Diesel generator with earthed neutral. Grounding the power plant or grounding. What is better to choose? What loads should be powered by the generator

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.
• Grounding copper wire corresponding 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 terminal.

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 resistivity soil with a special device at the work site. 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.

Grounding is a connection electrical appliance with grounding device. Consider how it is carried out in relation to diesel power plants.

Generators, control panel and switchgear must be grounded before starting and operating. This process must be carried out for security purposes, in accordance with the requirements adopted in Russia.

What is a diesel generator ground?

The grounding system usually consists of:

• ground electrode. Most often, steel rods coated with copper are used for this, which are buried in the ground. Note that in this case it is impossible to use pipes of underground water or gas pipelines.
• 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 provided with access for inspection. In this place, according to the requirements, a sign must be placed that says that there is a grounding system here.
• Ground clamp. It is located near the main circuit breaker of the power plant.
• Ground conductor. It connects all non-live metal parts of the installation to the earth terminal.

It is important to know that the connection of the earth clamp to the municipal earth electrode often requires the formal approval of the local authorities. This is necessary in areas where, in addition to the power plant, there is an electrical network common use, and the owner is the only person who is connected to the public supply transformer. Otherwise, you will have to install a separate ground electrode.

The connection of the conductor with the electrodes is carried out by welding, and with generator set- with the help of a special bolted connection on the body of the unit. It is necessary to dig the elements of the grounding system into the ground to a depth of 2.5-3 m.

The number of rods that can provide good diesel generator grounding, is determined depending on the soil. Its loop connection should be small, but sufficient so that, in the event of a ground fault, the current flow will allow the protective devices to operate.

Any installation with a mobile generator must have ground electrodes that are connected to the conductor and neutral. Instrument cables and wires must be as short as possible and free from loops to avoid overheating.

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When connecting an electric generator, you have to deal with three networks: a common centralized network, a network of energy consumers and wiring from the generator. Their connection and interaction determines the specific connection scheme. There are three ways to power devices that consume energy from an electric generator.

Energy consumers are connected directly to the generator socket. This circuit is very simple and needs no explanation. It does not require the creation of any additional circuits and network connections.

The generator is connected to a consumer network that is not connected in any way with a centralized network (it may not exist at all). In this case, the wires coming from the generator are permanently connected to the wiring of energy consumers. This connection scheme of the gas generator (diesel generator) is called constant. The main thing to take care of in this case is that the cross sections of the wiring wires correspond to the rated current of the generator.

The generator, through manual or automatic switching devices, is connected into a single circuit with a centralized network and consumer wiring. This connection scheme of the gas generator allows, in the event of a power failure in the centralized network, to easily and quickly power all consumers from the generator. It's called a backup.

Unlike the first method, which does not require any preparation (the plug of the powered tool or device is connected directly, or through an extension cord, to the socket located on the generator control panel), the last two methods require competent preparatory work. The third (reserve) connection scheme is the most complex and in demand.

Generator connection diagram as a backup power source

Scheme with manual mode switching. In the event of a power failure in the central network, by turning the key of the switch or the handle of the knife switch, they break the consumer network with the central network and connect it to the wires from the generator. The switch must guarantee the impossibility of simultaneous connection of electrical consumers to the centralized power grid and the generator (there must be an intermediate neutral position).

Reversing switches or toggle switches are used as a manual switch. When choosing these devices, you should pay attention to their rated currents. They must correspond to the consumed current (not be lower). Their design and connection diagram can differ significantly, for example, the diagram below shows a three-pole switch (one pole is not used) OT40F3С (far from the cheapest option).

In addition to the manual switch, you can put an indicator, the function of which is to indicate the presence or absence of voltage in the central network. It turns on between the phase and zero of the central network. These can be special modular 220V indicators, or cheaper (20 times) 220V indicator lights. closed case and already soldered wires.

The weak point of these indicators is that they are connected before the fuses.

Scheme with automatic mode switching. Automatic scheme connection of an electric generator allows, in the event of a power failure in the central network, to turn on the generator automatically without human intervention. This work is performed by the ATS (automatic transfer switch), consisting of a whole set of devices - contactors, voltage control relays, circuit breakers, indication elements.

