CN210534262U - Large-current fault line selection system of resonance grounding system - Google Patents
Large-current fault line selection system of resonance grounding system Download PDFInfo
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- CN210534262U CN210534262U CN201921402976.6U CN201921402976U CN210534262U CN 210534262 U CN210534262 U CN 210534262U CN 201921402976 U CN201921402976 U CN 201921402976U CN 210534262 U CN210534262 U CN 210534262U
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Abstract
The utility model discloses a big current fault route selection system of resonance ground system, wherein the neutral point is earthed through the arc suppression coil, including the voltage transformer that is used for detecting single-phase earth fault and takes place, the first current transformer that is used for detecting each branch zero sequence current, the signal conditioning circuit that is used for handling voltage transformer and first current transformer output signal, the AD converting circuit that is used for converting voltage transformer and first current transformer output analog signal into digital signal, the microprocessor that is used for zero sequence current analysis and the initiative ground system that is controlled by microprocessor; the active grounding system mainly comprises a first grounding transformer, a quick switch and a second current transformer, wherein the quick switch is connected between a neutral point on the high-voltage side of the grounding transformer and the ground after being connected in series with the second current transformer, and the quick switch is controlled by the microprocessor.
Description
Technical Field
The utility model relates to a ground connection route selection technical field specifically is a resonance grounding system's heavy current trouble route selection system with initiative.
Background
Single-phase earth faults are the most dominant fault form in power systems, accounting for over 70% of the total number of faults. The advantage of the low-current grounding system is that after single-phase grounding (such as phase C of line 2 in fig. 1) occurs, the symmetry of the system line voltage is not damaged, and the system can still supply power normally, i.e. continuous power supply of the grid users is not affected. However, when the arc-shaped power grid is grounded, overvoltage of the whole power grid system can be caused, electric equipment is likely to be damaged, personal safety is threatened, and safe operation of the system is damaged; meanwhile, the non-fault phase-to-ground voltage of the power grid can rise, which may cause the weak insulation link of the power grid to be broken down by high voltage or to be in interphase short circuit, so that the power grid accident is further expanded, and the normal power supply of a power grid user is influenced. Therefore, to ensure the normal operation of the power grid system, when a single-phase earth fault occurs in the low-current earth system, the fault line and the fault position of the power grid must be accurately positioned in time, so as to eliminate the fault.
In a small current grounding system, two forms of neutral point non-grounding and neutral point grounding through an arc suppression coil are mainly adopted. When a single-phase grounding occurs in a system with a neutral point not grounded, the current flowing through the grounding point is the current of a system ground distributed capacitor, and the magnitude of the current is related to the voltage grade, the magnitude of the power grid scale and the structure of a line. The installation arc suppression coil can make the fundamental wave electric capacity current of ground point reduce, is favorable to extinguishing by oneself of fault point electric arc, can make the harm degree of fault point reduce. From the perspective of being beneficial to arc extinction and reducing residual current of the grounding point, the full compensation effect is best. However, the structure and operation mode of the power grid are constantly changed, and the distributed capacitance current of the system is not a constant quantity, so that in order to realize full compensation, the arc suppression coil must adopt variable inductance to automatically track the capacitance current of the system in real time.
Therefore, automatic tracking compensation of the arc suppression coil and automatic line selection of the small-current ground fault are measures for reducing the damage degree of the single-phase ground fault, have very important functions for improving the safety, the economy and the reliability of a power distribution system, and need to take consideration simultaneously. In addition, after the small current grounding system is subjected to single-phase grounding, the fault characteristics are not obvious, and in addition, certain difficulty exists in rapidly and accurately finding out a grounding loop. The existing single-phase earth fault line selection methods have the problems of low detection accuracy or excessively complex detection methods. For example, patent CN105067948B published in 2018, 6, 12 discloses a high-current fault line selection system and a single-phase ground detection method of a resonant grounding system based on voltage and current phasors, which simplify the existing algorithm at that time, but are still complex.
