A circuit breaker operating overvoltage elimination system and method of operation

Abstract

The application discloses a circuit breaker operation overvoltage elimination system and an operation method, relates to the technical field of overvoltage elimination, and comprises an auxiliary vacuum circuit breaker, a light trigger thyristor valve body, a tripping detection and trigger signal generation unit, a splitter and a circuit breaker operation loop; wherein the upper terminal and the lower terminal of the auxiliary vacuum circuit breaker are connected with the upper terminal of a main loop vacuum circuit breaker and the upper terminal of the light trigger thyristor valve body respectively, and the lower terminal of the light trigger thyristor valve body is connected with the lower terminal of the main loop vacuum circuit breaker; the input end of the tripping detection and trigger signal generation unit is connected with the closing coil of the auxiliary vacuum circuit breaker in parallel, the output end of the tripping detection and trigger signal generation unit outputs a trigger light signal, the trigger light signal is connected with the input end of the splitter through an output optical fiber, and the output end of the splitter is connected with the gate input end of the light trigger thyristor. The application relieves the technical problems of great implementation difficulty and complex control in the prior art.

Description

Technical Field

[0001] This invention relates to the field of overvoltage elimination technology, specifically to an overvoltage elimination system and operating method for circuit breaker operation. Background Technology

[0002] The ladle refining furnace (LF) is used to treat molten steel, performing processes such as heating, fine-tuning of alloy composition, desulfurization, deoxidation, slag formation, inclusion control, and temperature homogenization to improve steel quality. It is a crucial production link between steelmaking and continuous casting, coordinating the production rhythms of converters and continuous casting machines, and is increasingly widely used by steel companies. The LF furnace has a short smelting cycle and requires frequent power outages for temperature measurement and sampling. Therefore, the high-voltage vacuum circuit breaker in the LF furnace system operates very frequently, exceeding 30,000 times per year. This not only causes operational overvoltage and current arcing, significantly increasing equipment failure rates, but also negatively impacts production organization and employee safety. Experience has shown that without effective overvoltage suppression technology, the operation of the LF furnace transformer poses significant safety hazards.

[0003] Instantaneous overvoltage during the opening and closing of switching circuits is unavoidable, and such overvoltages pose a significant threat to electrical equipment, even causing it to burn out. Due to the inherent characteristics of vacuum circuit breakers, the probability of overvoltage during operation is higher than with other circuit breakers, and the phenomenon of overvoltage is more pronounced. It has been learned that overvoltages in LF furnace vacuum circuit breakers are primarily current-cutting overvoltages. In the past, the arc-extinguishing capability of oil-filled circuit breakers and some air-filled circuit breakers used in LF furnace power supply systems was directly related to the cut current. The smaller the cut current, the less gas generated by the arc in the circuit breaker, and the weaker the arc-extinguishing capability. Therefore, when disconnecting an unloaded transformer, there was generally no obvious instantaneous current-cutting phenomenon, and the operational overvoltage value was not large. Currently, vacuum circuit breakers are mostly used in LF furnaces of 35kV and below. Vacuum circuit breakers are circuit breakers that close and open in a high vacuum, resulting in particularly strong breaking capacity. When interrupting low-power, low-current LF furnaces, the current may be cut off before the natural zero point due to the current-cutting phenomenon of the vacuum arc. When the rate of change of current is very high, overvoltage will be generated. Essentially, this is caused by the rapid change of the magnetic field in the inductor, which leads to a very high induced voltage.

[0004] To address switching overvoltages in vacuum circuit breakers, especially current-cutting overvoltages, many companies are currently focusing on developing low-current-cutting-level contact materials to reduce tripping current and overvoltage values. Additionally, installing an RC-type resistor-capacitor absorption device between the load and ground can also suppress switching overvoltages. While these measures have some effect, they cannot fundamentally eliminate switching overvoltages.

[0005] A domestic patent, "An Overvoltage Suppression Method for Circuit Breaker Opening Operation (Patent Application No. CN202411532619.7)," discloses the following: During the opening operation, the transient voltage changes of each key node in the system are monitored; a distributed multi-point suppression method is selected based on the node voltage status; the opening angle of the circuit breaker is adjusted based on the real-time detected voltage and current status; in the event of transient overvoltage, the line impedance is instantaneously adjusted to delay the voltage rise; a small capacitor is added to the opening circuit for instantaneous voltage absorption; and based on the fault characteristics analysis of the line, an early warning of impending overvoltage is issued, triggering an adaptive adjustment operation. However, the "instantaneous adjustment of line impedance" in this method is difficult to implement, and the response speed is hard to meet the requirements. A domestic patent, "An Operational Overvoltage Suppression Device (Application Patent No. CN201410559422.2)," discloses a device comprising a main switch circuit, a closing damping circuit, and a voltage equalization circuit. The main switch circuit, closing damping circuit, and voltage equalization circuit are connected in parallel. The device also includes a parallel protection circuit for overvoltage protection, a sampling unit, and a transmission unit for sampling and data transmission. The operational overvoltage suppression device employs a multi-closing switch structure to reliably prevent the heating effect of a single closing switch. It also uses a parallel protection device to prevent overvoltage damage and a monitoring device to monitor the suppression device and confirm its operating status, demonstrating long-term reliability and stability. However, this patent still requires the use of a tripping resistor, an RC circuit, and synchronous closing to reduce operational overvoltage, placing high demands on the speed and anti-interference capabilities of the transmission channel, and making control complex. Summary of the Invention

[0006] The purpose of this invention is to provide a circuit breaker operation overvoltage elimination system and operation method to solve at least one of the above-mentioned technical problems.

