CN113486290B - Security check calculation method for active low-voltage distribution network grounding device - Google Patents
Security check calculation method for active low-voltage distribution network grounding device Download PDFInfo
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Abstract
The invention relates to a safety check calculation method of an active low-voltage distribution network grounding device, which comprises the following steps: s1, selecting a sectional area of a grounding wire; s2, checking the sectional area of the grounding wire according to the single-phase residual voltage and the three-phase residual voltage of the working point, and if the single-phase residual voltage and the three-phase residual voltage are lower than the safety voltage of a human body, checking the sectional area of the selected grounding wire safely; otherwise, the sectional area of the grounding wire is selected again; the single-phase residual voltage is obtained by superposing the pressure drop of the single-phase grounding current on the grounding device and the ground potential difference between the working point and the grounding device, and the ground potential difference is obtained by analyzing double-layer soil through a mirror image method. Based on the current situation of the active power distribution network, the invention provides a checking method of the grounding device, and maintenance personnel can flexibly find the optimal and safest grounding protection measures according to the method. Meanwhile, when the sectional area of the grounding wire is checked, the single-phase residual voltage and the three-phase residual voltage of the working point are considered, and the safety of maintenance personnel is effectively ensured.
Description
Technical Field
The invention relates to a safety check calculation method of an active low-voltage distribution network grounding device, and belongs to the field of electric automation.
Background
The distribution network is an intermediate bridge connecting a large power grid with power users, and the reliable and economic operation of the distribution network has an important influence on the stability of the whole power system. The active power distribution network refers to a power distribution network with a large amount of access to distributed power sources and power flowing bidirectionally, and is also called an active power distribution network. At present, a passive power distribution network gradually transits to an active power distribution network, and the grid structure of the power distribution network is changed continuously. And the active power distribution network is subjected to power outage maintenance regularly. Before overhauling, an maintainer needs to additionally install a grounding device on one side of a working point (namely an overhauling point) so as to ensure the safety of the maintainer. The grounding device refers to a general term of a grounding electrode buried underground and a connecting wire from the grounding electrode to equipment, and comprises a grounding wire, a grounding electrode, a wire clamp and other components.
However, the existing checking method of the grounding device is not adjusted along with the change of the grid structure of the power distribution network, and the withstand current of the grounding wire is checked according to the non-fusing principle only through an Audi-dak formula, so that the sectional area of the grounding wire is selected, and a certain potential safety hazard exists. Therefore, a method for checking and calculating a grounding device suitable for an active power distribution network is needed.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a safety check calculation method of an active low-voltage power distribution network grounding device, and provides a checking method of the grounding device based on the current situation of the active power distribution network, so that maintenance personnel can flexibly find the optimal and safest grounding protection measures according to the method. The invention is suitable for various active power distribution networks, in particular for active low-voltage power distribution networks with a large number of distributed power sources connected to the low-voltage side.
The technical scheme of the invention is as follows:
a security check calculation method of an active low-voltage distribution network grounding device comprises the following steps:
s1, selecting a sectional area of a grounding wire;
s2, checking the sectional area of the grounding wire according to the single-phase residual voltage and the three-phase residual voltage of the working point, and if the single-phase residual voltage and the three-phase residual voltage are lower than the safety voltage of a human body, checking the sectional area of the selected grounding wire safely; otherwise, the sectional area of the grounding wire is selected again;
the single-phase residual voltage is obtained by superposing the pressure drop of the single-phase grounding current on the grounding device and the ground potential difference between the working point and the grounding device, and the ground potential difference is obtained by analyzing double-layer soil by a mirror image method.
Further, the method further comprises the following steps: and determining the using measure of the grounding wire according to the safety checking result of the sectional area of the grounding wire.
Further, the step S1 specifically includes:
s11, acquiring parameters and a topological structure of an active low-voltage power distribution network;
s12, calculating to obtain a functional relation between the withstand current of the grounding wire and the protection action time of the circuit switch for the grounding wires with different sectional areas based on an Audi dak formula;
s13, calculating the maximum short-circuit current of the working point according to the topological structure of the active low-voltage power distribution network;
s14, selecting a grounding wire sectional area meeting a condition according to the switch protection action time of the line where the working point is located by utilizing the functional relation; the condition is that the ground line withstand current is greater than the maximum short circuit current.