SUMMERY OF THE UTILITY MODEL
The shortcoming and not enough to prior art, the utility model provides a resonance grounding system's heavy current trouble route selection system with initiative.
A large-current fault line selection system of a resonance grounding system comprises a voltage transformer for detecting single-phase grounding fault, a first current transformer for detecting zero sequence current of each branch, a signal conditioning circuit for processing output signals of the voltage transformer and the first current transformer, an AD conversion circuit for converting output analog signals of the voltage transformer and the first current transformer into digital signals, a microprocessor for analyzing the zero sequence current and an active grounding system controlled by the microprocessor;
the active grounding system mainly comprises a first grounding transformer, a quick switch and a second current transformer, wherein the quick switch is connected between a neutral point on the high-voltage side of the first grounding transformer and the ground after being connected in series with the second current transformer, and the quick switch is controlled by the microprocessor;
the arc suppression coil is provided with a secondary winding and is matched with a second grounding transformer, an isolating switch, a damping resistance box and a capacitance compensation cabinet, the isolating switch is connected between the second grounding transformer and the arc suppression coil, and the damping resistance box is connected between the arc suppression coil and the ground; the capacitance compensation cabinet mainly comprises a capacitor bank, a thyristor bank, a fuse and a fan, thyristors are reversely connected in parallel and then are connected in series with the capacitors to form a compensation branch, a plurality of compensation branches, the fuse and the fan are all connected in parallel to the secondary winding side of the arc suppression coil, and the thyristors are controlled by the microprocessor;
the quick switch adopts a quick vacuum switch based on an electromagnetic repulsion mechanism; the microprocessor is connected with a monitoring server through a network, and the monitoring server provides display, alarm and real-time query services.
Furthermore, the signal conditioning circuit adopts a low-pass filter circuit, and the input end of the low-pass filter circuit is connected with a voltage-limiting and amplitude-limiting circuit formed by two voltage-stabilizing diodes which are connected in series in a reverse direction.
Further, the AD conversion circuit employs a 14-bit analog-to-digital converter MAX125 and peripheral circuits thereof.
Furthermore, the microprocessor adopts a DSP chip TMS320F2812 and peripheral circuits thereof; the microprocessor is connected with a watchdog circuit, and the watchdog circuit adopts a reset chip MAX706 and peripheral circuits thereof.
Further, the grounding transformer is connected with a surge protector in parallel.
The utility model has the advantages that: when the power system has single-phase earth fault, the system can accurately select a fault loop, effectively reduce the probability of two-phase long-distance short circuit or interphase short circuit formed by the power system due to single-phase earth, avoid the system from accidents and have remarkable economic benefit; the arc suppression coil is provided with an automatic tracking compensation system, so that the arc suppression angle is facilitated, the residual current of a grounding point is reduced, automatic tracking type full compensation is provided for the system, and the safety coefficient of the system is improved.
Drawings
FIG. 1 is a schematic diagram of a single phase ground fault;
FIG. 2 is a schematic diagram of zero sequence current in a neutral point arc suppression coil grounding system;
FIG. 3 is a main block diagram of a high current fault line selection system of the resonant grounding system;
FIG. 4 is a schematic diagram of an active grounding system;
FIG. 5 is a schematic diagram of an automatic tracking compensation system for an arc suppression coil;
FIG. 6 is a diagram of a second grounding transformer;
FIG. 7 is an electrical structure diagram of an automatic tracking compensation arc suppression coil (one control two);
FIG. 8 is a schematic diagram of the compensation branch connection;
FIG. 9 is a circuit diagram of a microprocessor watchdog reset circuit;
fig. 10 is a low-pass filter circuit diagram.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The embodiments of the present invention have been presented for purposes of illustration and description, and are not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Example 1
In a system with a neutral point grounded through an arc suppression coil, the zero sequence current in a fault line is the sum of the zero sequence current of a non-fault line and the inductive current in the arc suppression coil, the current direction is the bus flow direction line, and as shown in fig. 2, the relation of each branch current has a formula iL1＝iL2+iL3+iL4+iL5。
Although the zero sequence current has a certain correlation with the fault branch, the zero sequence capacitance current flowing on each branch after the fault is determined only by the zero sequence voltage of the system and the ground capacitance of the branch, but not by which branch the fault occurs, and the ground capacitances of the branches before and after the fault occurs are almost unchanged. Therefore, the grid fault line and the fault position cannot be accurately judged only according to the zero sequence current.
