Electrical Safety Procedure /
RL-HSE-0001/SP0014 / Revision 03 / September 2008
/ RAS LAFFAN POWER COMPANY /
RL-HSE-0001/SP0014
ELECTRICAL SAFETY PROCEDURE
Revision 03
AES ROC SAFETY MANAGEMENT SYSTEM
Rev
# / Issue Date / Amendment Description / Date effective / Prepared
By / Review By / Approved by
03 / 09/08 / Electrical Safety Procedure separated from Safety document procedure and modified according AES corp electrical safety standard
Personal Protective Grounding Procedure added to Electrical Safety Procedure / 09/08 / M. Kallyan / HSE Committee / K. Venkatachalam
1. Purpose
Electrical safety standard is established to protect AES employees from serious injury and property from serious damage that could result from work activities involving (or in proximity to) energized electrical equipment within Ras Laffan Power and Desalination plant. It also provides employees with an understanding of the hazards associated with working on or near energized electrical equipment and the precautionary measures needed to reduce these hazards.
1. Prove that the electrical circuit or equipment is in fact removed from a dynamic source of electrical energy.
2. Provide protection in the case of accidental re-energization that may be caused by operator error, contact with neighboring circuits, lightning, backfeed, insulator failure, etc.
3. Provide protection from electrostatic and electromagnetic induction that may be caused by adjacent energized circuits, wind or energized equipment.
2. Scope
This safety standard applies to all work activities conducted at Ras Laffan Power and Desalination plant, that is performed on or in proximity to energized electrical equipment.
For the purposes of this standard, the scope of standard is designated as all equipment and processes associated with the generation of electrical energy up to and including the Gas insulated substation GIS.
3. Definitions
Arc-Flash - Temperatures created when an electric current passes through air between two conductors that can be as great as 35,000°F (20,000 °C). Exposure to these extreme temperatures can result in life threatening burns.
Arc Blast – An extremely high temperature explosive expansion of both metal and the surrounding air in an arc flash path. Copper expands by a factor of 67,000 times when changed from a solid into a vapor, high velocity shrapnel, material and molten metal is expelled away from the arc at speeds exceeding 700 miles/hour (1200 km/hr).
De-energized: No electrical voltage exists (verified by testing).
Energized: Voltage is present or considered present (unless proven otherwise) on a piece of electrical equipment.
Earthing Device: An approved means of providing a connection between an electrical conductor and earth, being one of the following:
· Primary Earth - A fixed or portable Earthing Device applied to an electrical conductor to protect against inadvertent energization;
· Drain Earth - A fixed or portable Earthing Device applied for the purpose of protection against induced voltages.
Electrical Environment - An environment subject to electromagnetic induction, high step and touch potentials during a system fault and exposed electrical apparatus closer than the minimum approach distance.
Exposed parts - Energized electrical parts, not guarded, isolated, or insulated, capable of being inadvertently touched or approached closer than a safe distance.
Flash Protection Boundary – An approach limit at a distance from live parts that are un-insulated or exposed within which a person could receive a second-degree burn in the event of an arc.
High Voltage: The presence of more than 600 volts phase to earth voltage.
Isolated – A circuit or electrical equipment that is removed from a source of electrical energy and prevented from re-energized by means of control, secure and safe position.
Low Voltage: The presence of more than 50 volts but no more than 600 volts nominal.
Limited Access Certificate: A Safety Document defining limits within which work may be carried out where there is no risk of any person coming in contact with Hazardous Energy.
Minimum Approach Distance – The closest distance that any part of an employee’s body including the length of any conductive tool being used to perform work is permitted to approach exposed energized apparatus or circuits without the use of protective equipment and/or safe work practices.
Electrically Competent Person - A person who is trained and has demonstrated proficiency in:
1. Recognition of voltage levels of exposed energized parts.
2. Knowledge and methods to maintain the minimum approach distances and flash protection boundaries for the voltage levels in and near the work site.
3. Recognition of potential electrical hazards when working on or near energized equipment.
4. Knowledge and skills to safely perform work on or near energized equipment operating at voltage levels exceeding 50 volts.
5. Emergency procedures including, but not limited to, first-aid, cardiopulmonary resuscitation (CPR), and rescue procedures.
6. The proper use of special precautionary techniques, personal protective equipment (PPE), insulating and shielding material, and insulated tools for working on or near energized parts of electrical equipment.
Safe Distance: The distance from the nearest High Voltage exposed conductor not connected to earth by means of an Earthing Device, or from an insulator supporting a High Voltage conductor, which must be maintained to avoid danger.
Step Potential – The voltage between the feet of a person standing near an energized grounded object (read more in the Appendix)
Touch Potential – The voltage between an energized object and grounded object a person could touch
Protective Grounding (Earthing) – Effectively connecting an electrical circuit or electrical equipment to ground/earth potential.
Bonding – Connecting all grounds (bonds) to a single point to eliminate differences of potential at a work site.
