Upload
sayed-nagy
View
19
Download
5
Embed Size (px)
DESCRIPTION
Chapter 2 Introduction to Electrical safety
Citation preview
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
CHAPTER 2Introduction to Electrical safety
1. Electrical hazards and electrical safety
Electrical accidents, unlike most other industrial accidents, quite
often happen to professional and supervisory staff. In some
situations they may be at greater risk than the manual staff. In a
typical year 47% of electrical accidents in factories in Great
Britain involved electrically skilled persons out of a total of 805
reported accidents. These accidents were analyzed according to
types of apparatus and their voltage (see Table 2.1). At the time
of that analysis the then legislation made the distinction between
high voltage and lower voltages at the arbitrary level of 650
volts.
The statistics also related solely to those premises subject to the
Factories Act in Great Britain. Changes to legislation and
administrative changes to the enforcing authorities have changed
the manner in which such accidents are reported and processed
but the accident situation represented will not have substantially
altered.
Much of the apparatus and working practices have changed but
many of the old problems persist and the same electrical
accidents are seen time and time again. Throughout the working
population one may expect this same pattern to be repeated, or
at least to be similar to that shown in Table 2.1. Since only about
one-third of the employed population work in factories, the scope
for electrical accidents per year is considerably larger than is
illustrated here.
2-1
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
Table2.2 analyses those accidents by occupation: 57 accidents
were to supervisory and testing staff, and electrical trades people
accounted for 302 of the total 805 accidents. Tables 2.3-2.5
analyze a year of accidents by location, causation and voltage,
respectively.
2-2
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
Table 2.1 Electrical accidents analyzed by apparatus.
The other points to note about electrical accidents, which may
not be apparent from study of these tables but which, if one
knows about them, may be seen to fit into the patterns shown,
are:
(a) A very large proportion of those accidents to electrical staffs
do not involve electric shock but cause flash and arc burns due to
incorrectly working on live exposed conductors. Too much work is
done live, and by persons who should know better, although they
2-3
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
are as likely as not to have had quite inadequate training in live
work. The law in the UK is now strongly against live working.
Table 2.2 Electrical accidents analyzed by occupation.
Table 2.3 Analysis of reportable electrical accidents by
location in one year.
Table 2.4 Conditions leading up to accidents in one year.
2-4
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
(b) Most electrical fatalities are due to electric shocks at the
lowest distribution voltage of 240 volts (415 volts, 3 phase).
Contrary to some commonly held beliefs, 240 volts is a very
dangerous voltage.
(c) Nearly all electric shocks, even at 240 volts, are potentially
lethal. For every fatality, there have been many narrow escapes
and an even vaster number of minor shocks and ‘tingles’. The
key factors are discussed in Chapter 3, but it depends crucially on
whether the victim is able to ‘let go’ of the live conductors or not.
Mostly the answer is yes, hence the large number of lucky
escapes.
Table 2.5 Reported electrical accidents by a.c. systems in
one year analysis.
2. Control of staff
2-5
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
From time to time, we all make mistakes, but when life and limb
are at risk it is inexcusable to take chances. It would be very sad
to go through the rest of one’s life knowing that someone had
been killed or injured due to one’s own negligence.
Even if one were not distressed at causing pain or death to
others, there is also the legal aspect to consider. Everyone must
conduct their work these days in accordance with statutory
legislation; in particular, in the UK the Health and Safety at Work
etc. Act 1974 and, in the case of electrical hazards, the Electricity
at Work Regulations 1989 apply. These regulations place duties
on all employers, the self-employed and all employees in respect
of work with, on, or near electrical equipment. Even office
workers do not escape the scope of these regulations.