Further, the audi-dak formula in the step S12 is:
wherein S is the sectional area of the grounding wire; i k A withstand current for the ground line; t is the switch protection action time of the line; c is the thermal stability coefficient of the ground wire material.
Further, the step S13 specifically includes:
calculating three-phase short-circuit current provided by each distributed power supply to a working point in the active low-voltage distribution network; calculating three-phase short-circuit current provided by a large power grid connected with an active low-voltage power distribution network to a working point;
if the grounding wire is positioned at the upstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the maximum value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point; if the grounding wire is positioned at the downstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the superposition value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point.
Further, the calculation formula of the three-phase residual voltage in the step S2 is as follows:
U res3 ＝kU G +I DG (R x +R t )
in U G The power supply voltage of the large power grid; k is a partial pressure coefficient, k is less than 1; i DG A sum of three-phase short-circuit currents provided to the operating points for each distributed power supply; r is R x A cable resistor is short-circuited for a grounding wire; r is R t Is the contact resistance of the wire clip.
Further, the calculation formula of the single-phase residual voltage in the step S2 is as follows:
wherein I is k Representing a single phase ground current at the ground line; k represents the reflection coefficient of the soil,
ρ 1 representing the resistivity of the upper soil, ρ 2 Representing the resistivity of the underlying soil; s represents the thickness of the upper soil; z is Z g1 Representing the ground resistance of the ground wire; z is Z g Representing the sum of the grounding resistance of the distribution transformer and the grounding resistance of the grounding wire; r is R N Represents the neutral line resistance; r is R x Representing the ground wire short circuit cable resistance; r is R t Representing the contact resistance of the wire clip; x represents the distance between the operating point and the ground line.
The invention has the following beneficial effects:
1. based on the current situation of the active power distribution network, the invention provides a checking method of the grounding device, and a maintainer can flexibly find the optimal and safest grounding protection measures (namely the sectional area of the grounding wire and the using measure of the grounding wire) according to the method. Meanwhile, when the sectional area of the grounding wire is checked, the single-phase residual voltage and the three-phase residual voltage of the working point are considered, and the safety of maintenance personnel is effectively ensured.
2. According to the invention, the soil resistivity is considered in a layering manner, the actual soil condition is more fit, and the single-phase residual voltage can be more accurately obtained by considering the shunting effect of the low-voltage side zero line, so that the actual requirement on the grounding resistance is reduced, the cost of the grounding device is reduced, and the economic benefit of a power grid is improved.
3. The bidirectional tide in the active power distribution network is considered, the maximum value of the three-phase short-circuit current which can be provided for the working point by the upstream and downstream of the working point is selected as the maximum short-circuit current, the reliability of the grounding wire can be effectively ensured, and the safety of maintenance personnel is further ensured.
Drawings
FIGS. 1 and 2 are flowcharts of the present invention;
FIG. 3 is a graph of the withstand current of the ground line as a function of the line switch protection action time for different cross-sectional areas;
fig. 4 is a schematic topological structure diagram of an active low-voltage power distribution network according to a fourth embodiment;
fig. 5 is a schematic topological structure diagram of an active low-voltage power distribution network corresponding to the fifth embodiment;
fig. 6 is a schematic diagram of the maintenance of a certain pole.
Detailed Description
The invention will now be described in detail with reference to the drawings and to specific embodiments.
Example 1
The invention is suitable for various active power distribution networks, in particular for active low-voltage power distribution networks with a large number of distributed power sources connected to the low-voltage side. As shown in fig. 1 and 2, a method for computing security check of an active low-voltage distribution network grounding device includes the following steps:
a1, obtaining a topological structure and parameters of the active low-voltage power distribution network.
The topology comprises: and the connection mode among all the power equipment (such as a distributed power supply and the like) connected in the active low-voltage distribution network.
The parameters include: the short-circuit capacity (the short-circuit capacity represents the power supply capacity of a power system and is used for calculating the impedance of the large power grid) of the large power grid connected with the active low-voltage power distribution network, the neutral point grounding mode (the unique grounding mode of the active low-voltage power distribution network is that a TT system, namely a power neutral point, is directly grounded, an electric equipment exposed conductive part is directly grounded, a TN system, namely a power neutral point, is directly grounded, and the equipment exposed conductive part is directly electrically connected with the power neutral point), line parameters (the length and the type of lines (different in impedance and capacitance resistance of all types of lines) in the active low-voltage power distribution network), distributed power supply parameters, the switching protection action time of the lines and the like.
