Simple capacitor bank differential protection circuit and impulse current generator

Abstract

The invention relates to a large-capacity capacitor bank differential protection circuit and an impulse current generator, the circuit comprising a protection gap G0 branch and a parallel circuit of at least one set of capacitor bank differential circuits, the capacitor bank differential circuit being formed by the parallel connection of two capacitor bank branches; the protection gap G0 branch is a series circuit of a protection gap G0 and a fault current discharge resistor R0, two output terminals of the secondary windings of the current transformers CT1 and CT2 are respectively CT 1，4 and CT 1，5 and CT 2，4 and CT 2，5 ; the protection gap G0 is composed of a spherical or hemispherical first metal electrode, a second metal electrode and a needle-shaped metal electrode; the first ports of the capacitor banks C1 and C2 are connected to the first metal electrode, the second ports are connected to the ground through the primary windings of CT1 and CT2 respectively, the needle-shaped metal electrode is connected to the ground through R0, the output terminal CT 1，4 is connected to the needle-shaped metal electrode, the output terminal CT 1，5 is connected to the output terminal CT 2，5 , and the output terminal CT 2，4 is connected to the second metal electrode. The beneficial effects are simple manufacturing and no use of integrated circuits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power equipment, in particular to a simple capacitor bank differential protection circuit and an impulse current generator. BACKGROUND

[0002] The impulse current generator with capacitors as energy storage elements is applied in the power operation department and the electrical manufacturing department to test the impact current resistance of zinc oxide arrester valve, lightning arrester, down conductor, etc. The output current amplitude of the impulse current generator in this application scenario often reaches more than 100 kA; the output current amplitude in the field of nuclear physics, accelerator, laser, etc. can even reach the order of MA. In order to generate the required output current of 100 kA-MA (100 kA to MA) and improve the steepness of the output current, a large number of capacitors are usually used in parallel, and at the same time, the length of the capacitor discharge circuit must be minimized in the design to reduce the inductance of the circuit. If the internal insulation of a capacitor (the capacitor is referred to as a fault capacitor) is damaged during use, the energy stored in other normal capacitors connected in parallel with the fault capacitor will be released to the fault capacitor in a very short time, which is easy to cause the fault capacitor to rupture or even explode, thereby causing serious safety accidents. Therefore, ensuring that the capacitor does not explode when it fails is one of the key indicators for designing an impulse current generator. At present, the following three protection measures are generally used:

[0003] 1) The capacitors are grouped, and a large-capacity energy-absorbing resistor is connected in series at the high-voltage output end of each group of capacitors. When the capacitors fail, most of the energy stored in other normal capacitors will be consumed in the energy-absorbing resistor; for a capacitor bank with a large capacity, the structure of the energy-absorbing resistor is complex, and the presence of the energy-absorbing resistor in the circuit will cause the output current amplitude to be smaller. This capacitor protection method reduces the efficiency of the capacitor,

[0004] 2) The capacitors are grouped, and a fuse is connected in series at the high-voltage output end of each group of capacitors. When a fault occurs, the capacitor protection is realized by fusing the fuse. The existing fuse has poor action sensitivity, and the fusing characteristics of the fuse are greatly different under different current amplitudes and waveforms, and there is a problem of difficulty in replacing the fuse after fusing.

