CN217656252U

CN217656252U - Nonlinear resistance control cabinet

Info

Publication number: CN217656252U
Application number: CN202221438274.5U
Authority: CN
Inventors: 阮法; 郭超; 谭天雷
Original assignee: Anhui Paweier Intelligent Technology Co ltd
Current assignee: Anhui Himat Electrical Equipment Co ltd
Priority date: 2022-06-09
Filing date: 2022-06-09
Publication date: 2022-10-25
Anticipated expiration: 2032-06-09

Abstract

The utility model discloses a nonlinear resistance switch board, the output including a plurality of nonlinear resistors is connected with the input series connection electricity that corresponds current transformer respectively, nonlinear resistor's high-pressure input passes through high-pressure current-limiting fuse and is connected with isolator's end opening, isolator end opening and the female row of three-phase are connected, and the female three-phase circuit that arranges in the three-phase is connected with high frequency voltage sensor respectively. Has the advantages that: in normal operation, the non-linear resistor is in a high-impedance state, the current flowing through the non-linear resistor is very small, and the non-linear resistor is basically in an open circuit state, so that the system is equivalent to a non-grounding state. Therefore, the method has the characteristics of power supply reliability in an ungrounded mode and good safety. If the system has a fault and high-power voltage is caused, the neutral point voltage can be simultaneously increased, the nonlinear resistor immediately responds and is conducted, the voltage is limited in a set range, and the characteristics of low overvoltage level and high line selection accuracy of the effective grounding system are achieved.

Description

Nonlinear resistance control cabinet

Technical Field

The utility model relates to an electric power unit technical field especially relates to a nonlinear resistance switch board.

Background

Grounding modes of power systems are mainly divided into two main types, namely effective grounding and non-effective grounding. Effective grounding includes direct grounding and grounding via a small resistance; non-effective grounding includes ungrounded, grounded through a crowbar coil, and grounded through a high resistance. Non-active grounding system: (1) Ungrounded is mainly used for overhead lines and systems with small networks, and occupies a large proportion in traditional networks in China. The power supply device is low in manufacturing cost, simple in structure and high in power supply reliability and safety. But the overvoltage multiple is high, and the system insulation threat is large. With the increase of cable lines, the grounding capacitance current of the system is larger and larger, and when single-phase grounding occurs, electric arcs are not easy to extinguish, and high overvoltage can be generated. (2) Grounding via a high resistance is mostly used in power plant supply systems. The high resistance plays a role in absorbing electromagnetic energy of resonance and single-phase grounding, the accuracy of line selection is increased, and the power supply reliability and safety are high. But the overvoltage is still high when the single phase is grounded. Systems with large ground capacitance currents are not suitable. (3) The arc suppression coil is grounded and is mainly used for a system with larger grounding capacitance current. It utilizes inductive current to compensate grounding capacitance current, so that the single-phase grounding residual current is small, after zero-crossing, the electric arc can not be reignited, and it has high power supply reliability and safety. However, the overvoltage multiple is high, the accurate tuning difficulty is high, the line selection accuracy is low, the manufacturing cost is high, and the power grid prospective planning is not facilitated. An effective grounding system: the effective grounding of the medium-voltage system is mainly a mode of grounding through a small resistor, the overvoltage level of the medium-voltage system is low, the accuracy rate of line selection is high, and the grounding fault can be quickly found out. But the power supply reliability and safety are poor. When single-phase arc grounding occurs, arc extinction cannot be realized, and the single-phase arc grounding must be immediately tripped. The grounding current is large, the step voltage is high, the personal safety is seriously threatened, and the secondary circuit and the electronic communication equipment are also greatly interfered.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a non-linear resistance switch board, during normal operating, neutral point voltage is very low, and non-linear resistance is the high resistance state, and the electric current wherein of flowing through is very little, is in the state of opening a way basically, and the system is equivalent to ungrounded. Therefore, the method has the characteristics of power supply reliability in an ungrounded mode and good safety. If the system is in failure and high-power voltage is caused, the neutral point voltage is simultaneously increased, the nonlinear resistor is immediately responded and conducted, the voltage is limited within a set range, and the overvoltage of the system is limited to be less than 2 times. At the moment, the system has the characteristics of low overvoltage level and high line selection accuracy of an effective grounding system, and is superior to a mode of grounding through a small resistor.

