intelligent scada systems - iceweb safety/elect safety for... · as3000 defines extra low voltage,...

Session Two: Electrical Safety for Engineers and Supervisors – A First Primer

2013 Electrical Safety & Power System Protection Forum

Session Two:

Electrical Safety for Engineers and Supervisors – A First Primer

Gary Triffitt

Consultant, B. Econ. Dip. Elec. Eng. MIEAust. EC 1348 EW 107178

1. Introduction – an historical perspective from my own experience over 50 years

When I became an electrical engineer 50 years ago there was not one word on safety

in either my training or my workplace. As a rookie engineer I was sent off alone to

carry out work which was on occasions downright dangerous, frequently with minimal

instruction and equipment. In the words of my mother “the devil takes care of his own”

and I am pleased to note that I am still here!

Admittedly that was 50 years ago and in the Northern Territory. Not only was that in

frontier locations (Darwin and Gove) but my 50 years span almost a third of the

history of commercially distributed electric power. In those early days attitudes to

safety were often, at best, cavalier.

In later years I found myself directly supervising linesmen and electricians in a

construction environment which was very ‘hands-on’. It was through this that I

became a licensed electrician in order to have some credibility.

For the last 5 1/2 years I have been teaching electrical apprentices the content of the

Certificate III in Electrotechnology. This course contains significant content on safety,

safe working practices and hazard recognition and management. Electricians are

licensed to deal with a maximum of 1000 volts rms or 1500 volts ripple free DC. This

is called somewhat deceptively “Low Voltage”. Beyond these voltages, called ‘High

Voltage’, additional training and certification is required. Extra Low Voltage (below 50

volts AC and 120 volts DC) does not require licensing

In modern times there is much more focus on safety but workers and the public are

still being killed and injured by electricity and other hazards.

The purpose of this paper is to ensure that you, the audience, are made aware of the

dangers and of modern practice in hazard management with particular reference to

electricity.

You cannot depend on the devil!!

2. Brief Historical Perspective and Preamble

Electricity is a silent, insidious killer. It makes no sound, and has neither smell nor taste. Electricity was first distributed commercially 160 years ago in the USA and other

countries, including Australia, and one in two linesmen could expect to die as a result

of electrical accidents.

There was a very public and acrimonious argument between Edison, promoting DC,

and Tesla, promoting AC, as to the vehicle to distribute electrical power in the ‘War of



the Currents’. Edison resorted to publicly electrocuting stray animals from the city

pound to demonstrate that high voltage AC was potentially lethal. In a celebrated

demonstration he electrocuted a rogue elephant that had previously killed two of its

handlers. There was a public backlash to the event, but more importantly Tesla joined

with Westinghouse to provide a new power station at Niagara Falls to transmit power

to New York in 1895. This together with the electrification of the Chicago Trade Fair,

again by Tesla, sealed the fates of DC and AC, at least at that time. Prior to this time

there was a proliferation of isolated DC and AC systems. The rapid industrialization of

the 20th Century and the pressures of the First World War led to an enormous

expansion of use of electricity.

In recent years HVDC has re-entered the scene.

The key to the distribution of electricity on a large scale over long distances is to

elevate the voltage so that the current can be reduced and hence the power wastage

(copper losses), proportional to the square of the current, is also reduced. The

highest AC voltage in use in WA is 330 000 volts and in Australia 550 000 volts. Only

AC can have its voltage changed by transformers. There are two High Voltage DC

links in Australia – both at 400 000 Volts. One links Tasmania to Victoria (Basslink)

and one links Queensland to NSW. A third is at the same voltage in New Zealand

linking the North and South Islands.

In the eastern states of Australia the power systems from north of Cairns (Port

Douglas) to west of Adelaide (Port Lincoln), form one large power grid. The addition

of more and more power stations necessarily increases the available fault levels.

The generating and transmission authorities have retained their identities, and trade

electricity through National Electricity Market (NEM). The Snowy Mountains Authority

has been dissolved and its assets distributed between Victoria and New South Wales.

The NEM operates one of the world’s longest interconnected power systems between

Port Douglas, Queensland and Port Lincoln, South Australia with an end-to-end

distance of more than 4000 kilometres. Tasmania is also connected by Basslink to

Victoria. Over A$11 billion of electricity is traded annually in the NEM to meet the

demand of almost eight million end-use consumers.[1]

In rural Australia there is extensive use of Single Wire Earth Return (SWER)

transmission providing supply to isolated small loads. These operate typically at 19.1

kV, and as the name suggests, supply power using only one conductor, while the

circuit current returns through the ground. Voltage gradients around the customers’

earth mats provide potentially dangerous step and touch voltages, particularly during

faults.