[0007] In a first aspect, embodiments of the present invention provide a circuit breaker operation overvoltage elimination system applied to a power supply system; the power supply system includes a working power supply and a main circuit vacuum circuit breaker; the upper and lower terminals of the main circuit vacuum circuit breaker are respectively connected to the positive terminal of the working power supply and the load; the circuit breaker operation overvoltage elimination system includes: an auxiliary vacuum circuit breaker, an optically triggered thyristor valve body, a trip detection and trigger signal generation unit, a beam splitter, and a circuit breaker operation circuit; wherein, the upper and lower terminals of the auxiliary vacuum circuit breaker are respectively connected to the upper terminal of the main circuit vacuum circuit breaker and the upper terminal of the optically triggered thyristor valve body, and the lower terminal of the optically triggered thyristor valve body is connected to the lower terminal of the main circuit vacuum circuit breaker; the optically triggered thyristor valve body includes multiple valve body assemblies connected in series, each valve body assembly including two optically triggered thyristors connected in reverse parallel; the circuit breaker operation circuit... The circuit includes a main circuit breaker tripping circuit and an auxiliary circuit breaker closing circuit. The main circuit breaker tripping circuit includes a main circuit tripping node, a normally open node of the main circuit vacuum circuit breaker, a normally open node of the auxiliary vacuum circuit breaker, and a tripping coil of the main circuit vacuum circuit breaker connected in series. The auxiliary circuit breaker closing circuit includes a normally closed node of the auxiliary vacuum circuit breaker and a closing coil of the auxiliary vacuum circuit breaker connected in parallel across the normally open node of the auxiliary vacuum circuit breaker and the tripping coil of the main circuit vacuum circuit breaker. The input terminal of the tripping detection and trigger signal generation unit is connected in parallel with the closing coil of the auxiliary vacuum circuit breaker. The output terminal of the tripping detection and trigger signal generation unit outputs a trigger optical signal. The trigger optical signal is connected to the input terminal of the optical splitter through an output optical fiber. The output terminal of the optical splitter is connected to the gate input terminal of the optical trigger thyristor.

[0008] Optionally, the main circuit vacuum circuit breaker and the auxiliary vacuum circuit breaker respectively include an A-phase switch, a B-phase switch, and a C-phase switch; the optically triggered thyristor valve body includes an A-phase optically triggered thyristor valve body, a B-phase optically triggered thyristor valve body, and a C-phase optically triggered thyristor valve body; wherein, the A-phase optically triggered thyristor valve body, the B-phase optically triggered thyristor valve body, and the C-phase optically triggered thyristor valve body each include an even number of valve body assemblies connected in series; the upper terminal of the A-phase optically triggered thyristor valve body is connected to the lower terminal of the A-phase switch of the auxiliary vacuum circuit breaker, and the A-phase optically triggered thyristor valve body... The lower terminal of the thyristor valve body is connected to the lower terminal of the A-phase switch of the main circuit vacuum circuit breaker; the upper terminal of the B-phase optically triggered thyristor valve body is connected to the lower terminal of the B-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal of the B-phase optically triggered thyristor valve body is connected to the lower terminal of the B-phase switch of the main circuit vacuum circuit breaker; the upper terminal of the C-phase optically triggered thyristor valve body is connected to the lower terminal of the C-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal of the C-phase optically triggered thyristor valve body is connected to the lower terminal of the C-phase switch of the main circuit vacuum circuit breaker.

[0009] Optionally, the valve body assembly further includes a static voltage equalizing resistor, a dynamic voltage equalizing resistor, and a dynamic voltage equalizing capacitor; the static voltage equalizing resistor is connected in parallel with the two optically triggered thyristors, and the dynamic voltage equalizing resistor and the dynamic voltage equalizing capacitor are connected in series and then connected in parallel with the two optically triggered thyristors.

[0010] Optionally, the beam splitter includes an A-phase beam splitter, a B-phase beam splitter, and a C-phase beam splitter; wherein the A-phase beam splitter, the B-phase beam splitter, and the C-phase beam splitter each have multiple optical output ports, which are respectively connected to the gate input terminals of multiple valve body components of the A-phase optical trigger thyristor valve body, the B-phase optical trigger thyristor valve body, and the C-phase optical trigger thyristor valve body.

[0011] Optionally, the trip detection and trigger signal generation unit includes a rising edge detection unit and an electro-optical conversion unit; wherein, the rising edge detection unit is used to output a high-level electrical signal of a preset time length after detecting that the closing coil of the auxiliary vacuum circuit breaker is energized; the electro-optical conversion unit is used to convert the high-level electrical signal into a trigger optical signal.

[0012] Optionally, the circuit breaker operating circuit further includes an auxiliary circuit breaker tripping circuit and a main circuit breaker closing circuit; wherein, the auxiliary circuit breaker tripping circuit includes a valve normal signal node, a normally open node of the auxiliary vacuum circuit breaker, and a trip coil of the auxiliary vacuum circuit breaker connected in series; the main circuit breaker closing circuit includes a main circuit closing node, a normally closed node of the main circuit vacuum circuit breaker, and a closing coil of the main circuit vacuum circuit breaker connected in series.

[0013] Optionally, the system further includes a valve status monitoring voltage transformer and a valve status detection unit; wherein, the high-voltage terminal of the valve status monitoring voltage transformer is connected in parallel with the optically triggered thyristor valve body, the low-voltage terminal of the valve status monitoring voltage transformer is connected to the input terminal of the valve status detection unit, and the output terminal of the valve status detection unit is connected to the valve normal signal node.

[0014] Optionally, the valve status monitoring voltage transformer includes an A-phase valve status monitoring voltage transformer, a B-phase valve status monitoring voltage transformer, and a C-phase valve status monitoring voltage transformer. Each of the A-phase, B-phase, and C-phase valve status monitoring voltage transformers is composed of two single-phase electromagnetic voltage transformers connected in series. The common terminal of the two single-phase electromagnetic voltage transformers is connected to the intermediate node of multiple series-connected valve body components of the optically triggered thyristor valve body.

[0015] Secondly, embodiments of the present invention also provide an operation method for a circuit breaker operation overvoltage elimination system, comprising: controlling the main circuit tripping node to close, energizing the closing coil of the auxiliary vacuum circuit breaker, and closing the auxiliary vacuum circuit breaker; the tripping detection and trigger signal generation unit generating a high-level electrical signal of a preset time length and converting the high-level electrical signal into a trigger optical signal; transmitting the trigger optical signal to the gate input terminal of the optical trigger thyristor valve body through the optical splitter, so that the optical trigger thyristor valve body enters a trigger waiting state; and closing the normally open node of the auxiliary vacuum circuit breaker. When the main circuit vacuum circuit breaker is closed, its closing coil is energized, and the main circuit vacuum circuit breaker is opened. The optically triggered thyristor valve body is turned on to eliminate overvoltage. After a preset time period, the current of the optically triggered thyristor valve body is turned off at zero. The valve terminal voltage of the optically triggered thyristor valve body is obtained based on the valve status monitoring voltage transformer, and the valve group status is detected based on the valve status detection unit. If the valve group status detection result is normal, the valve normal signal node is closed, the trip coil of the auxiliary vacuum circuit breaker is energized, and the auxiliary vacuum circuit breaker is opened.

