In What Situations Is A Residual Current Protection Circuit Breaker Required?

Definition of RCD Residual current operated protective device (RCD): also known as leakage protector, leakage switch, leakage circuit breaker, etc., is mainly used to operate when a leakage fault occurs in the equipment to protect personal safety. Some have both overload and short-circuit protection functions, which can be used to protect the overload and short circuit of the line or motor, and can also be used as an infrequent switching start of the line under normal circumstances. Working principle: As shown in the figure below, its iron core surrounds all the current-carrying conductors of the electrical circuit. In a normal circuit without faults, I1 + I2=0, there is no magnetic flux in the magnetic core, and the electromotive force in the coil is zero.
The ground fault current Id flows through the magnetic core to the fault point, but returns to the power supply through the earth or the protection line of the TN system. At this time, the currents of the conductors passing through the magnetic core are no longer balanced, and the current difference generates a magnetic flux in the magnetic core. During normal operation, the residual current of the system is almost zero, so its action setting value can be set very small (usually mA level). When the system causes personal electric shock or the equipment casing is charged, a large residual current will appear. The leakage protector will reliably act after detecting and processing this residual current and cut off the power supply.
According to the residual current action characteristics, it is divided into: AC type; A type; B type. The AC type only protects against AC leakage and cannot act on DC pulsating leakage; the A type protects against AC and DC pulsating leakage; the B type protects against AC, DC pulsating and smooth DC leakage. 3. Where to install the residual current protector?
1. The distribution lines of the following equipment should be equipped with residual current protectors with a rated residual action current value not greater than 30mA: 1) Handheld and mobile electrical equipment; 2) Fixed equipment that the human body may not be able to get rid of in time; 3) Electrical equipment in outdoor workplaces; 4) Household appliance circuits or socket circuits.
2. Elevator shaft lighting (powered by AC 220V) The power supply voltage of the elevator shaft lighting should be 36V. When AC 220V is used, a residual current protection device should be installed and the light source should be covered.
3. Elevator pit socket The elevator pit should be equipped with a single-phase three-hole power socket with a protection level not less than IP54. The power supply of the power socket can be connected nearby (the power circuit connected nearby should be equipped with a residual current protection device.), and the bottom edge of the power socket should be 1.5m away from the pit.
4. Power distribution circuit of electric doors, automatic revolving doors, and electric telescopic doors The electric door should be powered by a dedicated circuit from the nearest distribution box (cabinet). The power supply circuit should be equipped with short-circuit, overload and residual current protection devices (a residual current protection device with an action of no more than 30mA should be installed for personal protection in case of leakage), and isolation devices and manual control switches or buttons should be installed on the electric door. The control box of the automatic revolving door and electric door should be set in a place that is convenient for operation and maintenance, and the distribution circuit should be equipped with overload protection, short-circuit protection and residual current protection devices. The power distribution line of outdoor electric retractable doors with metal components should be equipped with overload protection, short circuit protection and residual current protection devices, and equipotential connection should be made.
5. The home distribution box for connecting the power sockets of handheld and mobile household appliances should be equipped with power supply incoming line switch devices that disconnect the phase line and the neutral line at the same time. The power supply circuit should be equipped with short circuit and overload protection devices. The power socket circuit connecting handheld and mobile household appliances should be equipped with residual current protection devices.
6. Air conditioning sockets The power socket circuit of cabinet air conditioners should be equipped with residual current protection devices, and the power socket circuit of split air conditioners should be equipped with residual current protection devices.
