CN111257697A - Middle resistor line selection system for arc suppression coil grounding system - Google Patents
Middle resistor line selection system for arc suppression coil grounding system Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/16—Spectrum analysis; Fourier analysis
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/08—Measuring resistance by measuring both voltage and current
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
- G01R27/205—Measuring contact resistance of connections, e.g. of earth connections
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Abstract
The invention discloses a medium resistance line selection system for an arc suppression coil grounding system, which comprises: the device comprises a data acquisition module, an impedance calculation module and a line selection algorithm module. And the data acquisition module is used for acquiring zero-sequence voltage signals and branch zero-sequence current signals of the power grid. And the impedance calculation module is used for calculating the steady-state impedance of each branch circuit on the basis of the zero-sequence voltage of the power grid and the zero-sequence current of the branch circuit. And the line selection algorithm module is used for identifying faults and controlling the switching on and off of the middle resistor, and performing line selection algorithm analysis according to the change of the steady-state impedance of each branch before and after the switching on and off of the middle resistor to judge the grounding branch. The line selection system is based on the impedance characteristics of each branch circuit and the middle resistor in the power grid and is irrelevant to the grounding process, so that the grounding line can be reliably, accurately and quickly selected according to the difference of the impedance of each branch circuit before and after the middle resistor is switched.
Description
Technical Field
The invention relates to the field of power systems, in particular to a medium resistance line selection system for an arc suppression coil grounding system.
Background
In a 6-66 kV power grid in China, a mode that a neutral point is grounded through an arc suppression coil is adopted in large quantity. In this way, when the system has single-phase earth fault, capacitive earth current is generated, and the arc suppression coil can provide an inductive compensation current opposite to the capacitive earth current at the moment, so that the earth ground current is reduced. This is the basic working and compensation principle of the arc suppression coil.
Due to the compensation effect of the arc suppression coil, the grounding point current is reduced. Meanwhile, in order to prevent possible series resonance after the arc suppression coil is put into use, the arc suppression coil generally adopts an overcompensation mode, namely, the compensated inductive current is 5% larger than the grounding current. Thus, the direction of the current actually flowing through the grounding branch is the same as that of other normal branches, and the current amplitude is not the maximum. Therefore, after the arc suppression coil is put into use, the group amplitude-to-amplitude ratio phase method generally adopted for a neutral point ungrounded grid cannot be used.
Therefore, the neutral point is grounded through the arc suppression coil, and the line selection is generally performed by adopting a medium resistance method. The so-called medium resistance method line selection is to inject an extra resistive current into the system by inputting a medium resistor connected with the arc suppression coil in parallel after grounding occurs and is stabilized, and the resistive current only flows through a grounding branch. Therefore, after the middle resistor is put into use, the current of the grounding branch can be increased, and the grounding branch can be found as long as the branch with the largest current change of the grounding branch is found.
However, after the medium resistor is put into use, not only the current flowing through the grounding branch is increased, but also the voltage of the system neutral point is reduced, and the reduction of the voltage causes the reduction of the current of all branches including the grounding branch, so that the current of the grounding branch may not change obviously, and the current of the non-grounding branch is reduced, thereby causing a line selection error. The current reduction caused by the resistance input and the voltage reduction is more obvious under the condition of high-resistance grounding, and the misselection cannot be avoided. Therefore, the arc suppression coil system is selected through the medium resistor, and in actual operation, particularly when the arc suppression coil system is grounded at a high resistance, the medium resistor is put into use and the selection is performed only depending on the change of the current, which is not completely accurate and reliable.
Document 103207352a describes a fault line selection method for achieving single-phase grounding of a power distribution network by using a line selection impedance magnitude characteristic. The zero sequence voltage of the power grid before and after the switching of the middle resistor and the zero sequence current of each branch are measured, then the zero sequence current before the switching of the middle resistor is converted into the zero sequence current after the switching of the middle resistor, and finally the so-called line selection impedance is calculated. The essence is that the current generated by the medium resistance can only flow back to the system through the grounding branch circuit, so that the current of the grounding branch circuit is increased; and the current after the normal branch circuit is converted is approximately unchanged. Therefore, the 'line selection impedance' of the grounding branch is smaller, and the 'line selection impedance' of the normal branch is larger. However, in actual operation, especially when the neutral point voltage is low and the current increment generated after the medium resistor is put into use is small, the calculated "line selection impedance" will be relatively high and is difficult to distinguish from the "line selection impedance" of the normal branch, and therefore the line selection accuracy is greatly reduced.
