Grounding the generator set when connected to a fixed network. Lightning protection and grounding for container facilities. Exhaust gas outlet

Generally speaking, it can be noted that the great and terrible power of electricity has long been described, calculated, listed in thick tables. Normative base, defining the paths of sinusoidal electrical signals frequency of 50 Hz is able to plunge any neophyte into horror with its volume. And despite this, any frequenter of technical forums has long known that there is no more scandalous issue than grounding. The mass of contradictory opinions in fact 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 in order to understand the grounding technology, you need to refer (to begin with) to Chapter 1.7, which is called "Grounding and Electrical Safety Protective Measures".

In clause 1.7.2. says:

Electrical installations in relation to electrical safety measures are divided into:

electrical installations above 1 kV in networks with effectively grounded neutral(with high earth fault currents), ;
electrical installations above 1 kV in networks with isolated neutral (with low earth fault currents);
electrical installations up to 1 kV with dead-earthed neutral;
electrical installations up to 1 kV with isolated neutral.

In the vast majority of residential and office buildings in Russia, a dead-earthed neutral is used. Clause 1.7.4. reads:

A dead-earthed neutral is a transformer or generator neutral connected to a grounding device directly or through low resistance (for example, through current transformers).

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

When describing other options for electrical installations, it is easiest to do as in one of the Rolls-Royce instructions - "if the car breaks down, your driver probably knows what to do." At the very least, schemes other than dead-earthed neutral are slightly more common in the construction of home networks than Rolls-Royces on the streets.

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

1.7.6. Grounding 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 in order to ensure electrical safety.
1.7.8. Working grounding is the grounding of any point of the current-carrying parts of the electrical installation, which is necessary to ensure the operation of the electrical installation.
1.7.9. Zeroing in electrical installations with voltages up to 1 kV is the intentional connection of parts of an electrical installation that are not normally energized with a dead-earthed neutral of a generator or transformer in networks three-phase current, with solidly grounded source output single-phase current, with a dead-earthed midpoint of the source in networks direct current.
1.7.12. A grounding conductor is a conductor (electrode) or a set of metal-connected conductors (electrodes) that are in contact with the ground.
1.7.16. A grounding conductor is a conductor connecting the grounded parts to the ground electrode.
1.7.17. A protective conductor (PE) in electrical installations is a conductor used to protect against electric shock to people and animals. In electrical installations up to 1 kV, a protective conductor connected to a dead-earthed neutral of a generator or transformer is called a neutral protective conductor.
1.7.18. Zero working conductor (N) in electrical installations up to 1 kV is a conductor used to power electrical receivers, connected to 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 source point in three-wire DC networks. A combined zero protective and zero working conductor (PEN) in electrical installations up to 1 kV is a conductor that combines the functions of a zero protective and zero working conductor. In electrical installations up to 1 kV with a solidly grounded neutral, the zero working conductor can perform the functions of a zero protective conductor.

Rice. 4.5. difference protective earth 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 at this point). At the very least, they must be combined (or even can be performed "in one bottle"). The only question is where and how it was done.

In passing, we note paragraph 1.7.33.

Grounding or grounding of electrical installations should be carried out:

at a voltage of 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 rooms with increased danger, especially dangerous and in outdoor installations.

In other words, it is not necessary to ground or neutralize a device connected to 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 (or a new edition of the PUE close to it) that comes into practice in practice is better, more reliable, and safer. But according to the old PUE, we lived in our country for decades ... And what is especially important, houses were built by entire cities.

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

15.4. For grounding (zeroing) metal cases household air conditioners, stationary and portable household appliances class I (without double or reinforced insulation), household electrical appliances the power of St. 1.3 kW, cases of three-phase and single-phase electric stoves, digesters and other thermal equipment, as well as metal non-current-carrying parts technological equipment premises with wet processes, a separate conductor with a cross section equal to the phase should be used, laid from the shield or shield to which this electrical receiver is connected, and in the lines supplying medical equipment - from the ASU or main switchboard of the building. This conductor is connected to the neutral conductor of the mains. The use of a working neutral conductor for this purpose is prohibited.

