Modularized rapid controllable lightning arrester based on hybrid bypass switch and control method thereof

Abstract

The invention provides a modularized rapid controllable lightning arrester based on a hybrid bypass switch and a control method thereof, the lightning arrester is connected in parallel with a protection unit, the lightning arrester comprises a fixed part and a controllable part, and the fixed part is connected in series with the controllable part. Wherein the fixed part is provided with a first overvoltage protection element; the controllable part is provided with a controllable module or a plurality of controllable modules which are connected in series; and a second overvoltage protection element and a hybrid bypass switch are connected in parallel in the module. The hybrid bypass switch is provided with a breakthrough gap and a thyristor. According to the controllable lightning arrester, the closing time of the bypass switch is shortened through the breakthrough gap, so that the controllable lightning arrester has the capability of deeply inhibiting fast wavefront overvoltage, meanwhile, the charge rate of the lightning arrester is reduced, the problem of action consistency caused by series connection of a large number of thyristors is avoided through the modular design, the redundant number of the thyristors is reduced, and the reliability of the controllable lightning arrester is improved. The transient overvoltage level of the system can be effectively reduced, and the insulation electric clear distance of the system is reduced.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a modular fast controllable lightning arrester based on a hybrid bypass switch and a control method thereof. Background Art

[0002] With the rapid growth in the demand for transmission distance and capacity in existing power grids, in order to ensure the economy of power transmission, the transmission voltage level used is also significantly increased, resulting in a rapid increase in overvoltage levels.

[0003] In order to suppress the damage of overvoltage to the devices in the system, metal oxide arresters are widely used in power systems to suppress overvoltage.

[0004] However, the existing usage scenarios continue to put forward higher requirements for the reliability of lightning arresters, which also limits its protection performance, which is reflected in the parameters that the charge rate restricts the protection level and residual voltage; similarly, this also seriously restricts system construction and equipment manufacturing, greatly increasing the cost and difficulty of system construction, and even overvoltage will threaten the reliable operation of the system. In particular, in the current design scenario, because of the large-scale use of emerging power electronic devices, they are more sensitive than traditional power equipment to the peak of transient overvoltage. However, the slow wave front overvoltage and fast wave front overvoltage levels on the DC side of the DC grid are usually about 2p.u.. Furthermore, the slow wave front overvoltage and fast wave front overvoltage levels on the valve side of the pole line reactor also reach about 1.9pu. Therefore, as more power electronic equipment is adopted on the DC side of the DC transmission system, it is urgent to deeply suppress overvoltage.

[0005] In order to deeply suppress the slow wavefront overvoltage, the existing technology reduces the overvoltage by turning on the bypass switch when the system fails, reducing the number of lightning arresters connected to the system. This method of decoupling the charge rate and transient pressure ratio is very mature and has been put into operation in DC projects. Among them, according to the bypass switch, the controllable lightning arrester can be divided into a mechanical switch type and a thyristor type. The turn-on time of the mechanical switch and the thyristor are in the order of milliseconds and microseconds, respectively, and there is a delay problem in the system control. However, the wavefront time of the typical fast wavefront overvoltage is in the range of 0.1 to 20 microseconds, which means that the existing bypass switch cannot be turned on within the wavefront range. Therefore, the controllable lightning arrester cannot deeply suppress the fast wavefront overvoltage. However, in order to have a certain lightning overvoltage suppression capability, the charge rate of the controllable lightning arrester is the same as that of the traditional metal oxide lightning arrester, and the expected effect of further improving reliability is not achieved. In addition, in high-voltage scenarios, a large number of thyristors connected in series have voltage balancing and action consistency problems.