Document CN110456218A describes a fast fault line selection method based on power frequency increment coefficients before and after medium resistance switching, which uses the variation of power frequency components in zero-sequence currents of branches of medium resistance switching first half cycle and switching second half cycle to perform line selection. The current change caused by the system voltage change caused by the medium resistor input is not considered, and the current response delay caused by the time error of the medium resistor switching control to the actual input of the medium resistor is not considered, so that the zero sequence current before and after the medium resistor switching and the incremental coefficient calculated by the current are inaccurate, and the accuracy of line selection is influenced.
Document CN101540499A describes a median resistance grounding fast route selection tripping device and a route selection method for an urban distribution network, which utilize comparison of amplitudes of zero-sequence currents of branches (so-called transverse comparison) and comparison of phase differences of zero-sequence currents of branches (so-called longitudinal comparison) to determine a route selection result. The current change caused by the system voltage change caused by the resistor input is not considered; and when the high resistance is grounded, the current increment is small, and the current change is limited. These all cause errors in line selection.
Therefore, the problems that current calculation is inaccurate, a line selection result is influenced by a grounding process and the like exist in the existing line selection of the medium resistor. The line selection is most accurate and reliable only by finding the line selection which is not influenced by the grounding process, does not depend on the absolute value of the current and only depends on the electrical characteristics of the branch circuit.
Disclosure of Invention
The invention provides a medium resistance line selection system for an arc suppression coil grounding system, aiming at the problems in the prior art, and the line selection system is used for selecting lines by measuring the steady-state impedance change of each branch circuit before and after the medium resistance is put into the system after grounding occurs. The steady-state impedance of each branch circuit is irrelevant to the grounding process, only the characteristic of the ground impedance of the characteristic of the branch circuit is reflected, and the reliable, accurate and quick line selection of the medium resistor of the arc suppression coil grounding system can be realized.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a medium resistance route selection system for an arc suppression coil grounding system is characterized by comprising: the device comprises a data acquisition module, an impedance calculation module and a line selection algorithm module;
and the data acquisition module is used for acquiring the zero sequence voltage of the power grid and the zero sequence current signals of each branch circuit required by the line selection of the central resistor. And transmitting the collected power grid zero sequence voltage and branch zero sequence current signals to the impedance calculation module and the line selection algorithm module.
And the impedance calculation module receives a starting command from the line selection algorithm module, receives the zero sequence voltage of the power grid and the zero sequence current signals of each branch of the data acquisition module, and performs steady-state impedance calculation on the signals. And inputting the calculated impedance of each branch circuit into a line selection algorithm module.
The line selection algorithm module receives a zero sequence voltage signal from the data acquisition module, judges the occurrence and recovery of a fault and controls the on/off of a middle resistor, and starts the impedance calculation module after the fault occurs; and receiving the steady-state impedance of each branch circuit from the impedance calculation module before and after the on/off of the medium resistance, and performing line selection algorithm analysis according to the change of the steady-state impedance of each branch circuit so as to judge the grounding branch circuit.
Preferably, the medium resistance line selection system for the arc suppression coil grounding system is characterized in that the data acquisition module acquires zero sequence voltage signals of a power grid and zero sequence current signals of branch circuits. In order to ensure the accuracy of subsequent impedance calculation, the module adopts the multi-path synchronous and high-speed sampling technology. Wherein:
the multi-path synchronous sampling can meet the requirement of full synchronous acquisition of 100 paths of alternating voltage or current with a synchronous error not exceeding 1 mu S; the multi-path high-speed sampling can carry out high-speed acquisition of more than 12.8kHz on each path of alternating voltage or current.
Preferably, the medium resistance line selection system for the arc suppression coil grounding system is characterized in that the impedance calculation module performs steady-state impedance calculation on zero sequence voltage and zero sequence current signals from the data acquisition module, and transmits an impedance calculation result to the line selection algorithm module.
The impedance calculation module mainly aims at zero sequence impedance of each branch circuit before and after the medium resistor is switched on and off. Before and after the medium resistor is switched on and off, the single-phase grounding of the power grid is in a steady state condition, so the impedance calculation module only needs to calculate the impedance of each branch circuit under the steady state condition.
