Metal Clad Switchgear Maintenance and Safe Handling Guidelines
3 Definitions and Abbreviations
4 Potential Problems with Switchgear
5 Safe Operating and Maintenance Guidelines
Metal Clad Switchgear Maintenance and Safe Handling Guidelines
1 Introduction Metal Clad Switchgear
The purpose of this article is to provide the essential safety guidance to the operation and maintenance personnel working on metal clad switchgear.
This is intended to give general guidelines of the practical safe working environment for employees relative to the hazards arising from working on metal clad switchgear. It is also intended to address electrical safety requirements for employee workplaces during the operation and maintenance of switchgear.
2 References Metal Clad Switchgear
Industry Codes and Standards
National Fire Protection Agency
NFPA 70E Standard for Electrical Safety in the Workplace
International of Electrical and Electronics Engineers (IEEE)
IEEE STD 902 – 1998 Guide for Maintenance, Operation, and Safety of Industrial and Commercial Power Systems
3 Definitions And Abbreviations
Arc Flash: a rapid release of electrical energy due to an arcing fault between electrical phases, neutral or ground, resulting in a plasma arc through the adjacent surrounding air. An arc flash is sometimes inappropriately called a “flashover.”
Arc Flash Hazard: A dangerous condition associated with the release of energy caused by an electric arc.
Arc Flash Suit: A complete flame resistant clothing and equipment system that covers the entire body. This includes pants/bib, jacket, and beekeeper-type head protection hood fitted with a face shield.
Electrical Safety: recognizing hazards associated with the use of electrical energy and taking precautions so that hazards do not cause injury or death.
Flame-Resistant (FR), Flame Resistant Clothing (FRC): Materials or clothing with the inherent characteristic that combustion is prevented, terminated, or inhibited following the application of a flaming or non-flaming source of ignition, with or without subsequent removal of the ignition source.
Limited Approach Boundary: An approach limit at a distance from an exposed energized electrical conductor or circuit part within which a shock hazard exists.
4. Potential Problems with Switchgear
4.1 Protection from Electrical Hazards
The incoming electrical supply to any premises which requires a high voltage supply often passes through switchgear. Switchgear is generally located in substations and varies in size, age, appearance, and operation and maintenance steps.
Switchgear failure is low, but, when it happens it is likely to be catastrophic, with a high probability rate of damage, and possibility of personal injury. Accident experience has shown that failure usually occurs at, or shortly after, operation of the equipment. Thus, the way switchgear is operated, its condition and the circumstances existing in the system at the time of operation, to a large extent, determines whether the equipment will safely perform its duty.
Personnel should understand the nature and consequences of electrical hazards and the reasons for practicing electrical safety.
It is important to understand the four main phases of protection from electrical hazards:
1) Electrical installations should be designed and constructed to be safe by complying with the criteria of recognized and generally accepted good engineering practices and following company and vendor tolerances.
2) The integrity of electrical equipment shall be maintained with particular emphasis on enclosures, insulation, operating mechanisms, grounding, and circuit protective devices.
3) Electrical equipment shall be placed in an electrically safe work condition before personnel work on or near it. Safe practices shall be used to establish an electrically safe work condition.
4) Safe work practices and adequate protective equipment, tools, and test equipment shall be understood and used when it is not feasible to establish an electrically safe work condition, or when de-energizing would create a greater hazard of another kind.
