The protective automation of the home power network, located in the control cabinet, is a necessity dictated by safety. A lot depends on how correctly it is chosen. Such equipment can turn off the power supply during overload, power surges or current leaks that can harm a person. In this case, each device is responsible for its area of protection. Today we will talk about how the RCD differs from the machine, what functions these devices perform and how they are arranged.
Home Power Protection Devices: Definitions and General Information
First you need to understand the difference between such automation and in which cases its use is justified. Such devices are divided into 4 main types:
- Circuit Breakers (AB).
- RCD.
- Automatic machines of differential current (AVDT).
- Relay for voltage control (LV).
To make it easier to understand how RCD differs from a differential automaton (for example), it is worthwhile to analyze in more detail what each of the listed devices is responsible for.
What is AB and what functions does it perform
A protective circuit breaker is a complex device consisting of a static solenoid and a movable rod located in it. With stable operation of the electric network, a current flows through the solenoid that does not affect the functionality of the machine. If many different devices with high power consumption are connected to the line, the parameters change. Increasing the current in the solenoid pushes the movable rod, which acts on the contact group, breaking the circuit, as a result of which the voltage supply to the group of the home power supply is interrupted.
Of all the protective automation devices, AB is considered the simplest. Its functionality allows not to protect the home network from overloads and short circuits, but provides the prevention of the consequences of such cases, such as overheating and ignition of the wiring and the possible subsequent occurrence of a fire. And what is the difference between a conventional machine and an RCD?
Residual current circuit breaker: equipment features
The difference between the RCD is that it performs a completely different function, the purpose of which is to ensure the safety of not a wiring, but a person. The device turns on when a situation occurs when the current-carrying wire is in contact with the metal housing of the household appliance. In this case, a leak occurs, which is fixed by the RCD. This causes a cut-off and a power outage. But the main thing that distinguishes an RCD from a circuit breaker is the lack of response to overloads and short circuits. If there is no AB in the circuit, and a short circuit occurs in the home electrical network, the device will simply burn out, and the voltage will not be cut off.
Similar features of protective equipment dictate certain rules for their use. In distribution cabinets, a pair connection of UZO and automatic devices is used, in which the maximum safety is achieved both for a person and for electrical wiring of household appliances.
AVDT: what is it and what is it for?
Often, distribution cabinets are quite small in size, and it is impossible to place all the protection devices that are planned in them. You can install a larger box, but sometimes you need to expand the niche (with its built-in location), which is not always possible. The way out of this situation will be the use of a differential machine that performs the functions of two devices at once - AB and RCD, but takes up less space. In addition, installation in this case is simplified.
It is worthwhile to understand how the differential differs. machines from RCD. The answer to this question will be a short video in which everything is described in detail.
Such combined devices have many advantages, however, they could not do without negative aspects. The pros and cons of residual current circuit breakers should be considered in more detail.
Advantages and disadvantages of a combined device in front of a bunch of AB + RCD
Information about the pros and cons of ATS for the convenience of perception and clarity is presented in the form of a comparative table.
Positive sides of the differential automaton | Negative qualities of AVDT |
Takes up less space on the DIN rail. For installation, 2 modular places are required, unlike a bunch of two devices, for installation of which 3 are required. | It is difficult to determine the cause of the operation - leak or overload. When using a bunch, the answer will be obvious. |
Connecting an AEDT is much simpler, which reduces the risk of improper installation. | The cost of the device is higher than that of a conventional machine and RCD combined. |
It does not require additional protection - the differential automaton is quite integrated. | Failure of one part implies a complete replacement of equipment, while when using two devices you will only have to buy an AV or a residual current device. |
The question "what is the difference between a differentiated automaton and an RCD" remains to be returned, but now it makes sense to understand what the LV is.
Voltage Monitoring Relays: Application Features
Power surges and power drops are not uncommon for our power networks. Particularly susceptible to them are houses in private sectors. Such swings can easily disable complex, expensive household appliances and electronics. But the purchase of stabilizers or uninterruptible power supplies is not a cheap pleasure, and it is not always justified. The best option is to install a voltage monitoring relay, the upper and lower threshold of which are set by the user.
If the voltage drops below or jumps above the programmed values, the device turns off the power supply for a certain time. After passing it, the device closes the circuit again. If the cause of the operation is eliminated, the voltage is supplied in the normal mode until the next similar situation occurs. This allows you to protect household appliances and electronics from the harmful effects of power surges. Also, the voltage control relay will save in the event of a short circuit of one of the phases to the neutral wire. This often happens when in the private sector the veins of an overhead power line sagged over time. With strong winds, the phase wire overlaps with zero. As a result of this, 380V can be supplied to the devices. When this situation occurs, the voltage relay will not allow dangerous current to reach devices connected to the home power network.
