Electricity becomes unsafe when current finds path towards non-intended route. Electrical Circuits are designed for systematic current flow. If current escaped the designed path, it becomes a potential cause for unsafe working and fire. Protection system detects any unusual variation in current and disconnects power supply to the system to avoid consequential damages.
Flow Diagram of Electrical Protection, Fire and Safety. When protection works, electrical system gets isolated and the issue remains is of the reliability of equipment used which led to initiation of protection system. The problems starts when protection does not work, it led to fire, electrocution and smoke depending on the situation. Fire can be avoided if no flammable items is used nearby. Therefore,
Protection is the key to keep the dangerous aspect of electricity under control.
Electrical systems are so meticulously designed that no current shall escape without detection. However, accurate detection and response time still remains a challenge.
Electrocution and Fire are the most dangerous unintended result of protection failure
- Passage of current through body-heart is most sensitive to current damage
- Resistivity of human body depends on skin moisture, path of current flow in the human body and varies from 100-300ohms which decides the fatal voltage
Electrostatic Charge – Shock
- An isolated coach get electrostatic charged due to 25kV overhead traction if the body is not solidly earth.
- Any person touching the coach body may get a shock, may not be fatal as the body will get immediately discharged
- Capacitors in an electrical circuit may retain charge and shall be solidly earth even after the power supply is disconnected before touching it for any repair.
- When current escapes unintended path without detection, it passes through some resistive path resulting in rise of temperature of that body; and if there is any inflammable body nearby, it catches fire
- If the path is not resistive and protection still does not work to detect such a high current, heavy flashing starts which may result into fire
Do’s and Don’ts for Electrical Safety – Home and general public – 230V and HT supply
230V AC is house hold supply and can be dangerous.
- Ensure three pin plug socket, earth connection on appliance and wire continuity and its resistance. Earth pin is thick for its ability to carry high fault current and long for it to touch first before phase is connected.
- Ensure socket closure mechanism to prevent children entering their finger inside
- Earth leakage current if not flowing through earth wire will find path through damp wall and pipe line and may be fatal.
- Provide earth leakage detector(RCB) along with over current protection (MCB)
- Be watch full if duty cycle of any socket is very high. There is possibility of loose connection which may result overheating, smoke and even fire.
- Check LT over head line is protected by a guard wire
- Ensure HT supply in your area is properly fenced and impossible for children to find entry.
- Use safety and testing tools – Rubber sole shoes, Helmet, safety sling (working on HT line), Continuity tester,
- Switch off power supply, test personally and fix sticker ‘Men at Work’
- Take permit to work when working on HT line
- Never keep any inflammable item near electrical installation
- Protect HT switching station from rodent/lizards etc.
- Ensure provision of danger board
- Fence the HT area from unauthorized entry of even animals.
- Never assume and always test to be certain
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