24/07/2015
Today’s speaker
Mike Taylor
Health, Safety and Environmental Technical Director
BEng MBA CEng CMIOSH CEnv MIET MIEMA
Mobile: 07525 278980
Email: michael.taylor@santiaconsulting.com
Electrical Safety in a Modern Working Environment
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Session Aims
A background to the legislative requirements
surrounding electrical safety.
Understand the main hazards and dangers associated
with electricity.
Identify modern strategies to control electrical hazards.
Think about where we go next.
© Santia Training Services 2015
Ref: IOSH SW July
Introduction
Each year:
30 workplace deaths
30 domestic deaths
Causes
Electric shock
Fires
Electric burns
Electrical arcing
Explosions
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
Legislative Framework
Good Practice - IET
Health and Safety at Work etc. Act 1974
Wiring Regulations
Electricity at Work Regulations 1989
Electrical system
Duty holders
Selection & suitability of equipment
Strength & capability
Competence
Provision and Use of Work Equipment
Regulations 1998
First drafted in 1882
Became BS7671 in1992
The third amendment to BS 7671: 2008 published
January 2015.
Installations designed after 30 June 2015 must
comply with BS 7671: 2008 + A3:2015.
Next update due in 2018.
Inspection and testing of fixed and
portable electrical systems
Management of Health and Safety at Work
Regulations 1999
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
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24/07/2015
Principles of Electricity
Ohms law
Voltage, Current, Resistance
Resistance
Measured in Ohms (Ω)
Electricity - The Hazards,
Dangers and Controls
Current flow will take the path of least resistance
Conductors
Copper, water, carbon, steel, etc.
Current carrying capacity
Insulators
Rubber, plastic, air, etc.
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
Electric Shock Health Effects
Damage to the nervous system / pain
Irregular heartbeat (fibrillation)
Cardiac arrest
Respiratory paralysis
Severity of Electrical Shock
Factors include:
Voltage
Current
Time exposed - milliseconds (ms)
Body and environment conductivity or resistance
Burns – surface and internal
Current path
Muscular contractions
Nature of contact
Physical trauma (shock)
Individual factors
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
Effect of Electricity
The Electrocution Principle
AC current
in milliamps (mA)
Effects
0.5 to 2
Threshold of perception
2 to 10
Painful sensation
10 to 25
Inability to let go, danger of asphyxiation
This is more than twice the amount of current required
to cause a fatal injury.
25 to 80
Loss of consciousness from cardiac or respiratory
failure
Fatality would not normally be expected below 50V ac.
Over 80
Burns at point of contact, death from fibrillation
© Santia Training Services 2015
Ref: IOSH SW July
A standard UK socket can provide up to 13A at 230V.
The average human body’s resistance is around 2000 Ohms
Using Ohms law we can see that: 230/2000 = 115mA
© Santia Training Services 2015
Ref: IOSH SW July
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Installation, Use & Inspection of
Electrical Systems
EAWR 1989
Insulation, protection and placing of conductors
Methods of Preventing Electric
Shock
MCB – Miniature Circuit Breakers
Earthing or other suitable precautions:
Designed for fusing of mains supplies.
Can be selected for different currents.
Can be selected for different loads.
Double insulation – Class II
Earthing & automatic disconnection – Class I
Fuses
Circuit breakers, MCBs
Use of safe voltages
110 V CTE
SELV
Battery powered equipment
© Santia Training Services 2015
Ref: IOSH SW July
Methods of Preventing Electric
Shock
Type B = 3 to 5 times load current.
Type C = 5 to 10 times load current.
Type K = 8 to 12 times load current.
Type D = 10 to 20 times load current.
© Santia Training Services 2015
Ref: IOSH SW July
RCD Circuit Diagram
RCD – (Residual Current Device)
Disconnects supply if an imbalance of 30mA
or more is detected.
Can be used for class 1 & 2 equipment.
An crucial requirement for equipment where
liquids are in use.
May not detect overloads or shorts.
Unless combined with an MCB
© Santia Training Services 2015
Ref: IOSH SW July
DC Power Sources – the Future?
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Ref: IOSH SW July
Causes of Electrical Fires
Inadequate circuits, e.g. 5A wire carrying 13A current
Overloaded circuits
Incorrect fuse
Damaged insulation, etc.
Loose connections
Flammable materials too close to electrical equipment
Overheating cables on coils
No let go
Excessive thermal insulation of cables
More serious burn potential
Lack of ventilation
Often involve capacitors - High potential energy storage
Unauthorised use, misuse, private equipment
DC Power Sources
Micro-generation
Batteries or rectified AC
Low voltage systems in buildings
Cars
Issues
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
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Electrical Burns
Direct burns
Electric current generates heat
Internal and external burns
Indirect burns
Arcing
The heat generated is often sufficient to
start fires or cause injury.
Arc Flash – Electrical Flashover
External burns
Short circuit melts a tool, e.g. screwdrivers
Spray of molten metal and UV light
© Santia Training Services 2015
Ref: IOSH SW July
Work on or near Live Conductors
– EAWR 14
Live working
Sufficient potential to jump across an
insulation material, usually air.
More prominent?
Risk Assessment
Calculation – IEEE1584
© Santia Training Services 2015
Ref: IOSH SW July
Live Working – Risk Assessment
Elimination of the arc flash hazard.
Unreasonable in all circumstances for it to be dead;
Reasonable in all circumstances for it to be live;
and
Suitable precautions (including where necessary
the provision of suitable protective equipment) are
taken to prevent injury.
Unsafe Working Practices
Modifications whilst the equipment is “live”
Correct isolation not carried out
Understand arc flash, signage, competence.
PPE
© Santia Training Services 2015
Ref: IOSH SW July
Procedures, authorisations, testing and maintenance.
Information and training.
Lower trip levels / settings, Design, UV Trips.
Control the risk.
De-energise, segregate, finger protection, condition.
Reduction.
Last resort, flameproof overalls, mush research.
© Santia Training Services 2015
Ref: IOSH SW July
Isolation – ‘Lock Off, Tag Out’
Working on systems made dead
Planning the job
Disconnection from power
Isolation – secure e.g. locking off
Unsuitable modifications
Misuse
Proving dead
Unsuitable equipment
Earthing as additionally precaution
Notices
Other precautions
Communication of the SSoW
Using ‘second hand’ components
Use of damaged equipment
Equipment out of test date (e.g. PAT)
Not following the fault reporting process
© Santia Training Services 2015
Ref: IOSH SW July
Physical barriers, temporary insulation
© Santia Training Services 2015
Ref: IOSH SW July
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24/07/2015
Adverse or Hazardous Environments
DSEAR 2002
Hazardous Area Classification
Probability of the hazard
Escape
Zoning – Gas / Vapour or Dust
Ignition Source
Where to Now
Electric apparatus;
Stray electric currents;
Static electricity;
Lightning
Ionizing radiation;
Radio frequency etc.
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
Electricity Supply
Edison’s original vision was a
direct current, locally based
electricity system.
Electricity Use
Point of use versus mobile.
Global information connections.
Battery operated equipment.
Demand Versus supply.
Renewables, Fossil, Nuclear.
Power electronics – Inverters etc.
Transmission and distribution.
Smart systems.
Local generation and use.
End of life.
DC Versus AC
Sustainability.
© Santia Training Services 2015
Ref: IOSH SW July
© Santia Training Services 2015
Ref: IOSH SW July
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