Z1LK6123 - INTRODUCTION TO ELECTRICAL SAFETY & ELECTRICAL BASICS

Ir. Dr. Rosdiadee Nordin

¨  Maxis (2002-2006) ¤  Electrical: DC system (rectifier & battery bank) and AC system (generator, power

protection; lightning, DB) ¤  Core Switching: MSC, HLR, VLR, Switch Commander & regional E1 expansion

¨  Tutor (2006), Lecturer (2011) ¨  P.Eng. (2011) & SMIEEE (2012), MIET (2014), C.Eng. (??) ¨  BSc. – UKM (Electronics & Electrical), Malaysia, 2001 ¨  Ph.D. – Univ. of Bristol, Wireless Engineering, 2011 ¨  Research Area – Wireless Communications

¤  4G and beyond (LTE-A & ??): MIMO, OFDMA, Carrier Aggregation, Coordinated Multipoint, Energy Efficient Communications, TV White Space, Emergency Network

¤  Applied: Wireless Indoor Localization and Wireless Sensor for Sports Performance Monitoring

¨  Email: adee@eng.ukm.my , telephone: 03-892118402

2

Intro & Electrical basic

Grounding & Bonding

Cable, Battery & Personnel Safety

Load protection

Lightning Protection

Safety Regulations

Mechanical safety (Prof Chase)

Electrostatic hazard

Project Presentation, Tutorial & Summary

Planning SPKI 2015/2016

Why Electrical Safety?

¨  Electrical shock kills and injures hundreds of workers each year ¨  Happen because people don't look, don't think or just don't

understand the shocking power of electricity.

¨  Electrical shock can only occur when a part of the body completes a circuit between a conductor and another conductor or a grounding source

¨  Death or injury is not caused by the voltage; the damage is done by the amount of current that flows through the body

¨  Higher the voltage, the greater amount of current

Why Electrical Safety?

¨  Some people have survived shocks of several thousand volts, while others have been killed by voltages as low as 12 V

¨  Effects of electrical shock depend mainly on the total amount of current flow and the path of the current through the victim's body

¨  To prevent electrical shock (which can cause several types of injuries), make sure that your body cannot become part of the electrical flow and the path of the current

¨  Water reduces resistance and allows electricity to flow into wet areas, hands, arms, your body

¨  Electricity and water are a bad mix

What is electricity?

¨  What does it look like? ¨  What does it smell like?

¨  What does it taste like?

¨  Electricity is created by the movement of tiny particles called electrons

¨  It is the flow of negatively charged particles called electrons through an electrically conductive material.

¨  Electrons that are freed from an atom and travel in a specific direction produce electric current, also called electricity.

Conductors of Electricity

¨  Objects that are conductors of electricity are made of material that lets electrons move quickly: ¤ Water ¤ Trees ¤ Metals ¤ People

¨  What is an insulator? Examples? Semiconductor?

Why Are Wires Dangerous?

¨  Electrical wires, cables or lines can carry enough electricity to power the homes in an entire neighbourhood.

¨  Usually they are safe. But sometimes things can damage them. How? Example: ¤ A storm ¤ A car accident ¤ A tree limb

Shocking Statistics

¨  The fifth leading cause of accidental death in the U.S. is electrocution*

¨  Every 24 hours, someone is electrocuted in their home**

¨  Every 36 hours, someone is electrocuted in the workplace***

*National Electrical Safety Foundation (NESF) ** U.S. Consumer Product Safety Commission (CPSC) *** Occupational Safety and Health Administration (OSHA)

Electrical Accidents -Statistics

¨  25% of all fires occur due to electricity (NFPA) ¨  411 deaths from job related electrical accidents per year

(NIOSH) ¨  Electrocution - the fifth leading cause of death (1982 -

1990) NIOSH ¨  About 12 deaths due to electrocution NCRB ¨  42 % of total fires occur due to electrical sources (Source -

OISD) ¨  8% deaths that occur in Indian factories are due to

electricity ¨  Electrocution is a major cause of injury and death in both the

industrial and home environment

Electrical Accidents -Statistics

¨  Most electrocution injuries occur at voltages above 50 Volts AC or 100 Volts DC, however sometimes the voltage can be much lower.

