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Permissible resistance of the protective grounding loop. Ground resistance
Page 1
The resistance value of the grounding device on the 0-4 kV side should be 4 Ohms. This resistance must also be taken for the 6 kV side with common grounding.
The value of the resistance of the grounding device r3 compared to the resistance of the human body Kchsa is very small: according to the standards, it should not exceed 4 Ohms.
The resistance value of the grounding device of a mobile electrical installation must be checked during its construction, as well as during subsequent technical services. If, to reduce the resistance of artificial grounding conductors, natural grounding conductors are also used in an electrical installation, then their resistances must be measured separately. Only if it is not possible to separate artificial grounding conductors from natural ones is it possible to measure the total resistance.
The resistance value of the grounding device normalized by the PUE depends on the ground fault current, the installation voltage and the method of grounding the neutrals of transformers or generators of the network in question.
At the same time, the resistance value of the grounding device (R) should be no more than 4 ohms. As an exception, transformer substations with one transformer with a power of 100 kVA or less, the grounding device can have a resistance of no more than 10 ohms.
It is equivalent to limiting the resistance value of the grounding device and, consequently, the voltage relative to the ground to certain valid value. The Rules accept 4 ohms as the resistance value of the grounding device.
To obtain the resistance value of the grounding device required by the standards, radial grounding conductors are laid in addition to the contours.
As you can see, with this method the resistance value of the grounding device is not limited, and safety must be achieved by equalizing the potentials.
The first condition is, to a certain extent, satisfied by the requirement of the Rules that the resistance of the grounding device be no more than 4 ohms. This is also facilitated by the presence of repeated grounding of the neutral wire.
Artificial grounding conductors are used in cases where there are no natural grounding conductors near electrical installations to be grounded or when, after using natural grounding conductors, the resistance value of the grounding device does not satisfy the standards or design requirements.
In soils with higher resistivity, the natural conductivity of reinforced concrete foundations, supports and stepsons should not be taken into account, and the required table. P-5-14 the resistance value of the grounding device should be ensured only by the use of artificial ground electrodes.
The calculated resistance of the grounding device is determined. The resistance value of the grounding device is determined depending on the purpose and in all cases is regulated by the Electrical Installation Rules. The resistance of the grounding device in networks up to 1,000 V should not exceed 4 ohms, and for generators or transformers with a power of 100 kVA or less - 10 ohms.
The calculated resistance of the grounding device is determined. The resistance value of the grounding device is determined depending on the purpose and in all cases is regulated by the Electrical Installation Rules. The resistance of the grounding device in networks up to 1000 V should not exceed 4 ohms, and for generators or transformers with a power of 100 kVA or less - 10 ohms.
Ground resistance- this is the resistance of the soil (earth) to the spreading of electric current through it, entering through the ground electrodes.
As we know from the physics course, resistance is measured in Ohms and the lower it is, the better. The ideal option is a zero value, meaning the absence of any resistance at all.
Such an ideal does not exist in nature, therefore all electrical equipment and electronics are standardized by resistance values of 60, 30, 15, 10, 8, 4, 2, 1 and 0.5 Ohms.
When connecting local grounding to the neutral of a transformer/generator in a TN system, the total grounding resistance (local + all repeated + transformer/generator grounding) should be no more than 4 Ohms (PUE 1.7.101). This condition is met without any additional measures if the current source (transformer or generator) is properly grounded.
As for private houses with an electrical network of 220/380 Volts, the value of grounding resistance should not exceed 30 Ohms.
If a gas pipeline is connected to a private house, then the grounding resistance should be no more than 10 Ohms, since dangerous equipment is used.
The grounding used to connect lightning rods must have a resistance of no more than 10 Ohms.
For a current source (generator or transformer), the grounding resistance should be no more than 2, 4 and 8 Ohms, respectively, at linear voltages of 660, 380 and 220 V of a three-phase current source or 380, 220 and 127 V of a single-phase current source (PUE 1.7.101)
For reliable operation of gas arresters in devices for protecting overhead communication lines (for example, a local network based on a copper cable or a radio frequency cable), the grounding resistance to which they (the arresters) are connected must be no more than 2 Ohms. There are instances with a requirement of 4 ohms.
When connecting telecommunications equipment, the ground should usually have a resistance of no more than 2 or 4 ohms.
For a 110 kV substation, the resistance to current spreading should be no more than 0.5 Ohm (PUE 1.7.90).
The above grounding resistance standards are valid for normal soils with a specific electrical resistance of no more than 100 Ohm*m (for example, clay / loam).
If the soil has a higher electrical resistivity, then often (but not always) minimum values grounding resistance increases by 0.01 of the soil resistivity.
For example, with sandy soils with a resistivity of 500 Ohm*m, the minimum local grounding resistance of a house with the TN-C-S system increases 5 times - up to 150 Ohm (instead of 30 Ohm).
Grounding quality
Grounding resistance is the main qualitative indicator of the ground electrode and directly depends on:
Specific soil resistance;
- configuration of the ground electrode, in particular: the area of electrical contact of the ground electrodes with the ground.
Soil resistivity
The parameter determines the level of “electrical conductivity” of the earth as a conductor - how well the electric current coming from the ground electrode will flow in such an environment. The smaller this value is, the lower the grounding resistance will be.