[0016] Optionally, the valve group status detection of the optically triggered thyristor valve body based on the valve status detection unit includes: determining whether multiple voltage criteria conditions are simultaneously met; if yes, then determining that the valve group status detection result is normal; if no, then determining that the valve group status detection result is abnormal; wherein, the multiple voltage criteria conditions include:

[0017]

[0018] In the formula, , , These represent the induced voltage values ​​corresponding to the voltage division of the upper half of the valve string in the A-phase, B-phase, and C-phase optically triggered thyristor valve bodies, respectively. , , These are the induced voltage values ​​corresponding to the voltage division of the lower half of the valve string in the A-phase, B-phase, and C-phase optically triggered thyristor valve bodies, respectively. N K1 and K2 are the rated voltage of the power supply system, K1 and K2 are preset criterion coefficients, and pu is the per-unit value of the power system.

[0019] This invention provides a circuit breaker operation overvoltage elimination system and operation method, which can not only eliminate overvoltage during opening operation, but also prevent circuit breaker arcing and increase equipment service life. This invention does not change the wiring method of existing power distribution equipment and loads. The optically triggered thyristor valve body is connected in parallel to the first and second ends of the main circuit vacuum circuit breaker, making implementation easy. By using a beam splitter and optically triggered thyristor valve body in combination, electrical insulation between high and low potentials is achieved, alleviating the technical problems of high implementation difficulty and complex control in the prior art. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A circuit diagram of a circuit breaker operation overvoltage elimination system provided in an embodiment of the present invention;

[0022] Figure 2 A flowchart illustrating an operation method for a circuit breaker operation overvoltage elimination system provided in an embodiment of the present invention;

[0023] Figure 3 A flowchart illustrating another operation method for a circuit breaker operation overvoltage elimination system provided in an embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of an overvoltage simulation model of an overvoltage elimination system without a circuit breaker provided in an embodiment of the present invention.

[0025] Figure 5 A schematic diagram of voltage and current waveforms of an overvoltage simulation model of an operating overvoltage elimination system without a circuit breaker provided in an embodiment of the present invention;

[0026] Figure 6 This is a schematic diagram of an overvoltage simulation model of an overvoltage elimination system equipped with a circuit breaker, provided in an embodiment of the present invention.

[0027] Figure 7 A schematic diagram of a high-level signal for an overvoltage simulation model of an overvoltage elimination system for circuit breaker operation provided in an embodiment of the present invention;

[0028] Figure 8 A three-phase current waveform diagram of a thyristor valve body triggered by light is provided in an embodiment of the present invention;

[0029] Figure 9This is a schematic diagram of voltage and current waveforms of an overvoltage simulation model of an overvoltage elimination system for circuit breaker operation, provided as an embodiment of the present invention. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] Figure 1 This is a circuit diagram of a circuit breaker operation overvoltage elimination system according to an embodiment of the present invention. The system is applied to a power supply system; wherein the power supply system includes a working power supply and a main circuit vacuum circuit breaker; the upper and lower terminals of the main circuit vacuum circuit breaker are respectively connected to the positive terminal of the working power supply and the load. For example, as... Figure 1 As shown, the load includes the LF furnace transformer and the LF refining furnace. Specifically, the operating power supply includes phases A, B, and C, and the main circuit vacuum circuit breaker includes the phase A switch (…). Figure 1 DLA in the middle), B-phase switch ( Figure 1 DLB and C-phase switch (in the middle) Figure 1 In the DLC), the upper terminal of DLA is A1+ and the lower terminal is A1-, the upper terminal of DLB ​​is B1+ and the lower terminal is B1-, and the upper terminal of DLC is C1+ and the lower terminal is C1-.

[0033] Specifically, the circuit breaker operation overvoltage elimination system provided in this embodiment of the invention includes: an auxiliary vacuum circuit breaker, a light-triggered thyristor valve body, a trip detection and trigger signal generation unit, a beam splitter, and a circuit breaker operation circuit; wherein...

[0034] The upper and lower terminals of the auxiliary vacuum circuit breaker are connected to the upper terminal of the main circuit vacuum circuit breaker and the upper terminal of the optically triggered thyristor valve body, respectively, and the lower terminal of the optically triggered thyristor valve body is connected to the lower terminal of the main circuit vacuum circuit breaker.

[0035] The optically triggered thyristor valve body includes multiple valve body assemblies connected in series, and each valve body assembly includes two optically triggered thyristors connected in parallel with opposite directions;

[0036] The circuit breaker operating circuit includes the main circuit breaker tripping circuit and the auxiliary circuit breaker closing circuit; the main circuit breaker tripping circuit includes the main circuit tripping node and the normally open node of the main circuit vacuum circuit breaker connected in series (i.e., Figure 1 The normally open (DL) and normally open (i.e., the auxiliary vacuum circuit breaker) are mentioned. Figure 1 The auxiliary circuit breaker closing circuit includes the normally open (FZ normally open) terminal of the auxiliary vacuum circuit breaker and the trip coil TQ1 of the main circuit vacuum circuit breaker; the auxiliary circuit breaker closing circuit includes the normally closed terminal of the auxiliary vacuum circuit breaker connected in parallel to the normally open terminal (FZ normally open) and the trip coil TQ1 of the main circuit vacuum circuit breaker. Figure 1 The normally closed (FZ) circuit breaker and the closing coil HQ2 of the auxiliary vacuum circuit breaker;

[0037] The input terminal of the trip detection and trigger signal generation unit is connected in parallel with the closing coil of the auxiliary vacuum circuit breaker. The output terminal of the trip detection and trigger signal generation unit outputs a trigger optical signal. The trigger optical signal is connected to the input terminal of the optical splitter through the output optical fiber. The output terminal of the optical splitter is connected to the gate input terminal of the optical trigger thyristor.

[0038] Specifically, such as Figure 1 As shown, the auxiliary vacuum circuit breaker includes a phase A switch ( Figure 1 FZA), B-phase switch ( Figure 1 FZB) and C-phase switch ( Figure 1 The FZA (FZA) has an upper terminal of A2+ and a lower terminal of A2-, the FZB has an upper terminal of B2+ and a lower terminal of B2-, and the FZC has an upper terminal of C2+ and a lower terminal of C2-. The optically triggered thyristor valve body includes an A-phase optically triggered thyristor valve body, a B-phase optically triggered thyristor valve body, and a C-phase optically triggered thyristor valve body; each of these three phases includes an even number of valve body assemblies connected in series.

