Oleh: Ir. Rizka Yunita, ST, IPP. (VA Cat II & IR Lev I | RCM Engineer)
Objective
To provide everyone with an understanding of the electrical hazards especially arc-flashed and electrocution, so as-to achieve safe production.
1. Arc-Flashed Definition
- A phenomenon of the release of heat and light energy caused by the flow of electric current through the air between two active conductors with different potentials or between an active conductor and ground.
- Short circuit in air between two active bare conductors in very close contact or contact with earth.
- There has been a failure or contact of the metal equipment.
2. How arc-flashed occurs?
- The arc of fire occurs when there is an error
- The arc of fire generates heat very high and accompanied fast explosion
- Very hot rise height approx. 19,426°C
Copper evaporation: Evaporation occurs 67000 times faster
Causes of Arc-flashed:
- Touching the conductor / active conductor accidentally.
- Failure of insulation of cables or electrical equipment (short circuit between conductors or with ground) Dirt or dust on electrical equipment
- Porosity and rust
- Extreme weather conditions for electricity supply
- Condensation or dripping water
- Inadequate grounding.
- Animals touch between conductors
- Over Voltages
- Broken parts.
- Ground fault on equipment.
- Equipment fails to energize when just repaired or inspected.
Effects of Arc-flashed:
- Air pressure wave
- Hearing damage
- Metal breaks into pieces and blows away.
The intensity of the rays that arise damage the eyes and even blind.
3. Arc-Flashed PPE
Arc-flashed PPE condition should fulfill:
- made of special cloth should be used to reduce the degree of burns from arc flames
- Proper PPE is used to prevent electric arc and shock hazard, the head, eyes, hands and feet are protected.
- PT FI has determined the type of clothing that must be used in restricted spaces.
- Electrical technicians must ensure that if they work in an electric arc area (listed on the arc label), they are at risk of being exposed to an electric arc.
- Electrical technicians must wear special fire-resistant (FR) clothing. If you don’t use it, you will be at risk of being exposed to an electric arc which can cause serious burns.
- Clothing made of ordinary materials should not be used in the area of Electric arc fire, some of these materials are made with a mixture of cotton and wool, including: Acetate, Nylon, Polyester, Rayon.
- The fire-retardant clothing is made by a recommended manufacturer.
4. Arc-flashed Energy
Arc-flashed has some criteria of exposure level:
- Exposure to 1.2 cal/cm2 resulted in 2nd degree skin burns without protective FR clothing.
- Exposure to 4 cal/cm2 resulted in burning cotton clothing.
- Exposure to 8 cal/cm2 resulted in 3rd degree skin burns without protective FR clothing.
Instantaneous Maximum Energy
- Distance / radius is longer when the voltage is greater.
- Unit of energy per unit area with a distance of 24 inches (equivalent to one arm) from the point of Arc Flash (Arc of Electric Flame).
- Incident energy unit = cal/cm2 or joule/cm2 (5 j/cm2 = 1.2 cal/cm2 ) < 600Volt.
- Incident energy causes burns to human skin.
- The incident energy threshold is 1.2 cal/cm2 for second-degree skin burns.
- 1 cal/cm2 = the amount of energy released by the cigarette lighter in 1 second.
Flash Protection Boundary (outer limit):
- The furthest limit from the energy source in the event of an electric arc. This limit is where an employee will be exposed to energy exposure of 1.2 calories/cm2 which can result in 2nd degree burns.
Limited Approach Boundary:
- A distance from exposed live parts where there is a risk of electrical shock.
Restricted Approach Boundary:
- A distance from exposed live parts where there is an increased risk of electrical shock.
Prohibited Approach Boundary:
A distance that is considered equal to-making contact with an open live part.
5. Electrocution Definition
Electrocution means being accidentally exposed to an electric current or the flow of an electric current through the human body.
6. The Severity of Electrical Shock
The severity of the electric shock depends on the following:
- Type and magnitude of electric current
- Body’s resistance to electric current
- Path of entry of electric current into the body
- The length of time exposed to / electrified
Type and magnitude of electric current
- DC tends to cause strong muscle contractions, which often push/throw the victim away from the power source.
- The AC tends to cause the muscles to lock into position, so the victim is unable to release their grip on the power source. As a result, the victim is exposed to an electric shock for a longer period of time, resulting in severe burns.
The body’s resistance to electric current
Resistance is the body’s ability to stop or slow down the flow of electric current.
The path of electric current when it enters the body
Electric current most often enters through the hands and most often exits the feet.
The length of time exposed to electric current.
The longer exposed to electric current, the more the number of damaged tissue.
Death or injury can result from the effects of electric current on the body in the following ways:
- Contraction of the chest muscles interferes with breathing and causes breathing to stop.
- Temporary paralysis of the central nervous system causes respiratory failure.
- Disruption of the normal heart rate, causing abnormalities in the work of the heart (abnormal contraction of the heart muscles).
- The movement of the heart is restrained due to muscle contraction.
- Bleeding and damage to tissues, nerves and muscles due to high heat currents.
- Secondary injuries such as falling from stairs, falling onto machines and so on.
Keep in mind that electric shocks greater than or equal to 100 milliamperes or a tenth of an ampere can be categorized as very lethal / fatal.
The size of the injury / shock when stung depends on the amount of current flowing.
The reactions and consequences of each person are not the same.
7. Electric Shock Prevention
- Apply grounding current leakage protection equipment: RCD (Residual Current Device) or GFCI (Ground Fault Circuit Interrupter) in areas that are at risk of electric shock.
- Conduct inspections of earthing protection / leakage protection equipment on a regular basis, to ensure that the equipment is functioning according to the specified standards.
- Implement procedures for using equipment
- Perform inspections on electrical equipment.