A voltage type arc extinguishing device and system for single-phase grounding fault in distribution network

Abstract

The present invention discloses a voltage-type arc extinguishing device and system for single-phase grounding faults in distribution networks, and belongs to the technical field of relay protection for distribution networks. The voltage-type arc extinguishing device of the present invention comprises a circuit breaker combination, an arc-extinguishing busbar, a voltage-regulating transformer and a four-position switch cabinet, wherein the circuit breaker combination connects the substation busbar and the arc-extinguishing busbar, the voltage-regulating transformer generates a compensation voltage with the same amplitude and opposite direction as the fault phase voltage, one end of which is connected to the arc-extinguishing busbar, and the other end is connected to the four-position switch cabinet, one end of the four-position switch cabinet is connected to the voltage-regulating transformer, and the other end is connected to the system neutral point, and the position of the four-position switch is determined according to the fault detection and fault phase selection device. The present invention provides a novel voltage-type arc extinguishing device, which is configured at the neutral point of the distribution network to clamp the voltage at the fault point and destroy the conditions for the arc to reignite, without an external independent power supply, without power electronic equipment, with high reliability and low cost, and suitable for large-scale promotion and application.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of distribution networks, and in particular relates to a voltage-type arc extinguishing device and system for single-phase grounding faults in distribution networks. Background Art

[0002] The distribution network is the end of the power system, responsible for distributing electric energy and closely connected with users. my country's distribution network usually adopts a small current grounding system, which has the advantage of being able to continue to operate after a single-phase grounding fault occurs, thereby improving power supply reliability. However, with the expansion of the distribution network scale and the increase in the number of cables, the single-phase grounding capacitance current of the distribution network is getting larger and larger, resulting in the failure of the single-phase grounding fault arc of the distribution network to extinguish itself, which in turn causes electrical fires and electric shock accidents. Therefore, it is of great practical significance to study the arc extinguishing problem of single-phase grounding faults in distribution networks.

[0003] The existing distribution network single-phase grounding fault arc extinguishing methods can be divided into two types: current arc extinguishing method and voltage arc extinguishing method. The current arc extinguishing method was first to install an arc extinguishing coil at the neutral point of the distribution network to compensate for the fault current, but with the acceleration of the cable construction of the power grid, the residual current of the fault increases, and it is difficult to achieve natural arc extinguishing. In recent years, some scholars have also proposed a full compensation scheme for fault current based on power electronics technology, but there are problems such as relying on the accurate calculation of the system's ground capacitance and poor equipment reliability and complex control due to the poor over-current and over-voltage capabilities of power electronic equipment. The voltage arc extinguishing method takes the fault phase voltage as the control target, suppresses the phase voltage at the fault point to below the restriking arc voltage, and prevents the arc from reigniting from the source, which is a new development direction. However, it requires the application of power electronic equipment and devices, which is costly and has low reliability, making it difficult to be widely promoted in the distribution network. In addition, the grounding fault phase transfer technology is to directly ground the fault phase busbar through the bypass set in the station to achieve fault arc extinguishing, but it is necessary to artificially create a short-circuit point in the substation, endangering the safety of substation operators.

[0004] In summary, although the single-phase grounding fault arc extinguishing technology in the distribution network has good research and application prospects, there are still some problems. Therefore, it is necessary to further study the single-phase grounding fault arc extinguishing technology in the distribution network. Summary of the invention

[0005] The purpose of the present invention is to provide a voltage-type arc extinguishing device and system for single-phase grounding faults in distribution networks. The voltage at the fault point is clamped to below the arc extinguishing voltage by applying voltage at the neutral point of the distribution network, thereby destroying the conditions for the fault arc to reignite. No external independent power supply is required, and no power electronic equipment and devices are required. The device has high reliability and low cost, and is suitable for large-scale promotion and application.

[0006] In order to achieve the above object, the present invention adopts the following technical solution.

[0007] On the one hand, the present invention provides a voltage-type arc extinguishing device for single-phase grounding faults in a distribution network, the voltage-type arc extinguishing device being applied to a small current grounding system, the voltage-type arc extinguishing device comprising a circuit breaker assembly (1), an arc-extinguishing small busbar (2), a voltage-regulating transformer (3) and a four-position switch cabinet (4); wherein the circuit breaker assembly is used to connect a substation busbar and the arc-extinguishing small busbar, the voltage-regulating transformer generates a compensation voltage with an amplitude equal to that of a fault phase voltage and in an opposite direction, one end of the voltage-regulating transformer is connected to the arc-extinguishing small busbar, and the other end is connected to the four-position switch cabinet, one end of the four-position switch cabinet is connected to the voltage-regulating transformer, and the other end is connected to a neutral point of the distribution network, and the position of the four-position switch is determined according to the results of a fault detection and fault phase selection device.