The technical scheme of the utility model is realized like this:

a nonlinear resistance control cabinet comprises an embedded controller installed on a cabinet door of the control cabinet, wherein the controller comprises a PCI interface sampling card processed by an industrial control system, a DSP digital processor and a high-speed FPGA, transient overvoltage waveforms and transient overvoltage waveforms are analyzed and processed in real time, and overvoltage types and waveform recording are stored and analyzed.

The controller collects and measures high voltage through the high-low transformation ratio of the current transformers;

the output ends of the nonlinear resistors are respectively connected with the input ends of the corresponding current transformers in series and electrically, the high-voltage input ends of the nonlinear resistors are connected with the lower port of the isolating switch through a high-voltage current-limiting fuse, the upper port of the isolating switch is connected with a three-phase bus bar, and three-phase circuits on the three-phase bus bar are respectively connected with a high-frequency voltage sensor and fixed on the inner wall of the control cabinet;

and the operating handle is arranged on the back surface of the control cabinet and is connected with the isolating switch through the control rod, so that the switching-on and switching-off of the isolating switch are realized.

Furthermore, the industrial control system adopts an XP operating system, a 2.0G Dual-core processor and a memory 500G.

Furthermore, the nonlinear resistor is formed by connecting multiple ZnO nonlinear resistors in parallel.

The beneficial effects of the utility model are that: in normal operation, the neutral point voltage is very low, the nonlinear resistor is in a high-resistance state, the current flowing through the nonlinear resistor is very small and basically in an open circuit state, and the system is equivalent to no ground. Therefore, the method has the characteristics of power supply reliability in an ungrounded mode and good safety. If the system is in failure and high-power voltage is caused, the neutral point voltage is simultaneously increased, the nonlinear resistor is immediately responded and conducted, the voltage is limited within a set range, and the overvoltage of the system is limited to be below 2 times. At the moment, the system has the characteristics of low overvoltage level and high line selection accuracy of an effective grounding system, and is superior to a mode of grounding through a small resistor.

When the system resonates, the large capacity of the nonlinear resistor absorbs the resonant energy very quickly. Since the overvoltage is limited to a low level, the characteristic of the transformer is in a linear region and exhibits a high inductive reactance state, so that the resonance disappears.

When the single-phase arc light is grounded in a system mode, the nonlinear resistor absorbs the energy of the grounding charge in time, and simultaneously limits the recovery voltage of an arc way, so that the grounding current is not easy to re-ignite after zero crossing, the arc light is extinguished quickly, and the comprehensive performance is due to an arc suppression coil.

When permanent grounding occurs, the non-linear resistor maintains the phase voltage level, the current flowing in the resistor is small, and the operation can be maintained. And the fault feeder line can be cut off in a delayed mode or quickly by line selection, so that the method is suitable for various different operation requirements.

The system overvoltage level grounded through the nonlinear resistor is limited within an insulation allowable range, the possibility that the insulation of the electrical equipment is impacted by high voltage is reduced, the probability of large faults caused by small faults (such as short-circuit faults caused by single-phase grounding) is also reduced, and the reliability and the safety of power supply are greatly improved.

The nonlinear resistor is a nonlinear resistor group formed by connecting a plurality of ZnO nonlinear resistors in parallel, and the volt-ampere characteristics of each path are completely consistent.

