Transmission Line Design Standard

Transcription

1 Transmissin Line Design Standard Summary This standard defines the perfrmance design parameters fr verhead transmissin lines cnstructed t cnnect t and frm part f the TransGrid netwrk. TransGrid publishes this infrmatin under clause 5.2A.5 f the Natinal Electricity Rules. Dcument Cntrl Date f issue July 2018 Update Initial versin Disclaimer and imprtant ntice This dcument and the infrmatin in it is fr general guidance nly and may be subsequently updated r amended. This dcument des nt cnstitute technical r ther prfessinal advice, and shuld nt be relied n as a substitute fr btaining detailed technical and prfessinal advice abut its subject matter. T the maximum extent permitted by law, TranGrid and its fficers, emplyees and cnsultants invlved in the preparatin f this dcument: make n representatin r warranty, express r implied, as t the currency, accuracy, reliability r cmpleteness f the infrmatin in this dcument are nt liable (whether by reasn f negligence r therwise) fr any statements r representatins in this dcument, r any missins frm it, r fr any use r reliance n the infrmatin in it. 1 Transmissin Line Design Standard

2 Cntents 1. Purpse Scpe Objectives Definitins Acrnyms and Abbreviatins General Design parameters Safety in design Design drawings Operatinal Requirements Electrical Design Insulatin Electrical clearances Clearance t grund and rads Clearance t structures Maintenance clearances Transpsitins Earthing Earthing metalwrk Fting resistance Earthing safety Electric and magnetic fields Inductin Vibratin Structural Design General requirement Ladings Structure and design Fting design Prttype and testing Fauna cnsideratin Transmissin Line Design Standard

3 1. Purpse This standard fr Transmissin Line Design specifies the minimum structural, electrical and getechnical design required fr verhead transmissin lines used in TransGrid s netwrk. This standard cmplies with AS/NZS 7000 and any exceptins are explicitly nted. 2. Scpe This standard specifies the requirements that shall be met fr the design f new twers, ples r similar structures that supprt the cnductr f TransGrid verhead transmissin lines. This standard is nt intended as a substitute fr AS/NZS 7000 r ther Regulatry Standards, Cdes r Acts. Every effrt has been made t ensure that this standard cmplies with AS/NZS 7000 except where explicitly stated, hwever it remains the users respnsibility t ensure that all relevant regulatry requirements are satisfied, particularly where recent amendments have been made. 3. Objectives TransGrid requires wrks t be carried ut in accrdance with this standard t ensure: That relevant Australian legal requirements are met That the requirements f the Natinal Electricity Rules are met Persnnel and public safety Safety f TransGrid s assets Ease in peratin and maintenance Reliability and cntinuity f pwer supply frm the pwer transmissin netwrk Minimum disruptin t the pwer supply system fllwing a fault Alignment with TransGrid s netwrk management strategies and TransGrid s established maintenance practices That the expsure f TransGrid s business t risk is minimised. 4. Definitins The meanings and interpretatins f terms and phrases used in this dcument are as listed belw. Term Cnductr Span Suspensin Structure Tensin Structure Terminatin (Dead- Definitin This is generally a reference t the phase cnductrs n a transmissin line but is als a generic term fr the uninsulated cables that are used fr either phase cnductr r verhead earthwire. The hrizntal distance between tw adjacent structures. A structure that primarily supprts the transverse and vertical lad f the cnductrs and is subject t minimal lngitudinal lad. The cnductr is supprted by insulatin that is usually perpendicular t the cnductr. Insulatr types include I string, D string, V string, hrizntal V, line pst, braced line pst. A structure where the cnductrs are terminated with insulatrs in-line with the cnductr and supprts lngitudinal cnductr lads in additin t the transverse and vertical lads. The structure is incapable f resisting terminatin lads n ne face f the structure alne. A tensin structure that is capable f resisting terminated cnductr lads n ne face f 3 Transmissin Line Design Standard

4 end) Structure the structure. 5. Acrnyms and Abbreviatins Term ALS CBL EDMS EMF ICNIRP MOT OHEW OPGW RMS RSL SC/AC SC/GZ SVD SWP TAMIS TLS VAR Definitin Aerial Laser Survey Calculated Breaking Lad (kn) Electrnic Dcument Management System Electrmagnetic Field Internatinal Cmmissin n Nn-Inising Radiatin Prtectin Maximum Operating Temperature Overhead Earth Wire Optical Fibre Grund Wire Rt mean square Residual Static Lad (kn) Steel Cnductr/Aluminium Clad Steel Cnductr/Galvanized Spiral vibratin damper r impact damper Standard Wrk Practices TransGrid Asset Management Infrmatin System Terrestrial Laser Survey Reactive r apparent pwer (vlt ampere reactive) 6. General 6.1 Design parameters The design scpe shall include cnsideratin f the fllwing inputs: Apprved line rute and rute length Climatic cnditins (wind regin, wind speed, wind directin, temperatures, lightning grund flash density) Seismic cnditins (if they apply) Tpgraphical features (terrain categry, altitude) Pllutin level Envirnmental and cultural heritage requirements Operating vltage Number f circuits Cnductr type and size Overhead earthwire type and size 4 Transmissin Line Design Standard