Specific electrical resistivity of soil (Ohm*m) is a measured value that depends on the composition of the soil, the size and density of its particles adjacent to each other, its humidity and temperature, the concentration of soluble substances in it chemical substances(salts, acidic and alkaline residues).
Usually a table of approximate values “soil resistivity” is used, because its accurate measurement is possible only during special geological survey work.
Grounding Configuration
Grounding resistance directly depends on the area of electrical contact between the grounding electrodes and the ground, which should be as large as possible. The larger the surface area of the ground electrode, the lower the grounding resistance.
Most often, due to the least installation complexity, a vertical electrode in the form of a rod/pipe/angle is used as a grounding electrode.
To increase the contact area of the ground electrode with the ground:
The length (depth) of the electrode increases;
. several short electrodes connected together are used, placed at some distance from each other (
Elmashprom LLC produces ready-made grounding and lightning protection kits for station and linear structures of wired communication installations, radio relay stations, radio broadcasting nodes for wired broadcasting (WB), selective railway communication installations and antennas of collective television reception systems, which include: prefabricated lightning rods up to 25 meters high (for buildings and structures on brackets and free-standing), deep vertical grounding conductors, horizontal grounding conductors, clamps for connecting grounding conductors, holders for fastening leads of grounding conductors, holders for installing a potential equalization system, main grounding bars, flexible grounding conductors, welded grounding contacts, etc. Technical solutions and fastening units for designers in DWG.
RESISTANCE STANDARDS GOST 464-79
Moscow
STATE STANDARD OF THE USSR UNION
Date of introduction 01.01.80
This standard applies to (SKPT), for which stationary grounding devices are equipped, and establishes standards for the resistance of grounding devices that ensure the normal operation of the structures and installations listed above, as well as the safety of operating personnel.
The standard does not apply to grounding devices that are provided in special-purpose equipment.
The terms used in this standard and their definitions are given in the appendix.
1. GENERAL PROVISIONS
1.1. To worker-protective or protective grounding device Using grounding wires, the following should be connected in the shortest possible way:
one of the poles of the power supply installation;
neutral of transformers, output of a single-phase current source of a transformer substation or its own power plant that supplies equipment for communications enterprises, a radio relay station or a PV station;
metal parts of power, cabinet and switching equipment;
metal supporting equipotential surface of electronic telephone exchanges;
metal pipelines for water supply and central heating and other metal structures inside the building;
equipment and cable screens;
metal sheaths of cables, elements of protection circuits, lightning rods;
SKPT antennas subject to lightning protection in accordance with regulatory and technical documentation (hereinafter referred to as NTD).
The number of grounding wires and the procedure for connecting equipment and equipment to them are established in the technical documentation for equipment of a specific type.
(Changed edition, Amendment No. 2).
1.2. Telecommunications enterprises should be equipped protective grounding device, if there are no connecting lines and remote power supply circuits for equipment using ground as a wire electrical circuit.
Requirements to protective grounding and grounding- according to GOST 12.1.030.
(Changed edition, Amendment No. 1).
1.3. Telecommunications enterprises should be equipped one working and protective grounding device, if the “minus” of the remote power supply current source is grounded (in this case, the remote power supply circuits can be connected according to the “wire-ground” circuit) or the “plus” of the current source is grounded, but there are no remote power circuits according to the “wire-to-ground” circuit. In this case, the connecting lines can use the ground as the wire of the electrical circuit. The circuit of the working and protective grounding device in the presence of remote power circuits must have two independent inputs into the building (before the grounding panel).
Enterprises should have separate working and protective grounding devices, if there are remote power circuits according to the “wire-ground” circuit with grounding of the “plus” of the current source.
1.4. The neutral of transformers, the output of a single-phase current source of a transformer substation or its own power plant that supplies equipment for communications enterprises, a radio relay station or a PV station must be connected to the protective or working and protective grounding device. In this case, the grounding device for the above enterprise and for the transformer substation must be common if the distance between the enterprise and the transformer substation is less than 100 m.
Resistance of the common grounding device must comply with the resistance standards of grounding devices for each connected installation.
Resistance grounding device, to which the neutrals of generators or transformers or the output of a single-phase current source are connected, with a soil resistivity of up to 100 Ohm m there should not be more than, Ohm:
2 - installations with voltage 660/380 V;
4 - installations with voltage 380/220 V;
8 - installations with voltage 220/127 V.
If the soil resistivity r is more than 100 Ohm m, it is allowed to increase the resistance value of the grounding device by r/100 times, but no more than ten times, and also no more than the values indicated in the table. Table 1-Table 3, Table 5 and in paragraphs. Clause 2.1.5, Clause 2.4.5, Clause 2.7.2.
1.3, 1.4. (Changed edition, Amendment No. 2).
1.4a. The resistance of a protective or operational-protective grounding device must be ensured taking into account the use of natural grounding conductors (metal pipes laid underground, metal structures, reinforcement of buildings and their concrete foundations, and others, with the exception of pipelines of flammable and explosive mixtures, sewerage, central heating and domestic water supply located outside the building in which the equipment of the communications company or the PV station is located).
