6. Neutral mode.

Operating modes of neutrals in electrical installations

Neutrals of electrical installations are called common points three-phase windings generators or transformers connected in a star.

Depending on the neutral mode, electrical networks are divided into four groups:

1) networks with ungrounded (isolated) neutrals;
2) networks with resonantly grounded (compensated) neutrals;
3) networks with effectively grounded neutrals;
4) networks with solidly grounded neutrals.

According to the requirements of the Electrical Installation Rules (PUE, Chapter 1.2).

Networks with a rated voltage of up to 1 kV, powered by step-down transformers connected to networks with Un > 1 kV, are carried out with solid neutral grounding.
Networks with Unom up to 1 kV, powered from an autonomous source or an isolation transformer (subject to the condition of ensuring maximum electrical safety in case of ground faults), are carried out with no grounded neutral.
Networks with Un = 110 kV and higher are carried out with effective neutral grounding (the neutral is grounded directly or through a small resistance).
Networks 3 - 35 kV, made by cables, with any ground fault currents, are carried out with grounding of the neutral through a resistor.
3-35 kV networks with air lines, with a fault current of no more than 30 A, they are performed with the neutral grounded through a resistor.

Compensation of capacitive current to ground is necessary for the values ​​of this current under normal conditions:

In networks 3 - 20 kV with reinforced concrete and metal supports of overhead lines and in all networks 35 kV - more than 10 A;

In networks that do not have reinforced concrete or metal supports VL:
at voltage 3 - 6 kV - more than 30 A;
at 10 kV - more than 20 A;
at 15 - 20 kV - more than 15 A;

In circuits of 6 - 20 kV blocks, the generator - transformer - more than 5A.

Electrical installations voltage above 1 kV according to the Electrical Installation Rules (PUE) are divided into installations with high ground fault currents (single-phase ground fault current exceeds 500 A) and installations with low ground fault currents (single-phase ground fault current less than or equal to 500 A).

In installations with high ground fault currents neutral connected to grounding devices directly or through low resistance. Such installations are called installations with solidly grounded neutral .

In installations with low ground fault currents, the neutrals are connected to grounding devices through elements with high resistances. Such installations are called installations with isolated neutral.

In installations with solidly grounded neutral Any ground fault is a short circuit and is accompanied by a large current.
In installations with an isolated neutral, a short circuit of one of the phases to ground is not a short circuit (short circuit).

The passage of current through the fault is due to the conductivity (mainly capacitive) of the phases relative to the ground.
The choice of the neutral mode in installations with voltages above 1 kV is made taking into account the following factors: economic, the possibility of transition of a single-phase fault to a phase-to-phase fault, the impact on the breaking capacity of switches, the possibility of damage to equipment by ground fault current, relay protection, etc.

The following neutral operating modes are adopted in the electrical networks of RAO UES of Russia:

• electrical networks with rated voltages of 6...35 kV operate with low currents
• ground fault;
• for small capacitive ground fault currents - with insulated neutrals;
• at certain values ​​exceeding capacitive currents- with neutral grounded
• through an arc suppression reactor.

If in one of the phases three phase system, working with isolated neutral, a short circuit to ground has occurred, then its voltage in relation to the ground will become equal to zero, and the voltage of the remaining phases in relation to the ground will become equal to linear, i.e. it will increase 3 times. The ground fault current will be small because, due to the insulation of the neutral, there is no closed circuit for it to pass through. The ground fault current in a system with an isolated neutral will be small and will not cause an emergency shutdown of the line. Thus, insulating the neutral of the power source ensures reliable power supply, since it does not affect the operation of consumers.

However, in networks with large capacitive currents an intermittent arc appears on the ground (especially in cable networks) at the point of fault, which periodically goes out and lights up again, which leads to a circuit with active, inductive and capacitive elements emf exceeding the rated voltage by 2.5...3 times. Such voltages in the system at single-phase circuit on the ground are not allowed. To prevent the occurrence of intermittent arcs between the neutral and ground, an inductive coil with adjustable resistance is switched on.

