Self-breakdown gas switch control type low residual voltage lightning arrester

Abstract

The invention discloses a self-breakdown gas switch control type low-residual-voltage lightning arrester which comprises a zinc oxide lightning arrester with a nonlinear resistance characteristic, an assembly formed by connecting a linear resistor and a linear capacitor in series and in parallel, and a self-breakdown gas switch connected with the assembly in parallel. One end of the zinc oxide arrester is connected in series with one end of the linear assembly, the other end of the zinc oxide arrester is connected with high voltage, the other end of the linear assembly is grounded, and the self-breakdown gas switch is connected in parallel with two ends of the linear assembly. According to the invention, the low charge rate of the lightning arrester under the normal working condition can be ensured, so that the long-term operation life of the lightning arrester is prolonged, the reliability of the lightning arrester is improved, and the gas switch can be self-punctured more reliably under the action of the overvoltage, so that the low residual voltage is obtained, and the deep suppression of the overvoltage of a power system is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of lightning arresters, and in particular relates to a self-breakdown gas switch controlled low residual voltage lightning arrester. Background Art

[0002] As voltage levels in ultra-high voltage transmission systems continue to rise, effectively suppressing switching overvoltages has become a key technical challenge for ensuring safe grid operation. Traditional solutions employ a combined protection strategy of circuit breaker closing resistors in parallel with lightning arresters. However, this approach presents significant challenges, including high equipment investment, complex maintenance, and limited operational reliability. Against this backdrop, controllable lightning arresters, with their precise voltage regulation capabilities and dynamic response advantages, are gradually becoming the preferred option for the next generation of overvoltage limitation technology.

[0003] The structure of a controllable arrester consists of the arrester body and a controllable switch. The arrester body is further divided into a controlled section and a fixed section, both of which are composed of varistors. The controllable switch is connected in parallel across the controlled section, forming a control unit. The ratio of the controlled section's rated voltage to the arrester body's rated voltage is called the controllability ratio, generally set at 15%. During normal system operation, the controllable switch is disconnected, and both the controlled and fixed sections of the arrester body bear the continuous operating voltage. This significantly reduces the arrester's operating charge factor (charge factor is 60%-70%) and improves reliability. During transient high-amplitude switching overvoltages, the controllable switch conducts according to the set operating threshold, shorting the controlled section. The arrester's residual voltage drops to that of the fixed section, achieving deep suppression of system switching overvoltages. According to national standards, in UHV systems, the maximum statistical relative-to-ground switching overvoltage along the line should not exceed 1.7 pu, and the maximum statistical relative-to-ground switching overvoltage at a substation should not exceed 1.6 pu.

[0004] Despite the aforementioned advantages, controlled surge arresters still face several challenges, which can be broadly categorized into two categories: limitations of the arrester itself and inherent flaws in the controllable switch. For controllable switches, existing technology approaches fall into three general categories: mechanical, thyristor, and gap. Mechanical switches inherently have closing times on the order of tens of milliseconds, lacking rapid response capabilities and, therefore, failing to address the issue of limiting the depth of switching overvoltages. Thyristors offer fast response speeds, reaching microseconds, and can theoretically be used to limit various switching overvoltages that occur in a system. However, implementing this technology presents two challenges: 1) Thyristors operate under system transient conditions, and their di / dt and du / dt tolerances are the primary limiting factors. To ensure thyristor damage, external limiting measures are required. 2) Due to the low withstand voltage of a single thyristor, applications typically require dozens of thyristors connected in series. Dynamic and static voltage balancing of these series thyristors can easily lead to voltage balancing issues across the entire arrester. The gap type uses a closed or non-closed gas gap as the control element. It does not have di / dt, du / dt tolerance and voltage equalization problems. In addition, lightning arresters with series gaps have long been used and standardized. Therefore, the use of gaps as control elements in controllable lightning arresters has technical advantages and practical basis, and is a more ideal implementation method.

