Protective shutdown of electrical installations. Scope, basic requirements for RCDs, their types. What is the protective shutdown used for?

Windows Defender is a built-in component of the operating system that helps protect your computer from malware such as viruses, spyware, and other potentially unsafe applications.

In fact, Windows Defender is the same antivirus, only free, if you do not take into account the cost of the operating system itself. So why turn it off if it performs such useful functions, you don't have to pay extra for it and install it separately?

The fact is that Windows Defender only performs basic protection computer. Third-party antiviruses do a much better job of protecting your PC. You can see for yourself by looking at where the Defender is located according to the research data of the AV-Test laboratory (clickable image).

On the other hand, if you are a "diligent" user of the computer and the Internet, do not go to suspicious sites, do not download or use pirated software, use only trusted media, then Windows 10 Defender will be enough for you to ensure minimal security.

But back to the main topic of the article. How do you disable Windows 10 Defender anyway?

First of all, it should be noted that the Defender itself automatically turns off when installing additional antivirus software, provided that the system correctly recognizes third-party software.

Next, consider an option that I deliberately did not include in the general list of ways to deactivate Defender. The fact is that it only has a temporary effect. After a while or after restarting the computer, the defender will return to working state. This is a feature of Windows 10. In Windows 8.1, this method could completely disable the built-in antivirus.

Open your computer settings ( Windows + I).
Go to the section " Updates and security».
Select " Windows Defender»In the menu on the left.
Disable the " Real-time protection»

Now let's take a look at ways that disable Defender completely.

Disable Windows 10 Defender permanently

Method 1 - Through the registry

1. Open the " Execute» ( Windows + R), enter the command regedit and press " OK».

2. Navigate to the following registry branch:

HKEY_LOCAL_MACHINE \ SOFTWARE \ Policies \ Microsoft \ Windows Defender

3. Click with the right mouse button on an empty space on the left and create a DWORD (32-bit) parameter with a name.

4. Double-click to open the newly created parameter, assign a value to it 1 and press " OK».

Now you can close the registry editor and check the operation of this method through the computer settings. There you can make sure that all settings related to Defender have become inactive. You can also try running the built-in antivirus by clicking the link at the very bottom “ Open Windows Defender».

As a result, you will receive a message that Windows 10 Defender has been disabled by Group Policy.

If you want to reactivate the disabled Windows 10 Defender, you just need to remove the DisableAntiSpyware parameter or change its value to 0.

Method 2 - Using the Local Group Policy Editor

1. Run the command gpedit.msc through the window " Execute» ( Windows + R).

2. Proceed to the next section:

Computer Configuration -> Administrative Templates -> Windows Components -> Endpoint Protection

In some versions (assemblies) of Windows 10, this section may be called Windows Defender or Windows Defender.

3. In this section on the left, find the item "" and open it.

4. Activate this option as shown in the image below and click " OK».

Close the Group Policy Editor and you can, as in the first method, check if Defender is disabled.

If you want to turn Windows Defender back on, follow all the steps above and set the parameter to “ Not set". However, a reboot may be required to activate the built-in antivirus.

Method 3 - NoDefender Program

If the above methods did not help, you can try utilities specially designed to disable Windows Defender. One of these is NoDefender.

Attention! Use this method only as a last resort. Programs of this kind are not officially supported by Windows developers, and therefore no one gives any guarantees that they will not affect the performance of the operating system.

Be sure to back up your system before using NoDefender. It is also worth noting that the process of disabling the defender using this utility is irreversible. At least, the functionality of the program does not allow you to turn the Defender back on.

2. Unpack the resulting archive and run the program.

3. In the first window of the program, click " Next».

5. Disable the following options: real-time protection, cloud protection and automatic sample submission.

7. Then press " Next"And at the last step" Exit».

Everything. Windows Defender is disabled. Now if you try to activate the Defender, the message “ The application is disabled and does not monitor the computer».

The developers of the application claim that running NoDefender again allows the defender to be activated again. I couldn't do it.

The protective shutdown is designed for quick and automatic shutdown of a damaged electrical installation in cases of a phase short circuit to the case, a decrease in the insulation resistance of conductors, or when a person is short-circuited to conductive elements.

