This Guidance Document describes rules and procedures for safe working with high voltage electrical equipment. It details operating procedures, Permit to Work and other safety documents, provisions for entry into High Voltage enclosures, safety precautions prior to working on conductors and tests required on equipment.
It is recommended that the rules and procedures given in this Guidance Document be applied to all high voltage systems under the ownership or control of corporate companies.
The rules and procedures outlined in this document exclude any particular requirements for working on or near overhead lines.
- RESPONSIBILITIES OF THE COMPANY MANAGEMENT
It is the responsibility of the Head of site, or a higher authority if safety responsibility has not been delegated, to ensure that the statutory requirements governing the electrical system or systems are adhered to. The Supply Leader may delegate this responsibility to a suitably qualified engineer.
On the recommendation from the Maintenance Manager, the Supply Leader must appoint a competent person that is familiar with the electrical standards and guidelines to coordinate and instruct persons on high voltage work. This person will then be responsible for the operation of the high voltage system and the implementation of the rules and procedures for working in high voltage systems. Where appropriate, this same person should be made responsible for all Electrical Safety on the site at all voltages and should be given the necessary authority to implement this responsibility.
The Supply Leader of site must be satisfied that the Competent Persons have sufficient technical knowledge and experience to act within the limits of their Certificate of Authorisation. The Supply Leader and Human Resources of site shall ensure that all persons’ authorisations are included on the relevant job description.
The Supply Leader of site must, by means of an annual review with the Maintenance Manager, ensure that all persons with responsibilities for working on high voltage system are adequately trained.
The Maintenance Supervisor responsible for the Electricians shall ensure that the performance of all staff is regularly monitored and safety documents issued by them are regularly reviewed.
A formal safety documentation system must be put into operation. The Supply Leader must be satisfied that this has been carried out and is implemented.
The Supply Leader must be aware that the rules and procedures limit the access to high voltage enclosures to properly authorised persons. He must also ensure that those who are not competent to prevent the occurrence of injury and those whose presence is unnecessary are not permitted into the enclosures. All management and staff must be made aware of this restriction.
In some instances the Supply Leader may not have personnel on site that is qualified to perform the task of working on high voltage. In this event he/she must appoint a contractor who is prepared to accept the responsibility, formally in writing, to operate the system. He/She must satisfy themselves that the contractor has rules and procedures and has monitoring systems which ensure that his own rules and procedures are properly operated.
- GENERAL REQUIREMENTS
All corporate sites that receive, generate and operate electrical systems at high voltage must have a safe system of working for those operating and maintaining such electrical systems. They must have rules and procedures for safe working with high voltage equipment that are in full compliance with local statutory regulations. The site management is responsible for the application of these rules and procedures.
Rules and procedures for safe working with high voltage equipment must include, but may not be limited to, the following:
- Permit-to-Work system;
- Safety documents;
- Selection procedures for persons authorised to work with high voltage equipment.
Throughout the world, factories, shops and office premises are usually required to comply with certain statutory regulations which include conditions controlling the use of electricity aimed primarily at the safety aspect.
- HAZARDS ASSOCIATED WITH HIGH VOLTAGE EQUIPMENT
High voltage circuits, with their associated higher fault levels, have a greater number of hazards than low voltage circuits. This is not only due to the increased voltage but also because, under certain circumstances, high voltage circuits can retain a lethal charge even when switched off. In addition, dangerous potentials can exist some distance from live high voltage conductors.
Due to the high fault levels associated with high voltage systems, the energy released in the event of an accident may cause a fire or explosion with the associated risk of serious injury or death. For these reasons persons must be competent and aware of the danger.
- WORK ON HIGH VOLTAGE EQUIPMENT
To operate or work near a high voltage system safely and to comply with the relevant legislation it is necessary to ensure that all persons concerned are suitably qualified and competent for the duties they are to perform.
It is therefore essential, in order to provide maximum safety to personnel and equipment, that all persons who are required to work on or near, or to operate high voltage equipment, or even enter high voltage enclosures must be:
- fully aware of the hazards involved;
- have been trained in the correct procedures for avoiding danger;
- have the relevant electrical certification and training, including Arc Flash for their particular duty.
Only principal definitions which could lead to misunderstanding are given below. Other definitions will be found in the relevant national and international standards.
Connection between conductors and earth in addition to a Circuit Main Earth applied after the issue of a safety document.
Applied to equipment or procedures approved for use within the company by the Senior Authorised Person. Such approval should be in writing.
CIRCUIT MAIN EARTH
Connection between all relevant conductors and earth applied to prevent conductors becoming live before a safety document is issued and removed after the safety document is cleared; the number and location of each main earth fitted shall be recorded on the Permit to Work.