The utility model adopts the large current fault line selection system of the active resonance grounding system, after detecting the occurrence of single-phase grounding fault, the current signal is injected into the system through the active grounding of the first grounding transformer, and the injected current signal is transmitted along the grounding loop and finally flows into the single-phase grounding fault point, thereby determining the single-phase grounding fault point by comparing the current signals detected by the zero sequence current transformers of each branch circuit before and after the active grounding; meanwhile, an automatic tracking compensation system is provided for the arc suppression coil, the switching of capacitor banks with different capacities is regulated and controlled through a high-power thyristor so as to realize the real-time compensation effect on the capacitance current of system change, the applied principle is that the capacitance is switched when the voltage at two ends of the thyristor passes through zero, and the capacitor is naturally cut off when the current passes through zero, so that the problems of switching-on surge current and overvoltage during the switching of the capacitor can be effectively avoided.
Specifically, as shown in fig. 3 and 4, the large-current fault line selection system of the resonant grounding system includes a voltage transformer for detecting occurrence of a single-phase grounding fault, a first current transformer for detecting zero-sequence current of each branch, a signal conditioning circuit for processing output signals of the voltage transformer and the first current transformer, an AD conversion circuit for converting output analog signals of the voltage transformer and the first current transformer into digital signals, a microprocessor for analyzing the zero-sequence current, and an active grounding system controlled by the microprocessor.
The active grounding system mainly comprises a first grounding transformer 1, a quick switch 2 and a second current transformer, wherein the quick switch and the second current transformer are connected in series and then connected between a neutral point on the high-voltage side of the grounding transformer and the ground, and the quick switch is controlled by the microprocessor. The grounding transformer is connected with a surge protector 3 in parallel.
The arc suppression coil is provided with a secondary winding and is matched with a second grounding transformer 4, an isolating switch 5, a damping resistance box 6 and a capacitance compensation cabinet 7, the isolating switch 5 is connected between the second grounding transformer 4 and the arc suppression coil, the damping resistance box 6 is connected between the arc suppression coil and the ground, as shown in figure 5, when the neutral point of the system is △ type wiring or Y type wiring, the neutral point is led out to connect the arc suppression coil, and the structure diagram is shown in figure 6.
The capacitance compensation cabinet mainly comprises a capacitor bank, a thyristor bank, a fuse and a fan, referring to fig. 7, thyristors are reversely connected in parallel and then are connected in series with a capacitor to form a compensation branch, a plurality of compensation branches, the fuse and the fan are all connected in parallel on the secondary winding side of the arc suppression coil, referring to fig. 8, and the thyristors are controlled by the microprocessor. The microprocessor adopts a DSP chip TMS320F2812 and peripheral circuits thereof, and the DSP chip TMS320F2812 has a word length of 32 bits, high data calculation precision and strong system processing capacity. How to use the DSP chip to control the turn-off of the thyristor can be realized based on the prior art.
In order to avoid the situations of collapse, jump errors and the like of a software program of the low-current grounding line selection device, a hardware watchdog circuit is designed, and the watchdog circuit mainly adopts a reset chip MAX706 of Meixin company containing 8 external pins. The microprocessor is connected with a watchdog circuit, and the watchdog circuit adopts a reset chip MAX706 and peripheral circuits thereof, as shown in FIG. 9.
The first and second current transformers may be the same current transformer, and the distinction is only for convenience of description.