The scope of the residual current device (RCD) is practically unlimited: they can be used in networks of any voltage and with any neutral mode. RCDs are most widespread in networks with voltages up to 1000 V in installations with a high degree of danger, where the use of protective grounding or grounding is difficult for technical or other reasons, for example, at test or laboratory stands.

The advantages of RCDs include: simplicity of the circuit, high reliability, high speed (response time t = 0.02¸0.05 s), high sensitivity and selectivity.

According to the principle of operation, RCDs differ as follows:

Direct action:

1. RCD, responsive to housing voltage U To;

2. RCD, responsive to case current I To.

Indirect action:

3. RCD responding to phase voltage asymmetry - zero sequence voltage U O;

4. RCD, reacting to asymmetry of phase currents - zero sequence current I O;

5. RCD, responsive to operating current I op.

Consider the listed types of residual current devices.

1. RCD, which reacts to the voltage of the case.

The operation of the RCD circuit shown in Fig. 7.29 is carried out as follows.

The start-up of the power plant is carried out by pressing the "START" button with normally open contacts. In this case, the tripping coil is OK, having received power from the phase conductors 2 and 3 , compressing the spring P and pulling in the rod, closes all four contacts of the magnetic starter MP. The "START" button is released, and further power supply of the OK when the power plant is operating is carried out through the self-feeding line of the LAN through the MK contact. When a phase conductor is closed, such as a conductor 2 , to the ES body through the LV voltage relay installed on the additional grounding line ( r g), current will flow. In this case, the normally closed contacts of the voltage relay PH will open, the OK coils will be de-energized and with the help of a mechanical spring P, the contacts of the magnetic starter MP will open and the damaged installation will be disconnected from the network. The danger of electric shock to the operating personnel is eliminated. To check the operability of the RCD circuit, a self-control operation is performed at idle operation of the electrical installation. When you press the KS button connected to the phase conductor 1 and a protective earth line through a resistance R with, the power unit body will be energized. If the RCD is in good condition and there are no defects in the RCD circuit, the entire installation will shutdown, as described above. Using the self-feeding line of the LS with an additional mechanical contact MK, the RCD circuit shown in Fig. 7.29, allows for zero protection - protection against self-starting of the electrical installation

with a sudden disappearance and sudden supply of voltage.

Rice. 7.28. Schematic diagram of a residual current device,
responding to the potential of the case:

MP - magnetic starter; OK - tripping coil with spring P; RN - voltage relay with normally closed RN contacts; r 3 - resistance of the main protective grounding; r g- resistance of additional grounding; LS - self-replenishment line; MK - additional mechanical contact; P - START button; С - STOP button; KS - SELF-CONTROL button; R c- resistance to self-control; a 1, a 2 - coefficients of contact of the main and additional grounding

The selection of the operating voltage of the RCD, which responds to the voltage of the case, is made according to the formula:

(7.25)

where U pr add - permissible touch voltage, taken equal to 36 V with a duration of current exposure to a person 3¸10 s. (table 7.2); R p, X L- active and inductive resistance of the LV; a 1, a 2 - the contact coefficients of the corresponding grounding conductors; r g- resistance of additional grounding.

Calculation by formula (7.25) is reduced to determining the value r g in this case, the operating voltage of the RCD circuit must be less than the touch voltage, i.e. U Wed< U NS.

2. RCD, which reacts to the case current.

The principle of operation of the circuit of the residual current device, which reacts to the current of the case, is similar to the action of the RCD circuit, which is triggered by the voltage of the case, described above. This circuit does not require additional grounding. Instead of the voltage relay RN, a current relay RT is installed on the line of the main protective ground. Other devices and circuit elements remain unchanged, as in Fig. 7.20. Selection of the operating current I cf RCD, responsive to the current of the power plant case, is made according to the formula:

I cf = (7.26)

where Z rt is the total resistance of the current relay, r 3 - resistance of protective grounding; U- permissible contact voltage (7.25).