The local corporate Operating Company responsible for the electrical distribution system or systems.
An electrical conductor forming part of an electrical system.
A risk to health or of bodily injury.
At or about zero voltage.
The conductive mass of the earth whose electrical potential at any point is conventionally taken as zero.
Connected to the general mass of earth in such manner as will ensure at all times an immediate discharge of electrical energy without danger.
An area contained within a building, perimeter fence, cubicle etc. containing high voltage equipment.
Anything used, intended to be used or installed for use, to generate, provide, transmit, transform, rectify, convert, conduct, distribute, control, store, measure or use electrical energy.
Bare or insulated conductor, excluding properly designed and applied cable, which is exposed to touch.
Exceeding 750V between conductors or between any conductor and earth.
Disconnected and separated from every source of electrical energy in such a way that the disconnection and separation is secure.
See ‘Switching Log Book’.
NOTICES AND LOCKS
An approved form of notice prominently displayed on the electrical equipment when DEAD, warning against making such equipment live.
An approved form of notice prominently displayed on, or adjacent to, LIVE electrical equipment drawing attention to the danger of interference with such apparatus.
A padlock (differing from safety locks), having a common key pattern, used to prevent unauthorised operation by locking specific switchgear, when the need for a safety lock is not considered necessary.
A padlock having a unique key pattern which is used in the isolation and/or earthing of electrical equipment in conjunction with a Permit to Work.
Authorised Person (Maintenance Manager)
A competent person who has been appointed in writing by the Supply Leader to carry out specified duties which may include authority to issue and cancel specified safety documents.
A person, appointed in writing by the Supply Leader on recommendation from the Maintenance Manager, who has sufficient technical knowledge and experience to enable him to avoid danger and who may be nominated to accept and clear specified safety documents.
A person who is adequately advised or supervised by a competent person to enable that person to avoid dangers which electricity may create.
- RULES AND PROCEDURES
Not unless specifically stated, the term “rules and procedures” as used in this document refers to the rules and procedures described in this document.
The testing of high voltage insulation by means of an externally applied test voltage.
Isolation and Earthing Request
A safety document requesting the isolation of a circuit and/or the earthing of a circuit.
Limitation of Access
A form of declaration signed by an Authorised Person for any work in substations, switch rooms or compounds when a Permit to Work is not applicable and when verbal instructions are not considered sufficient. It is given to the person in charge of or doing the work in the vicinity of live equipment and defines the location and scope of the work and the precautions to be taken to avoid danger.
Permit to Work
A form of declaration by an Authorised Person and given to the person in charge of doing the work, specifying the equipment on which it is safe to work, the means of achieving safety and the work to be carried out on it.
Corporate Company’s area or location where the high voltage electrical power is supplied and distributed.
SPIKING OF CABLES
The operation of driving a metal spike through a cable thus connecting the conductors to the sheathing and/or armouring as applicable.
An electrical system in which circuit conductors and equipment are electrically connected to a source of supply.
The opening of a circuit breaker either by means of a manual trip button or automatically by a trip coil.
The testing of circuit conductors to establish that they are not live.
Either the persons under the immediate supervision of a competent or authorised person (who shall himself be a member of the working party) or a competent or authorised person when working by himself.
- GENERAL SAFETY REQUIREMENTS
ISSUE OF RULES AND PROCEDURES
The company Supply Leader is responsible for the application of the rules and procedures for safe working in high voltage systems on site. This responsibility may be delegated in writing to a suitably qualified engineer who must ensure that a copy of these rules and procedures are issued to such employees, and other persons, whose duties require them to work on or near high voltage electrical equipment. Each recipient of the rules and procedures must sign a receipt for his copy, should keep them in good condition and have them available for reference as necessary when work under these rules and procedures is being carried out.
In the event of any work, including switching at high voltage being performed by contractors, the Supply Leader must formally issue in writing a copy of the rules and procedures to these contractors. The contractors must confirm in writing the receipt and their acceptance of the rules and procedures.
VARIATIONS OF RULES AND PROCEDURES
In exceptional or special circumstances, these rules and procedures may be varied to such an extent as is necessary and approved by the Supply Leader. These variations may be required to comply with local legislation and requirements in other countries. Where variations to these rules and procedures are adopted, the revised rules and procedures should be issued as a document dedicated to the relevant site(s).
When any person receives instructions regarding the operation of or work upon the company high voltage system he must report any objections he may have to the carrying out of such instructions to the person issuing them. If such objections are reported, the person issuing such instructions will have the matter investigated before work proceeds and, if necessary, refer it to a higher authority.
- REPORTING OF ACCIDENTS AND DANGEROUS OCCURRENCES
In addition to reporting in compliance with Governmental requirements, any accident or dangerous occurrence must be reported to the company’s Supply Leader and then to any other person designated in the company’s safety procedures.