[0005] 3) The capacitors are grouped, and the protection of the capacitor bank is realized through a differential protection device. The large-capacity high-voltage capacitors used in the impulse current generator are often arranged in multiple parallel branches, and each branch has one or several capacitors, and the total capacitance of each branch is equal to each other. When the capacitor in any branch fails, it will cause the capacitance between the branch and other branches to be unequal. Figure 1 is a schematic diagram of a large-capacity capacitor bank adjacent branch single current transformer differential protection impulse current generator circuit in the prior art. Figure 2is a schematic diagram of an impact current generator circuit of a prior art large-capacity capacitor bank adjacent branch double current transformer differential protection. As shown in the accompanying Figure 1 , accompanying Figure 2 , in order to detect whether the capacitor in operation has a fault, the existing differential protection device; wherein Figure 1 CT i is a current transformer, the first branch current and the second branch current pass through the current transformer in opposite directions (i.e. the current directions are opposite), and the output of the current transformer is the difference between the two branch currents. Figure 2 CT i is a current transformer, two current transformers with the same characteristics are wound on each capacitor bank grounding lead, and the current transformers between adjacent two capacitor banks are connected into a differential protection circuit. The transformers of the above two devices need to be connected to a trigger pulse device, after the trigger pulse device receives the differential signal, a high-voltage pulse is output to the protection gap, the gap is broken down, and the capacitor bank discharges through the gap to play a protection role. According to the differential protection circuit of Figure 1 , since the adjacent branch currents need to pass through the current transformer in opposite directions, the connection line of each branch discharge circuit is too long, which increases the inductance of the discharge circuit and reduces the current amplitude and the steepness of the waveform, and at the same time, the conductor connection of the discharge circuit is difficult. According to the differential protection circuit of Figure 2 , each branch needs to have two current transformers or needs to have a double-winding current transformer; such a protection circuit is complex, the large differential signal collection system makes it difficult to obtain high reliability for this protection circuit, and the high cost also makes it difficult for this technology to be widely used. The impact current generator will generate a very strong electromagnetic interference signal when discharging, and the existing trigger pulse device mostly has an integrated circuit, which is easy to be disturbed in a strong electromagnetic environment, resulting in unstable output signal and even damage.

[0006] The function of a current transformer (CT) is to convert a large primary current into a small secondary current through a certain transformation ratio for protection and measurement purposes. The winding (turns N1) connected to the measured and protected current is called the primary winding (or primary winding, primary winding), and the winding (turns N2) connected to the measurement and protection circuit is called the secondary winding (or secondary winding, secondary winding). The protection gap is a simple lightning protection device composed of two metal electrodes.

[0007] The application number is 201810514818.3, the applicant is Hunan Xiangdian Test Research Institute Co., Ltd., and the application name is a controllable protection gap under large current and an application method thereof. The controllable protection gap under large current comprises a gap component, a pulse generating device, a current transformer and a measurement and control unit. The gap component is composed of two hemispherical electrodes. The two hemispherical electrodes form a protection main gap, and at least one of the hemispherical electrodes is provided with a spark electrode arranged towards the other hemispherical electrode and connected in conduction. The output end of the pulse generating device is connected in conduction with the spark electrode. The two hemispherical electrodes are connected in parallel at two ends of a protected high-voltage electrical equipment. The current transformer is arranged on a current loop of the protected high-voltage electrical equipment, and the output end of the current transformer is connected with the measurement and control unit. The output end of the measurement and control unit is connected with the control end of the pulse generating device. The controllable discharge gap protection function with high reliability and without control dead zone can be provided for low impedance electrical equipment under large current.

[0008] The application utilizes the prior art and improves the capacitor bank differential protection circuit in view of the technical problems of the impulse current generator.

SUMMARY

[0009] The application aims to provide a large-capacity capacitor bank differential protection circuit which is simple to manufacture and does not use integrated circuits.

[0010] To achieve the above-mentioned purpose, the application adopts the technical scheme of a simple capacitor bank differential protection circuit, which comprises a protection gap G0 branch and a parallel circuit of at least one capacitor bank differential circuit. The capacitor bank differential circuit is composed of two capacitor bank branches in parallel. The protection gap G0 branch is a series circuit of a protection gap G0 and a fault current discharge resistor R0. The two capacitor bank branches are a series circuit of a capacitor bank C1 and a current transformer CT1 and a series circuit of a capacitor bank C2 and a current transformer CT2. Two output ends of secondary windings of the current transformer CT1 and the current transformer CT2 are respectively CT 1,4 and CT 1,5 and CT 2,4 and CT 2,5 . The protection gap G0 is composed of a spherical or hemispherical first metal electrode, a second metal electrode and a needle-shaped metal electrode arranged towards the first metal electrode on the spherical surface of the second metal electrode. The first port of the capacitor bank C1 and the first port of the capacitor bank C2 are connected with the first metal electrode, and the second ports are connected with the ground through the primary windings of the current transformer CT1 and the current transformer CT2 respectively. The needle-shaped metal electrode is connected with the ground through the fault current discharge resistor R0. The output end CT 1,4 is connected with the needle-shaped metal electrode, the output end CT 1,5 is connected with the output end CT 2,5 , and the output end CT 2,4The second metal electrode is connected.

