Hazards and Preventive Measures at Electrical Facilities

The many components making up electrical installations exhibit varying degrees of robustness. Regardless of their inherent fragility, however, they must all operate reliably under rigorous conditions. Unfortunately, even under the best circumstances, electrical equipment is subject to failures that may result in human injury or material damage.

Safe operation of electrical installations is the result of good initial design, not the mere retrofitting of safety systems. This is a corollary of the fact that while current flows at the speed of light, all electromechanical and electronic systems exhibit reaction latencies, caused primarily by thermal inertia, mechanical inertia and maintenance conditions. These latencies, whatever their origins, are sufficiently lengthy to allow humans to be injured and equipment damaged (Lee, Capelli-Schellpfeffer and Kelly 1994; Lee, Cravalho and Burke 1992; Kane and Sternheim 1978).

It is essential that equipment be installed and maintained by qualified personnel. Technical measures, it should be emphasized, are necessary both to ensure the safe operation of installations and to protect humans and equipment.

Introduction to electrical hazards

Proper operation of electrical installations requires that machinery, equipment, and electrical circuits and lines be protected from hazards caused by both internal (i.e., arising within the installation) and external factors (Andreoni and Castagna 1983).

Internal causes include:

• overvoltages

• short circuits

• modification of the current’s wave-form

• induction

• interference

• overcurrents

• corrosion, leading to electrical current leakages to ground

• heating of conducting and insulating materials, which may result in operator burns, emissions of toxic gases, component fires and, in flammable atmospheres, explosions

• leaks of insulating fluids, such as oil

• generation of hydrogen or other gases which may lead to the formation of explosive mixtures.

Each hazard-equipment combination requires specific protective measures, some of which are mandated by law or internal technical regulations. Manufacturers have a responsibility to be aware of specific technical strategies capable of reducing risks.

External causes include:

• mechanical factors (falls, bumps, vibration)

• physical and chemical factors (natural or artificial radiation, extreme temperatures, oils, corrosive liquids, humidity)

• wind, ice, lightning

• vegetation (trees and roots, both dry and wet)

• animals (in both urban and rural settings); these may damage the power-line insulation, and so cause short circuits or false contacts

and, last but not least,

• adults and children who are careless, reckless or ignorant of risks and operating procedures.

Other external causes include electromagnetic interference by sources such as high-voltage lines, radio receivers, welding machines (capable of generating transient overvoltages) and solenoids.

The most frequently encountered causes of problems arise from malfunctioning or non-standard:

• mechanical, thermal or chemical protective equipment
• ventilation systems, machine cooling systems, equipment, lines or circuits
• coordination of insulators used in different parts of the plant
• coordination of fuses and automatic circuit-breakers.

A single fuse or automatic circuit-breaker is incapable of providing adequate protection against overcurrent on two different circuits. Fuses or automatic circuit breakers can provide protection against phase-neutral failures, but protection against phase-ground failures requires automatic residual-current circuit-breakers.

• use of voltage relays and dischargers to coordinate protective systems
• sensors and mechanical or electrical components in the installation’s protective systems
• separation of circuits at different voltages (adequate air gaps must be maintained between conductors; connections should be insulated; transformers should be equipped with grounded shields and suitable protection against overvoltage, and have fully segregated primary and secondary coils)
• colour codes or other suitable provisions to avoid misidentification of wires
• mistaking the active phase for a neutral conductor results in electrification of the equipment’s external metallic components
• protective equipment against electromagnetic interference.

These are particularly important for instrumentation and lines used for data transmission or the exchange of protection and/or controlling signals. Adequate gaps must be maintained between lines, or filters and shields used. Fibre-optic cables are sometimes used for the most critical cases.

The risk associated with electrical installations increases when the equipment is subjected to severe operating conditions, most commonly as a result of electrical hazards in humid or wet environments.