The impedance calculation module calculates the effective value of the zero sequence voltage of the power grid and the effective value of the zero sequence current of each branch by adopting a root-mean-square algorithm, so as to calculate the steady-state impedance of each branch. The calculation method comprises the following steps:
Rk＝Uk/Ik
preferably, the line selection algorithm module further includes: fault recognition submodule, line selection judge submodule, wherein:
and the fault identification submodule receives the zero-sequence voltage data from the data acquisition module and then calculates the effective value of the zero-sequence voltage by adopting a root-mean-square algorithm. When the zero sequence voltage effective value exceeds the preset fault voltage value, the fault is considered to occur, the time of the fault occurrence is recorded, and an impedance calculation module is started; and when the zero sequence voltage is recovered to be below the set fault voltage value, the fault is considered to be ended, the end time of the fault is recorded, and the impedance calculation module is stopped.
And the fault identification submodule continuously judges the fault state after identifying the fault occurrence and starting the impedance calculation module, records the impedance of each branch transmitted by the impedance calculation module at the moment as initial impedance if the fault continuously exists for more than 1S, and then puts in a middle resistor. After the middle resistor is put into 0.5S, the impedance of each branch circuit transmitted by the impedance calculation module at the moment is recorded again to serve as final impedance, and then the middle resistor is cut off. And the initial impedance and the final impedance are input into the line selection judgment submodule for line selection calculation.
And the line selection judgment submodule receives the initial impedance and the final impedance of each branch circuit transmitted from the fault identification submodule and finds the branch circuit with the maximum absolute value of impedance change, namely the grounding branch circuit. The calculation method comprises the following steps:
when line selection judgment is carried out, the grounding resistance is changed after the medium resistance is considered, so that zero sequence voltage of a power grid is changed, and further, currents of all branches are correspondingly changed, and therefore the grounding branches cannot be accurately judged by directly adopting the change of the currents. The steady-state impedance of the line represents the impedance of the line per se for a normal line, and is irrelevant to whether the middle resistor is put into the ground voltage or not; for the grounding circuit, the parallel sum of the intermediate resistance and the impedance of other normal branches is reflected, so that the change of the impedance before and after the intermediate resistance is input is only reflected on the grounding branch, and the grounding branch can be accurately selected.
Preferably, the medium resistance line selection system for the arc suppression coil grounding system is characterized in that the impedance calculation module only needs to operate after a ground fault occurs and calculates before and after the resistance in switching. When the power grid has no ground fault, the zero sequence voltage of the power grid is very small and the zero sequence current of each branch is also very small according to the electrical characteristics of the power grid, and the calculated steady-state impedance is inaccurate at the moment and cannot be used for calculation of a line selection algorithm. Only when the system is in single-phase grounding, the zero sequence voltage and the zero sequence current of each branch are high enough, the calculated steady-state impedance is accurate enough, and the calculated steady-state impedance can be used for line selection calculation.
Preferably, the medium resistance line selection system for the arc suppression coil grounding system is characterized in that the impedance refers to zero sequence impedance to ground of a zero sequence loop of a line and a medium resistance. The impedance characteristics of the line and the middle resistor are reflected, are only related to the electrical design parameters and the manufacturing process of the line and the middle resistor, are not related to the specific grounding process and the power grid operation condition, can be definitely used as a characteristic signal for identifying the grounding fault, and the grounding branch can be quickly and accurately judged by calculating the impedance and the impedance change of the impedance.
Compared with the prior art, the invention has the following advantages:
(1) the invention relates to a medium resistance line selection system for an arc suppression coil grounding system, which is based on the impedance characteristics of each branch circuit and the medium resistance in a power grid, is only related to the electrical design parameters and the manufacturing process of the circuit and the medium resistance, and is not related to the grounding process, so that the grounding circuit can be reliably, accurately and quickly selected according to the difference of the impedance of each branch circuit before and after the switching of the medium resistance.
(2) The medium resistance line selection system for the arc suppression coil grounding system can be suitable for a 6-66 kV neutral point arc suppression coil grounding power grid, and can be suitable for main arc suppression coil types, such as turn adjustment type, capacitance adjustment type, phase control type, magnetic bias type and the like.
