SOCIALIST REPUBLIC OF VIETNAM

                                        ____________________________________________________________________________________

 

VIETNAMESE STANDARD

ELECTRICAL SAFETY IN CONSTRUCTION

GENERAL REQUIREMENTS

TCVN 4086 - 85

 SOCIALIST REPUBLIC OF VIETNAM

 

VIETNAMESE STANDARD

ELECTRICAL SAFETY IN CONSTRUCTION

GENERAL REQUIREMENTS

TCVN 4086-85

 

• Prepared by:     The Institute of Construction Mechanization and Technology.
• Suggested by:   The Institute of Construction Standardization and Module Designs.
• Submitted by:  The Institute of Construction Standardization and Module Designs.
• Approved and issued by: The State Construction Committee.
• Under Decision No. 158/UBXD date 11 November 1985.

VIETNAMESE STANDARD

GROUP-H

 

ELECTRICAL SAFETY IN CONSTRUCTION GENERAL REQUIREMENTS	TCVN 4086-85
	Effect from date: 01 July 1986

1.         GENERAL REQUIREMENTS

1.1. This standard specifies the general requirements on electrical safety applied to all the construction and erection works on building sites.

This standard shall not be applied to any construction and erection work on building sites having electrical voltage of more than 1000V, on coal-mining sites and metal-mining sites.

1.2. Notwithstanding the requirements specified in this standard, in order to prevent harmful and hazard impacts to the life due to electrical currents, electrical arcs, electromagnetic and electrostatic effects, users of this standard, shall observe other applicable standards and codes on electrical safety.

1.3. Workers assigned to operate electrical equipment on construction sites shall be subjected to the qualification requirements specified in the attached Appendix - 1 of this standard.

1.4. All workers involved in construction and erection works shall have been being trained on electrical safety, they shall know how to have the victims disconnected from electrical sources and have the power victims first-aid upon electrical accidents.

1.5. In any construction and erection enterprise, there shall be employed with electrical safety officer(s) certified with safety qualification Level 4 or higher, who shall be in charge of safety on monitoring and operating of electrical equipment.

1.6. Directors of the construction and erection enterprises shall be of legal responsibility for electrical safety for the utilization of electrical equipment within the enterprises.

2.         REQUIREMENTS ON ELECTRICAL SAFETY

2.1. Upon designing electrical network on the site, it shall be confirmed that: the power system and the lighting system are separated, the network can be cut off as a whole, or locally to disconnect the electrical loads from any building location or any erection location.

2.2. Connection, disconnection, repairing, adjustment and trial running of electrical equipment shall only be assigned to the electrical workers who have sufficient competence on electrical safety as appropriate to that required by the equipment.

For movable electrical equipment, electrical hand tools, and portable lamps, connection to the network shall be made by the use of plugs and sockets. The connection shall be done so a manner as to maintain the good safety as required.

Replacement of blown-out fuses and light bulbs shall only by assigned to electrical workers. The electrical workers shall have their personal safety wares used during their replacement work.

2.3. Before erecting or repairing electrical network or electrical equipment, circuit breakers of the concerned area shall be cut off and a board showing a massage of “No power on, people are still in work thereon” shall be hung on the breaker. In addition to these actions, if the breakers are outdoors from the substations (section or branch breakers), the 3-phase grounding application shall be made at the source termination.

2.4. Construction and erection enterprises employing with the use of electrical hand tools, portable drills, electrical lamps, low-voltage transformers, frequency modulators etc. shall observe the following:

Before assigning electrical tools to the workers, the tools shall be tested by using a testing gauge (manometer) to check the resistance of the body shell and the grounding application. The shell structures shall be subjected to examination for whether the resistance is sufficient for the use or not. Permission shall not be strictly given to use hand tools revealing with evidence of potential failures.

Electrical hand tools shall have their identification numbered. After using, the tools shall be saved in dry places. Monthly, the tools shall be tested at least one time for the resistance and for the grounding applications. The testing operators shall be of safety qualification Level 3 or higher.

2.5. Before operating electrical hand tools, the operators shall carry out the actions of checking all the grounding applications, the travelling and rotating components; the technical conditions of the carbon brushes and the contacting drums.

2.6. For working in area of potential electrical shortcut dangers, besides the personal safety wares, the hand tools to be used shall be of resistance level 2 and 3. For working in area of very high shortcut dangers, the hand tools to be used shall be of resistance level 3.

Note:

     1. Classification of danger level to electrical shortcut is specified in the relevant Vietnamese Standard TCVN 2328-78 “Environment for Erection of Electrical Equipment – General Definitions”.

   2. Classification of shell resistance of electrical hand tools is specified in the relevant Vietnamese Standard TCVN 3144-79 “Electrical Engineering Appliances”.  