[0006] In summary, it is also necessary to improve the structure of the controllable lightning arrester so that its bypass switch can be turned on within the wavefront range, achieve the ability to deeply suppress fast wavefront overvoltage, simplify the existing structural design, and reduce costs. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a multi-port hybrid DC circuit breaker with a simplified structure, low cost and the same functions.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0009] On the one hand, the present invention provides a modular fast controllable lightning arrester based on a hybrid bypass switch, the lightning arrester comprising a fixed part and a controllable part; the fixed part is connected in series with the controllable part; the lightning arrester is connected in parallel with a protection unit;

[0010] The fixing portion is provided with a first overvoltage protection element;

[0011] The controllable part is provided with one controllable module or a plurality of controllable modules connected in series;

[0012] A second overvoltage protection element and a hybrid bypass switch are connected in parallel in the controllable module;

[0013] The hybrid bypass switch is provided with a breakdown gap and a thyristor.

[0014] Optionally, the first overvoltage protection element is a metal oxide varistor.

[0015] Optionally, a first voltage-equalizing resistor is further provided in the fixed portion;

[0016] The first voltage balancing resistor is connected in parallel with the first overvoltage protection element.

[0017] Optionally, the controllable module is further provided with a second voltage-equalizing resistor;

[0018] The second balancing resistor is connected in parallel with the second overvoltage protection element, the breakdown gap and the thyristor.

[0019] Optionally, a resistance ratio of the first balancing resistor to the second balancing resistor is equal to a rated voltage ratio of the first overvoltage protection element to the second overvoltage protection element.

[0020] Optionally, the second overvoltage protection element is a metal oxide varistor.

[0021] Optionally, the electrode structure capable of breaking through the gap is a parallel plate gap structure.

[0022] Optionally, the lateral dimension of the electrode capable of penetrating the gap is 5-60 times the gap distance.

[0023] Optionally, the electrode capable of breaking through the gap is in a disc-shaped structure, and the gap distance is in the millimeter order;

[0024] The diameter of the electrode capable of penetrating the gap is 15-60 times the gap distance.

[0025] On the other hand, the present invention also provides a modular fast controllable arrester control method based on a hybrid bypass switch, which comprises the following steps:

[0026] S1, real-time monitoring of the fixed part voltage, when the monitoring value exceeds the design value, the hybrid bypass switch is closed to exit the controllable part;

[0027] S2. When the voltage of the fixed part exceeds a threshold value, the thyristor in the hybrid bypass is turned on;

[0028] S3, when the voltage of the controllable part drops and the current of the thyristor is less than the holding current, the thyristor is turned off, the hybrid bypass switch is opened, and the controllable part is put into operation;

[0029] The lightning arrester exits the voltage suppression process.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The present invention shortens the closing time of the bypass switch through the breakdown gap, so that the controllable lightning arrester has the ability to deeply suppress fast wave front overvoltage while reducing the charging rate of the lightning arrester. The modular design avoids the problem of action consistency caused by a large number of thyristors connected in series, reduces the redundant number of thyristors, can effectively reduce the transient overvoltage level of the system, and reduce the insulation clearance distance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 This is a schematic circuit diagram of the circuit breaker of the present invention;

[0034] Figure 2 This is a flow chart of the control method of the present invention;

[0035] Figure 3 A device voltage waveform diagram during the control process of a specific embodiment;

[0036] Figure 4 It is a voltage waveform diagram of the fixed part during the control process of a specific embodiment;

[0037] Figure 5 It is a voltage waveform diagram of the controllable part during the control process of a specific embodiment.

[0038] In the figure: 1. fixed part; 2. controllable part; 3. controllable module; 4. first balancing resistor; 5. second balancing resistor; 6. first overvoltage protection element; 7. second overvoltage protection element; 8. breakdown gap; 9. thyristor. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0040] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0041] In the description of the present invention, “plurality” means two or more than two, unless otherwise clearly and specifically defined.

[0042] It is worth noting that the methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products, and their sources are not specifically limited unless otherwise specified.

[0043] like Figure 1 As shown, this embodiment provides a modular fast controllable lightning arrester based on a hybrid bypass switch, the lightning arrester mainly includes a fixed part 1 and a controllable part 2, and the fixed part 1 and the controllable part 2 are arranged in series, and the lightning arrester is connected in parallel with the protection unit to control overvoltage.