What is the difference between RCDs from a differential automaton and what is the similarity of devices
If we take into account the dimensions, then everything is the same. The residual current device takes 2 modular places, as well as a residual current circuit breaker. However, as already mentioned, if a short circuit occurs on a line that is equipped only with an RCD, no cutoff will occur, the wires will begin to heat up, which will cause them to ignite and fire. The differential automaton will not allow such an outcome. In case of overload or short circuit, it will instantly turn off the power supply, like a regular AB. But the difference between the RCD from the machine is the ability to detect current leakage.
Most people are familiar with the unpleasant sensations when, when you touch the body of the household appliance, a slight electric shock is felt. This can happen due to high humidity. If a breakdown of insulation occurs, then the discharge can be several times stronger, and the consequences are very deplorable. The RCD is designed specifically for fixing such leaks and turning off the power when they occur. The fact is that in such a situation there is a difference in the current entering the phase conductor and returning to zero. It is taken into account by the residual current device.
It remains to give an answer to one more question: what is the difference between the difavtomat and RCD? The differential current circuit breaker, in contrast to the residual current circuit breaker, responds not only to leakage, but also to various overloads. If several devices with high power consumption are connected to the sockets of one line, the AEDT will interrupt the power supply, thereby protecting the wiring from heating, and the contacts of the connection points from burning out.
Rules for installing equipment in a switchboard
Despite the fact that the residual current device can be switched without grounding, complete safety in this case cannot be expected from the device. However, in some cases there is no other way. It is not difficult to figure out how to connect the RCD and the machine correctly, but the work requires maximum care and accuracy. The first thing you should pay attention to during installation is the presence or absence of a ground bus in the switchboard. It must be installed separately from the zero level and should not be in any contact with it.
Only a phase wire is connected to a conventional machine. Placing it on a DIN rail, you should make sure that the inscriptions on the front are not upside down. With the correct location, the upper contact will be an input, and from the lower voltage will go to the home network or other automation.
RCD connection is slightly different. Here 2 wires come to the upper contacts - phase and zero, and the lower terminals are tap-offs. First you need to check the functionality of the residual current device. To do this, the flag switches to the “on” position and the “test” button is pressed - the RCD should work the same way as with a leak.
Helpful information! If, after installation, the residual current circuit breaker trips periodically for no specific reason, incorrect connection or wiring of outlets is possible. You will have to check all connection points and junction boxes. Perhaps in one of the places allowed the connection of the ground and ground wires.
Selection criteria for RCDs and circuit breakers
Before purchasing such protective equipment, it is necessary to determine the technical parameters that are necessary for a certain amount of household appliances and its power consumption. Here, one should not be guided by the information about how the RCD differs from the machine, but, on the contrary, by the similarity of some characteristics. It is understood that these devices will work in pairs, which means that the maximum current load of the devices must coincide, although a lower indicator is allowed on AB.
Before picking up an RCD and an automatic machine, you need to add the current load of all household appliances into groups. Also, the total amount for all lines will be required. If this indicator does not exceed 16A, it is entirely possible to do with one RCD. Otherwise, you will have to purchase devices by the number of groups or protect individual lines that supply more expensive equipment.
As for the cost, the products of famous brands will cost more. But experts do not advise taking advantage of the opportunity to purchase cheap protective equipment from unknown manufacturers. Such an acquisition will at best require replacement after a short period of time. At worst, it may not work at the right time, which will lead to sad consequences.
It is not necessary to purchase such equipment through the Internet - RCD, AVDT and AB may be inoperative, and returning or exchanging in this case becomes quite problematic. The best option would be to buy protective automation in large, well-established electrical stores, in which sales consultants who know the specifics of the product work. They can talk about the product, and if the outlet value their reputation, they will not conceal the negative sides of the products from the buyer.
Checking the performance of RCDs upon purchase
When purchasing a residual current device in an ordinary store, you need to understand whether it performs its functions. This is pretty easy to do. Before going to the store you need to prepare a regular 1.5V battery, 2 pieces of wire, each about 10 cm long with stripped ends and a screwdriver. The verification algorithm is as follows:
- The wires are connected to the two contacts of the selected RCD (the input and output terminals are used, phase or zero - it does not matter).
- The second bare ends, when the device is turned on, are connected to the plus and minus of the battery. If the RCD is operational, it will turn off.
The reason for the operation is quite simple. By connecting the battery, the user creates a certain voltage on one of the coils, the second, at the same time, remains without load. The RCD considers this state of affairs as a leak and shuts down. This method is simple and safe, and therefore feasible at any outlet. You can similarly check the device installed in the switchboard, but for this you need to disconnect the wires that are suitable for it.
What to choose?
Everyone should give an answer to this question independently on the basis of the size of the distribution board and financial capabilities. Having figured out how the RCD differs from an automatic machine and an AEDT, it will not be difficult to make a decision. You must understand that you should not save on your safety. And how the protection will be implemented is not so important. The main thing is that it should be comprehensive and efficiently fulfill the duties assigned to it.