[0011] Preferably, the capacitor banks C1 and C2 have equal capacitance, the current transformers CT1 and CT2 have the same size and shape, the gap between the first metal electrode and the first metal electrode is determined according to the charging voltage of the capacitor, and there is a 0-2mm gap filled with insulating medium between the first metal electrode and the needle-shaped metal electrode.

[0012] Preferably, the insulating medium filled between the first metal electrode and the needle-shaped metal electrode is air.

[0013] Preferably, the current transformers CT1 and CT2 include secondary windings, a core, and a frame, a shell, and a terminal, the secondary windings are directly and uniformly wound on a circular ring-shaped core made of silicon steel sheet, the core is fixed on the frame, and is installed in the shell, the secondary windings are led out through the terminal, and a current-carrying wire passes through the center of the circular ring-shaped core to act as a primary winding.

[0014] Preferably, when the capacitor bank discharges an impulse current signal, either capacitor bank C1 or C2 of any capacitor bank differential circuit is fault-free, the capacitor bank branch currents of the fault-free capacitor bank have the same direction and equal size, the induced potential generated by the current transformers CT1 and CT2 cancels out, and the protection gap G0 does not act; when either capacitor bank C1 or C2 of any capacitor bank differential circuit is faulty, the capacitor in the fault-free capacitor bank discharges to the faulty capacitor, the current in the faulty capacitor bank branch and the current in the normal capacitor bank branch have opposite directions, the induced potential generated by the current transformers CT1 and CT2 superimposes on each other, the gap between the second metal electrode and the needle-shaped metal electrode of the protection gap G0 breaks down under the action of the induced potential, generates a strong electric spark, causes gas ionization, and reduces the insulation performance to cause the gap between the first metal electrode and the second metal electrode of the protection gap G0 to break down.

[0015] Preferably, when the capacitor bank discharges a 500A 8 / 20μs waveform impulse current signal, the distance of the gap between the second metal electrode and the needle-shaped metal electrode of the protection gap G0 is 1mm.

[0016] Another object of the present application is to provide a large-capacity capacitor bank differential protection impulse current generator which is simple to manufacture and does not use integrated circuits.

[0017] To achieve the above-mentioned further purpose, the technical scheme adopted by the present application is a simple capacitor bank differential protection impact current generator, comprising the simple capacitor bank differential protection circuit mentioned above, and further comprising an ignition ball gap G, the capacitor bank branch further comprises a wave adjustment resistor for adjusting the output current waveform, the first port of the wave adjustment resistor is connected to the first port of the capacitor bank, the second port of the wave adjustment resistor is connected to the first port of the ignition ball gap G and the first metal electrode, and the second port of the ignition ball gap G is connected to the load.

[0018] Preferably, the number of groups of the capacitor bank is an even number 2N groups, which are divided into N groups of capacitor bank differential circuits, each group of capacitor bank differential circuit comprising two transformers CT 2j-1 and CT 2j , the two output ends of the secondary windings of which are CT 2j-1,4 and CT 2j-1,5 , and CT 2j,4 and CT 2j,5 , wherein j≤N, the output end CT 2j-1,4 is connected to a needle-shaped metal electrode, the output end CT 2j-1,5 is connected to the output end CT 2j,5 , the output end CT 2j,4 is connected to the second metal electrode.

[0019] Preferably, the number of groups of the capacitor bank is an odd number 2N+1 groups, the 1st to 2Nth groups of capacitor bank form N groups of capacitor bank differential circuits; the 2Nth and 2N+1th groups of capacitor bank form one group of capacitor bank differential circuit, the circuit transformer CT 2N and the current transformer CT 2N+1 , the two output ends of the secondary windings of which are CT 2N,4 and CT 2N,5 , and CT 2N+1,4 and CT 2N+1,5 , the output end CT 2N,4 is connected to the second metal electrode, the output end CT 2N,5 is connected to the output end CT 22+1,5 , the output end CT 2N+1,4 is connected to a needle-shaped metal electrode.

