Electrical safety

220V Can Kill Humans

The misunderstanding that "only high voltage is dangerous" is the most dangerous. A significant number of electrocution deaths occur from common household 220V. What's important is not the voltage, but the size of the current flowing through the body and the duration.

Human Body Effects by Current Amount

If current exceeds 10mA, you cannot release your hand by yourself. This is why an electrocuted person tightly grips the wire.

Risk Seen Through Ohm's Law

Current(I) = Voltage(V) ÷ Resistance(R)

Dry hand resistance Approximately 5,000Ω → 220V ÷ 5,000 = 44mA (Dangerous) Wet hand resistance Approximately 1,000Ω → 220V ÷ 1,000 = 220mA (Lethal)

> Sweat or moisture reduces resistance to 1/5, increasing risk 5 times. This is why electrocution accidents are more common in summer.

The Path of Current Determines Life or Death

• Hand → Opposite hand, Hand → Foot: Current passes through the heart. Most lethal.
• Hand → Same side foot: Current bypasses the heart, relatively less dangerous.

That's why during electrical work, the habit of putting one hand in your pocket (one-hand rule) exists. Using both hands creates a path that goes through the heart.

Why Grounding Is Important

If insulation on a wire inside equipment is damaged and it touches a metal casing (leakage), the moment a person touches it, the human body becomes the path for current.

A grounding wire creates a path for current to flow into the ground, which has much lower resistance than the human body. That's why equipment with a broken or disconnected grounding wire is the most dangerous.

Residual Current Device (ELB/RCD)

This is a device that works with grounding. If incoming and outgoing current differ (= current is leaking somewhere), it cuts off power within 0.03 seconds. The reason the rated sensitivity current is 30mA is directly tied to the danger criteria in the table above.

• Press the test button (TEST) monthly to confirm normal operation.
• Never fix or bypass the circuit breaker if it keeps tripping. This is a signal that there's a leakage.

5 Rules to Follow on Site

• Do not touch electrical equipment with wet hands
• Do not use octopus wiring or cables with damaged insulation
• For portable electric tools, use grounded plug (3-pin)
• Check RCD test button monthly
• If you find an electrocution victim, never touch them with bare hands, first cut off the power or remove them with a dry wooden or plastic object