Of course, it is not necessary for any product in which the invention is practiced to achieve all of the above-described advantages at the same time.
Drawings
Embodiments of the invention are further described below with reference to the accompanying drawings:
FIG. 1 is a block diagram of the modules that make up the system of the preferred embodiment of the present invention;
FIG. 2 is a system internal data flow diagram of the preferred embodiment of the present invention;
FIG. 3 is a block diagram of an impedance calculation module according to a preferred embodiment of the present invention;
FIG. 4 is a block diagram of a module structure of a line selection algorithm according to a preferred embodiment of the present invention;
FIG. 5 is a waveform of a fault according to a preferred embodiment of the present invention.
FIG. 6 is a diagram illustrating the calculation results of the impedance variation according to the preferred embodiment of the present invention.
Detailed Description
The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.
An embodiment of a medium resistance line selection system for an arc suppression coil grounding system according to the present invention is described in detail with reference to fig. 1, and as shown in fig. 1, the embodiment includes: the device comprises a data acquisition module 1, an impedance calculation module 2 and a line selection algorithm module 3; the data acquisition module 1 is used for acquiring basic power grid zero sequence voltage and branch zero sequence current signals required by impedance detection. Transmitting the collected power grid zero sequence voltage and branch zero sequence current signals to an impedance analysis module 2 and a line selection algorithm module 3; the impedance calculation module 2 receives the voltage and current data from the data acquisition module 1, and based on the data, calculates effective values of the voltage and the current by adopting a root mean square algorithm, further calculates the steady-state impedance of each branch, and inputs the impedance of each branch into the line selection algorithm module 3; the line selection algorithm module 3 is used for receiving the voltage signal from the acquisition module 1, identifying faults and starting the impedance calculation module 2 after the faults occur; meanwhile, branch steady-state impedance data from the impedance calculation module 2 are received, in the fault existence process, the line selection algorithm module 3 controls the switching-in and the switching-out of the middle resistor, the branch steady-state impedance at the time is synchronously recorded in the switching-in and switching-out processes of the middle resistor, and then line selection algorithm analysis is carried out according to the change of the branch steady-state impedance, so that the grounding branch is judged.
In this embodiment, zero sequence voltage U0 of the power grid and zero sequence currents of 3 branches, that is, a branch 1 current I01, a branch 2 current I02, and a branch 3 current I03 are collected. And respectively carrying out ground fault simulation on the branch circuits 1, and then carrying out a medium resistance line selection test.
The specific implementation of each module in the above embodiments is described in detail below:
1. a data acquisition module, as shown in fig. 2:
the module collects zero sequence voltage U0 from the power grid, and zero sequence currents I01, I02 and I03 of 3 branches. For the acquired result, the data acquisition module 1 inputs the zero sequence voltage U0 data to the line selection algorithm module 3; the data acquisition module 1 inputs zero sequence voltage U0 and zero sequence currents I01, I02 and I03 of 3 branches into the impedance calculation module 2.
The acquisition rate of the data acquisition module is 12.8kHz, the acquisition of all voltage and current signals is completely synchronous, and the time synchronization error among the signals is not more than 1 muS, so that the accuracy of signals required by subsequent frequency spectrum analysis and grounding line selection can be effectively ensured.
2. An impedance calculation module, as shown in fig. 2 and 3:
the module receives the zero sequence voltage U0 transmitted by the data acquisition module and the zero sequence currents I01, I02 and I03 of each branch, calculates and obtains effective values of the zero sequence voltage and the zero sequence currents of each branch by adopting a root-mean-square algorithm, and then calculates the steady-state impedances R1, R2 and R3 of each branch.
Rk＝Uk/Ik
The calculated characteristic impedance of each branch is input into a line selection algorithm module 3.
An example of the impedance analysis results of this module is shown in fig. 6.
4. A line selection algorithm module, as shown in fig. 2 and 4:
this module receives the zero sequence voltage U0 signal from the data acquisition module 1 and the steady state impedances R1, R2, R3 of the individual branches from the impedance calculation module 2.
The module firstly calculates the effective value of the zero sequence voltage U0, judges whether the zero sequence voltage U0 exceeds the set starting voltage of the ground fault, and if the zero sequence voltage U0 exceeds the starting voltage, the power grid is considered to be grounded in a single phase. At this point the impedance calculation block 2 is started.
