RCD , protection of human and household appliances

basic protection of the human body from dangerous voltage and action of the electric current in the household and electrical powernetworks is to install protective device (RCD).In addition, the RCD is used to protect electrical appliances from emergency modes of operation for domestic and power networks of direct and alternating sinusoidal current.But very often it picks up and domestic consumers wondering why is switched off or RCD at the constantly activated RCD.

principle and operation of RCDs

Fig.1 Work RCD

current amount are included in the site, should be equal to currents that go.This is the main principle of this machine breakers.The reason for tripping RCDs elektropitanieeto that the currents that come from the area of ​​electrical networks are not equal currents that are part of this network.This difference is called the amount of leakage current, or it is called the residual current.The vector sum of the currents in the phase conductors ( I1 ) must be equal to currents in the neutral conductor ( I2 ).They are the same in magnitude but in different directions towards and thereby offset each other and the EMF (electromotive force) is absent.If the currents are not equal, then the difference between them and there is a leakage current.He, in turn, creates the EMF and it, in turn, through the solenoid acts on the shut-off mechanism and the RCD is turned off.

Motivation installation RCD.Dangerous for the human body electric current

On Fig.1 normal mode is I 1 = I 2. When a person touches the bare wires, there is a differential current IΔn .If we calculate the current that will flow through a person, you get, I = 230 / R h , A, where 230 V mains voltage consumer, Rch - human resistance.Although each person has this characteristic is individual, but it is considered to be about 1 ohms (1000 ohms).As a result, we get 000 230/1 = 23 mA.It should be noted that the threshold of sensitivity in humans begins with a 0.6 - 1.5 mA.With this current, a human perceptible irritation.At a current of 10 - 15 mA in human muscle spasm occurs, and the current call neotpuskayuschego.In this case, a person can not independently release the bare wire, if it took him.At the current 90 - 100 mA current fibrillyatsionnogo arises.At this current chaotic heart muscles contract, and after a few seconds going into cardiac arrest.Safe for humans is considered to be a current of 2 mA when it passes over 10 seconds, and if more than 120, the safe current of 6 mA.These currents, as well as time off is necessary to keep in mind when selecting an RCD residual current that would understand what will happen to you if you fall under dangerous voltage.For these reasons, remember, if the RCD turns off the heater, it saves you a minimum of discomfort.

Selection of RCD depending on leakage currents

According SP31-110-2003 p.A.4.15 bathroom if powered by a separate line, it is necessary to provide RCD 10 mA, if the line is a common room with kitchen andcorridor, it is necessary to install the RCD current up to 30 mA.For ordinary household power lines (sockets, lighting) protection device is selected at a maximum current of 30 mA ( PUE p.7.1.79.). RCD to differential currents at 100 and 500 mA, as shown above, do not protect the human body from dangerous voltage, and it is the main purpose of fire protection.When installing the machine breakers need to understand that it does not protect against long-term overload, the maximum current or overvoltage.For these reasons, this installation must be in conjunction with a circuit breaker with electromagnetic and thermal release device and overvoltage protection must be installed relays or surge arresters (device protection against surge voltages).For these reasons, if the RCD TERMEKS off, and the machine does not work, then, is the cause of the fault leakage current.

If UZOodnovremenno off with the circuit breaker, the cause may be a differential current and maximum currents that occur when a short-circuit.

Causes of leaks

current important to understand that the presence of the leakage current, it is an emergency operation or a fault in the electrical networks domestic purposes or malfunctions in electrical appliances.The causes of this current is quite common.The main causes of leakage current is a human touch to the bare wires, through the course of his deformed or insulation of the cable through the conductive element.For example, the reason for tripping RCDs vodonagrevateleeto can be leakage current through the water.The cable insulation damaged by moisture penetrated the bare wire and the current through it went.This current is just not enough for what would be the difference of incoming and outgoing currents is equal to 0 (zero) disables the alarm and protection of land.If this water heater TERMEKS, disconnected RCD dannogopribora.Voda may also be the reason why the RCD is turned off on nasoseperekachivayuschim various liquids.