In addition, each phase circuit of the three-phase circuit is connected with a high-frequency voltage sensor, the bandwidth of the high-frequency voltage sensor reaches 20MHz (the common electromagnetic PT can only reach 10KHz, and the high-frequency component of the power grid voltage cannot be collected), the high-frequency voltage sensor has good frequency response, and high-frequency voltage signals can be recorded.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a front view of a nonlinear resistance control cabinet;

FIG. 2 is a schematic diagram of an internal structure of a nonlinear resistance control cabinet;

FIG. 3 is a circuit diagram of a method for analyzing, managing and selecting a neutral point system fault;

FIG. 4 is a schematic diagram of the current-voltage characteristic of a non-linear grounding resistor;

fig. 5 is a waveform diagram of a fault when a small resistor is accessed (ψ =90 °, R =50 Ω);

fig. 6 is a waveform diagram of a fault when a small resistor is accessed (ψ =0 °, R =50 Ω);

fig. 7 is a diagram of a normal waveform at the time of small resistance access (ψ =0 °, R =50 Ω);

fig. 8 is a waveform diagram of a fault when a nonlinear resistor is switched in (ψ =90 °, R =5000 Ω);

fig. 9 is a diagram of a normal waveform when a nonlinear resistor is turned on (ψ =90 °, R =5000 Ω);

FIG. 10 is a permanent ground fault waveform diagram;

FIG. 11 is a graph of an arc ground fault waveform;

FIG. 12 is a graph of the power frequency voltage waveform detected by the high frequency voltage sensor;

FIG. 13 is a graph of the waveform of the high frequency voltage detected by the high frequency voltage sensor;

fig. 14 is a diagram of a divided voltage waveform detected by the high-frequency voltage sensor.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments.

In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.

According to the utility model discloses an embodiment provides a nonlinear resistance switch board.

Referring to fig. 1-2, according to the embodiment of the present invention, the nonlinear resistance control cabinet comprises an embedded controller 2 installed on a door of a control cabinet 1, wherein the controller 2 comprises an industrial control system, a DSP digital processor and a PCI interface sampling card processed by a high-speed FPGA, and analyzes transient and transient overvoltage waveforms in real time, and stores and analyzes overvoltage types and waveform recording;

the controller 2 collects and measures high voltage through the high-low transformation ratio of the current transformers 3;

the output ends of the nonlinear resistors 4 are respectively and electrically connected with the input ends of the corresponding current transformers 3 in series, the high-voltage input ends of the nonlinear resistors 4 are connected with the lower port of an isolating switch 6 through a high-voltage current-limiting fuse 5, the upper port of the isolating switch 6 is connected with a three-phase bus 7, and three-phase circuits on the three-phase bus 7 are respectively connected with a high-frequency voltage sensor 8 and fixed on the inner wall of the control cabinet 1;

and the operating handle 9 is installed on the back surface of the control cabinet 1, and is connected with the isolating switch 6 through an operating rod, so that the closing and opening of the isolating switch 6 are realized.

Furthermore, the nonlinear resistor 4 is formed by connecting multiple ZnO nonlinear resistors in parallel. Screening by adopting a special database, and uniformly pressing and homogenizing; the ZnO-based active protection device has the advantages of quick action response, good steep wave response characteristic, znO active protection and excellent protection performance, and is not influenced by system capacitive current.

A fault analysis, treatment and line selection method for a neutral point system of a nonlinear resistance control cabinet comprises the following steps:

s1: the neutral point of the three-phase circuit is connected with the nonlinear resistor 4 through the isolating switch 6 and is grounded, the isolating switch 6 is electrically connected with the controller 2, the system resonance overvoltage and the arc light overvoltage are judged and managed, and the permanent grounding is carried out to select the line, when the three-phase circuit breaks down, the controller 2 analyzes and judges transient and transient overcurrent and overvoltage waveforms in real time and stores the transient and overvoltage waveforms;

each phase circuit of the three-phase circuit is connected with a high-frequency voltage sensor 8, the high-frequency voltage sensor 8 is electrically connected with the controller 2, and the high frequency, the power frequency and the frequency division of the circuit are monitored, analyzed and judged;

s2: (i) The fault management is carried out through the nonlinear resistor 4, and the fault simulation analysis and the accurate line selection of the three-phase circuit are monitored through the controller 2;