[0039] Specifically, such as Figure 1 As shown, the upper terminal A2+ of the auxiliary vacuum circuit breaker is connected to the upper terminal A1+ of the main circuit vacuum circuit breaker; the lower terminal A2- of the auxiliary vacuum circuit breaker is connected to the upper terminal A3+ of the optically triggered thyristor valve body; the upper terminal B2+ of the auxiliary vacuum circuit breaker is connected to the upper terminal B1+ of the main circuit vacuum circuit breaker; the lower terminal B2- of the auxiliary vacuum circuit breaker is connected to the upper terminal B3+ of the optically triggered thyristor valve body; the upper terminal C2+ of the auxiliary vacuum circuit breaker is connected to the upper terminal C1+ of the main circuit vacuum circuit breaker; and the upper terminal C2- of the auxiliary vacuum circuit breaker is connected to the upper terminal C3+ of the optically triggered thyristor valve body.

[0040] In this embodiment of the invention, the valve body assembly further includes a static voltage equalizing resistor, a dynamic voltage equalizing resistor, and a dynamic voltage equalizing capacitor; the static voltage equalizing resistor is connected in parallel with two optically triggered thyristors, and the dynamic voltage equalizing resistor and the dynamic voltage equalizing capacitor are connected in series and then connected in parallel with the two optically triggered thyristors.

[0041] Specifically, such as Figure 1As shown, the A-phase optically triggered thyristor valve body consists of n valve body components (n=1,2.....n, where n is an even number), and each valve body component contains a static voltage equalization resistor R. dcAn A dynamic voltage equalization resistor R sAn A dynamic voltage equalization capacitor C sAn Two thyristors T An+ and T An- The B-phase optically triggered thyristor valve body consists of n valve body components (n=1,2.....n, where n is an even number), and each valve body component contains a static voltage equalizing resistor R. dcBn A dynamic voltage equalization resistor R sBn A dynamic voltage equalization capacitor C sBn Two thyristors T Bn+ and T Bn- The C-phase optically triggered thyristor valve body consists of n valve body components (n=1,2...n, where n is an even number), and each valve body component contains a static voltage equalization resistor R. dcCn A dynamic voltage equalization resistor R sCn A dynamic voltage equalization capacitor C sCn Two thyristors T Cn+ and T Cn- .

[0042] In this embodiment of the invention, the thyristor is in optical triggering mode, and it can conduct when a positive voltage is applied between the gate input optical signal and AK. The two thyristors are connected in reverse parallel configuration, i.e., T A / B / Cn+ Anode A is connected to T A / B / Cn- Cathode K, T A / B / Cn+ The cathode K is connected to T A / B / Cn- Anode A, static equalizing resistor R dcA / B / Cn Connected in parallel with anti-parallel thyristors, dynamic voltage equalization resistor R sA / B / Cn and dynamic voltage equalization capacitor C sA / B / Cn After being connected in series, it is connected in parallel with the anti-parallel thyristor.

[0043] Specifically, such as Figure 1As shown in the figure, the valve body components A1, A2, ... An are connected in series end to end to form the valve body of the A-phase optically triggered thyristor. The external wiring terminal of the A1 layer is defined as A3+, the external wiring terminal of the An layer is defined as A3-, and the external lead-out terminal of the middle node of the A-phase optically triggered thyristor valve body (there are n / 2 layers of valve body components above and below this node) is defined as A3 mid. The valve body components B1, B2, ... Bn are connected in series end to end to form the valve body of the B-phase optically triggered thyristor. The external wiring terminal of the B1 layer is defined as B3+, the external wiring terminal of the Bn layer is defined as B3-, and the external lead-out terminal of the middle node of the B-phase optically triggered thyristor valve body (there are n / 2 layers of valve body components above and below this node) is defined as B3 mid. The valve body components C1, C2, ... Cn are connected in series end to end to form the valve body of the C-phase optically triggered thyristor. The external wiring terminal of the C1 layer is defined as C3+, the external wiring terminal of the Cn layer is defined as C3-, and the external lead-out terminal of the middle node of the C-phase optically triggered thyristor valve body (there are n / 2 layers of valve body components above and below this node) is defined as C3 mid.

[0044] Specifically, the upper terminal A3+ of the A-phase optically triggered thyristor valve body is connected to the lower terminal A2- of the A-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal A3- of the A-phase optically triggered thyristor valve body is connected to the lower terminal A1- of the A-phase switch of the main circuit vacuum circuit breaker;

[0045] The upper terminal B, of the B-phase optically triggered thyristor valve body is connected to the lower terminal B2- of the B-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal B3- of the B-phase optically triggered thyristor valve body is connected to the lower terminal B1- of the B-phase switch of the main circuit vacuum circuit breaker;

[0046] The upper terminal C3+ of the C-phase optically triggered thyristor valve body is connected to the lower terminal C2- of the C-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal C3- of the C-phase optically triggered thyristor valve body is connected to the lower terminal C1- of the C-phase switch of the main circuit vacuum circuit breaker.

[0047] Specifically, as Figure 1 shown, the optical splitter includes an A-phase optical splitter, a B-phase optical splitter, and a C-phase optical splitter; among them,

[0048] The A-phase optical splitter, B-phase optical splitter, and C-phase optical splitter all have multiple optical output ports, which are respectively connected to the gate input terminals of multiple valve body components of the A-phase optically triggered thyristor valve body, B-phase optically triggered thyristor valve body, and C-phase optically triggered thyristor valve body.

[0049] Specifically, the output optical fibers include an A-phase main optical fiber, a B-phase main optical fiber, and a C-phase main optical fiber.

[0050] Specifically, as Figure 1As shown, the A-phase splitter, B-phase splitter, and C-phase splitter each have one optical input port and 2n optical output ports. The A-phase splitter is connected to the A-phase main optical fiber and outputs LA1- to the A-phase optical trigger thyristor valve body TA1-, LA1+ to the A-phase optical trigger thyristor valve body TA1+, LA2- to the A-phase optical trigger thyristor valve body TA2-, LA2+ to the A-phase optical trigger thyristor valve body TA2+, ..., LAn- to the A-phase optical trigger thyristor valve body TAn-, and LAn+ to the A-phase optical trigger thyristor valve body TAn+. The B-phase splitter connects to the B-phase main fiber and outputs LB1- to B-phase optical trigger thyristor valve body TB1-, LB1+ to B-phase optical trigger thyristor valve body TB1+, LB2- to B-phase optical trigger thyristor valve body TB2-, LB2+ to B-phase optical trigger thyristor valve body TB2+, ..., LBn- to B-phase optical trigger thyristor valve body TBn-, LBn+ to B-phase optical trigger thyristor valve body TBn+. The C-phase splitter connects to the C-phase main fiber and outputs LC1- to C-phase optical trigger thyristor valve body TC1-, LC1+ to C-phase optical trigger thyristor valve body TC1+, LC2- to C-phase optical trigger thyristor valve body TC2-, LC2+ to C-phase optical trigger thyristor valve body TC2+, ..., LCn- to C-phase optical trigger thyristor valve body TCn-, LCn+ to C-phase optical trigger thyristor valve body TCn+.