An increase in voltage relative to ground in undamaged phases in the presence of weak points in the insulation of these phases can cause phase-to-phase short circuit,. In addition, the voltage in undamaged phases increases by 3 times, therefore, it is necessary to insulate all phases for linear voltage, which leads to an increase in the cost of machines and devices. Therefore, although operation of a network with an isolated neutral is permitted when a phase-to-ground fault occurs, it must be immediately detected and corrected.
Electrical networks with a rated voltage of 110 kV and above operate with large earth fault currents (with effectively grounded neutrals).

For autonomous mobile units the neutral is selected isolated.

According to the “Rules for Electrical Installations”, when stationary electrical receivers are powered from autonomous power sources, the neutral mode of the power source and protective measures must correspond to the neutral mode and protective measures taken in networks of stationary electrical receivers. Therefore, for diesel generators used as a “reserve” industrial network", the neutral is selected solidly grounded.

I bought a 1 phase generator. The neutral is separated from the ground. The house has a 3-phase input. On the input panel in the house, zero and ground are on the same block, that is, they are connected.
I plan to connect the generator through a reversible 4-pole switch, i.e. phase and zero in the gap. What to do with the grounding of the generator? Is it possible to throw houses on the ground?

It’s not possible, but by default the generator frame must be connected to the power supply at home with a power cable. In general, worse options are possible, budget-friendly, permitted by standards and common sense, and more best options, when the generator frame is not connected to the house charger. In any case, the generator frame must be grounded.

In addition to the fact that in 1-phase generators there is no zero, by default any power output must be groundedit is forbidden!

GOST R 50783-95 said:

ELECTRICAL UNITS AND MOBILE POWER PLANTS WITH INTERNAL COMBUSTION ENGINES
10 SAFETY REQUIREMENTS

10.3 Electrical connection diagram for mobile electrical units and AC power plants three-phase current must have an insulated neutral.It is not allowed to use any devices that create an electrical connection between phase and (or) neutral wires or neutral with housing or neutral wires or neutral with housing or ground directly or through an artificial zero point, except for devices to suppress interference to radio reception.

10.4 In mobile electrical units and power plants with a power of 1 kW and above with a rated voltage of 115 V and abovethere must be a device for continuous monitoring of insulation, which allows you to measure (evaluate) the insulation resistance relative to the body (ground) of the live parts of the electrical unit and power plant that are energized. For use in conjunction with local electrical network Mobile electrical units and power plants must have an automatic shutdown device. Monitoring of the serviceability of these devices must be provided.

It is not allowed to use continuous insulation monitoring devices operating on the principle of voltage asymmetry.

Unfortunately, only some manufacturers of autonomous power supply sources indicate this.

Generator instructions ENERGO said:

This manual is valid for petrol electric units of the company:
SAWAFUJI ELECTRIC COMPANY (Japan)

EA 6500 (SH 6500 EX)

HAZARD WARNINGS
Do not connect to the local power supply without a disconnector installed by a qualified electrician. ...

BASIC ELECTRICAL SAFETY RULES
― do not allow the electric unit to operate if there is a short circuit to the housing...

When operating the unit PROHIBITED:
ground the neutral or connect it to the housing;

Owners of autonomous power supply sources, ignorant in electrical safety, who themselves do not comply with and advise others not to comply with these standards, argue that they are right by declaring that portable and smoke-type generators and other autonomous power supply sources of 220/380 volts when powering their home from them are not affected by this, since they constantly stand in one place.

You have to think of something like this, like because the generator is called portable, it is carried during operation, or because the generator constantly stands in one place, the electricity it generates becomes safe!

Sales and installers are also ignorant in electrical safety, including some certified service centers those who connect generators, or simply hacks, tightly connect one of the generator terminals to neutral wire supply network since without switching the neutral wire simpler scheme, installation, it is cheaper and easier to find components, as well as to fool the clumsy flame control circuit of some boilers, arguing that they are doing it correctly because they have done it many times and it seems to work, which is comparable to the illiterate statement that it is enough to do the wiring without an RCCB , grounding since in millions of houses there are no RCCBs, 2 wirings and millions did not kill, so there is no need to install differential protection and use wiring with PE.