The thin liquid conductive layers that form on metallic and insulating surfaces in humid or wet environments create new, irregular and dangerous current pathways. Water infiltration reduces the efficiency of insulation, and, should water penetrate the insulation, it can cause current leakages and short circuits. These effects not only damage electrical installations but greatly increase human risks. This fact justifies the need for special standards for work in harsh environments such as open-air sites, agricultural installations, construction sites, bathrooms, mines and cellars, and some industrial settings.

Equipment providing protection against rain, side-splashes or full immersion is available. Ideally, the equipment should be enclosed, insulated and corrosion proof. Metallic enclosures must be grounded. The mechanism of failure in these wet environments is the same as that observed in humid atmospheres, but the effects may be more severe.

Electrical hazards in dusty atmospheres

Fine dusts that enter machines and electrical equipment cause abrasion, particularly of mobile parts. Conducting dusts may also cause short circuits, while insulating dusts may interrupt current flow and increase contact resistance. Accumulations of fine or coarse dusts around equipment cases are potential humidity and water reservoirs. Dry dust is a thermal insulator, reducing heat dispersion and increasing local temperature; this may damage electrical circuits and cause fires or explosions.

Water- and explosion-proof systems must be installed in industrial or agricultural sites where dusty processes are carried out.

Electrical hazards in explosive atmospheres or at sites containing explosive materials

Explosions, including those of atmospheres containing explosive gases and dusts, may be triggered by opening and closing live electrical circuits, or by any other transient process capable of generating sparks of sufficient energy.

This hazard is present in sites such as:

• mines and underground sites where gases, especially methane, may accumulate
• chemical industries
• lead-battery storage rooms, where hydrogen may accumulate
• the food industry, where natural organic powders may be generated
• the synthetic materials industry
• metallurgy, especially that involving aluminium and magnesium.

Where this hazard is present, the number of electrical circuits and equipment should be minimized—for example, by removing electrical motors and transformers or replacing them with pneumatic equipment. Electrical equipment which cannot be removed must be enclosed, to avoid any contact of flammable gases and dusts with sparks, and a positive-pressure inert-gas atmosphere maintained within the enclosure. Explosion-proof enclosures and fireproof electrical cables must be used where there is the possibility of explosion. A full range of explosion-proof equipment has been developed for some high-risk industries (e.g., the oil and chemical industries).

Because of the high cost of explosion-proof equipment, plants are commonly divided into electrical hazard zones. In this approach, special equipment is used in high-risk zones, while a certain amount of risk is accepted in others. Various industry-specific criteria and technical solutions have been developed; these usually involve some combination of grounding, component segregation and the installation of zoning barriers.

Equipotential Bonding

If all the conductors, including the earth, that can be touched simultaneously were at the same potential, there would be no danger to humans. Equipotential bonding systems are an attempt to achieve this ideal condition (Andreoni and Castagna 1983; Lee, Cravalho and Burke 1992).

In equipotential bonding, every exposed conductor of non-transmission electrical equipment and every accessible extraneous conductor in the same site are connected to a protective grounded conductor. It should be recalled that while the conductors of non-transmission equipment are dead during normal operation, they may become live following insulation failure. By decreasing the contact voltage, equipotential bonding prevents metallic components from reaching voltages that are hazardous to both humans and equipment.

In practice, it may prove necessary to connect the same machine to the equipotential bonding grid at more than one point. Areas of poor contact, due, for example, to the presence of insulators such as lubricants and paint, should be carefully identified. Similarly, it is good practice to connect all the local and external service piping (e.g., water, gas and heating) to the equipotential bonding grid.

Grounding

In most cases, it is necessary to minimize the voltage drop between the installation’s conductors and the earth. This is accomplished by connecting the conductors to a grounded protective conductor.

There are two types of ground connections:

• functional grounds—for example, grounding the neutral conductor of a three-phase system, or the midpoint of a transformer’s secondary coil
• protective grounds—for example, grounding every conductor on a piece of equipment. The object of this type of grounding is to minimize conductor voltages by creating a preferential path for fault currents, especially those currents likely to affect humans.