- SAFETY DOCUMENTS
Safety documents must be operated throughout the entire site.
- MAINTENANCE AND WORK ON HIGH VOLTAGE SYSTEM
All persons responsible for the maintenance of high voltage switchgear should be conversant with relevant NFPA 70E or CSA Z462.
- INTERFERENCE WITH HIGH VOLTAGE EQUIPMENT
No person must work upon or interfere with any high voltage equipment unless specifically authorised by a relevant safety document to work on the equipment.
- ISOLATION OF REMOTE/AUTOMATIC CONTROL EQUIPMENT
All remote or automatic control equipment such as “on load” tap changers must be isolated and locked off before a Permit to Work is issued for the relevant equipment.
- AUTOMATIC FIRE PROTECTION SYSTEMS & OTHER HAZARDS
Safety precautions with respect to Fire Protection Systems or other hazardous systems or materials such as compressed air supplies and SF6 (chemical) must be followed in accordance with site safety procedures.
- MANNING REQUIREMENT
The following must be posted/located in a prominent position in each substation and High Voltage switchroom:
- A chart detailing the treatment of a person suffering from electric shock;
- Single line diagrams (reflecting the current status of the installation);
- A copy of the site rules and procedures for safe working with high voltage equipment;
- Hand-held fire extinguisher(s) suitable for use on electrical fires.
All important parts and points of the electrical installation (e.g. busbar systems, switchgear, transformer, conductors, substations) must be clearly, legibly and durably marked with information plates and site equipment reference labels. Labelling should be in accordance with the drawing of the System Distribution Network. The Senior Authorised Person must ensure that all labelling is correct.
The operational state of high voltage switchgear and control gear must be clearly shown by indicators, except when the main contacts can clearly be viewed by the operator.
- DISPLAY OF DOCUMENTS
A chart detailing the treatment of a person suffering from electric shock, a drawing of the System Distribution Network, the rules and procedures and, where required, copies of any relevant Statutory Requirements must be posted in a prominent position in each power station, substation and High Voltage switchroom.
- WORK BY THIRD PARTIES ON HIGH VOLTAGE EQUIPMENT
Work on high voltage equipment must only be carried out after the issue of the relevant Safety Document.
It is recommended that all enquiries and orders for equipment associated with the high voltage system should include the following statement :
“Rules and Procedures relating to high voltage electrical equipment including a Permit to Work system are in force for the high voltage system in this factory and their requirements must be met by any contractor, his agents or servants when working on high voltage equipment or in high voltage enclosures”.
A copy of the rules and procedures should be handed to the contractor where applicable and the contractor must either accept these rules and procedures and agree in writing to work to them or use his own rules and procedures. Where it is agreed that the contractor may use his own rules and procedures, the formal rules and procedures to be adopted must be agreed in writing.
- REMOTE SWITCHING
Wherever possible, switching operations shall be carried out via remote control equipment external to the switch room and persons shall not remain in the switch room while switching operations are in progress.
- HIGH VOLTAGE MOTORS
A high voltage Permit to Work for the routine switching and isolation of high voltage motors is not considered necessary, provided that an agreed method of isolating, locking off and posting caution notices is written down and strictly observed. Company Safety Rules for working on mechanical plant should be followed. Where high voltage conductors are exposed, a Permit to Work shall be issued.
- ACCESS TO HIGH VOLTAGE ENCLOSURES
People who are not competent to prevent the occurrence of an injury and those whose presence is unnecessary are not permitted into high voltage enclosures.
No persons must, without proper written authority, enter or have access to any high voltage enclosure unless accompanied by a competent person and unless there is good reason for their presence.
Barriers, doors or gates restricting access to substations, transformers and similar areas containing high voltage equipment must be kept locked. The control of keys for these locks must be included in the rules and procedures for safe working with high voltage equipment.
All access doors to enclosed high voltage electrical operating areas and all sides of outer perimeter fences enclosing high voltage operating areas must be provided with following externally positioned warning signs and notices:
- Warning against unauthorised entry e.g. stating “No Admittance – Authorised Personnel Only” (Typical Caution and Danger Signs).;
- Electrical Hazard Warning;
- The name of the high voltage operating area;
- The nominal voltage.
- FAILURE OF SUPPLY (Power Outage)
A failure of supply, from whatever cause, to or from any part of the high voltage system shall be reported immediately to the Supply Leader either on site or at his emergency telephone number. During failures of supply all equipment and conductors must be regarded as being live until isolated, proved dead and, where necessary, earthed.
This procedure is only for reference – always follow safety rules prescribed by your local H&S department.