Residual current protections

What is differential current, where does it come from?

As the name suggests, this is the difference between the currents flowing through the phase wire to the user and through the neutral working wire back. The sensing element is a differential transformer installed inside the device.

In normal operation of the network, these currents are equal to each other. When an accident occurs, a leakage current occurs, i.e. the "in" current is less than the "out" by the amount of the leakage current. If the network leakage current is equal to or higher than 50% of the residual current protection setpoint, the device breaks the protected line.

Residual current protection is more often installed on group socket lines, consumer lines in contact with water (washing machine, boiler, dishwasher, etc.). Thanks to the use of residual current protection, it was possible to significantly reduce the level of electrical injuries during the daily operation of various types of electrical equipment. The 10mA and 30mA leakage current RCDs are designed to protect a person from electric shock, and the 100mA and 300mA RCDs are used to protect buildings from fire which can be caused by insulation aging and heating of current carrying elements on the network.

Types of residual current protection.

The first and simplest type is residual current protection, which is triggered when AC leakage occurs. This type of residual current protection is usually called AC type. Residual current protection devices of this type are marked either with the inscription AC or with the symbol ac "~" on their housing.

The second subtype of devices is considered a device for triggering in the presence of alternating or direct (pulsating) current in the circuit or with its slow growth. This type is called type A. Devices of this type are marked with a symbol or a rectangular symbol with two tildes (of different amplitude).

The third subtype of devices is considered a tripping device when direct, alternating or rectified leakage current occurs. Such devices are marked with a symbol on the case and are intended for industrial use.

The first two subtypes can be used at home. There are several subtypes of residual current protection according to their principle of operation: electromechanical and electronic.

Subtypes of residual current protection

Electromechanical residual current protection is characterized by the fact that the operation of the device does not depend on the mains voltage, but only on the leakage of current in the damaged line - differential current.

Electronic residual current protections, on the other hand, are voltage dependent and require an external current source to operate with an integrated circuit with a built-in electronic amplifier. This type is less common due to less reliability compared to an electromechanical device.

According to the number of poles, all residual current protections are divided into: two-pole (2P) and four-pole (4P). The main difference between these types is the use of the device in a single-phase or three-phase network. 2P devices are used in a single-phase network, and respectively 4P in a three-phase network.

Selection of residual current protection

Having understood the main technical characteristics and the principle of operation of residual current protection, we will try to determine which device to choose to protect your own network. Not everything is so unambiguous and we will analyze everything in order.

The first thing to start from when choosing the residual current protection is the purpose of the line on which it will be installed. If the residual current protection will be installed on a group of devices that come into contact with water or sockets in the bathroom / kitchen, then it is necessary to stop at the residual current protection with a leakage current of 10 mA, if it is necessary to protect household contacts in living room or office, a residual current protection with a leakage current of 30 mA should be stopped. In the case when the protection is installed at the entrance, in front of group devices, then you should stop at the residual current protection with a leakage current of 100mA or 300mA (depending on the total load and length of electrical wiring in the room).

Second, residual current protection and combined residual current protection?

If space is limited in the electrical panel, then it is worth stopping at a combined residual current protection. Since it will not be necessary to install overcurrent protection in the form of a circuit breaker in addition to residual current protection and take up additional space on the DIN rail . The advantage of separate assembly of residual current protection and circuit breaker is that in case of operation, you can determine the reason for its elimination: from overcurrent or from differential current, and in the case of combined residual current protection, the reason for operation without additional manipulations will not be able to determined, except in cases where the device has a separate handle responsible for indicating the reason for operation. Such devices in our product range are e.elcb.stand. Another advantage of a separate installation of RCD and circuit breaker is simple replacement, if the circuit breaker breaks, then it is cheaper to replace it than to replace an expensive combined RCD.

Third, Type A or AC? In the case when there is a load with a switching power supply (washing machine, microwave oven, computer) in the protected line, then for reliable protection it is worth installing a residual current protection type A e.rcbo.pro, if the load is without such a unit (boiler, electric jug, etc.), then for complete protection against electric shock, residual current protection for alternating current will be sufficient.

Fourth, electromechanical or electronic residual current protection? The choice of electronic residual current protection can only be resorted to in order to save money and in the case where there is a higher or lower electromechanical differential protection in the same line, since only electromechanical devices can protect against unacceptable fluctuation of the voltage or burnout of the neutral working wire.

Fifth, marginal exclusion capability. Depending on the design level of the short-circuit currents, you must determine the tripping capability of the residual current protection. In the Enext product range there is an e.industrial.elcb residual current protection with a maximum value of 10 kA.

We have analyzed only the main characteristics when choosing a residual current protection, it is additionally necessary to take into account the technical indicators of each residual current protection, which the manufacturer indicates in the passport of the device.

Be responsible for the safety of yourself and your loved ones, choose residual current protection from the ENEXT company.

Devices for different types of tasks and different price segments that you can find in our online store.

What is differential current, where does it come from?
Types of residual current protection.
Subtypes of residual current protection
Selection of residual current protection