Under normal operating conditions, no current flows through ground connections. In the event of accidental activation of the circuit, however, the current flow through the low-resistance grounding connection is high enough to melt the fuse or the ungrounded conductors.

The maximum fault voltage in equipotential grids allowed by most standards is 50 V for dry environments, 25 V for wet or humid environments and 12 V for medical laboratories and other high-risk environments. Although these values are only guidelines, the necessity of ensuring adequate grounding in workplaces, public spaces and especially residences, should be emphasized.

The efficiency of grounding depends primarily on the existence of high and stable ground leakage currents, but also on adequate galvanic coupling of the equipotential grid, and the diameter of the conductors leading to the grid. Because of the importance of ground leakage, it must be evaluated with great accuracy.

Ground  connections  must  be  as  reliable  as  equipotential grids, and their proper operation must be verified on a regular basis.

As the earth resistance increases, the potential of both the grounding conductor and the earth around the conductor approaches that of the electrical circuit; in the case of the earth around the conductor, the potential generated is inversely proportional to the distance from the conductor. In order to avoid dangerous step voltages, ground conductors must be properly shielded and set in the ground at adequate depths.

As an alternative to equipment grounding, standards allow for the use of double-insulated equipment. This equipment, recommended for use in residential settings, minimizes the chance of insulation failure by providing two separate insulation systems. Double-insulated equipment cannot be relied upon to adequately protect against interface failures such as those associated with loose but live plugs, since some countries’ plug and wall-socket standards do not address the use of such plugs.

Circuit-breakers

The surest method of reducing electrical hazards to humans and equipment is to minimize the duration of the fault current and voltage increase, ideally before the electrical energy has even begun to increase. Protective systems in electrical equipment usually incorporate three relays: a residual-current relay to protect against failure towards ground, a magnetic relay and a thermal relay to protect against overloads and short circuits.

In residual-current circuit-breakers, the conductors in the circuit are wound around a ring which detects the vector sum of the currents entering and exiting the equipment to be protected. The vector sum is equal to zero during normal operation, but equals the leakage current in cases of failure. When the leakage current reaches the breaker’s threshold, the breaker is tripped. Residual-current circuit-breakers can be tripped by currents as low as 30 mA, with latencies as low as 30 ms.

The maximum current that can be safely carried by a conductor is a function of its cross-sectional area, insulation and installation. Overheating will result if the maximum safe load is exceeded or if heat dissipation is limited. Overcurrent devices such as fuses and magneto-thermal circuit-breakers automatically break the circuit if excessive current flow, ground faults, overloading or short circuits occur. Overcurrent devices should interrupt the current flow when it exceeds the conductor’s capacity.

Selection of protective equipment capable of protecting both personnel and equipment is one of the most important issues in the management of electrical installations and must take into account not only the current-carrying capacity of conductors but also the characteristics of the circuits and the equipment connected to them.

Special high-capacity fuses or circuit-breakers must be used on circuits carrying very high current loads.

Fuses

Several types of fuse are available, each designed for a specific application. Use of the wrong type of fuse or of a fuse of the wrong capacity may cause injury and damage equipment. Overfusing frequently results in overheated wiring or equipment, which in turn may cause fires.

Before replacing fuses, lock out, tag and test the circuit, to verify that the circuit is dead. Testing can save lives. Next, identify the cause of any short circuits or overloads, and replace blown fuses with fuses of the same type and capacity. Never insert fuses in a live circuit.

Circuit-breakers

Although circuit-breakers have long been used in high-voltage circuits with large current capacities, they are increasingly used in many other kinds of circuits. Many types are available, offering a choice of immediate and delayed onset and manual or automatic operation.

Circuit-breakers fall into two general categories: thermal and magnetic.

Thermal circuit-breakers react solely to a rise of temperature. Variations in the circuit-breaker’s ambient temperature will therefore affect the point at which the breaker is tripped.

