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Electrical Safety

This lecture notes tackle about the electrical safety in safety manage...
Course

Safety Engineering (SAF101)

65 Documents
Students shared 65 documents in this course
Academic year: 2022/2023
Uploaded by:
Anonymous Student
This document has been uploaded by a student, just like you, who decided to remain anonymous.
Malayan Colleges Laguna

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ELECTRICAL SAFETY

Electrical shock

  • A sudden and accidental stimulation of the body’s nervous system by an electrical current
  • The current will flow through the body when it becomes part of an electrical circuit.

Current Effect 3 + mA Shock 10 + mA Muscular contractions 30 + mA Respiratory paralysis 50 + mA Heart paralysis (can be fatal) 100 + mA Ventricular fibrillation (usually fatal) 200 + mA Heart clamps tight 1500 + mA Tissue and organs burn

Electrical burns - Current passing through tissue generates extreme heat - Skin damage at entry and exit - Internal tissue damage - Result from arcs or flashes - Thermal burns from overheated wires or equipment or fires

Falls

  • Initiated by a shock
  • Muscles contract involuntarily
  • Worker can lose balance and fall

Machinery injuries

  • Unexpected activation
  • Shock
  • Pinch
  • Crush
  • Shear

Electrical hazards

  • Bare conductors
  • Insulation failure
  • Equipment failure
  • Static electricity
  • Heating and overheating
  • Electrical explosions

Bare conductors

  • Live overhead wires most common

  • Working on rooftops

  • Repair of electrical systems

  • Capacitors

Insulation failure

  • Heat and elevated temperatures
  • Moisture and humidity
  • Mechanical damage
  • Rodents, fungi
  • Chemical incompatibility

Electrical explosions

  • Occurs when two different materials contact and then separate
  • High voltage, low current
  • Flammable liquids
  • Lightning

Heating and overheating

  • Use of electricity results in heat
  • Can cause accidental fires
  • Burns out equipment
  • Equipment failure and ignition
  • Hot surfaces

Static electricity

  • Rapid overheating from over-current
  • Caused by short circuits, power surges, or lightning
  • Heated contaminants in oil-filled breakers or transformers
  • Capacitors subject to wrong polarity

Engineered protection

  • Over-current protection
  • Grounding
  • Fuses
  • Circuit breakers
  • Ground-fault circuit interrupters
  • Insulation

Over-current protection

  • Defined as any current in excess of the rated current of equipment or the ampacity of a conductor by the National Electrical Code.
  • It may result from overload, short circuit, or ground fault.

Ampacity

  • ideally would carry its rated current indefinitely, and melt quickly on a small excess
  • The element must not be damaged by minor harmless surges of current, and must not oxidize or change its behavior after possibly years of service.

Metal wire or strip

  • An important component of a fuse that melts when too much current flows which interrupts the circuit in which it is connected

Main reasons for excessive current

  1. Short circuit
  2. Overloading
  3. Mismatched loads
  4. Device failure

Elements that make up a fuse:

  1. Zinc
  2. Copper
  3. Silver
  4. Aluminum
  5. Alloys

Circuit breaker

  • an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow.
  • This can be resumed to normal operation unlike a fuse which operates once and has to be replaced.
  • It can also be made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city.

Switchgear

  • is the combination of electrical disconnect switches, fuses or circuit breakers used to control, protect and isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults downstream.
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Electrical Safety

Course: Safety Engineering (SAF101)

65 Documents
Students shared 65 documents in this course

University: Malayan Colleges Laguna

Was this document helpful?
ELECTRICAL SAFETY
Electrical shock
- A sudden and accidental stimulation of the body’s nervous system by an electrical current
- The current will flow through the body when it becomes part of an electrical circuit.
Current Effect
3 + mA Shock
10 + mA Muscular contractions
30 + mA Respiratory paralysis
50 + mA Heart paralysis (can be fatal)
100 + mA Ventricular fibrillation (usually fatal)
200 + mA Heart clamps tight
1500 + mA Tissue and organs burn
Electrical burns
- Current passing through tissue generates extreme heat
- Skin damage at entry and exit
- Internal tissue damage
- Result from arcs or flashes
- Thermal burns from overheated wires or equipment or fires
Falls
- Initiated by a shock
- Muscles contract involuntarily
- Worker can lose balance and fall
Machinery injuries
- Unexpected activation
- Shock
- Pinch
- Crush
- Shear
Electrical hazards
- Bare conductors
- Insulation failure
- Equipment failure
- Static electricity
- Heating and overheating
- Electrical explosions
Bare conductors
- Live overhead wires most common

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