Automatic switching grounding mode complete device and automatic switching grounding method thereof

Abstract

The present invention relates to a complete set of automatic switching grounding mode equipment and an automatic switching grounding method thereof. It solves the problems of the existing single neutral node grounding mode. It comprises a controller, which is respectively connected in parallel with a resistor grounding structure, a gap grounding structure, a direct grounding structure and an arc extinguishing coil grounding structure. The resistor grounding structure comprises a controllable small resistor formed by a small resistor and a vacuum contactor in series. The direct grounding structure comprises an isolating switch for controlling the direct grounding of the neutral point of the power grid, and the isolating switch is connected with an electric operating mechanism. The advantages are: a grounding mode combining arc extinguishing coil grounding, small resistor grounding and non-grounding mode is adopted, which can be selected by users according to the operation conditions of the power grid, a small resistor is connected in parallel with the arc extinguishing coil, an isolating switch and the primary side of the gap, and the controller controls the adjustment of the arc extinguishing coil, the switching of the small resistor and the separation and combination of the isolating switch to realize the selection of several grounding modes.

Description

Technical Field

[0001] The invention belongs to the technical field of power supply equipment, and in particular relates to an automatic switching grounding mode complete device and an automatic switching grounding method. Background Art

[0002] At present, most of China's 6kV~35kV distribution networks adopt small current grounding and neutral point ungrounding, that is, neutral point non-effective grounding and neutral point ungrounding. With the acceleration of urban construction, the urban framework continues to expand, and the scale of urban medium-voltage power grids has also increased. In addition, with the large-scale adoption of power cable lines in recent years, the capacitive current level of the medium-voltage power grid system has increased sharply, which has brought some problems to the operation of the power grid. Single-phase grounding causes faults and abnormalities in the medium-voltage power grid, which are characterized by multiple, shielding, extensive, unpredictable and diverse. It should be highly valued, find out the causes and formulate measures to solve them. There are several main neutral point grounding methods for medium-voltage distribution networks, including small resistance grounding, arc suppression coil grounding, and ungrounded. These grounding methods have their own advantages and disadvantages. For example, arc suppression coil grounding has problems such as unchanged adjustment and low intelligence.

[0003] In order to solve the problems existing in the prior art, people have conducted long-term exploration and proposed various solutions. For example, a Chinese patent document discloses an arc extinguishing coil device and an arc extinguishing method thereof [application number: 201510732831.2], wherein the arc extinguishing coil device includes an arc extinguishing coil, one end of the arc extinguishing coil is grounded, and the other end is electrically connected to one end of a switch module, and the other end of the switch module is the output end; it also includes a parallel resistor, one end of the parallel connection is grounded, and the other end is connected to one end of the parallel input switch, and the other end of the parallel input switch is connected to the output end. When the present invention is put into use, the output end is connected to the neutral point of the power grid. When a single-phase grounding occurs in the power grid, the switch module quickly connects the arc extinguishing coil to the neutral point when the capacitive current of the power grid increases, and quickly reduces the asymmetric voltage of the power grid. After the arc extinguishing coil is connected for a period of time, when the zero-sequence voltage in the power grid is not zero, the parallel input switch is closed to connect the parallel resistor to the neutral point to eliminate the zero-sequence voltage.

[0004] The above solution solves the problem of inconvenient adjustment of the existing neutral point grounding method to a certain extent, but the solution still has the problem that the grounding method is single and multiple grounding methods cannot be selected according to the operation conditions of the power grid. Summary of the invention

[0005] The object of the present invention is to provide a complete set of automatic switching grounding mode devices with simple and reasonable structure and multiple grounding mode combinations in order to solve the above problems.

[0006] Another object of the present invention is to provide an automatic switching grounding method with simple operation and high automation level in order to solve the above-mentioned problem.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical solutions: the automatic switching grounding mode complete set of equipment includes a controller, characterized in that the controller is respectively connected in parallel with a resistor grounding structure, a gap grounding structure, a direct grounding structure and an arc suppression coil grounding structure, the resistor grounding structure includes a controllable small resistor formed by a small resistor and a vacuum contactor in series, the direct grounding structure includes an isolating switch for controlling the direct grounding of the neutral point of the power grid, and the isolating switch is connected to an electric operating mechanism connected to the controller and used to realize the closing and opening of the isolating switch.