2.7. Supplying power to electrical hand tool having shell resistance level 1 (per TCVN 3144-79 “Electrical Engineering Appliances”), shall be done by using electrical cables having a grounding wire and the connecting devices having grounding terminations. The connecting devices (the plugs and the sockets) shall be of types capable to connect grounding first when putting on and to disconnect grounding last when disconnecting. In addition, the grounding application shall be provided at the termination of the connecting devices.

2.8. All metal scaffolding, electrical crane’s rails and metal parts of electrical construction equipment shall be grounded as those in compliance with the Vietnamese Standard QPVN 13-78 “Provisional Code on Grounding of Electrical Equipment”.

Electrical equipment having voltage of less than 1000V, supplied from power lines having a neutral grounding wire, the shell of the equipment shall be connected to “Zero” (connected to the neutral wire) as those in compliance with the Vietnamese Standard QPVN 13-78 “Provisional Code on Grounding of Electrical Equipment”.

2.9. Automatic protectors, switch-gears and other electrical devices used in the construction sites or erected on construction equipment shall be provided with body shell or case for protection purposes.

2.10. Power carrying parts of electrical equipment shall be isolated or bounded with fence, and placed in vacant locations of sufficient countermeasures to prevent from incident access.

2.11. For outdoors-electrical cables of the site’s temporary power supply system, coated cables shall be used and they shall be hung on high props via porcelain insulators. Vertical clear distance from the cables to the ground level or the working floor shall not be less than the following values:

2.5m where a manual working area is under the cable lines (the jobs will not employ tools or equipment having their sizes over the man’s reach);

3.5m where a pathway for pedestrian footpath is under the cable lines;

6.0m where a roadway for equipment access is under the cable lines;

6.5m where a railway for tramcars or trains is under the cable lines;

(distance  calculated from the top level of the rails)

Electrical cables within a span length of poles shall not have more than two joints; the joints shall be located near the porcelain insulators;

2.12. Upon erection of power lines and operation of electrical equipment, provisions shall be made to prevent them from thermal heating due to overload, poor jointing or connection.

2.13. For soft cable wires in the construction site supplying power to movable machines, equipment or for temporary use, provisions shall be made to protect the cables from being scratched. Where a cable wires cutting vehicle roads, they shall be hung over the roads or buried under the roads by being passed thorough steel pipes or shaped steel tubes. If the cable wires are placed in a mining area, the power in the cable wires must be cut off before igniting the mines. After the explosion, the cables shall be checked to detect and repair any defect before the power can be re-connected.

2.14. To protect the power lines and the electrical equipment from shortcut between the phase lines and between the phase lines with the equipment’s shell, automatic protectors or fuses with proper melting rate shall be used.

2.15. Lighting lamps installed in connection with the power lines having voltage of 127V and 220V (phase voltage only) shall be placed on a level at least 2.5m high from the ground or the working floor. If the working spaces limit the height to less than 2.5m, lighting lamps of 36V or less shall be used.

2.16. While working under a special dangerous area as those defined by the Vietnamese Standard TCVN 2328-78 “Environment for Erection of Electrical Equipment – General Definitions”, portable lighting lamps of 12V shall be used.

Power 36V or less may be supplied from low voltage transformers, generators and batteries. Low voltage transformers of auto-responding types shall not be used to supply this 36V power.

2.17. Electrical welding equipment shall satisfies the requirements specified in the Vietnamese Standard TCVN 2290-78 “Production Equipment – General Requirements on Safety” and the TCVN 3144-79 “Electrical Engineering Appliances – General Requirements on Safety”.

2.18. Electrical welding works shall be taken in compliance with the Vietnamese Standard TCVN 3146-79 “Electrical Welding Works – General Requirements on Safety” and the TCVN 3254-79 “Fire Safety – General Requirements”.

2.19. Welding torches shall be of types satisfying the requirements specified in attached Appendix - 2 of this standard.

2.20. Connection of electrical welding equipment (generators or welding transformers) to the power source shall be made thorough circuit breakers. The circuit breakers shall be placed at convenient locations, 2m to 20m far from the welding location. Where welding is taken on a high place, there shall be assigned with one person in welding and one person in watching. The person in watching shall take care the person in welding for promptly cutting off the breakers upon detecting accident.

2.21. Where welding is employed by the method of manipulation with the use of electrodes, two cable wires shall be used, one is to be connected to the welding torches and other (the return cable) is to be connected to the base metal, where the termination of transformer’s secondary coil shall be connected to the return cable and it shall also be grounded.

2.22. Power cables used for welding purposes shall be of coated types suitable to the used voltage and having sufficient cross-section area to endure the high welding intensity at maximum gear. Jointing in the cables shall be securely made to prevent them from thermal heating and they shall be covered with insulation tapes. Welding cables should not be left running over power cables. In case of inevitability, the welding cables shall be placed under the power cables.

2.23. No allowance shall be made to use grounding wires, water steel pipelines, gas pipelines, or metal structures of buildings and plants in replacement of the returning lines for welding purposes.