[0020] The simple capacitor bank differential protection circuit and impact current generator have the following beneficial effects: simple to manufacture and without using integrated circuits, capable of reducing the action time delay of differential protection and improving the anti-interference ability of control signals, and having obvious practicality and economy. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic diagram of an impact current generator circuit of a prior art large-capacity capacitor bank adjacent branch single current transformer differential protection.

[0022] Figure 2 is a schematic diagram of an impact current generator circuit of a prior art large-capacity capacitor bank adjacent branch double-current transformer differential protection.

[0023] Figure 3 is a schematic diagram of a protection gap structure of a simple capacitor bank differential protection circuit.

[0024] Figure 4 is a schematic diagram of a simple capacitor bank differential protection circuit fault-free capacitor simulation principle.

[0025] Figure 5 is a schematic diagram of a simple capacitor bank differential protection circuit fault capacitor simulation principle.

[0026] Figure 6 is a current waveform diagram and an output voltage waveform diagram of a simple capacitor bank differential protection circuit simulation circuit when a 500A 8 / 20μs waveform impact current signal is injected through the current transformer CT1.

[0027] Figure 7 is a current waveform diagram and an output voltage waveform diagram of a simple capacitor bank differential protection circuit simulation circuit when a 500A 8 / 20μs waveform impact current signal is injected through the current transformer CT2.

[0028] Figure 8 is a total output voltage waveform diagram of a simple capacitor bank differential protection circuit fault-free capacitor simulation circuit when a 500A 8 / 20μs waveform impact current signal is injected through the current transformer CT1 and the current transformer CT2.

[0029] Figure 9 is a total output voltage waveform diagram of a simple capacitor bank differential protection circuit fault capacitor simulation circuit when a 500A 8 / 20μs waveform impact current signal is injected through the current transformer CT1 and the current transformer CT2.

[0030] Figure 10 is a circuit principle diagram of a simple capacitor bank differential protection impact current generator when a fault-free capacitor is present.

[0031] Figure 11 is a circuit principle diagram of a simple capacitor bank differential protection impact current generator when a first capacitor bank branch fault capacitor is present.

[0032] The reference signs and components involved in the drawings are shown as follows: 1, first metal electrode, 2, second metal electrode, 3, needle-shaped metal electrode.

DETAILED DESCRIPTION

[0033] The present application is further described below in conjunction with examples and with reference to the accompanying drawings.

[0034] Example 1

[0035] This embodiment implements a simple differential protection circuit for capacitor banks.

[0036] This embodiment presents a simple differential protection circuit for capacitor banks, which can reliably activate the protection gap of the capacitor bank when an individual capacitor malfunctions, providing high-reliability protection for large-capacity capacitor banks.

[0037] This embodiment presents a simple capacitor bank differential protection circuit, including a protection gap G0 branch and a parallel circuit of at least two capacitor bank branches. The protection gap G0 branch is a series circuit of the protection gap G0 and the fault current discharge resistor R0. The two capacitor bank branches are a series circuit of capacitor bank C1 and current transformer CT1, and a series circuit of capacitor bank C2 and current transformer CT2. The total capacitance of capacitor bank C1 and capacitor bank C2 is equal, and current transformers CT1 and CT2 are identical in size and shape.

[0038] Figure 3 This is a schematic diagram of the protective gap structure in a simple capacitor bank differential protection circuit. (See attached diagram.) Figure 3 As shown in the figure, this embodiment presents a simple differential protection circuit for a capacitor bank. The protection gap G0 is composed of a spherical or hemispherical first metal electrode 1, a spherical or hemispherical second metal electrode 2, and a needle-shaped metal electrode 3 arranged on the spherical surface of the second metal electrode 2 facing the first metal electrode 1. The first metal electrode 1 and the first metal electrode 2 of the protection gap G0 are separated by a certain distance, which is determined according to the charging voltage of the capacitor. There is a 1-2 mm gap between the first metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0, and the gap is filled with an insulating medium (generally air). Furthermore, a high-voltage trigger pulse is applied to both ends of the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0, causing the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0 to break down, resulting in a discharge. As a result, a high-density metal vapor plasma is generated in the protection gap G0 and is rapidly injected into the gap between the first metal electrode 1 and the second metal electrode 2 of the protection gap G0, leading to a discharge.