4.2 Typical Hazardous Tasks in Electrical Work
The following tasks are some examples of possible exposure to energized conductors:
Measuring, testing, and probing electrical system components
Opening electrical equipment enclosure doors or removing covers;
Inserting or pulling fuses;
Drilling, or otherwise penetrating, earth, walls, or floors;
Lifting leads or applying jumpers in control circuits;
Installing or removing temporary grounds;
Operating switches or circuit breakers;
4.3 Examples of Activities which Involve Arc Flash Risks
Racking in or out of draw-out circuit breakers
Removing or installing circuit breakers or fuses
Working on control circuits with exposed energized primary parts
Applying safety grounds
Removing panel covers for inspections or other activities
Low voltage testing and diagnostics
Conducting any action deviating from safe and approved steps
Switchgear equipment energizing or de-energizing
5. Safe Operating and Maintenance Guidelines
Well-designed enclosures and proper clearances protect employees under normal and most abnormal operating conditions. Proper maintenance of electrical equipment can reestablish system condition as the equipment ages. It should always be remembered, however, that when it is necessary for personnel to enter electrical equipment enclosures, many of the protective barriers that the design and initial installation have provided may have to be removed. In these cases, electrical safe practices that are appropriate to the task should be used.
It is important that facilities and systems be initially designed and installed in such a manner as to provide for all personnel a safe workplace, free from exposure to electrical hazards. This should cover the following concerns:
Maintenance (breakdown and preventive)
Safety audits of workplace conditions
Technical training and qualifications of personnel
A technical authority to respond to questions or concerns about design and installation.
Electrical equipment should be designed with adequate working spaces both within the equipment and around it. Installations in cramped spaces or areas where accessibility is difficult should be avoided, working on such systems needs extra care and precautions. A system properly designed to optimize reliability & maintainability should also optimize safety, productivity and cost at the same time.
Working on or near exposed energized electrical parts in cramped spaces is especially dangerous because reflex reactions, from bumping into objects, could cause a person to involuntarily contact the energized parts and receive a shock or instigate a flash. Dimensions for access to, and clearances around, electrical equipment are given in SAES-P-116.
5.1 Qualified vs. Unqualified Persons
The terms qualified and unqualified are often misunderstood. Some people think that to be electrical safety qualified, one must be a fully qualified electrician who has had a long list of electrical training courses. In reality, a person may be electrical safety qualified to perform only a limited number of tasks on or near specified electrical equipment. Qualified persons shall:
Be trained in, and knowledgeable of, the construction and operation of the equipment or a specific work method;
Be trained to recognize and avoid the electrical hazards that might be present with respect to such equipment or work method;
Be familiar with the proper use of special precautionary techniques, personal protective equipment, insulating and shielding materials, and insulated tools and test equipment.
Persons permitted to work on or near exposed conductors and circuit parts must also be trained in and familiar with:
The skills and techniques necessary to distinguish exposed live parts from other parts of electrical equipment.
The skills and techniques necessary to determine the nominal voltage of exposed live parts.
The approach distances specified in the table of NFPA 70E – 1995, Part II, Chapter 2, and the corresponding voltages to which the qualified person will be exposed.
The decision-making process necessary to determine the degree and extent of the hazard and the proper personal protective equipment and job planning necessary to perform the task safely.
5.2 Safe Electrical Work Practices
Safe practices are the most important area of the electrical safety program on which to concentrate. A significantly greater number of injuries and fatalities are the result of poor or careless practices than the result of poor equipment conditions.
Always assume that hazardous voltage is present in switchgear assemblies unless proven to be in an electrically safe work condition as defined in NFPA 70E. This voltage can cause serious injury such as shock or burn, or even cause death. Only qualified persons should be allowed to operate, inspect, or maintain switchgear assemblies.
Here are just a few examples by which maintenance and service personnel might avoid serious injury or death when working around electrical equipment:
Never assume that the electrical equipment is de-energized. A false assumption can lead to serious injury or death. Review the entire operation sequence for disconnecting and grounding with a second knowledgeable person before actually doing the work, and make sure the entire sequence for disconnecting and grounding is in fact followed. A failure to follow the entire operation sequence could lead to serious injury or death. It is the policy of Saudi Aramco that energized electrical equipment shall be properly de-energized, voltage tested, grounded, locked-out and tagged in accordance with GI-0006.012 and local operating instructions prior to being worked on, whenever possible.
Do not assume that any conductor is de-energized. A false assumption can lead to serious injury or death. Confirm that the conductor is de-energized and grounded before you begin work on electrical equipment.