1.5. The design of artificial grounding devices or various circuits of a grounding device, the brand and cross-section of connecting conductors from the grounding device to the grounding panel, a list of equipment, equipment and protective elements connected to the grounding device, methods of connecting wires and their number, methods for measuring the resistance of grounding devices and soil resistivity installed in the technical documentation for a specific type of equipment.
(Changed edition, Amendment No. 2).
1.6. The distance between individual non-insulated parts of different grounding devices (between working, protective, measuring, etc.) in the area before entering the building should not be less than 20 m.
1.7. The resistance of the measuring grounding device should not be more than 100 Ohms in soils with a resistivity of up to 100 Ohm m and 200 Ohm in soils with a resistivity of more than 100 Ohm m.
1.8. Resistance of linear protective grounding devices for communication lines and wire hanging in areas of dangerous influence of electrified power lines railways, as well as under the influence of radio stations and impulse impacts (excluding lightning), determined by calculation in accordance with the requirements of the normative and technical documentation, should not exceed the values established by this standard.
(Changed edition, Amendment No. 2).
1.9. When operating grounding devices, their resistance should be checked periodically:
twice a year - in summer (during the period of greatest drying of the soil) and in winter (during the period of greatest freezing of the soil) - at long-distance, urban and rural telephone exchanges, telegraph stations, telegraph broadcasting, terminal and subscriber points;
once a year - in the summer (during the period of greatest drying out of the soil) - at radio relay stations, at stations and substations of radio broadcasting nodes;
once a year - before the start of the thunderstorm period (April - May) - in unattended reinforcement points (UPP) and regeneration points (RP) of long-distance, urban and rural communications; for containers of transmission system equipment (ICM-30, etc.);
once a year - before the start of a thunderstorm - on cable and overhead communication lines and radio broadcast networks, at cable supports and supports on which protective equipment is installed, at subscriber points of telephone and radio broadcast networks, at step-down transformers of payphone booths;
at least once a year (before the start of a thunderstorm) - for antennas of collective television reception systems.
2. RESISTANCE STANDARDS
2.1. Resistance standards for grounding devices for long-distance telephone exchanges and terminal points of selective railway communications
2.1.1. Intercity telephone exchanges (MTS), terminal points of selective railway communications, line equipment shops (LAS) and intermediate amplification points with power supply installations must be equipped with a protective or operational-protective grounding device and two measuring grounding devices. When equipping working and protective grounding devices in accordance with clause 1.3, one measuring grounding device is installed, which must be connected in parallel to the protective grounding device.
In operating condition, measuring grounding devices must be connected on the grounding panel parallel to the protective or operational-protective grounding devices.
2.1.2. Resistance of protective grounding devices of MTS, linear hardware shops and intermediate amplification points, as well as terminal points of selective railway communication with power supply installations that do not use the ground as a current conductor in circuits of connecting lines or remote power supply of unattended amplification and regeneration points using the “wire- earth”, should be no more than the values specified in clause 1.4.
2.1.3. The resistance of protective grounding devices at intermediate points that do not have power supply installations should be no more than 10 Ohms for soils with a resistivity of up to 100 Ohm m and no more than 30 Ohm for soils with a resistivity of more than 100 Ohm m.
2.1.4. The resistance of working or working-protective grounding devices of MTS, using the ground as one of the wires of connecting lines of any type (custom, service from MTS and ATS, transit service lines, etc.), or in remote power supply (DP) circuits should be no more values indicated in table. Table 1, and operational and protective grounding devices must also meet the requirements of clause 1.4.
Table 1
(Changed edition, Amendment No. 2).
2.1.5. Resistance of working or working-protective grounding devices of linear equipment shops, support points; serviced amplifier points feeding remotely unattended or regeneration points using the “wire-to-ground” circuit must be determined based on the voltage drop on the grounding device from the remote supply current of no more than 12 V. However, the resistance of working or operational-protective grounding devices should not be more than the values specified in clause 1.4.
2.1.6. Serviced amplification points of underwater cable lines that remotely feed underwater amplifiers using the wire-to-ground circuit must be equipped with two separate working grounding devices (main and backup), which in working order must be connected to the grounding panel. The resistance of the main working grounding device should be no more than 5 Ohms and the backup one - no more than 10 Ohms.
(Introduced additionally, Amendment No. 2).
2.2. Resistance standards of grounding devices for unattended amplification points of long-distance communication and intermediate points of selective railway communication
2.2.1. Unattended amplification points (NUA), fed remotely using a wire-to-ground circuit, in which the remote power supply circuit ends, must be equipped with three separate grounding devices - working, protective and line-protective.
Magnesium protectors used to protect metal NUP tanks from soil corrosion may be used as a protective grounding device.
In cases where it is not necessary to protect metal tanks of the LUP from soil corrosion, as well as when using non-metallic bodies, the LUP must be equipped with a working and integrated protective grounding device.
2.2.2. Unattended amplification points (NUP) and regeneration points (RP), fed remotely according to the “wire-to-wire” circuit, as well as UUP, powered according to the “wire-to-ground” circuit, in which the remote power supply circuit does not end, must be equipped with two separate grounding connections. devices - protective and linear protective.
Magnesium protectors used to protect metal tanks NUP or RP from soil corrosion can be used as grounding conductors for a protective grounding device.
In cases where protection of metal tanks of the LUP or RP from corrosion is not required, as well as when using non-metallic bodies of the LUP or RP, a combined protective grounding device must be equipped.