2.24. Electrical equipment, during the time of being used on the site, shall be distinguished with the use of safety warning boards as those specified in the Vietnamese Standard TCVN 2572-78 “Electrical Safety Warning Signs”.

2.25. Construction and erection works carrying out under the live aerial power lines shall only be executed unless the writing permission of the power line managing authority is given and all the conditions for safety working have been prepared. During the construction or erection progress, the electrical safety officers shall be full time available on the site for giving safety instructions.

The writing permission for working on the dangerous area under live aerial power lines shall have the enterprise signed by both the technical vice director and the chief officer specially in charge of electrical safety assigned as in compliance with the sub-provision 1.5 of this standard.

2.26. Before allowing construction machines (cranes, excavators, etc…) to work on the dangerous area under live aerial power lines, the power in the lines shall be cut off and the actions specified in the above sub-clause 2.25 of this standard shall be taken.

Definition of the dangerous area under the aerial power lines shall be as those specified under the attached Appendix - 3 of this standard.

In case of inevitability to cut off the power in the lines, for working purpose of the construction machines, the actions specified in sub-clause 2.25 and the followings shall be exercised:

Distance from the outmost point of any lifting or traveling part of the construction machines to the outmost vertically projected plane of the power lines shall not be less than the following values:

 

 

Voltage of the aerial power lines (kV)	Minimum distance (m)
Less than 1	1.5
From 1 to 20	2.0
From 35 to 110	4.0
From 150 to 220	5.0

 

1. Construction machines are allowed to work directly under the live aerial power lines of 110kV or more unless the requirements specified in sub-clause 2.26a of this standard is satisfied.
2. Workers operating construction cranes shall be of safety qualification Level 2 or higher.
3. Body of cranes (except crawlers) shall be grounded by using a mobile grounding rods.

 

3.         REQUIREMENTS ON USING OF PERSONAL SAFETY WARES

1. Provisions shall be made to provide personal safety wares to electrical equipment operators as that in compliance with the Vietnamese Standard TCVN 2291-78 “Safety Wares for Labors. Classification”.
2. Personal safety wares shall be accompanied with test records. Test results obtained from regularly tests shall be recorded on, clearly stated with the date, month, year of recording. Before using rubber safety wares, the wares shall be carefully checked, cleaned, and dried if being wetted. Hollowed, tattered, or cracked wares shall not be used.

 

4.         EXAMINING THE COMPLIANCE OF SAFETY REQUIREMENTS

1. Regularly examining the electrical resistance of the power cables and the electrical equipment by the use of manometers or other appropriate measuring instruments (in appropriate to the level of accuracy or the range of measuring) shall be taken. The power in the cables shall be cut off before the measuring instruments can be connected.

APPENDIX – 1

REQUIREMENTS FOR WORKERS OPERATING

ELECTRICAL EQUIPMENT ON THE SITE

 

1. Workers operating electrical equipment shall be trained and qualified with training courses in electrical engineering and electrical safety. The contents of the courses shall be as those as suitable to their target operations.
2. Workers monitoring or operating electrical equipment shall be of sufficient heath strength, no blood and heart attack, and they shall be subjected to regularly heath testing as per the applicable regulation specified by the Ministry of Health.
3. Workers operating electrical equipment on the site shall have their job qualifications appropriate to their assigned works, and they shall have the electrical safety qualification levels appropriate to that specified for their involved engineering fields. Safety qualification levels specified for electrical equipment operators shall not be less than Level 2; for substation monitoring operators shall not be less than Level 3.
4. Electrical workers on construction site shall be provided with personal safety wares as those in compliance with the applicable regulation, and they shall be of sufficient skill to have the power victims first aided.
5. Workers operating electrical equipment shall be trained with safety techniques and shall be subjected safety technique testing at annual frequency.

APPENDIX – 2

TECHNICAL REQUIREMENTS FOR WELDING TORCHES

 

Welding torches shall satisfy the following requirements:

The power carrying parts of the torches should be made of copper.

The handles of the torches shall be made of power resistance and heat resistance materials.

The pincers of the torches shall be provided with springs in order to keep the electrodes tight.

The jaws of the torches shall be provided with grooves in order to keep the electrode fixed.

Devices to maintain the close contact between the welding cables and the torches during the welding progress shall be provided.

Where the welding power is more than 600A, the torches shall not be of the types having the welding cables placed inside the handles.

 

APPENDIX – 3

DEFINITION OF DANGEROUS AREA

 

Dangerous area under the live aerial power lines are defined as the space limited by the ground and the two parallel vertical planes, the first one is the vertically projected plane of the outmost wire in the lines (in static status); and the other one is far from the first one a distance corresponding to the voltage stated below:

 

Voltage (kV)	Distance (m)
Less than 1	2
From 1 to 20	10
35	15
110	20
From 150 to 220	25

 

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