Before any adjustment, servicing, parts replacement or any other act is performed requiring physical contacts with the electrical working components or wiring of the equipment, power must be removed from all sources and all attached rotating equipment (motors, generators, etc.) must have come to a complete stop.
Inspect the equipment for any damage. This includes damage to the enclosure, power panel, control panel and wiring harness. If any damage is found or suspected, report immediately.
Solid insulation surrounding an energized conductor and power apparatus must never be relied upon to provide protection to personnel.
Do not operate/remove any current transformer with secondary terminals open-circuited. Be sure to short-circuit secondary before installing or removing a current transformer.
All spring-charged mechanism related to a breaker must be serviced only by skilled and knowledgeable personnel capable of releasing such spring load in a controlled manner.
Do not attempt to insert the circuit breaker into any circuit breaker compartment prior to inspection of the breaker. Compare breaker nameplate rating with switchgear rating. Verify secondary voltages on the breaker and in the circuit breaker compartment.
Do not attempt to insert a closed circuit breaker.
Always inspect breaker compartment to ensure that it is free of obstructions, tools, or other equipment.
Do not rely on interlocks and other indicators to prevent an accident. Relying on interlocks and indicators are not a substitute for following the entire operation sequence for disconnecting and grounding electrical equipment in order to de-energize and avoid risk of death or serious injury. Interlocks are only a backup.
Unless fully covered by a properly rated arc flash suit or arc rated face shield, personnel shall not wear meltable (plastic) or conductive (metal) glasses, jewelry, rings, watches, metal belt buckles, etc., within the limited approach boundary of energized electrical equipment.
Whenever feasible, remote racking and remote switching devices shall be installed and used. When racking and switching is not being performed remotely, proper personal protective equipment (PPE) shall be worn and bodily exposure to potential arc flash minimized (e.g., by standing as far away from the equipment as possible).
After every activity, make a final inspection to see that no tools, construction materials, or other foreign matter have been left in the switchgear equipment.
“Good” maintenance practices enhance equipment reliability, but too much maintenance is expensive and may be counterproductive to both reliability and safety. To optimize safety one needs to optimize maintenance practices & systems. Maintenance optimization should improve reliability & safety.
5.2.1 General Checks for Circuit Breakers
a) Handle, test, operate, and install circuit breakers in accordance with manufacturer recommendations. For any difficulty, consult manufacturer for support.
b) Prior to installing circuit breakers, ensure that the circuit breaker is in the “Open” position with all springs discharged before inspecting or installing the circuit breaker.
c) Perform a manual open/close operation check of circuit breakers while it is in the racked out position.
d) Remove all tools, lifting assembly, and miscellaneous items left on the circuit breaker before installing the circuit breaker into the circuit breaker compartment.
5.2.2 Racking Circuit Breakers into “Test/Disconnected” Position
Ensure to follow the manufacturer’s instructions for the equipment. The following description is generic:
Ensure that circuit breakers are installed in the appropriate switchgear cubicles. Ensure that the rating of the circuit breaker matches the rating of the cubicle or cell.
Verify that the racking position indicator reads “Test/Disconnected.”
Roll circuit breakers onto the circuit breaker lifting truck and secure in accordance with manufacturer provisions.
Remove the padlock from the door handle, if installed, and open the door.
Install the circuit breaker using the circuit breaker lifting truck, if required. A circuit breaker lifting truck is required to install circuit breakers into top cubicles and lower cubicles for switchgear mounted on a housekeeping pad.
Elevate and align lifting truck and circuit breaker compartment rails. Carefully align the circuit breaker lift truck when installing and removing circuit breakers to prevent damage to components inside of circuit breaker cubicles.
Align the rollers on each side of the circuit breaker with the compartment positioning rails mounted on the side walls of the circuit breaker compartment, and roll the circuit breaker into the cubicle until the front of the circuit breaker lines up with the test position indicator(s).