In recent years there has been widespread application of solar power in the suburbs,

and this has introduced the complication of dual power supply on houses, with

attendant safety issues.

The highest voltage in use in the world is 1,100,000 Volts AC (China) (ref 1) and

800,000 Volts DC (China). A line connecting Russia and Kazakhstan from 1989 to

1996 was commercially operated at 1200 kV AC. The line was taken out of operation

due to the collapse of the Soviet Union.

http://en.wikipedia.org/wiki/Electrical_grid

http://en.wikipedia.org/wiki/Port_Douglas,_Queensland

http://en.wikipedia.org/wiki/Port_Lincoln,_South_Australia

http://en.wikipedia.org/wiki/Electricity

http://en.wikipedia.org/wiki/National_Electricity_Market#cite_note-1



In India, Powergrid, a central sector PSU, has decided to set up a 400/1,200 KV

substation at Deoli. The highest voltage proposed in power transmission is 1,200 KV.

Throughout Australia there is extensive use of transmission voltages on secondary

feeders of 66 000, 132 000, 220 000 and 275 000 volts.

Voltages at these levels have their own safety issues such as safe earth clearance

distances, flashover and corona, together with voltage rises of system earthing due

to faults.

3. Summary of Legislative Requirements

Safety in the workplace in WA is governed by the WA Occupational Health and Safety

Act, together with the Mining Act and to these are added WA OSH Regulations and

the Mining Act Regulations.

WA OSH is managed by Worksafe. This covers all aspects of work activity in the

workplace.

Energy Safety manages all aspects of Gas and Electricity safety in the workplace and the community. As such it inspects completed work as required, investigates electrical and gas installation accidents, undertakes litigation in the event of substandard work and work undertaken by unlicensed individuals and companies. In summary:

Employers are required to provide a safe working environment Employers are required to provide all necessary training for their workers Workers are responsible for their own safety Workers are required to work in a manner which does not endanger their fellow workers Employers are required to provide all necessary Personal Protective clothing and equipment

As engineers and supervisors we are accountable for the safety of staff and workers that we direct. The word “personnel” is de-humanizing and may let us forget that we are dealing with people. In the event of an accident, whether fatal or not, we may find ourselves the subject of litigation by both statutory bodies and the victim or the victim’s estate. Fatal accidents find their way to the Coroner’s Court, and this may further focus on our failure to safely supervise our workers. Electrical work is further governed by a host of Acts and Standards including:

AS3000 Wiring Rules AS2067 Design and erection of high voltage installations

WA Electricity Act BCA – Building Codes of Australia Sundry standards for Caravans, mobile homes and marinas Western Power Electrical Regulations Hazardous Areas High Voltage safety and practice Solar panel PV installations Wind generation installations



AS3000 defines extra low voltage, low voltage and high voltage:

Extra low voltage is voltages below 50 Volts rms AC or 120 Volts DC

ripple free

Low voltage is defined as voltages above ELV and below 1000 Volts rms

AC or 1500 Volts ripple free DC

High voltage is defined as voltages above low voltage

Note that this does not imply that DC is safer than AC. In any case AC voltages are rms which means that peak voltages are 1.4 times the rms voltages. Indisputably DC will kill you just as dead as AC. AS3000 defines ‘Direct contact” as contact with normally energized conductors, ‘Indirect contact’ as contact with surfaces not normally energized, but become energized during faults, causing touch and step voltage hazards. AS2067 deals with the design of High Voltage installations. It is concerned with the appropriate design to contain touch and step voltages within limits that a “normal” person will survive in the event of a fault affecting station equipment.

4. The physiological effects of electric current and Arc Flash

I shall make only cursory mention of Arc Flash as others are speaking on that in this seminar. However, with the increasing levels of energy in power systems due to requirements for larger transformers and generators, the systems themselves are able to deliver greater energy in fault situations. Serious electric incidents are likely to have associated large arc flash events and the latter result in serious burns to exposed skin and flesh due to the presence of hot gas plasma and molten metal as sparks. The degree of injury is minimized by the use of appropriate classes of clothing and PPE. Electric shocks are of course dangerous in their own right. The level of experienced voltage, the path of the electric current through the body, the level of resultant current through the body, the duration of current flow and in the case of the heart the point in the heart beat cycle at which the shock is received all play their part. This may lead to ventricular fibrillation which requires the application of a defibrillator to restart the heartbeat. Loss of heartbeat for longer than about 2 minutes may lead to brain and organ damage or death. CPR statistics show that with only CPR chances of recovery are 5 to 10%, while this soars to 40% if a defibrillator is applied within 5 minutes.



