Controllable discharge lightning arrester

Abstract

The invention provides a controllable discharge lightning arrester which is used for solving the technical problem that the protection voltage is too high when weak insulation equipment is protected due to the fact that the protection voltage level of an existing metal oxide lightning arrester cannot be controlled and adjusted. The invention discloses a controllable discharge lightning arrester. Two ends of a second voltage limiting element MOV2 are connected in parallel with combined gaps G1-G3-G2 and a control loop; the third electrode G3 of the combined gap G1-G3-G2 is located between the first electrode G1 and the second electrode G2, and a first gap G1-G3 and a second gap G2-G3 which are equal in length are formed; a first branch circuit formed by connecting a first reactor L1 and a first current-limiting resistor R1 in series in the control loop is connected with first gaps G1-G3 in parallel; the second reactor L2 is connected in series with the controller K, then is connected in parallel with the capacitor C, and then is connected in series with the second current-limiting resistor R2 to form a second branch which is connected in parallel with the combined gap G1-G3-G2. The combined gap G1-G3-G2 is controlled through the first branch and the second branch, so that the protection level of the lightning arrester is controlled and adjusted.

Description

Technical Field

[0001] The invention relates to a lightning arrester, in particular to a controllable discharge lightning arrester. Background Art

[0002] Metal oxide surge arresters are important protective devices that are widely used in limiting overvoltage protection of power systems because they can prevent insulation components of electrical equipment from being damaged due to overvoltage. However, the protection voltage level of existing metal oxide surge arresters cannot be controlled and adjusted, resulting in the protection voltage being too high when protecting weakly insulated equipment. Summary of the invention

[0003] The purpose of the present invention is to solve the technical problem that the protection voltage level of the existing metal oxide lightning arrester cannot be controlled and adjusted, resulting in the protection voltage being too high when protecting weak insulation equipment, and to provide a controllable discharge lightning arrester so that the protection voltage level of the lightning arrester can be controlled and adjusted.

[0004] In order to achieve the above purpose, the technical solution provided by the present invention is:

[0005] A controllable discharge arrester, which is special in that it comprises a first voltage limiting element MOV1 and a second voltage limiting element MOV2 connected in series;

[0006] A controllable discharge gap is arranged in parallel at both ends of the second voltage limiting element MOV2;

[0007] The controllable discharge gap includes a combined gap G1-G3-G2 and a control loop;

[0008] The combined gap G1-G3-G2 is composed of a first electrode G1, a second electrode G2 and a third electrode G3; the first electrode G1 is connected to one end of the second voltage limiting element MOV2 and the first voltage limiting element MOV1, and the second electrode G2 is connected to the other end of the second voltage limiting element MOV2;

[0009] The third electrode G3 is located between the first electrode G1 and the second electrode G2. A first gap G1-G3 is formed between the first electrode G1 and the third electrode G3, and a second gap G2-G3 is formed between the second electrode G2 and the third electrode G3. The lengths of the first gap G1-G3 and the second gap G2-G3 are equal.

[0010] The control loop includes a first reactor L1, a second reactor L2, a capacitor C, a first current limiting resistor R1, a second current limiting resistor R2 and a controller K;

[0011] The first reactor L1 is connected in series with the first current limiting resistor R1 to form a first branch, and the first branch is connected in parallel with the first gap G1-G3;

[0012] The second reactor L2 is connected in series with the controller K, the series circuit is connected in parallel with the capacitor C, and the parallel circuit is connected in series with the second current limiting resistor R2 to form a second branch, and the second branch is connected in parallel with the combined gap G1-G3-G2;

[0013] The inductance ratio N of the first reactor L1 and the second reactor L2 is greater than 1.

[0014] Furthermore, the controller K is a switch device.

[0015] Furthermore, the controller K is a power electronic device.

[0016] Furthermore, N=10.

[0017] Furthermore, the combined gap G1-G3-G2 adopts a flat plate gap.

[0018] Furthermore, the combined gap G1-G3-G2 adopts a horn gap.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. A controllable discharge lightning arrester provided by the present invention has a controllable discharge gap connected in parallel at both ends of a second voltage limiting element MOV2, and a combined gap G1-G3-G2 in the controllable discharge gap is set to a combined gap with a length equal to that of the first gap G1-G3 and the second gap G2-G3, and the combined gap G1-G3-G2 is controlled by the first branch and the second branch in the control loop, that is, the terminal voltage and the discharge voltage of the combined gap G1-G3-G2 are controlled by controlling the on-voltage of the controller K, so as to realize the control and adjustment of the protection level of the lightning arrester, and can reduce the protection voltage level of the lightning arrester when protecting weak insulation equipment.