The generator, which is switched on automatically, must have an electric starter. To turn on backup source to work, you must disable centralized network, start and warm up the generator, connect the wiring from it to the consumer network. When a central tension appears, reverse work. All this is performed by the AVR block.

Exist various systems automatic input of a reserve, differing in their functionality. They work as follows, using the example of the Champion ATS block for gasoline generator GG7000E. When the power supply from the central network is interrupted, the program for starting the ATS unit is launched. First, energy consumers are disconnected from the centralized network. After 2-3 seconds, the generator engine starts and its operation is checked. During normal operation of the unit, after 12 seconds. after starting the engine (warming up), the generator is connected to consumers of electricity.

When power is restored from common network, the system monitors the stability of the supplied electricity. If stability is detected for 10 seconds, ATS automatically switches consumers to power from the public network. The generator runs without load for another 5 seconds, then the ATS system stops it.

Load switching order

Connection errors

Both of these are unacceptable. Plugging the generator wires into a consumer network socket, in case of a heavy load, can cause destruction of the socket and electrical wiring with a risk of fire, since the size of the socket contacts and the cross section of its wires are not designed for high currents flowing in the generator network. And if you do not turn off the centralized network (for example, forgetting), then when voltage appears in it, the generator will fail.

Installation of an electric generator

The installation site of the gas generator or diesel generator must be dry and level. There must be no flammable objects nearby.

Not every the room is suitable to install a power generator. There are certain ventilation requirements. So, in a closed room, it is necessary to organize supply and exhaust ventilation using a duct system or built-in fans. Thus, the supply of cold air and the removal of heated air will be ensured. If the generator is placed, for example, in a basement or pantry, it will overheat, even if there is an open window. As a result, the generator will break down.

Noise protection

When installing a diesel generator or gas generator, make sure that the base on which the unit is installed is not rigidly connected to the building. It is advisable to install the generator on shock absorbers, the simplest of which can be a conventional rubber gasket.

The noise coming from the surface of the generator is reduced by means of noise protection covers. Factory-made casings work most efficiently - special containers in which sound and vibration insulating materials are used and supply and exhaust ventilation, providing the necessary normal operation generator temperature.

You can make a container yourself, but this is not as simple as it might seem at first glance. Mainly because of the need to ensure effective ventilation.

Container for gasoline generator. Air is forced through the lower air duct closer to the engine.

Noise coming from exhaust gases, reduce with silencers. But manufacturers are prohibited from installing additional mufflers, and making any changes to the design will void the warranty. Installing a silencer can result in reduced power and difficult starting. Moreover, it is not the most effective method noise control, because sounds arise not only from the operation of the engine, but also from vibration. Therefore, it would be wiser to pay more attention to the place where the generator is installed. In a room or casing, walls are recommended to be upholstered with a special soundproof material- in one or two layers, depending on how noisy the generator is.

grounding

• a metal rod with a diameter of at least 15 mm, a length of at least 1.5 m;
• a metal pipe with a diameter of at least 50 mm, a length of at least 1.5 m;
• a sheet of galvanized iron with a size of at least 500x1000 mm.

Any grounding conductor must be immersed in the ground to constantly wet soil layers. Grounding conductors must be equipped with clamps or other devices that ensure a reliable contact connection of the ground wire with the grounding conductor. The opposite end of the wire is connected to the generator ground terminal.

Exhaust gas outlet

The problem is that the extension of the exhaust pipe, as well as the additional muffler, creates additional resistance to the exit of the exhaust gases. This significantly affects engine power, durability and fuel consumption. The resistance to the release of exhaust gases from the cylinder causes incomplete combustion of the fuel, an increase in the operating temperature of the exhaust gases, and the formation of soot. Typically, manufacturers of gas generators prohibit extending the exhaust pipe and installing an additional muffler. To minimize the resistance to the exhaust outlet, the following principles should be followed:

• The inner diameter of the pipe must be larger than the diameter of the generator exhaust pipe. The more (within reason) the better. And the longer the pipe, the larger the diameter should be.
• The length of the work should be as short as possible.
• Must be least amount bends.
• The curves should be as smooth as possible.