[0005] Gap triggering methods are primarily categorized as externally triggered and self-triggered. Externally triggered gaps have significant limitations. First, in high-voltage operating environments, strong electromagnetic interference can severely impact the transmission reliability of the external trigger control signal, leading to faults such as false triggering or failed operation. Second, this triggering method requires multiple steps, including signal detection, logic analysis, and drive circuitry. The cumulative delays in these steps significantly increase the overall system response time. In contrast, self-triggered gaps trigger conduction by directly detecting voltage changes across the controlled component. This operating mechanism effectively avoids a number of issues faced by external triggering methods. However, the operating voltage of a gap is not a single, fixed value; multiple experimental measurements of the operating voltage exhibit a probabilistic distribution. Furthermore, studies have shown that steeper overvoltage fronts are associated with faster rises in the arrester's operating current, shorter gap triggering delays, and higher operating voltages. Conversely, shallower overvoltage fronts slow the rise in the arrester's operating current, significantly increase the gap triggering delay, and reduce the operating voltage. These findings indicate that the operating voltage of a gap is uncertain.

[0006] In practical applications, we hope that the gap triggering delay is short and the gap action voltage fluctuation is small. The existing solution is obviously not enough to meet this standard. In addition to being related to the gap performance, it is also affected by the limitations of the arrester body. That is, the action characteristics of the controllable arrester under the operation overvoltage are jointly determined by the arrester body and the controllable switch. From another perspective, when the fixed part ages due to energy absorption after multiple actions, one of the results of aging is the reduction of the nonlinear coefficient of the fixed part. When a new operation overvoltage comes, since the nonlinear coefficient of the controlled part is greater than that of the fixed part, the voltage division of the controlled part is lower than the theoretical value, and the time for the controlled part to reach the preset voltage is delayed, which will further extend the triggering delay of the gap and affect the voltage limiting capability of the controllable arrester. Summary of the Invention

[0007] The object of the present invention is to provide a low residual voltage arrester controlled by a self-breakdown gas switch to solve the above-mentioned problems existing in controllable arresters.

[0008] To achieve the above object, the present invention adopts the following technical solutions: A self-breakdown gas switch controlled low residual voltage arrester, comprising a zinc oxide arrester with nonlinear resistance characteristics, a linear component, and a self-breakdown gas switch connected in parallel with the linear component; One end of the zinc oxide lightning arrester is connected in series with one end of the linear component, the other end of the zinc oxide lightning arrester is connected to high voltage, the other end of the linear component is grounded, and the self-breakdown gas switch is connected in parallel at both ends of the linear component.

[0009] Furthermore, the linear component includes a linear resistor and a linear capacitor string, and the linear resistor and the linear capacitor string are connected in parallel.

[0010] Furthermore, the resistance of the resistor and the capacitive reactance of the capacitor are determined by multiplying the equivalent resistance and capacitive reactance of the zinc oxide arrester at the rated operating voltage by the same coefficient.

[0011] Furthermore, during operation, the charge rate of the zinc oxide arrester is less than or equal to 70%.

[0012] Furthermore, the ratio of the rated voltage of the linear component to the rated voltage of the arrester body is 15%; the voltage error of the linear component is less than 1%, and the phase difference is less than 40'.

[0013] Furthermore, during normal operation, the gas switch does not break down; under overvoltage, the linear component voltage drop increases, the zinc oxide arrester voltage drop decreases, and the gas switch self-breaks down and conducts after the linear component voltage drop increases to its threshold.

[0014] Furthermore, the overvoltage is limited to 1.6~1.7pu.

[0015] A lightning arrester comprises the self-breakdown gas switch controlled low residual voltage arrester.

[0016] Compared with the prior art, the present invention has the following technical effects: Unlike controllable arresters, this invention changes the voltage division method by replacing the nonlinear varistor in the controlled portion with a linear parallel resistor-capacitor circuit. This shifts from a nonlinear-to-nonlinear ratio to a nonlinear-to-linear ratio. This maintains the arrester's performance under normal operating conditions while ensuring a more flexible and reliable self-breakdown of the gas switch when overvoltage occurs, achieving deep overvoltage suppression.