7. The lighting circuit of the bathroom with shower or bathtub The lighting circuit of the bathroom with shower or bathtub should be equipped with residual current protection devices (the lighting circuit of the bathroom with shower or bathtub is equipped with residual current protection devices to ensure personal safety. It is safe and reliable to install residual current protection devices for the bathroom lighting circuit alone, but it is not economical and reasonable.), and the lamps and bathroom heater switches should be installed outside the bathroom door. In residential buildings, if both bathrooms are equipped with high-power electrical equipment such as water heaters, each bathroom should be equipped with no less than one power socket circuit, and the bathroom lighting should be in the same circuit as the bathroom power socket. If there are no high-power electrical equipment in the kitchen and bathroom of the residential suite, the power sockets in the kitchen and bathroom and the lighting in the bathroom can be powered by a power circuit with a residual current action protector.
8. The domestic water pump motor in the pump room The domestic water pump motor in the pump room should be equipped with a residual current action protector with a sensitivity of 300mA for ground fault protection.
9. The main circuit of the motor The main circuit of the motor can use a comprehensive motor protector. The comprehensive motor protector should have overload protection and phase failure protection; it can add additional protection functions such as three-phase imbalance, overvoltage, undervoltage, residual current, temperature test, measurement and display function, control function, and communication function.
10. Stage power and projection equipment, music stand lights in the orchestra pit and seat number lights in the auditorium (when powered by 220V) Stage power and projection equipment, music stand lights in the orchestra pit and seat number lights in the auditorium should be powered by 24V or less, and the light source can be a 24V semiconductor light-emitting lighting device (LED). When powered by 220V, a residual current action protector should be added to the power supply circuit.
11. AC charging piles AC charging piles should be equipped with residual current action protection, and a type A RCD with a rated residual action current not greater than 30mA should be selected.
12. Distribution lines of electric radiant heating, electric heating cable equipment, electric heating equipment, electric dry and wet sauna room equipment. Each heating cable of electric radiant heating and electric heating cable equipment should be individually installed with overload protection, short-circuit protection and residual current protection. Each heating cable distribution line of electric heating equipment should be separately installed with overload protection, short-circuit protection and residual current protection, and the starting current of the whole line should be verified. The electrical protection of the electric heating tape should be coordinated with the temperature protection device. The power distribution lines of dry and wet sauna room equipment should be equipped with overload protection, short circuit protection and residual current protection; the power distribution lines of lifting and parking equipment should be equipped with overload protection, short circuit protection and residual current protection;
13. The power distribution lines of window cleaning machines should be equipped with overload protection, short circuit protection and residual current protection;
14. The power distribution lines of kitchen equipment should be equipped with overload protection, short circuit protection and residual current protection;
15. Landscape lighting power supply Landscape lighting power supply uses outdoor branch lines of Class I lamps and lanterns should be equipped with residual current protection; Because the sensitivity of single-phase short-circuit protection of TT system is lower than that of TN system, fuses and circuit breakers often refuse to operate, causing the exposed conductive parts to carry dangerous voltages close to 110V for a long time. The use of residual current protection devices can greatly improve the sensitivity of electric shock protection of TT system, making TT system safer and more reliable.
16. Power distribution circuits in rooms with bathtubs or showers In rooms with bathtubs or showers, except for the following circuits, the electrical distribution circuits shall be protected by residual current devices (RCDs) with a rated residual operating current not exceeding 30mA: 1. Electrical separation protection measures are adopted, and one circuit only supplies one electrical device; 2. Circuits using SELV or PELV protection measures.
17. Socket circuits in educational buildings Socket circuits in educational buildings shall be equipped with residual current protection devices. When the residual current protection device of the power distribution circuit of the educational building is used as an additional protection for direct contact protection, the residual operating current shall not exceed 30mA.
18. The main power supply of the automatic fire alarm system shall not be equipped with residual current protection and overload protection devices. Once the residual current protection and overload protection devices are in alarm, the power supply will be automatically cut off. Therefore, the main power supply of the automatic fire alarm system shall not be protected by residual current protection and overload protection devices.
19. For circuits in the laboratory that need to maintain continuous power supply due to experimental process restrictions, when a residual current protection device for electrical fire protection or electric shock protection is installed, its protection should not directly act on the power-off function, but may act on the sound and light alarm.