Even if the autonomous power source is stupidly connected via a power supply system with the TN grounding type, then it is impossible to somehow connect one of the power terminals of the autonomous power source to the neutral wire of the supply network!

GOST R 50571-4-44-2011 (IEC 60364-4-44:2007) said:

SAFETY REQUIREMENTS. PROTECTION AGAINST VOLTAGE SURGERY AND ELECTROMAGNETIC INTERFERENCE.

444.4.7 Switching power sources
In TN systems, switching power from one source to another sourcemust be performed using a switching device that simultaneously switches the linear conductors and the neutral conductor, if it is present in the electrical installation (see Figures 44. R9A, 44. R9B, 44. R9C).

Failure to comply with the above-mentioned electrical safety standards poses every day an increasing danger for those who violate these standards, animals, as well as for installers repairing the power supply network, since every day there are more autonomous power supply sources and their power among the population illiterate in electrical safety !

This is not to say that failure to comply with the above-mentioned standards increases the likelihood of generator failure, even to the point of impossibility of repair, for example due to a minor leak in the generator insulation, even if the generator is not working, since the machine does not protect against such a malfunction, and It is impossible to use a RCCB in such a dangerous connection!

You should also keep in mind, if you are making a circuit, that during a power outage, only part of the house wiring is powered from an autonomous power source of 220/380 volts, and the rest of the wiring remains connected to the power supply network, which is better not to do, then the installation of lines in the switchboard and in the wiring fed from an autonomous source of electricity and connected to the mains, which are located together, must be designed for 660 volts! This also applies to nearby lines powered by different autonomous power sources of 220/380 volts!

The activities were carried out in accordance with the PUE 7th ed. Chapter 1.7.

Let's consider the case when the object of installation of protective grounding is a diesel generator container (diesel generator set). In accordance with the customer’s data, the soil in the intended installation location of the IGE-4 grounding device (alluvial sandy loam gray soft plastic) and IGE-3 (alluvial-deluvial loam Brown tight-plate), groundwater at a depth of 2.5 m.

Let us take the soil resistivity to be 100 Ohm∙m.

In accordance with the PUE clause 1.7.101, the resistance of the grounding device to which the generator or transformer neutrals or source terminals are connected single-phase current, at any time of the year there should be no more than 4 Ohms, respectively, at line voltages of 380 V of a three-phase current source or 220 V of a single-phase current source.

The DGU container belongs to the conventional ones in terms of lightning protection in accordance with the CO and to the 3rd category according to the RD.

Buildings are protected from lightning strikes using lightning rods. A lightning rod is a device that rises above the protected object, through which the lightning current, bypassing the protected object, is discharged into the ground. It consists of an lightning rod that directly absorbs the lightning discharge, a down conductor and a grounding conductor.

The set of measures to ensure the necessary requirements for the lightning protection system is represented by the following solutions:

One lightning rod-mast is being installed on 3 concrete foundations 4 meters high. Installation is carried out on the roof of the container;

Construction of two down conductors using copper-plated wire D=8 mm. Down conductors should be located no closer than 3 m from entrances or in places inaccessible to people. The down conductors are fastened to the roof using clamps GL-11706. The down conductor is secured to the vertical surfaces of the building using GL-11704A clamps.

Installation of a grounding device consisting of five vertical electrodes (copper-plated pins with a diameter of 14 mm) 4.5 m long, united by a horizontal electrode (copper-plated strip 30x4 mm). The distance between vertical electrodes is at least 5 meters, the distance from the horizontal electrode to the walls of the container is 1 m, the depth is 0.5 meters.

The connection of the down conductor with the output of the copper-plated strip from the ground is carried out using a control clamp GL-11562A.