Engineers hold a special place in our society. They not only hold
responsible positions in many industries and institutions but carry
special responsibilities for the safety of work people and for the
public where these engineers are in control of work processes or
activities. As an example, an electrical engineer in charge of the
high voltage testing of a piece of electrical equipment must fully
apprise him or herself of all the potential hazards and risk points
associated with that testing. There must be proper control of the
work and of the persons working on that task. These people must
be properly supervised at all times. The duties are not just legal
ones, they are moral ones too. At root of the whole issue there is
also the financial penalty associated with errors. Accidents can be
very costly indeed.
No one should be allowed to do anything which is likely to be
dangerous unless they have the necessary skill and experience
and the technical knowledge to do the work safely. Managers and
supervisors must therefore satisfy themselves that no one is
2-6
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
asked to do any work for which they are not qualified and
particular care must be taken with trainees and apprentices.
As a first step, an electrical engineer should equip him or herself
with a copy of the Memorandum of Guidance on the
Electricity at Work Regulations (HSE, 1989). This is essential
reading since it reproduces the important regulations and gives a
commentary on them indicating the thinking of the main
enforcement authority, the Health and Safety Executive (HSE).
This memorandum also lists many other relevant and useful
guidance notes and publications. Note also the article by Dolbey
Jones (1989).
3. Permits to work
Much electrical work is done in industry, and particularly so in the
electrical power supply industry, using a system of work and staff
control known as ‘permits to work’. The purpose with most of
these procedures is to control who does what, on what and when,
and to document this in a formal manner.
Generally, the principle is to make the particular piece of
equipment to be worked upon as safe as possible, for example by
making it dead, isolated and earthed. That does not necessarily
mean that all danger would be eliminated in the area of the work.
The permit itself should be written in such a way as to alert
persons to such residual dangers, for example from adjacent live
equipment which is still in service during the work.
When there may be danger, and some electrical work
(particularly in testing and maintenance) cannot be made
absolutely safe, instructions must be precise and unambiguous
and these should be recorded on the permit which should be
issued and, in due course, cancelled, in an orderly and clearly
defined manner. A full record of all permits issued must be kept
2-7
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
so that it is possible, at any time, to find out what is going on,
who is involved or at risk, and what precautions have been taken.
The permit must state clearly and fully to whom it has been
issued (this person should be present at all times and is
responsible for what happens), name those persons who may be
present in the danger area, and state what special precautions
have been taken. The safe and unsafe areas must be stated, and
clearly indicated on the site. The work to be done must be clearly
defined, and no other work must be carried out, because it may
entail risks not contemplated by the person issuing the permit
who therefore may not have taken the necessary extra
precautions.
At the end of the work there must be a clearly defined procedure
for handing over. A check must be made that all persons have
been withdrawn and the result recorded. Before the permit is
cancelled, a statement must be recorded (preferably on the back
of the cancelled permit and also in the log book where one has
been kept) of what work has been done - and what is left undone
- and what steps have been taken to render the site safe for
normal operations. Until the permit has been cancelled the
person to whom it was issued remains responsible for everything
that happens.
If the work lasts for more than one shift there must be an
appropriate method of handing over and ensuring that
the new shift supervisor is familiar with the state of work
and the terms of the permit. It is often preferable to
cancel the first permit and issue a new one. Sometimes
the person with the authority to issue permits takes
charge of the work; in that case he should issue a permit
for himself.
2-8
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
All this detailed procedure may sound very fussy, but experience
has shown that it is essential. The routine not only ensures that
there is a record which should show the cause of any mistake,
but the mere writing down of all the details is a great help in
preventing anything being overlooked. As the persons concerned
must sign all records and statements, the routine helps to ensure
that instructions have been read and understood.
4. Testing and research work etc.
Some testing and research work presents its own hazards. As the
conditions are likely to vary greatly, it is impossible to lay down
rules in detail. What can be said, however, is that the law treats
the activities of testing and research work no differently from any
other activity. The general principles therefore are exactly the
same. In short, there is no special license to work on or near live
conductors (or to allow live conductors to be accessible) simply
because the activity is testing or a necessary part of research
etc.