The module continuously monitors whether grounding exists after judging that the power grid is grounded in a single phase and starting the impedance calculation module 2, records the steady-state impedance value of each branch when the grounding time exceeds the set fault duration (2 seconds in the embodiment) and then puts in a middle resistor; after the medium resistance was put in for 1 second, the steady state impedance of each branch was recorded again, and then the medium resistance was withdrawn. And finding out the branch with the maximum change value as the grounding branch by calculating the steady-state impedance change value of each branch before and after the resistance is switched on and off. If the changes of the branches are similar, the bus is considered to be grounded.
An example of an analysis of this module is shown in fig. 5 and 6. FIG. 5 shows waveforms before and after grounding and medium resistance application; fig. 6 is an analysis calculation of zero sequence voltage of the power grid before and after the medium resistance is switched on and off and impedance of each branch circuit.
According to the medium resistance line selection system for the arc suppression coil grounding system, accurate and quick judgment of a single-phase grounding fault branch circuit when a neutral point is grounded to a power grid through the arc suppression coil is achieved, the characteristic that the line impedance only reflects the impedance characteristic of the line is utilized, the influence of voltage reduction on current change caused by medium resistance input during conventional medium resistance line selection can be effectively avoided, and the defects that the current of each branch circuit does not have obvious change and cannot be selected due to the obvious voltage reduction during conventional medium resistance line selection can be particularly overcome. The system greatly improves the accuracy and reliability of single-phase earth fault selection when the neutral point is earthed to the power grid through the arc suppression coil, and effectively improves the operation safety of the power grid.
The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and not to limit the invention. Any modifications and variations within the scope of the description, which may occur to those skilled in the art, are intended to be within the scope of the invention.
Claims (6)
1. A medium resistance route selection system for an arc suppression coil grounding system is characterized by comprising: the device comprises a data acquisition module, an impedance calculation module and a line selection algorithm module;
the data acquisition module is used for acquiring a power grid zero sequence voltage and each branch zero sequence current signal required by the line selection of the central resistor; transmitting the collected power grid zero sequence voltage and branch zero sequence current signals to the impedance calculation module and the line selection algorithm module;
the impedance calculation module receives a starting command from the line selection algorithm module, receives the zero sequence voltage of the power grid and the zero sequence current signals of each branch of the data acquisition module, and performs steady-state impedance calculation on the signals; the calculated impedance of each branch circuit is input into a line selection algorithm module;
the line selection algorithm module receives a zero sequence voltage signal from the data acquisition module, judges the occurrence and recovery of a fault and controls the on/off of a middle resistor, and starts the impedance calculation module after the fault occurs; and receiving the steady-state impedance of each branch circuit from the impedance calculation module before and after the on/off of the medium resistance, and performing line selection algorithm analysis according to the change of the steady-state impedance of each branch circuit so as to judge the grounding branch circuit.
2. The medium resistance line selection system for an arc suppression coil grounding system according to claim 1, wherein the data acquisition module acquires a zero sequence voltage of a power grid and a zero sequence current signal of a branch circuit; in order to ensure the accuracy of subsequent impedance calculation, the module adopts a multi-path synchronous and high-speed sampling technology; wherein:
the multi-path synchronous sampling can meet the requirement of full synchronous acquisition of 100 paths of alternating voltage or current with a synchronous error not exceeding 1 mu S; the multi-path high-speed sampling can carry out high-speed acquisition of more than 12.8kHz on each path of alternating voltage or current.