[0008] Furthermore, the circuit breaker combination includes a circuit breaker, two disconnectors and two grounding switches, one disconnector is configured on each side of the circuit breaker, and the disconnector is configured with a grounding switch.

[0009] Furthermore, the voltage regulating transformer is composed of three four-winding transformers, namely TA, TB and TC; each of the four-winding transformers is provided with a first iron core column (31), a second iron core column (32), a third iron core column (33), a fourth iron core column (34), a first winding (35), a second winding (36), a third winding (37) and a fourth winding (38); the first iron core column and the second iron core column are connected by an iron yoke to form a closed magnetic circuit; the third iron core column and the fourth iron core column are connected by an iron yoke to form another closed magnetic circuit; the ends of the first coil, the second coil and the third coil are connected, and the first section is led out; the end of the fourth coil is grounded, and the first end is led out; the voltage regulating transformer is provided with 12 lead-out terminals, namely: TA1, TA2, TA3, TA4, TB1, TB2, TB3, TB4, TC1, TC2, TC3, TC4.

[0010] Furthermore, the wiring method of the voltage-regulating transformer is as follows: TA1, TA2, and TA3 are respectively connected to the B phase, C phase, and A phase of the arc-extinguishing busbar, and TA4 is connected to the gear I of the four-position switch cabinet; TB1, TB2, and TB3 are respectively connected to the A phase, C phase, and B phase of the arc-extinguishing busbar, and TB4 is connected to the gear II of the four-position switch cabinet; TC1, TC2, and TC3 are respectively connected to the A phase, B phase, and C phase of the arc-extinguishing busbar, and TC4 is connected to the gear III of the four-position switch cabinet.

[0011] Furthermore, the transformation ratio of the four-winding transformer is 1:1:1:2 / 3.

[0012] Furthermore, the position of the four-position switch is determined according to the results of the fault detection and fault phase selection device: when the fault detection device does not detect a fault, the four-position switch is adjusted to the normal position; when the fault detection device detects a fault and the fault phase selection device detects that the fault phase is phase A, the four-position switch is adjusted to position I; when the fault detection device detects a fault and the fault phase selection device detects that the fault phase is phase B, the four-position switch is adjusted to position II; when the fault detection device detects a fault and the fault phase selection device detects that the fault phase is phase C, the four-position switch is adjusted to position III.

[0013] On the other hand, the present invention provides a voltage-type arc extinguishing system for single-phase grounding faults in a distribution network, which specifically includes a fault detection device, a fault phase selection device and a voltage-type arc extinguishing device. The fault detection device is used to detect the fault, the fault phase selection device is used to determine the fault phase, and the voltage-type arc extinguishing device is used to generate a voltage opposite to the fault phase and inject it into the neutral point of the small current grounding system.

[0014] The beneficial effects of the present invention are:

[0015] 1. Compared with the existing arc suppression coil, the present invention can reduce the voltage between the fault point and the ground to below the arcing voltage or the safety voltage without calculating the system capacitance to the ground. On the one hand, it can prevent the arc from reigniting at the source, and on the other hand, it can ensure the personal safety of personnel.

[0016] 2. Compared with the flexible arc extinguishing technology, the present invention does not require power electronic equipment and devices, has low cost and high reliability, does not require an external power supply, and has no capacity limitation.

[0017] 3. Compared with the ground fault phase transfer technology, there is no need to artificially create short-circuit points in the substation, which can reduce the impact on the power grid.

[0018] 4. The present invention can be used in situations with Z-type grounding transformers, and can also be directly used at the neutral point of a star-type transformer, and has a wide range of applications.

[0019] To sum up, the present invention combines the characteristics of distribution network operation to provide a voltage-type arc extinguishing device and system for single-phase grounding faults in distribution networks. The voltage at the fault point is clamped by applying voltage at the neutral point, thereby destroying the conditions for the restrike of the fault arc. No external independent power supply is required, and no power electronic equipment and devices are required. It has high reliability and low cost, and is suitable for large-scale promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to better understand the above technical scheme, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art, and the accompanying drawings of the present invention are as follows.

