The RCD is a residual current device that serves to protect a person from a current shock. It is also used as a fire protection, with leakage current. RCD in the apartment, office, in a private house, on the job site and production - one of the guarantees that you and your colleagues, domestic and other people will not be electrocuted.
What is RCD and how does it work? For clarity, we give a vivid example. Everyone has a home appliances that fully or partially consists of different metals or has metal parts. There are times when there is a dangerous chance of getting an electric shock from these metal parts. For example, a heating tenon broke through, or your child for some reason got his fingers into the socket. In this situation, we are just getting used to an RCD in an apartment, which will open the contacts and will not allow you to get an electric shock, which often turns out to be a serious injury or a fatal outcome.
Trips the RCD according to the leakage current measurement principle. If the same amount of current comes as it's gone - the RCD works. With a leakage current, the device shuts down. The RCD in the apartment is a guarantee of your safety against accidental electric shock.
Differences between the RCD and the Difa Automaton. Video
Classification of RCDs
Consider several types of RCDs. Knowledge of their classification will help to correctly answer the question "How to connect the RCD?".
RCD-E
These are capacitive RCDs with the highest sensitivity, which are performed for lightning-fast operation. They operate on the principle of a capacitive relay, that is, they react to a capacitive current. The disadvantage of such RCDs is the presence of electromagnetic interference.
УЗО-Д
Differential RCDs operate on the principle of measuring the currents of the departed and those who arrived. If the currents are equal, the RCD in the apartment works perfectly, if the currents are not equal, that is, a leakage current appears - the device shuts down.
УЗО-ДМ
This is a variant of the differential device - mechanical. The most common type of RCD, developed in the 80's of last century. The principle of operation remains unchanged, only the appearance of the device changes over the years. The prefix DM was removed, now it is written and it is said simply by the RCD.The principle of this RCD is as follows. When the current changes, the magnetic flux also changes, which induces an electromotive force on the secondary winding( in the textbooks on the physics of EMF).In this case, the electromagnet pulls the latch of the contactor mechanism and the equipment switches off. With the creation of an electromechanical RCD, it became possible to combine a current automatic device and an RCD.
RCD-
Electronic protective circuit breaker. Such a RCD is usually located in sockets. It is characterized by high sensitivity and lightning-fast operation. This is really modern equipment, which does not raise questions about how to properly connect the RCD.The drawbacks are the price and the fact that it's still electronics, which means it may not work for voltage dips.
Importance of RCD indexes
Connection scheme for RCDs
Basic indices of the RCDs
- AC.Operate with an unbalance of about 100 mA of the AC component. The optimal price-quality ratio.
- A. Protective RCDs with an unbalance of 30 mA.There may be false alarms / malfunctions in the TN-C system, and in the TN-C-S system, they may occur if the grounding is poor.
- B. Respond to leakage currents of any kind.
Additional indices
- S. The response time of the device is from five thousandths of a second to one second. It is used in power supply of industrial facilities.
- G. These are high-speed and ultra-fast RCDs used in kindergartens, hospitals and educational institutions - that is, where safety with regard to accidental electric shock is particularly important.
How to choose a RCD
How to choose a RCD?One of those issues that worries many people who decided to make an installation to protect people from electric shock. In order to select an RCD that is ideal, you need to know the rated current;leakage current, which is equal to 30-100 mA;pick up the cut-off value when overloading, and finally decide what to put. The choice in this case is limited to a difa-automat or a separate RCD.If you live in an old house, where there is a two-wire network, you will not be able to put the difa-automat. If the system of the electrical network is three-wire, then it is possible to put both a difa-automat and a separate RCD, if the machine is already standing.
How to connect the RCD and calculate the overload?
How to properly connect the RCD, so that you do not have to worry about the problems that might arise when connecting incorrectly, you will find out today.
For this we need to find out in the technical passport of the house or apartment the maximum current consumption, and multiply this number by 1.25.
Suppose the maximum current is 16A.Multiply by 1.25, we get 20A.The rated current of the RCD is higher than the cutoff current of the machine. In our case with a current of 20A we take 25A-rated current of the RCD.
Connecting the RCD in the apartment or connecting the device in a private house, at the cottage, in a cottage can be done with the help of a specialist or try with your own hands and minds. Strict adherence to safety rules is important.
How to connect the RCD.Video instruction
The connection diagram of the RCD is unique for each electrical network. Often it is located directly near the source of electricity. A residual current device can be installed as a single unit, that is, there is one RCD for each line, and a separate RCD for each line. In the first case, if a protection system is triggered, it will be difficult to find the cause of this operation. Can, among other things, divide the current in the whole apartment. In the second case, we will immediately see which RCD has worked, and the cause will be easier to find. The only drawback is the size of the electrical flap. It is too big and can take up a lot of space.
Wiring diagram for RCDs and circuit breakers. Photo
The circuit of the RCD connection informs us that the power comes to the input automaton in 50 A, from the machine to the electricity meter, from the meter both wires - phase and zero - go to the UZO-63A.From the residual current device, the phase wire goes to the machines to which the outlets will be connected. For example, zero with RCD goes to the terminal block-zero N.
Wiring plan for three-phase RCD.Photo of
If you realize that you are able to independently connect the RCD, then follow some recommendations. An important point is the connection of wires to the terminals of the RCD.Do not confuse the terminals and wires, in order not to short circuit and do not damage the device.
If you are confronted with the choice of how many RCDs to install, then count how many spaces can be dangerous for you and your loved ones with regard to electrical safety. If the financial possibilities permit, then it is possible to put a separate RCD at each outlet. True, this is inappropriate, since many sockets will rarely be subjected to connecting and disconnecting devices. Usually devices are included in the network and there remain - TV, desktop PC and much more. Select only those sockets and rooms where there may be an electric shock. This will save space in the electrical panel and your money.
How to check the RCD for operation of the
RCD without ground
The RCD without grounding is installed and operates as well as with the ground. Its properties do not change, it also works, as well as the RCD, which works with grounding. Disconnect the RCD without grounding will be by leakage current to the conductors, which can be like a person, so conductive objects. In this case, you choose which to choose the RCD connection with grounding, or without.
Taking into account all the nuances of installing an RCD in a private house and apartment, it is possible to sum up and outline an approximate plan for how to connect the RCD better and more economically. This is a whole complex of diverse works, so it is important to do the preparatory part of the work - choose which device you prefer, and then call a specialist. If the skills in the electrician make it possible to conduct the RCD independently, it is better to read about it as much information as possible. Finally, when the protective shutdown device is installed, you will be assured of the safety of your family from accidental electric shock.