5 Optical Fibre Overhead earthwire (if applicable) Structure type Line imprtance Security Level Design wrking life fr the line Lightning perfrmance requirements OPGW requirements Details f the cnnectin r terminal pints f the line Maximum lad Earth fault level at terminal substatins Cnstructin issues such as: Outage restrictins and recall times Overcrssings, undercrssings and traffic management Cnstructin staging if required Inductin frm parallel transmissin lines 6.2 Safety in design Designs shall be in accrdance with the Safe Wrk Australia Safe Design f Structures Cde f Practice. 6.3 Design drawings Where required design drawings fr cnstructin shall include the fllwing: Plan & prfile drawings. These shall include cnductr type, maximum design temperature and the minimum clearance prvisin Line schedules shall be in a tabulated frmat, summarising the details f the line Stringing/sagging tables (including ffset clipping if applicable) Vibratin damper schedule and installatin dimensins Cnstructin staking tables Structure drawings (if utilising nn-standard structures) Rail crssing drawings (if applicable) Other pwerline crssing drawings (if applicable) Navigable waterway crssing drawings (if applicable) Landing span drawings fr nn-standard structures General arrangement Steelwrk fabricatin details Ple manufacturing details Insulatr and earthwire arrangements and details Electrical clearances Design lading capacity with lad factrs Structure test reprts 5 Transmissin Line Design Standard

6 7. Operatinal Requirements The fllwing issues shall be addressed in the transmissin line design t ensure that the line meets the peratin requirements f the TransGrid netwrk: Structure security is required t limit the cnsequential damage in the event f a structural failure and particularly t reduce the risk f cascade failures Netwrk Reliability shuld be maximised fr all transmissin line designs thrugh all aspects f cnstructin, peratin and maintenance Thermal Rating phase cnductrs and maximum perating temperature shall be selected t minimise annealing and maximise cnductr life. All lines shall maintain statutry grund clearances at the maximum design perating temperature Fault Currents current, future and ultimate fault levels shuld be cnsidered in the selectin f cnductrs and earthwires t ensure they are adequately rated Lightning Perfrmance - The lightning perfrmance f a transmissin line shall be managed thrugh cntrl f earthwire shielding angle, structure earth resistance and insulatin level t achieve the lightning utage rates shwn in the table belw: Line Vltage Radial Lines Parallel Lines Each Circuit Duble Circuit Each Circuit Duble Circuit 500 kv kv kv kv kv Table 1: Design Lightning Outage Rates (utages/100 kilmetre/year) 6 Transmissin Line Design Standard

7 Easement Widths are sized t ensure standard safety clearances under high wind cnditins, prvide an area where vegetatin heights can be cntrlled and prvide ease f access fr nging maintenance and repairs. Easements shall be acquired fr all transmissin lines n private land accrding t the table f minimum easement widths belw: Table 2: Easement widths Transmissin Line 500kV duble circuit 500kV single circuit 330kV single r duble circuit 220kV single r duble circuit 132kV single r duble circuit 66kV single r duble circuit Up t 33kV single r duble circuit Easement Width 70m 80m 60m 50m 45m 30m 20m Required Clearances Arund Structures - The fllwing are the minimum requirements t prvide fr a safe wrk area arund each type f structure: 15m frm any crssing pwer line structure r cnductrs 15m t any rad carriageway, r barricade utside the edge f the carriageway 15m t the prperty bundary f any rail crridr Cnsideratin f cnductr blwut twards structures t maintain safe electrical clearances All parts f structures and cnductrs f any parallel electricity line t be utside the easement, verlapping easements are acceptable 8. Electrical Design 8.1 Insulatin Insulatin c-rdinatin shall be in accrdance with AS Electrical clearances Clearance t grund and rads Minimum Clearance t grund and ver the carriageway f rads fr new transmissin lines shall be in accrdance with AS/NZS Als when designing a new line, the fllwing cnsideratins shuld be given t fr additinal clearances: Include a margin t allw fr minr inaccuracy in surveying and cnstructin, as well as sme small mvement ver time Additinal clearance shuld be allwed if there is likely t be a future lwer circuit cnstructed alng the rad r in special circumstances such as private rads and adjacent parts f public rads especially in mining and heavy industrial sites Greater clearances ver rads may be required where regular high lads are likely (Natinal and State Highways and ther majr rads) and t allw fr vehicle maintenance r breakdwn activities (a persn n tp f the vehicle) which are nt allwed fr in the standard clearances. 7 Transmissin Line Design Standard