(ii) Detecting the high-frequency, power-frequency and frequency-division simulation oscillograms of the three-phase circuit through a high-frequency voltage sensor 8, and judging the fault type through a controller 2;

s3: the fault type is judged through the fault simulation analysis of the time variation of each current and voltage, and the monitoring, the governing and the line selection are carried out through the controller 2.

When a single-phase grounding fault occurs in a power grid or a stator winding of the generator, additional resistive current is provided for the grounding point, so that the current of the grounding point is changed from capacitive to resistive current, and the generated overvoltage is ensured not to exceed 1.7 times of phase voltage.

In normal operation, the neutral point voltage is very low, the nonlinear resistor is in a high-resistance state, the current flowing through the nonlinear resistor is very small and basically in an open circuit state, and the system is equivalent to no ground. Therefore, the method has the characteristics of power supply reliability in an ungrounded mode and good safety. If the system is in failure and high-power voltage is caused, the neutral point voltage is simultaneously increased, the nonlinear resistor is immediately responded and conducted, the voltage is limited within a set range, and the overvoltage of the system is limited to be below 2 times. At the moment, the system has the characteristics of low overvoltage level and high line selection accuracy of an effective grounding system, and is superior to a mode of grounding through a small resistor.

When the system resonates, the huge energy capacity of the nonlinear resistor absorbs the resonant energy quickly. Since the overvoltage is limited to a low level, the characteristic of the transformer is in a linear region and exhibits a high inductive reactance state, so that the resonance disappears.

When the single-phase arc light is grounded in a system mode, the nonlinear resistor absorbs grounding charge energy in time and limits the recovery voltage of an arc channel, so that the grounding current is not easy to re-ignite after zero crossing, the arc light is extinguished quickly, and the comprehensive performance is due to the arc suppression coil.

The level of the system overvoltage grounded through the nonlinear resistor is limited within an insulation allowable range, the possibility that the insulation of the electrical equipment is impacted by high voltage is reduced, the probability of large faults caused by small faults (such as short-circuit faults caused by single-phase grounding) is also reduced, and the reliability and the safety of power supply are greatly improved.

As shown in fig. 3 and 4, the nonlinear resistor is a nonlinear resistor group formed by parallel connection of multiple ZnO nonlinear resistors, and the current-voltage characteristics of each path are completely consistent. In specific implementation, the capacity can be calculated according to 300%, normal operation can be realized even if the resistor is damaged by more than 50%, and each circuit is connected with a high-voltage current-limiting fuse in series, so that normal operation of the nonlinear resistors is guaranteed.

The nonlinear resistor is connected between a system neutral point and the ground, namely a nonlinear resistor grounding mode is formed, the mode fully utilizes the characteristics of excellent volt-ampere characteristic, huge heat capacity, quick response speed and the like of the nonlinear resistor, the action value of the nonlinear resistor is set at the system phase voltage level, and a good effect is achieved in operation.

As shown in fig. 5-9, the analysis is simulated for the waveform diagram of the fault or normal condition when the resonance is grounded.

Specifically, as shown in fig. 5 to 6, the waveform diagram shows that when the neutral point is grounded via a small resistor (the conventional small resistor grounding method), the resistance R =50 Ω, and when a resonance fault occurs, the system voltage is hardly affected by the fault, and the transient process is short and can be considered as entering the steady state directly. The overvoltage level is low, the accuracy of line selection is high, and the grounding fault can be quickly found out. But the power supply reliability and safety are poor, when single-phase arc grounding occurs, arc extinguishing cannot be carried out, and immediate tripping is required. The grounding current is large, the step voltage is high, the personal safety is seriously threatened, and the secondary circuit and the electronic communication equipment are also greatly interfered.