(Courtesy ‘Electrotechnology Practice- Second Edition Jeffery Hampson published by Pearson)

A current of 1 milliamp is barely discernible, from 1 to 15 mA causes various degrees of pain, while a current of 15 to 17 mA leads to ‘grip’ which can’t let go. Beyond this current, potentially fatal results occur with loss of respiration at 75 mA and fibrillation at 100 mA. In addition Australian utilities follow British practice and use 50 Hertz as a frequency. This has close resonance with the frequency of synaptic impulses between nerves in the human body, thereby making the body more vulnerable. The choice between 50 Hz and 60 Hz is steeped in urban myth. Early systems operated at 25 Hz and 40 Hz primarily to meet the needs of traction engines and industrial applications. 40 Hz was widely used in Australia in mining sites. However the lower frequencies caused light flicker with incandescent lamps and arc lamps (used in cinemas). Low Voltage Electric shocks are characterized by entry and exit burns. High voltage shocks are characterized by extensive damage to internal body tissue. Extra low voltage is not often a source of electrical shock but under the right conditions such as wet floors can be just as hazardous as Low Voltage High voltage accidents are less common as the management of access to HV equipment is through switching instructions and access permits. HV incidents are usually the by-product of some other event such as traffic accidents or major equipment failure. Hazard Management and Practical Job Safety Analysis The first requirement is to recognize the hazard!



In the textbook approach we look to attempt to apply one or more of the following steps:

Eliminate the hazard

Substitution

Re-engineer the hazard

Apply management systems

Use PPE

Eliminate the hazard – if electricity is switched off it is no longer a hazard. Substitution – change the work process or the equipment to a less hazardous process. Re-engineer the hazard - provide RCD’s or other safety devices. Apply management systems – access permits and switching instructions. Use PPE - safety boots, gloves, glasses, face shields, Faraday suits and clothing of appropriate energy rating. These steps cover all hazards, not just electrical, and are all aimed at reducing the risk provided by the hazard. For electrical hazards we apply the additional steps of containment (in design) and isolation as a means of eliminating the hazard. Electrical Apprentices are not permitted to work on ‘live’ equipment. At CET we require apprentices to carry out Job Safety Analysis. Before commencing work they complete a JSA form (figure i) Hazard Risk Assessment and Job Safety Analysis involves a subjective estimate of the likelihood of an event and a measure of its consequences: e.g. direct contact with live low voltage conductors which have not been isolated is ‘5’ and the consequences are estimated at 5 which gives a risk factor of 25 (the number in the box not the product 5x5). After isolation lockout and tagging this becomes ‘1’ In their ‘on-the-job’ training, tool-box meetings are used to plan jobs and discuss the hazards and safety measures to be undertaken. Necessarily there is intense focus on electricians and apprentices as these are at the ‘coal-face’ of the electrical industry. Most engineering offices these days would have a ‘tool-box’ meeting to discuss the same areas, even though they are remote from the ‘hands-on’ situation as this forms part of the planning of the job.



Hazard ID and Risk Assessment Checklist

Date: ____12/05/13______________ Name: Bill Smith

Task: ___Change RCD on main

switchboard_________________________________________

Location: _____7 Smith Street Dianella______________________________________

Hazard / Risk I Controls R

Electricity / Isolation 25 Isolate/lockout/tag/prove dead 1

Vehicles / traffic management

Working at heights

Slips, trips, falls 17 Housekeeping 5

Pinch Points

Public or pedestrians 17 Barriers, Safety officer 5

Protruding – flying objects

Tools or other equipment 12 Secure from Falling 5

Substances / Chemicals

Manual handling

Environmental

Noise

Fumes / dust

Access / egress

Flammable/ fire

Pressure / burst / explode

Lighting / visibility

Confined space

I = Inherent Risk R = Residual Risk

* This form is used for training purposes only and is not subject to amendment.


Electrical Safety & Power System Protection Forum

* This form is used for training purposes only and is not subject to amendment. Figure I courtesy College of Electrical Training

The Risk Matrix is used to (subjectively) determine the inherent (I) and residual

(R) level of risk of a particular hazard. The mantra of “Isolate, Lockout, Tag, Prove dead” is repeatedly reinforced. The “Prove Dead” step also involves the routine of “Check the checker, check the job, check the checker again” as faulty test instruments can conceal the presence of dangerous voltages.