5.2.3 Racking Circuit Breakers into “Connected” Position
Ensure that the circuit breaker is in the “Open” position. Circuit breakers must be in the “Open” position when racked into or out of the cubicle. Interlock mechanisms allow the racking shaft to rotate only when the circuit breaker is in the “Open” position.
Close the circuit breaker compartment door and remove the padlock from the racking port, if installed. Always keep the circuit breaker compartment door closed when racking the circuit breaker from one position to another while the switchgear is energized.
Open the racking port, insert the racking crank or handle into the port, and engage the handle onto the racking shaft. Keep the racking handle as straight as possible during the racking procedure.
Rotate the racking handle clockwise. If the circuit breaker does not easily rack into the compartment, remove the circuit breaker and repeat steps above steps. If satisfactory results are not achieved, consult the manufacturer for recommendations. Never force the circuit breaker into or out of the circuit breaker compartment. If a mechanism is not operating easily, inspect the equipment and remove any foreign objects or debris.
Continue rotating the racking handle clockwise until the racking position indicator reads “Connected.”
Do not over-torque the racking shaft.
When the racking position indicator reads “Connected,” the circuit breaker is fully racked into the circuit breaker compartment and the circuit breaker’s primary contacts are connected to the bus.
If control power is available, the circuit breaker spring winding motor will operate as soon as the circuit breaker control secondary disconnects operates.
5.2.4 Racking Out Circuit Breaker
Always keep the circuit breaker compartment door closed when racking the circuit breaker from one position to another while the switchgear is energized.
Verify that the circuit breaker is in the “Open” position and check the indicator on the front of the circuit breaker.
Place the racking handle into the racking port and engage the racking shaft.
Rotate the racking handle counterclockwise. If the circuit breaker does not easily rack out of its compartment, reconnect the circuit breaker and repeat the first two steps above. If satisfactory results are not achieved, consult the manufacturer for recommendations.
Continue rotating the racking shaft until the racking position indicator reads “Test/Disconnected.” The racking handle will stop when the final position is reached. Do not over-torque the racking shaft.
5.2.5 Removing Circuit Breakers from Compartments
Open the circuit breaker compartment door.
Inspect breaker indicator to confirm that the circuit breaker is open.
Use the circuit breaker lifting truck to remove the circuit breaker from the circuit breaker compartment.
Move the release handle to release the circuit breaker from the “Test/Disconnected” position. Operate the latch (if provided) to release the circuit breaker from the “test” position. On most designs, it is necessary to trip the circuit breaker before the circuit breaker can be released. If springs are not already discharged, there will be a loud noise as the closing springs discharge when the circuit breaker is withdrawn from the compartment. Charged springs will discharge loudly when the circuit breaker is removed from the compartment.
Move the circuit breaker out of the compartment, and roll the circuit breaker out onto a circuit breaker lifting truck, where required. Secure circuit breakers onto the lifting truck in accordance with manufacturer provisions.
Personnel should be trained to understand the content of the rules, why they exist, and how to implement them in the field. Training on safety-related work practices should cover all personnel, not just persons associated with the electrical end of the business. In this modern day of technology, so-called “unqualified” persons are surrounded by a lot of electrically powered utilization equipment.
Even though they don’t need to know the construction or how things operate internally, they do need to know the possible electrical hazards. Therefore, everyone in the workplace should have sufficient electrical safety training so that they can be qualified to perform their assigned tasks. Part of this qualification should cover the electrical safety aspects of their assignments.
Any individual who would be interacting with the electrical system needs to understand the reasons why he should follow electrical safety-related procedures, standards, and practices so that they will approach such work with the proper attitude.
As requested by GI-0002.721, Saudi Aramco and contractor employees who work on electrical equipment operated at higher than 240 volts shall receive formal safe electrical work training, which includes the following:
Arc flash hazards and prevention of injuries,
Reading and understanding arc flash hazard and task warning signs,
Proper selection, inspection, use of arc flash PPE/FRC, and
Safe work procedures for electrical isolation, switching, voltage testing, etc.