[0044] The fixed part is provided with a first overvoltage protection element 6, and the first overvoltage protection element 6 of this embodiment is selected as a metal oxide varistor. Optionally, in order to maintain balanced voltage distribution, a first voltage balancing resistor 4 is also provided in the fixed part 1, and the first voltage balancing resistor 4 is connected in parallel with the first overvoltage protection element 6.

[0045] The controllable part 2 is provided with a plurality of controllable modules 3 connected in series. A second overvoltage protection element 7 and a hybrid bypass switch are connected in parallel in the controllable module 3. The second overvoltage protection element 7 of this embodiment is also a metal oxide varistor. The hybrid bypass switch is the main improved design unit, which is provided with a breakdown gap 8 and a thyristor 9, and the breakdown gap 8, the thyristor 9 and the corresponding second overvoltage protection element 7 are arranged in parallel. The application of the breakdown gap 8 makes the action reaction time of the hybrid bypass switch reach the order of ten nanoseconds; and the use of the thyristor 9 in parallel with the breakdown gap 8 plays a role in extinguishing the arc and improving the current carrying capacity of the bypass switch, avoiding the problem of short gap life and the problem of being unable to extinguish the arc after the gap is overheated, thereby improving the reliability of the hybrid bypass switch. Optionally, in order to further improve the response speed of the hybrid bypass switch, the electrode structure of the breakdown gap 8 is designed in this embodiment as a parallel plate gap structure, and the electrode size is much larger than the gap distance. Preferably, the lateral size of the electrode of the breakdown gap 8 is 5-60 times the gap distance. Furthermore, in the parallel plate gap structure capable of breaking through the gap 8, the electrode is specifically disc-shaped, the gap distance is in the millimeter level (0.5 mm-9 mm), and the ratio of the electrode diameter corresponding to the lateral dimension to the gap distance thereof is further limited to 15-60 times.

[0046] Optionally, each controllable module 3 is also provided with a second equalizing resistor 5, which is connected in parallel with the second overvoltage protection element 7, the breakdown gap 8 and the thyristor 9. The application of the second equalizing resistor 5 combined with the modular design makes the discharge voltage more evenly dispersed. Therefore, the aforementioned small gap (compared to the lateral size of the electrode) breakdown gap design is adapted to the high-voltage application scenario of the present invention, with a shorter response time and a better service life, and because the gap discharge voltage is normally distributed, this design can achieve excellent speed while having better stability, effectively solving the problem of gap refusal and misoperation; the module independently configures the equalizing resistor to avoid the voltage balancing problem caused by a large number of thyristors in series, and the modular design also solves the problem of thyristor action consistency and reduces the number of redundant thyristors. Further, in the selection of the resistance value of the equalizing resistor, the resistance value of the first equalizing resistor 4 is greater than or equal to 1MΩ, which avoids the bypass switch current being too large after the overvoltage, and the current being greater than the thyristor holding current, causing the thyristor to be unable to turn off. Furthermore, the two equalizing resistors are designed to be related to each other to achieve the function of voltage balance. The resistance ratio of the first equalizing resistor 4 to the second equalizing resistor 5 is equal to the rated voltage ratio of the first overvoltage protection element 6 to the second overvoltage protection element 7.

[0047] Based on the above design, the hybrid bypass switch of the controllable lightning arrester of this embodiment can reduce or avoid the problems of refusal to operate, malfunction or plate ablation, and can also improve the problem of voltage imbalance and inconsistent operation caused by a large number of power electronic devices in series.

[0048] Based on the above-mentioned modular fast controllable lightning arrester based on hybrid bypass switch, this embodiment also provides a Figure 2 The control method shown, in particular, combines Figure 3-Figure 5 As shown in the voltage waveform, the normal operation of the system is recorded as the T1 period. During this period, the voltage of the fixed part 1 is monitored in real time, and the monitored value does not exceed the set value. Therefore, the lightning arrester does not work, the hybrid bypass switch is open, and is in a low charge rate state.