Calculation of the resistance of the grounding device:

Horizontal electrode resistance:

where ρ is soil resistivity, Ohm m;

b - strip width of the horizontal electrode, m;

h is the depth of the horizontal grid, m;

L hor - length of horizontal electrode, m.

Vertical electrode resistance:

Where ρ eq - equivalent soil resistivity, Ohm m;

L- length of vertical electrode, m;

d- diameter of the vertical electrode, m;

T- depth - distance from the surface of the earth to the ground electrode, m;

Where t- depth of the top of the electrode, m

Grounding device impedance:

Where n- number of sets;

k isp - utilization factor;

The calculated resistance of the grounding device is 3.89 ohms.

Figure 1 - Protection zone B according to the RD

Figure 2 - Layout of grounding and lightning protection elements

Scroll necessary materials shown in Table 1.

Table 1 – List of material requirements

No.	Image	Code	Name	Quantity
1.		GL-21121	GALMAR Lightning rod mast (4.0 m; on 3 concrete bases; single-stage cable support; galvanized steel)	1 PC.
2.		GL-11149-50	GALMAR Copper-plated steel wire (D8 mm; coil 50 meters)	10 pieces.
3.		GL-11706	GALMAR Flat roof holder for down conductor (D8 mm; for gluing; plastic)	4 things.
4.		GL-11707	GALMAR Decorative protective cover for holder GL-11706	4 things.
5.		GL-11704A	GALMAR Facade clamp for down conductor (painted galvanized steel)	6 pcs.
6.		GL-11562A	GALMAR Control clamp for connecting down conductors wire + strip (painted galvanized steel)	2 pcs.
7.		GL-11075-50	GALMAR Copper-plated strip (30*4 mm / S 120 mm²; coil 50 meters)	1 PC.
8.		GL-11075-10	GALMAR Copper-plated strip (30*4 mm / S 120 mm²; coil 10 meters)	1 PC.
9.		ZZ-005-064

Generally speaking, it can be noted that the great and terrible power of electricity has long been described, calculated, and entered into thick tables. Normative base, defining the paths of sinusoidal electrical signals frequencies of 50 Hz can plunge any neophyte into horror with its volume. And, despite this, any regular on technical forums has long known that there is no more scandalous issue than grounding. The mass of conflicting opinions does little to establish the truth. Moreover, this issue is actually serious and requires closer consideration.

Basic Concepts

If we omit the introduction of the “electrician’s bible” (PUE), then to understand grounding technology you need to turn (to begin with) to Chapter 1.7, which is called “Grounding and protective measures for electrical safety”.

In clause 1.7.2. said:

Electrical installations with regard to electrical safety measures are divided into:

electrical installations above 1 kV in networks with an effectively grounded neutral (with large ground fault currents), ;
electrical installations above 1 kV in networks with an isolated neutral (with low ground fault currents);
electrical installations up to 1 kV with a solidly grounded neutral;
electrical installations up to 1 kV with insulated neutral.

The vast majority of residential and office buildings in Russia use a solidly grounded neutral. Clause 1.7.4. reads:

A solidly grounded neutral is the neutral of a transformer or generator, connected to a grounding device directly or through low resistance (for example, through current transformers).

The term is not entirely clear at first glance - neutral and grounding devices are not found at every turn in the popular science press. Therefore, below all unclear places will be gradually explained.

When describing the remaining options for electrical installations, the easiest way is to proceed as in one of the versions of the instructions for a Rolls-Royce - “if the car breaks down, your driver will probably know what to do.” At least, schemes other than a solidly grounded neutral are found in the construction of home networks a little more often than Rolls-Royces on the streets.

Let's introduce a few terms - this way we can at least speak the same language. Perhaps the points will seem "taken out of context". But the PUE is not fiction, and such separate use should be completely justified - like the application of individual articles of the Criminal Code. However, the original PUE is quite accessible both in bookstores and online - you can always turn to the original source.

