with new standardized versins f thse assets, hwever the verall cnfiguratin assciated with this infrastructure remains the same. In kind prjects are evaluated by calculating the avided estimated risk cst f executing the prject immediately in 0 as ppsed t delaying it. Within the ICM applicatin, the deferral time has been set t 0, as this wuld represent the next available year when THESL may file a new Cst f Service EDR applicatin. In rder t calculate the avided estimated risk cst f perfrming a prject in 0 as ppsed t 0, the varius csts and benefits assciated with executing a prject in a particular year is taken int accunt. 0 When a prject analysis is undertaken, assets within the prject may be befre, at, r beynd their ptimal replacement time, thus sme assets will have sacrificed ecnmic life and thers
will have incurred excess risk. The cumulative sacrificed life and excess risk f the assets invlved becmes a cst against the prject, as shwn by the red curve in Figure. There may be benefits achieved by perfrming multiple asset replacements tgether as part f a linear prject, and typically these benefits wuld be weighed against the ttal csts in rder t prduce an verall prject net cst calculatin. Hwever, in this instance, the Statins Switchgear TS segment cnsists f targeted asset replacements being perfrmed acrss the City f Trnt, and therefre these benefits wuld nt be applicable. Therefre, the ttal Prject Net Cst is directly prprtinal t the ttal csts including sacrificed life and excess risk. 0 Nte that the Prject Net Cst in Figure is pltted with time, in years, as the abscissa and the ttal csts as the rdinate. As such, the minimum pint f this curve prvides the highest Net Prject Benefit and defines the ptimal year t execute the specific prject. Figure : Typical Example f Prject Net Benefit Analysis
The effectiveness f the Statins Switchgear TS prject can therefre be measured by calculating the ttal avided estimated risk cst f executing this wrk immediately in 0, as ppsed t waiting until 0. In rder t calculate the avided estimated risk cst, the Prject Net Cst in 0 is subtracted frm the present value f the Prject Net Cst frm 0. An example f this avided estimated risk cst is shaded in blue in Figure. 0 Since the ptimal year is the lwest pint n the graph in Figure, it means that estimated risk csts fr the prject assets in 0 will exceed the estimated risks that exist tday. By perfrming the wrk immediately as ppsed t waiting until 0, THESL can eliminate these estimated risks. Therefre, these avided csts represent the benefits f the in kind prject executin. The frmula fr this calculatin is detailed belw: Avided Estimated Cst = PV(PROJECT NET_COST (0)) PROJECT NET_COST (0) Where: PROJECT NET_COST (0): Represents the ttal prject net csts in 0. 0 PV(PROJECT NET_COST (0)): Represents the present value f ttal prject net csts in 0. Within the TS Switchgear segment, individual ptimal interventin timing results were calculated fr each f the switchgear TS assets, based upn the prcesses identified in Sectin.. Each f these assets may pssess an individual sacrificed life and an excess risk value, which are aggregated t prduce the verall Prject Net Cst year by year. 0 As nted in the frmula abve, this Prject Net Cst was then calculated fr all individual switchgear assets within this prject at years 0 and 0 respectively. Prject Net Csts quantified in 0 were brught back t a present value and the difference between this value and the Prject Net Cst quantified in 0 was taken as the Avided Estimated Risk Cst. The final results are prvided in Table belw:
Table : Summary f values used in the determinatin f Avided Estimated Risk Cst Business Case Element Estimated Cst (in Millins) Present Value f Prject Net Cst in 0 (PV(PROJECT NET_COST (0)) $. Prject Net Cst in 0 (PROJECT NET_COST (0)) $ 0.0 Avided Estimated Risk Cst = $.0 (PV(PROJECT NET_COST (0)) PROJECT NET_COST (0)) When this avided estimated risk cst is calculated as a psitive value, it means that estimated risk csts fr the jb assets in 0 will exceed the estimated risks that exist tday. By perfrming the wrk immediately as ppsed t waiting until 0, we can eliminate these estimated risks. Therefre, these avided estimated risk csts represent the benefits f jb executin.