[0021] 2. Based on a controllable discharge arrester provided by the present invention, the controller adopts power electronic devices, which can realize accurate control of the conduction voltage, thereby enabling the discharge voltage of the combined gap G1-G3-G2 to achieve high-precision controlled discharge in a narrow range.

[0022] 3. The controllable discharge arrester provided by the present invention has a combined gap G1-G3-G2 that can break the power frequency continuous current by using an ordinary flat gap or a horn gap, and has a simple structure and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a circuit diagram of a controllable discharge arrester. DETAILED DESCRIPTION

[0024] In order to make the advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] A controllable discharge arrester, such as Figure 1 As shown, the arrester of the present invention comprises a first voltage limiting element MOV1 and a second voltage limiting element MOV2 connected in series, and the protection level of the arrester is equal to the sum of the protection levels of the first voltage limiting element MOV1 and the second voltage limiting element MOV2. Wherein, a controllable discharge gap is arranged in parallel at both ends of the second voltage limiting element MOV2, and the protection level of the second voltage limiting element MOV2 is controlled and adjusted by the controllable discharge gap.

[0026] The controllable discharge gap includes a combined gap G1-G3-G2 and a control loop.

[0027] The combined gap G1-G3-G2 is composed of a first electrode G1, a second electrode G2 and a third electrode G3; the third electrode G3 is located between the first electrode G1 and the second electrode G2, a first gap G1-G3 is formed between the first electrode G1 and the third electrode G3, and a second gap G2-G3 is formed between the second electrode G2 and the third electrode G3; since the lengths of the first gap G1-G3 and the second gap G2-G3 are equal in the present invention, that is, the spacing between the first electrode G1 and the third electrode G3 is equal to the spacing between the second electrode G2 and the third electrode G3, the discharge voltages of the first gap G1-G3 and the second gap G2-G3 are also substantially equal. The combined gap G1-G3-G2 in the present invention can adopt an ordinary flat plate gap or a horn gap, which has a simple structure and strong practicality.

[0028] The control loop includes a first reactor L1, a second reactor L2, a capacitor C, a first current limiting resistor R1, a second current limiting resistor R2 and a controller K. The first reactor L1 is connected in series with the first current limiting resistor R1 to form a first branch, and the first branch is connected in parallel with the first gap G1-G3; the second reactor L2 is connected in series with the controller K, the series circuit is connected in parallel with the capacitor C, and the parallel circuit is connected in series with the second current limiting resistor R2 to form a second branch, and the second branch is connected in parallel with the combined gap G1-G3-G2. The inductance ratio N of the first reactor L1 and the second reactor L2 can be taken as needed, and the principle of taking the value of N is to ensure that the combined gap G1-G3-G2 can be discharged; in this embodiment, the value of N is 10. The controller K is a switching device, such as a discharge tube, a thyristor, an IGBT, a mechanical switch, etc.

[0029] The implementation principle of a controllable discharge arrester of the present invention is:

[0030] When the controller K is not conducting, the voltage Uk across the controller K is equal to the voltage Uc across the capacitor C. Under the condition that the leakage current of the second current limiting resistor R2 can be ignored, the voltage Uc across the terminals of the second current limiting resistor R2 isR2 =0. Therefore, the voltage between the terminals of the second voltage limiting element MOV2 is equal to the voltage between the terminals of the controller K and the capacitor C, that is, U MOV2 =U K =U C .

[0031] At the moment when the controller K is turned on, the voltage of the capacitor C cannot change suddenly, so the voltage U of the second reactor L2 L2 Forced to be equal to U C At the same time, the voltage U of the first reactor L1 L1 Equal to N times the voltage U of the second reactor L2 L2 ,Right now

[0032] U L1 =N*U L2 =N*U C =N*U K (1)

[0033] At the same time, before the combined gap G1-G3-G2 discharges, no current flows through the branch of the first reactor L1, and the voltage U L1 Equal to the terminal voltage U of the gap G1-G3 G1-G3 , that is,

[0034] U G1-G3 =U L1 (2)

[0035] When U G1-G3 When the discharge voltage of the gap G1-G3 is reached, the gap G1-G3 discharges and conducts. At the same time, since the third electrode G3 is located at the center of the first electrode G1 and the second electrode G2, the discharge voltage U of the gap G2-G3 is G2-G3 Equal to the discharge voltage U of the gap G1-G3 G1-G3 , that is, the combined gap G1-G3-G2 breaks down and discharges. Therefore, the discharge voltage of the combined gap G1-G3-G2 can be expressed by the following formula:

[0036] U G1-G3-G2 =U G2-G3 =U G1-G3 =U L1 =N*U K (3)

[0037] According to formula (3), it can be seen that the discharge voltage of the combination gap G1-G3-G2 can be controlled by controlling the on-voltage of the controller K, and the ratio of the two voltages is equal to the inductance ratio N of the first reactor L1 and the second reactor L2. Since the discharge voltage of the combination gap G1-G3-G2 is equal to N times the voltage Uk across the controller K, the larger the value of N, the smaller the influence of the dispersion of the voltage Uk across the controller K and the dispersion of the discharge of the combination gap G1-G3-G2 on the discharge of the combination gap G1-G3-G2. In other words, the lower limit of the voltage Uk across the controller K and the lower limit of the discharge voltage of the combination gap G1-G3-G2 after multiplying by N are much larger than the lower limit of the discharge voltage of the combination gap G1-G3-G2. Therefore, even if the voltage Uk across the controller K and the discharge of the combination gap G1-G3-G2 have a certain dispersion, the discharge of the combination gap G1-G3-G2 can still be ensured. However, the value of N cannot be too large, as a too large value will increase the volume of the first reactor L1 . Therefore, in this embodiment, the value of N is 10.

[0038] Generally, the discharge voltage of the combined gap G1-G3-G2 has a certain dispersion, therefore, the controller K in the present invention preferably adopts power electronic devices, which can realize the precise control of the conduction voltage. It can be seen from formula (3) that the terminal voltage of the combined gap G1-G3-G2 can be controlled within the accuracy range of the controller K, therefore, the discharge voltage of the combined gap G1-G3-G2 can realize high-precision control discharge in a narrow range.

[0039] The following takes a 10.5kV generator as an example to illustrate the relevant parameters and principles of the above-mentioned lightning arrester that provides protection for it.

[0040] The rated voltage of the generator is 10.5kV, and its power frequency withstand voltage is 2*10.5+1=22kVr.ms. The operating voltage and lightning withstand voltage can generally be taken as the peak value of the power frequency withstand voltage, that is, 22*√2=31kVcrest.

[0041] The continuous operating voltage of the lightning arrester protecting the generator should be 1.1*1.15*10.5=13.3kVr.ms, which is 1.1 times the maximum line voltage. Its rated voltage should be 1.25 times the continuous operating voltage, that is, 1.25*13.3=16.6kVr.ms. Compared with the parameters of the 10kV distribution type lightning arrester in GB11032, the rated voltage and continuous operating voltage of the product in this example are 17kVr.ms and 13.6kVr.ms respectively. According to GB11032, a traditional gapless metal oxide lightning arrester is used, and its DC 1mA reference voltage and residual voltage are 24kV and 45kV respectively. Because the residual voltage of the lightning arrester (45kV) is greater than the insulation level of the generator (31kV), it cannot provide effective insulation protection for the latter. In order to solve this problem, a controllable discharge lightning arrester provided by the present invention is used to perform insulation protection on the generator in this example, and its principle and parameter determination are as follows:

[0042] The DC 1mA reference voltage of the whole machine is still 24kV, and the DC reference voltages of the first voltage limiting element MOV1 and the second voltage limiting element MOV2 are allocated according to the following parameters: U MOV1-1mA =16kV, U MOV2-1mA =8kV.

[0043] According to the voltage ratio characteristics of the metal oxide nonlinear resistor, the residual voltage of the whole machine is still 45kV, and the 5kA lightning residual voltage of the first voltage limiting element MOV1 and the second voltage limiting element MOV2 are respectively not greater than the following parameters: U MOV1-5kA ≤30kV, U MOV2-5kA ≤15kV.

[0044] Discharge voltage of combined gap G1-G3-G2: 10-12 kV.

[0045] Controller K uses IGBT, which is turned on when the voltage between its terminals reaches 9kV.

[0046] The inductance value of the second reactor L2 is 12 mH, the inductance value of the first reactor L1 is 120 mH, and N=10.

[0047] Capacitor C is a film capacitor with a capacitance of 1.6pF and a rated voltage of 12kV. The capacitive reactance of the capacitor should be at least 10 times the impedance of the second voltage limiting element MOV2 and be able to withstand the maximum voltage between the terminals of the combined gap.

[0048] The first current limiting resistor R1 and the second current limiting resistor R2 are metal oxide nonlinear resistors of the same specification as the second voltage limiting element MOV2, with a DC reference voltage of 800V and a 2ms square wave current carrying capacity of 400A.