¨  What is the cost in $$$ ??? ¤ Each year, electrical accidents result in more than $2

billion in property damage to home and industry…

But what about the cost in human terms?

Caused by 24 volt DC battery   Caused by kneeling on a  

defective 110 volt AC extension cord  

Notice where watch band & screwdriver were in contact with skin  

Notice the path in & the path out  

From: http://www.dosh.gov.my

From: http://www.dosh.gov.my

Personal protection and home

¨  40,000 residential fires annually which are caused by problems with electrical wiring systems, claiming more than 350 lives

¨  Additionally, electric cords and plugs were involved in about ¨  7,100 fires resulting in 120 deaths or about 32% of all

deaths associated with residential electrical system fires, occurring each year.

¨  Lamps and light fixtures were involved in about 8,900 fires and 60 deaths

¨  About 3,600 people are treated for injuries associated with extension cords.

¨  Switches and outlets are involved in 4,700 fires and deaths

REPORTED ELECTRICAL ACCIDENTS IN ONE YEAR ANALYSIS BY AC SYSTEMS (UK)

Standard systems of supply (a.c.) Fatal Total      

Normal, low and medium distribution voltages 23 (200 – 450 V single-phase and 3-phase) High-voltage distribution (over 3 kV, but not 13 exceeding 12 kV nominal) Main transmission systems

22 kV - 33 kV 1 66 kV - 132 kV - 275 kV -

Nonstandard alternating voltages 2

484    

68        

- 4 1 1 -

49

CONDITIONS LEADING UP TO ACCIDENTS IN ONE YEAR

Cause Fatal Total    

Failure or lack of earthing 5 91  

Testing 5 87  

Ignorance, negligence, forgetfulness and inadvertence

24 354

 

Accidents resulting from fault of persons 18 160  

Working on live gear deliberately 3 108  

ANALYSIS OF REPORTED ELECTRICAL ACCIDENTS BY LOCATION IN ONE YEAR

Premises Fatal Total    

Electricity supply 10 101 Factories 19 485 Building operations 5 86 Works of engineering construction 6 18 Onboard ship in dock 1 10 Docks and wharves etc. - 4 Warehouses - 2 Miscellaneous - 6

     

Total 41 712

ELECTRICAL ACCIDENTS ANALYSED BY APPARATUS

Fatal Total  

Portable tools Heaters and irons Lamps Testing sets, including lamps and test leads Plugs, sockets and adaptors Cables and flex for portables Electric hand welding All other portable apparatus Rotating electrical machines Transformers and reactors Oil Circuit Breakers above 650 V Oil immersed isolating switches above 650 V Other switch, fuse and control gear above 650 V Circuit breakers, not exceeding 650 V Contactors below 650 V Switches not exceeding 650 V

- 19 - 7 2 13 2 22 - 59 2 33 - 15 - 24 - 13 1 7 - 6 - 9 - 9 - 17 - 93 1 76

Electricity and People

¨  A person usually offers a lesser resistance for the electricity

¨  Human body is about 60% water in adult males and 55% in adult females (lean muscle, blood, body fat and bone)

¨  The person forms a completed circuit when touching the ground

¨  Electricity always tries to travel to ground

Sources of Electrical Hazards

¨  Short circuits are one of many potential electrical hazards that can cause electrical shock.

¨  Electrostatic hazards due to single or multiple discharges of static electricity may cause minor shocks.

¨  Arcs and sparks hazards. When the electric arc is a discharge of static electricity it is called a spark.

¨  lightning hazards. Lightning is static charges from clouds following the path of least resistance to the earth, involving very high voltage and current.

¨  Improper wiring ¨  Fire hazards are conditions that favour fire development of

growth.

Biological Effects of Electrical Hazards

¨  The effects can vary depending on ¤ Source characteristics (current,

frequency, and voltage). ¤ Body impedance and the current’s

pathway through the body. ¤ How environmental conditions affect

the body’s contact resistance. ¤ Duration of the contact.