1.7.6. Grounding of any part of an electrical installation or other installation is called intentional electrical connection this part with a grounding device.
1.7.7. Protective grounding is the grounding of parts of an electrical installation to ensure electrical safety.
1.7.8. Working grounding is the grounding of any point of live parts of an electrical installation, which is necessary to ensure the operation of the electrical installation.
1.7.9. Grounding in electrical installations with voltage up to 1 kV is called intentional connection parts of the electrical installation that are not normally energized, with a solidly grounded neutral of a generator or transformer in three-phase current networks, with a solidly grounded output of a single-phase current source, with a solidly grounded midpoint of the source in networks direct current.
1.7.12. A grounding electrode is a conductor (electrode) or a set of metallic interconnected conductors (electrodes) that are in contact with the ground.
1.7.16. A grounding conductor is a conductor that connects the grounded parts to the ground electrode.
1.7.17. A protective conductor (PE) in electrical installations is a conductor used to protect people and animals from injury. electric shock. In electrical installations up to 1 kV, the protective conductor connected to the solidly grounded neutral of the generator or transformer is called the neutral protective conductor.
1.7.18. The neutral working conductor (N) in electrical installations up to 1 kV is the conductor used to power electrical receivers, connected to a solidly grounded neutral of a generator or transformer in three-phase current networks, to a solidly grounded terminal of a single-phase current source, to a solidly grounded source point in three-wire DC networks. A combined neutral protective and neutral working conductor (PEN) in electrical installations up to 1 kV is a conductor that combines the functions of a neutral protective and neutral working conductor. In electrical installations up to 1 kV with a solidly grounded neutral, the neutral working conductor can serve as a neutral protective conductor.

Rice. 4.5. The difference between protective grounding and protective zero

So, a simple conclusion follows directly from the terms of the PUE. The differences between “ground” and “zero” are very small... At first glance (how many copies are broken in this place). At the very least, they must be combined (or even can be done “in one bottle”). The only question is where and how it is done.

In passing, we note paragraph 1.7.33.

Grounding or grounding of electrical installations should be performed:

at voltage 380 V and above alternating current and 440 V and above direct current - in all electrical installations (see also 1.7.44 and 1.7.48);
at rated voltages above 42 V, but below 380 V AC and above 110 V, but below 440 V DC - only in hazardous areas, especially hazardous and in outdoor installations.

In other words, it is not at all necessary to ground or neutralize a device connected to a voltage of 220 volts AC. And there is nothing particularly surprising in this - there is really no third wire in ordinary Soviet sockets. We can say that the Eurostandard, which is coming into its own in practice (or the new edition of the PUE, which is close to it) is better, more reliable, and safer. But according to the old PUE, people lived in our country for decades... And what is especially important, houses were built in entire cities.

However, when it comes to grounding, it's not just about the supply voltage. A good illustration of this is VSN 59-88 (State Committee for Architecture) “Electrical equipment of residential and public buildings. Design standards" Excerpt from Chapter 15. Grounding (grounding) and protective safety measures:

15.4. For grounding (grounding) metal cases household air conditioners, stationary and portable household appliances class I (not having double or reinforced insulation), household electrical appliances power of St. 1.3 kW, housings of three-phase and single-phase electric stoves, digesters and others thermal equipment, as well as metal non-current-carrying parts technological equipment in rooms with wet processes, a separate conductor with a cross-section equal to the phase one should be used, laid from the switchboard or panel to which this electrical receiver is connected, and in lines supplying medical equipment, from the ASU or main switchboard of the building. This conductor is connected to the neutral conductor of the supply network. The use of a working neutral conductor for this purpose is prohibited.

This results in a normative paradox. One of the visible results at the everyday level was the acquisition washing machines"Vyatka-automatic" with a coil of single-core aluminum wire with the requirement to perform grounding (by the hands of a certified specialist).