[0049] The residual voltage of the first voltage limiting element MOV1 and the second voltage limiting element MOV2 is divided according to the DC 1mA reference voltage. When the voltage across the arrester reaches 27kV, the terminal voltages of the first voltage limiting element MOV1 and the second voltage limiting element MOV2 are 18kV and 9kV respectively. The controller K can be triggered to conduct when the voltage reaches 9kV, which makes the terminal voltage of the first reactor L1 reach a maximum of 90kV and causes the terminal voltage of the combined gap G1-G3-G2 to break down and conduct when it rises to 10-12kV, so that the first reactor L1 and the second voltage limiting element MOV2 are bypassed, and the terminal voltage of the lightning arrester is limited to 28kV-30kV, with the lower limit value being the sum of the terminal voltage of the first voltage limiting element MOV1 18kV and the minimum discharge voltage of the combined gap G1-G3-G2 10kV, and the upper limit value being the sum of the terminal voltage of the first voltage limiting element MOV1 18kV and the maximum discharge voltage of the combined gap G1-G3-G2 12kV.

[0050] As the surge current increases, the voltage between the terminals of the arrester is only the residual voltage of the first voltage-limiting element MOV1, and its residual voltage at 5kA is no more than 30kV. Therefore, during the development of overvoltage, the maximum voltage across the arrester never exceeds 30kV, meeting the requirements for generator protection.

[0051] The first voltage-limiting element MOV1 can limit the power-frequency continuous current to no more than 15A. The maximum phase-to-ground voltage of the generator is 1.15*10.5kV=12kVr.ms, with a peak value of 17kVcrest, and its ratio to the DC reference voltage of the first voltage-limiting element MOV1 is 1.07. According to the volt-ampere characteristic of MOV1, the corresponding peak value and effective value of the power-frequency continuous current are approximately 15Acrest and 11A, respectively. Since the power-frequency continuous current is small, ordinary plate gaps and horn gaps can break the power-frequency continuous current, so the combined gaps G1-G3-G2 of the present invention can adopt such ordinary gaps with simple structures.

[0052] The above description is only used to illustrate the technical solution of the present invention rather than to limit it. For ordinary professional and technical personnel in the field, the specific technical solution recorded in the above embodiment can be modified, or some of the technical features therein can be replaced by equivalents, and these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution protected by the present invention.

Claims

1. A controllable discharge arrester, characterized in that: It includes a first voltage limiting element MOV1 and a second voltage limiting element MOV2 connected in series; A controllable discharge gap is arranged in parallel at both ends of the second voltage limiting element MOV2; The controllable discharge gap includes a combined gap G1-G3-G2 and a control loop; The combined gap G1-G3-G2 is composed of a first electrode G1, a second electrode G2 and a third electrode G3; the first electrode G1 is connected to one end of the second voltage limiting element MOV2 and the first voltage limiting element MOV1, and the second electrode G2 is connected to the other end of the second voltage limiting element MOV2; The third electrode G3 is located between the first electrode G1 and the second electrode G2. A first gap G1-G3 is formed between the first electrode G1 and the third electrode G3, and a second gap G2-G3 is formed between the second electrode G2 and the third electrode G3. The lengths of the first gap G1-G3 and the second gap G2-G3 are equal. The control loop includes a first reactor L1, a second reactor L2, a capacitor C, a first current limiting resistor R1, a second current limiting resistor R2 and a controller K; The first reactor L1 is connected in series with the first current limiting resistor R1 to form a first branch, and the first branch is connected in parallel with the first gap G1-G3; The second reactor L2 is connected in series with the controller K, the series circuit is connected in parallel with the capacitor C, and the parallel circuit is connected in series with the second current limiting resistor R2 to form a second branch, and the second branch is connected in parallel with the combined gap G1-G3-G2; The inductance ratio N of the first reactor L1 and the second reactor L2 is greater than 1.

2. A controllable discharge arrester according to claim 1, characterized in that: The controller K is a switch device.

3. A controllable discharge arrester according to claim 2, characterized in that: The controller K is a power electronic device.

4. A controllable discharge arrester according to claim 3, characterized in that: Said N=10.

5. A controllable discharge arrester according to any one of claims 1 to 4, characterized in that: The combined gap G1-G3-G2 adopts a flat plate gap.

6. A controllable discharge arrester according to any one of claims 1 to 4, characterized in that: The combined gap G1-G3-G2 adopts a horn gap.

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