2.2.3. The resistance of the working grounding device for LUPs powered by a wire-to-ground circuit should be no more than 10 Ohms for soils with a resistivity of up to 100 Ohm m and no more than 30 Ohm for soils with a resistivity of more than 100 Ohm m. In this case, the voltage drop from remote power currents across the resistance of the grounding device should be no more than 12 V for soils with a resistivity of up to 100 Ohm m and no more than 36 V for soils with a resistivity of more than 100 Ohm m.
2.2.4. The resistance of protective grounding devices for LUP or RP powered according to the “wire-to-ground” and “wire-to-wire” circuits should be no more than 10 Ohms for soils with a resistivity of up to 100 Ohm m and no more than 30 Ohms for soils with a specific resistance resistance more than 100 Ohm m.
2.2.5. The resistance of linear protective grounding devices for cable sheaths equipped at the NUP or RP, when protecting cables from lightning strikes, should be no more than, Ohm:
10 - for soils with resistivity up to 100 Ohm m inclusive;
20 - for soils with a resistivity of St. 100 to 500 Ohm m inclusive;
30 - for soils with a resistivity of St. 500 to 1000 Ohm m inclusive;
50 - for soils with a resistivity of St. 1000 Ohm m.
(Changed edition, Amendment No. 2).
2.2.6. Intermediate points of selective railway communication must be equipped with one protective grounding device, the resistance of which must not exceed the values specified in Table. Table 2.
table 2
2.3. Resistance standards for grounding devices for telegraph stations and telegraph broadcast terminals and subscriber points.
2.3.1. Telegraph stations, broadcasting, terminal and subscriber points operating on two-wire circuits, located in a separate building (not combined with MTS, automatic telephone exchanges and other enterprises) and not using “ground” as an electrical circuit wire, must be equipped with a protective and two measuring grounding devices. In operating condition, all grounding devices must be connected in parallel on the grounding panel. Telegraph stations, broadcast terminals and subscriber points combined with other enterprises (MTS, ATS) must include grounding wires to a common protective grounding device.
For telegraph stations where up to five telegraph devices are installed, it is allowed to use temporary measuring grounding devices.
2.3.2. The resistance of the protective grounding device of telegraph stations with power supply installations should not exceed the values specified in clause 1.4.
Broadcasting, terminal and subscriber points that do not have power supply installations must be equipped with a protective grounding device with a resistance of no more than 10 Ohms for soil resistivities of up to 100 Ohm m and 20 Ohms for soils with a resistivity of more than 100 Ohm m.
2.3.3. Telegraph stations and telegraph broadcasting points operating on single-wire circuits must be equipped with a working-protective and two measuring grounding devices. For telegraph stations where up to five telegraph devices are installed, it is allowed to use temporary measuring grounding devices.
The resistance of the working and protective grounding device, depending on the number of single-wire telegraph circuits introduced into the station (see GOST 5238, drawing 26-31), should be no more than the values indicated in the table. Table 3.
Table 3
2.4. Resistance standards for grounding devices for city telephone exchanges and local railway communication stations
2.4.1. Telephone exchanges with a central battery (automatic telephone exchanges and manual telephone exchanges - RTS) must be equipped with three separate grounding devices - a protective or operational-protective one and two measuring ones.
In operating condition, all three grounding devices must be connected in parallel on the grounding panel and are disconnected only to measure the resistance of the protective or operational-protective grounding device.
2.4.2. Telephone exchanges that have connecting lines and do not use the ground as a current conductor (for example, connecting lines equipped with inductive sets of the RSL type) should be equipped with protective grounding devices (clause 1.2), the resistance of which should not exceed the values specified in clause. 1.4.
Telephone exchanges that do not have supply transformer substations receiving power from electrical networks voltage 380/220/127 V, must be equipped with a protective grounding device with a resistance not exceeding the values specified in table. 4.
Table 4
(Changed edition, Amendment No. 2).
2.4.3. Telephone exchanges that have connecting lines using the ground as current conductors (according to clause 1.3) must be equipped with operational and protective grounding devices, the resistance of which should not exceed the values indicated in the table. 5.
Table 5
Note. In cases where the connecting lines at the station are equipped with inductive and battery (using the ground as a current conductor) sets of the RSL type, the resistance value of the working and protective grounding is selected depending on the number of battery (polar) sets of the RSL type.
2.4.4. Unattended booster and regeneration points powered remotely using the “wire-to-wire” and “wire-to-ground” circuits must be equipped with one protective grounding device, the resistance value of which must correspond to that given in clause 2.2.4.
2.4.5. The resistance of the protective or operational-protective grounding device of electronic telephone exchanges must be no more than 4 Ohms, and also comply with the requirements of paragraphs. 2.4.2 and 2.4.3.
(Introduced additionally, Amendment No. 2).
2.5. Resistance standards for grounding devices of rural telephone exchanges (STS)
2.5.1. Rural telephone exchanges with a central battery (RTS and ATS) must be equipped with three separate grounding devices in accordance with paragraphs. 2.4.1-2.4.3.
2.5.2. Telephone exchanges with a capacity of up to 3000 numbers can be equipped with one protective or operational-protective grounding device, and temporary grounding devices can be used as measuring grounding devices.
