1. Basic Electrical Safety Faculty of Science & Health
Safe-Lab Module
Alan Hughes
January 2017
Ver.1.0

2. Why this Module! Encouraging Electrical Safety Specifically
In an Educational & Active Research Environment
Specifically
Avoid Injury, Death – You & Others
Avoid Equipment Damage & Loss of Research
Awareness of your moral & legal responsibility
to yourself, colleagues & to all others
By increasing your
awareness of potential dangers & how to avoid
creating them
awareness of your skills & Limitations
providing sources of advice & information
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3. Overview of Module! Information sources Overview of Electrical Basics
Encouraging Electrical Safety
in an Educational and Research Environment
Information sources
Overview of Electrical Basics
Electrical Equipment
Specific laboratory examples
January Ver.1.1

4. Where to get more information
Your Supervisor, Manager, Head of Department
Department Safety Statements
Department Safety Committees & Safety Officer
DCU safety - WEB
Edinburgh University H&S - WEB
University London H&S – WEB
These PP slides on Faculty Safety web site
Safety in Schools Department of education document
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5. TODAY
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6. Content [ I ] Basic Electrical Theory [ Ladybird version, no maths  ]
Voltage & Current
Electricity in the body & effects on the body
Electricity & associated hazards
[ II ] Electrical Equipment
Electrocution
General Electrical Guidelines & Precautions
Safety features: fuses, ELCBs, cables, connections, equipment design
[ III ] Specific Hazards & Personal Safety
A few Do’s , Don’ts & Watch-out-for’s
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7. -
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8. [ I ] Electricity Basic Electrical Theory
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9. Basic Electrical Theory
Electricity is the flow of electrons around a circuit
Voltage [a driving force] causes Current [e - ] to flow
AC / DC Negligible difference wrt Safety
Single Phase / Three Phase if 3 phase get a professional
SI units
Volts , Amps / milli-Amps and for power Watts, energy kWHrs
Circuit necessary for current to flow
a start point - a route - an end point
Cannot keep pouring water into a sealed bottle
October Ver. 1.4

10. Voltage, Current and Resistance
Water analogy
Water flow : electrical current flow
Water pressure : voltage
Conductor : pipe
Pump : battery
High resistance : Narrow, long pipe
Low resistance : Wide short pipe
Switch : Slam shut, on/off valve
Voltage increases => Current increases
Resistance decreases => Current increases
Voltage = Current / Resistance Ohms Law
October Ver. 1.4

11. Voltages AC = = DC Low Voltage 0 => 50V
Batteries: AA, AAA, PP3, MP3 player, Android/i-Phone
Car, trucks, busses 12 / 24 / 48
Phone or laptop charger, Christmas tree LEDs, Garden lights
High Voltage [high tension, HT ] => 300V
EU Mains, Electrophoresis, DART power lines, Capacitors SM-PSUs
Very High Voltage [ EHT ] 1KV +
ESB pylons, TV tubes, photocopiers, X-Ray machines, Mass Spectrometers
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12. The complete circuit necessary for current to flow
A complete Circuit or loop is
necessary for current to flow
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13. A complete circuit - Complete Circuit or loop.
- Complete Circuit or loop
is necessary for current to flow
- Current takes the path of least resistance
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14. Summary - basic Electrical Theory
Voltage causes
a Current to flow
Big voltage => Big current
Water analogy
A Complete Circuit
is necessary for
current to flow
Bird on H.T. wires 
Power Voltage X Current
October Ver. 1.4

15. Electricity & Human Body
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16. ‘Normal’ Electricity in the body
Muscles
Muscles control all body movements, activated using small electrical currents
Including & very importantly, those that keep us
alive: our Breathing and our Heart beat
The brain controls voluntary muscles using
small current pulses along nerves
Some local autonomous circuits for involuntary muscles e.g. Heart
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17. ‘External’ Electricity in the body
External Current through the body overrides all biological control and causes:
Loss of muscle control, respiratory, paralysis
including ‘Inability to let go’
Spasms & Involuntary movement
Fibrillation of the Heart [no heart pumping]
Burns - external & internal
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18. Just a little current can kill
It is the
Current driven through the body
by Voltage
that creates danger
Keep voltages low
Do not make your
body part of a circuit
October Ver. 1.4