Parts of the exhaust system must not be located near wood or other combustible materials. To reduce the room temperature, it is necessary to use non-flammable thermal insulation materials. Layer insulating material, wrapped around the piping, can significantly reduce heat radiation into the room from the exhaust system. Thermal insulation The exhaust pipe is especially important when the generator is running in a wooden container.

A corrugated stainless steel hose installed between the generator exhaust pipe and the rest of the pipeline reduces the transmission of vibration from the engine to the pipeline and building, and compensates for the forces resulting from thermal expansion. The design of the flexible section must allow displacement of either end in any direction without damage. The piping must not rest on the exhaust pipe of the generator.

The exhaust system must be equipped with a condensate trap with a condensate drain, located in the lowest part of the pipe inside the room. Or a corrugated stainless steel hose should have a bend below the level of the generator exhaust pipe, in order to prevent street condensate from entering the generator.

The outlet must be under a canopy to prevent atmospheric precipitation from entering the system. It is also recommended that restrictions be placed on children's access to outer pipe, as the temperature and composition of the exhaust gases can pose a threat to their health.

In the hole in the wall through which the pipe passes to the street, insulation must be provided from high temperature pipes and to absorb vibration.

Neglect in the removal of exhaust gases can cause death. Here are some examples:

"Dead 14-year-old girls were found in a private residential building, poisoned carbon monoxide. The cause of death was a portable diesel generator. One of the girls, in the absence of her parents, invited two girlfriends and, since the power supply was turned off in the house, she turned on the diesel generator on her own. As a result of a violation of the operating technique, three children suffocated from carbon monoxide.

“A family that died in the village of Yuzhnaya Koryaki suffocated due to a working diesel generator, the exhaust gases of which got into the house. Long-term power outages forced the family to use an alternative source of electricity. As already reported, after the cyclone, part of the Yelizovsky district remained without electricity for about a day and people fled from the cold whoever can. And only today the whole family, consisting of two sons, one of whom was a minor, mother, father and their close relative, were found without signs of life by neighbors.

"According to preliminary data, on the evening of February 12, the men decided to take a steam bath in wood-burning bath. Her 65-year-old Kurchatovian settled in basement your garage. The bathhouse was lit by a gasoline generator. Steam room lovers started the generator and began to put firewood into the firebox. The door was closed and the exhaust gases from the gasoline generator quickly filled closed room garage. 50-year-old Kurchatov became ill. He fell in the waiting room - suffocated with carbon monoxide. The owner of the garage, feeling the lack of oxygen, rushed to the garage door to open it. But he didn't manage to do it. Having lost consciousness, the man fell on the threshold and also suffocated. The next day, relatives of the Kurchatovites, worried about their long absence, opened the garage and, finding two corpses there, called the police.

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Diesel generators have a lot of rotating parts, and the laws of physics dictate that friction causes static electricity. Therefore, for safety reasons (avoiding the appearance of sparks from static and ignition), they must be grounded before starting operation.

Grounding device

The grounding system includes:

• Clamp (all conductors are attached to it), it is located near the main circuit breaker of the diesel device.
• Conductor. It integrates the ground clamp with all metal parts that are not energized.
• An electrode representing a steel rod coated with a copper alloy. He burrows into the ground. There may be several electrodes.
• A copper wire of a certain cross section that connects the clamp to the electrode. The place where they are connected must be protected from damage, but free for inspection. Here it is required to install a sign warning about the location of the grounding system “Do not touch. Electrical grounding.

In areas where there is a power grid (public), and the owner is a single consumer connected to a supply public transformer, permission must be taken from the authorities to connect to the electrode (municipal). If permission is not given, a separate earth electrode must be installed.

The conductor with the generator is connected with the help of bolts located on its body, with the electrodes - by welding. Elements of the grounding system are dug in at 2.5 - 3 meters.

Depending on the resistance of the soil, the number of rods for better grounding diesel unit. To protective devices could work (in the event of a malfunction), a loop connection should be sufficient (but not excessive).

If a current leakage occurs during a fault, its level is calculated according to the formula given in the requirement I. E. E. Regulations.

Grounding electrodes connected to the neutral and the conductor must have each installation with a mobile (mounted on a tractor or trailer) generator.