(Changed edition, Amendment No. 2).
2.5.3. For compaction equipment of rural automatic telephone exchanges and radio telephone exchanges in the case of using the NUP “wire-to-wire” power supply system, one integrated protective grounding device should be used. In this case, unattended amplification points must be equipped with protective grounding devices with a resistance not exceeding the values specified in paragraphs. 2.1.2 and 2.1.3.
2.5.4. Maintenance-free amplification points powered remotely using a wire-to-ground circuit should be equipped with two separate grounding devices: a working one and a line-protective one. The resistance of working and linear protective grounding devices should be no more than the values specified in paragraphs. 2.2.3 and 2.2.5.
2.6. Grounding resistance standards for telephone exchanges with a local battery (MB)
2.6.1. Telephone exchanges of the MB system operating on two-wire circuits must be equipped with three separate grounding devices - a protective one and two measuring ones. In operation, these three grounding devices must be connected in parallel on the grounding panel. When the station capacity is up to 200 numbers, it is allowed not to equip stationary measuring grounding devices, and when measuring the protective grounding device, use temporary grounding devices.
2.6.2. The resistance of the protective grounding device of MB stations operating on two-wire circuits should be no more than the values indicated in table. 2.
2.7. Resistance standards for grounding devices for stations and PV
2.7.1. Stations and PV should be equipped with one protective or operational-protective grounding device. For control measurements of the resistance of the protective and working-protective grounding device, it is allowed to equip two stationary measuring grounding connections or use temporary grounding devices.
2.7.2. The resistance of the protective or operational-protective grounding device for PV stations should be no more than 10 Ohms.
2.7-2.7.2. (Changed edition, Amendment No. 2).
2.7.3. PV stations and transformer substations feeding them, geographically close to one another (clause 1.4), should be equipped with a common protective or operational-protective grounding device with a resistance of no more than the values specified in clause 1.4.
(Introduced additionally, Amendment No. 2).
2.8. Resistance standards of grounding devices for combined installations of wired communication and PV
(Changed edition, Amendment No. 2).
2.8.1. Stationary installations of wired communications for various purposes, located in the same or adjacent buildings and powered by one transformer substation: intercity, city, railway selective communications and others, as well as stations and substations of radio broadcasting nodes, should be equipped with one common protective or operational-protective grounding device . In this case, the resistance of the connecting wires from the grounding device should be taken into account.
2.8.2. The resistance value of the common grounding device must comply with the standards for each connected installation.
2.8.3. Not allowed in unattended amplification points powered remotely DC, combine a common protective grounding device with the working one.
2.9. Resistance standards for protective grounding devices for long-distance communication lines
2.9.1. Resistance values of grounding devices for:
cascade protection spark gaps of types IR-7, IR-10, IR-15 and IR-20;
spark gaps IR-0.2 or IR-0.3 - when installed on supports adjacent to the cable support or station;
spark gaps installed on overhead line wires to protect underground communication cables from lightning strikes;
lightning rods installed on overhead line supports;
rope and metal sheaths of cables suspended on overhead line supports should be no more than the values specified in table. 6.
Table 6
(Changed edition, Amendment No. 2).
2.9.2. The resistance of protective grounding devices for input, cable and other supports of intercity communication lines and selective railway communications, on which, in accordance with the requirements of GOST 5238, it is required to turn on spark gaps of types IR-0.2 and IR-0.3 or gas-filled gaps, must not be more than the values indicated in the table. 7.
Table 7
2.9.3. The resistance of protective grounding devices for arresters of type IR-0.3, included to protect the blocking coils in the third circuits (see GOST 5238, Fig. 9), must be no more than the values indicated in the table. 6.
2.9.4. The resistance of linear protective grounding devices for metal cable sheaths, protective wires (cables) or busbars laid in the ground when protecting the cable from lightning strikes should be no more than the values specified in table. 8.
Table 8
Note. The number of linear protective grounding devices, their placement on cable lines and the method of connecting metal shells, cables and cable screens is established in the regulatory and technical documentation.
2.10. Resistance standards of protective grounding devices for lines of urban and rural telephone networks and local railway communication networks
2.10.1. Resistance of grounding devices for spark gaps of types IR-0.2; IR-0.3; IR-7; IR-10 and IR-15, connected according to diagrams. 19, 22-24 GOST 5238, should be no more than the values specified in table. 6.
2.10.2. Resistance of grounding devices for gas-filled arresters of types R-84 and R-35 installed in cable boxes at the junctions of overhead lines of GTS, STS and railway communication networks with cable lines (see GOST 5238, drawings 15-17; 21a), and also for installation points of blockers (see GOST 5238, Fig. 24), there should be no more than the values specified in the table. 9.
Table 9
Soil resistivity, Ohm m Up to 100 incl. St. 100 to 300 incl. St. 300 to 500 inclusive. Over 500
Resistance of grounding devices, Ohm, no more than 10 15 20 25
(Changed edition, Amendment No. 2).
2.10.3. The resistance of grounding devices for subscriber points (see GOST 5238, drawings 16, 17, 21), for step-down transformers of payphone booths and lightning rods installed on overhead line supports should be no more than the values specified in table. 10.