Routine testing using dangerous voltages is normally carried out
in enclosures having interlocked doors so arranged that the
power supply is completely disconnected and, if the
circumstances require it, the conductors are earthed, before the
person may gain access.
Alternatively, if the testing can be undertaken with a very low
and harmless voltage, for example 12 volts, the need for
enclosure can be dispensed with.
When the equipment under test is so large that interlocked
enclosure is inappropriate, special measures will have to be
devised. The principle of excluding persons from the vicinity of
the equipment while voltage is applied should always be
observed. When voltages above say 1000 volts are involved (i.e.
2-9
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
high voltage) the exclusion of persons from the area becomes
imperative. If the test facility is a permanent one there is no
excuse for persons to have access during testing to conductors
energized at high voltage. The HSE publish guidance in addition
to that mentioned in section 1.2 above (HSE, 1980) on the
subject of safety in electrical testing.
There are some specialized activities where work on live
conductors is commonly accepted practice and where
appropriate precautions have been developed. The official
guidance in HSE (1980, 1989) describes some of these. (Also see
Appendix 1 for further HSE guidance.)
5. Non-electrical causes
Some so-called ‘electrical’ accidents are the result of mechanical
and other causes. Examples of these are mechanical ‘stress-
raisers’, thermal shock on insulators, resonant vibrations of
conductors leading to fractures, low temperature brittleness or
corrosion fatigue. To deal with such troubles it is necessary to
have more than a narrow interest in electrical matters.
The official report on the enquiry into the disastrous explosion
and fire at Flixborough stated that engineers should have
academic and practical training in all branches of engineering,
outside their specialty, which may affect their work. That disaster
was caused by an inappropriate and amateur modification to the
highly complex chemical plant.
The official report of the inquiry by Lord Cullen into the disastrous
explosion and fire on the North Sea oil platform, Piper Alpha, in
1988, in which 167 men died (Cullen, 1990), concluded with a list
of 106 recommendations comprehensively covering the
shortcomings. Of particular importance was the recommendation
for the adoption of Safety Management Systems by the company.
2-10
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
This was to ensure that the design and operation of the
installation was safe.
6. Equipment design
Standards are necessarily very precise about small details of
apparatus to ensure that it is not only safe when leaving the
manufacturers but also remains safe in use and after repairs.
Some of the conditions laid down may appear trivial, but are, in
fact, essential. It is not easy to decide what to specify so as to
attain safety without limiting choice of design.
Some important basic requirements of standards are:
The insulation of conductors shall be unable to come into
contact with moving parts.
Earthing terminals shall be adequately locked against
loosening. These terminals shall not serve for any other
purpose, e.g. for securing parts of the case.
Electrical connections shall be so designed that the contact
pressure is not transmitted through insulating material
other than ceramic or other materials not subject to
shrinkage or deterioration.
Knobs, handles, operating levers and the like, which when
removed or damaged render live points accessible, shall be
of adequate mechanical strength, and shall be so attached
to the shaft that they cannot become detached
inadvertently, even after extensive use. They shall be so
arranged that contact with live shafts cannot be made by
thin metal objects allowed to fall between the knobs and
the case.
Soldered connections shall be so designed that they keep
the conductors in position if the conductor breaks at the
point of connection. Protective insulation shall be securely
2-11
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
fixed in such a way that it cannot be removed without
making the tool unfit for use (e.g. if it were omitted during
repair it would be impossible to reassemble the tool in a
workable condition), and so on.
In many situations it is important that fingers, steel rules or
even knitting needles shall not be able to touch live or
moving parts and a number of probes have been devised to
prevent this, including a standard test finger which is
hinged and can feel round corners.