19. Just a Little Current Can Kill
• 1 mA, slight tingle is felt.
• 5 mA, slight shock is felt, not painful but disturbing. The average individual can let go, involuntary reactions can lead to injuries.
• 6-25 mA, painful shock, muscular control is lost
• 9 – 30 mA, called the freezing current or “let-go” range. many humans cannot get their muscles to work, and they can’t open their hand to let go of a live conductor.
• mA, there will be extreme pain, respiratory arrest, and severe muscular contractions. Individual cannot let go, death is possible.
• mA, there is ventricular fibrillation. Muscular contraction and nerve damage occur. Death is most likely.
• 10,000+ mA, Cardiac arrest, severe burns and probable death.
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20. Electricity & Associated Hazards
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21. Electricity - associated hazards
Life support muscles
Diaphragm and breathing
Heart Fibrillation Random, uncoordinated heart contractions
De-fibrillation: High voltages (3000 V at 20 A) fraction of a second
Burns - death of tissue
Internal [organs]
External [skin] Usually at Exit & Entry areas
Indirect Injury
Falls from ladder
Thrown back. Fall to ground, onto sharp edge
Drop objects, injure an innocent bystander
Thermal burns – Very hot equipment surface, explosion
Wires & cables
Indirectly probably the most common “electrical” injury
October Ver. 1.4

22. Electricity - associated Hazards
Wires & cables
Trailing leads
Trips, falls & injury
Equipment damage
Re-route, tidy up, cover over
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23. Exit & entry Burns
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24. END [ I ] Electrical Theory Section
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25. -
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26. [ II ] Electrical Appliances. Safety - design guidelines
[ II ] Electrical Appliances Safety - design guidelines Connectors, cables Fuses, Safety devices Selection, maintenance & correct use Dealing with electrocution Environmentally friendly
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27. Electrical Appliances
Safety guiding principles
keep currents and voltages to a minimum
inside apparatus and away from our bodies
when a fault is detected Trip out
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28. Electrical Appliances
Minimise voltages [ and thus minimise current ]
Inherently safe - Low voltage / low current
Keep Voltages away from our bodies
Enclosures
Insulation
Connections safe & secure
Trip out when fault detected
Safety features – Fuses, ELCBs, Switches
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29. Electrical cables & plugs
Mains cable
Brown Live - power
Blue Neutral
Green/yellow Earth
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30. Electrical plugs, cables & fuses
Mains cable
Brown Live power
Blue Neutral
Green/yellow Earth L N
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31. Electrical fuses & ELCBs
October Ver. 1.4

32. Live, Neutral, Earth & Fuses
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33. Live, Neutral, Earth & Fuses
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34. ELCB Electric Leakage Circuit Breaker RCD Residual Current Device
RCCB Residual Current Circuit Breaker
MCB Magnetic Circuit Breakers
RCBO Residual Current Breaker
with Over-current protection
current difference of > 30 mA
for a duration of ~ 30 ms L L N N E
October Ver. 1.4

35. Fuse Vs ELCB An ELCB breaks the circuit A Fuse breaks the circuit
When too much current attempts to flow through an appliance
Usually the excess current is in Amps [Very dangerous] and it happens in less than a second
Must be replaced
An ELCB breaks the circuit
When there is a difference between the current flowing in the Live and in the Neutral wires
Usually operates when the difference is ~ 30mA [borderline safe]
Operates very fast, in a small fraction of a second
Is resettable
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36. Electrical extension boards
Emergency Stop Switch
Avoid where possible
Do not daisy-chain
Check total current
Know where they are
Check occasionally
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37. Electrical summary The Earth wire is there to protect you.
The Live and Neutral wires carry current to equipment
The Earth wire is there to protect you.
The Earth wire can act like a back-up Neutral wire,
Many appliances have metal cases e.g. kettles, toasters, dishwashers, washing machines etc.
The Fuse is very thin piece of wire.
The wire has a quite low melting point. As current flows through the wire it heats up.
If too large a current flows it melts, thus breaking the circuit
Use appropriate fuse size/rating
ELCBs, RCDs Important Safety Devices
Leakage-to-earth sensors with trip out
October Ver. 1.4

38. Electricity Safety Summary
High Voltage causes High current
Keep voltages low
Electricity require a circuit
Ensure your body does nor complete the circuit
Electric current takes the easiest path
Ensure that all equipment has an earth connection
When a fault occurs
All equipment should have fuses and ELCBs
Wires & cables
Probably the single most common electrical hazard
October Ver. 1.4

39. Guidelines to using Electrical Equipment in laboratories
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40. Equipment & Laboratory Guidelines
Use low & safe voltages: Mains voltages are dangerous 230 VAC
Select equipment appropriate for environment & use
Avoid electricity where its use could be dangerous.
Use equipment as per manufacturer’s instruction & design
Ensure adequate maintenance, damaged case, frayed leads
Insulate and enclose live parts
Ground casings to earth
Prevent conducting parts from becoming live. Earth, double insulation, separate supply from earth, limit electric power
Rubbing, Induction & Capacitance effects can build up static electricity
Avoid use of daisy-chained power extension boards
Toxic - Beryllium heat sinks, Incomplete burning can produce carbon monoxide & other toxicfumes
October Ver. 1.4