Table 10
Soil resistivity, Ohm m Up to 100 incl. St. 100 to 300 incl. St. 300 to 500 inclusive. St. 500 to 1000 inclusive. St. 1000
Grounding device resistance, Ohm, no more than 30 45 55 65 75
2.10.4. Resistance of grounding devices for the metal sheath of the cable, cable screen with non-metallic sheaths when suspended on the supports of pole and rack lines, rope used when hanging cables, as well as for telephone housings distribution cabinets type ShR or ShRP into which the cables are included must be no more than the values specified in table. 6.
2.10.5. The resistance of linear protective grounding devices when protecting GTS and STS cables laid in the ground from lightning strikes, as well as for the housing of telephone distribution cabinets of the ShR and ShRP types in which the cables are included, should be no more than the values specified in Table. 8.
2.11. Resistance standards for protective grounding devices on power supply lines
2.10.4, 2.10.5, 2.11. (Changed edition, Amendment No. 2).
2.11.1. Resistance of linear protective grounding devices for spark gaps of types IR-0.5 and IR-7.0 (see GOST 14857, drawings 1, 2), as well as for spark gaps of types IR-0.3 and IR-7.0 (see GOST 14857, drawings 3, 5, 6) should be no more than the values indicated in the table. 6.
2.11.2. Resistance of linear protective grounding devices for grounding the metal sheath and screen of cables laid in channels cable duct and collectors (at the beginning and end of the cable), should be no more than the values indicated in the table. 8.
2.11.3. The resistance of linear protective grounding devices for lightning rods installed on the supports of overhead power lines must be no more than the values specified in table. 10.
(Changed edition, Amendment No. 2).
2.12. Resistance standards for grounding devices for radio relay stations
2.12.1. Radio relay stations, including those with compaction equipment, must be equipped with one protective grounding device. To monitor the resistance of the protective grounding device, it is allowed to equip two stationary measuring grounding devices or use temporary grounding devices. In operating condition, protective and measuring stationary grounding devices must be connected in parallel on the grounding board.
2.12.2. The resistance of the protective grounding device must be no more than the values specified in clause 1.4.
2.13. Resistance standards for grounding devices for antennas of a collective television reception system
2.13.1. To protect SKIT antennas from dangerous voltages and currents arising from lightning discharges, a protective grounding device must be equipped. To monitor the resistance of the protective grounding device, it is allowed to use temporary measuring grounding devices.
2.13.2. It is allowed to connect lightning rods from two or more SKPT antennas located on the same building to one grounding device.
2.13.3. The design of the grounding device, as well as the lightning rod connecting the SKPT antenna to the grounding device, and the method of connecting them are established in the regulatory and technical documentation.
2.13.4. The resistance of the grounding device for SKPT antennas should be no more than the values indicated in the table. 6.
2.13.5. If there is a grounding device for the building on which the SKPT antennas are located (when protecting buildings from lightning strikes or to protect telephone communication and radio broadcasting equipment), it is allowed to connect lightning rods from the SKPT antennas to the existing grounding device. The resistance of the grounding device must be no more than the values indicated in the table. 6.
APPLICATION
Information
TERMS USED IN THIS STANDARD AND THEIR DEFINITIONS
Term Definition
Grounding for wired communication installations, radio relay stations, MF radio broadcasting units, etc. Intentional electrical connection of plant equipment or apparatus to a grounding device
Grounding conductor A metal conductor or group of conductors of any shape (pipe, angle, wire, etc.) in direct contact with the ground (soil)
Grounding conductor A metal conductor connecting the grounded equipment or equipment to the grounding conductor
Grounding device A set of grounding conductors and grounding conductors
Resistance of the grounding device or resistance to current spreading The total electrical resistance of the grounding conductors and the grounding conductor relative to the ground, expressed in ohms. The resistance of the grounding conductor relative to the ground is defined as the ratio of the voltage of the grounding conductor relative to the ground to the current passing through the grounding conductor into the ground
Soil resistivity The electrical resistance exerted by soil with a volume of 1 m3 when current passes from one side of the soil to the opposite. The soil resistivity, denoted by r and expressed in ohms per meter, should be measured taking into account seasonal variations, taking the most unfavorable value as the calculated value
Working grounding device A device designed to connect wired communication equipment and radio devices (PV substations, radio relay stations) to the ground for the purpose of using the ground as one of the wires of the electrical circuit
Protective grounding device A device designed to connect to the ground the neutral wires of the windings of power transformer substations, lightning rods, arresters, equipment screens and in-station installation wires, metal shells and armored covers of cables, metal tanks, unattended amplification points (NUP), metal parts of power equipment of wired installations communications and power supply stations, installations for maintaining cables under pressure and other equipment that are not normally energized, but may become energized if the insulation of live wires is damaged. Protective grounding devices ensure that the potential of metal parts of equipment is equalized with the ground potential and thereby protect operating personnel and equipment from the occurrence of dangerous potential differences with respect to the ground.