Electrical personnel should also be trained in emergency procedures, such as methods of releasing victims, first aid, and cardiopulmonary resuscitation (CPR), since they might someday have a need for these techniques in their job assignments.
5.4 Personal Protective Equipment (PPE)
Electrical protective equipment serves to eliminate or reduce hazard severity, reduce the likelihood of an accident given that a hazard exists, and reduce the severity of the injury if an accident occurs. The selection of personnel protective equipment should be determined by a hazard analysis that determines the hazard severity and the parts of the body that could be exposed to the hazard.
All body parts exposed to electrical hazards should be protected as a last line of defense from personal injury.
In addition to protective clothing, managing systems can be designed to augment the reduction of hazard exposure. Properly designed labeling and documentation practices serve to communicate and inform people of hazard presence and potential.
Electrical workers who work on electrical equipment operated at higher than 240 volts (e.g., electrical system operators, electricians, Power Distribution and Utilities Department technicians) shall be flame resistant clothing (FRC) that conforms to NFPA 70E Hazard/Risk Category 2 (has a minimum arc flash rating of 8 cal/cm²).
Table 1 shows tasks requiring specific arc flash PPE & insulated tools.
The user shall inspect all personal protective equipment (PPE), including flame resistant clothing (FRC), before each use. Any items that are contaminated or damaged to the extent their protective qualities are impaired shall not be used. PPE/FRC shall be dry during use. Proper eye protection (e.g., safety glasses marked as meeting ANSI Z87.1) shall always be worn under a face shield or arc flash hood.
PPE and FRC garments shall be stored in a manner that prevents physical damage and damage or contamination from moisture, deteriorating agents, flammable materials, etc.
5.4.1 Care and Maintenance of FR Clothing and FR Arc Flash Suits
FR apparel shall be inspected before each use. Work clothing or arc flash suits that are contaminated, or damaged to the extent their protective qualities are impaired, shall not be used. Protective items that become contaminated with grease, oil, or flammable liquids or combustible materials shall not be used.
(b) Manufacturer’s Instructions
The garment manufacturer’s instructions for care and maintenance of FR apparel shall be followed.
FR apparel shall be stored in a manner that prevents physical damage; damage from moisture, dust, or other deteriorating agents; or contamination from flammable or combustible materials.
(d) Cleaning, Repairing, and Affixing Items
When FR clothing is cleaned, manufacturer’s instructions shall be followed to avoid loss of protection. When FR clothing is repaired, the same FR materials used to manufacture the FR clothing shall be used to provide repairs. When, trim, name tags, and/or logos are affixed to FR clothing, guidance in ASTM F 1506, Standard Performance Specification for Textile Material for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards, shall be followed.
5.4.2 Maintenance of Protective Equipment
Personal safety and protective equipment such as the following shall be maintained in a safe working condition:
Rubber gloves, sleeves, and leather protectors
Voltage test indicators
Blanket and similar insulating equipment
Insulating mats and similar insulating equipment protective barriers
External circuit breaker rack-out devices
Safety grounding equipment
Insulated and insulating hand tools
5.4.3 Inspection and Testing of Protective Equipment and Tools
Safety and protective equipment and tools shall be visually inspected for damage and defects before initial use and at intervals thereafter, as service conditions require.
The insulation of protective equipment and protective tools shall be verified by the appropriate test and visual inspection to ascertain that insulating capability has been retained before initial use, and at intervals thereafter, as service conditions and applicable standards and instructions require.
5.4.4 Safety Grounding Equipment
Personal protective ground cable sets shall be inspected for cuts in the protective sheath and damage to the conductors. Clamps and connector strain relief devices shall be checked for tightness. These inspections shall be made at intervals thereafter as service conditions require, but in no case shall the interval exceed 1 year.
Prior to being returned to service, safety grounds that have been repaired or modified shall be tested.
(C) Grounding and Testing Devices
Grounding and testing devices shall be stored in a clean and dry area. Grounding and testing devices shall be properly inspected and tested before each use.
“Your safety depends upon your own actions”