A2, calculating to obtain a functional relation between the withstand current of the grounding wire and the protection action time of the line switch under different sectional areas based on an Audi-dak formula, and obtaining a functional relation diagram (shown in figure 3).
Wherein, the Audi dak formula is:
wherein S is the sectional area of the grounding wire; i k Is tolerant of current (i.e., short circuit current value flowing through the ground); t is the switch protection action time of the line; c is the thermal stability coefficient of the material used for the grounding wire.
The protection action time of the circuit switch is a fixed value, and the switch protection action time of different circuits in the power distribution network is different (the circuit is provided with a protection device, the farther the circuit is from the protection device, the longer the switch protection action time is).
A3, calculating the maximum short-circuit current of the working point according to the topological structure of the active low-voltage power distribution network:
calculating three-phase short-circuit current provided by each distributed power supply to a working point in the active low-voltage distribution network; calculating three-phase short-circuit current provided by a large power grid connected with an active low-voltage power distribution network to a working point;
if the grounding wire is positioned at the upstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the maximum value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point; if the grounding wire is positioned at the downstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the superposition value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point.
And A4, selecting a grounding wire sectional area as small as possible from a functional relation diagram according to the switching protection action time of the line where the working point is located under the condition that the grounding wire withstand current is larger than the maximum short-circuit current (namely, the principle of no fusing).
A5, calculating single-phase residual voltage and three-phase residual voltage of the working point, and if the single-phase residual voltage and the three-phase residual voltage are lower than the safety voltage of a human body, checking the sectional area of the selected grounding wire through safety; otherwise, jumping to the step A4, and reselecting a larger grounding wire sectional area for checking until the largest value of the grounding wire sectional area is selected.
A6, determining the using measure of the grounding wire according to the checking result of the sectional area of the grounding wire.
The formulas for calculating the single-phase residual voltage and the three-phase residual voltage show that the single-phase residual voltage and the three-phase residual voltage are respectively increased along with the increase of the short-circuit cable resistance and the wire clamp contact resistance of the grounding wire. The short-circuit cable resistance and the wire clamp contact resistance are reduced along with the increase of the sectional area of the grounding wire, and the sectional area is 16mm according to the DL-T879-2004 technology in the power industry 2 ，25mm 2 ，35mm 2 ，50mm 2 ，70mm 2 ，95mm 2 ，120mm 2 The average resistance value per meter should be less than 1.24mΩ,0.79mΩ,0.56mΩ,0.40mΩ,0.28mΩ,0.21mΩ,0.16mΩ, respectively. Therefore, a large enough sectional area of the grounding wire is required to be selected so as to ensure that the single-phase residual voltage and the three-phase residual voltage are lower than the safety voltage of a human body.
In individual cases (e.g. overhauling at the outlet end of the distribution transformer), even if the sectional area of the selected ground wire reaches the maximum value (e.g. 120 mm) under its construction specification 2 ) The cross section area is still freeThe method is checked by security. The maintenance personnel can adopt various using measures such as connecting the grounding wires in parallel or hanging multiple grounding wires to ensure the safety.
Based on the current situation of the active power distribution network, the invention provides a checking method of the grounding device, and a maintainer can flexibly find the optimal and safest grounding protection measures (namely the sectional area of the grounding wire and the using measure of the grounding wire) according to the method. Meanwhile, when the sectional area of the grounding wire is checked, the single-phase residual voltage and the three-phase residual voltage of the working point are considered, and the safety of maintenance personnel is effectively ensured.
Example two
Further, the calculation formula of the three-phase residual voltage is as follows:
U res3 ＝kU G +I DG (R x +R t )
in U G The power supply voltage of the large power grid; k is a partial pressure coefficient, k is less than 1; i DG A sum of three-phase short-circuit currents provided to the operating points for each distributed power supply; r is R x A cable resistor is short-circuited for a grounding wire; r is R t Is the contact resistance of the wire clip.