Linear protective grounding device A device that provides grounding of metal cable sheaths and armored covers along the cable route and at stations (NUP) where cable lines are suitable, as well as on overhead lines for grounding lightning rods, cables and metal cable sheaths, etc. In some cases, it is possible to combine protective and linear protective grounding devices. Such a grounding device is called a combined protective
Measuring grounding device An auxiliary device designed for control measurements of the resistance of working, protective and working-protective grounding devices. The resistance of the working and protective grounding devices should be measured, as a rule, from the grounding panel at the station, including the grounding conductor towards the grounding conductor. The resistance of grounding devices on overhead and cable lines is measured directly on the line
Working and protective grounding device A device that simultaneously serves as both a working and a protective grounding device. The resistance of the working and protective grounding device must be no more than the minimum value provided for the working and protective grounding devices.
(Changed edition, Amendment No. 2).
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the USSR Ministry of Communications
DEVELOPERS:
A.K. Slanov (topic leader); V.V. Zakharov
2. APPROVED AND ENTERED INTO EFFECT by the Resolution State Committee USSR according to standards dated January 29, 1979 No. 304
3. The standard is unified with BDS 4722-70
4. Inspection frequency - 5 years
5. INSTEAD GOST 464-68
6. REFERENCE REGULATIVE AND TECHNICAL DOCUMENTS
7. The validity period was lifted according to Protocol No. 4-93 of the Interstate Council for Standardization, Metrology and Certification (IUS 4-94)
8. REISSUE (October 1997) with Amendments No. 1, 2, approved in December 1983, June 1989 (IUS 4-84, 10-89)
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Also, the circuit resistance to pulse currents is less than to currents with a frequency of 50 Hz, but for a deep modular memory it’s the opposite!
You also need to know that the protective grounding of the house and equalization systems, potential equalization in the house when using TN systems, one of the varieties of which is the TN-C-S system, do not protect on the street when using electrical appliances of protection class 1, these are those with protective contacts on the plug or a grounding terminal on the housing in case of a power failure.
GOST R 50571.3-94 413.1.3.9 said:
When a residual current protective device is used to automatically disconnect a circuit outside the range of the main equipotential bonding system, the exposed conductive parts shall not be connected to the TN system network, but the protective conductors shall be connected to an earthing conductor having a resistance sufficient to operate the device. A circuit protected in this way may be considered a CT system network (see 413.1.4).
NOTE: Outside the range of the main equipotential bonding system, other protective measures may be used:
- power supply through a separating transformer;
- use of additional insulation (see 413.2)
The maximum consumption will be up to 10 kW. What cross section should I pull the wire from the metal plate that will be on the foundation to the shield?
Power has nothing to do with it at all. The cross-section must be at least 10 mm2 for copper or 16 mm2 for aluminum.
Why dig so much, not to mention the fact that unnecessary soil will be loosened, which will have a worse effect on the resistance of the charger. Everything is done much easier.
Instead of the notorious triangle hammered into the heads of the inexperienced, it is better to drive these same pins with the same distance in a straight line along the wall of the house; at least the resistance of such a charger will be less due to the better utilization rate of the pin. Also, such a design will be part of the grounding loop of the house, which will provide at least primitive equalization, alignment of the conductive parts of the house. In the future, in parts or all at once, it will be possible to make a full-fledged grounding loop for the house.
Welding areas and exits to the surface from a depth of 30 centimeters to a height of 30 centimeters above the surface should be thoroughly cleaned and treated with an anti-corrosion coating. The backfilled soil must be homogeneous, without stones and debris. At a minimum, the first soil to be filled up to 20 centimeters above the grounding device must be compacted.
It's called a device for measuring grounding resistance, there are many different models, but it's a bit expensive to buy for a one-time use.
It is easier to drive in a corner that needs to be made sharp with a grinder. The pipe is flattened on one side to make it easier to drive in; before flattening, it is also better to cut it at an angle with a grinder.
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B. Electrical safety Resistance of grounding devices (PUE-76, GOST 12.1.030-81)
Protective grounding ensures, in systems with an isolated transformer zero, that the current is discharged into the ground along the line of least resistance (compared to the resistance of the human body) through a metal conductor, firmly and tightly bolted to the body of the equipment, fence. This conductor is connected to the grounding line, deeply grounded in the ground with special grounding conductors (pipes, plates). It is necessary to check the serviceability of grounding at workplaces more often in order to promptly detect breaks and violations at connection points. Once a year, a mandatory check of the grounding resistance with equipment is carried out. In networks with voltages up to 1000 V, the resistance of the grounding mouths -
Inspection of the above-ground part of grounding devices electrical installations should be carried out simultaneously with the inspection of electrical equipment, but at least once a year. It is necessary to measure the resistance of grounding devices and check the presence of a grounding circuit with selective opening of individual elements of the grounding device at least once every 3 years, as well as after relocating the equipment.
The resistance of grounding devices should be measured during periods of lowest conductivity: in summer - when the soil is most dry, in winter - when the soil is most frozen.
In electrical installations with high ground fault currents, the resistance of grounding devices at any time of the year should be no more than 0.5 ohms.
The resistance of the grounding device used to ground equipment with voltages over 1000 V should not be more than 10 ohms, and with large ground fault currents (over 500 A), the resistance of the grounding devices should be no more than 0.5 ohms. .