[0051] Specifically, the trip detection and trigger signal generation unit includes a rising edge detection unit and an electro-optical conversion unit; wherein,

[0052] The rising edge detection unit is used to output a high-level electrical signal of a preset time length after detecting that the closing coil of the auxiliary vacuum circuit breaker is energized;

[0053] The electro-optic conversion unit is used to convert a high-level electrical signal into a trigger optical signal.

[0054] Preferably, the preset time length is greater than the time length from when the main circuit vacuum circuit breaker and the auxiliary vacuum circuit breaker receive the tripping signal to when the tripping action generates an operational overvoltage.

[0055] Specifically, such as Figure 1 As shown, the electro-optical conversion unit includes an A-phase electro-optical conversion unit, a B-phase electro-optical conversion unit, and a C-phase electro-optical conversion unit. After the rising edge detection unit detects that the closing coil HQ2 of the auxiliary vacuum circuit breaker is energized, it immediately outputs a high-level electrical signal of a preset duration (the duration t is adjustable) and simultaneously inputs it to the A-phase, B-phase, and C-phase electro-optical conversion units. These three units convert the preset duration high-level electrical signal into a trigger optical signal, which is simultaneously transmitted to the A-phase splitter, B-phase splitter, and C-phase splitter, respectively, through the A-phase main optical fiber, B-phase main optical fiber, and C-phase main optical fiber.

[0056] Specifically, such as Figure 1 As shown, the circuit breaker operating circuit also includes an auxiliary circuit breaker tripping circuit and a main circuit breaker closing circuit; among which,

[0057] The auxiliary circuit breaker tripping circuit includes the valve normal signal node, the normally open node (FZ normally open) of the auxiliary vacuum circuit breaker, and the tripping coil TQ2 of the auxiliary vacuum circuit breaker connected in series.

[0058] The main circuit breaker closing circuit includes the main circuit closing node and the normally closed node of the main circuit vacuum circuit breaker connected in series (i.e., Figure 1 The closing coil HQ1 of the DL normally closed circuit breaker and the main circuit vacuum circuit breaker.

[0059] Preferably, the main circuit breaker tripping circuit, the auxiliary circuit breaker tripping circuit, and the main circuit breaker closing circuit in the circuit breaker operating circuit are connected in parallel between the control bus +KM and the control bus -KM, respectively. The two ends of the auxiliary circuit breaker closing circuit are connected between the connection point between the normally open node of the main circuit vacuum circuit breaker and the normally open node of the auxiliary vacuum circuit breaker and the control bus -KM, respectively.

[0060] Specifically, after the trip coil TQ1 of the main circuit vacuum circuit breaker is energized, the main circuit vacuum circuit breaker trips.

[0061] After the closing coil HQ1 of the main circuit vacuum circuit breaker is energized, the main circuit vacuum circuit breaker closes.

[0062] The normally open node of the main circuit vacuum circuit breaker is the status node of the main circuit vacuum circuit breaker. When the main circuit vacuum circuit breaker is open, the normally open node is disconnected; when the main circuit vacuum circuit breaker is closed, the normally open node is closed.

[0063] The normally closed node of the main circuit vacuum circuit breaker is the status node of the main circuit vacuum circuit breaker. When the main circuit vacuum circuit breaker is open, the normally closed node is closed; when the main circuit vacuum circuit breaker is closed, the normally closed node is open.

[0064] When the trip coil TQ2 of the auxiliary vacuum circuit breaker is energized, the auxiliary vacuum circuit breaker trips.

[0065] After the closing coil HQ2 of the auxiliary vacuum circuit breaker is energized, the auxiliary vacuum circuit breaker closes.

[0066] The normally open contact of the auxiliary vacuum circuit breaker is the status contact of the auxiliary vacuum circuit breaker. When the auxiliary vacuum circuit breaker is open, the normally open contact is disconnected; when the auxiliary vacuum circuit breaker is closed, the normally open contact is closed.

[0067] The normally closed node of the auxiliary vacuum circuit breaker is the status node of the auxiliary vacuum circuit breaker. When the auxiliary vacuum circuit breaker is open, the normally closed node is closed; when the auxiliary vacuum circuit breaker is closed, the normally closed node is open.

[0068] Valve normal signal node: When the valve normal signal is valid, the valve normal signal node is closed; when the valve normal signal is invalid, the valve normal signal node is open.

[0069] like Figure 1 As shown, the circuit breaker operation overvoltage elimination system provided in this embodiment of the invention further includes a valve status monitoring voltage transformer and a valve status detection unit; wherein,

[0070] The high-voltage terminal of the valve status monitoring voltage transformer is connected in parallel with the optically triggered thyristor valve body, and the low-voltage terminal of the valve status monitoring voltage transformer is connected to the input terminal of the valve status detection unit; the output terminal of the valve status detection unit is connected to the valve normal signal node.

[0071] Specifically, the valve status monitoring voltage transformer includes an A-phase valve status monitoring voltage transformer, a B-phase valve status monitoring voltage transformer, and a C-phase valve status monitoring voltage transformer. Each of the A-phase, B-phase, and C-phase valve status monitoring voltage transformers is composed of two single-phase electromagnetic voltage transformers connected in series. The common terminal of the two single-phase electromagnetic voltage transformers is connected to the intermediate node of multiple series-connected valve body components of the optically triggered thyristor valve body.

[0072] Specifically, such as Figure 1 As shown, the voltage transformer for monitoring the A-phase valve status consists of two single-phase electromagnetic voltage transformers. One transformer has secondary low-voltage terminals A41 and A42, and primary high-voltage terminals A45 and A46. The other transformer has secondary low-voltage terminals A43 and A44, and primary high-voltage terminals A47 and A48. The primary side terminals A46 of one transformer and A47 of the other transformer are connected to a common terminal A49.