5. Annual electrical accident statistics for WA and Australia over the last 10

years

In a typical year since 2003 in Australia about 9 to 17 people are killed by electrocution. Prior to 2003 about 30-35 people per year were killed. 2 or 3 of these are ‘hard luck’ stories – wrong place at the wrong time. The rest are the results of carelessness, stupidity or negligence. A partial catalogue of some accidents and incidents over 30 years could include

Housewife on the phone in Victoria killed by transferred touch voltage due

to fault in the nearby substation

Workers installing thermal insulation variously shocked or killed by faulty

wiring

Kitchen hand electrocuted trying to fix a commercial dishwasher at

Malaga Markets

Electrical engineer killed in a substation accident at Boulder

“electrical apprentice” killed at Bunbury

Hercules the police horse killed at the Kalamunda Show and people

present received shocks while retrieving harness and saddle. This was

due to incorrect earthing of floodlights on the football ground

Child electrocuted at Roebourne due to lack of RCD’s and faulty

installation

Manager electrocuted at Dampier as a result of transporting an aluminum

boat on a trailer with the mast up encountering the street based 11kV

At Dampier a truck driver pulled down the 33kV line to Karratha while

spreading gravel with the tray elevated. The danger was further

enhanced by the use of automatic re-closers on the line

Man killed in Queensland when she encountered step voltage from a

faulty garden lights installation. Brass strip in the paving construction joint

was not earthed, and the garden lights developed a fault

RISK MATRIX

Likelihood

Conseq

uence

5 4 3 2 1

5 25 24 23 19 15

4 22 21 18 14 13

3 20 17 12 11 6

2 16 10 9 5 4

1 8 7 3 2 1



Two men killed while stealing copper from a 22kV substation at

Greenbushes when the incoming line and droppers were still energized.

Electrician severely burned (arc flash) by applying a multimeter set on the

wrong scale and the multimeter had an inadequate fault containment

level.

Electrician severely shocked when faulty test meter leads concealed the

presence of dangerous voltages

Electrician severely shocked during a power station construction project

in Arnhem Land when a diesel was started without noticing that the

sparky was making off the 22kV generator cables in the HV switchboard.

Fortunately the exciter supply fuses were not in place so only the voltage

due to residual magnetism was available.

Linesmen working on a de-energized HV line parallel to another line in

service for a considerable distance received a severe shock due to

induced voltage

Contact with overhead lines by vehicles and equipment (cranes) accounts

for about 4 fatalities per year

And then of course there are the indirect causes of death and loss of property due to fallen power lines causing fires etc., so-called ‘collateral damage’. In WA RCD’s (also known as ‘Safety Switches’) in houses, units and flats are now required by law. These are fitted to plug-in circuits and lighting circuits and detect an out of balance current flowing to earth. As such they protect people rather than wiring and electrical equipment. The WA ‘Electrical Incident Report of 2010-2011’ defines the following electrical events: Electrical Fatality – in which death by electrocution occurred Serious Electrical Accident - non-fatal electrocution requiring medical treatment Electric Shock - non-fatal electrocution not requiring medical treatment Electrical Incident – in which electrocution, fatal or non-fatal, occurred FIFR (Fatal Injury Frequency Rate) is the number of fatalities per million population.



6. Analysis of those statistics by age, accident category and review of their

causes –

particular case studies

There are many factors that can contribute to electrical shock and electrocution

incidents, however an analysis of events reported in South Australia in the period

from 1994 to 2003 indicates that about 50 per cent of shocks were due to

problems on the distribution network and 50 per cent were due to problems in

consumers’ installations. The major causes of electrical shock and electrocution

incidents in studies in South Australia were found to be:

41% exposed metal raised to shock voltages because of electrical faults

18% contact with live parts

10% exposed metal raised to shock voltages because of inadequate circuit design

9% defective insulation

3% electrostatic phenomena

2% loss of earthing

1% lack of earthing

16% other

These statistics are quoted in Electrical safety - One flash and you're ash

Friday, 19 August 2011 Written by Chris Towsey Editorial Safety & Health, QCoal

Pty Ltd http://www.qrc.org.au/

There is a stark change since 2003, with a dramatic reduction of annual deaths due

to electrocution from 30-35 to 9 to 17, possibly due to education of both public and

workplace, introduction of RCD’s and a much greater focus on safety.

http://www.qrc.org.au/



These statistics are quoted in Electrical safety - One flash and you're

ash Friday, 19 August 2011 Written by Chris Towsey Editorial Safety &

Health, QCoal Pty Ltd http://www.qrc.org.au/

Several studies in various countries produce a profile of who is likely to be electrocuted,

and when and where it will happen:

A male

Aged 20 to 35

At work

In summer months

With his upper body extremities coming in contact with a live wire

The current source is more likely to be low voltage (<1000v) than high voltage

Water is likely to be present




Perth Metro Regional WA

EnergySafety conducted a safety awareness campaign during 2003-04, 2005-06,

2007-08 and 2009-10 fiscal years. Chart 1 demonstrates that there have been fewer

fatalities in those years.