And one more interesting point:. 1.7.39. In electrical installations up to 1 kV with a solidly grounded neutral or a solidly grounded output of a single-phase current source, as well as with a solidly grounded midpoint in three-wire DC networks, grounding must be performed. The use of grounding of electrical receiver housings in such electrical installations without grounding them is not allowed.

In practice, this means that if you want to “ground”, first “ground”. By the way, this is directly related to the famous issue of “battery storage” - which, for a completely incomprehensible reason, is mistakenly considered better than zeroing(grounding).

Grounding parameters

The next aspect to consider is numeric parameters grounding. Since physically it is nothing more than a conductor (or many conductors), its main characteristic will be resistance.

1.7.62. The resistance of the grounding device to which the neutrals of generators or transformers or the terminals of a single-phase current source are connected, at any time of the year should be no more than 2, 4 and 8 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 In a single-phase current source. This resistance must be provided taking into account the use natural grounding agents, as well as grounding conductors for repeated grounding of the neutral wire of overhead lines up to 1 kV with a number of outgoing lines of at least two. In this case, the resistance of the grounding conductor located in close proximity to the neutral of the generator or transformer or the output of a single-phase current source should be no more than: 15, 30 and 60 Ohms, respectively, at line voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 In a single-phase current source.

For lower voltage, higher resistance is acceptable. This is quite understandable - the first purpose of grounding is to ensure human safety in the classic case of a “phase” hitting the body of an electrical installation. The lower the resistance, the smaller part of the potential may be “on the body” in the event of an accident. Therefore, the hazard for higher voltages must be reduced first.

Additionally, it should be taken into account that grounding also serves for normal operation fuses. To do this, it is necessary that the line, during a breakdown “to the body,” significantly changes its properties (primarily resistance), otherwise the operation will not occur. The greater the power of the electrical installation (and the consumed voltage), the lower its operating resistance, and accordingly the grounding resistance should be lower (otherwise, in the event of an accident, the fuses will not trip minor change total circuit resistance).

The next standardized parameter is the cross-section of the conductors.

1.7.76. Grounding and neutral protective conductors in electrical installations up to 1 kV must have dimensions no less than those given in table. 1.7.1 (see also 1.7.96 and 1.7.104).

It is not advisable to present the entire table; an excerpt will suffice:

For non-insulated copper, the minimum cross-section is 4 square meters. mm, for aluminum - 6 sq. mm. For isolated ones, respectively, 1.5 sq. mm and 2.5 sq. mm. If the grounding conductors go in the same cable with the power wiring, their cross-section can be 1 square meter. mm for copper, and 2.5 sq. mm for aluminum.

Grounding in a residential building

In a normal “domestic” situation, power grid users (i.e. residents) deal only with the Group network (7.1.12 PUE. Group network - a network from switchboards and distribution points to lamps, plug sockets and other electrical receivers). Although in old buildings, where the panels are installed directly in the apartments, they have to deal with part of the Distribution Network (7.1.11 PUE. Distribution Network - the network from the VU, ASU, Main Switchboard to distribution points and panels). It is advisable to understand this well, because often “zero” and “ground” differ only in the place of connection with the main communications.

From this, the first grounding rule is formulated in the PUE:

7.1.36. In all buildings, group network lines are laid from group, floor and apartment panels to lamps general lighting, plug sockets and stationary electrical receivers must be three-wire (phase - L, neutral working - N and neutral protective - PE conductors). Combining zero working and zero protective conductors of different group lines is not allowed. The neutral working and neutral protective conductors are not allowed to be connected on panels under a common contact terminal.

Those. from a floor, apartment or group panel you need to lay 3 (three) wires, one of which is a protective zero (not ground at all). Which, however, does not at all prevent it from being used for grounding a computer, cable shield, or the “tail” of lightning protection. It seems that everything is simple, and it is not entirely clear why to delve into such complexities.

You can look at your home outlet... And with a probability of about 80% you will not see the third contact there. What is the difference between zero working and zero protective conductors? In the shield they are connected on one bus (even if not at the same point). What happens if you use the working zero as a protective zero in this situation?

