Advice To Site Personnel When Working Near Underground Electricity Cables

1. Damaging underground electricity cables is dangerous and can often cause flashover, explosion or fire.

2. Damage can result from excavation or penetration of the ground.

3. Underground electricity cables may be found under roads, footpaths and on sites. Always assume that they are present. Treat any cables found anywhere as LIVE.

Before Starting Works

Before starting works, the contractor or person responsible for the proposed works should go through the following checklist:

1. Make sure you have plans of the underground electricity cables in the area before carrying out any works except for minor shallow excavation of less than 450 mm in depth from ground level and 2 sq. m in size. When plans of underground electricity cables are not available, in case of an emergency or unforeseen works, contact the relevant electricity supplier for assistance. Remember that the plans are used for reference only and a cable locator must always be used to identify the existence and alignment of the underground electricity cables in the works site or its vicinity.

2. Check whether the works site is within the vicinity of underground cables in accordance with the distance specified in Table 1 of the Code of Practice. If the cable plans provided by the electricity supplier indicate that there are underground cables within the works site and/or the area of the specified distance from the works site, appoint a competent person to carry out cable detection work.

3. Carry out passive cable detection by the competent person who shall propose trial holes to expose the target cables.

4. Confirm the location of the underground electricity cables by exposing the cables using hand-dug trial holes and toroidal active cable detection under the supervision of a competent person, except for minor shallow excavation.

5. Ensure that the alignment and depth profile of any underground electricity cables as identified by the competent person in the area are clearly marked on the ground.

6. Ensure that a written report of the works is obtained from the competent person. The written report should contain information on the alignment and depth of the underground electricity cables as identified.

7. Arrange site briefing to site personnel and explain the contents of the report, related information and the necessary safety precautions.

During the Course of Works

During the course of the excavation, all site workers should exercise the following precautions:

1. Whenever possible, hand dig near underground services. Spades and shovels are safer than picks or forks.

2. Watch out for signs and the position of cables as work continues.

3. Do not use hand-held power tools directly over the marked alignment of an underground electricity cable identified by the competent person. Only use such tools if the work cannot feasibly be carried out by hand tools.

4. For hand-held power tools used for the purpose of breaking paved concrete surfaces, a horizontal clearance of 250mm from any underground electricity cable must be maintained. Otherwise, a clearance of 500mm around any underground electricity cable nearby must be maintained.

5. Keep a clear distance of 1m between the side of any distribution cable (i.e. voltage below 132 kV) and the bucket of a mechanical excavator, and for transmission cables (i.e. voltage at 132kV and above), the distance is extended to 3 m.

6. Keep a clear distance between underground electricity cables and other utilities (e.g. gas and water pipes, telecommunication cables, etc.). The distance should be at least 300mm for cables of below 132 kV and at least 1 m for cables of 132 kV and above.

7. Do not let existing underground electricity cables go into a manhole or other structure or encase them in concrete.

8. Always provide adequate support and anchoring for exposed underground electricity cables according to the electricity supplier's recommendations.

9. Report any electrical accident or damage to an underground electricity cable or its sheath, to the relevant parties, and the electricity supplier. Even if there is no immediate danger, the damage could lead to danger at a later date. Evacuate everyone from the immediate area of the damage but do not attempt to remove any objects or touch any injured persons, who are in contact with the damaged cable because the cable may still be LIVE. Cooperate as requested with the electricity supplier by providing access to the works site for the repair of the cable.

10. Even if the underground electricity cable seems to be disconnected or abandoned, do not attempt to drill or cut into it, or to dismantle it until approval has been given by the electricity supplier.

11. All backfilling of excavations must be done carefully and warning tapes, tiles, protection plates or other protection must be replaced in their original position. The electricity supplier should be approached for make-up cable protection materials if they are missing or damaged before the backfilling. The same backfilling materials should be used unless otherwise agreed with the electricity supplier. If in doubt, the contractor must seek advice from CLP or HEC on the specific requirements for backfilling of excavation including the thickness of the bedding layer, type of materials to be used and method of compaction, etc.

Enquiries

Enquiries on the Electricity Supply Lines (Protection) Regulation and this advice can be addressed to the Electricity Legislation Division of the Electrical and Mechanical Services Department.

Contact Details of CLP Power Hong Kong Ltd. (CLP)

Information on CLP's underground electricity cables in the vicinity of works to be undertaken can be obtained from CLP at the following address:

General enquiries and incident reports of CLP's underground electricity cables can also be made by calling or faxing the above numbers.

Contact Details of The Hongkong Electric Company Limited (HEC)

Information on HEC's underground electricity cables in the vicinity of works to be undertaken can be obtained from HEC at the following address:

General enquiries and incident reports of HEC's underground electricity cables can also be made by calling or faxing the above numbers.

Note : This is NOT a legal document and is prepared for general information only. The detailed guidelines for works in the vicinity of underground electricity cables can be found in the Code of Practice on Working near Electricity Supply Lines published by the Electrical and Mechanical Services Department.