3. RCD, reacting to phase voltage asymmetry.

Rice. 7.30. Schematic diagram of a residual current device,
reacting to phase voltage unbalance:

a- common point zero sequence filter 1 ; RN - voltage relay;
Z 1 , Z 2 , Z 3 - impedances of phase conductors 1, 2 and 3; r zm1, r zm2 - resistance
short circuit of phase conductors 1 and 2 to ground; U o = φ 1 - φ 2  is the zero sequence voltage (φ 1 is the potential at the point 1 , φ 2  is the potential at the point 2 )

The sensor in this RCD circuit is a zero sequence filter consisting of capacitors connected in a star.

Consider the operation of the RCD circuit shown in Fig. 7.30.

If the resistances of the phase conductors relative to the ground are equal to each other, i.e. Z 1 = Z 2 = Z 3 = Z, then the zero sequence voltage is zero, U o = φ 1 - φ 2  = 0. In this case, this RCD circuit does not work.

If there is a symmetrical decrease in the resistance of the phase conductors by the amount n> 1, i.e. then voltage U o will also be equal to zero and the RCD will not work.

If an asymmetrical degradation of the insulation of the phase conductors occurs Z 1 ¹ Z 2 ¹ Z 3, then in this case the zero sequence voltage will exceed the operating voltage of the circuit and the residual current device will disconnect the network, U o> U Wed

If there is a short to ground of one phase conductor, then at a low resistance value, the short circuit r zm1 zero sequence voltage will be close to the phase voltage, U f> U Wed, which will trigger the protective shutdown.

If there is a ground fault of two conductors at the same time, then at small values r zm1 and r Zm2 the zero sequence voltage will be close to the value, which will also lead to a network shutdown. Thus, to the advantages of a voltage-responsive RCD circuit U oh, include:

Reliability of operation of the circuit in case of asymmetric deterioration of the insulation of phase conductors;

Reliability of operation in case of one- or two-phase short circuit of conductors to earth.

The disadvantages of this RCD circuit are absolute insensitivity with a symmetrical deterioration of the insulation resistance of the phase conductors and the lack of self-control in the circuit, which reduces the safety of maintenance of electrical systems and installations.

4. RCD responding to phase current unbalance

a) b)

Rice. 7.31. Schematic diagram of a residual current device,
reacting to unbalance of phase currents:

a- circuit of the zero sequence current transformer TTNP; b - I 1 , I 2 , I 3 - currents of phase conductors 1 , 2 , 3 ; RT - current relay; OK - tripping coil; 4 - magnetic circuit TTNP;
5 - secondary winding of TTNP

The sensor in the RCD circuit of this type is the zero sequence current transformer TTNP, schematically shown in Fig. 7.31, b... The secondary winding of the TTNP gives a signal to the current relay RT and at a zero sequence current I 0, equal to or greater than the current of the installation, the electrical installation will shutdown.

Consider the action of the RCD shown in Fig. 7.31.

If the insulation resistances of the phase conductors are equal Z 1 = Z 2 = Z 3 = Z and symmetrical load on the phases I 1 = I 2 = I 3 = I zero sequence current I 0 will be equal to zero, and therefore, the magnetic flux in the magnetic circuit 4 (fig. 7.31, a) and EMF in the secondary winding 5 TTNP will also be equal to zero. The protection circuit is inoperative.

With a symmetrical deterioration of the insulation of the phase conductors and a symmetrical change in the phase currents, this RCD circuit also does not react, since the current I 0 = 0 and there is no EMF in the secondary winding.

With an asymmetric deterioration of the insulation of phase conductors or when they are short to ground or to the EU frame, a zero sequence current will occur I 0> 0 and a current equal to or greater than the operating current is generated in the secondary winding of the TTNP. As a result, the damaged area or installation will be disconnected from the network, which is the main advantage of this RCD circuit. The disadvantages of the circuit include design complexity, insensitivity to symmetrical insulation degradation, and lack of self-control in the circuit.

5. RCD, responsive to operating current.

The sensor in this RCD circuit is a current relay with low actuation currents (several milliamperes).