[0073] The voltage transformer for monitoring the B-phase valve status consists of two single-phase electromagnetic voltage transformers. One transformer has secondary low-voltage terminals B41 and B42, and primary high-voltage terminals B45 and B46. The other transformer has secondary low-voltage terminals B43 and B44, and primary high-voltage terminals B47 and B48. The primary side terminals B46 of one transformer and B47 of the other transformer are connected to a common terminal B49.

[0074] The C-phase valve status monitoring voltage transformer consists of two single-phase electromagnetic voltage transformers. One transformer has secondary low-voltage terminals C41 and C42, and primary high-voltage terminals C45 and C46. The other transformer has secondary low-voltage terminals C43 and C44, and primary high-voltage terminals C47 and C48. The primary side terminals C46 of one transformer and C47 of the other transformer are connected to a common terminal C49.

[0075] Specifically, terminal A45 of the A-phase valve status monitoring voltage transformer is connected to terminal A3+ of the A-phase optical trigger thyristor valve body; terminal A49 of the A-phase valve status monitoring voltage transformer is connected to the intermediate node A3 of the A-phase optical trigger thyristor valve body; and terminal A48 of the A-phase valve status monitoring voltage transformer is connected to terminal A3- of the A-phase optical trigger thyristor valve body.

[0076] Terminal B45 of the B-phase valve status monitoring voltage transformer is connected to terminal B3+ of the upper part of the B-phase optical trigger thyristor valve body; terminal B49 of the B-phase valve status monitoring voltage transformer is connected to the middle node B3 of the B-phase optical trigger thyristor valve body; terminal B48 of the B-phase valve status monitoring voltage transformer is connected to terminal B3- of the lower part of the B-phase optical trigger thyristor valve body.

[0077] Terminal C45 of the C-phase valve status monitoring voltage transformer is connected to terminal C3+ of the upper part of the C-phase optically triggered thyristor valve body; terminal C49 of the C-phase valve status monitoring voltage transformer is connected to the middle node C3 of the C-phase optically triggered thyristor valve body; terminal C48 of the C-phase valve status monitoring voltage transformer is connected to terminal C3- of the lower part of the C-phase optically triggered thyristor valve body.

[0078] Specifically, such as Figure 1 As shown, the input current port UA1 of the valve status detection unit is connected to terminals A41 and A42 of the A-phase valve status monitoring voltage transformer, UA2 is connected to terminals A43 and A44 of the A-phase valve status monitoring voltage transformer, UB1 is connected to terminals B41 and B42 of the B-phase valve status monitoring voltage transformer, UB2 is connected to terminals B43 and B44 of the B-phase valve status monitoring voltage transformer, UC1 is connected to terminals C41 and C42 of the C-phase valve status monitoring voltage transformer, and UC2 is connected to terminals C43 and C44 of the C-phase valve status monitoring voltage transformer.

[0079] The valve status detection unit outputs a passive status node as a normal valve signal node, which is then output to the auxiliary circuit breaker tripping circuit of the circuit breaker operating circuit. Specifically, one end of the valve status detection unit's output is connected to the control bus +KM, and the other end is connected to the normally open node (FZ normally open) of the auxiliary vacuum circuit breaker.

[0080] The present invention provides a circuit breaker operation overvoltage elimination system. Before the system is connected to the power supply system, when the closing coil HQ1 of the main circuit vacuum circuit breaker is energized (manual closing / remote closing / reclosing node (i.e., Figure 1When the main circuit closing node is closed and the main circuit vacuum circuit breaker is in the open state (DL normally closed node closed), the main circuit vacuum circuit breaker closes, and the working power supply side terminals A1+, B1+, and C1+ are connected to the load side terminals A1-, B1-, and C1- respectively. The three-phase voltage source supplies power to the LF furnace through the LF furnace transformer. When the main circuit vacuum circuit breaker tripping coil TQ1 is energized (manual trip / remote trip / protection tripping node closed, and the main circuit vacuum circuit breaker is in the closed state (the normally open node of the main circuit vacuum circuit breaker closed)), the main circuit vacuum circuit breaker opens, and the working power supply side terminals A1+, B1+, and C1+ are disconnected from the load side terminals A1-, B1-, and C1- respectively. The LF furnace transformer and the LF furnace are de-energized.

[0081] After the circuit breaker operation overvoltage elimination system provided in this embodiment of the invention is connected to the power supply system, the closing control and operation sequence of the main circuit vacuum circuit breaker remain unchanged, so the power-on process will not be described again; in order to eliminate the operation overvoltage, when the main circuit vacuum circuit breaker is opened, it will be performed according to the following process. (At this time, the main circuit vacuum circuit breaker is in the closed state, the FZ auxiliary vacuum circuit breaker is in the open state, and the A / B / C three-phase optically triggered thyristor valve bodies are all in the locked state.)

[0082] Specifically, Figure 2 This is a flowchart illustrating an operation method for a circuit breaker operation overvoltage elimination system according to an embodiment of the present invention. Figure 2 As shown, the method specifically includes the following steps:

[0083] Step S202: Control the main circuit trip node to close, energize the closing coil of the auxiliary vacuum circuit breaker, and close the auxiliary vacuum circuit breaker;

[0084] In step S204, the circuit breaker detection and trigger signal generation unit generates a high-level electrical signal of a preset time length and converts the high-level electrical signal into a trigger optical signal;

[0085] Step S206: The trigger optical signal is transmitted to the gate input terminal of the optical trigger thyristor valve body through the beam splitter, so that the optical trigger thyristor valve body enters the trigger waiting state;

[0086] In step S208, the normally open contact of the auxiliary vacuum circuit breaker closes, the closing coil of the main circuit vacuum circuit breaker is energized, and the main circuit vacuum circuit breaker opens.

[0087] In step S210, the optically triggered thyristor valve body is turned on to eliminate overvoltage, and after a preset time length, the optically triggered thyristor valve body current turns off when it crosses zero.

[0088] Step S212: Obtain the valve terminal voltage of the optically triggered thyristor valve body based on the valve status monitoring voltage transformer, and perform valve group status detection on the optically triggered thyristor valve body based on the valve status detection unit.

[0089] Step S214: If the valve group status detection result is normal, the normal signal node of the control valve is closed, the trip coil of the auxiliary vacuum circuit breaker is energized, and the auxiliary vacuum circuit breaker is tripped.