[0021] Figure 1 It is a circuit diagram of the present invention and a schematic diagram of access to a power distribution network.

[0022] Figure 2 This is a structural diagram of the core and winding of the voltage regulating transformer of the present invention.

[0023] Figure 3 It is the output voltage vector diagram of the voltage regulating transformer of the present invention.

[0024] Figure 4 This is a waveform diagram of the output voltage of the voltage regulating transformer and the voltage of the fault phase (phase A) in embodiment 1 of the present invention.

[0025] Figure 5 This is a diagram showing the voltage waveform and effective value change at the fault point before and after the device is put into operation in Example 1 of the present invention.

[0026] Figure 6 This is a diagram showing the current waveform and effective value change at the fault point before and after the device is put into operation in Example 1 of the present invention.

[0027] Figure 7 This is a waveform diagram of the output voltage of the voltage regulating transformer and the voltage of the fault phase (phase B) in embodiment 2 of the present invention.

[0028] Figure 8 This is a diagram showing the voltage waveform and effective value change at the fault point before and after the device is put into operation in Example 2 of the present invention.

[0029] Fig. 9 This is a diagram showing the current waveform and effective value change at the fault point before and after the device is put into operation in Example 2 of the present invention.

[0030] In the figure, 1-circuit breaker combination, 2-arc extinguishing busbar, 3-voltage regulating transformer, 4-four-position switch cabinet, 31-first iron core column, 32-second iron core column, 33-third iron core column, 34-fourth iron core column, 35-first winding, 36-second winding, 37-third winding, 38-fourth winding. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] The purpose of the present invention is to provide a voltage-type arc extinguishing device and system for single-phase grounding faults in distribution networks, which clamps the voltage at the fault point to below the arc extinguishing voltage by applying voltage at the neutral point, destroys the conditions for the fault arc to reignite, does not require an external independent power supply, does not require power electronic equipment and devices, has high reliability and low cost. The present invention is further described below in conjunction with specific embodiments.

[0033] Embodiment 1: This embodiment is based on Figure 1 According to the structure diagram shown, a distribution network simulation model is built in the PSCAD / EMTDC electromagnetic transient simulation software. There are 5 outgoing lines on the 10 kV side of the 110 kV substation, of which there are 3 overhead lines with lengths of L1=15 km, L3=20 km and L4=18 km respectively; there are 2 cable lines with lengths of L2=15 km and L5=20 km respectively. Figure 1 and Figure 2 The structure diagram shown and Figure 3 The voltage vector diagram shown in the figure shows that the voltage type arc extinguishing device of the present invention is built and connected to the neutral point of the distribution network. A single-phase grounding fault is set to occur on the L3 line, the fault point is set at 15km away from the substation, the fault phase is set to phase A, the fault transition resistance is 500 ohms, and the fault occurrence time is set to 0.4s. After the fault occurs, the substation fault detection device detects the fault, and the substation fault phase selection device determines that the fault phase is phase A.

[0034] The device of the present invention receives the information provided by the substation relay protection, and at 1s, adjusts the four-position switch to position I. The device of the present invention generates a voltage with the same amplitude and opposite direction as the fault phase voltage, such as Figure 4 After the device of the present invention is put into use, the effective value of the voltage at the fault point gradually decreases from 5.39kV after the fault to 32V. Figure 5 At the same time, after the device of the present invention is put into use, the effective value of the current at the fault point gradually decreases from 10.8A after the fault to 0.1A, as shown in Figure 6 The device of the present invention can reduce the voltage and current of the fault point, destroy the conditions for the fault arc to reignite, and extinguish the single-phase grounding fault arc of the distribution network.

[0035] Embodiment 2: This embodiment is based on Figure 1According to the structure diagram shown, a distribution network simulation model is built in the PSCAD / EMTDC electromagnetic transient simulation software. There are 5 outgoing lines on the 10 kV side of the 110 kV substation, including 3 overhead lines with lengths of L1=15 km, L3=20 km and L4=18 km, and 2 cable lines with lengths of L2=15 km and L5=20 km. Figure 1 and Figure 2 The structure diagram shown and Figure 3 As shown in the schematic diagram, the voltage type arc extinguishing device of the present invention is built and connected to the neutral point of the distribution network. A single-phase grounding fault is set to occur in the L3 line, the fault point is set at 15km away from the substation, the fault phase is set to phase B, the fault transition resistance is 8000 ohms, and the fault occurrence time is set to 0.4s. After the fault occurs, the substation fault detection device detects the fault, and the substation fault phase selection device determines that the fault phase is phase B.