[0017] The linear component of the present invention is composed of a parallel circuit of resistors and capacitors, and the control switch is a self-breakdown type gap. When the system is operating normally, the control switch is disconnected, and the nonlinear component and the linear component jointly bear the continuous operating voltage. When an overvoltage occurs, the voltage across the linear component rises rapidly, causing the gap to self-break down and conduct, causing the linear component to be short-circuited, and energy flows into the ground after passing through the nonlinear component and the gap and is discharged. The residual voltage of the lightning arrester is reduced to the residual voltage of the nonlinear component, achieving the purpose of deeply suppressing the system operation overvoltage. The present invention can not only ensure that the lightning arrester has a low charge rate under normal operating conditions, but also make the gas switch more reliably self-breakdown under the action of overvoltage, thereby obtaining a lower residual voltage and achieving deep suppression of overvoltage in the power system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the present invention.

[0019] Figure 2 It is an experimental circuit diagram in a specific embodiment.

[0020] Figure 3 The volt-ampere characteristic curve of the metal oxide varistor constituting the nonlinear component of the controllable lightning arrester in a specific embodiment.

[0021] Figure 4 4 is a waveform diagram of the total voltage and linear component voltage during normal operation of the controllable lightning arrester in a specific embodiment.

[0022] Figure 5 The figure shows the relationship between the voltage divider ratio and the switching overvoltage when the gap is not working. The voltage ratio refers to the ratio of the linear component voltage to the total voltage when the total voltage reaches its peak.

[0023] in: 1. Zinc oxide lightning arrester with nonlinear resistance characteristics; 2. Linear component; 3. Self-breakdown gas switch; 11. Metal oxide varistor; 21. Resistor and capacitor parallel connection. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to the accompanying drawings: See also Figure 1The present invention discloses a self-breakdown gas switch controlled low residual voltage arrester, the controllable arrester comprising: a zinc oxide arrester having nonlinear resistance characteristics, a linear component, and a self-breakdown gas switch connected in parallel with the linear component; One end of the zinc oxide lightning arrester is connected in series with one end of the linear component, the other end of the zinc oxide lightning arrester is connected to high voltage, the other end of the linear component is grounded, and the self-breakdown gas switch is connected in parallel at both ends of the linear component.

[0025] When the system is operating normally, the control switch is disconnected, and the nonlinear components and linear components share the responsibility of bearing the continuous operating voltage.

[0026] The linear component is mainly composed of a linear resistor and a linear capacitor string. Its resistance and capacitive reactance are determined by multiplying the equivalent resistance and capacitive reactance of the nonlinear component at the rated working voltage by the same coefficient.

[0027] When the system is operating normally, the charge rate of the nonlinear component does not exceed 70%; the ratio of the rated voltage of the linear component to the rated voltage of the arrester body is about 15%; the voltage error of the linear component does not exceed 1%, and the phase difference does not exceed 40'.

[0028] Limit overvoltage to 1.6~1.7pu.

[0029] The control switch is a self-breakdown type gap; when the system is operating normally, the gap is not conductive; under overvoltage, the linear component voltage drop increases and the nonlinear component voltage drop decreases, and the gap self-breaks down and conducts after the linear component voltage rises rapidly to its threshold.

[0030] When an overvoltage occurs, the voltage across the linear component rises rapidly, causing the gap to self-break down and conduct, short-circuiting the linear component. Energy then flows through the nonlinear component and the gap and is discharged to the ground. The residual voltage of the arrester is reduced to the residual voltage of the nonlinear component, achieving the goal of deeply suppressing the system's operating overvoltage.

[0031] like Figure 2 The verification experiment of the present invention is carried out as shown. Figure 2 The nonlinear component of the controllable lightning arrester is composed of 5 layers of varistors with the same formula and specifications. The equivalent capacitance of the varistor at the rated voltage is about 2nF. Its volt-ampere characteristic curve is as follows: Figure 3 shown.

[0032] Figure 2 The linear component of the controllable lightning arrester consists of a 2.27nF capacitor in parallel with 400MΩ.

[0033] Figure 4The total voltage waveform of the arrester body and the voltage waveform of the linear component are displayed at a charge factor of 60%. The rated controllable ratio is 15%, the actual controllable ratio is 14.9%, the voltage error of the linear component is 0.67%, and the phase difference is 22'.