7. Investigations
Most engineers will, at some time, have to investigate an
accident or plant failure. The first requirement is to make
sure that one has all the relevant information and that it
is correct. Persons who have witnessed a severe accident
are often shocked and emotionally disturbed. They may be
quite unable to distinguish between what they have seen and
what they think they ought to have seen, or, perhaps, what they
have imagined when trying to rationalize their confused
memories. Some people may also have good reason for wanting
to mislead. The person injured is sometimes less upset and a
better witness than the onlookers: for example, a girl who lost
several fingers in a guillotine was much calmer the next day than
others who saw it happen.
It is also important to remember that the impossible does
not happen, and the improbable only happens
occasionally. On the other hand, one should always be
suspicious of an explanation which comes too readily. With
perseverance, the truth can nearly always be found. It is
important to examine the debris very carefully after a
failure and be very critical of stock wiring diagrams; they
frequently have mistakes or refer to the wrong apparatus.
2-12
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
Modifications may not have been recorded. For example, after a
switch-cubicle explosion which had been attributed to ‘a surge’,
on enquiry it was found that no system disturbance had been
noticed anywhere else. On examining the wreckage a severed
conductor showed clear evidence of a fatigue fracture, not
entirely obscured by arcing. The cause of all the trouble, as
checked by calculation, was that the conductor had resonated at
the supply frequency, work hardened, and fractured while
carrying load current.
Having determined how the accident happened, it is
important to find out why. Was the equipment suitable for
its duty? If an accident occurs because someone closed
the wrong switch, it is important to find out why they did
it.
Were they familiar with the job or equipment? Were standing
instructions vague or ambiguous, was the position of the switch
handle misleading, were the circuits confusing, or were the
switches inadequately labeled, etc.?
Temperament is important in some jobs. A control engineer
may have long periods of dull routine punctuated by
occasional emergencies when quick and correct decisions
are necessary. In such a situation, people require enough to do
to keep alert, but not so much that they do not respond instantly
when the emergency arises. The UK Medical Research Council
Applied Psychology Unit has found that a tired man can usually
perform such a job quite as well as a fresh one in normal
conditions, particularly if he has had a great deal of experience,
but may fail to meet an emergency.
8. Report writing
2-13
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
The purpose of an investigation is to ascertain the facts and
achieve any necessary action. Usually a report will be necessary,
and should be presented in clearly written, easily understandable
form. If the report is muddled or unconvincing the time spent on
the investigation will have been wasted. It is useful to consider
the following points when writing a report.
1. Fully understand the sequence of events which led to the
incidence or accident. Arrange the report in a logical
sequence, for example to reflect the chronological sequence
of events. Each paragraph should follow naturally from its
predecessor. Give the report a title, use subheadings and
number the paragraphs.
2. The text should flow, carrying the argument forward and in
such a way that the reader is almost expecting what
follows.
3. Direct the language at the recipient reader. Use language
and terminology which he or she will understand. If
necessary explain special or difficult technical terms in
basic, everyday language.
4. Put detailed technical material in appendices.
5. If the report is long, provide a short and cogent summary.
6. End the report with conclusions. If appropriate then add
recommendations.
7. Sign it and date it.
Much has been written and published on the correct use of
English and a lot of nonsense is talked about what is, and what is
not, allowed. There are actually no rules in English, despite what
the experts may wish one to believe: that is what has made it
such a resilient and successful language!
There are, however, some very useful conventions (which are not
the same as rules) which are helpful to know about. Gowers
2-14
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
(1965, 1987), Jespenson (1943) and Carey (1958) may be of
interest.
9. Developments in engineering
There is an old saying about even the most advanced and up-to-
date pieces of machinery or technology, especially it is said of
modern advanced aero- planes, that they are ‘out of date before
they leave the drawing board’. Even drawing boards are
becoming out of date nowadays, with computers reaching into
every aspect of our lives and, of course, into engineering drawing
offices.
Solid state devices have been with us for many years, nearly half
a century in fact, and their reliability is well established. It is
possible to compute the probable ‘life before failure’ of most
devices. However, this does not help one trace those defective
components which operate only in emergency and could
otherwise remain unused and defective but undetected for years.