The waveform of fig. 7 shows that the neutral point voltage is very low, the non-linear resistor 1 is in a high-impedance state, the current flowing through the non-linear resistor is very small, and the non-linear resistor is basically in an open circuit state, and the system is equivalent to no ground.

As shown in fig. 8, when the impedance of the grounding point is relatively large (i.e., the nonlinear resistor is connected in the scheme), the resistance R =5000 Ω, and when a resonance fault occurs, the voltage has a very obvious transition process, which is finished after about 2 power frequency cycle transient processes; no significant high-frequency components of the voltage occur at high or small transition impedances. FIG. 9 is a diagram of normal waveforms when a non-linear resistor is switched in.

Different from the voltage change characteristic, the nonlinear resistor 1 with the neutral point connected has the advantages that the high-frequency component of the current is obviously reduced, the proportion of the capacitive current is obviously reduced, and the attenuated current basically disappears due to the increase of the impedance.

When the system resonates, the large capacity of the non-linear resistor 1 absorbs the resonant energy very quickly. Because the overvoltage is limited to a lower level, the overvoltage is in a high inductive reactance state, and the resonance disappears.

As shown in fig. 10, which is a waveform diagram of a permanent ground fault, when a permanent ground occurs, the non-linear resistor maintains the phase voltage level, the voltage has a very obvious transient process, and the operation can be maintained after about 4 power frequency cycle transient processes are finished. And the fault feeder line can be cut off in a delayed mode or quickly by selecting the line through the controller, so that the method is suitable for various different operation requirements.

As shown in fig. 11, when a single-phase arc is grounded, the nonlinear resistor 1 absorbs the energy of the grounding charge in time and limits the recovery voltage of the arc path, so that the grounding current does not easily re-ignite after zero crossing, the arc is extinguished quickly, and the comprehensive performance is due to the arc suppression coil.

The above, only be the concrete implementation of the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art is in the technical scope of the present invention, according to the technical solution of the present invention and the utility model, the concept of which is equivalent to replace or change, should be covered within the protection scope of the present invention.

Claims

1. A nonlinear resistance control cabinet is characterized by comprising

The embedded controller (2) is arranged on a box door of the control cabinet (1), the controller (2) comprises an industrial control system, a DSP (digital signal processor) and a PCI (peripheral component interconnect) interface sampling card processed by a high-speed FPGA (field programmable gate array), transient overvoltage waveforms and transient overvoltage waveforms are analyzed and processed in real time, and overvoltage types and waveform recording are stored and analyzed;

the current transformers (3) are arranged at the bottom of the control cabinet (1), secondary output ends of the current transformers (3) are electrically connected with an embedded circuit in a secondary chamber, and the controller (2) collects and measures high voltage through the high-low transformation ratio of the current transformers (3);

the output ends of the nonlinear resistors (4) are respectively and electrically connected with the input ends of the corresponding current transformers (3) in series, the high-voltage input ends of the nonlinear resistors (4) are connected with the lower port of an isolating switch (6) through a high-voltage current-limiting fuse (5), the upper port of the isolating switch (6) is connected with a three-phase busbar (7), and a three-phase circuit on the three-phase busbar (7) is respectively connected with a high-frequency voltage sensor (8) and fixed on the inner wall of the control cabinet (1);

the operating handle (9) is installed on the back face of the control cabinet (1) and connected with the isolating switch (6) through the operating rod, and switching-on and switching-off of the isolating switch (6) are achieved.

2. The nonlinear resistance control cabinet according to claim 1, wherein the industrial control system employs an XP operating system, a 2.0G Dual-core processor, and a memory of 500G.

3. A nonlinear resistance control cabinet according to claim 1, characterized in that the nonlinear resistor (4) is formed by parallel connection of multiple ZnO nonlinear resistors.