[0034] Figure 5 A graph shows the relationship between the voltage divider ratio and the switching overvoltage when the gap is not operating. The voltage divider ratio of a controllable surge arrester varies very little with the applied voltage, approximately equal to the rated controllable ratio. However, in the present invention, the voltage divider ratio increases nonlinearly with the applied voltage when the applied voltage exceeds 1 p.u. (1.0 p.u. is the system's highest operating phase RMS voltage, which, converted to a peak value, is approximately equal to the controllable surge arrester reference voltage).

[0035] To achieve better protection, the operating voltage of a controllable lightning arrester is generally set at 1.2 to 1.3 pu. That is, when the operating overvoltage rises to the range of 1.2 to 1.3 pu, the gap needs to be broken down. Therefore, the operating voltage range of the gap is equal to the operating voltage of the controllable lightning arrester multiplied by the controllability ratio, which is equal to 0.18 to 0.195 pu. Assuming that the rated voltage of the gap takes the middle value of 0.1875 pu, taking into account its own dispersion (generally ±10%), the actual operating voltage range of the gap is 0.1688 pu to 0.2063 pu. Obviously, this range exceeds the theoretical value, which means that if the controllable lightning arrester adopts a self-breakdown method, the gap has a probability of malfunctioning or delayed operation. The present invention can solve this problem.

[0036] based on Figure 5 It can be obtained that at voltages of 1.2pu and 1.3pu, the voltage divider ratios are approximately 0.286 and 0.342, respectively, that is, the theoretical value of the gap's operating voltage range is 0.343~0.445pu. Similarly, considering the 10% dispersion of the operating voltage, it can be calculated that the rated operating voltage is 0.381~0.404pu, and the actual operating voltage range is included in the theoretical range. Therefore, the controllable lightning arrester can operate reliably by self-breakdown. The present invention has flexibility when designing the gap, and the aging problem of nonlinear components after long-term operation can be taken into account by moderately reducing the operating voltage of the gap.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A self-breakdown gas switch controlled low residual voltage arrester, characterized in that: The invention comprises a zinc oxide lightning arrester with nonlinear resistance characteristics, a linear component, and a self-breakdown type gas switch connected in parallel with the linear component; One end of the zinc oxide lightning arrester is connected in series with one end of the linear component, the other end of the zinc oxide lightning arrester is connected to high voltage, the other end of the linear component is grounded, and the self-breakdown gas switch is connected in parallel at both ends of the linear component.

2. The self-breakdown gas switch controlled low residual voltage arrester according to claim 1, characterized in that: The linear component includes a linear resistor and a linear capacitor string, and the linear resistor and the linear capacitor string are connected in parallel.

3. The self-breakdown gas switch controlled low residual voltage arrester according to claim 2, characterized in that: The resistance of the resistor and the capacitive reactance of the capacitor are determined by multiplying the equivalent resistance and capacitive reactance of the zinc oxide lightning arrester at the rated working voltage by the same coefficient.

4. The self-breakdown gas switch controlled low residual voltage arrester according to claim 3, characterized in that: During operation, the charge rate of the zinc oxide arrester is less than or equal to 70%.

5. The self-breakdown gas switch controlled low residual voltage arrester according to claim 4, characterized in that: The ratio of the rated voltage of the linear component to the rated voltage of the arrester body is 15%; the voltage error of the linear component is less than 1%, and the phase difference is less than 40'.

6. The self-breakdown gas switch controlled low residual voltage arrester according to claim 5, characterized in that: During normal operation, the gas switch does not break down; under overvoltage, the linear component voltage drop increases, the zinc oxide arrester voltage drop decreases, and the gas switch self-breaks down and turns on after the linear component voltage drop increases to its threshold.

7. The self-breakdown gas switch controlled low residual voltage arrester according to claim 6, characterized in that: Overvoltage is limited to 1.6~1.7pu.

8. A lightning protection device, characterized in that: It includes the self-breakdown gas switch controlled low residual voltage arrester as described in claim 7.

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