The single-phase residual voltage is obtained by superposing the voltage drop of the single-phase grounding current on a grounding device (the grounding device comprises a grounding wire, a grounding electrode, a wire clamp and other parts) and the ground potential difference between a working point and the grounding device, the ground potential difference is obtained by analyzing double-layer soil through a mirror image method, and the ground potential difference is expressed as follows:
wherein I is k Representing a single phase ground current at the ground line; k represents the reflection coefficient of the soil,
ρ 1 representing the resistivity of the upper soil, ρ 2 Representing the resistivity of the underlying soil; s represents the thickness of the upper soil; z is Z g1 Representing the ground resistance of the ground wire; z is Z g Representing the ground resistance of a distribution transformer and the ground resistance of a ground wireAnd (3) summing; r is R N Represents the neutral line resistance; r is R x Representing the ground wire short circuit cable resistance; r is R t Representing the contact resistance of the wire clip; x represents the distance between the operating point and the ground line.
The beneficial effects of this embodiment lie in:
the calculation formula of the single-phase residual voltage in the patent application number 202110442657.3, namely a safety check calculation method of an active power distribution network grounding device, is as follows:
wherein I is k Representing a single-phase ground current of the ground wire; ρ is the resistivity of the soil; z is Z g The grounding resistor is a grounding wire; x is the distance between the operating point and the ground line.
The patent does not consider the shunt effect of the zero line (namely N line) on the low-voltage side of the active low-voltage distribution network when calculating the single-phase residual voltage, simplifies a soil model into uniform soil (actually, the water content of each soil layer is different, and the soil resistivity of each soil layer is different), so that the calculated single-phase residual voltage is larger, the requirement on grounding resistance is higher (the single-phase residual voltage is positively related to the grounding resistance value and the single-phase residual voltage needs to be lower than the safety voltage of a human body).
The following are illustrated:
assuming that a remote sudden single-phase call occurs, as shown in fig. 6, the single-phase grounding current is 100A, the grounding resistance is 10Ω, the power-source grounding resistance is 4Ω, the grounding wire is 2m away from the electric pole (the electric pole is the operating point), the total resistance of the grounding wire is 5mΩ, and the neutral wire resistance is 1.2Ω.
According to the single-phase residual voltage method calculation described in the patent with application number 202110442657.3, namely a safety check calculation method for an active power distribution network grounding device, a soil model is uniform in soil quality, the resistivity of the soil is 100 omega/m, and the single-phase residual voltage is calculated to be 204V.
According to the method, the single-phase residual pressure is calculated to be about 29V according to the soil resistivity layering consideration, wherein the upper layer resistivity is 100 omega/m, the thickness is 1.2m, and the lower layer resistivity is 50 omega/m.
Obviously, the method disclosed by the patent has better effect.
The method has the beneficial effects that the soil resistivity is considered in a layering manner, the actual soil condition is more fitted, and meanwhile, the single-phase residual voltage can be more accurately obtained by considering the shunting effect of the low-voltage side zero line, so that the actual requirement on the grounding resistance is reduced, the cost of the grounding device is reduced, and the economic benefit of a power grid is improved.
Example III
Further, the step A3 specifically includes:
a31, the distributed power sources may be roughly classified into a rotary motor type distributed power source and an inverter type distributed power source according to the grid connection mode with the power distribution network. Three-phase short-circuit current provided by each distributed power supply to a working point in the active low-voltage power distribution network is calculated:
the three-phase short-circuit current calculation formula that rotary motor type distributed power supply provided to operating point:
in U N 、X d "exit voltage and sub-transient impedance of the rotary motor type distributed power supply, respectively.
The three-phase short-circuit current calculation formula provided by the inverse distributed power supply to the working point comprises the following steps:
wherein S is DG 、U DG The rated capacity and the rated voltage of the inversion type distributed power supply are respectively.
A32, calculating three-phase short-circuit current I provided to working points by a large power grid connected with an active low-voltage power distribution network f0 : the formula is as follows:
wherein Z is xi For rotary motor type distributed power supply xi The impedance value of the line to its upstream previous node; z is Z nj Is an inversion type distributed power supply ni The impedance value of the line to its upstream previous node; z is Z f2 An impedance value for a line between the distribution transformer and an upstream previous node; z is Z f3 A line impedance value for a line between the operating point and the distribution transformer; x is X s Impedance of a large power grid; z is Z T 、U 2N /U 1N The impedance and transformation ratio of the distribution transformer are respectively.
Wherein, the impedance X of the large power grid s The calculation formula is as follows:
wherein: u (U) G Is the power supply voltage of a large power grid, S c Is the short-circuit capacity of a large power grid.
A33, if the grounding wire is positioned at the upstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and taking the maximum value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point;
if the grounding wire is positioned at the downstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the superposition value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point.