[0008] In the above-mentioned automatic switching grounding mode complete set of equipment, the arc suppression coil grounding structure includes a turn-adjustable arc suppression coil, and the turn-adjustable arc suppression coil is respectively provided with a number of taps, and each tap corresponds to a different number of turns, and each tap is provided with an on-load electric switch that can realize on-load switching gears and thus change the inductive current.

[0009] In the above-mentioned complete set of automatic switching grounding mode devices, the small resistor is made of stainless steel alloy, and the small resistor is connected to the controller.

[0010] In the above-mentioned automatic switching grounding mode complete set, the gap grounding structure includes a discharge gap connected in parallel with the controller, at least one vacuum contactor is connected in series on the gap circuit of the discharge gap, and the controller is connected to the vacuum contactor, and the vacuum contactors are all connected to the lightning arrester.

[0011] In the above-mentioned complete set of automatic switching grounding mode devices, a plurality of parallel resistors are sequentially connected to the turn-adjusting arc-extinguishing coil, and the parallel resistors are connected to thyristor components.

[0012] In the above-mentioned automatic switching grounding mode complete set, the turn-adjusting arc-extinguishing coil is connected to the voltage transformer, the voltage transformer is connected to the primary connection bar through the isolating switch, and the primary connection bar is connected to the grounding transformer.

[0013] In the above-mentioned complete set of automatic switching grounding mode devices, the discharge gap is connected to the current transformer via a resistor.

[0014] In the above-mentioned complete set of automatic switching grounding mode devices, the number of taps on the said turn-adjusting arc-extinguishing coil is 5-25.

[0015] The automatic switching grounding method of the above-mentioned automatic switching grounding mode complete set is as follows: The automatic switching grounding method is characterized in that the method includes:

[0016] A. Arc suppression coil and small resistor combined grounding method: When a ground fault occurs in the distribution network, the arc suppression coil grounding structure and the resistor grounding structure are combined into a set of devices to detect the capacitance current value of the power grid to calculate the inductance current that needs to be compensated, and control the arc suppression coil to output the compensation current;

[0017] B. Combine gap grounding and direct grounding into one grounding method: The gap grounding structure and the direct grounding structure belong to the large current grounding system. They are directly grounded through the neutral point. When a single-phase grounding fault occurs, the grounding short-circuit current is very large, causing the circuit breaker to trip and eliminate the fault.

[0018] Compared with the existing technology, the advantages of the automatic switching grounding mode complete device and the automatic switching grounding method are: simple structure, using a grounding mode that combines arc extinguishing coil grounding, small resistor grounding and non-grounding mode, for users to choose according to the operation of the power grid. A small resistor is connected in parallel with the arc extinguishing coil, the disconnector, and the primary side of the gap, and the controller controls the adjustment of the arc extinguishing coil, the switching of the small resistor, and the opening and closing of the disconnector to realize the selection of several grounding modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of the structure provided by the present invention.

[0020] Figure 2 A structural schematic diagram from another perspective provided by the present invention.

[0021] Figure 3 The present invention provides a block diagram of the principles.

[0022] In the figure, controller 1, resistor grounding structure 2, small resistor 21, vacuum contactor 22, gap grounding structure 3, discharge gap 31, lightning arrester 32, direct grounding structure 4, disconnector 41, electric operating mechanism 42, arc suppression coil grounding structure 5, turn-adjusting arc suppression coil 51, tap 52, on-load electric switch 53, parallel resistor 6, thyristor assembly 7, voltage transformer 8, primary connection bar 81, resistor 9, current transformer 91. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] like Figure 1-3As shown, the automatic switching grounding mode complete set includes a controller 1, which is respectively connected in parallel with a resistor grounding structure 2, a gap grounding structure 3, a direct grounding structure 4 and an arc extinguishing coil grounding structure 5. The resistor grounding structure 2 includes a controllable small resistor formed by a small resistor 21 and a vacuum contactor 22 in series. The direct grounding structure 4 includes an isolating switch 41 for controlling the direct grounding of the neutral point of the power grid. The isolating switch 41 is connected to an electric operating mechanism 42 connected to the controller 1 and used to realize the closing and opening of the isolating switch 41. This design mainly adopts a grounding mode that combines arc extinguishing coil grounding, small resistor grounding and non-grounding mode, which can be selected by users according to the operation of the power grid. A small resistor is connected in parallel with the arc extinguishing coil, the isolating switch and the primary side of the gap, and the controller controls the adjustment of the arc extinguishing coil, the switching of the small resistor and the opening and closing of the isolating switch to realize the selection of several grounding modes.