According to the rules for electrical installations, protective grounding is standardized by the value of its resistance. The highest resistance of grounding devices in installations with voltages up to 1000 V depends on the power of the current source (generator or transformer). If the power of the current source is less than 100 kVA, then the grounding resistance is allowed to be 10 Ohms; when the power of the current source is more than 100 kVA, the grounding resistance should be no more than 4 Ohms. In electrical installations with voltages above 1000 V with high ground fault currents (more than 500 A), the ground-gel resistance should not exceed 0.5 Ohm. In installations with voltages above 1000 V with low ground fault currents, the resistance of the ground electrode is determined by the ratio 250//3; if the grounding device is simultaneously used for electrical installations with voltages up to 1000 V, then the resistance of the ground electrode should not exceed 125//3, but should not be more than 10 Ohms (or 4 Ohms if it is required for installations up to 1000V). Here /z is the ground fault current.
The resistance of grounding devices in explosive premises and outdoor installations should be measured only with explosion-proof instruments designed for the corresponding explosive environments. As a rule, the resistance to current spreading is
With a contour (distributed) grounding electrode, when the resistance of the grounding conductors is usually small, the resistance of the grounding device K3.у can be considered equal to R3- If the grounding electrode is remote, then due to its distance from the equipment being grounded, the resistance of the grounding conductor may turn out to be significant and should be taken into account when calculating R- , and D3,y In this case, the total resistance of the grounding device, Ohm,
Repeated grounding of the neutral wire must be carried out at the ends of branches of overhead lines with a length of more than 200 m and in the middle of the line and branches with a length of 500 m. The resistance of the grounding devices to which the neutrals of transformers or the terminals of a single-phase current source are connected should be no more than 2, at any time of the year. 4 and 8 Ohms, respectively, at linear voltages of 66U, 380 and 220V of a three-phase current source or 380, 220 and 127V of a single-phase current source.
To avoid the occurrence of spark charges of static electricity, metal and electrically conductive parts of process equipment must be grounded. The resistance of grounding devices should not exceed 100 Ohms.
1 - transformer; 2 - network; 3 - pantograph body; 4 - electric motor winding; 5 - ground electrode; 6 - neutral grounding resistance (conditional)
/ - transformer; 2 - network; 3 - fuse; 4 - electric motor winding; 5 - electric motor housing; 6 - neutralizing conductor; 7 - neutral protective conductor; 8 - neutral grounding resistance
In the presence of grounding, due to the flow of current to the ground, the touch voltage decreases and, therefore, the current passing through a person is less than in an ungrounded installation. To keep the voltage on the grounded equipment body to a minimum, the grounding resistance is limited. In 380/220 V installations it should be no more than 4 ohms, in 220/127 V installations it should be no more than 8 ohms. If the power source power does not exceed 100 kVA, the grounding resistance can be within 10 ohms.
grounding and phase insulation resistance. With good insulation, gf is equal to tens of kOhms, so the current /z will be small. So, with a phase voltage of 220 V g, = 4 Ohm, /F = 40000 Ohm, L = 220 / (4 + +40 000) = 0.0055 A. The potential drop will be distributed as follows: on grounding - between the housing and the base U3 = /Eg3 = =0.0055-4 = 0.022 V, between base and phases (potential drop across insulation
In a network with a grounded neutral (see Fig. 7.5, 6) 13 = U$/(r3 + /b) = =220/(4 + 10) = 15.7 A(/b is the electrical resistance of the neutral grounding, usually not exceeding 10 Ohms), and the touch voltage?/pr = U3 = 15.7 4 = 62.8 V, which poses a danger to humans. As can be seen, in this case 13 increases significantly as r decreases, and the grounding efficiency is low. The lower the electrical resistance of the installation body grounding compared to the neutral grounding resistance, the higher the protective properties of the grounding will be.
According to the PUE, the electrical resistance of protective grounding at any time of the year should not exceed: 4 Ohms in installations with voltages up to 1000 V with an insulated neutral (when the power of the current source - generator or transformer - is less than 100 kW, no more than 10 Ohms is allowed). In installations with a grounded neutral, the grounding resistance is determined by calculation based on the requirements for permissible touch voltage, but not more than 0.5 Ohm.
Installations for applying polymer powder paints must be equipped with local exhaust ventilation interlocked with the powder supply system, as well as devices that prevent sparking when the sprayer approaches the product being painted due to discharges of static electricity. To eliminate spark discharges of static electricity, it is necessary to ground the product suspension. Grounding resistance should not exceed 1C6 Ohm; it is subject to control at least once per shift.
During a routine inspection of a compressor unit, you should check: the compressor and its engine; serviceability of the lubrication system; safety valves, pressure gauges; degree of tightening of bolted connections; electrical insulation resistance and grounding resistance; operation of automatic devices; condition of check valves. Routine inspections should be carried out according to a schedule drawn up taking into account the manufacturer’s recommendations.
neutral grounding resistance (for networks with a grounded neutral) (Fig. 39, biv). If the value of the network insulation resistance is large, then practically the current passing through a person is very small, and in this case, a network with a linear network voltage U of up to 1000 V is relatively safe with a single-phase connection.
Grounding conductors connect electrical equipment housings to the ground electrode. Bridge cranes, except those operating in explosive environments, are grounded through the crane runway. Grounding resistance in networks with operating voltages up to 1000 V, which include electric taps, should not exceed 4 Ohms along with the circuit resistance.
When checking the grounding, keep in mind that the grounding resistance should not exceed 4 ohms. The witness must familiarize himself with the results of the resistance measurement.