Because a plurality of distributed power supplies are connected, bidirectional power flow occurs in the active low-voltage distribution network, namely, the power can be supplied in the upstream and downstream directions of the working point. The embodiment has the advantages that the bidirectional power flow in the active low-voltage power distribution network is considered, the maximum value of the three-phase short-circuit current which can be provided for the working point at the upstream and downstream of the working point is selected as the maximum short-circuit current, the reliability of the grounding wire can be effectively ensured, and the safety of maintenance personnel is further ensured.
Example IV
The active low voltage distribution network as shown in fig. 4 includes: large electric network G 1 Distribution transformer, m rotary motor type distributed power supply l xi The method comprises the steps of carrying out a first treatment on the surface of the (i is more than or equal to 0 and less than or equal to m), p inversion type distributed power supplies l nj (0.ltoreq.j.ltoreq.p). Wherein Z is xi Representation l xi The impedance value of the line to the previous node upstream thereof (as Z in FIG. 4 x2 Representation l x2 To l x1 Impedance value of the line between them); z is Z nj Representation l nj The impedance value of the line to the previous node upstream thereof (as Z in FIG. 4 n2 Representation l n2 To l n1 Impedance value of the line between them); z is Z f1 An impedance value of a line between the operating point and a previous node upstream thereof; z is Z f2 Impedance value of the line from the working point to the distribution transformer; z is Z c An impedance value for the line between the end of the line and its upstream previous node; kf 1 、Kf 2 Is a switch; u (U) 2N /U 1N Is the transformation ratio of the distribution transformer.
Let it be assumed that at the working point f 1 Overhauling the non-distal hanging ground wire 2: if K f2 If the power is not operated, the distributed power source at the low voltage side is reversely fed to the medium voltage side (i.e. working point f) 1 ) The sum of the three-phase short-circuit currents provided by the distributed power supplies to the operating points is calculated as follows:
wherein X is d "is the sub-transient impedance of a rotary motor type distributed power supply; s is S DG 、U DG Is rated capacity and rated voltage of the inversion type distributed power supply.
Example five
The active low voltage distribution network as shown in fig. 5 includes: large electric network G 1 Distribution transformer, m+n rotary motor type distributed power supply l xi The method comprises the steps of carrying out a first treatment on the surface of the (i is more than or equal to 0 and less than or equal to m+n), and p+q inversion type distributed power supplies l nj (0.ltoreq.j.ltoreq.p+q). Wherein Z is xi Representation l xi The impedance value of the line to the previous node upstream thereof (as Z in FIG. 4 x2 Representation l x2 To l x1 Impedance value of the line between them); z is Z nj Representation l nj The impedance value of the line to the previous node upstream thereof (as Z in FIG. 4 n2 Representation l n2 To l n1 Impedance value of the line between them); z is Z f1 An impedance value of a line between the operating point and a previous node upstream thereof; kf 1 、Kf 2 Is a switch; z is Z T 、U 2N /U 1N The impedance and transformation ratio of the distribution transformer are respectively shown. Z is Z k Representing the impedance value of the line between the end of the line and the upstream previous node; z is Z c Representing the impedance value of the line between the substation bus to the distribution transformer.
Assuming that the ground wire is hung at the operating point f1 for maintenance (when power is transmitted by mistake due to a fault or human factor, each distributed power source in the low-voltage side directly transmits power to the operating point):
if K f1 False operation, working point f 1 Upstream three-phase short-circuit current I f∑up The calculation is as follows:
if K f2 False operation, working point f 1 Downstream three-phase short-circuit current I f∑down The calculation is as follows:
wherein X is d "is the sub-transient impedance of a rotary motor type distributed power supply; s is S DG 、U DG Is rated capacity and rated voltage of the inversion type distributed power supply.
With I f∑ Representing the maximum short circuit current at the ground line. If I f∑up >I f∑down Then I f∑ ＝I f∑up If I f∑down >I f∑up Then I f∑ ＝I f∑down 。
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope of the present invention.
