Nsp 004011 | Insulator (Electricity) | Electrical Conductor

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Guidance on Overhead Line Clearances
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    Document reference NSP/ 004 / 011 Version:-  3.0 Date of Issue:-  April 2014 Page 1 of 25   CAUTION! - This document may be out of date if printed   NSP/004/011 Guidance on Overhead Line Clearances 1.0   Purpose The purpose of this document is to specify the minimum clearances between overhead lines at all voltages up to and including 132kV and ground, general obstacles, railway and waterways property and other overhead lines. This document has been updated to represent current practices and the specific requirements of The Electricity Safety, Quality and Continuity Regulations (ESQCR). This document supersedes the following documents, all copies of which should be destroyed. Ref Version Title NSP/004/011 Version 2.1 Dated March 2010 Guidance on Overhead Line Clearances NSP/004/011 Version 1 Dated July 2006 Guidance on Overhead Line Clearances DSS/004/037 Version 1.0 - Dated 09/09/99 Guidance on Overhead Line Clearances OHI 16 ------------------------ Northern  –  Overhead Line Clearances 2.0   Scope Clearances given in this document are applicable to all new overhead lines and need not be applied retrospectively to existing lines. However if a “material alteration” is made to the line e.g. pole, conductor or crossarm change then the new clearances shall be applied. Clearances specified in this document refer to bare, lightly and effectively insulated line conductors  and have been determined to provide safety to the general public and protection against flashover of the line. These clearances are based on normal use of any land, buildings or structures crossed by the line, unusual situations can only be determined by local risk assessment and may require an increase in the clearances specified. Where effectively insulated conductors are used, ground clearances over roads accessible to vehicular traffic shall be maintained as stated in Regulation 17 (2) (a) of ESQCR 2002. Clearances over other ground or in proximity to objects may be reduced provided the effectively insulated conductor is not placed in a position where it is likely to be damaged or where persons going about normal everyday activities could come into contact with it.    Document reference NSP/ 004 / 011 Version:-  3.0 Date of Issue:-  April 2014 Page 2 of 25   CAUTION! - This document may be out of date if printed   2.1 Contents 1.0 Purpose ....................................................................................................................................................... 1 2.0 Scope .......................................................................................................................................................... 1 2.1 Contents ................................................................................................................................................. 2 3.0 Overhead Line Clearances .......................................................................................................................... 3 3.1 Introduction ............................................................................................................................................ 3 3.2 Siting of Overhead Lines ......................................................................................................................... 3 3.3 Application of Clearances ....................................................................................................................... 3 3.4 Allowance for Creep ............................................................................................................................... 3 3.5 Proximity of Overhead Lines to High Risk Localities ............................................................................... 4 3.6 Clearances to Ground and Roads and Objects ....................................................................................... 4 3.6.1 Clearances to Ground and Roads ....................................................................................................... 4 3.6.2 Clearances to Objects ......................................................................................................................... 5 3.6.3 Clearance from effectively insulated low voltage lines attached to poles ......................................... 7 3.6.3.1 Ground Clearance ........................................................................................................................... 8 3.6.3.2 Clearances to Buildings and Structures .......................................................................................... 8 3.6.3.3 Systems attached to Buildings ............................................................................................................ 9 3.7 Clearances where power lines cross or are in close proximity .............................................................. 9 3.8 Clearances to Railway Crossings ........................................................................................................... 10 3.9 Clearance to Waterways....................................................................................................................... 11 3.10 Clearance to Telecommunication Lines ................................................................................................ 11 3.11 Work in Proximity to Overhead Lines ................................................................................................... 12 3.11.1 Horizontal Clearances  –  on sites where there will be no work or passage of plant under lines. ...... 13 3.11.2 Vertical Passing Clearances  –  on sites where vehicles will pass under the lines. .............................. 14 3.11.3 Vertical Clearance  –  on sites where work will be undertaken beneath the line. .............................. 16 3.11.3.1 Work at ground level only. .............................................................................................................. 16 3.11.3.2 Work on buildings or structures underneath an overhead line ...................................................... 16 3.12 Clearance of Unsupported Jumper loops ................................................................................................. 16 4. References ................................................................................................................................................ 17 4.1 External Documentation ....................................................................................................................... 17 4.2 Internal documentation ....................................................................................................................... 17 4.3 Summary of Changes ............................................................................................................................ 