This creates a normative paradox. One of the results visible at the household level was the acquisition of washing machines"Vyatka-automatic" skein 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, zeroing must be performed. The use in such electrical installations of grounding the housings of electrical receivers without their grounding is not allowed.

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

Grounding parameters

The next aspect to consider is numerical parameters grounding. Since physically it is nothing more than a conductor (or a set of 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 outputs 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 660, 380 and 220 V three-phase supply or 380, 220 and 127 V single-phase supply. This resistance must be provided taking into account the use natural grounding, 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 ground electrode located in the immediate vicinity of 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, more 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 electrical installation case. The lower the resistance, the smaller part of the potential may be "on the case" in the event of an accident. Therefore, the risk for higher voltages must be reduced first.

In addition, it must be taken into account that grounding also serves for the normal operation of the fuses. To do this, it is necessary that the line during the breakdown "to the body" significantly change its properties (primarily resistance), otherwise the operation will not occur. The greater the power of the electrical installation (and the voltage consumed), the lower its operating resistance, and, accordingly, the ground resistance must be lower (otherwise, in case of an accident, the fuses will not work from little change total circuit resistance).

The next normalized parameter is the cross section of the conductors.

1.7.76. Grounding and zero protective conductors in electrical installations up to 1 kV must have dimensions not less than those given in Table. 1.7.1 (see also 1.7.96 and 1.7.104) .

It is not advisable to give the entire table, an excerpt is enough:

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

Grounding in a residential building

In a normal "household" situation, power grid users (i.e. residents) deal only with the Group network (7.1.12 PUE. Group network - a network from shields and distribution points to lamps, socket outlets and other electrical receivers). Although in old houses where shields are installed directly in apartments, they have to deal with part of the Distribution Network (7.1.11 PUE. Distribution Network - a network from VU, ASU, Main Switchboard to distribution points and shields). It is desirable 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 laid from group, floor and apartment shields to lamps general lighting, socket outlets and stationary electrical receivers must be three-wire (phase - L, zero working - N and zero protective - PE conductors). It is not allowed to combine zero working and zero protective conductors of various group lines. Zero working and zero protective conductors are not allowed to be connected on shields under a common terminal.

Those. 3 (three) wires must be laid from the floor, apartment or group shield, one of which is a protective zero (not earth at all). Which, however, does not prevent at all from using it for grounding a computer, a cable screen, or a "tail" of lightning protection. Everything seems to be simple, and it is not entirely clear why go into such complexity.

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

It is difficult to assume that a negligent electrician will confuse the phase and zero in the shield. Although this constantly scares users, it is impossible to make a mistake in any state (although there are unique cases). However, the "working zero" goes through numerous strobes, probably passes through several junction boxes (usually small, round, mounted in the wall near the ceiling).

It is already much easier to confuse the phase with zero there (I did it myself more than once). And as a result, 220 volts will appear on the case of an incorrectly "grounded" device. Or even simpler - a contact will burn out somewhere in the circuit - and almost the same 220 will pass to the case through the load of the electrical consumer (if this is an electric stove for 2-3 kW, then it will not seem enough).

For the function of protecting a person, frankly, this is an unsuitable situation. But for grounding connection, lightning protection of the APC type is not fatal, since a high-voltage decoupling is installed there. However, it would be unequivocally wrong to recommend such a method from a security point of view. Although it must be admitted that this rule is violated very often (and usually without any adverse consequences).

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

From the further text of the PUE, it can be seen that to zero protective conductor you need to attach 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, domestic air conditioners, electric towels, etc.) to the neutral protective conductor.

In general, it is easier to represent the following illustration:

Rice. 4.6. Grounding scheme.

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

But the dependence of safety and cost is a statistical value, and no one has canceled the savings. Therefore, it is not worth blindly laying a copper strip of a decent section around the perimeter of the apartment (instead of a plinth), leading everything to it, up to the metal legs of the chair, is not worth it. How not to walk in a fur coat in the summer, and constantly wear a motorcycle helmet. This is a question of adequacy.

