One of the main conditions for the arrangement of electrical installations in rooms of various types and purposes is the grounding system. Paired with automatic shutdown equipment, the grounding system can significantly reduce the risk of fires in the event of short circuits. Grounding also significantly reduces the risk of injury. When installing any types of installations and electrical equipment, the main grounding bus GZSH according to the PUE must also be equipped. What it is? See our article today for the answer to this question.
Design features
By design, the grounding system consists of metal elements - one or more. These parts make it possible to securely connect the electrical equipment case to the ground.
Among the basic parts of this system, we can single out the main ground bus GZSH,ground wire in the wiring, tap from the housing, common circuit. In fact, the circuit is quite simple, but the system must provide the ability to individually connect / disconnect protective conductors with a special tool. The number of connections is five or more. It all depends on the chosen connection scheme. According to the requirements of GOSTs and PUE (Electrical Installation Rules), each part of the system must be made of steel (or its alloys) and copper. These requirements apply to any element, regardless of the type of construction of the ground loop and the electrical installation itself.
The main ground bus GZSh-copper 100x10 is the most preferred. This is due to high electrical conductivity, slow oxidation processes when exposed to high voltages, as well as the resistance of copper to corrosion. Steel elements are used only for the purpose of economy. The copper bus is often used in private housing construction.
The level of electrical resistance has a special effect on the effectiveness of protective circuits. Among the classic options for connecting to the main GZSH ground bus, ground loops, sewer and water mains can be distinguished.
Installation can be done by open or closed method. The installation location must be convenient for access and maintenance. The open type is popular at facilities where access to unauthorized persons is limited. But you can often find open installation in the panel boxes of residential buildings. Closedthe method is used in switchboard cabinets - in the boxes of the main ground bus GZSH.
Influence of resistance on the circuit
The total resistance of the grounding elements is called the indicator of each element separately, conductors or the entire circuit that is in the ground. Often this value is neglected. Parts made of metal (subject to a quality connection), have good electrical conductivity and low resistance.
Most important is soil resistance. The lower this indicator, the more efficient the system. Clause 7.1.101 of the Electrical Installation Rules states that in buildings with 220 or 380 V electrical networks, the resistance should not exceed 30 ohms. For generators, as well as for a transformer substation, the resistance level does not exceed 4 ohms.
In systems that are assembled on the basis of TN-S or TN-C circuits, it is necessary to equalize the potentials in each section of the circuit. GZSH is intended for these purposes.
TN-C
The TN-C scheme has been developed and has been in use since 1913. For the first time, ground loops were assembled along it in Germany. This type is used in old buildings throughout Europe, as well as in the post-Soviet countries. This scheme differs in the way the neutral conductor is connected. It is connected directly to the ground bus.
If the neutral wire breaks, voltages that exceed the phase voltage by 1.7 times may occur on the installation case. This greatly increases the risk of injury to people.
TN-S
TN-S has been around since the 1930s. It took into account and eliminated all the disadvantages of the previous connection option. The scheme provides for a separate wire that runs from the grounding system in the substation to the loop of the grounding system in the building through the GZSH. In the case of a combined connection in individual sections, it is permissible to connect the neutral conductor to the ground line using PE conductors. Electrical circuits of wires from any electrical installations to be grounded are connected to the GZSH. It is also possible to ground elements of other communications on it.
EIC requirements
In the rules for the arrangement of electrical installations, paragraph 1.7.119 defines all the basic requirements regarding the arrangement of the main ground bus GZSH in networks with a power of up to 1 kW. The system is located in the control cabinet of a specific device. In case of a large number of ground conductors, installation in a separate additional cabinet is allowed.
For systems implemented on the basis of TN-C, use the PE bus as the GZSH. But it should be borne in mind that the PE cross section must be larger than the wires themselves. For the arrangement of the GZSH, it is recommended to use copper. Rarely install steel. But aluminum is the biggest mistake. This material is strictly prohibited for use under these conditions.
All connections must be collapsible. They are usually bolted on. The wires are crimped to the lugs and then screwed onto the busbar. On the wall next to the latter, a symbol is necessarily applied indicating the groundingtire.
In paragraph 1.7.120 it is determined that for rooms with two or more inputs a separate bus should be equipped. It must be connected with conductors on various switchgears. Metal structures can be used to connect tires from various devices. But only on condition that they are non-separable and have constant electrical contact. At the same time, it is forbidden to use oil / gas / water pipelines, heating systems, cable sheaths, cables and supporting structures of cables as conductors for grounding. It is worth paying attention to an important nuance.
This is a common mistake when arranging the main grounding bus of the GZSH - the electrical installation rules (clause 1.7.20) allow grounding these structures on the main bus. However, connecting them directly from different cabinets using these designs is strictly prohibited. This is listed in clause 1.7.123 of the electrical installation rules.
Specifications
The main ground bus must be mounted in the electrical panel. Then it is connected to the ground loop. Inside the input equipment, tires of the PE type are used. In this case, the conductors must have a certain cross section:
- For copper - 1.1 cm and above.
- For aluminum - from 1.7 centimeters or more.
- For steel - from 7.5 centimeters.
The cross section of the ground bus must strictly correspond to the type and characteristics of the wire.
Design features
What is GZSH? This iscopper alloy plate with holes for connecting conductor tips. The size of the busbar and the number of holes depends on the type and dimensions of the cabinet, as well as the number of elements and wires that will be grounded. The reader can see the photo of the GZSH in this article.
Manufacturers make products in a variety of sizes. For example, the main ground bus GZSH-21 has a size of 395x310x120 millimeters. It is able to withstand current from 340 to 1525 amperes.
Mounting the GZSH in the cabinet
How is it done? For connection, a PE-type conductor and a box of the main grounding bus GZSH-10 or another are used. The tire should be positioned in such a way that in case of repair there is reliable and safe access to it. Its cross section should not be less than the ground wire. If necessary, you can connect several tires using standard fasteners.
Cabinets with rails are allowed to be placed on the front parts of buildings or in special switchboards. For outdoor or street lighting systems, you can choose a housing with an IP index. Installation includes fixing the busbar with a bolted connection in the cabinet body, connecting protective elements to the "zero" rail.
Installation outside the cabinet: technology, nuances
External installation of strips of the main grounding bus GZSH-10 can be performed in places where there is good protection from unauthorized persons. Fix the element on strong insulators. Among the most convenient options are DIN rails. It's metallicprofile that is used in the electrical industry. This rail can be aluminum or galvanized. But now the use of welding is popular. It complies with all GOSTs.
So, we found out what the main GZSH ground bus is, what requirements it must meet.
