Rcd Connection To A Single-Phase Network With Grounding: Rules + Stages Of Work

Electric energy is used everywhere and extensively in the residential sector. It is one of the main energy resources, but its use is not at all safe. In order to ensure safety, different methods of protection are used.

In particular, connecting a RCD to a single-phase network with grounding prevents electrocution, equipment breakdown, and electrical wiring fires. But in order for the device to be able to perform these tasks, it is necessary to correctly select a protective device and competently implement it into the electrical network.

Solving these issues is the subject of our article. We will tell you what parameters are important to take into account when choosing a RCD, we will indicate the installation requirements for the device, and we will describe the procedure for connecting the device to a single-phase network.

What are the protective measures provided by a RCD?

  • Selection of the device according to the design data
  • Rules for connecting the apparatus
  • Work carried out by professionals
  • Instruction for households
  • Conclusions and useful video
  • What protection does the RCD provide?

    For sure, there are certain rules for the installation of protective devices in the electricity supply. Let's take a look at the installation of RCDs.

    The protective module in a series of such devices is designed as a universal device, so most models are designed to protect against various negative manifestations during the use of electrical networks.

    The RCD offers three directions of protection:

    • current prevention;
    • circuit breakdown followed by leakage to the equipment;
    • short circuit.

    We should note: all three directions of protection work best if the equipment is connected by a grounded circuit.

    At the same time, a circuit without ground is (and often used). However, in this case, the efficiency of the appliance is considerably reduced.

    RCD connection to a single-phase network with grounding: rules + stages of work

    Electrical protection equipment is already commonplace in modern electricity use. These devices have been steadily improved and today offer a wide range of protective functions

    RCD devices are considered a necessary component in all kinds of electrical distribution boards - fixed, temporary or mobile.

    It is not rare to find them integrated in socket and plug structures for connecting tools and appliances used in humid, dusty environments.

    Selecting the device according to the design parameters

    It is a real challenge. The current market for electrical appliances, including RCDs, is characterized by a peculiar assortment. This is the result of the lack of strict quality control by the state structures.

    There is a mass of different devices on the market, made by a large number of manufacturers, many of whom do not always follow the current regulations.

    The potential RCD owner has nothing else to do but accept the information that the manufacturer of the device provides. In addition to the guarantees is the certificate of conformity and fire safety.

    The absence of such documents on the sold product is a direct prohibition on installation and operation, according to the requirements of the applicable standards.

    RCD connection to a single-phase network with grounding: rules + stages of work

    About one such document, the certificate of conformity, should complete any device that is put on sale. If a RCD does not have a certificate of conformity, this is a clear reason not to buy (+)

    The choice of a RCD is always accompanied by a consideration of the operating parameters and characteristics that determine to a large extent the quality and reliability of the device.

    The rated values of:

    • voltage;
    • current;
    • switching current.

    These basic characteristics must correspond to the technical characteristics of the installation planned or the circuit in operation.

    The quality and reliability of the RCD is determined by a few parameters, whose general physical meaning is often difficult to grasp.

    These parameters are primarily the nominal rated short-circuit current and the rated breaking capacity.

    RCD connection to a single-phase network with grounding: rules + stages of work
  • The main operating parameters of devices such as RCDs are traditionally shown directly on the panel of the device itself. However, together with the main parameters, there are also some more or less secondary parameters that have a significant influence on the functioning of the devices (+)

  • It is not very often that RCD manufacturers mark all the mentioned characteristics in their documents. It is therefore necessary to correctly evaluate all the existing advantages and disadvantages of the selected devices.

    From a technical design point of view, RCDs are traditionally described as a switching device, the action of which is determined by the standby mode. The device has no signs to help visually determine the quality of operation.

    But there is a single principle on which such devices function in the same way. The device is plugged into the circuit of the operating current and if a leakage current of a certain value exceeds the set point appears, the RCD simply opens the power circuit.

    RCD connection to a single-phase network with grounding: rules + stages of work

    Despite the variety of RCD designs, the actual operation of these devices remains the same. The basic principle is to de-energize the circuit if the set leakage current value (+)

    How well does the disconnection work? It is only possible to evaluate the circuit performance, the switching capacity, the service life and other relevant parameters by means of a special test.

    Rules for connecting the apparatus

    There are standards which define the normal conditions for the installation and the subsequent operation of RCDs. These standards are fixed in particular in the documents GOST P 51326.1-99 and P 51327.1-99.

    The following criteria must therefore be respected when using RCDs in practice:

    • optimum ambient temperature range -5 + 40°C;
    • no relative humidity higher than 50% at +40°C and no higher than 90% at +20°C;
    • no altitude limit of 2000 m;
    • no strong magnetic fields in the vicinity of the appliance.

    As indicated in GOST R 50571.3-94, for connection circuits in buildings, an important and necessary condition for the normal operation of a RCD in the building installation is the absence, within its operating range, of any connection between the neutral operating conductor and the earthed parts of the installation and the PE protective earth conductor.