Rice. 7.32. Schematic diagram of a residual current device,
responsive to operational current:

D 1, D 2, D 3 - three-phase choke with a common point 1 ; D p - single-phase choke; I op - operational current from an external source; RT - current relay; Z 1 , Z 2 , Z 3 - impedances of phase conductors 1 , 2 and 3 ; r zm - the resistance of the phase conductor closure;
- the path of the operating current

A constant operating current is supplied to the protection circuit I op from an external source that passes through a closed circuit: source - ground - insulation resistance of conductors Z 1 , Z 2 and Z 3 - the conductors themselves - three-phase and single-phase chokes - the winding of the current relay RT.

In normal operation, the insulation resistances of the conductors are high, and therefore the operating current is insignificant and less than the operating current, I op< I Wed

In the event of any decrease in the resistance (symmetrical or unbalanced) of the insulation of the phase conductors or as a result of a person touching them, the total resistance of the circuit Z will decrease, and the operating current I op will increase and if it exceeds the operating current I Wed, the mains will be disconnected from the power source.

The advantage of an RCD that reacts to the operating current is to ensure a high degree of safety for people in all operating modes of the network due to current limitation and the possibility of self-monitoring of the circuit's serviceability.

The disadvantage of these devices is the complexity of the design, since a constant current source is required.

Safety shutdown- this is a fast-acting protection that provides automatic shutdown of an electrical installation when there is a danger of electric shock to a person.

protective shutdown is currently the most effective electrical protective means. The experience of developed foreign countries shows that the massive use of residual current devices (RCDs) has provided a sharp decrease in electrical injuries.

Protective shutdown is increasingly being used in our country. It is recommended for use as one of the means to ensure electrical safety by regulatory documents (NTD): GOST 12.1.019-79, GOST R 50571.3-94 PUE, etc. In some cases, mandatory use of RCDs in electrical installations of buildings is required (see GOST R 5066.9 -94). The objects to be equipped with the AEO include: newly built, reconstructed, overhauled residential buildings, public buildings, industrial structures, regardless of the form of ownership and belonging. It is not allowed to use an RCD in cases where a sudden shutdown can lead, for technological reasons, to the occurrence of situations dangerous for personnel, to the shutdown of fire, burglar alarms, etc.

The main elements of the RCD are a residual current device and an actuator - a circuit breaker. Residual current device is a set of individual elements that perceive the input signal, react to its change and, at a given signal value, act on the switch. Executive device- an automatic circuit breaker, which ensures the shutdown of the corresponding section of the electrical installation (electrical network) upon receipt of a signal from the residual current device.

Primary requirements, for RCDs:

1) Response speed - the shutdown time (), summed up of the time of the device (t p) and the time of the switch (t in), must meet the condition

The existing designs of devices and apparatus used in protective shutdown circuits provide a shutdown time t o tcl = 0.05 - 0.2 s.

2) High sensitivity - the ability to respond to small values of input signals. Highly sensitive RCD devices allow setting the switches (the values of the input signals at which the switches are triggered), ensuring the safety of a person's contact with the phase.

3) Selectivity - the selectivity of the action of the RCD, i.e. the ability to disconnect from the network that section in which there was a danger of electric shock to a person.

4) Self-control - the ability to react to own faults by disconnecting the protected object is a desirable property for an RCD.

5) Reliability - no failures in work, as well as false positives. Reliability must be sufficiently high, since RCD failures can create situations associated with electric shock to personnel.

Application area RCDs are practically unlimited: they can be used in networks of any voltage and with any neutral mode. RCDs are most widespread in networks up to 1000 V, where they ensure safety when a phase is closed to the case, a decrease in the insulation resistance of the network relative to the ground below a certain limit, a person's touch to a live part that is energized, in mobile electrical installations, in an electric tool, etc. Moreover, RCDs can be used as independent protective devices, and as an additional measure to grounding or protective grounding. These properties are determined by the type of RCD used and the parameters of the protected electrical installation.

Types of residual current devices. The operation of the electrical network in both normal and emergency modes is accompanied by the presence of certain parameters that can vary depending on the conditions and operating mode. The degree of danger of injury to a person in a certain way depends on these parameters. Therefore, they can be used as input signals for RCDs.