Also, independent digging of trenches under a protective contour should be attributed to the area of ​​\u200b\u200ba non-scientific approach (in a city house, apart from problems, this will certainly bring nothing). And for those who still want to experience all the delights of life - in the first chapter of the EMP there are standards for the manufacture of this fundamental structure (in the truest sense of the word).

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

If the Group network is made with three wires, you can use protective zero. It is, in fact, designed for that.
If the group network is made with two wires, it is advisable to have a protective neutral wire from the nearest shield. The cross section of the wire must be more than the phase one (more precisely, you can consult the PUE).

With a two-wire network, it is impossible to ground the device case to a working zero. IN last resort, and being careful, you can ground the conclusions of the lightning protection with high-voltage decoupling in this way.

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

STEN company: installation of ground loops according to all the 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 a point in a network or electrical equipment with a grounding device. What is grounding in relation to diesel power plants?

With regard to electrical safety measures, widely used diesel generators and their associated equipment (control panel, load transfer panel, ATS, switchgears etc.), which are part of a diesel power plant, refer to electrical installations with voltage up to 1 kV, operating in networks with insulated and solidly grounded neutral. Accordingly, the diesel generator neutral 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 redundant centralized network with earthed neutral. In the second case, without fail, the neutral of the diesel generator must be deafly grounded, and the grounding system of the power plant must correspond to the grounding system of the existing electrical installation in this network. Let's list these systems.

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

TT - system with 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 exposed conductive parts are connected to a solidly grounded neutral of the power source with neutral protective conductors.

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

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

It is clear that in any case, when operating diesel power plants, a grounding device is indispensable.

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

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

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

The grounding conductor is connected to the grounding conductor by welding, and its connection to the power plant by bolting. Can be used as natural grounding conductors reinforced concrete foundations buildings, metal pipelines, etc. However, by 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 combustible substances is unacceptable. If diesel generator located in a building with a ground loop, it is allowed to ground it through this loop. The best solution for a power plant is its own ground loop. According to PUE-7, in networks with a solidly grounded neutral with a linear voltage of 380V, the resistance of the grounding device should be no more than 4 ohms. The lower the resistance of the ground circuit, the better, since in this case more current ground fault and protection relay operation speed. It depends mainly on the surface area of ​​the electrodes, the depth of their grounding, and the resistivity of the soil. Moreover, the latter is the main factor determining the grounding resistance. In its turn, resistivity soil is determined by temperature, moisture content, electrolytes and electrically conductive minerals, and therefore varies depending on the place and season. The figure shows a standard ground loop 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 that connects all vertical earthing switches and to which a ground conductor 6 made of round steel is welded. To him with bolted connection 1 connected ground conductor from copper wire 8, which is connected at the other end to the main ground bus (GZSH) in the input-distribution device (ASU).

For effective grounding of the power plant and ensuring the safety of personnel, it is necessary to fulfill all the requirements for the elements of the grounding device, exact calculation its maximum allowable resistance. Such a calculation is possible only after measuring the soil resistivity using the device directly at the work site and must take into account seasonal factors. The measured resistance of the correct grounding device should not exceed the calculated norm. Later, during operation, different time year, the necessary checks and measurements must be carried out to control the condition of the power plant's grounding.

It is obvious that these works must be carried out by qualified specialists with the help of an electrical laboratory.

Our company has extensive experience in the installation of ground 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 ground loop. The STEN electrical laboratory performs the entire complex required measurements and checks, such as: checking the condition of the elements of the grounding device; checking the presence of a circuit and measuring the contact resistance between the grounding conductor, grounding conductors and grounded elements; earth resistivity measurement; measurement of resistance of any grounding device; device check protective shutdown; measurement of the loop current "phase - zero", etc. All results are recorded in the protocol.

To place an order for the performance of work, to find out their cost, you just need to contact the manager using the phone or e-mail.

Most people know that grounding is necessary for safety when installing any electrical appliance, including a power generator. At the same time, few people understand what it is and how exactly the grounding system ensures safety.

So, why is grounding necessary and what will happen if it is not?

To answer these questions, you first need to remember from school course physics, what is electricity- the movement of charged particles in a conductive substance (conductor). The human body is also a conductor of current.