    RCD connection to a single-phase network with grounding: rules + stages of work

    Each device at its operating range is tested for leakage within a certain limit. This is called the sensitivity zone of the RCD protective device. In this zone, no connection of the neutral busbar to the earthing conductor is possible

    For the TN-C-S earthing system, separate terminals or busbars should be provided in electric installation boards at points where the PEN conductor is split, for the neutral operating N and the neutral protective PE conductors.

    Bearing in mind that a RCD reacts to earth leakage of both the neutral and the phase conductor, earth leakage circuit breakers should generally be provided in the lines.

    RCD connection to a single-phase network with grounding: rules + stages of work

    The classical TN-C-S type circuit, where an earth bar is an essential feature. According to many experts, this circuit is considered the best option for using RCDs (+)

    The introduction of circuit breakers allows the faulty section of the circuit to be detected quickly by disconnecting individual lines one by one.

    Mutual circuit breakers prevent the disassembly of the \"switchboard\" when a faulty section is detected, including the section with leakage through the neutral conductor.

    GOST R 50571.9-94 contains specific instructions to follow the action to protect the neutral operating and neutral protection conductors.

    Conducting the work by professional services

    In theory and in practice, too, with the participation of professionals, the installation of RCDs involves making arrangements for determining the tripping threshold of the device.

    RCD connection to a single-phase network with grounding: rules + stages of work

    The installation of RCD protective devices always requires a specific installation sequence. The first element in the sequence is usually the circuit breaker. Then come the meter, the RCD and the other parts of the circuit (+)

    There are rules laid down, a sort of manual where the sequence of operations in such cases is noted.

    How to proceed:

    1. First, the phase and zero load circuit is disconnected from the appliance, for which a circuit breaker is used.
    2. After this, the measuring apparatus and the adjustment elements (potentiometer) are connected to the RCD.
    3. By changing the resistance of the potentiometer, the tripping of the device is achieved and the current reading of the meter is recorded.

    The reading of the meter at the tripping time is the differential current of the RCD. The recorded current reading must be within the specified range.

    If the condition is not fulfilled, the protective device must not be installed in the circuit. A new one with suitable parameters must be found.

    RCD connection to a single-phase network with grounding: rules + stages of work

    Adjustment of an already installed device is a classical phenomenon in professional services. Thanks to a precise setting, the optimum protection is set and this has a significant effect on the general safety

    When connecting RCDs with earthed protection, the rules prescribe also the work to measure the leakage current within the protection area of the appliance.

    Such measures are generally necessary in the case of electromechanical installations:

    1. The load is connected to the circuit breaker.
    2. A test circuit is connected to the relay with a resistance store and an ammeter.
    3. Changing the resistance store, the relay trips and the ammeter is noted.
    4. The leakage current is calculated by the formula Iu = I - Ia, where I is the tripping current of the circuit, Ia is the reading of the ammeter.

    The resulting value Iu must not exceed the rated value of the RCD differential current by more than one third.

    RCD connection to a single-phase network with grounding: rules + stages of work

    The setting is accompanied by measurements of the different mode currents. Ammeters with a high degree of accuracy are used for the measurements. Only specialists can do this work

    If such an excess is detected, it is a clear sign that there is a defective section within the protection zone of the device. For these cases, the EAR rules require the execution of the necessary measures to eliminate the leakage current.

    Domestic installation instruction

    Installing a RCD in a domestic circuit, provided it has been adjusted to the parameters of the supply network, must respect a number of requirements.

    List of mandatory rules:

    1. Mounting on the input line and connection of the device must only follow the circuit breaker. It is usual to install the circuit breaker in between the two units in addition to the electricity meter.
    2. Installation must be carried out with the supply line completely deenergized.
    3. The rated current of the automatic unit must be chosen equal or slightly lower than the appliance differential current.
    4. The connections must be made in strict accordance with the symbols and the manufacturer's circuit diagram supplied.
    5. The connections on the load side are first made with phase and neutral busbars to the corresponding terminals of the appliance.
    6. Tightening the terminal screws is carried out with some force, sufficient to secure the connections, but without excessive force.
    7. At last, after checking that all connections are secure and free from defects, the device is connected to the output terminals of the automatic gas burner control unit.

    To install, adjust and start up the safety device, no formalities should be tolerated. All actions must be carried out carefully, with precise calculation and duplicate checks.

    RCD connection to a single-phase network with grounding: rules + stages of work

    After all the installation and adjustment work has been completed, a duplicate analysis is performed in the operating mode of the circuit. All measurements are recorded in technical logs

    In a domestic circuit, it is not uncommon to try to carry out the RCD and residual current circuit breaker connection by ourselves. You should always choose a professional installation - with the help of experts.

    Conclusions and useful videos on the topic

    This video clearly describes and demonstrates how to include a protection device in the circuit diagram of the power grid. Different schemes are considered:

    Familiarizing yourself with the rules for connecting the RCD and the order of work, as well as the specifics of installation in a single-phase network with grounding, you can try to do everything with your hands.

    But this option is justified only if you have a tuned protection device and certain skills for electrical installation works. Otherwise, the best solution is to invite an electrician.

    You have experience connecting a RCD yourself? Please tell your readers about the nuances of choosing a suitable protection device and the peculiarities of its installation. Comment on the publication, participate in discussions and add photos of your self-made products. The feedback box is located below.

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