At least two RCD’s to existing properties constructed post 1992 came into force with

the release of AS3000-2007 in August 2009 throughout Australia, and was a

requirement for domestic properties for sale or rental in WA in 2009-10.

Chart 3 shows an improvement in fatalities per million July 2001 to June 2011.



Chart 4 shows that the rate per million in the Perth metropolitan region has remained

stable over this period, while the regional areas have shown a substantial reduction.

Table 4 shows workplace fatalities but excludes non work place fatalities across

Australia.



7. Analysis of fatalities by workplace, by age, by rural/metro for WA

Non-workplace trends have increased. However the introduction of RCD’s in domestic

installations will bring about a reduction in future years.

EnergySafe has also advertised heavily to discourage DIY electrical work by

unqualified persons.



4.5 Age of the deceased



Chart 21 shows a consistent decrease in the total number of electrical accidents

1995/96 to 2010/11 in WA. Over the reporting period 53% of workplace accidents

occurred outdoors while 47% were indoors.

A significant proportion of domestic accidents occurred in wet areas (12%) such as

bathrooms, kitchens and laundries.

8. The personal consequences of accidents – death, severe injury, psychological

impact on future work, impact on families

The most severe event is of course death. Regardless of your religious views on life after death, the fact remains that the victim had family and friends who are very directly affected by the death of the victim. Loss of breadwinner, father, mother, siblings, lovers and so on, strikes at the very heart of personal relationships and family survival.



Victims who survive may also have severe psychological issues in returning to work particularly at the site of their accident, not to mention physical injuries which may take them out of the workforce..

9. Overview of electrical safety training provided by Universities, TAFEs and

Electrical Apprentice training institutions in WA

Universities

The universities offer degree level courses in engineering disciplines.

The universities have extensive and elaborate information on their websites, but it is

unclear to what extent the topic is taught in the courses at a ‘hands-on’ level. ‘Safety’ is

embedded in erudite courses about ‘Risk, Reliability and Safety’ which covers machine

design and mathematical probability, but are students provided with the skill base to

keep them alive in the face of danger?

Tafe’s

The Technical and Further Education colleges offer a wide array of courses, and these

include advanced Diplomas in Engineering. These bodies are bound by the course

framework set down by EE-OZ and this includes extensive safety training.



Electrical Apprentice training institutions

These bodies are also bound by the course framework set down by EE-OZ.

The Electrotechnology III course for apprentices includes extensive components on

safety and documenting hazard management.

In addition, CET and EGT (a group training employer of electrical apprentices) provide

additional refreshers on electrical safety for EGT apprentices.

CET also provides ‘Fee for Service’ courses, ranging from Electrical Contractors

courses to High Voltage Switching to Portable Appliance Testing, and in all of these

courses emphasis is placed on electrical safety.

CET provides further courses - Certificate IV courses in Instrumentation and

Hazardous Areas, which are similarly covered by in EE-OZ.

10. Summary, close and questions

In 160 years we have progressed from killing half the workers servicing electrical systems to the point at which the workplace is regulated and protected by law and practice. Extensive training and emphasis on safety, together with greater recognition by employers, has served to make the workplace a safer place. Homes are also safer as a result of improved standards and regulation, and extensive advertising campaigns. However, the greatest hazard is, as always, people. A quotable quote I recently saw stated that no amount of legislation and/or protection will protect a sufficiently determined fool. All protection is readily undone by individuals with a disregard for the dangers presented by the unseen killer. References

1. May 1, 2009 Switchgear Technology Surpasses 1 Million Volts Sonal Patel Power Magazine

2. An Introduction to Australia's National Electricity Market http://www.aemo.com.au/corporate/0000-0262.pdf

3. Electrical safety - One flash and you're ash Friday, 19 August 2011 Written by Chris Towsey Editorial

Safety & Health, QCoal Pty Ltd http://www.qrc.org.au/

4. Electrical Incident Safety Report 2010-2011 Government of Western Australia Department of Commerce

EnergySafe

5. History of electric power transmission –Wikipedia

6. Notified Fatalities Statistical Report 2009-10 March 2011

7. ‘Electrotechnology Practice- Second Edition Jeffery Hampson published by Pearson

8. College of Electrical Training Balcatta

9. Modern Marvels High Voltage (Video on Youtube)

10. AS3000 Wiring Rules

http://www.aemo.com.au/corporate/0000-0262.pdf


intelligent scada systems - iceweb safety/elect safety for... · as3000 defines extra low voltage,...

Documents