[0025] The arc extinguishing coil grounding structure 5 includes a turn-adjustable arc extinguishing coil 51, on which a plurality of taps 52 are respectively arranged, and each tap 52 corresponds to a different number of turns, and each tap 52 is provided with an on-load electric switch 53 capable of realizing on-load switching gears to change the inductive current. The arc extinguishing coil grounding is to connect the arc extinguishing coil at the neutral point of the system, and provide an inductive current when a single-phase grounding occurs in the system, so as to compensate for the capacitive grounding current caused at the fault point due to the existence of capacitance in the system, so as to minimize the fault grounding current of the system. The system can still operate for 2 hours with a single-phase grounding fault, so the power supply reliability of the neutral point of the transformer through the arc extinguishing coil grounding method is relatively high, and it is not easy to cause power outages. A small current line selection device can also be configured, and when a single-phase grounding fault occurs, the fault line can be tripped in a short time.

[0026] Among them, the resistance grounding here is to connect a resistor at the neutral point of the system. When single-phase grounding occurs, the fault line will generate a large fault current. The zero-sequence overcurrent protection has good sensitivity and can quickly cut off the grounding line, but the faulty power grid must be cut off within 10s to avoid burning the resistor. When a single-phase fault occurs in a single system, whether it is permanent or transient, it will act on the tripping, so the line trips more times, seriously affecting the normal power supply of the user and reducing the reliability of the power supply. Preferably, the small resistor 21 here is made of stainless steel alloy, and the small resistor 21 is connected to the controller 1.

[0027] Preferably, the gap grounding structure 3 here includes a discharge gap 31 connected in parallel with the controller 1, at least one vacuum contactor 22 is connected in series on the gap circuit of the discharge gap 31, and the controller 1 is connected to the vacuum contactor 22, and the vacuum contactor 22 is connected to the lightning arrester 32. Here, the turn-adjustable arc-extinguishing coil 51 is connected in sequence with several parallel resistors 6, and the parallel resistor 6 is connected to the thyristor component 7, the turn-adjustable arc-extinguishing coil 51 is connected to the voltage transformer 8, the voltage transformer 8 is connected to the primary connection row 81 through the isolating switch 41, and the primary connection row 81 is connected to the grounding transformer 82, and the discharge gap 31 is connected to the current transformer 91 through the resistor 9.

[0028] Furthermore, the grounding transformer here: for the 10kV distribution network, because the transformer winding is △, a grounding transformer is required to create the neutral point. In order to reduce the zero-sequence impedance, the grounding transformer adopts a Z-shaped connection, and should be equipped with appropriate secondary capacity as needed to replace the station transformer. The arc suppression coil is actually a single-phase iron core reactor. The inductance is changed by changing the number of turns of the winding coil, and the inductance is proportional to the square of the number of turns. Therefore, the number of taps 52 on the turn-adjustable arc suppression coil 51 is 5-25. Corresponding to different numbers of turns, the taps are adjusted by an on-load electric switch, which can realize on-load switching of the gear position, thereby changing the inductance current. The control panel outputs a control signal to drive the on-load switch to adjust the size of the arc suppression coil compensation capacitor current. For the parallel gap, a vacuum contactor is connected in series in the gap circuit, and the controller controls the switching of the contactor to realize the use of the gap circuit.

[0029] The automatic switching grounding method includes: A. Arc extinguishing coil and small resistor combined grounding mode: when a grounding fault occurs in the distribution network, the arc extinguishing coil grounding structure 5 and the resistor grounding structure 2 are combined into a set of devices to detect the capacitance current value of the power grid to calculate the inductance current that needs to be compensated, and control the arc extinguishing coil to output the compensation current; generally, after the instantaneous grounding fault is compensated by the inductance current, the arc is extinguished, and the grounding fault is automatically eliminated, then the complete set of devices automatically exits the compensation state, and the system resumes normal operation, thereby avoiding the situation in which the line tripping rate is high due to the immediate tripping when there is a fault in the small resistance grounding mode. If the line grounding fault still exists after the arc extinguishing coil is compensated for 10s, the system can be considered to have a permanent grounding fault, and the complete set of devices will automatically close the vacuum contactor to input the small resistor. At this time, the fault current is large, and the zero-sequence current protection can be activated to cut off the incoming line by tripping the switch. After the small resistor is put into use, the controllable arc extinguishing coil is controlled to exit the compensation. After the fault line is cut off, the system resumes normal operation, and the grounding complete set of devices automatically closes the high-voltage switch to exit the small resistor. The input of the resistor realizes accurate and rapid isolation of the fault, avoiding the expansion of the fault. This grounding device is a comprehensive way of dealing with single-phase grounding faults in the distribution network. For instantaneous line grounding faults, the controllable arc suppression coil outputs compensation, so that the grounding arc can be extinguished quickly, solving the shortcoming of high tripping rate in low-resistance grounding. It is a major improvement on the current low-resistance grounding method.