Generally, a common vacuum contactor is usually used for a fast switch, a current limiting resistor Rk is arranged between the vacuum contactor and the ground, and the addition of the current limiting resistor Rk can influence the line selection accuracy to a certain extent. Therefore, the embodiment adopts the quick vacuum switch based on the electromagnetic repulsion mechanism as the quick switch, and is characterized by quick action, reduction or even no addition of the current limiting resistor Rk, thus the current signal change is large, and the line selection accuracy is higher.
Regarding the measurement of zero sequence voltage, the three-phase voltage transformer is connected with the branch in parallel and connected into an open triangle, and the outlet of the open triangle is the zero sequence voltage.
Regarding the measurement of the zero sequence current, all three live wires pass through the inner hole of the current transformer, and the vector sum of the three-phase current, namely the zero sequence current, is measured.
The output signals of the voltage transformer and the current transformer can be input into the microprocessor only through preprocessing, and the preprocessing comprises filtering processing through a low-pass filter circuit and analog-to-digital conversion through an AD conversion circuit.
As shown in fig. 10, the low-pass filter circuit is designed to use two reverse-connected voltage regulators at the input end of the analog signal, and has a design function of limiting the voltage and amplitude of the analog input signal and preventing the sudden serial impact voltage from damaging the analog signal acquisition circuit, thereby damaging the whole circuit. Meanwhile, a second-order analog low-pass filter is designed in the signal conditioning circuit, an operational amplifier LM324 is used in the filter, and the application process shows that the filter has good filter characteristics of a pass band and a stop band, and particularly has a good effect of processing power frequency component interference of a power grid.
The output of the signal conditioning circuit is analog, so that an analog-to-digital converter must be used in the electronic circuit design of the high-current fault line selection system of the resonant grounding system to convert the analog output signal of the signal conditioning circuit into a digital signal, namely, a signal which can be recognized and processed by a back-end microprocessor. The analog-to-digital converter adopted in the embodiment is a 14-bit analog-to-digital converter MAX125 which is an 8-channel analog-to-digital converter, and when the number of signal paths exceeds 8, a plurality of MAX125 chips are connected in parallel.
In order to ensure that the sampling analog signal of the large-current fault line selection system of the resonant grounding system is not distorted, the microprocessor should consider the shannon sampling theorem, that is, the sampling frequency used by the device should be more than or equal to 2 times of the signal frequency, so that the acquisition rate of the large-current fault line selection system of the resonant grounding system is increased, the integrity of the original data of the large-current fault line selection system of the resonant grounding system can be ensured, and the improvement of the line selection accuracy of the large-current fault line selection system of the resonant grounding system can also play an important role.
The microprocessor is connected with a monitoring server through a network, and the monitoring server provides display, alarm and real-time query services. The monitoring service end can be realized based on the existing internet of things technology, and the specific structure and the realization mode of the monitoring service end are not the key points related to the application.
The system comprises a line selection process: 1. after the system has single-phase earth fault, the voltage transformer detects a fault signal and transmits the fault signal to the microprocessor, and the microprocessor reads and stores the zero sequence current of each branch to select the branch with the maximum zero sequence current; 2. the method comprises the following steps that a fast switch (controlled by a microprocessor) is started, a first grounding transformer is grounded, current signals are injected into a system through active grounding of the first grounding transformer (the size and the time of the injected current signals can be controlled through the microprocessor so as to achieve the purpose of not influencing the original state of a grounding point), the injected current signals are transmitted along a grounding loop and finally flow into a single-phase grounding fault point, the microprocessor reads and stores zero-sequence currents of all branches again, and the branch with the largest zero-sequence current is selected; 3. selecting a branch with the maximum zero-sequence current change by comparing current signals detected by zero-sequence current transformers of the branches before and after active grounding; 4. if the three selected branches are the same, the three selected branches are definitely the fault points, and if the three selected branches are different, the fault points need to be further determined according to experience obtained by summarizing a large amount of data or by means of other methods. Generally, when there is no high resistance fault, the branch with the largest zero sequence current change is the accurate fault point.