Magnetic circuit-breakers, on the other hand, react solely to the amount of current passing through the circuit. This type of breaker is preferable where wide temperature fluctuations would require overrating the circuit-breaker, or where the breaker is frequently tripped.

In the case of contact with lines carrying high current loads, protective circuits cannot prevent personal injury or equipment damage, as they are designed only to protect power-lines and systems from excess current flow caused by faults.

Because of the resistance of the contact with the earth, the current passing through an object simultaneously contacting the line and the earth will usually be less than the tripping current. Fault currents flowing through humans may be further reduced by body resistance to the point where they do not trip the breaker, and are therefore extremely dangerous. It is virtually impossible to design a power system that would prevent injury or damage to any object that faults the power lines while remaining a useful energy transmission system, as the trip thresholds for the relevant circuit protection devices are well above the human hazard level.

Standards and Regulations

The framework of international standards and regulations is illustrated in figure 1 (Winckler 1994). The rows correspond to the geographic scope of the standards, either worldwide (international), continental (regional) or national, while the columns correspond to the standards’ fields of application. The IEC and the International Organization for Standardization (ISO) both share an umbrella structure, the Joint Presidents Coordinating Group (JPCG); the European equivalent is the Joint Presidents Group (JPG).

Figure 1. The framework of international standards and regulations

Each standardization body holds regular international meetings. The composition of the various bodies reflects the development of standardization.

The Comité européen de normalisation électrotechnique (CENELEC) was created by the electrical engineering committees of the countries signing the 1957 Rome Treaty establishing the European Economic Community. The six founding members were later joined by the members of the European Free Trade Association (EFTA), and CENELEC in its present form dates from 13 February, 1972.

In contrast to the International Electrotechnical Commission (IEC), CENELEC focuses on the implementation of international standards in member countries rather than on the creation of new standards. It is particularly important to recall that while the adoption of IEC standards by member countries is voluntary, adoption of CENELEC standards and regulations is obligatory in the European Union. Over 90% of CENELEC standards are derived from IEC standards, and over 70% of them are identical. CENELEC’s influence has also attracted the interest of Eastern European countries, most of which became affiliated members in 1991.

The International Association for Testing and Materials, the forerunner of the ISO, as it is known today, was founded in 1886 and was active until The First World War, after which it ceased to function as an international association. Some national organizations, like the American Society for Testing and Materials (ASTM), survived. In 1926, the International Standards Association (ISA) was founded in New York and was active until The Second World War. The ISA was replaced in 1946 by the ISO, which is responsible for all fields except electrical engineering and telecommunications. The Comité européen de normalisation (CEN) is the European equivalent of the ISO and has the same function as CENELEC, although only 40% of CEN standards are derived from ISO standards.

The current wave of international economic consolidation creates a need for common technical databases in the field of standardization. This process is presently under way in several parts of the world, and it is likely that new standardization bodies will evolve outside of Europe. CANENA is a regional standardization body created by the North American Free Trade Agreement (NAFTA) countries (Canada, Mexico and the United States). Wiring of premises in the US is governed by the National Electrical Code, ANSI/NFPA 70-1996. This Code is also in use in several other countries in North and South America. It provides installation requirements for premises wiring installations beyond the point of connection to the electric utility system. It covers installation of electric conductors and equipment within or on public and private buildings, including mobil homes, recreational vehicles, and floating buildings, stock yards, carnivals, parking and other lots, and industrial substations. It does not cover installations in ships or watercraft other than floating buildings—railway rolling stop, aircraft, or automotive vehicles. The National Electric Code also does not apply to other areas that are normally regulated by the National Electrical Safety Code, such as installations of communications utility equipment and electric utility installations.

European and American Standards for the Operation of Electrical Installations

The European Standard EN 50110-1, Operation of Electrical Installations (1994a) prepared by CENELEC Task Force 63-3, is the basic document that applies to the operation of and work activities on, with or near electrical installations. The standard sets the minimum requirements for all CENELEC countries; additional national standards are described in separate subparts of the standard (EN 50110-2).