[0090] Specifically, in step S212, the valve group status detection based on the valve status detection unit for the optically triggered thyristor valve body further includes the following steps:

[0091] Determine whether multiple voltage criteria conditions are met simultaneously; if yes, determine that the valve group status detection result is normal; if no, determine that the valve group status detection result is abnormal.

[0092] Among them, several voltage criterion conditions include:

[0093]

[0094] In the formula, , , These represent the induced voltage values ​​corresponding to the voltage division of the upper half of the valve string in the A-phase, B-phase, and C-phase optically triggered thyristor valve bodies, respectively. , , These are the induced voltage values ​​corresponding to the voltage division of the lower half of the valve string in the A-phase, B-phase, and C-phase optically triggered thyristor valve bodies, respectively. N It is the rated voltage of the power supply system, K1 and K2 are preset criterion coefficients, and pu is the per-unit value of the power system.

[0095] Figure 3 This is a flowchart of an operation method for an overvoltage elimination system for circuit breaker operation provided by an embodiment of the present invention. Figure 3 As shown, the process includes the following:

[0096] Step 1: Close the auxiliary vacuum circuit breaker:

[0097] When the LF refining furnace needs to be de-energized, the manual / remote / protective trip point of the main circuit breaker trip circuit (i.e., Figure 1 When the main circuit tripping node is closed, the normally open node of the main circuit vacuum circuit breaker is closed, and the normally open node of the auxiliary vacuum circuit breaker is open. Therefore, the tripping coil TQ1 of the main circuit vacuum circuit breaker will not be energized at this time. However, the normally closed node of the auxiliary vacuum circuit breaker in the closing circuit of the auxiliary circuit breaker is closed. Therefore, the closing coil HQ2 of the auxiliary vacuum circuit breaker is energized first, and the auxiliary vacuum circuit breaker closes first.

[0098] Step 2: Generate a light-triggered thyristor valve body trigger light signal with a preset time length t:

[0099] When the closing coil HQ2 of the auxiliary vacuum circuit breaker is energized, the rising edge detection unit of the trip detection and trigger signal generation unit detects a rapidly rising electrical signal from 0 and generates a high-level signal of a preset time length t. This preset time length t is greater than the time from when the main circuit vacuum circuit breaker and the auxiliary vacuum circuit breaker receive the trip signal to when the trip action generates an operational overvoltage. The high-level signal of preset time length t is simultaneously sent to the A-phase electro-optical conversion unit, the B-phase electro-optical conversion unit, and the C-phase electro-optical conversion unit. These three units convert the electrical signal into three trigger optical signals of the same width, which are then input to the A-phase splitter, B-phase splitter, and C-phase splitter respectively via the A-phase main optical fiber, B-phase main optical fiber, and C-phase main optical fiber.

[0100] Step 3: Conversion and transmission of optical signal for triggering the thyristor valve body:

[0101] Phase A splitter outputs LA1- to Phase A optical trigger thyristor valve body TA1-, LA1+ to Phase A optical trigger thyristor valve body TA1+, LA2- to Phase A optical trigger thyristor valve body TA2-, LA2+ to Phase A optical trigger thyristor valve body TA2+, ..., LAn- to Phase A optical trigger thyristor valve body TAn-, LAn+ to Phase A optical trigger thyristor valve body TAn+. Phase B splitter outputs LB1- to Phase B optical trigger thyristor valve body TB1-, LB1+ to Phase B optical trigger thyristor valve body TB1+, LB2- to Phase B optical trigger thyristor valve body TB2-, LB2+ to Phase B optical trigger thyristor valve body TB2+, ..., LBn- to Phase B optical trigger thyristor valve body TBn-, LBn+ to Phase B optical trigger thyristor valve body TBn+. The C-phase splitter outputs LC1- to C-phase optical trigger thyristor valve body TC1-, LC1+ to C-phase optical trigger thyristor valve body TC1+, LC2- to C-phase optical trigger thyristor valve body TC2-, LC2+ to C-phase optical trigger thyristor valve body TC2+, ..., LCn- to C-phase optical trigger thyristor valve body TCn-, and LCn+ to C-phase optical trigger thyristor valve body TCn+.

[0102] Step 4: The optically triggered thyristor valve body enters the trigger waiting state.

[0103] Although step 3 has sent the trigger optical signal to the gate of each thyristor in the A / B / C three-phase optically triggered thyristor valve body assembly, the voltage between the thyristor anode A and cathode K is approximately zero because the main circuit vacuum circuit breaker has not yet tripped, thus lacking conduction time. Since the thyristor trigger pulse duration is a preset time length t, the optically triggered thyristor valve body can enter the conduction state as long as a voltage appears across it within this specific time period. During this stage, the optically triggered thyristor valve body is in a ready-to-conduct state.

[0104] Step 5: Open the main circuit vacuum circuit breaker:

[0105] When the closing coil HQ2 of the auxiliary vacuum circuit breaker is energized, the auxiliary vacuum circuit breaker closes, the normally open contact of the auxiliary vacuum circuit breaker closes and the normally closed contact opens, thus the tripping circuit of the main circuit breaker is connected, the tripping coil TQ1 of the main circuit vacuum circuit breaker is energized, and the main circuit vacuum circuit breaker trips.

[0106] Step 6: Optically trigger thyristor valve body to conduct:

[0107] After the main circuit vacuum circuit breaker trips, the A / B / C three-phase optically triggered thyristor valve bodies, which are in the trigger waiting state, are all ready to conduct. The thyristors in each phase valve body that are under positive pressure conduct. Taking phase A as an example, either TA1-, TA2-...TAn- conduct simultaneously, or TA1+, TA2+...TAn+ conduct.

[0108] The tripping of the main circuit vacuum circuit breaker generates a certain voltage, which is far lower than the overvoltage generated before the application of this invention. This causes the thyristor to turn on, eliminating the overvoltage. After the high-level signal of the preset time length t ends, the thyristor current crosses zero and automatically turns off, preventing overvoltage. This invention fundamentally eliminates the overvoltage problem caused by frequent operation of the vacuum circuit breaker in the LF refining furnace.

[0109] Step 7: Optically triggered thyristor valve body status detection:

[0110] After the main circuit vacuum circuit breaker is tripped, the optically triggered thyristor valve body conducts briefly and turns off automatically when crossing zero. Then, a voltage appears at the valve terminal, and the voltage of each phase is evenly distributed on each valve body component of the corresponding phase valve body. At this time, the optically triggered thyristor valve body status detection stage is entered.