It is understood that the described embodiments are merely exemplary of the invention, rather than exemplary of the whole, and that those skilled in the art will be able to make various modifications, additions and substitutions to the described embodiments without departing from the spirit of the invention or exceeding the scope of the claims. Based on the embodiments in the present disclosure, all other embodiments obtained by a person of ordinary skill in the art and related fields without creative efforts shall fall within the protection scope of the present disclosure.
Claims (6)
1. A large current fault line selection system of a resonance grounding system, wherein a neutral point is grounded through an arc suppression coil, and the large current fault line selection system is characterized by comprising a voltage transformer for detecting the occurrence of a single-phase grounding fault, a first current transformer for detecting zero sequence current of each branch, a signal conditioning circuit for processing output signals of the voltage transformer and the first current transformer, an AD conversion circuit for converting output analog signals of the voltage transformer and the first current transformer into digital signals, a microprocessor for analyzing the zero sequence current and an active grounding system controlled by the microprocessor;
the active grounding system mainly comprises a first grounding transformer, a quick switch and a second current transformer, wherein the quick switch is connected between a neutral point on the high-voltage side of the first grounding transformer and the ground after being connected in series with the second current transformer, and the quick switch is controlled by the microprocessor;
the arc suppression coil is provided with a secondary winding and is matched with a second grounding transformer, an isolating switch, a damping resistance box and a capacitance compensation cabinet, the isolating switch is connected between the second grounding transformer and the arc suppression coil, and the damping resistance box is connected between the arc suppression coil and the ground; the capacitance compensation cabinet mainly comprises a capacitor bank, a thyristor bank, a fuse and a fan, thyristors are reversely connected in parallel and then are connected in series with the capacitors to form a compensation branch, a plurality of compensation branches, the fuse and the fan are all connected in parallel to the secondary winding side of the arc suppression coil, and the thyristors are controlled by the microprocessor;
the quick switch adopts a quick vacuum switch based on an electromagnetic repulsion mechanism; the microprocessor is connected with a monitoring server through a network, and the monitoring server provides display, alarm and real-time query services.
2. The large-current fault line selection system of the resonant grounding system as claimed in claim 1, wherein the signal conditioning circuit is a low-pass filter circuit, and the input terminal of the signal conditioning circuit is connected with a voltage-limiting and amplitude-limiting circuit composed of two voltage-stabilizing diodes connected in series in an opposite direction.
3. The large current fault line selection system of the resonant grounding system as claimed in claim 1, wherein the AD conversion circuit employs a 14-bit analog-to-digital converter MAX125 and its peripheral circuits.
4. The high current fault line selection system of the resonant grounding system of claim 1, wherein the microprocessor employs a DSP chip TMS320F2812 and its peripheral circuits.
5. The large current fault line selection system of the resonant grounding system as claimed in claim 4, wherein said microprocessor is connected with a watchdog circuit, and said watchdog circuit employs a reset chip MAX706 and its peripheral circuits.
6. A high current fault routing system of a resonant grounding system as in claim 1 wherein said grounding transformer is connected in parallel with a surge protector.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111896889A (en) * | 2020-07-10 | 2020-11-06 | 国网湖北省电力有限公司电力科学研究院 | Arc grounding fault transient analysis method for resonance grounding system |
| CN113156251A (en) * | 2021-04-26 | 2021-07-23 | 珠海菲森电力科技有限公司 | Ground fault simulation experiment table for non-effective grounding system |
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2019
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111896889A (en) * | 2020-07-10 | 2020-11-06 | 国网湖北省电力有限公司电力科学研究院 | Arc grounding fault transient analysis method for resonance grounding system |
| CN113156251A (en) * | 2021-04-26 | 2021-07-23 | 珠海菲森电力科技有限公司 | Ground fault simulation experiment table for non-effective grounding system |
| CN113156251B (en) * | 2021-04-26 | 2024-03-29 | 珠海菲森电力科技有限公司 | Ground fault simulation experiment table for non-effective grounding system |
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