Types and RCD.Visual and technical designation

Fig.2 Appearance and designation of protective devices

RCD divided on:

• household voltage and mains 220/380
• According to the number of poles.If a single-phase load in the power system, the RCD must be installed two-pole if the three-phase load, the four poles.
• at nominal operating current.The value of the nominal (operating) currents for the RCD is the same as for the circuit breakers, it is 16, 25, 32, 40, 63, 80 A
• residual current (leakage current), the value of which is oriented residual current device 10, 30, 100, 300, 500 mA
• by type of leakage current, which in turn is divided into:

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1. Alternating pulsating electric current.RCD type for the current « Speaker". pulsing current is present in the controlled luminaires and lamps, washing machines in which regulated speed.
2. 2. AC and DC electrical pulse, the type of RCD « A".This tipustroystv zaschityrekomenduetsya apply where there is consumer electronics, microwave, computer, TV, etc.
3. permanent electrical and AC type RCDs «B». This type of protection devices primarily installed where there is a rectified current.The household electrical networks, this type is not used.
4. In order to observed selectivity in the installation of 2 or more protective devices in the household and electrical power networks used RCD with delayed tripping, this type of RCD «S». This type of RCD is used in networks where ATS use (automatic transfer switch), and the type of « G », in the same network, but it has less exposure time.

tripping RCDs, primary and secondary causes of

most common causes tripping RCDs in the boiler or water heater Electrolux, is unscrupulous manufacturer or various types of faults in the electrical network.If the water heater is turned off ouzo on , it is necessary to once again enable it.If the appliance is working and the RCD does not disconnect, then, it was a short-term leakage current.Next, you need to use the button "Test".It simulates the emergency mode.

1. must disable machines that are included in the network in conjunction with the RCD and to determine, why disconnected RCD .At the same time we disconnect the neutral conductor.After they disconnected, turn on the RCD.If it is not turned off, then press the "Test" button.If after clicking "Test" RCD worked, then it is fine.It should be noted that the verification of protective device performance should be checked at least 1 time per month by pressing the "Test" button.
2. If during connection RCD operates without load, means it is out of order, or at the point of installation there are leakage currents.If it is fine, it is necessary to understand why the RCD operates without load.In this case, if you have multiple machines from him, then all at once they are disabled.Then we determine why the RCD turns off and turns include circuit breakers and determine the emergency section of electrical network.

main types of connection RCD

Fig.3. One RCD and one consumer

Connect the RCD can any electrician, having at least the 3rd bit fitter.Wiring is written on the device, and there is nothing difficult.The only thing that should be done prior to installation, it is to take into account the nuances of when you turn on the network and select the right amount of off machines per RCD.You can install a single security device to the entire apartment floor panel, if it's an apartment building, as shown in Figure 3 . can be set separately in the rosette and lighting network, if enough space for installation.It would be suitable for an apartment.When installing and selecting RCD must take into account the nominal (operating) current, which should be one level higher than the rated current of the machine, which is after the protective device.For example, if the machine 25 A, it is necessary to set the operating current with the RCD 32 A etc.If it is a private home, it is best to consider the following items, one RCD and one automatic if the machine is not a lot.

One security appliance and a few breakers

Fig.4

If, for example, the house is a lot of machines (one machine = one room, or = one appliance), in this case the size of the electrical panel can be huge.For these reasons, better skomplektovat switchboard so under one RCD to install multiple machines, but no more than 5. In this case, it is necessary to calculate the rated current of the protective device in relation to the off-machines so that their sum does not exceed the operating current protective devices.For example, off-BA1 machines 16 A, 16 A BA2, BA3 32 A sum of 16 + 16 + 32 = A. So the RCD should be rated current of at least 64 A, and knowing the range of the rated currents of the best option on the residual current device ratedcurrent to 63 A.

As seen in Fig.4 nothing complicated to connect not, but in some cases, it will be interesting to know why the RCD operates on the water heater ariston if home network and device protection are in a satisfactory operational and sostoyanii.Kogda triggered RCD, the reasons may not be properly connected.

The main types of wrong connection of the RCD, the neutral and protective conductor

• not connect the neutral ( N ) and phase conductor passing through the RCD with other zero and phase conductors after the RCD.
• You can not make the connection neutral conductor (N) after RCD open designs electrical systems, as well as it can not be connected with the protective conductor (PE).
• Never connect the neutral in the AC outlet and the protective conductor.
• If the mains two protective devices, the association of neutral conductor installed will result in additional current leakage and as a consequence of activation of both
• If the electrical panel installed many RCD, you should double-check the wiring to avoid connecting the phase conductor andworking the ground with various protection devices

Only properly selected protective devices and connected properly protect the person in case of an accident on the dangerous effects of electric current.

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