[0039] The current transformers CT1 and CT2 include secondary windings, a core, a frame, a housing, and terminals. The secondary windings are directly and evenly wound on a circular iron core, which is fixed to the frame and housed within the housing. The secondary windings are led out through the terminals. The secondary windings themselves do not have a primary winding; the current-carrying (load current) conductor passes through the center of the circular iron core made of silicon steel sheets, acting as the primary winding. The two output terminals of the secondary windings are defined as CT1 and CT2 respectively. 1,4 and CT 1,5 CT scan 2,4 and CT 2,5 .

[0040] The output CT of the current transformer CT1 of the simple capacitor bank differential protection circuit of the embodiment 1,4 The output CT of the current transformer CT1 of the simple capacitor bank differential protection circuit of the embodiment 1,5 The output CT of the current transformer CT2 of the simple capacitor bank differential protection circuit of the embodiment 2,5 The output CT of the current transformer CT2 of the simple capacitor bank differential protection circuit of the embodiment 2,4 The second metal electrode 2 of the protection gap G0 is connected with the output CT of the current transformer CT1 and CT2, which generates induced potential for providing high voltage pulse to the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0. The second metal electrode 2 of the protection gap G0 is connected with the output CT of the current transformer CT1 and CT2, which generates induced potential for providing high voltage pulse to the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0. 1,4 The output CT of the current transformer CT1 and CT2 is connected with the second metal electrode 2 of the protection gap G0, and the needle-shaped metal electrode 3 of the protection gap G0 is connected with the first port of the fault current discharge resistor R0 and the ground of the second port of the fault current discharge resistor R0, respectively, which is used to ensure that the breakdown of the trigger pulse with positive and negative polarity can occur on the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0. 2,4 The output CT of the current transformer CT1 and CT2 is connected with the second metal electrode 2 of the protection gap G0, and the needle-shaped metal electrode 3 of the protection gap G0 is connected with the first port of the fault current discharge resistor R0 and the ground of the second port of the fault current discharge resistor R0, respectively, which is used to ensure that the breakdown of the trigger pulse with positive and negative polarity can occur on the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0. 2,4 The output CT of the current transformer CT1 and CT2 is connected with the second metal electrode 2 of the protection gap G0, and the needle-shaped metal electrode 3 of the protection gap G0 is connected with the first port of the fault current discharge resistor R0 and the ground of the second port of the fault current discharge resistor R0, respectively, which is used to ensure that the breakdown of the trigger pulse with positive and negative polarity can occur on the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0.

[0041] If the capacitor bank C1 and the capacitor bank C2 are fault-free, the current directions in the grounding leads are the same, the current sizes are approximately equal, the induced potential generated by each current transformer is approximately the same, the induced potential generated by the current transformer CT1 and CT2 cancels each other out, and there is no or minimal pressure difference between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0, the protection gap G0 does not act. If the capacitor bank C1 or the capacitor bank C2 is faulty, the capacitor in the fault-free capacitor bank will discharge to the faulty capacitor, the current direction in the grounding lead of the faulty capacitor is opposite to that in the grounding lead of the normal capacitor, the induced potential generated by the current transformer CT1 and CT2 superimposes each other, in this case, the protection gap G0 will break down according to the following process: the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0 breaks down under the action of the induced potential, a very strong electric spark is generated when the gap breaks down, which causes gas ionization, and the insulation performance decreases after gas ionization, leading to the breakdown of the gap between the first metal electrode 1 and the second metal electrode 2 of the protection gap G0.

[0042] Figure 4 It is a simple capacitor bank differential protection circuit without fault capacitor simulation principle diagram. Figure 5 It is a simple capacitor bank differential protection circuit with fault capacitor simulation principle diagram. As shown in Figure 4 , and Figure 5As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 4 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 5 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 6 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 6 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 7 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 7 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank.

[0043] Figure 4 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 8 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 8 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank.

