6.9 Undergrund Cables Purpse This instructin utlines the safe apprach distances (SADs) that must be maintained and the wrking requirements fr undergrund cables. Scpe This instructin utlining the safe apprach distances fr undergrund cables, that applies t all Hrizn Pwer Wrkers, including Wrkers perating, servicing, and/ r maintaining (MPS) Micr Pwer Systems electrical equipment (inclusive f all generating methdlgies) Safety Befre cmmencement f wrk, a risk assessment must be carried ut using the Risk Analysis Prcedure (OSH-3.6-1-02), t identify and dcument the hazards and risks assciated with the task and ensure apprpriate cntrl measures are implemented. It is imprtant that, apprpriate cntrl measures must be identified, dcumented and implemented in rder t cntrl hazards t As Lw as Reasnable Practicable (ALARP). Instructin Befre ding machine excavatin wrk near live high vltage (HV) apparatus: a Vicinity Authrity (VA) must be btained Aut-reclsing devices must be disabled, if present. D nt tuch live cables unless the cable has a sund earthed sheath. Cvers laid fr mechanical prtectin f cables must always be remved by hand. Blasting D nt blast within 30 m f any live buried cable. Expsed Undergrund Cables D nt leave live cables in excavatins unattended r accessible by the public. D nt mve cable jints during excavatin as this may damage the jint itself and endanger the wrk team. When a jined cable has been de-energised and mved, cnfirm jint integrity befre reenergising by ding an insulatin test. Use a rigid, nn-cnductive supprt, t supprt cables acrss penings greater than 2 m. The supprt must nt damage the uter sheath f the cable r cnduit. Live cables that are suspended acrss penings must be cvered with nncnductive material t prevent them frm being accidentally cntacted. Where cnduits and ducts are expsed acrss pen excavatins greater than 2 m, supprt them t prevent any mvement, misalignment, r damage. CS# 2244623 FI 6.9 Undergrund Cables Page 1 f 6
Table 1, belw, prvides the SADs abve and beside undergrund cables. Care must be taken at all times nt t make cntact with the undergrund cables. If damage ccurs, it must be immediately reprted t the Hrizn Pwers fault centre n 13 23 51. A Hrizn Pwer representative must supervise any excavatin wrk that will disturb the sil beneath undergrund cables that may pssibly allw them t becme unsupprted and unprtected. Table 1 Safe Apprach Distances t Undergrund Cables Nminal Vltage Safe apprach Distance (mm) Pwered Tl r Plant Un-pwered Hand Tl r Persns Up t and including 1,000 V 300 mm Avid cntact 1,000 V up t and including 33 kv 500 mm Avid cntact Greater than 33 kv up t and including 132 kv 3,000 mm Avid cntact Nte: Pwered excavatin tls/machinery may nt be used at distances any clser than indicated in the Table abve. Only unpwered excavating hand tls can be used at clser distances. Vacuum extractin is acceptable. Fr cables f 33 kv and abve: A Hrizn Pwer representative must supervise the wrks Pt-hling must first have identified the relevant cables. Mving Live Cables Never mve live HV cables When mving cables, d nt reduce the manufacturer s stated minimum bending radius. Care must be taken when mving cnduits cntaining live cables, t ensure the cnduit is nt discnnected r bent. Only mve HV XLPE cables (less than 66 kv) if the cable sheaths are undamaged and cmplete and at earth ptential and the cable is prved de-energised. A separate risk assessment must be perfrmed fr the task. Only mve HV and lw vltage (LV) paper lead cables/cnsac if the cable is undamaged and the cable is prved de-energised. A separate risk assessment must be perfrmed fr the task. Only mve live LV cables when: a separate risk assessment has been perfrmed fr the task the cable sheath is in gd cnditin and at earth ptential CS# 2244623 FI 6.9 Undergrund Cables Page 2 f 6
the cable is either Wavecn, 25 mm, fur-cre XLPE, 10 mm r 16 mm streetlight cable Placing new cables int a trench with existing live cables A safety bserver must be present during these wrks. Carry ut a risk assessment befre installatin. Prtect existing cables against damage. Cnduit Cutting When lcating cables enclsed in cnduits and cutting pen the cnduits t access either HV r LV cables, the fllwing must be dne. 1. Obtain recrds f cable lcatins using Dial befre Yu Dig and Gegraphic Infrmatin Systems (GIS).. Cmplete a risk assessment. 3. Wear PPE in accrdance with field instructin 2.6 (Wrksite Clthing and Persnal Prtective Requirements) in this manual. 4. The identified cable must be de-energised and earthed if HV r LV, unless LV live jinting is necessary. 5. Obtain an Electrical Access Permit (EAP). 6. Use an electrnic cable lcatr with separate transmitter while trenching t lcate the cable enclsed within a cnduit. 7. Where the cnduit is gruped with ther cnduits, cnfirm that the crrect cnduit has been selected by using an apprved cable identity tl, fr example: frequency cable identity tl with transmitter SEBA KMT with transmitter and receiver lp. 8. Cut a suitable viewing hle in the tp f the cnduit t release any water inside and help determine the number f cables inside. T d this safely: a. use a battery-pwered drill and Harn 35 mm bring bit t bre a hle f 1-2 mm depth b. replace the Harn bit with a 35 mm hle saw bit but with the central drill bit remved c. cnsult the chart belw t determine the cnduit wall thickness then fit a hse clamp arund the hle saw t ensure that the drill depth des nt fully penetrate the cnduit wall d. using the circle bred by the Harn bit as a guide, cut a hle in the cnduit wall, leaving a thin plastic skin e. use a hammer t break the thin plastic skin and remve the sectin f cnduit. Nte: The cutting depth in the cnduits shuld be less than the wall thickness in rder t leave a thin plastic skin. The table belw shw the apprximate wall thickness f cmmnly used cnduits. CS# 2244623 FI 6.9 Undergrund Cables Page 3 f 6