Why is current dangerous? Everyone has heard the expression: "shocked." In this blow lies its danger to a person, starting with unpleasant sensations, ending with a fatal outcome. To receive an electric shock, it is not enough just to touch a wire or part of a live device - it is necessary that there is an electrical circuit.

In practice, there is always such a chain, since we are constantly standing on the ground or on the floor, holding or touching objects. On contact with a wet surface, the potential difference increases and electric shock can be fatal.

In order to protect yourself from electric shock, grounding is necessary. Grounding is a special connection of the electrical network or electrical appliances with a grounding mechanism at a certain point. The essence of grounding is that all metal parts of the equipment are connected to a wire that goes to the ground. It is through this wire that the electric current goes into the soil, and not through a person, thereby ensuring the safety of the latter.

Before starting and starting the operation of the electric generator, it must also be connected to a ground loop, made in accordance with the requirements of the PUE.

• Grounding electrode (ground electrode). Copper-plated steel rods are best suited for this, which are buried in the ground in a certain pattern. Note that in this case it is impossible to use pipes of underground water or gas pipelines.
• Ground clamp. It is located near the main circuit breaker of the power plant.
• Earthing copper wire of the appropriate section. It connects the electrode to the clamp. It is important to remember that the place where the ground electrode and wire are connected must be protected from accidental damage and must be accessible for inspection. In this place, according to the requirements, a sign must be placed that says that there is a grounding system here.
• Ground conductor. It connects all non-live metal parts of the installation to the earth clamp.

In order to effectively carry out all procedures for grounding the power plant and ensure safety, it is necessary to clearly follow all PUE requirements(Electrical Installation Rules) and accurately calculate the maximum allowable resistance. This calculation is only possible when measuring soil resistivity special device at the place of work. Moreover, seasonal factors must be taken into account.

Undoubtedly, the installation of the grounding device should only be carried out by qualified personnel using special tools.

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

Let us consider the case when the object of the protective grounding installation is the DGU container (diesel generator set). In accordance with the customer's data, the soil at the proposed installation site of the EGE-4 grounding device (alluvial sandy loam gray color soft-plastic) and EGE-3 (alluvial-deluvial loam Brown hard plate), ground water at a depth of 2.5m.

Let us take the specific soil resistance equal to 100 Ohm∙m.

In accordance with the PUE, clause 1.7.101, the resistance of the grounding device to which the neutrals of the generator or transformer or the outputs of a single-phase current source are connected, at any time of the year 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 current.

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

Protection of buildings from lightning discharges is carried out with the help of lightning rods. A lightning rod is a device that rises above the protected object, through which the lightning current, bypassing the protected object, is diverted to the ground. It consists of a lightning rod that directly perceives a lightning discharge, a down conductor and a ground electrode.

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

Installation of one lightning rod-mast for 3 concrete bases 4 meters high. Installation is carried out on the roof of the container;

The device of two down conductors with the use of copper-plated wire D=8 mm. Down conductors should be located no closer than 3 m from the entrances or in places inaccessible to people. Mounting of down conductors on the roof is carried out using clips GL-11706. The down conductor is fixed to the vertical surfaces of the building using clamps GL-11704A.

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 30 × 4 mm). The distance between the 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 the control clamp GL-11562A.

Calculation of the resistance of the grounding device:

Horizontal electrode resistance:

where ρ is the resistivity of the soil, Ohm m;

b - strip width of the horizontal electrode, m;

h is the depth of the horizontal grid, m;

L mountains - the length of the horizontal electrode, m.

Vertical electrode resistance:

Where ρ eq - equivalent soil resistivity, Ohm m;

L- length of the vertical electrode, m;

d- diameter of the vertical electrode, m;

T- deepening - the distance from the earth's surface to the ground electrode, m;

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

Grounding device impedance:

Where n- number of sets;

k isp - utilization factor;

The design resistance of the grounding device is 3.89 ohms.

Figure 1 - Protection zone B according to AD

Figure 2 - Layout of grounding and lightning protection elements

Scroll necessary materials is shown in table 1.

Table 1 - List of material requirements

No. p / p	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