It is difficult to assume that a careless electrician will confuse phase and zero in the panel. Although this constantly frightens users, it is impossible to make a mistake in any state (although there are unique cases). However, the “working zero” goes along numerous grooves, probably passing through several distribution boxes (usually small, round, mounted in the wall near the ceiling).

It’s much easier to confuse phase with zero there (I’ve done this myself more than once). As a result, 220 volts will appear on the body of the incorrectly “grounded” device. Or even simpler - a contact will burn out somewhere in the circuit - and almost the same 220 will pass to the housing through the load of the electrical consumer (if it is a 2-3 kW electric stove, then it will not seem too small).

For the human protection function, frankly speaking, this is a bad situation. But for connecting grounding, lightning protection type APC is not fatal, since a high-voltage isolation is installed there. However, it would definitely be wrong to recommend this method from a security point of view. Although it must be admitted that this norm is violated very often (and, as a rule, without any adverse consequences).

It should be noted that the lightning protection capabilities of the worker and protective zero approximately equal. The resistance (up to the connecting bus) differs slightly, and this is perhaps the main factor influencing the flow of atmospheric interference.

From the further text of the PUE it can be noted that towards zero protective conductor you need to connect literally everything that is in the house:

7.1.68. In all rooms it is necessary to connect open conductive parts of general lighting fixtures and stationary electrical receivers ( electric stoves, boilers, household air conditioners, electric towels, etc.) to the neutral protective conductor.

In general, it is easier to imagine this with the following illustration:

Rice. 4.6. Grounding diagram.

The picture is quite unusual (for everyday perception). Literally everything in the house must be grounded to a special bus. Therefore, the question may arise - after all, we lived without this for decades, and everyone is alive and well (and thank God)? Why change everything so seriously? The answer is simple - there are more electricity consumers, and they are becoming more powerful. Accordingly, the risks of damage increase.

But the relationship between safety and cost is statistical, and no one has canceled the savings. Therefore, it is not worth blindly placing a copper strip of a decent cross-section around the perimeter of the apartment (instead of a baseboard), placing everything on it, right down to the metal legs of the chair. How you shouldn’t wear a fur coat in the summer and always wear a motorcycle helmet. This is already a question of adequacy.

Also in the area of ​​an unscientific approach is the independent digging of trenches under the protective contour (in a city house this will obviously bring nothing but problems). But for those who still want to experience all the delights of life - in the first chapter of the PUE there are standards for the manufacture of this fundamental structure (in the very literal sense of the word).

Summarizing the above, we can draw the following practical conclusions:

If the group network is made of three wires, you can use protective zero. In fact, that’s what it was invented for.
If the group network is made of two wires, it is advisable to install a protective neutral wire from the nearest shield. The cross-section of the wire must be larger than the phase one (more precisely, you can check in the PUE).

With a two-wire network, the device body cannot be grounded to the working zero. IN as a last resort, and being careful, you can ground the lightning protection terminals with high-voltage isolation in this way.

This could be the end of the presentation if the network were located within one building (or rather, one room with a single bus). In reality, home networks have large aerial spans (and what is most unpleasant, they are performed at a decent altitude). Therefore, it is necessary to separately and in detail consider the issue of lightning protection.

STEN company: installation of grounding loops according to all rules, full complex electrical measurements

Many people have heard about such a necessary measure of electrical safety as grounding and generally imagine that grounding is a deliberate electrical connection of any point in the network or electrical equipment with a grounding device. What is grounding in relation to diesel power plants?

Regarding electrical safety measures, widely used diesel generators and related equipment (control panel, load transfer panel, ATS, distribution devices etc.), which are part of a diesel power plant, refer to electrical installations with voltages up to 1 kV, operating in networks with an isolated and solidly grounded neutral. Accordingly, the neutral of a diesel generator can be either isolated or connected to a grounding device. The first option is more common when using a diesel power plant as an autonomous power source, and the second when used in redundancy. centralized network with solidly grounded neutral. In the second case, the neutral of the diesel generator must be solidly grounded, and the grounding system of the power plant must correspond to the grounding system of the existing electrical installation in this network. Let us list these systems.

