In today's world it is difficult to live without electricity. But for such types of energy, maximum protection is required. Therefore, high-quality installations are always created that can realize this. Modern developments in this industry create all the conditions for mutual contact. RCD is a device that is difficult to do without.
Not everyone understands what it is. For clarity, it is worth knowing the designation, purpose, principle of operation. Information about this will be presented in this article.
About protection
Without electricity, it is difficult to imagine human life, but it is also required to create conditions for protection against defeat. The most elementary is the insulation of the wiring, but it will not work to wrap everything completely. Because the circuit must have technical breaks and contact groups. But no one rules out the possibility:
- Insulation wear.
- Wiring break.
- Safety violations.
- Incorrect operation, etc.
Therefore, insulating and grounding is the best solution. But this was not always enough. Therefore, many years ago, the first RCD appeared in Germany. Its designation is in the diagram below.
How does this system work? It assumes:
- Leak sensor minimum size.
- Polarized magnetic relay. Its sensitivity is not more than 99 milliamps.
It was not possible to create something unique and faster in past centuries due to the lack of appropriate materials. But already in the twentieth century, improved developments appeared. The main thing is that protection against false alarms during bad weather was created. In addition, they went from a large size to a more compact one, able to sit on small stands.
Today, developers do not stop there, and in the near future, protection systems against electric shock with artificial intelligence will be made. Thanks to the developments, the device will perform maximum functions and, if necessary, notify users.
What kind of device and how does it work?
Everyone wants to know the RCD designation. As we have already noted, this is a residual current device. What does RCD protect against? The device has the function of protecting a person from electric shock, as well as from the likelihood of ignition of wires and other installations.
RCD - what is it in electrics? The action is based on laws that are based on incoming and outgoing electricity in closed circuits with maximumloads.
This says that the current must have the same value, regardless of the phase of the passage. Then everything is simple. When a person touches a bare wire or breaks, the indicator in the wiring changes its value and jumps. For the RCD, this is a signal to turn off. It is this system that is taken as a basis and implemented in installations.
The whole process is thought out to the smallest detail, so even minor power leaks are recorded. To understand the principle of operation, it goes like this:
- When there is no violation – Iin=Iout.
- If during operation there is a change in the current in the network, the RCD trips and the network turns off - Iin > Iout.
In this symbol, each has its own meaning - input current and output. RCD has its own designations. They are used in electrical circuits, and people with experience know about them.
Working principle
We already know the purpose of the RCD - this is protection against short circuits. Protection is carried out in the following directions:
- Shortcut. When a phase wire fails, it is on many household appliances - automatic machines, water heaters, dishwashers, etc. Breakdown often occurs when the main element is heated.
- Violation of installation rules when laying electrical wiring. If it was removed under the plaster, then the RCD will work until the repair is completed.
- Disconnection in electrical panel. If createdconditions under which there is a slight loss of current, then the efficiency of the entire installation as a whole is questionable. For this reason, protection is triggered.
If you look at the diagram, you can't see the violation, but the RCD works. This speaks to its accuracy and the smallest fixations. It also happens that an inexperienced person cannot find the reason for the shutdown. Only careful analysis will lead to the result.
Exceptions
Although there are exceptions to the rule. There are situations in which when an animal or a person enters an electrical installation, no reaction occurs (due to falling into phase and zero). For this reason, secondary protection is sometimes required.
Where does it meet?
It is important to understand the purpose of the RCD and how it works. The device has been widely used in everyday life, in many installations. Sometimes a circuit is developed at the input, but is not excluded on each device. The fact is that RCDs for powerful small devices are cheaper. But in places of group stay of people it would be advisable to apply it extensively. In this case, the division takes place in groups - all wiring is not turned off, which is convenient.
Most often, RCDs of a selective type are used. It is based on the same system of work, but the response period is slower. The principle is not to turn off the entire network, but to work in sections (where the loss has passed, the system has been de-energized there). For example, if music is playing in a restaurant, there is a short circuit and a different charge of energy, then only the equipment will turn off, and the rest of the light will remain on.
In AC installations, there should be re-protection with an applied RCD for sockets. This applies to various household appliances. Bit depth is of great importance when choosing. Not everyone can know how everything works, but it is necessary to understand the safety rules. The RCD system is not so common, so some mount it themselves.
The easiest device to understand is a water heater. What type of RCD and its application here? There are several options:
- By the occurrence of voltage.
- By current leakage.
- By response time.
When a person is in the shower or just washing their hands with warm water, there will be a power leak. The current will not hit him, since the RCD is triggered. Experts believe that in order for this installation to function in the house, it is important to correctly distribute the wiring. Sometimes the old one fails to do this due to incorrect input from the pillars.
Device operation
When you press the "Start" button, the operation of the RCD starts. The voltage of two points is measured. One is the flow of energy, and the other is the protection required. Voltage should not be present in the second section. When voltage appears in the area under the protection of reaching its predetermined value, the RCD turns off the input. This is voltage protection.
Current protection
Through the built-in transformers, the input and output current is measured. In normal mode, the difference between these indicators should be zero. When creating an emergencysituations when current leakage occurs and the value is dangerous for a person or animal, the RCD turns off the input.
Differential RCD
The alphanumeric designation of the RCD in this case is QFD1. It characterizes itself in terms of fast action. The larger the leakage current, the faster the tripping speed. Other types of RCDs operate at specified time intervals. Always at any rate, the shutdown time is standard. The advantage of a differential RCD is that it measures current and voltage.
Often, when connecting a residential building, inspectors are ordered to make an RCD on the meter. This is written in the technical connection, the wiring is carried out taking into account the requirements. In the switchboard, an RCD and an automatic device are installed. As a rule, people without experience do this, and when the master sees this, many errors are revealed. For this reason, no operation occurs. Before installation, it is worth understanding the operation of the RCD. What is it in electrics, we have already considered.
Connection without errors
It is important to make a competent connection not only to the energy source, but also to each other. There are two main options:
- The most common and frequently used is the main machine - the accounting counter - RCD.
- What will work more efficiently: the main machine - the accounting counter - the RCD of the selective type - the group machine - the group RCD.
RCD symbol onthe electrical circuit has its own symbol - D. Specialists in them read and understand how the entire system functions. There are rules not to be broken:
- After exiting the residual current circuit breaker, the zero indicator wire must not be connected to the ground terminal. Because it gives the possibility of current leakage and false trips.
- It is important to connect the RCD completely. When the power wire goes past, a current appears in the neutral wire. This is perceived by the system as a violation, and protection is triggered.
- There are neutral wires of sockets that are checked by the RCD. They must not be fixed to ground. Because there will be a power outage with small fluctuations.
- When group protective settings are created, it is impossible to overlap the neutral wires on the incoming terminals. This will cause the whole installation to react defensively.
This is the reason why the preliminary scheme is always executed. Otherwise, even a specialist can get confused. The process is not always complicated, there are devices whose operation is easy to set up. It is important to take into account all the errors that can occur on the network. When everything is correctly entered into the circuit, the operation of the RCD brings an effect. Today there are analogues of such a protection system. But before choosing, you should understand how they work.
Pay attention
Now we know the decoding of the RCD marking. In any case, when working with electrical appliances and installations, one must not forget about safety precautions. It is worth periodically doing a visualinspection of all wires. In case of damage, you do not need to delay the repair. Otherwise, the power supply will be interrupted because the safety device in the room will operate.