Claims (4)
1. The safety check calculation method of the grounding device of the active low-voltage distribution network is characterized by comprising the following steps of:
s1, selecting a sectional area of a grounding wire:
s11, acquiring parameters and a topological structure of an active low-voltage power distribution network;
s12, calculating to obtain a functional relation between the withstand current of the grounding wire and the protection action time of the circuit switch for the grounding wires with different sectional areas based on an Audi dak formula;
s13, calculating the maximum short-circuit current of the working point according to the topological structure of the active low-voltage power distribution network;
s14, selecting a grounding wire sectional area meeting a condition according to the switch protection action time of the line where the working point is located by utilizing the functional relation; the condition is that the ground wire withstand current is greater than the maximum short circuit current;
s2, checking the sectional area of the grounding wire according to the single-phase residual voltage and the three-phase residual voltage of the working point, and if the single-phase residual voltage and the three-phase residual voltage are lower than the safety voltage of a human body, checking the sectional area of the selected grounding wire safely; otherwise, the sectional area of the grounding wire is selected again;
the single-phase residual voltage is obtained by superposing the voltage drop of the single-phase grounding current on the grounding device and the ground potential difference between the working point and the grounding device, and the ground potential difference is obtained by analyzing double-layer soil by a mirror image method;
the calculation formula of the three-phase residual voltage is as follows:
U res3 ＝kU G +I DG (R x +R t )
in U G The power supply voltage of the large power grid; k is a partial pressure coefficient, k is less than 1; i DG A sum of three-phase short-circuit currents provided to the operating points for each distributed power supply; r is R x A cable resistor is short-circuited for a grounding wire; r is R t The contact resistance of the wire clamp;
the calculation formula of the single-phase residual voltage is as follows:
wherein I is k Representing a single phase ground current at the ground line; k represents the reflection coefficient of the soil,
ρ 1 representing the resistivity of the upper soil, ρ 2 Representing the resistivity of the underlying soilThe method comprises the steps of carrying out a first treatment on the surface of the s represents the thickness of the upper soil; z is Z g1 Representing the ground resistance of the ground wire; z is Z g Representing the sum of the grounding resistance of the distribution transformer and the grounding resistance of the grounding wire; r is R N Represents the neutral line resistance; r is R x Representing the ground wire short circuit cable resistance; r is R t Representing the contact resistance of the wire clip; x represents the distance between the operating point and the ground line.
2. The method for computing the security check of the grounding device of the active low-voltage distribution network according to claim 1, further comprising: and determining the using measure of the grounding wire according to the safety checking result of the sectional area of the grounding wire.
3. The method for computing the security check of the grounding device of the active low-voltage distribution network according to claim 1, wherein the audi dak formula in the step S12 is:
wherein S is the sectional area of the grounding wire; i k A withstand current for the ground line; t is the switch protection action time of the line; c is the thermal stability coefficient of the ground wire material.
4. The method for security check calculation of the grounding device of the active low-voltage distribution network according to claim 3, wherein the step S13 specifically comprises:
calculating three-phase short-circuit current provided by each distributed power supply to a working point in the active low-voltage distribution network; calculating three-phase short-circuit current provided by a large power grid connected with an active low-voltage power distribution network to a working point;
if the grounding wire is positioned at the upstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the maximum value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point; if the grounding wire is positioned at the downstream of each distributed power supply, taking the sum of three-phase short-circuit currents provided by each distributed power supply to the working point and the superposition value of the three-phase short-circuit currents provided by the large power grid to the working point as the maximum short-circuit current of the working point.
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| JP2012220383A (en) * | 2011-04-11 | 2012-11-12 | Chugoku Electric Power Co Inc:The | Short-circuit point locating device, short-circuit point locating method, and program |
| CN104568719A (en) * | 2015-01-12 | 2015-04-29 | 国家电网公司 | Evaluation method of transformer substation grounding grids |
| CN111257794A (en) * | 2020-01-20 | 2020-06-09 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Transformer substation grounding device thermal stability checking method based on conduction test |
| CN112363025A (en) * | 2020-12-14 | 2021-02-12 | 广东电网有限责任公司 | Power distribution network single-phase earth fault diagnosis method and system |
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| JP2012220383A (en) * | 2011-04-11 | 2012-11-12 | Chugoku Electric Power Co Inc:The | Short-circuit point locating device, short-circuit point locating method, and program |
| CN104568719A (en) * | 2015-01-12 | 2015-04-29 | 国家电网公司 | Evaluation method of transformer substation grounding grids |
| CN111257794A (en) * | 2020-01-20 | 2020-06-09 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | Transformer substation grounding device thermal stability checking method based on conduction test |
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