[0044] Figure 5 As shown, the output current of the impulse current generator is used to output a 500A 8 / 20μs waveform to simulate the discharge current of capacitor bank C1 and capacitor bank C2, and the current transformers CT1 and CT2 are connected to the load current conductor L1L2 to simulate the two conditions of no fault and fault of the capacitor bank. Figure 9is a simple capacitor bank differential protection circuit fault capacitor analog circuit in 500A8 / 20μs waveform impact current signal injection when the total output voltage waveform flowing through current transformer CT1 and current transformer CT2. As shown in the attached Figure 9 , in this working condition, 500A8 / 20μs waveform when the total output voltage waveform of current transformer CT1 and current transformer CT2, the output voltage reaches the peak value of 12.08kV at 2.62μs, the protection gap G0 second metal electrode 2 and the needle-shaped metal electrode 3 between the gap distance is 1mm, the output voltage can let the protection gap G0 second metal electrode 2 and the needle-shaped metal electrode 3 between the gap discharge, at this time can be observed the protection gap G0 first metal electrode 1 and the second metal electrode 2 between the gap breakdown phenomenon.

[0045] In terms of function, the simple capacitor bank differential protection circuit of the embodiment does not have an integrated circuit chip, has strong anti-interference ability, fast action time and high sensitivity. These characteristics realize the high reliability of the protection device.

[0046] Embodiment 2

[0047] The embodiment realizes a simple capacitor bank differential protection impact current generator.

[0048] The simple capacitor bank differential protection impact current generator of the embodiment can make the protection gap of the capacitor bank reliably act when an individual capacitor is abnormal, and is used for high reliability protection of the impact current generator large-capacity capacitor bank.

[0049] The simple capacitor bank differential protection impact current generator of the embodiment includes a parallel circuit of a protection gap G0 branch and a plurality of capacitor bank branches. The protection gap G0 branch is a series circuit of a protection gap G0 and a fault current discharge resistor R0, and the capacitor bank branch is a series circuit of a capacitor bank C i , a wave modulation resistor R i and a current transformer CT i . The total capacitance of the capacitor bank C i is equal to each other, and the size and shape of the current transformer CT i are the same.

[0050] Figure 3 A simple capacitor bank differential protection circuit protection gap structure diagram. As shown in the attached Figure 3As shown, the simple capacitor bank differential protection impulse current generator of the embodiment is composed of a spherical or semi-spherical first metal electrode 1, a spherical or semi-spherical second metal electrode 2 and a needle-shaped metal electrode 3 arranged on the spherical surface of the second metal electrode 2 towards the first metal electrode 1. The first metal electrode 1 and the second metal electrode 2 of the protection gap G0 are separated by a certain distance, which is determined according to the charging voltage of the capacitor, and there is a 1-2 mm gap between the first metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0, which is filled with an insulating medium (generally air). Further, a high-voltage trigger pulse is applied to both ends of the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0, the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0 is broken down, resulting in discharge, which in turn generates high-density metal vapor plasma in the protection gap G0 and rapidly injects into the gap between the first metal electrode 1 and the second metal electrode 2 of the protection gap G0, resulting in discharge.

[0051] Figure 10 The circuit schematic diagram of the simple capacitor bank differential protection impulse current generator when there is no fault capacitor. Figure 11 The circuit schematic diagram of the simple capacitor bank differential protection impulse current generator when there is a fault capacitor in the first capacitor bank branch. In the figure, G is the ignition sphere gap, G0 is the protection gap, R i is the wave adjustment resistance (used to adjust the output current waveform), C i is the capacitor bank (consisting of one or more capacitors), R0 is the fault current discharge resistance, CT i is the current transformer, where i is a positive integer. As shown in the accompanying Figure 10 , the accompanying Figure 11 , the simple capacitor bank differential protection impulse current generator of the embodiment is connected in the following manner: the capacitor bank C i port 7 is connected to the wave adjustment resistance R i port 8, the capacitor bank C i port 6 is grounded, the wave adjustment resistance R i port 9 is connected to the ignition sphere gap G port 10 and the first metal electrode 1 of the protection gap G0; the ignition sphere gap G port 11 is connected to the load port 14, and the load port 15 is grounded; the protection gap G0 needle-shaped metal electrode 3 is connected to the fault current discharge resistance R0 port 12, and the fault current discharge resistance R0 port 13 is grounded.