18 5. Definitions ................................................................................................................................................ 18 6. Authority for issue .................................................................................................................................... 20 6.1 CDS Assurance ...................................................................................................................................... 20 6.2 Author ................................................................................................................................................... 20 6.3 Technical Assurance ............................................................................................................................. 20 6.4 Approval ............................................................................................................................................... 20 6.5 Authorisation ........................................................................................................................................ 20    Document reference NSP/ 004 / 011 Version:-  3.0 Date of Issue:-  April 2014 Page 3 of 25   CAUTION! - This document may be out of date if printed   3.0 Overhead Line Clearances 3.1 Introduction All clearances quoted (except those in sections 3.4, 3.6.2 &3.9) are those listed in ENA TS 43-08 Issue 3. A direct comparison can be made to the source document ENA TS 43-08 by removing the first digit (3) from all section and table referencing. Clearances which are bold and underlined  are statutory 3.2 Siting of Overhead Lines In siting an overhead line, special consideration should be given to the existing or future use of the land, buildings or structures over which the line is to be erected. In such cases, a reasonable and responsible attitude must be taken towards any danger which might arise. In order to prevent danger, increased ground clearances or the use of insulated or covered conductors may be necessary, as appropriate to the situation .  Guidance in the identification of high risk locations can be found by making reference to NSP/004/012  –  Guidance on the Risk Assessment of Overhead Lines. 3.3 Application of Clearances The following factors require to be taken into consideration when providing clearances to overhead lines: (i) Allowance shall be made for the effects of creep in conductors. (ii) In some cases, lines are operated at a lower voltage than that for which they are designed. It is important when specifying clearances to fixed objects that the clearances appropriate to the max potential nominal operating voltage of the line be adopted. (iii) When an overhead line is being erected in proximity to existing objects, the clearances shall allow for future maintenance of the object. (iv) When work is to be carried out, or objects are to be erected in proximity to an existing overhead line, the clearance may require to be increased substantially to allow for the operation and movement of site traffic. Detailed guidance on safe working methods are given in HSE guidance note GS6. Section 3.11 of this document has been included to allow site operators to comply with the requirements of GS6. 3.4 Allowance for Creep Allowance must be made for the effects of creep in conductors and setting out errors as the specified clearance must be maintained for the life of the conductor. This allowance shall be as follows: Conductor Type Additional Clearance Required Copper 450mm Aluminium Alloy 600mm ACSR 600mm    Document reference NSP/ 004 / 011 Version:-  3.0 Date of Issue:-  April 2014 Page 4 of 25   CAUTION! - This document may be out of date if printed   3.5 Proximity of Overhead Lines to High Risk Localities An overhead line route which crosses or is in proximity to a high risk locality shall be given special consideration. Reference shall be made to NSP/004/012 ‘ Guidance on the Risk Assessment of Overhead Lines’ for guidance in the correct identification and recommended minimum  mitigating measures. Where practical all new overhead lines will be routed to avoid the need to pass in close proximity to high risk localities. However where lines are specifically identified as being in close proximity to fishing or high amenity areas, new or existing bare conductors shall be replaced with effectively insulated conductors e.g. ABC on LV lines or the use of Lightly insulated conductors e.g. XLPE covered conductors on HV lines. 3.6 Clearances to Ground and Roads and Objects 3.6.1 Clearances to Ground and Roads The clearances specified in the table below shall not be infringed at the specified maximum conductor temperature with the conductor (including its suspension insulators if (fitted) hanging vertically in still air or deflected at any angle up to 45° from the vertical). Additional creep values detailed in clause 3.4 shall be added to these values. Table 3.6.1 - Clearances to Ground and Roads Item Description Minimum Clearance(m) System Voltage kV ≤33  66 132 275 400 3.6.1.1 Line conductor at any point not over a road (See note 1 & 8) 5.2 6.0 6.7 7.0 7.3 3.6.1.2 Line conductor to road surface other than as specified in item 3.6.1.3, 3.6.1.4 or 3.6.1.5 (note 2) 5.8 6.0 6.7 7.0 7.3 3.6.1.3 Line conductor to road surface of designated 6.1m High Load Route (note 3) 6.9 7.1 7.5 8.5 9.2 3.6.1.4 Line conductor to motorway or other road surface where Skycradle can be used (see note 4 & 6) 8.2 8.4 8.8 9.8 10.5 3.6.1.5 Line conductor to Motorway road surface where scaffolding is to be used on: (1)   Normal 3 Lane motorways. (2)   Elevated 2 Lane motorways (See note 5 & 6) 14.0 11.0 14.2 11.2 14.6 11.6 15.6 12.6 16.3 13.3 3.6.1.6 Bare live metalwork, e.g. transformer terminals, jumper connections, etc. (See note 7) 4.3 4.3 Controlled Zone - Safety Rules apply. Notes: 1. The specified ground clearance for effectively insulated conductors at locations, which are not over roads accessible to vehicular traffic, are included in Section 3.6.3. Such conductors shall be positioned so that they are not likely to be damaged or cause injury. 2. The height of any wire or cable (other than a line conductor) which is attached to a support carrying a line conductor is 5.8 m above any roadway irrespective of the line voltage. The clearances specified allow for the safe passage below the line of a vehicle of maximum height 5 m. These clearances are based on a vehicle height not exceeding 5 m (except for the 6.1 m high load routes). 3. 'High load' routes are roads designated by the Department for Transport, for which the higher load clearance of 6.1m shall be maintained. 4. These clearances apply to situations where it is possible to use a Skycradle for conductor erection and maintenance. These clearances allow for the positioning of the Skycradle under a live circuit. Where the
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