It is virtually impossible to detect all weak links with certainty.
Similarly, software can harbors weaknesses which can be
extremely difficult if not impossible to detect. The hazards of
relying on untried software in safety critical systems is
becoming a growing area of concern as our society
assigns more and more control processes to the
microchip.
An associated development has been the increasing use
of fiber optics for the transmission of information and
instructions, and the subsequent development of ‘optical’
switches and relays. These reduce fire and explosion
hazards. They also eliminate the disturbance of control systems
and telecommunications by electrostatic and magnetic induction,
and by gradients in the ground and structures caused by power
2-15
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
faults and lightning discharges. Fiber optics are already well
established as are some optical devices, the latest of which
appears to be a ‘transistor’, and development is rapid at the
present time.
Another important development has been the realization of the
seriousness of the toxic hazards arising from the use of
polychlorinated biphenyl’s, used increasingly from the mid-1950s
to about 1975 or later in place of mineral oil in power
transformers to reduce the danger from fire and explosions.
Oil-less, otherwise referred to as dry or sometimes air-cooled,
transformers have been used to some extent, but, even it not
immersed in an insulating liquid, conventional solid insulation is
itself a fire risk. In addition these transformers are prone to
failure caused by absorbed moisture from the air and from
surface contamination and tracking in industrial situations. Fire
risks due to oil escape are an increasingly important industrial
hazard and the losses have at times amounted to several million
pounds.
There have also been important developments in understanding
the havoc which may be caused in control, telecommunication
and instrumentation systems by electrostatic and
electromagnetic radiation. There has also been much work
carried out on the subject of earth potential gradients caused by
power circuit failures.
10. Legislation and its administration
There have been many developments in the ‘political’ climate. To
understand their significance, particularly in the UK, it is useful to
refer back to the beginning of the organized electrical supply
industry. The period 1880 to 1895 was one of very rapid
development. In 1880 Edison in the USA and Swan in Great
2-16
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
Britain perfected a practical carbon filament electric light bulb.
This was the trigger to a vast electrical industry including central
power supply and electricity distribution systems.
Following these early steps, legislators took an early interest. To
lay mains in the streets in Great Britain, for example, it was
necessary to introduce special legislation. Hence the first Electric
Lighting Act was passed in 1882. In due course this was followed
by numerous modifying and amending Acts. On the safety side
there are two important sets of Regulations.
The first of these was in 1896, the Electricity Supply
Regulations, which were introduced for ‘securing the safety of
the public’ and for ‘ensuring a proper and sufficient supply of
electrical energy’. Dealing with the minimum heights of overhead
power lines, maximum voltages of distribution systems and
maximum permissible leakage currents etc., these Regulations
were very detailed and prescriptive and were administered by the
then Board of Trade. It is interesting therefore that their eventual
successors are still entitled the Electricity Supply Regulations (of
1988 as amended in 1990) and cover many of the same matters
as their earliest predecessors, but refined in many ways through
numerous revisions and amendments down the decades. Their
principle and objectives remain the same; the safety of the public
from the electricity distribution system up to the consumers’
terminals and the preservation of the ‘security of the supply’.
The other set of statutory (i.e. criminal law) Regulations in
Great Britain, which had an early provenance and was directed
solely at electrical safety, was made under the Factories and
Workshops Acts. These were the Electricity Regulations of
1908 and they protected employees working in premises subject
to the Factories and Workshops Acts. They also had many
detailed and specific provisions but their strength lay in some
2-17
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
very generally drafted provisions together with flexible
enforcement by Her Majesty’s Factory Inspectorate (HMFI) over
many decades. They also protected those working in power
stations and in those substations which were ‘large enough to
admit an employee’. These Regulations were amended in
1944 and became known as the Electricity (Factories Act)
Special Regulations 1908 and 1944. However employees
were not protected by this legislation from electrical hazards
arising in the course of their work from the other parts of the
electrical distribution system, e.g. working on cables in the street.