The standard applies to installations designed for the generation, transmission, conversion, distribution and use of electrical power, and operating at commonly encountered voltage levels. Although typical installations operate at low voltages, the standard also applies to extra-low and high-voltage installations. Installations may be either permanent and fixed (e.g., distribution installations in factories or office complexes) or mobile.

Safe operation and maintenance procedures for work on or near electrical installations are set out in the standard. Applicable work activities include non-electrical work such as construction near overhead lines or underground cables, in addition to all types of electrical work. Certain electrical installations, such as those on board aircraft and ships, are not subject to the standard.

The equivalent standard in the United States is the National Electrical Safety Code (NESC), American National Standards Institute (1990). The NESC applies to utility facilities and functions from the point of generation of electricity and communication signals, through the transmission grid, to the point of delivery to a customer’s facilities. Certain installations, including those in mines and ships, are not subject to the NESC. NESC guidelines are designed to ensure the safety of workers engaged in the installation, operation or maintenance of electric supply and communication lines and associated equipment. These guidelines constitute the minimum acceptable standard for occupational and public safety under the specified conditions. The code is not intended as a design specification or an instruction manual. Formally, the NESC must be regarded as a national safety code applicable to the United States.

The extensive rules of both the European and American standards provide for the safe performance of work on electrical installations.

The European Standard (1994a)

Definitions

The standard provides definitions only for the most common terms; further information is available in the International Electrotechnical Commission (1979). For the purposes of this standard, electrical installation refers to all equipment involved in the generation, transmission, conversion, distribution and use of electrical energy. This includes all energy sources, including batteries and capacitors (ENEL 1994; EDF-GDF 1991).

Basic principles

Safe operation: The basic principle of safe work on, with or near an electrical installation is the need to assess the electrical risk before commencing work.

Personnel: The best rules and procedures for work on, with or near electrical installations are of no value if workers are not thoroughly conversant with them and do not comply strictly with them. All personnel involved in work on, with or near an electrical installation shall be instructed in the safety requirements, safety rules and company policies applicable to their work. Where the work is long or complex, this instruction shall be repeated. Workers shall be required to comply with these requirements, rules and instructions.

Organization: Each electrical installation shall be placed under the responsibility of the designated person in control of the electrical installation. In cases of undertakings involving more than one installation, it is essential that the designated persons in control of each installation cooperate with each other.

Each work activity shall be the responsibility of the designated person in control of the work. Where the work comprises sub-tasks, persons responsible for the safety of each sub-task will be designated, each reporting to the coordinator. The same person can act as the designated person in control of the work and the designated person in control of the electrical installation.

Communication: This includes all means of information transmission between persons, i.e., spoken word (including telephones, radio and speech), writing (including fax) and visual means (including instrument panels, video, signals and lights).

Formal notification of all information necessary for the safe operation of the electrical installation, e.g., network arrangements, switchgear status and the position of safety devices, shall be given.

Worksite: Adequate working space, access and lighting shall be provided at electrical installations on, with or near which any work is to be carried out.

Tools, equipment and procedures: Tools, equipment and procedures shall comply with the requirements of relevant European, national and international standards, where these exist.

Drawings and reports: The installation’s drawings and reports shall be up to date and readily available.

Signage: Adequate signage drawing attention to specific hazards shall be displayed as needed when the installation is operating and during any work.

Standard operating procedures

Operating activities: Operating activities are designed to change the electrical state of an electrical installation. There are two types:

• operations intended to modify the electrical state of an electrical installation, e.g., in order to use equipment, connect, disconnect, start or stop an installation or section of an installation to carry out work. These activities may be carried out locally or by remote control.
• disconnecting before or reconnecting after dead-working, to be carried out by qualified or trained workers.