[0052] The current transformer CT iThe system includes a secondary winding, a core, a frame, a housing, and terminals. The secondary winding is directly and evenly wound around a toroidal core, which is fixed to the frame and housed within the housing. The secondary winding is led out through the terminals. Its structure does not include a primary winding; the current-carrying (load current) conductor passes through the center of the toroidal core made of silicon steel sheets, acting as the primary winding. The two output terminals of the secondary winding are defined as CT. i,4 and CT i,5 This embodiment describes a simplified capacitor bank differential protection circuit using an impulse current generator and a current transformer (CT). i-1 Output CT i-1,4 Connect the protective gap G0 needle-shaped metal electrode 3, current transformer CT i-1 Output CT i-1,5 Current transformer (CT) i Output CT i,5 Current transformer CT i Output CT i,4 The second metal electrode 2 of the protective gap G0 is connected. The induced electromotive force generated by the two current transformers in the same group is used to provide a high-voltage pulse to the gap between the second metal electrode 2 of the protective gap G0 and the needle-shaped metal electrode 3.

[0053] When there is no capacitor bank fault and the impulse current generator is discharging, in this embodiment of a simple capacitor bank differential protection impulse current generator, the current direction in each grounding lead is the same, the current magnitude is approximately equal, the induced electromotive force generated by each current transformer is approximately the same, the induced electromotive force generated by the two current transformers in the same group cancels each other out, there is no voltage difference or the voltage difference is extremely small between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0, and the protection gap G0 does not operate.

[0054] When a capacitor in a capacitor bank fails, and the inrush current generator discharges, the capacitors in other capacitor banks will discharge to the faulty capacitor. The current in the grounding lead of the faulty capacitor is greater than the current in the grounding lead of the normal capacitor, and the directions are opposite. The induced electromotive forces generated by the two current transformers in the same bank are superimposed. In this case, the protective gap G0 will break down according to the following process: the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protective gap G0 breaks down under the action of the induced electromotive force. When the gap breaks down, a strong electric spark is generated, causing gas ionization. After the gas is ionized, the insulation performance decreases, leading to the breakdown of the gap between the first metal electrode 1 and the second metal electrode 2 of the protective gap G0.

[0055] The protective gap G0, the second metal electrode 2, and CT i-1,4 Connected, the protective gap G0 needle-shaped metal electrode 3 is respectively connected to the CT i,4The structure that the fault current discharge resistance R0 port 12 connects with the second metal electrode 2 of the protection gap G0, and the fault current discharge resistance R0 port 13 connects with the ground, is used to ensure that the breakdown can occur when the positive and negative trigger pulses are applied on the gap between the second metal electrode 2 and the needle-shaped metal electrode 3 of the protection gap G0.

[0056] Specifically, when the number of capacitor groups is even, it is set as 2N groups. The simple capacitor group differential protection impulse current generator of the embodiment comprises 2N current transformers and one protection gap G0. The 2N current transformers are divided into N groups, each group having two current transformers, denoted as CT 2j-1 and CT 2j (j≤N), the output CT 2j-1 of the current transformer CT 2j-1,4 connects with the second metal electrode 2 of the protection gap G0, the output CT 2j-1 of the current transformer CT 2j-1,5 connects with the output CT 2j of the current transformer CT 2j,5 , and the output CT 2j of the current transformer CT 2j,4 connects with the needle-shaped metal electrode 3 of the protection gap G0.

[0057] When the number of capacitor groups is odd, it is set as 2N+1 groups. The simple capacitor group differential protection impulse current generator of the embodiment comprises 2N+1 current transformers and one protection gap G0. The current transformers CT1-CT 2N are connected in the same way as the number of capacitor groups is even. The output CT 2N of the current transformer CT 2N+1 is combined with the output CT 2N of the current transformer CT 2N，4 to form a group, the output CT 2N of the current transformer CT 2N,5 connects with the output CT 2N+1 of the current transformer CT 2N+1，5 , and the output CT 2N+1 of the current transformer CT 2N+1,4 connects with the second metal electrode 2 of the protection gap G0.

[0058] In terms of function, the simple capacitor group differential protection impulse current generator of the embodiment does not have an integrated circuit chip, has strong anti-interference ability, fast action time, and high sensitivity. These characteristics realize high reliability of the protection device.

[0059] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and supplements can be made without departing from the principles of the present application, and these improvements and supplements should also be considered as the protection scope of the present application.

