What is the RCD?

By Admin | Electrical Light
23 April 2016
circuit breakers (RCD) are special equipment to protect people from electric shock, as well as from possible fire and fires that result from damage to electrical insulation, electrical equipment and wiring.RCD effectively in a situation when there is a break protective conductors, touch to open live parts, problems and careless handling of electrical engineering.


In the event of a short circuit due to defects in the insulation system, the RCD seek out the leak current, and then perform actions that prevent a short circuit, namely, to prevent heating of the conductors and fire, within three seconds, disconnect the unit from the sourcesupply.

There were first the RCD in 1937 and had at its core a polarized relays, differential transformer, with a speed of 0.1 seconds and a sensitivity of 0.01 A. Already in the 60-70-ies of the RCD gained popularity in Western Europe, the US andJapan.

Today RCD actively apply for arrangement of industrial and socio-residential electrical, commercial vans and mobile
catering facilities, hangars and garages.Every day, manufacturers are developing innovative models of RCD, giving them greater functionality.

Two types RCD - AS and A, which are different from each other difference measurement circuit currents, and thus price.Speaker type used in alternating current leakage, but in DC leakage is necessary to use an RCD type A. circuit breakers type A is recommended for operation of washing machines, dishwashers and household electrical appliances.

circuit breakers can be installed on the control panel, or built into the wall outlet.Built RCD, in turn, can be:
  • installed on an existing outlet
  • or first connected to a power outlet and then connect to the appliance
  • RCD-plug

the first two types of devices are beneficial touse if not accommodate the replacement of wiring, however, are highly price - setting built RCD will cost three times more expensive than installing an RCD at the distribution board.

Another type RCDs are differential machines - breaker combined with an RCD.Differential machine responds to current leakage to ground, short circuit and overload.The most advantageous use of such a device is that if a cabinet is no space for two different devices.

How It Works

RCD is a momentary switch, the principle of operation is based on the response of the sensor to changes in residual current originating in the conductors by which electricity is supplied to the protected installation.The sensor is used as a differential current transformer, and a threshold element that determines the current level for the RCD, made on magnitnoelektricheskom relay with very high sensitivity.

In normal operation, the magnetic flux and the current that passes in the secondary winding of the transformer, have a zero indicator.

When a person touches the body of a faulty appliance or exposed conductive path through the conductor phase differential leakage current flows.

When current passes the threshold limit boundary element in the starting device, it responds to the influence of the actuator.You can monitor the operation of the RCD test by means of a chain, artificially create residual current.

RCD installed in the space - switchboard.When installing the RCD can be used one of the following types of installation:
• One protective device on the entire apartment or house (leakage current of 30 mA).Construction of this type will cost inexpensive and does not take much space.However, the leakage current and disconnecting equipment, the whole apartment will be cut off from the light.
• For each line one RCD (leakage current 10mA) and one RCD with a current of 30 mA on the female line.This installation method is more convenient for the owners of the premises, since failures will only disable the faulty line.However, to install such a system in an apartment, you will need to make significant expenditures and set aside for large area devices.Please note that it is necessary to design a special panel in the apartment, because in a cabinet at the site will not be enough space.In addition, it is necessary to establish the selective RCD with tripping from three to five seconds near the circuit breaker that protects the entire building.If during this time the first line of devices, responsible for the protection of a separate apartment or home appliances, will not have time to react to the problem, selective RCD will disconnect the entire power supply circuit.

When installing the RCD such mistakes are possible:
• Load connection with the compound of the neutral conductor, which are exposed conductive parts of the installation
• Connection to the RCD protective conductor
• The connection load neutral conductor to the RCD
• Jumper between the neutral conductorvarious RCD
• Connect load neutral conductor to another RCD

To protect themselves from potential errors, design and connection of the RCD must be left to professionals.

When installing the RCD should be aware of contraindications to the use, as in the case of mounting the device into the old wiring can react unpredictably.When installing the RCD in the Old scheme, it is recommended to use the socket with integrated RCD.