In practice, the following input signals are used to create an RCD:

Hull potential relative to ground;

Earth fault current;

Zero sequence voltage;

Differential current (zero sequence current);

Phase voltage to ground;

Operational current.

In addition, combined devices are used that respond to several input signals.

Below is a diagram and operation of a residual current device that reacts on the potential of the case relative to the ground.

The purpose of an RCD of this type is to eliminate the danger of electric shock to people when an increased potential occurs on a grounded or grounded housing. Typically, these devices are an additional measure of protection to grounding or earthing. The device is triggered if the potential φ k arising on the body of the damaged equipment turns out to be higher than the potential φ cdop, which is selected based on the highest long-term permissible touch voltage U pr. Add.

The sensor in this circuit is the RN voltage relay,

Fig. 28. Schematic diagram of an RCD that reacts to

potential of the case, connected to earth by means of an auxiliary earthing switch R vop

When a phase is closed to a grounded (or neutralized) case, a protective grounding first acts, providing a decrease in the voltage on the case to the value U k = I z * R z,

where R s is the protective grounding resistance.

If this voltage exceeds the voltage of the setting of the relay PH U set, then the relay, due to the current I p, will operate, opening the power circuit of the magnetic starter MP with its contacts. And the power contacts of the magnetic starter, in turn, will de-energize the damaged equipment, i.e. The RCD will complete its task.

Operational (working) switching on and off the equipment is carried out by buttons START, STOP. The contacts of the magnetic starter BK provide its power after releasing the START button.

The advantage of this type of RCD is the simplicity of its circuit. The disadvantages include the need for auxiliary grounding, lack of self-monitoring of serviceability, non-selectivity of disconnection in the case of connecting several buildings to one protective earthing switch, inconsistency of the setting when R vop.

Next, consider the second circuit that responds to a differential current (or zero-sequence current) - RCD (D). These devices are the most versatile, and therefore are widely used in manufacturing, public buildings, residential buildings, etc.

Safety shutdown

Zeroing

Zeroing- deliberate electrical connection to the neutral protective conductor of metal non-current-carrying parts that may be energized. Zero protective conductor - a conductor connecting the neutralized parts with the neutral point of the current source winding or its equivalent.

Zeroing is used in networks with voltages up to 1000 V with a grounded neutral. In the event of a phase breakdown to the metal body of the electrical equipment, a single-phase short circuit occurs, which leads to a quick operation of the protection and thereby automatic disconnection of the damaged installation from the supply network. Such protection are: fuses or overload circuit breakers installed to protect against short-circuit currents; automatic machines with combined releases.

When a phase is closed to a zeroed case, the electrical installation is automatically turned off if the single-phase short-circuit current I З satisfies the condition I З> = To∙ I N, where I N is the rated current of the fuse insert or the operating current of the circuit breaker, A; To- current multiplicity factor.

For machines To= 1.25 - 1.4. For fuses To = 3.

The conductivity of the neutral protective conductor must be at least 50% of the conductivity of the phase conductor.

The calculation of grounding for the safety of touching the frame in case of a phase to ground or frame is reduced to calculating the grounding of the neutral point of the transformer and repeated grounding conductors of the neutral protective conductor. According to the PUE, the neutral grounding resistance should be no more than 8 ohms at 220/127 V; 4 Ohm at 380/220 V; 2 ohms at 660/380 V.

Safety shutdown is a protection system that automatically shuts down an electrical installation when there is a danger of electric shock to a person (in case of a ground fault, a decrease in insulation resistance, a ground fault or grounding). A protective shutdown is used when it is difficult to perform grounding or neutralization, and also in addition to it in some cases.

Taking into account the dependence on what is the input value, to the change of which the protective shutdown reacts, the protective shutdown circuits are distinguished: on the case voltage relative to the ground; for earth fault current; for voltage or current of zero sequence; for phase voltage relative to earth; for direct and alternating operating currents; combined.

The principle of operation of the RCD as a protective switch that reacts to the leakage current.