This was not fully redressed until 1989 when the 1908 and 1944
Regulations were finally revoked and replaced by the more
comprehensive Electricity at Work Regulations 1989 which were
made under the Health and Safety at Work etc. Act 1974
(HSE, 1989; Dolbey Jones, 1989).
These new Regulations are considerably simpler than those which
they replaced. A great deal of dead wood has been eliminated,
mainly where technology had overtaken specific requirements in
the Factories Act Electricity Regulations that reflected the
technology of the beginning of the 20th century when electrical
power distribution was in its infancy. The new Regulations are
thus less specific and deal only with general principles.
This has the advantage that they should not restrict the
development and application of new ideas in the future.
On the other hand, in the absence of specific material
requirements (such as those relating to dimensions at
switchboards in those early Regulations), the electrician at the
workplace, or the engineer for that matter, may be at a loss to
know what is and what is not acceptable practice.
Under the statutory Factories Act, Electricity Regulations (of
1908/1944) there had for many decades been an official
2-18
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
publication known as the ‘Memorandum’ (Form 928). That was
withdrawn when the Electricity at Work Regulations 1989
superseded those Regulations and a new guidance document by
the Health and Safety Executive, Memorandum of guidance on
the Electricity at Work Regulations (HSE, 1989), was issued.
This publication gives a commentary on the legal duties and
mainly rather generalized advice on the technical interpretation
of these regulations.
The Health and Safety Executive also issues a series of guidance
publications in addition to the Memorandum (HSE, 1989) on a
number of specific hazards, working situations and equipments.
11. ‘Consumer’ safety
Whereas the safety of employees from electricity used in
factories and workplaces, and the safety of the public from the
electrical distribution system in the streets etc. were matters
adequately catered for by legislation of early provenance,
consumer protection has been only relatively recently a
matter for comprehensive legislation. In Great Britain the
principal legislation is now the Low Voltage Electrical Equipment
(Safety) Regulations 1989 made under the Consumer Protection
Act 1987 to implement and align with the EEC directive known as
the Low Voltage Directive (LVD). In essence these Regulations
follow the principle that products which conform to consensus
standards agreed in International forums, e.g. CENELEC and IEC
are deemed safe and are thus allowed to be placed on the
market for sale to the public. That is a considerable simplification
of the LVD and to think of its scope simply in terms of hairdryers
and toasters would be misleading, but in terms of market share
and numbers of persons protected it is primarily a consumer-
orientated matter.
2-19
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
Within the four walls, so to speak, of the home, electrical safety
becomes almost exclusively the responsibility of the individual
householder. The product that he or she purchases may have
been made to a standard and may adequately comply with the
statutory safety Regulations and the LVD but its manner of use
and the wiring within the home are a matter for the individual.
That is the case in Great Britain at least and is repeated in similar
patterns in many countries. Prescriptive requirements about
wiring up plugs or obligatory requirements for house wiring are
rare internationally.
The well-known and highly regarded ‘Wiring Regulations’, which
have been issued by the Institution of Electrical Engineers in
many revised versions since the turn of the century, have
become the cornerstone of good electrical installation practice in
many countries as well as the UK. In the international context the
IEE Wiring Regulations have been redrafted to reflect the general
harmonization that is taking place in many technological
standard making forums. While the latest edition of the IEE
Wiring Regulations (IEE, 2008) does not pretend to equate
precisely word for word or even Regulation by Regulation with
internationally parallel documents, the format, scope and
technical principles are converging.
12. Low voltage - below 1000 volts a.c. etc.
Like the Electricity Supply Regulations and the LVD, the IEE
Wiring Regulations reflect the current international adoption of
1000 volts A.C. as a significant or at least useful ‘cut-off’ voltage.
