To ensure safety in the house and protect a person from electric shock, residual current devices (RCDs) are most often used. They are triggered by current leakage. When buying such devices, people ask themselves: "How to check the RCD?" immediately before installation. In this article, we will try to answer this question.
What is an RCD?
As we have already said, RCD stands for "residual current device". They, like circuit breakers, are classified as electrical protection devices. But what's the difference? How to check the operation of the RCD?
The fact is that the RCD is triggered at the slightest leakage of current, while circuit breakers simply ignore small charges. They react only to overload currents or in the event of a short circuit. For example, if a child wants to learnsocket device with a metal object, it may be shocked by a small discharge current. It will pass through the body and go into the ground. The circuit breaker will not even respond to such a leakage of current. They start their action at a leakage of 30A.
To provide additional protection of a person from electric shock or fire due to damage to the insulation of the electrical wiring in household electrical networks, an RCD with a sensitivity of 10 to 300mA is installed.
How does it work?
If there are no problems with electricity, the currents in the phase and neutral wires will be equal, but oppositely directed. This will create magnetic fluxes in the core of the transformer, which will be directed towards each other, and therefore will compensate each other. In this case, the magnetic flux will be zero.
In the event that, for example, an insulation breakdown occurs, there is a difference in the currents of the wires. A leakage current will appear in the phase wire, which will be a difference for the transformer. That is, the magnetic flux will be different from zero, because magnetic fluxes of different values will appear in the core.
Then the law of electromagnetic induction comes into play. As a result, a current will appear in the control winding. If this current reaches a certain value, then the electromagnetic relay will work. It activates the release, and the power contacts of the RCD will open. The end result will be the de-energization of electrical elements protected by RCDs.
But howCheck if the RCD is working? Suddenly it doesn't work at all? To do this, right on the device there is a "Test" button. It is recommended to use it from time to time. When this button is pressed, an artificial leakage current occurs. If everything is in order with the device and it works properly, then it should work and de-energize the electrical appliances under her control.
Tools needed to test the RCD
Before we learn how to check the RCD, let's figure out what tools you can use to do this at home.
Almost everyone can check with the help of improvised means, and be sure that the residual current device is working. So, to carry out this check, we may need:
- wire with plug, in order to apply voltage to the RCD;
- wire with cartridge, in order to connect an electric lamp;
- electric lamps of different power;
- power tools such as a knife or screwdriver.
During the RCD test, it is recommended to measure the mains voltage. It is usually between 180-240 V. This may be important during the test.
What do we check?
In order to test the RCD at home, as we indicated above, you need a set of simple improvised materials. With their help, we will be able to explore 2 aspects of the operation of the RCD.
To begin with, we will make sure that the purchased RCD is working properly and can be connected to the network. As well aswe will evaluate the correctness and speed of the RCD in the event of leaks.
The easiest way to check
To implement this verification method, we do not need the listed tools. All we need is a regular battery and a piece of wire. You can immediately take them with you to the store when you are going to purchase a residual current device.
In qualified shops, you can also request that the RCD be checked by the seller in your presence.
So, how to check the RCD with a battery? Everything is very simple. To do this, you just need to turn on the RCD, that is, turn the button to the "On" position, connect the battery between the ground input and the phase output. When the device is working properly and the battery is charged, the device should fire and turn itself off. You should hear a click and the button should move to the off position
It may be that the first time you check will fail. Try again by simply flipping the battery over.
This verification method is the easiest, since it can be carried out without connecting the RCD to the electrical network and without leaving the cash register.
Checking a single-phase RCD with a sensitivity of 30mA
Before you check the RCD for operation, it must be assembled. To do this, we attach the ends of the wire with a plug to the upper terminals, and the ends of the wire with a cartridge to the lower terminals.
To test an RCD with such sensitivity, we will have enough light bulbs withpower of 20 watts. We screw it into the cartridge and turn on the plug.
Then turn on the device. To do this, translate the key "Off." on the device to the "On" position. If you assembled and connected everything correctly, then the light should light up. This procedure is recommended to be repeated 3-4 times. That is, turn the device on and off.
Then, leaving the RCD on and the light on, press the "Test" button on the device. If the device is working correctly, it should turn off, turning off the light. We repeat the procedure 3-4 times, after turning on the device again.
Now we need to check if the RCD will turn itself off when a leakage current is generated. We artificially create this leak. We take the free end from the lamp that is not fixed in the terminal block and disconnect it from the RCD. The lamp will turn off, but the device will remain on. Then we touch with a disconnected wire, for example, a grounded frame from a circular saw. You can also use any other grounded place so that the leak is, but does not harm any device, but goes into the ground. Normally, the RCD is turned off.
Checking a three-phase RCD with a sensitivity of 300mA
The main points of how to check the RCD for performance, we described above. Thus, the beginning of the check will be identical. We assemble the device as described above.
The only feature is that we connect the upper terminals with a loop from one network wire, and the second wire to the N terminal. We connect the lower terminalsas follows: one end of the wire to the N terminal, and the other end remains free.
Next, we will check each phase pole of the RCD with the free end of the wire. We plug the plug into the socket, turn on the RCD and check all the phases in turn. If they are all correct, the light will be on.
Also, for each phase pole, we check the operation of the "Test" button.
When checking for operation in emergency situations, bulbs from 40 to 100 watts must be used. The RCD should not work on a 20 W lamp, since the leakage current is not included in the response range of the RCD of such sensitivity. If the device does not work with other lamps, then it is defective and cannot be used.
Here we have learned how to check the RCD before connecting it to the network.
Safety Practices
When carrying out RCD checks, we are dealing with electricity. This can be fraught with unpleasant consequences. Therefore, before checking the RCD, you need to familiarize yourself with the precautions and observe them during operation:
1. All operations for connecting and disconnecting circuits must be done with the voltage removed (remove the plug from the socket).
2. Bare hands should not touch any bare wires.
3. Protect yourself from electric shock with the help of protective and auxiliary means (there must be a dry place for work, it is better to lay a rubber mat or wooden flooring under your feet, work with an insulated installation tool, whenthe need to use rubber gloves, etc.).
4. If you do not have the slightest idea about electricity, then it is better not to carry out the work of checking and installing equipment yourself.
