Electrical leakage refers to a condition in which electricity flows outside the circuit due to aging wiring or cables. Because leakage can cause electric shock accidents and fires, early detection with an earth leakage breaker is essential. This article clearly explains how an earth leakage breaker works, what to do when it trips, and when replacement should be considered.
Why is electrical leakage dangerous? Effects on the human body
Electrical leakage is a condition in which electricity leaks outward from wiring or electrical appliances. Its effects on the human body vary depending on the current level, duration of exposure, and path of conduction.
| Current level | Effects on the human body |
|---|---|
| 0.5〜1mA | A slight tingling sensation, but little danger |
| 5mA | A fairly sharp electric shock |
| 10〜20mA | Muscle rigidity, making it impossible to move the body |
| 50mA | Risk of ventricular fibrillation and possible cardiopulmonary arrest |
| 100mA | Fatal injury, cardiopulmonary arrest |
What are the three types of breakers?
Ampere breaker
This is the most common breaker, located on the left side of the distribution board, and it cuts off the power supply when the contracted amperage is exceeded.
Earth leakage breaker
Located in the middle of the distribution board, it automatically shuts off the circuit when electrical leakage is detected. If it trips, there is a high likelihood that leakage is occurring somewhere in the house.
Safety breaker
Installed on branch circuits leading to each room, it cuts off power when the allowable current is exceeded to protect wiring and equipment.
What is the principle and mechanism of an earth leakage breaker?
Under normal conditions, the outgoing and returning current in a circuit are equal, but when leakage occurs, a difference appears. This difference is detected by a zero-phase current transformer (ZCT), and when it exceeds a certain level, an electromagnetic device operates and shuts off the circuit. By quickly interrupting leakage current of around 15〜30mA, it helps prevent electric shock accidents.
Types of residual current devices and how to choose them
- High-sensitivity type (high-speed type)：Best for preventing electric shock, operating time within 0.1 seconds
- High-sensitivity type (time-delay type)：Prevents wide-area outages, used in the main section of distribution boards
- Medium-sensitivity type：Used for main line protection in cubicles
- Low-sensitivity type：Used to protect against arc ground fault damage
Use the test button to confirm normal operation
The test button on an earth leakage breaker is used to check whether it is operating properly. For peace of mind, it is advisable to perform a test at least once a month.
Test procedure
- Confirm that the earth leakage breaker is turned ON
- Press the test button
- Confirm that the breaker switches to OFF and that power to appliances is cut
- Turn the earth leakage breaker back ON to finish
Do you need both an earth leakage breaker and a grounding wire?
A grounding wire channels electrical current from appliances into the ground to prevent electric shock. In some cases, an earth leakage breaker alone can detect leakage, but detection is faster when a grounding wire is connected. Using both together significantly improves safety.
When should an earth leakage breaker be replaced, and what does it cost?
Estimated service life
The service life of an earth leakage breaker is about 13〜15 years. If the following symptoms appear, consider replacement or maintenance.
- The unit becomes abnormally hot
- There is an unusual smell or noise
- The exterior is discolored
- The test button does not operate properly
Typical replacement costs
| Type | Typical cost range |
|---|---|
| Earth leakage breaker unit | About JPY 9,000 to 20,000 |
| Safety breaker | About JPY 4,000 to 10,000 |
| Distribution board replacement | About JPY 20,000 to 50,000 |
| Total when hiring a specialist contractor | About JPY 5,000 to 50,000 |
Replacing it yourself is prohibited by law, and a licensed electrician qualification is required. If replacement is carried out without qualifications, there may be a fine of up to JPY 30,000 or imprisonment of up to 3 months.
What to do when an earth leakage breaker trips
- Turn all breakers to “Off”
- Turn the ampere breaker and earth leakage breaker to “On”
- Turn on the safety breakers one by one to identify the leaking circuit
- Leave only the leaking circuit turned “Off” and restore electricity through the other circuits
- Ask a specialist contractor to inspect the electrical leakage
Five measures to prevent electrical leakage
- Do not touch electrical appliances with wet hands：This can cause electric shock accidents
- Do not bundle or bend cords：Arrange them in gentle loops
- Replace damaged appliances and cords early：They can cause short circuits
- Stay within power consumption limits：Be careful when using large appliances at the same time
- Review your contracted amperage：Change to a contract that matches your actual usage
Frequently Asked Questions (FAQ)
Q. How many years does an earth leakage breaker last?
About 13〜15 years is a good guideline. Use regular testing and inspection to confirm that it continues to function properly.
Q. What causes an earth leakage breaker to trip frequently?
Possible causes include faulty appliances, deteriorated wiring, and reduced insulation due to moisture. Ask a specialist contractor to investigate.
Q. Should the grounding wire always be connected?
Yes. Using it together with an earth leakage breaker allows leakage to be detected more quickly and improves safety.