Electrical Systems

Electrical Systems

Electrical Injuries

¨  There are four main types of electrical injuries: ¤ Electrocution (death due to electrical shock) ¤ Electrical shock ¤ Burns ¤ Falls

Electric Shock

¨  The electric shock is caused by a current passing through the body. The lethality of an electric shock is dependent on: ¤  Current (the higher the current,

the more likely it is lethal); ¤  Duration (the longer the

duration, the more likely it is lethal);

¤  Voltage (the higher the voltage, the more likely it is lethal);

¤  Pathway (if current flows through the heart muscle, it is more likely to be lethal

Diagram showing how electric shock occurs: The severity of electric shock depends on the current flowing through the body (I) in Ampere, which is a function of the electromotive force (E) in volts, and the contact resistance (R) in ohms.

Electric Shock

Electric Shock

¨  Dry skin (resistance around 10,000Ω)

Current = 220V ÷ 10,000Ω = 0.022A

¨  Wet skin (resistance around 500Ω)

Current = 220V ÷ 500 Ω = 0.44A

Electrical Burns

¨  Most common shock-related, non-fatal (?) injury

¨  Occurs when you touch electrical wiring or equipment that is improperly used or maintained

¨  Typically occurs on the hands

¨  Very serious injury that needs immediate attention

Falls

¨  Electric shock can also cause indirect or secondary injuries

¨  Workers in elevated locations who experience a shock can fall, resulting in serious injury or death

Grounding and Double Insulation ¨  Hand-held electric tools pose a

potential danger because they make continuous good contact with the hand

¨  To protect you from shock, burns, and electrocution, tools must: ¤ Have a three-wire cord with ground and

be plugged into a grounded receptacle, or

¤  Be double insulated ¨  Path: The path to ground from circuits,

equipment, and enclosures must be permanent and continuous

Inadequate Wiring Hazards

¨  A hazard exists when a conductor is too small to safely carry the current

¨  Example: using a portable tool with an extension cord that has a wire too small for the tool ¤  The tool will draw more current than the cord can handle,

causing overheating and a possible fire without tripping the circuit breaker

¤  The circuit breaker could be the right size for the circuit but not for the smaller-wire extension cord

Control Inadequate Wiring Hazards ¨  The wire must be able to handle the current. Its insulation must

be appropriate for the voltage and tough enough for the environment

Overload Hazards

¨  If too many devices are plugged into a circuit, the current will heat the wires to a very high temperature, which may cause a fire

¨  If the wire insulation melts, arcing may occur and cause a fire in the area where the overload exists, even inside a wall

Electrical Protective Devices

¨  Fuses and circuit breakers are overcurrent devices ¤  When there is too much current:

n  Fuses melt n  Circuit breakers trip open

¨  Clues that electrical hazards exist ¤  Tripped circuit breakers or blown fuses ¤  Warm tools, wires, cords, connections, or junction boxes

¤  Ground Fault Current Interrupter (GFCI) that shuts off a circuit ¤  Worn or frayed insulation around wire or connection

Use of Flexible Cords

¨  More vulnerable than fixed wiring ¨  Do not use if one of the recognized wiring methods can

be used instead ¨  Flexible cords can be damaged by:

¤ Aging ¤ Door or window edges ¤  Staples or fastenings ¤ Abrasion from adjacent materials ¤ Activities in the area

¨  Improper use of flexible cords can cause shocks, burns or fire

Energized Work

¨  EXEMPTION 1 De-energizing introduces additional or increased hazards. Examples include interruption of life support equipment, deactivation of emergency alarm systems, shutdown of hazardous location ventilation equipment, or removal of illumination for an area.

¨  EXEMPTION 2 De-energizing is infeasible due to equipment design or operational limitations. Examples include testing of electrical circuits that can only be performed with the circuit energized, and work on circuits that form an integral part of a continuous industrial process in a chemical plant that would otherwise need to be completely shutdown in order to permit work on one circuit or piece of equipment.

¨  EXEMPTION 3 Live parts that operate at less than 50V to ground need not be de-energized if there will be no increased exposure to electrical burns or to explosion due to electric arcs.