IT is a system with an isolated neutral of the power supply and grounding of exposed conductive parts of electrical installations.

TT system with a solidly grounded neutral of the power source and grounding of electrical installations using an independent grounding device. For electrical installations in networks with a solidly grounded neutral, several TN grounding systems are used, in which open conductive parts are connected to the solidly grounded neutral of the power source with neutral protective conductors.

IN TN-C system In one neutral conductor, the protective and working neutral conductors are combined along its entire length. In the TN-S system, the protective and working neutral conductors are separated along its entire length.

IN TN-C-S system The zero protective and zero working conductors are first combined in one, and then separated into independent ones.

It is clear that in any case, when operating diesel power plants, you cannot do without a grounding device.

The figure shows the application of the TN-S grounding system for a power plant used as backup source power supply and working in conjunction with four-pole automatic transfer switches.

We must not forget that grounding a diesel power plant is a measure used for the safety of people, and therefore is carried out in strict accordance with the current rules (PUE-7). It is performed using a grounding device consisting of grounding conductors and grounding conductors.

A grounding conductor is a conductor (electrode) or a set of conductors that has electrical contact with the ground, and a grounding conductor is a conductor for connecting a grounding point to a grounding electrode.

The connection of the grounding conductor to the ground electrode is performed by welding, and its connection to the power plant is by bolting. Can be used as natural grounding agents reinforced concrete foundations buildings, metal pipelines, etc. However, according to for various reasons, in In this case, it is not always possible to achieve a sufficiently low resistance of the grounding device. In addition, the use of pipelines for explosive and flammable substances is prohibited. If diesel generator is located in a building that has a grounding loop, it is allowed to be grounded through this loop. The best solution for a power plant is its own grounding loop. According to PUE-7, in networks with a solidly grounded neutral with line voltage 380V, the resistance of the grounding device should be no more than 4 ohms. The lower the resistance of the grounding circuit, the better, since in this case more current breakdown to ground and speed of operation of the protection relay. It depends mainly on the surface area of ​​the electrodes, the depth of their grounding, resistivity soil. Moreover, the latter is the main factor determining the grounding resistance. In turn, the resistivity of the soil is determined by temperature, moisture content, electrolytes and electrically conductive minerals, and therefore varies depending on the location and time of year. The figure shows a standard grounding circuit arrangement, where 3,4,5 are options for vertical grounding conductors made of angle steel, pipe and round steel, respectively, 2 is a horizontal grounding conductor made of strip steel, which connects everything vertical grounding conductors and to which a grounding conductor 6 made of round steel is welded. To him with the help bolted connection 1 connected grounding conductor from copper wire 8, which at the other end is connected to the main grounding bus (GZSh) in the input distribution device (IDU).

To effectively ground the power plant and ensure personnel safety, it is necessary to fulfill all the requirements for the elements of the grounding device, exact calculation its maximum permissible resistance. Such a calculation is possible only after measuring the soil resistivity using a device directly at the work site and must take into account seasonal coefficients. The measured resistance of the correct grounding device should not exceed the calculated norm. Later, during operation, in different time year, the necessary checks and measurements must be carried out to monitor the grounding condition of the power plant.

It is obvious that this work must be carried out by qualified specialists with the involvement of an electrical laboratory.

Our company has extensive experience in installing grounding loops for power plants. The work is carried out in full compliance with the PUE and PTEEP, with the issuance of a passport for the grounding loop. The electrical laboratory of the STEN company carries out the entire complex necessary measurements and checks, such as: checking the condition of the elements of the grounding device; checking the presence of a circuit and measuring the transition resistance between the grounding conductor, grounding conductors and grounded elements; measurement of earth resistivity; measuring the resistance of any grounding device; device check protective shutdown; measurement of the loop current “phase - zero”, etc. All results are recorded in the protocol.

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