Bonding Principle – Bonds are installed so that a worker is kept in an equi-potential zone. A worker must not be able to bridge between a grounded circuit and any unbonded structure, vehicle, boom, wire or any other object not tied into the bonded network.
Grounding Principle – Protective grounds are installed to reduce any current flow through a worker to an acceptable level by providing a low resistant parallel shunt around the worker. If the circuit is or becomes energized, the grounds must be big enough to withstand any fault current in the circuit.
Bracket Grounding (box grounding) – Grounding at each potential source, not more than 2 miles (3km) on each side of the work site. Bracket Grounding shall only be applied when no possible source of re-energization may occur.
Equipotential Grounding – Grounding and bonding together all objects, including the structure to a single point to eliminate differences of potential at a work site.
Dynamic Electrical Source – A source from the electrical system itself, not from induction or portable generators.
Grounding Plan – An approved written document for planning the complete isolation of a circuit and the locations for the installation of protective grounds.
Ground Set – The cable, screw type ground clamps and pressed ferrules, assembled together as equipment used for applying personal protective grounds.
Grounding Set Tester – A device designed to test the resistance of a complete ground set.
Isolated – A circuit or electrical equipment that is removed from a source of dynamic electrical source.
Potential Tester – A device used to test a circuit or equipment for the existence of dynamic electrical energy.
4. General Rules & Responsibilities
4.1 General Rules for working on or near High Voltage equipment
a. When practicable, any work performed on electrical circuit and electrical apparatus must be started after ensuring that the equipment is de-energized and grounded.
b. All AES employees whose work activities require potential exposure to electrical hazards in generating stations and in any associated substations must be a qualified electrical worker
c. All High Voltage equipment shall be considered to be Energized unless it can be demonstrated by means of an appropriate Tag Out Order that the equipment has been De-energized.
d. Nobody shall allow any part of their body or objects to approach Energized exposed conductors beyond the Safety Distances.
e. Unqualified workers and mechanical equipment must stay at least 10 feet (3 meters) away from exposed circuits up to 50kV. At voltages over 50,000 volts, the distance is increased by 4 inches (10 cm) for every additional 10,000 volts, i.e. 14 feet (4.3 m) for 169 kV, 16 feet (4.9 m) for 230 kV, and 25 feet (7.6 m) for 500 kV.
f. A qualified electrical worker must know what is safe to touch in the specific areas being entered.
g. A qualified electrical worker must know the maximum voltage within an area being entered and the minimum approach distances for that maximum voltage and the flash protection boundary for the equipment.
h. When Isolating Devices have been placed into their Safe Position and exposed conductors could be subject to High Voltage, the only objects permitted to approach within the Safety Distances shall be approved voltage measuring devices or Earthing Devices. In special instances, and subject to assessment by a Control Room Engineer, persons may approach within the Safety Distances for the application of the above approved devices.
i. Safety Distances (obtained from National Electrical Safety Code Table 441-1)
Rated SystemAC Voltage
(phase-to-earth) / Safety Distance
from Live AC Conductors
Phase-to-ground (ft – in) / Phase-to-phase (ft – in)
0 to 50V
50V to 300V
300V to 750V
750V to 15kV
15kV to 36kV
230kV to 242kV / Not specified
Avoid contact
1-0
2-2
2-7
5-3 / Not specified
Avoid contact
1-0
2-3
10-0
16-6
j. A qualified electrical worker must know and use applicable protective equipment and work practices necessary to perform the assigned work within the minimum approach distance.
k. Only qualified electrical workers may encroach on the minimum approach distances established by AES Generation for working on or near energized apparatus. Encroachment to the minimum approach distance to an energized exposed conductor or apparatus over 600 volts must be by exception only. When working at the minimum approach distance the work must be planned so that the exposure time at the minimum approach distance is kept to a minimum, the worker is in a position from which a slip will not bring a worker into contact with any exposed energized conductor or equipment and an attendant acts as a dedicated observer
l. Workers on electrically isolated apparatus must be protected from re-energizing or back feeding through the use of a Lockout Tagout procedure.
m. Personnel not deemed to be qualified electrical workers must work under the supervision of qualified electrical worker when working even on an isolated circuit.
n. Workers at electric power generation who are exposed to the hazards of flames or electric arcs must not wear clothing that could increase the extent of a flash injury. When workers encroach on the flash protection boundary, they must wear personal protective equipment (PPE) and flame resistant (FR) clothing based on the facility’s flash hazard analysis.
o. Clothing made from the following types of fabrics: polyester, acetate, nylon rayon, spandex and polypropylene (either alone or in blends) can exacerbate burn injuries in the event of an electrical arc fire because they will melt into the skin. These are prohibited unless specifically treated to be flame retardant.
p. Employees shall wear protective equipment for the eyes or face wherever there is danger of injury to the eyes or face from electric arcs or flashes or from flying objects resulting from an electrical explosion, for example when racking in or out a circuit breaker.
q. Please refer to the Tag Out Order Procedure in the AES ROC Safety Manual for the specific requirements involved in the starting, initiation and removal of Tag Out Orders.