[0049] When overvoltage occurs in the system, the control method includes the following steps:

[0050] S1. During the T2 period, when the voltage of the monitored fixed part exceeds the design value, the breakdown gaps in the hybrid bypass are broken down successively, causing the hybrid bypass switch to close, resulting in the exit of the controllable part.

[0051] S2. The voltage of the fixed part continues to rise. When the voltage of the fixed part exceeds the threshold, the system sends a command to trigger the thyristor in the hybrid bypass to make it turn on; when the overvoltage wavefront time is long, the thyristor is turned on in the corresponding stage of the T3 period, which can break down the arc in the gap and extinguish the overvoltage, and continue to deeply suppress the overvoltage; when the overvoltage wavefront time is short, the thyristor is turned on in the corresponding stage of the T4 period, which can break down the arc in the gap and extinguish the overvoltage, and continue to deeply suppress the overvoltage.

[0052] S3, in the T5 period, after the overvoltage peak is suppressed, the voltage of the controllable part drops, and the current of the thyristor is less than the holding current, the thyristor is turned off, the hybrid bypass switch is opened, and the controllable part is put into operation;

[0053] As a result, the arrester exits the initial voltage suppression process.

[0054] It should be understood that the "time period" mentioned in the above embodiment is only used to describe that the specific action timing of the step is arranged in chronological order, and the specific time period is determined according to the actual working conditions and the corresponding detection signal. It is not a simple static value. It can be a fixed value after verification, or it can be a follow-up value generated by the detection signal. It cannot be understood as a limiting condition of the present invention.

[0055] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A modular fast controllable lightning arrester based on a hybrid bypass switch, characterized in that: The arrester comprises a fixed part and a controllable part; the fixed part and the controllable part are connected in series; the arrester and the protection unit are connected in parallel; The fixing portion is provided with a first overvoltage protection element; The controllable part is provided with one controllable module or a plurality of controllable modules connected in series; A second overvoltage protection element and a hybrid bypass switch are connected in parallel in the controllable module; The hybrid bypass switch is provided with a breakdown gap and a thyristor.

2. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 1 is characterized in that: The first overvoltage protection element is a metal oxide varistor.

3. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 1 or 2, characterized in that: The fixing part is also provided with a first voltage-equalizing resistor; The first voltage balancing resistor is connected in parallel with the first overvoltage protection element.

4. The modular fast controllable arrester based on hybrid bypass switch according to claim 3 is characterized in that: The controllable module is also provided with a second voltage-equalizing resistor; The second balancing resistor is connected in parallel with the second overvoltage protection element, the breakdown gap and the thyristor.

5. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 4 is characterized in that: The resistance ratio of the first balancing resistor to the second balancing resistor is equal to the rated voltage ratio of the first overvoltage protection element to the second overvoltage protection element.

6. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 5 is characterized in that: The second overvoltage protection element is a metal oxide varistor.

7. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 6 is characterized in that: The electrode structure capable of breaking through the gap is a parallel plate gap structure.

8. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 7 is characterized in that: The lateral dimension of the electrode capable of penetrating the gap is 5-60 times the gap distance.

9. The modular fast controllable lightning arrester based on hybrid bypass switch according to claim 8, characterized in that: The electrode capable of breaking through the gap is in a disc-shaped structure, and the gap distance is in the millimeter order; The diameter of the electrode capable of penetrating the gap is 15-60 times the gap distance.

10. A modular fast controllable lightning arrester control method based on a hybrid bypass switch, characterized in that: The steps include: S1, real-time monitoring of the fixed part voltage, when the monitoring value exceeds the design value, the hybrid bypass switch is closed to exit the controllable part; S2. When the voltage of the fixed part exceeds a threshold value, the thyristor in the hybrid bypass is turned on; S3, when the voltage of the controllable part drops and the current of the thyristor is less than the holding current, the thyristor is turned off, the hybrid bypass switch is opened, and the controllable part is put into operation; The lightning arrester exits the voltage suppression process.

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