Functional checks: This includes measurement, testing and inspection procedures.

Measurement is defined as the entire range of activities used to collect physical data in electrical installations. Measurement shall be carried out by qualified professionals.

Testing includes all activities designed to verify the operation or electrical, mechanical or thermal condition of an electrical installation. Testing shall be carried out by qualified workers.

Inspection is verification that an electrical installation conforms to applicable specified technical and safety regulations.

Work procedures

General: The designated person in control of the electrical installation and the designated person in control of the work shall both ensure that workers receive specific and detailed instructions before starting the work, and on its completion.

Before the start of work, the designated person in control of the work shall notify the designated person in control of the electrical installation of the nature, site and consequences to the electrical installation of the intended work. This notification shall be given preferably in writing, especially when the work is complex.

Work activities can be divided into three categories: dead-working, live-working and work in the vicinity of live installations. Measures designed to protect against electrical shocks, short circuits and arcing have been developed for each type of work.

Induction: The following precautions shall be taken when working on electrical lines subject to current induction:

• grounding at appropriate intervals; this reduces the potential between conductors and earth to a safe level
• equipotential bonding of the worksite; this prevents workers from introducing themselves into the induction loop.

Weather conditions: When lightning is seen or thunder heard, no work shall be started or continued on outdoor installations or on indoor installations directly connected to overhead lines.

Dead-working

The following basic work practices will ensure that the electrical installations at the worksite remain dead for the duration of the work. Unless there are clear contraindications, the practices should be applied in the order listed.

Complete disconnection: The section of the installation in which the work is to be carried out shall be isolated from all sources of current supply, and secured against reconnection.

Securing against reconnection: All circuit-breaking devices used to isolate the electrical installation for the work shall be locked out, preferably by locking the operating mechanism.

Verification that the installation is dead: The absence of current shall be verified at all poles of the electrical installation at or as near as practicable to the worksite.

Grounding and short-circuiting: At all high- and some low-voltage worksites, all parts to be worked on shall be grounded and short-circuited after they have been disconnected. Grounding and short-circuiting systems shall be connected to the earth first; the components to be grounded must be connected to the system only after it has been earthed. As far as practical, the grounding and short-circuiting systems shall be visible from the worksite. Low- and high-voltage installations have their own specific requirements. At these types of installation, all sides of the worksites and all conductors entering the site must be grounded and short-circuited.

Protecting against adjacent live parts: Additional protective measures are necessary if parts of an electrical installation in the vicinity of the worksite cannot be made dead. Workers shall not commence work before receiving permission to do so from the designated person in control of the work, who in turn must receive authorization from the designated person in control of the electrical installation. Once the work has been completed, workers shall leave the worksite, tools and equipment shall be stored, and grounding and short-circuiting systems removed. The designated person in control of the work shall then notify the designated person in control of the electrical installation that the installation is available for reconnection.

Live-working

General: Live-working is work carried out within a zone in which there is current flow. Guidance for the dimensions of the live-working zone can be found in standard EN 50179. Protective measures designed to prevent electric shocks, arcing and short circuits shall be applied.

Training and qualification: Specific training programmes shall be established to develop and maintain the ability of qualified or trained workers to perform live-working. After completing the programme, workers will receive a qualification rating and authorization to perform specific live-work on specific voltages.

Maintenance of qualifications: The ability to carry out live-working shall be maintained by either practice or new training.

Work techniques: Currently, there are three recognized techniques, distinguished by their applicability to different types of live parts and the equipment required to prevent electric shocks, arcing and short circuits:

• hot-stick working
• insulating-glove working
• bare-hand working.

Each technique requires different preparation, equipment and tools, and selection of the most appropriate technique will depend on the characteristics of the work in question.

Tools and equipment: The characteristics, storage, maintenance, transportation and inspection of tools, equipment and systems shall be specified.

Weather conditions: Restrictions apply to live-working in adverse weather conditions, since insulating properties, visibility and worker mobility are all reduced.