41. Electrical Hazards & Safety
Safety in Schools Department of education document
1.3 Electrical Services & equipment Pages 10 & 11
3.1 General Electrical safety precautions Pages 20 & 21
Good Housekeeping
Well organised & laid out laboratories
Adequate Class control
Water
Water & electricity do not go well together
Water makes you a better conductor allowing MORE current to flow
Mains
Avoid direct working with mains. Use low voltages
Check all leads for: Fraying, Proper clamping, Proper earthing.
Repairing
Do not repair, competency required
Trust nobody, remove fuse, use phase tester
One hand behind back, tip cautiously with back of hand
Note: Switch Mode PSU, laptop chargers, CF lamps [high voltages persists on capacitors long after switch off]
October Ver. 1.4

42. Environmental issues Don’t waste power -Turn off
15c per kWh
Use Low power versions of equipment
Flat screen Vs old CRT tube TV
Lighting: LED, fluorescent, CFL, Filament
Reduce and recycle, waste considerations!
Avoid hazardous materials
Mercury fluorescent tubes & CFLs
Cadmium & lead from re-chargeable batteries
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43. Electrical Hazards & Personal Safety
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44. Electrical Hazards & Personal Safety
Used where!
Office & home 95%
Laboratory 5%
Trailing wires, faulty wires
Mains
Avoid direct working with mains. Use low voltages
Check all leads for: Fraying, Proper clamping, Proper earthing.
Repairing
Do not repair, competency required
Trust nobody, remove fuse, use phase tester
One hand behind back, tip cautiously with back of hand
Note: Switch Mode PSU, laptop chargers, CF lamps [high voltages persists on capacitors long after switch off]
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45. Some examples of electrical hazards
Electronics experiments
Use acceptable low voltage Mains operated LT power supplies
Wrong connection – IC / electrical component over heats, shatters
Van De Graaff generator High voltage Low current !
Teltron tubes High voltage Vacuum implosion
Magnetic experiments High currents Heart pace makers
Hot plates Burns
Electrophoresis High voltages
Trailing Power and Signal wires - Protect & Tidy them up
October Ver. 1.4

46. Sometimes forgotten hazards
Medical / Sports equipment
Very strict regulations on equipment operation, design, repair
Never modify or tamper with such equipment
ECG measurements. even a few micro amps direct to the heart can have massive consequences [basis of a heart pacemaker ]
Pace makers
Susceptible to strong magnetic fields [NMR! ],
Possibly RF & Micro waves interference
Chemical Solvents
Flammable environments require specialised electrical equipment
E.g. Spark-free fridge for storage of samples dissolved in solvents
Cold rooms / water cooling
Equipment moved from cold room can get condensation on its internal electrical circuits. Avoid this movement, Use L.T. and give lots of time to acclimatise
October Ver. 1.4

47. Yet more examples RF & µW Power
Capacitive coupling, no need to touch,
Both can burn severely internally and externally depending on how focused. Think of them like an open air μ-wave oven
EHT
Static, OK [Very low current, moderate power] nearby Solvents!
Will jump considerable distances,
Beware of capacitors
Power
Heating effect in body => internal burns / damage
Contact burns, deep burns & necrosis
Trailing Power and Signal wires - Protect & Tidy them up
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48. Specific Hazards & Personal Safety
Other Laboratory Situations ?
Other Office Situations ?
Other Home Situations ?
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49. Electrocution
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50. Electrocution
Prevention & Training : Where are red mushroom switches ?
Response: Immediately cut power, red buttons / switch / plug
If in any doubt - Do not touch victim.
One hand behind back, stand on insulation, tip with back of hand
Use insulating rod / stick to move wires from victim.
Call for assistance
Talk & reassure victim
If unconscious then use first aid, CPR
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51. END [ II ] Theory Section Electrical Appliances
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52. -
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53. -
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54. SUMMARY
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55. Summary Awareness of the need for electrical safety
Potential Source of electrical dangers
Your responsibility to take care of
Yourself and Others
Note Safety References for future use
If unsure never be afraid to ask
January Ver.1.1

56. Where to get more information
Your Supervisor, Manager, Head of Department
Department Safety Statements
Department Safety Committees & Safety Officer
DCU safety - WEB
Edinburgh University H&S - WEB
University London H&S – WEB
January Ver.1.1

57. Thanks for your attention 
END
Thanks for your attention 
January Ver.1.1