[0030] B. Combine gap grounding and direct grounding: Gap grounding structure 3 and direct grounding structure 4 belong to large current grounding system, which are directly grounded through neutral point. When single-phase grounding fault occurs, the grounding short-circuit current is very large, causing the circuit breaker to trip and cut off the fault. When gap grounding and direct grounding devices are used, the controller outputs a signal to control the switch.

[0031] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0032] Although this article uses more terms such as controller 1, resistor grounding structure 2, small resistor 21, vacuum contactor 22, gap grounding structure 3, discharge gap 31, lightning arrester 32, direct grounding structure 4, disconnector 41, electric operating mechanism 42, arc extinguishing coil grounding structure 5, turn-type arc extinguishing coil 51, tap 52, on-load electric switch 53, parallel resistor 6, thyristor assembly 7, voltage transformer 8, primary connection bar 81, resistor 9, current transformer 91, etc., it does not exclude the possibility of using other terms. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A complete set of automatic switching grounding mode devices, comprising a controller (1), characterized in that: The controller (1) is respectively connected in parallel with a resistor grounding structure (2), a gap grounding structure (3), a direct grounding structure (4) and an arc extinguishing coil grounding structure (5); the resistor grounding structure (2) comprises a controllable small resistor formed by a small resistor (21) and a vacuum contactor (22) connected in series; the direct grounding structure (4) comprises an isolating switch (41) for controlling the direct grounding of the neutral point of the power grid; the isolating switch (41) is connected to an electric operating mechanism (42) connected to the controller (1) and used to realize the closing and opening of the isolating switch (41); the arc extinguishing coil grounding structure (5) comprises a turn-adjusting arc extinguishing coil (51); the turn-adjusting arc extinguishing coil (51) is respectively provided with a plurality of taps (52), and each tap (52) corresponds to Different numbers of turns, and each tap (52) is provided with an on-load electric switch (53) capable of realizing on-load switching gears and thus changing the inductor current; the small resistor (21) is made of a stainless steel alloy, and the small resistor (21) is connected to a controller (1); a plurality of parallel resistors (6) are sequentially connected to the turn-adjusting arc-extinguishing coil (51), and the parallel resistor (6) is connected to a thyristor component (7); the turn-adjusting arc-extinguishing coil (51) is connected to a voltage transformer (8), and the voltage transformer (8) is connected to a primary connection bar (81) through an isolating switch (41), and the primary connection bar (81) is connected to a grounding transformer (82); the number of taps (52) on the turn-adjusting arc-extinguishing coil (51) is 5-25.

2. The automatic switching grounding mode complete device according to claim 1 is characterized in that: The gap grounding structure (3) comprises a discharge gap (31) connected in parallel with the controller (1), at least one vacuum contactor (22) is connected in series on the gap circuit of the discharge gap (31), and the controller (1) is connected to the vacuum contactor (22), and the vacuum contactors (22) are all connected to the lightning arrester (32).

3. The automatic switching grounding mode complete device according to claim 2 is characterized in that: The discharge gap (31) is connected to a current transformer (91) via a resistor (9).

4. The automatic switching grounding method of the automatic switching grounding mode complete device according to any one of claims 1 to 3, characterized in that: The method includes: A. Arc suppression coil and small resistor combined grounding method: When a ground fault occurs in the distribution network, the arc suppression coil grounding structure (5) and the resistor grounding structure (2) are combined into a set of devices to detect the capacitance current value of the power grid to calculate the inductance current that needs to be compensated, and control the arc suppression coil to output the compensation current; B. Combined grounding method of gap grounding and direct grounding: Gap grounding structure (3) and direct grounding structure (4) belong to large current grounding system. They are directly grounded through the neutral point. When a single-phase grounding fault occurs, the grounding short-circuit current is very large, causing the circuit breaker to trip and eliminate the fault.

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