[0036] The device of the present invention receives the information provided by the substation relay protection, and at 1 second, adjusts the four-position switch to position II. The device of the present invention generates a voltage with the same amplitude and opposite direction as the fault phase voltage, such as Figure 7 After the device of the present invention is put into use, the effective value of the voltage at the fault point gradually decreases from 5.95kV after the fault to 34V. Figure 8 At the same time, after the device of the present invention is put into use, the effective value of the current at the fault point gradually decreases from 0.8A after the fault to 0.02A, as shown in Fig. 9 The device of the present invention can reduce the voltage and current of the fault point, destroy the conditions for the fault arc to reignite, and extinguish the single-phase grounding fault arc of the distribution network.

[0037] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principle and purpose of the present invention. The protection scope of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. Each implementation scheme within its scope shall be subject to the constraints of the present invention.

Claims

1. A voltage type arc extinguishing device for single-phase grounding fault in distribution network, characterized by: The voltage-type arc extinguishing device is applied to a small current grounding system, and comprises a circuit breaker assembly (1), an arc extinguishing busbar (2), a voltage regulating transformer (3) and a four-position switch cabinet (4); wherein the circuit breaker assembly is used to connect the substation busbar and the arc extinguishing busbar, and the circuit breaker assembly comprises a circuit breaker, two disconnectors and two grounding switches, and an disconnector is arranged on each side of the circuit breaker, and the disconnector is arranged with a grounding switch; the voltage regulating transformer generates a voltage with an amplitude equal to that of the fault phase and a direction opposite to that of the fault phase. The voltage regulating transformer is composed of three four-winding transformers, namely TA, TB and TC; the four-winding transformer is provided with a first iron core column (31), a second iron core column (32), a third iron core column (33), a fourth iron core column (34), a first winding (35), a second winding (36), a third winding (37) and a fourth winding (38); the first iron core column and the second iron core column are connected by an iron yoke to form a closed magnetic circuit; the third iron core column and the fourth iron core column are connected by an iron yoke to form another A closed magnetic circuit; the ends of the first winding, the second winding and the third winding are connected, and the first section is led out; the end of the fourth winding is grounded, and the first end is led out; the voltage regulating transformer is provided with 12 lead-out terminals, namely: TA1, TA2, TA3, TA4, TB1, TB2, TB3, TB4, TC1, TC2, TC3, TC4, one end of the voltage regulating transformer is connected to the arc-extinguishing small busbar, and the other end is connected to the four-station switch cabinet; one end of the four-station switch cabinet is connected to the voltage regulating transformer, and the other end is connected to the system neutral point. The position of the workstation switch is determined according to the results of the fault detection and fault phase selection device: when the fault detection device does not detect a fault, the four-position switch is adjusted to the normal position; when the fault detection device detects a fault and the fault phase selection device detects that the fault phase is phase A, the four-position switch is adjusted to position I; when the fault detection device detects a fault and the fault phase selection device detects that the fault phase is phase B, the four-position switch is adjusted to position II; when the fault detection device detects a fault and the fault phase selection device detects that the fault phase is phase C, the four-position switch is adjusted to position III.

2. A voltage-type arc extinguishing device for single-phase grounding fault in distribution network according to claim 1, characterized in that: The wiring method of the voltage regulating transformer is as follows: TA1, TA2, and TA3 are respectively connected to the B phase, C phase, and A phase of the arc-extinguishing busbar, and TA4 is connected to the gear position I of the four-position switch cabinet; TB1, TB2, and TB3 are respectively connected to the A phase, C phase, and B phase of the arc-extinguishing busbar, and TB4 is connected to the gear position II of the four-position switch cabinet; TC1, TC2, and TC3 are respectively connected to the A phase, B phase, and C phase of the arc-extinguishing busbar, and TC4 is connected to the gear position III of the four-position switch cabinet.

3. A voltage-type arc extinguishing device for single-phase grounding fault in distribution network according to claim 1, characterized in that: The transformation ratio of the four-winding transformer is 1:1:1:2 / 3.

4. A voltage type arc extinguishing system for single-phase grounding fault in distribution network, characterized by: The invention comprises connecting the voltage-type arc extinguishing device as described in claims 1 to 3 to a distribution network.

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