Rice. 14. Wiring diagram with RCD

Devices reacting to zero sequence voltage are used in three-wire networks with voltage up to 1000 V with insulated neutral and short length. Residual current devices that react to the fault current are used for installations whose housings are isolated from earth (handheld power tools, mobile installations, etc.).

The device, which reacts to zero sequence current, is used in networks with grounded and isolated neutral.

Protective shutdown - concept and types. Classification and features of the category "Safety shutdown" 2017, 2018.

- SECURITY SHUTDOWN

Protective shutdown is a fast-acting protection that provides automatic shutdown of an electrical installation in the event of a risk of electric shock, which may occur when: the halyard is closed to the body of the electrical equipment: the resistance is reduced ....

- Protective shutdown

A protective shutdown is a protection system that automatically shuts down an electrical installation in the event of a risk of electric shock to a person (in case of a ground fault, a decrease in insulation resistance, a ground fault or grounding). Protective ....

- Protective shutdown

Protective grounding Protective grounding refers to the intentional connection to earth or its equivalent of non-conductive metal parts that may be energized. Grounding of electrical installation parts and enclosures ....

- Protective shutdown

Protective shutdown is a fast-acting protection providing automatic shutdown of an electrical installation in the event of a risk of electric shock, which may arise: - when a phase is shorted to the electrical equipment case; - when decreasing ....

- SECURITY SHUTDOWN

SECTION 6.12 Protective shutdown (SA) - a protection system that automatically shuts down an electrical installation in the event of a risk of electric shock to a person (in case of a ground fault, decrease in insulation resistance, grounding faults). SA are applied ....

- Protective shutdown

Protective shutdown is a protection system that provides automatic shutdown of an electrical installation when there is a danger of electric shock. The protective shutdown circuit is shown in Fig. 2.13.3. This circuit provides protection against dead faults on ... [read more].

- Protective shutdown: purpose, scope, nature of protection, requirements.

A protective shutdown is a fast-acting protection that provides automatic shutdown of an electrical installation when there is a danger of electric shock. Such a danger can arise in the event of a violation of the insulation of live parts and a breakdown on ....

Safety shutdown is especially important when a large number of different electrical appliances are used in the house. In this article, we will look at residual current devices that are recommended and used in the construction of private houses. A diagram of the residual current device will be shown. Let us examine the question of what and when to use - an RCD or a difavtomat (differential automatic machine). In addition, we will find out the main differences between residual current circuit breakers.

Types of residual current circuit breakers

An important step in the organization of electrical safety is electrical protective devices or, as they are often called, automatic machines. Conventionally, they can be divided into three types:

automatic switches (AB);
differential shutdown devices (RCD);
differential automatic switches (DAV).

Fig 1. Circuit breaker

Fig 2. Residual current device (RCD)

Fig 3. Differential circuit breaker (DAV)

The principle of operation of residual current devices

Circuit breakers (AB), see Fig. 1, we install to protect the wiring from overcurrent, and electrical consumers from short circuits. Overcurrent overloads lead to heating of the conductor, which leads to a fire in the wiring and its failure.

Residual current device (RCD) operating principle(fig. 2). We install for protection against electric shock, in case of breakdown of the insulation of equipment and wiring. The RCD will also protect us in the event of touching open uninsulated sections of wiring or equipment that are energized at 220 V and will not allow a fire to occur if the wiring is faulty.

If there is a difference in currents, then the RCD turns off the voltage supply. It is necessary to choose an RCD according to two parameters: sensitivity and rated current. Typically, for household purposes, an RCD with a sensitivity of 300 mA is chosen. The rated current is selected depending on the total power of the electrical consumers and must be equal or an order of magnitude lower than the rated current of the input circuit breaker (AB), because the RCD does not protect against short circuit and overcurrent. A residual current device (RCD) is usually installed in the circuit after the meter to protect all wiring in the house, see fig. 4, 5. According to modern standards, the installation of an RCD is mandatory.

Rice. 4. RCD connection diagram

Rice. 5 Wiring diagram of power supply at home using an RCD

1 - u it is distributing; 2 - neutral; 3 - w ina grounding; 4 - f aza; 5 - RCD; 6 - av tomato switch; 7 - nnutrition of consumers.