Table 2 - Apprximate Wall Thickness f Cmmnly Used Cnduits SIZE HD cnduit size (OD in mm) 50 63 89 114 140 160 THICKNESS Apprx wall thickness (mm) 3.4 3.9 4.6 5.9 7.2 8.3 COIL HDPE cnduit cil (OD in mm) 63 110 125 140 180 226 THICKNESS Apprx wall thickness (mm) 5.6 9.8 11.0 10.5 14.0 17.5 9. Update the risk assessment as t whether r nt t use electric pwer tls r hand tls. 10. Use the apprpriate tl (e.g. ruter r saw) with depth setting per the table abve t cut a letter size pening in the tp f the cnduit with the viewing hle at the centre. 11. Carefully cut alng the tp and ring cut arund the ends f the sectin f cnduit t be remved. 12. Remve the sectin f cnduit. 13. Befre starting any wrk n the cable, prve that the crrect cable has been identified by ding bth f the fllwing: a. Use the cable identity tl t determine the crrect cable b. Spike/Cut the cable while de-energised. 14. Cmplete wrk t the cable, referring t any relevant field instructins. HV Cables fr Greenfields Subdivisins (Future Cnnectin) 1. If laying a cable fr a future scheme r cnnectin frm a universal pillar, kisk, r LV frame unit in an existing scheme, the remte end f the cable must nt be left n the drum. Instead, ensure it is: a. terminated b. insulated t apprved methds c. placed in a mini pillar with a white-clured dme tp 2. Where it is nt pssible r practical t install a pillar i.e. where the pillar will bstruct pedestrian access r create a safety hazard t vehicles, ensure the remte end f the cable is terminated in a suitable jint r shell and lcated undergrund in Hrizn Pwer s cable alignment. 3. Mark cable ends lcatin: On As cnstructed drawings, in GIS. CS# 2244623 FI 6.9 Undergrund Cables Page 4 f 6
Abandned Cables Cables t be abandned (bth HV and LV undergrund) fall int ne f tw grups. Grup 1: Cables that are nt suitable fr reuse These are cables that have been in service and have nw becme redundant thrugh damage r because they are t shrt t be reused. If these cables cannt be easily remved, they must: 1. Be left in their present lcatin. 2. Have their bare cres twisted tgether with screen wires wrapped arund these cres. 3. Have a heat shrink cap fitted. 4. Have their ends labelled externally and their lcatin recrded (see the General requirements sectin, belw). Grup 2: Cables that may be suitable fr reuse in the future These cables must be attended t as described belw. Befre reuse, these cables require testing by cable testing specialists t endrse reuse. XLPE cables XLPE cables must be prepared fr abandnment in the fllwing way: 1. Strip the cable ends. 2. Use the screen wires t wrap arund the bare cres (with a gd cntact). 3. Fit a heat shrink cap ver the end t seal the bare cres. Cnsac and PILCSWA cables Cnsac and PILCSWA cable sheath layers must be prepared fr abandnment in the fllwing way: 1. Strip back apprx. 150 mm dwn t the metal sheath. 2. Drive nails int the cre ends r between the cres and the sheath. 3. Tie cpper wire arund the nails. 4. Lay the wire ends against the metal sheath. 5. Fit a heat shrink cap. Small multi-cre PVC/PVC cables Small multi-cre PVC/PVC cables must be prepared fr abandnment in the fllwing way: 1. The cnductr ends must be stripped and twisted tgether with the screen. 2. Fit a push-n cap. CS# 2244623 FI 6.9 Undergrund Cables Page 5 f 6
General requirements Metal labels engraved r stamped abandned cable must be tied at the cable ends, arund the cable, using tw nyln cable ties, ne at each end f the label. The lcatin f each cable end must be measured frm a lcal reference pint and the data nted n the As cnstructed drawings. Cable preparatin befre terminatin Check heat shrink cap and cable fr signs f damage. If the cable is damaged r there are signs f misture ingress, ensure cable is tested befre terminatin. Remve the heat shrink cap. T prevent pssible static build up, cautin must be exercised while remving the heat shrink cap, ensuring the tl des nt cntact the cable cre r screen. While remaining insulated frm the cable, shrt the expsed cnductr and cable screen t earth. References Occupatinal Safety & Heath Act 1984 Occupatinal Safety & Health Regulatins 1996 SHMS OSH-3.6-1-02 Jb Risk Analysis (JRA) Prcedure SHMS OSH-3.6-1-26 Persnal Prtective Equipment SHMS OSH-3.6-1-17 Excavatin and Trenching Prcedures Electrical Safety Standards Switching Prcess and Rules 2.6 Wrksite Clthing / Persnal Prtective Equipment Requirements 2.15 Temprary Safety Barriers and / r Warning Signs 2.23 Jb Hazard and Risk Management (JRA) 2.25 Test befre Yu Tuch Prir t Cmmencement f Wrk 2.27 Safety Observer Rle 8.21 Wrk Permits 8.22 Switching Activities CS# 2244623 FI 6.9 Undergrund Cables Page 6 f 6