Electric Arc

Electric Arc

Category Cal/cm2 Clothing

0 1.2 Untreated Cotton

1 5 Flame retardant (FR) shirt and FR

pants

2 8 Cotton underwear FR shirt and FR

pants

3 25 Cotton underwear FR shirt, FR pants

and FR coveralls

4 40 Cotton underwear FR shirt, FR pants and double layer switching coat and

pants

Double layered switching hood or Balaclava for 2*

Hazard Risk Category 4

Hazard Risk Category 3

Hazard Risk Category 2 Hazard Risk Category 1

Competent Persons

¨  Electrical Engineers ¨  Electrical Service Engineers ¨  Electrical Supervisors ¨  Chargeman

¤  Chargeman AO (Low Voltage System without Power Station and Aerial Line) ¤  Chargeman A1 (Low Voltage System without Power Station) ¤  Chargeman A4-2 (Low Voltage System without Aerial Line and Synchronising Generator) ¤  Chargeman A4-1 (Low Voltage System without Synchronising Generator) ¤  Chargeman A4 (Low Voltage System) ¤  Chargeman BO-2 (High Voltage System without High Voltage Power Station, High Voltage

Aerial Line, Low Voltage Synchronising Generator and Low Voltage Aerial Line) ¤  Chargeman BO-1 (High Voltage System without High Voltage Power Station, High Voltage

Aerial Line and Low Voltage Synchronising Generator) ¤  Chargeman BO (High Voltage System without High Voltage Power Station and High

Voltage Overhead Line) ¤  Chargeman B1 (High Voltage System without High Voltage Power Station) ¤  Chargeman B4 (11kV or 33kV)

Competent Persons

¨  Wireman ¤  PW1 Single Phase Wireman ¤  PW2 Single Phase Wireman + Testing Endorsement ¤  PW3 Three Phase Wireman ¤  PW4 Three Phase Wireman + Testing Endorsement ¤  PW5 Three Phase Wireman + Electric Sign Endorsement (Neon Light) ¤  PW6 Three Phase Wireman + Testing Endorsement + Electric Sign Endorsement

(Neon Light) ¨  Cable Jointers

¤  PK1 Low Voltage ¤  PK2 Until 11kV ¤  PK3 Until 33kV ¤  PK4 Until 66kV ¤  PK5 Until 132kV ¤  PK6 No Restriction

Lockout/Tagout (when servicing equipment)

¨  Shut down the machine or equipment

¨  Completely isolate the machine using the appropriate energy-isolating devices

¨  Make sure a lockout or tagout device is applied for each energy-isolating device and only by the authorized employee doing the service or maintenance

¨  Make sure all potentially hazardous stored or residual energy is relieved, disconnected or restrained

¨  Notify affected employees

WHAT TO DO IN ELECTRIC SHOCK SITUATION ¨  First, stop the current flow from the circuit through the victim's body, if

it hasn't already been done. ¨  Often, victims are unable to pull away from the source of current. ¨  If the victim is still in contact with the current, disconnect or de-

energize the circuit, if possible. ¨  If this cannot be accomplished, obtain a nonconductive item, such as

dry clothing, dry rope or a dry stick, and remove the victim from the source of the current.

¨  Then call or send for help. ¨  Next, check to see if the victim's heart or breathing has stopped. ¨  Give the required first aid until professional help arrives.

Recognizing Hazards

¨  Exposed electrical parts ¨  Wires with bad insulation

¨  Electrical systems and tools that are not grounded or double –insulated

¨  Damaged power tools and equipment

¨  Inadequate wiring ¨  Overload circuits

Summary

¨  Exposed electrical parts ¨  Wires with bad insulation ¨  Ungrounded electrical systems

and tools ¨  Damaged power tools and

equipment ¨  Inadequate wiring ¨  Overloaded circuits ¨  All hazards are made worse

in wet conditions

¨  Guarding live parts

¨  Proper grounding

¨  Using GFCI’s

¨  Using fuses and circuit breakers

¨  Proper use of flexible cords

¨  Proper use of PPE

¨  Training

Hazards Protective Measures

10 COMMON MISTAKES

1.  Thinking that it's "only 120 volts" or 208 volts or 480 volts or... 2.  Working on energized systems or equipment when it can be de-

energized 3.  Not wearing PPE 4.  Outdated or defective test equipment to troubleshoot 5.  Not wearing the right PPE 6.  Trusting someone else for your safety 7.  Not performing required maintenance of power system equipment. 8.  Not carrying your gloves with you 9.  Not using a proper documentation system 10.  Going to sleep during safety training or SPKI lecture!