This is almost entirely an arbitrary voltage and no safety
significance can usefully be attached to its choice. Other voltage
limits appear in Standards and even in statutory Regulations but
only at the extra low voltages, e.g. 50 volts, do these have some
useful safety context. It is interesting to note that the Electricity
2-20
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
at Work Regulations 1989, unlike the principal Regulations which
they replaced, refer to no specific voltage levels or voltage
‘bands’.
The Regulations actually define electrical danger without
reference to voltage, which is, after all, only part of the
consideration of what is dangerous in any situation. It must be
remembered that most electrocutions, i.e. fatalities due to
electric shock, occur at the predominant domestic electric
voltages, particularly 240 volts a.c.
13. Technical advice and expertise
There is no short cut to the acquisition of technical knowledge
and competence in a particular area of expertise. The published
material by itself is seldom sufficient ground upon which to
develop an adequate depth of understanding in a particular
subject. The reading of the statutory Regulations and associated
guidance may enlighten one as to the outline and maybe reveal a
few details of the hazards while the more detailed codes of
practice such as the IEE Wiring Regulations are so detailed in
themselves that at first reading they will serve to confuse as
much as to enlighten. Those Regulations themselves refer to a
multiplicity of further codes and Standards, some of which may
seem obscure to any but specialists in their particular fields.
The warning must therefore be that the prevention of accidents
and disasters rests not simply with considerations of all the
relevant laws, standards, codes and guidance but with an in-
depth understanding of the principles and practice of the
particular subjects. There is little substitute for well founded
experience and without it accidents will continue to occur.
14. Conclusion
2-21
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
The art of electrical accident prevention has been founded
primarily on the investigation of accidents by professionally
qualified engineers. The science of accident prevention is based
on a logical analysis of their reports. Some aspects involve highly
technical considerations and this is particularly true of
investigations of failures where a correct interpretation of small
details such as fracture types or surface corrosion, or possible
causes of over-voltages, is important. But it is an essentially
practical subject and its practice is conditioned both by
psychological and financial considerations. It is important to
spend money first on the action which will bring the greatest and
if possible quickest benefit.
There is also a growing recognition that safety is something that
cannot simply be bolted on to an existing organization by training
the workforce in various safety routines but that it needs
managing as part of a company’s corporate strategy. It is only
partially useful to react solely to accidents and to correct the
discrete failings identified by these events. A spate of recent
disasters, the Kings Cross Underground fire, the sinking of the
Herald of Free Enterprise, the Clapham Junction Railway crash
and the Piper Alpha oil rig fire were all fully investigated with
benefit of public inquiry and published reports. In each case
severe failings in management at levels right up to the top were
identified. Organizational problems were being exposed and
highlighted. Responsibilities were being laid at the doors of chief
executives.
To steer an organization into a safer regime takes great skill and
determination. At the very least it requires the best possible
information feedback from the workplace where the hazards
exist. This requires attention to be paid to various audit and
management information controls. One particularly useful safety
2-22
I N T R O D U C T I O N T O E L E C T R I C A L S A F E T Y
management tool is to collect and analyse data on all ‘near miss’
incidents (van der Schaaf et al., 1991). On the iceberg theory,
there are many more of these than there will be of actual
accidents and, provided that one can get those involved to be
forthcoming about these incidents, a great deal of useful
information can be gleaned about an organization’s robustness
and fitness to avoid accidents. It is likely to be much more
revealing than trying to identify the weaknesses after the
accidents themselves.
The prevention of accidents is actually much more than the
technical discipline of identifying risks and adopting the right
technical solutions to counter those hazards. It is about managing
all levels of an organization and involves applying the principles
of total quality throughout and to all activities (HSE, 1991).
Finally, there is actually very little which is completely new in the
field of electrical safety. Most of the lessons have been
discovered many years ago, the problem is that each generation
of engineers needs to learn them and older engineers may need
to refresh their memories from time to time of the hazards and
the proper ways to do this: that is, if they ever knew these things
in the first place. There is a lot of material. We hope the following
chapters will at least assist some to discover the best and safest
ways to proceed.
2-23