Differential circuit breakers (DAV) combine the functions of RCD and AB. The circuit of the differential machine is based on the protection of circuits against short circuits and overloads, as well as the protection of people from electric shock when touching live parts, see Fig. 6.

Rice. 6. Diagram of DAW operation

These devices are widely used in household electrical networks (220/380 V), in outlet networks. The differential circuit breaker consists of a high-speed circuit breaker and a residual current device that reacts to the difference in currents in the forward and reverse directions.

The principle of operation of the differential machine. If the insulation of the electrical wiring is not damaged and there is no human touch to live parts, then there is no leakage current in the network. This means that the currents in the forward and reverse (phase-zero) load conductors are equal. These currents induce equal but oppositely directed magnetic fluxes in the magnetic core of the DAV current transformer. As a result, the current in the secondary winding is zero and does not trigger the sensitive element - the magnetoelectric latch.

When a leak occurs, for example: when a person touches a phase conductor, the balance of currents and magnetic fluxes is disturbed, an unbalance current appears in the secondary winding, which triggers a magnetoelectric latch, which in turn acts on the release mechanism of an automatic machine with a contact system.

A testing circuit is provided for periodic monitoring of the RCD and DAV performance. By pressing the "Test" button, a tripping differential current is artificially generated. The actuation of the protection devices means that it is generally serviceable.

Choice of circuit breaker

Now, let's decide in which case and which protective machine we give preference to:

To protect the wiring of the lighting network, from which all our lamps are powered, we choose automatic switches (AB) with operating currents 16 A.
The electrical outlet in the home, which is used to turn on irons, table lamps, televisions, computers, etc., must be protected by differential protection circuit breakers (DAV).
For the outlet network, we choose DAV with an operating current of 25 A and differential current shutdown 30 mA.
To connect an air conditioner, a dishwasher, an electric oven, a microwave oven and other powerful devices that are so necessary for us in everyday life, we need our own individual outlet and, therefore, our own circuit breaker with differential protection. For example, to connect an electric furnace with a power of 6 kW, a differential circuit breaker with breaking currents of 32 and 30 mA is required.

Paying attention, that all sockets must be grounded. Power equipment, such as a grinding machine, I advise you to connect it to a circuit breaker. Since the entire network in our house is for a voltage of 220 V, we also select the listed circuit breakers for the corresponding voltage.

Let's talk about a circuit breaker, which, for safety reasons, needs to be installed at the input. If we protected all socket lines with circuit breakers with differential protection, then at the input we put an automatic circuit breaker (AB) with a rated current determined by technical conditions and a single-line diagram of the project "Electrical equipment of a residential building".

But it is possible, after the introductory circuit breaker (AB), to put a residual current device (RCD) with a differential protection current of 300 mA. For such a connection diagram, see Fig. 5. If we choose this option of protection, then it does not oblige us to install differential circuit breakers for the outlet network, but simply install a circuit breaker (AB), see the same fig. 5. Such a scheme is acceptable if we have only one outlet line with a number of outlets. But it is completely not rational if we have a number of independent receivers plugged into individual sockets.

For example: You have a current leakage to the body of the washing machine and accidentally touch it. The differential protection will instantly work and the washing machine's DAI will turn off. It will not be difficult for you to identify and eliminate the cause. Imagine how much work needs to be done to find the reason for the disconnection of the RCD at the input.

I want to say that in the modern market for circuit breakers and RCDs there is a very large selection of devices, both domestic and foreign. It should be borne in mind that domestic products are distinguished by their large overall dimensions, the possibility of current regulation, a lower price, and the service life in domestic conditions is practically the same.

Table 1. Comparison of the cost of circuit breakers

Conclusion

So, in the article, we examined the issues of electrical safety. They became especially relevant when a huge number of electrical appliances, consumer electronics and computers entered our house. The wiring carries a very high load and a safety shutdown is necessary. Modern technology is very expensive and demanding on the quality of networks. Therefore, you should not save on protective measures, because the cost of an RCD is not commensurate with the cost of equipment in your home, and even more so with the cost of human life.

Attention: Prices are valid for 2009.