8 8.2.2 Clearance t structures Clearance t structures fr cnductrs and insulatr arrangements shall be shall be designed in accrdance with AS/NZS Maintenance clearances All structure designs shall prvide climbing access. On multiple circuit structures r line crridrs, access shall be available t ne circuit with the ther circuit(s) live. 8.3 Transpsitins Phase cnductrs are transpsed n lng transmissin lines t balance the mutual impedances and reduce the lad current unbalance. Transpsitins are usually nt required in 500kV lines r 330kV lines less than 100km in length. Where required, they will be specified by TransGrid. Fr lines less than 50km transpsitin is nt usually required. Fr lines greater than 50km, cnsultatin with TransGrid is required regarding the pssible need fr a transpsitin. 8.4 Earthing Earthing metalwrk In general all metallic ple fittings such as crss-arms, insulatr bases and ple bands shall be bnded t the structure earthing system. Step blts are nt required t be earthed Fting resistance The design structure fting resistance r structure earth resistance shall be determined based n the lightning perfrmance requirements f the transmissin line Earthing safety Where structures are lcated in public places and are deemed t have a high expsure t persns making frequent cntact r being in clse prximity fr extended perids, the step and tuch ptentials at the structure shuld be assessed in accrdance with AS/NZS Where step and tuch ptentials are fund t be nn-cmpliant, apprpriate remediatin shuld be determined and implemented as part f the design. 8.5 Electric and magnetic fields Electric and magnetic fields attributable t the transmissin line shall be in accrdance with the ICNIRP Guidelines Fr Limiting Expsure T Time-Varying Electric and Magnetic Fields (1Hz 100kHz). 8.6 Inductin Magnetic fields due t lad r fault current can cuple with nearby cnductive infrastructure t prduce hazardus vltages, particularly where the structure is lng, parallel and clse t the transmissin line. Metallic pipelines, pwer lines, metallic fences, cnveyr belts and cpper telecmmunicatin lines are typical examples. The risk and mitigatin measures shall be assessed in accrdance with AS 4853 r HB 102. Fences n the easement shuld generally be dealt with during cnstructin accrding t the TransGrid Fencing Guideline. 8.7 Vibratin Where a cnductr, earthwire r OPGW is strung at a tensin in excess f the limits f AS/NZS 7000 vibratin dampers shall be installed t limit fatigue. 8 Transmissin Line Design Standard

9 9. Structural Design 9.1 General requirement The mechanical and structural design shall ensure that the line perfrmance will cmply with all relevant Natinal and State Legislatin, that the line can be readily cnstructed and maintained using standard industry practices and tls, and that rutine maintenance can be carried ut withut lss f supply. The design shall ensure premature failure f cmpnents des nt ccur frm fatigue stresses, abrasin r crrsin r ther serviceability cnditins that will be encuntered within the design perating parameters fr the line. Design f structures and fting shall meet the requirements specified in in AS7000 t ensure that the line is suitable fr its intended purpse and t ensure acceptable levels f safety fr cnstructin, maintenance and peratin. Apprpriate security level shall be determined cnsidering the imprtance f line, impact n TransGrid netwrk reliability, its lcatin, climate cnditin, public safety and design wrking life in cnsultatin with TransGrid unless advised therwise by TransGrid. 9.2 Ladings Structures shall be designed t meet the lading requirements specified in AS/NZS7000 as the minimum including, but nt limited t, the fllwing lad cases: Wind lads shall be calculated in accrdance with AS and AS/NZS 7000 in cnjunctin with ther relevant Australian cdes and standards t achieve system security levels required Where lines f significant length crssver wind regins, the apprpriate regin can be applied t each respective sectin, hwever any change in wind pressure alng the line shuld be dne at a terminatin structure, with the higher wind pressure applied t the structure itself 9.3 Structure and design Structure design shall cmply with the requirements specified in AS/NZS 7000, AS 3995, ASCE standards and ther referenced cdes and standards as applicable unless advised by TransGrid. Where lad relief is prvided by failure f steelwrk, it shuld be in a ductile manner, whereby energy is absrbed by the plastic defrmatin f cmpnents. 9.4 Fting design Fting design shall cmply with the requirements specified in AS/NZS 7000 and in accrdance with AS 3600, AS 2159 and ther referenced cdes and standards as applicable. The fundatin shall be designed fr all sil strength cnditins likely t be experienced ver the design life f the line due t effects such as a fall r rise in the water table (including flding) and ersin f nearby sil. The effect f lng term and shrt term lad cnditins n sil strength shuld als be cnsidered Getechnical investigatin shall be carried ut t determine the sil parameters fr design f ftings. 9.5 Prttype and testing All structures shall be prttyped t ensure that fabricatin is as per design and t meet the quality requirements specified n drawings and specificatins. Generally all new designs shuld be lad tested. The decisin t lad test structures shuld be made by the design engineer, taking int accunt the fllwing factrs: Similarity f existing designs and design principles Quantity f structures t be used, including cnsideratin shuld be given t their utilisatin n future lines Cnfidence in the adequacy f the design 9 Transmissin Line Design Standard

10 Cst f testing The lad testing shall cnfirm the verall strength f the structure as well as the strength crdinatin between cmpnents. 9.6 Fauna cnsideratin All structures shuld be designed t be bird & vermin prf, including maintenance platfrm prtectin (minimise access). Cnsideratin is t be given t minimising the impact n lcal fauna, such as bird diverters n cnductrs/earthwires and fauna safe anti-climbers where particular species f cncern are nted. Stck have been knwn t get stuck in between twer leg members, als damage has ccurred t structures frm rubbing n guys etc. 10 Transmissin Line Design Standard