4.2 Responsibilities
Management / administrative responsibilitiesResponsibility / Responsible person / Comments
Ensure that all of the electrical hazards are identified and their risks evaluated / Safety Team Leader / The vehicle for identifying these hazards and their associated risks can be a Workplace Risk Assessment
Ensure that all electrical equipment risk control measures are implemented / E&I Maintenance Team Leader / Risk Assessment procedure shall be used to document the implementation of control measures and reassessment of risk after implementation
Ensure that people working in the electrical areas are suitably trained and authorized / E&I Maintenance Team Leader / A detailed authorization procedure, including supporting documents such as checklist of successfully completed activities witnessed, written test etc. See the appendix for the test criteria
Ensure that all tools used for electrical jobs are periodically inspected and maintained / E&I Maintenance Team Leader / Ensure all equipment is registered and has identification reference attached, and approval of inspection and maintenance procedures
Perform periodic inspection and maintenance of tools used for electrical jobs / Electrical Maintenance Engineer / Performance of inspection and maintenance following approved procedures.
Identify any necessary modifications to the electrical single line, schematic, connection and all other diagrams / Any personnel / Use Plant Modification Procedure
Ensure all electrical single line, schematic, connection and all other diagrams are up to date. The latest revisions of these diagrams shall be displayed in their appropriate places as soon as possible. / E&I Maintenance Team Leader
Identify by permanently marking all disconnect switches, circuit breakers, earthing switches, non-load break switches etc. / E&I Maintenance Team Leader
Ensure an up to date Single line diagrams showing the High Voltage and major Low Voltage distribution systems, including the correct service positions of all disconnect switches, bus bar tie breakers, earthing switches, etc. shall be displayed in Central Control Room and all relevant electrical switchgears. / E&I Maintenance Team Leader
Securely fasten a weather and corrosion resistant nameplate or tag to the switch enclosure of all non-load break switches. The tag must indicate that the switch is not to be operated under load and must identify circuit breakers that have to be opened to de-energize the circuit before the switch can be opened safely. / E&I Maintenance Team Leader
Ensures that all contractors, involved in the specific job are qualified and complying with the AES safety policy / Person responsible for the management and administration of the maintenance contract / As per AES ROC safety system contractors cannot work on Low voltage equipments
Ensure that proper PPE is available for operation on electrical breakers. / E&I Maintenance Team Leader
Electrical Maintenance Engineer / Responsible for specifying adequate quantity of PPE for all locations where it is required, ensuring all equipment is registered and has identification reference attached ensuring all Area Engineers and Electrical Maintenance Engineers are trained on the correct use and approval of inspection and maintenance procedures
Performance of inspection and maintenance following approved procedures, update CMMS and record results and training Area Engineers and Electrical Maintenance Engineers on the correct use
Pre-job planning responsibilities
Responsibility / Responsible person / Comments
Ensure that when at all possible work will be carried out on de energized electrical circuits and release the stored energy by closing the earth switch wherever applicable. / Safety Team Leader / The plant safety rules to specify that all work on low voltage electrical systems >50V should be done with the system isolated unless the nature of the work specifically requires the system to be energized (i.e. battery voltage measurement, faultfinding).
Ensure that if work on live electrical systems is required proper risk assessment is done before carrying out the job. / Safety Team Leader / The plant safety rules should specify that a Risk Assessment is required for all live work on low voltage electrical systems.
CRE must ensure the proper isolation of the equipment as per AES LOTO system. / Control Room Engineer / Follow plant LOTO procedure
Ensure to verify the isolations before accepting the work permit / Electrical Maintenance Engineer / Follow plant LOTO procedure
Must ensure that the person accepting the specific job is qualified for electrical maintenance work. / Safety Team Leader / Control Room Engineers to receive a list of all authorized persons for reference during safety document issue process
Ensure to release the stored energy before commencing the work and perform any verification tests necessary to ensure this. / Area Engineer
Electrical Maintenance Engineer / Follow plant LOTO procedure if it states that operations shall remove all system related hazards before issuing safety document
Used to confirm electrical system is de-energized following verification of isiolations
Ensure that proper PPE is used during operation on electrical breakers. / Area Engineer / All should be trained on the correct use of this PPE
Area Engineer should witness the HV detector test and applying the temporary earth by the electrical craft person after accepting the permit for any work to be carried out under the Tag Out Order involves work on exposed electrical conductors that have a rated voltage of greater than 50V. / Area Engineer / The safety document procedure needs to describe the voltage of the equipment where temporary earths are required (normally this is on HV systems only). Also the method of recording the signature of the Area Engineer needs to be clear, whether the temporary earth is applied before or after the issue of the safety document
5. Safety precautions for work on or near High Voltage equipment