Claims

1. A simple capacitor bank differential protection circuit, characterized by: Including protection gap Parallel circuit of branch and at least one set of capacitor bank differential circuit, the capacitor bank differential circuit is parallelly connected by two-way capacitor bank branch; the protection gap Branch is the protection gap And fault current discharge resistance Series circuit, the two-way capacitor bank branch is capacitor bank And current transformer Series circuit and capacitor bank And current transformer Series circuit, the current transformer And current transformer Two output ends of secondary winding are respectively And And And ; the protection gap It is made of spherical or hemispherical first metal electrode, second metal electrode and needle-shaped metal electrode arranged on the spherical surface of second metal electrode towards first metal electrode; the capacitor bank And capacitor bank First port is connected with first metal electrode, second port is respectively through the current transformer And current transformer Primary winding is grounded, the needle-shaped metal electrode is grounded after passing through fault current discharge resistance , the output end Connects needle-shaped metal electrode, output end Connects output end , output end Connects second metal electrode; When the number of groups of the capacitor banks is even When the number of groups of the capacitor banks is even The capacitor bank differential circuit is divided into and m, two output terminals of the secondary winding are respectively and and and Wherein , the output terminal is connected with the needle-shaped metal electrode, the output terminal is connected with the output terminal is connected with the output terminal is connected with the second metal electrode; When the number of groups of the capacitor bank is odd group, the 1 to group capacitor bank is composed of group capacitor bank differential circuit; the and group capacitor bank is composed of a group of capacitor bank differential circuits, circuit mutual inductor and current transformer Two output terminals of the secondary winding are respectively and and and , the output terminal connects to the second metal electrode, the output terminal connects to the output terminal , the output terminal connects to the needle-shaped metal electrode.

2. A simple capacitor bank differential protection circuit according to claim 1, characterized in that: The capacitor bank And capacitor bank The capacitance is equal, the current transformer And current transformer The size shape configuration is same, the first metal electrode and first metal electrode between gap according to capacitor charging voltage determination, the first metal electrode and needle metal electrode between filling insulating medium 0-2 Gap.

3. A simple capacitor bank differential protection circuit according to claim 2, characterized in that: The insulating medium filled between the first metal electrode and the needle-shaped metal electrode is air. The insulating medium filled between the first metal electrode and the needle-shaped metal electrode is air.

4. A simple capacitor bank differential protection circuit according to claim 3, characterized in that: The current transformer And It comprises a secondary winding, a core and a framework, a shell, a terminal, the secondary winding is directly and uniformly wound on a circular core made of silicon steel sheet, the core is fixed on the framework, is installed in the shell, the secondary winding is led out through the terminal, and the current-carrying wire passes through the center of the circular core to act as a primary winding.

5. A simple capacitor bank differential protection circuit according to claim 4, characterized in that: The capacitor bank of any capacitor bank differential circuit or capacitor bank No fault, the capacitor bank branch current direction is same, the current transformer and The induced potential generated by the protection gap Not act; the capacitor bank of any capacitor bank differential circuit or capacitor bank Fault, the capacitor in the non-fault capacitor bank will discharge to the fault capacitor, the current direction in the fault capacitor bank branch is opposite to that in the normal capacitor bank branch, the current transformer and The induced potential generated by the protection gap The gap between the second metal electrode and the needle-shaped metal electrode is broken down under the action of the induced potential, strong electric sparks are generated, the gas is ionized, and the insulation performance is reduced after the gas ionization, leading to the protection gap The gap between the first metal electrode and the second metal electrode is broken down.

6. A simple capacitor bank differential protection circuit according to claim 5, characterized in that: The capacitor bank is performed 500 Waveform impulse current signal discharge, protection gap The distance between the second metal electrode and the needle-shaped metal electrode is 1 .

7. A simple capacitor bank differential protection impulse current generator characterized by: A simple capacitor bank differential protection circuit as claimed in any one of claims 1 to 6, further comprising a spark gap between the firing balls , the capacitor bank branch further comprising a wave shaping resistor for shaping the output current waveform, the wave shaping resistor first port connected to the capacitor bank first port, the wave shaping resistor second port connected to the spark gap , the spark gap , the first port and the first metal electrode, between the second port and ground.

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