What to use for grounding

For grounding, you can use one of these grounding conductors:

• Galvanized iron (sheet). Its size is 50 cm x 100 cm.
• A metal rod 1.5 - 1.6 cm in diameter, at least 150 cm long.
• Metal pipe (length not less than 150 cm, diameter - 5 cm).

Important: it is forbidden to use pipelines for water and gas for grounding.

Reliable contact connection of the grounding conductor with the ground wire must be provided by special clamps. The other end of the wire is connected to the diesel generator ground terminal. 4 ohms and no more - this is the resistance of the ground loop, which should be close to the diesel device.

The grounding conductor is immersed in the ground to wet soil layers.

Grounding systems

For those operating as stand-alone power sources, an isolated neutral ground is used. For the central network, apply solidly grounded neutral. Grounding systems are:

Important: only a specialist (in accordance with regulations) should ground the equipment and calculate the allowable maximum resistance. The implementation of these actions requires, in addition to high professionalism, the availability of special equipment.

Most people know that a grounding system is necessary for electrical safety when installing a generator. However, they have enough general idea that grounding is a special connection of the mains or electrical appliances with a grounding mechanism at a certain point. The question arises, how to properly ground diesel generator?

With regard to electrical safety measures, commonly used diesel power plants and their associated devices (control panel, power switching system, automatic transfer device, distributors, etc.), which includes a diesel generator set, are classified as electrical equipment with a voltage of not more than 1 kV.

These power plants are used in power networks where the neutral of a transformer or generator is connected to a grounding mechanism:

• directly
• through the resistance of devices
• doesn't connect at all

Therefore, the first version of the neutral can be called dead-earthed, and the second - isolated. The neutral of the second type is usually used in the case of using a diesel generator as an additional power source that ensures its autonomous delivery, and when reserving the main electrical network, the neutral of which is of a solidly grounded type, the generator is connected to the grounding mechanism through resistance or not connected at all. Let's name such mechanisms:

It is important to remember that the organization of the grounding of diesel power plants is a necessary measure to ensure safe use this equipment. That is why, when installing a grounding system, one should strictly follow the specially developed rules (PES-7).

This statement is true for absolutely all models that can be seen in the section diesel generators >>>

To organize grounding, grounding devices are required:

• Grounding - is a single conductor (electrode) or a system of such electrodes that are in electrical contact with the ground.
• Ground conductor- a device that connects the grounding point and the ground electrode. To connect the ground conductor to the ground electrode, you will need welding machine, and for its connection to the electric generator - a bolted connection.

Cast natural grounding may speak reinforced concrete foundations buildings, pipes made of metal, etc. True, due to different reasons, when using them, the resulting resistance may not be low enough. In addition, it is forbidden to use pipelines for explosive and flammable compounds. In the event that a diesel generator is located in a building equipped with a ground loop, it is allowed to ground it through this loop. The best option for diesel station- this is the creation of an individual ground loop.

It is important to know! Taking into account the main provisions of PES-7 for power networks with a dead-earthed neutral and the value line voltage 380 V, the resistance of the grounding device must not exceed 4 ohms. It is considered optimal smallest value grounding circuit resistance indicator, which is explained by a larger value of the breakdown current to the ground and a faster response of the protective switch of the circuit.

Resistance is primarily determined by:

• the surface area of ​​the electrodes
• ground depth
• earth resistivity

In this case, the latter indicator is the main one, because it determines the resistance value to a greater extent. Soil resistivity also depends on a number of parameters: temperature, soil moisture, concentration of catholytes and electrically conductive mineral compounds. From this it follows that this indicator differs depending on the time of year and locality.

In order to qualitatively ground the electric generator and create safe conditions labor for workers, you should fulfill the entire list of requirements that apply to all components of the grounding mechanism, as well as carefully calculate its maximum allowable resistance. This calculation can be made only with a known index of soil resistivity, which is measured by special device right in the work area. In this case, you should remember about seasonal coefficients. Normally, the resulting resistance value should not exceed the calculated standard.

There is no doubt that such work should be carried out only by qualified personnel using an electrolaboratory. Over the years, our company has acquired a huge amount of knowledge in the field of installation of ground loops for power generators. The technologies for carrying out all work are fully consistent with the PUE and PTEEP. After they are carried out, we are guaranteed to issue a passport for the installed equipment.