Work organization: The work shall be adequately prepared; written preparation shall be submitted in advance for complex work. The installation in general, and the section where the work is to be carried out in particular, shall be maintained in a condition consistent with the preparation required. The designated person in control of the work shall inform the designated person in control of the electrical installation of the nature of the work, the site in the installation at which the work will be performed, and the estimated duration of the work. Before work begins, workers shall have the nature of the work, the relevant safety measures, the role of each worker, and the tools and equipment to be used explained to them.

Specific practices exist for extra-low-voltage, low-voltage, and high-voltage installations.

Work in the vicinity of live parts

General: Work in the vicinity of live parts with nominal voltages above 50 VAC or 120 VDC shall be performed only when safety measures have been applied to ensure that live parts cannot be touched or that the live zone cannot be entered. Screens, barriers, enclosures or insulating coverings may be used for this purpose.

Before the work starts, the designated person in control of the work shall instruct the workers, particularly those unfamiliar with work in the vicinity of live parts, on the safety distances to be observed on the worksite, the principal safety practices to follow, and the need for behaviour that ensures the safety of the entire work crew. Worksite boundaries shall be precisely defined and marked and attention drawn to unusual working conditions. This information shall be repeated as needed, particularly after changes in working conditions.

Workers shall ensure that no part of their body nor any object enters the live zone. Particular care shall be taken when handling long objects, for example, tools, cable ends, pipes and ladders.

Protection by screens, barriers, enclosures or insulating coverings: The selection and installation of these protective devices shall ensure sufficient protection against predictable electrical and mechanical stressors. The equipment shall be suitably maintained and kept secured during the work.

Maintenance

General: The purpose of maintenance is to maintain the electrical installation in the required condition. Maintenance may be preventive (i.e., carried out on a regular basis to prevent breakdowns and keep equipment in working order) or corrective (i.e., carried out to replace defective parts).

Maintenance work can be divided into two risk categories:

• work involving the risk of electrical shock, where procedures applicable to live-working and work in the vicinity of live parts must be followed
• work where equipment design allows some maintenance work to be performed in the absence of full live-working procedures

Personnel: Personnel who are to carry out the work shall be adequately qualified or trained and shall be provided with appropriate measuring and testing tools and devices.

Repair work: Repair work consists of the following steps: fault location; fault rectification and/or replacement of components; recommissioning of the repaired section of the installation. Each of these steps may require specific procedures.

Replacement work: In general, fuse replacement in high-voltage installations shall be performed as dead-work. Fuse replacement shall be performed by qualified workers following appropriate work procedures. The replacement of lamps and removable parts such as starters shall be carried out as dead-work. In high-voltage installations, repair procedures shall also apply to replacement work.

Training of Personnel about Electrical Hazards

Effective work organization and safety training is a key element in every successful organization, prevention programme and occupational health and safety programme. Workers must have proper training to do their jobs safely and efficiently.

The responsibility for implementing employee training rests with management. Management must recognize that employees must perform at a certain level before the organization can achieve its objectives. In order to achieve these levels, worker training policies and, by extension, concrete training programmes must be established. Programmes should include training and qualification phases.

Live-working programmes should include the following elements:

Training: In some countries, programmes and training facilities must be formally approved by a live-working committee or similar body. Programmes are based primarily on practical experience, complemented by technical instruction. Training takes the form of practical work on indoor or outdoor model installations similar to those on which actual work is to be performed.

Qualifications: Live-working procedures are very demanding, and it is essential to use the right person at the right place. This is most easily achieved if qualified personnel of different skill levels are available. The designated person in control of the work should be a qualified worker. Where supervision is necessary, it too should be carried out by a qualified person. Workers should work only on installations whose voltage and complexity corresponds to their level of qualification or training. In some countries, qualification is regulated by national standards.

Finally, workers should be instructed and trained in essential life-saving techniques. The reader is referred to the chapter on first-aid for further information.

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