RCD protection

The residual current device (RCD) consists of a sensitive element that reacts to changes in the monitored value, and an executive body that disconnects the corresponding section of the network. The sensing element can react to housing potential, earth fault current, zero sequence voltage and current, operating current.

The purpose of the RCD is to protect against electric shock by disconnecting when there is a danger of a short circuit to the equipment case or directly when a person touches live parts. In simple terms, this is a device that measures the amount of current that has come to an apartment (or any other

room) and out of it.

At the slightest insulation violation or other variants of current leakage, the circuit will be broken. By doing this, you will protect yourself, your apartment, dacha from possible troubles during the operation of your electrical equipment. What happens in the event of a short circuit, current leakage, or a person touching live parts of the device? The balance of the magnetic flux is disturbed, and a current appears in the secondary winding of the transformer, the threshold element relay reacts to the actuator, which acts on the principle of a release, and de-energizes the wiring circuit.

Fuses of different types, protecting the internal electrical network of the premises from short circuits and overloads, thereby protect electrical equipment from damage and breakdown. To a certain extent, these devices protect the very inhabitants of an apartment, cottage, etc., excluding the possibility of dangerous situations. However, they cannot protect people from the effects of current in the event of a wiring malfunction (when there is a leakage of current from the network to the body of the device) and do not protect people from electric shock when touching a bare wire or the body of a faulty device. where exposure to moisture can destroy the insulation of conductors and create conditions for current leakage to metal parts and objects.

To protect against electric shock, the so-called RCDs are used - disconnection protection devices. Such a device is small in size and can be placed in a switchboard and even in a socket. The RCD works in tandem with a circuit breaker-disconnector and instantly cuts off the voltage supply in the event of a person touching the bare wire, so that the leakage current does not have time to bring harm to health. RCDs can have different sensitivity and can, when paired with a circuit breaker, interrupt the circuit not only in case of direct contact with a live part, but also in the event of a malfunction in the device or in the wiring that causes the formation of a leakage current. It may seem to you that the RCD actually duplicates the circuit breakers, because they perform the same protective functions in the event of a short circuit or current leakage.

But it is not so.

The RCD has an advantage over a conventional circuit breaker:

In addition to protecting electrical wiring from short circuits and fires, this device also protects a person, reducing the risk of electric shock to a minimum. If you decide to add a residual current device to the wiring system, then it should be borne in mind that there are two types of such devices: electronic - dependent on the supply voltage and electromechanical - independent of the supply voltage.

The disadvantage of electronic devices is that their performance depends on the presence of current in the circuit. But when the neutral wire breaks, the circuit breaks, but the voltage remains (the wire with the "phase" remains energized). Electromechanical RCDs are devoid of this drawback and operate regardless of the presence or fluctuation of voltage in the network. Therefore, it is advisable to use electronic devices only as an additional safety net for other protective devices in the most dangerous areas of the electrical wiring (for example, in the bathroom).