3. The medium resistance line selection system for an arc suppression coil grounding system as claimed in claim 1, wherein the impedance calculation module performs steady-state impedance calculation on the voltage and current signals from the data acquisition module and transmits the impedance calculation result to the line selection algorithm module;
the impedance calculation module mainly aims at the impedance of each branch circuit before and after the medium resistor is put on and off; before and after the medium resistor is switched on and off, the single-phase grounding of the power grid is in a stable state, so that the impedance calculation module only needs to calculate the impedance of each branch circuit under the stable state;
the impedance calculation module calculates an effective value of zero-sequence voltage of a power grid and an effective value of zero-sequence current of each branch by adopting a root-mean-square algorithm, so as to calculate the steady-state zero-sequence impedance of each branch; the calculation method comprises the following steps:
Rk＝Uk/Ik
4. the medium resistance line selection system for a crowbar coil grounding system of claim 1, wherein the line selection algorithm module further comprises: fault recognition submodule, line selection judge submodule, wherein:
the fault identification submodule receives zero sequence voltage data from the data acquisition module and then calculates the effective value of the zero sequence voltage by adopting a root mean square algorithm; when the zero sequence voltage effective value exceeds the preset fault voltage value, the fault is considered to occur, the time of the fault occurrence is recorded, and an impedance calculation module is started; when the zero sequence voltage is recovered to be below the set fault voltage value, the fault is considered to be ended, the end time of the fault is recorded, and the impedance calculation module is stopped;
the fault identification submodule continuously judges the fault state after identifying the fault occurrence and starting the impedance calculation module, records the impedance of each branch transmitted by the impedance calculation module at the moment as the initial impedance if the fault continuously exists for more than 1S, and then puts in a middle resistor; after the middle resistor is put into 0.5S, the impedance of each branch circuit transmitted by the impedance calculation module at the moment is recorded again to serve as final impedance, and then the middle resistor is cut off. The initial impedance and the final impedance are input into a line selection judgment submodule for line selection calculation;
and the line selection judgment submodule receives the initial impedance and the final impedance of each branch circuit transmitted from the fault identification submodule and finds the branch circuit with the maximum absolute value of impedance change, namely the grounding branch circuit. The calculation method comprises the following steps:
when line selection judgment is carried out, the line selection algorithm module considers that after the medium resistor is put into use, the grounding resistor is changed, so that zero sequence voltage of a power grid is changed, and further, the current of all branches is correspondingly changed, so that the grounding branch cannot be accurately judged by directly adopting the change of the current; the steady-state impedance of the line represents the zero sequence impedance of the line for a normal line, and is irrelevant to whether the middle resistor is put into use or not and the grounding voltage; for the grounding circuit, the parallel sum of the medium resistance and the zero sequence impedance of other normal branches is reflected, so that the change of the impedance before and after the medium resistance is input can be reflected on the grounding branch only, and the grounding branch can be accurately selected.
5. A medium resistance line selection system for an arc suppression coil grounding system according to any one of claims 1 to 4, wherein the impedance calculation module is only required to operate after a grounding fault occurs and to perform calculation before and after the resistance is switched. When the power grid has no ground fault, the zero-sequence voltage of the power grid is very small and the zero-sequence current of each branch is also very small according to the electrical characteristics of the power grid, and the calculated steady-state impedance is inaccurate and cannot be used for calculation of a line selection algorithm; only when the system is in single-phase grounding, the zero sequence voltage and the zero sequence current of each branch are high enough, the calculated steady-state impedance is accurate enough, and the calculated steady-state impedance can be used for line selection calculation.
6. The medium resistance line selection system for an arc suppression coil grounding system according to claim 5, wherein the impedance refers to zero sequence impedance to ground of a zero sequence loop of a line and a medium resistance; the impedance characteristics of the line and the middle resistor are reflected, are only related to the electrical design parameters and the manufacturing process of the line and the middle resistor, are not related to the specific grounding process and the power grid operation condition, can be definitely used as a characteristic signal for identifying the grounding fault, and the grounding branch can be quickly and accurately judged by calculating the impedance and the impedance change of the impedance.
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| CN202010213290.3A CN111257697A (en) | 2020-03-24 | 2020-03-24 | Middle resistor line selection system for arc suppression coil grounding system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112305375A (en) * | 2020-10-26 | 2021-02-02 | 西安工程大学 | High-resistance grounding fault line selection method for resonant grounding system |
| CN112731047A (en) * | 2020-12-03 | 2021-04-30 | 天津大学 | Fault line selection method suitable for flexible grounding system |
-
2020
- 2020-03-24 CN CN202010213290.3A patent/CN111257697A/en not_active Withdrawn
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112305375A (en) * | 2020-10-26 | 2021-02-02 | 西安工程大学 | High-resistance grounding fault line selection method for resonant grounding system |
| CN112305375B (en) * | 2020-10-26 | 2023-08-22 | 西安工程大学 | High-resistance grounding fault line selection method for resonant grounding system |
| CN112731047A (en) * | 2020-12-03 | 2021-04-30 | 天津大学 | Fault line selection method suitable for flexible grounding system |
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