When constructing a new residential building, property owners try to provide it with various means of protection, including from lightning strikes. To do this, it is imperative to make the correct grounding loop according to all standards since otherwise it does not guarantee reliable protection. In this regard, there is a need for a thorough study of the rules and regulations of the PUE.
PUE norms are a collective group of special normative legal acts that were written under the USSR by the Ministry of Energy – rules for the design of power installations. These rules for electrical installations contain a description of how to properly create electrical wiring in residential buildings, factory premises and other structures; they have a description of various devices, as well as the principle of their construction. PUE includes the conditions for laying communications of electrical installations, components, requirements for certain systems and their elements.
Very often, PUE standards are used when installing electric lighting in buildings, various premises, as well as streets, towns, and territories of certain institutions or enterprises. They contain conditions for the installation of ultraviolet irradiation in health-improving structures, advertising with lighting devices, and more. When laying wiring in buildings, refer to a specific section of the PUE standards.
In separate sections you can find recommendations on how to make a grounding loop, how to install electrical protective devices, and other rules for the operation of various electrical equipment. More detailed and precise information about the conditions for using such equipment is written in the Rules for the Technical Operation of Consumer Electrical Installations (PTEEP).
Today, if you follow all the rules of the PUE for installing and connecting different types of wiring, laying a grounding loop or other technical solutions, the cost of such work will be very high. For this reason, these standards are followed superficially, observing only the most important instructions, and for others they try to find an alternative solution. Despite the high cost, these rules make it possible to effectively protect a building of any type from various negative factors.
Standards regarding ground loops
It is strongly recommended that the installation of the ground loop be done with reference to the PUE standards. This approach will allow you to make all the necessary connections and connect the circuit correctly in compliance with all standards. This will ensure reliable operation of the protection system in the building, preventing the negative consequences of natural or anthropogenic factors. To make a ground loop with your own hands, you should have some knowledge in the field of electrical engineering. Before work, it is recommended to read the necessary literature, as well as sections of the PUE that refer to the installation of the ground loop.
According to the current Rules for Electrical Installations, the secondary circuit must be located at the exit points of any type of building. Natural grounding conductors should be installed in place of the repeated grounding loop. The rules specify some metal structure trimmers that are suitable for grounding. Among them you can find reinforced concrete structures, massive metal parts that must come into contact with the ground with most of their surface. If the circuit is connected in an aggressive environment, then such structures must have a special protective coating. Also suitable for a grounding element are a metal water pipe that is dug deep into the ground, or long rails from non-electrified railways.
You must definitely pay attention to the PUE clause, which indicates elements that cannot be used as a ground loop. These include reinforced concrete structures with metal elements that are energized, as well as pipelines with flammable substances, heating and sewer pipes. If the circuit must be made using a natural grounding device (soil, foundation under a building), then you must first make theoretical calculations and a connection diagram.
Typically, during the construction of a new building, the ground loop is made artificially by burying supports underground. This method is considered more universal and is used much more often in practice. This is dictated by the fact that not all places have suitable conditions for natural grounding.
A very important factor that influences the circuit is soil resistance. So in places with high soil moisture, the resistance will be low. Significant installation problems arise on dry soil. For example, sandy soils, rocky or stone formations are completely unsuitable for such work.
The regulatory documents indicate the exact resistance value that determines the level of current flow, as well as what resistance the circuit should have.
There are two types of grounding used in household electrical installations.
Traditional ground loop. In this case, the main grounding element must be made of several vertical supports and one horizontal one. They must have a round cross-section and be smooth. To do this, you can use steel rods, pipes or thick reinforcement. For ordinary private houses, it is advisable to use large-sized supports. If steel reinforcement is used, then you can take 3 such elements with dimensions starting from 2 meters. They are set so that an equilateral triangle is formed if the installation location of the reinforcement is at the vertices of the conventional figure. Before you begin installing the supports, you need to measure the distance between them. The more space between them, the better. The distance between the grounding elements should be at least 1.5 meters. After making sure that the measurements correspond to the norm, you can begin installing the circuit.
When the elements are driven into the ground, a reliable connection should be made between them. Can be attached with separate fasteners at the same height. The connection of all supports is made using horizontal grounding conductors closer to the top of the electrodes. According to PUE standards, connections must be made of steel or copper. Each element can be connected to the transverse electrode by welding. This method is more reliable than movable fasteners (nuts, bolts). As for the sizes of these electrodes, they have standardized smallest values. When installing, preference should be given to longer supports.
When a ground loop is considered for residential buildings, it should be located in a place where people rarely visit. It is advisable to choose the north side. Since this part is illuminated less frequently, the earth retains more moisture.
The distance to the walls of the building must be more than 1 meter.
Deep ground loop. This type eliminates most of the disadvantages that are present in the traditional method. This method involves a modular-pin system. This design is made in specialized factories and has a certificate. The modular pin system has several advantages. First of all, this is compliance with all technical norms and standards. It has a long service life of more than 30 years. This design always has a stable resistance to the spreading of an electric charge under any weather conditions. The supports are driven 25-30 meters deep into the ground, which ensures reliable grounding of large buildings.
Such a system does not need to be constantly checked, as it is quite simple and reliable. The design and calculation of the grounding conductors of a modular-pin system are simpler than a do-it-yourself protection system.
When a private house or separate room has been equipped, then before connecting it, the actual readings of the entire system should be measured. If after measurements the indicators correspond to the standard data, then the installation and connection of the circuit were done correctly. Measurements of this kind, as well as checking the connection and installation diagram, are checked by a specially certified electrical laboratory. After verification, it issues an expert technical report with a separate number and is then entered into the register. Having made measurements at the main connection points, as well as the resistance, they fill out a technical passport for grounding loops, draw up a test report and sign an acceptance certificate for the corresponding system.
Special sockets must be installed in the premises, which are designed to connect wires with grounding. To make the connection, you need to lay a three-core power cable with a ground wire in advance. In addition to phase and neutral, the ground wire is also connected to the socket. It must be connected to the terminal, which is located between the sockets of the socket.
Before starting work, you need to make a grounding loop diagram, and you also need to take appropriate measurements. For each room or entire house, there are rules for calculations. The design of a specific building is carried out separately. For example, let’s take into account a small country house. To calculate the ground loop, you need to have the initial data:
- priming. Clay soil with a resistance of 60 Ohm*m.
- grounding elements. Metal corner with dimensions: thickness – 50 mm, length – 2.5 m, width – 5 cm.
- the distance between supports is 2.5 m.
- The trench depth for the structure is 0.7 m.
- you need a grounding resistance of 10 ohms.
For calculations, all data must be converted to one unit of measurement (for length in meters). From the PUE tables, coefficients are determined for specific climatic conditions and the length of vertical supports. The actual value of soil resistance will differ from the theoretical value since the weather in the region affects the calculations. With measurement data, we use the 2nd climate zone.
Using these measurements and data, when calculating using the basic formula, we obtain the value R = 27.58 Ohm. Once the resistance value of a single grounding support has been determined, it is used when calculating the number of required grounding elements in the structure. In this case, there should be 3 of them. After the calculation results have been obtained, you need to draw up a conditional diagram. This makes it easier to understand the structure and record the values of all its elements separately. It is advisable to save the diagram after installation in case repeated work with the grounding loop is necessary. Since it is difficult to make calculations and a diagram on your own, you can use the given values. But you need to take into account the soil on which the house is located.