[0111] The voltage transformer for monitoring the valve status of phase A senses the voltage induced at terminals A41 and A42, corresponding to the voltage division of the upper half of the valve string in phase A. Terminals A43 and A44 sense the voltage induced at terminals A43 and A44, corresponding to the voltage division of the lower half of the valve string in phase A. Similarly, the voltage transformer for monitoring the valve status of phase B senses the voltage induced at terminals B41 and B42, corresponding to the voltage division of the upper half of the valve string in phase B. Terminals B43 and B44 sense the voltage induced at terminals B43 and B44, corresponding to the voltage division of the lower half of the valve string in phase B. Likewise, the voltage transformer for monitoring the valve status of phase C senses the voltage induced at terminals C41 and C42, corresponding to the voltage division of the upper half of the valve string in phase C. Terminals A43 and A44 sense the voltage induced at terminals A43 and A44, corresponding to the voltage division of the lower half of the valve string in phase C.

[0112] The valve status monitoring unit determines whether the valve body is normal based on the above six voltage indicators and the following five criteria.

[0113]

[0114] If the above five voltage criteria are met simultaneously within time T (the length of time T is adjustable, preferably not less than 1 minute), the valve normal signal is set to the valid position, and the corresponding valve normal signal node is closed; if the conditions are not met, the valve normal signal is set to the invalid position, and the corresponding valve normal signal node is opened.

[0115] If voltage criterion condition 3 is not met, an A-phase optical trigger thyristor valve body abnormality signal will be issued simultaneously; furthermore, when At that time, an alarm message is issued indicating an abnormality in the upper layer of the A-phase light-triggered thyristor valve body. At that time, an alarm message is issued indicating an abnormality in the lower layer of the A-phase light-triggered thyristor valve body;

[0116] If voltage criterion condition 4 is not met, a B-phase optical trigger thyristor valve body abnormality signal will be issued simultaneously; furthermore, when At that time, an alarm message indicating an abnormality in the upper layer of the B-phase light-triggered thyristor valve body is issued. At that time, an alarm message is issued indicating an abnormality in the lower layer of the B-phase light-triggered thyristor valve body;

[0117] If voltage criterion condition 5 is not met, a C-phase optical trigger thyristor valve body abnormality signal will be issued simultaneously; furthermore, when At that time, an alarm message is issued indicating an abnormality in the upper layer of the C-phase light-triggered thyristor valve body. At that time, an alarm message is issued indicating an abnormality in the lower layer of the C-phase light-triggered thyristor valve body.

[0118] Step 8: Auxiliary vacuum circuit breaker trips:

[0119] When the valve normal signal is set to the valid position, and the corresponding valve normal signal node is closed, the normally open node of the auxiliary vacuum circuit breaker is also closed. Then the trip coil TQ2 of the auxiliary vacuum circuit breaker is energized, and the auxiliary vacuum circuit breaker trips.

[0120] After the above 8 steps, the main circuit vacuum circuit breaker tripped, the auxiliary vacuum circuit breaker tripped, the valve group lost power, and the LF refining furnace power supply system was completely de-energized. Although the power outage time increased by approximately t+T (t is the thyristor trigger current-carrying time, i.e. the preset time length, and T is the thyristor valve group detection time), no operational overvoltage was generated during the entire power outage process, achieving the expected goal.

[0121] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only one preferred embodiment of this invention and are only used to explain this invention. They do not limit the scope of protection of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0122] (1) Typical case equipment parameters:

[0123] Example 1: The 110kV main substation supplies power to two 150T refining furnaces. The 110kV side of the main substation adopts a single busbar connection. The three-phase short-circuit capacity is 1500MVA. Based on the short-circuit capacity and its equivalent to the external power grid, the equivalent parameters are as follows:

[0124] Operating voltage: 115kV;

[0125] Rated frequency: 50Hz;

[0126] Equivalent resistance: 0.8Ω;

[0127] Equivalent inductance: 25.68mH;

[0128] The transformer has a capacity of 50MVA and is an oil-immersed three-phase double-winding on-load tap-changing transformer. Its main parameters are as follows:

[0129] Transformer model: SFZ20-50000 / 110 (Level 3 energy efficiency);

[0130] Voltage ratio: 115±8×1.25% / 36.5kV;

[0131] Rated capacity: 50MVA;

[0132] Impedance voltage: 10.5%;

[0133] Connection group: YNd11;

[0134] The power supply cable is 500m long, model ZC-YJLHY23-26 / 35kV-3×240, and its main parameters are as follows:

[0135] Resistance per unit length: 0.04Ω / kM;

[0136] Reactance per unit length: 0.1Ω / kM;

[0137] Resistance to ground per unit length: 0.02 MΩ / kM;

[0138] The LF refining furnace transformer has a rated capacity of 20MVA and its main parameters are as follows:

[0139] Model: HBSSPZ-20000 / 35;

[0140] Rated capacity: 20000kVA;

[0141] Overload capacity 20%;

[0142] Rated primary voltage: 35kV;

[0143] Rated secondary voltage: 360~290~210V;

[0144] Impedance voltage: 8%;

[0145] Voltage regulation method: Electric on-load 13-level voltage regulation;

[0146] Linkage group label: Yd11;

[0147] Cable entry / exit method: Top in, side out;

[0148] Structural form: Inner closed triangle;

[0149] Cooling methods: OFWF, dual-pipe type;

[0150] The equivalent impedance of the LF furnace under load is 0.008Ω.

[0151] The actual parameters used in the circuit breaker operation overvoltage elimination system provided in this embodiment of the invention are as follows:

[0152] Thyristor model: T1503NH (Infineon);

[0153] Thyristor valve layer n: 16 layers;

[0154] Dynamic voltage equalization capacitor: 1.5uF / 4000V;

[0155] Dynamic voltage equalization resistor: 60Ω / 3kW;

[0156] Static voltage equalization resistor: 50kΩ / 80W;

[0157] Delay time t: 10ms;

[0158] Valve status detection time T: 1 minute;

[0159] The constant coefficient K1 is 0.1.

[0160] The constant coefficient K2 is 0.1.

[0161] The thyristor is an optically triggered thyristor with a repetitive forward and reverse voltage withstand capability of 7500V and a half-wave current RMS value of 1770A. It features built-in overvoltage protection via a transition diode. When the voltage at the thyristor terminals exceeds the overvoltage protection trip value of the transition diode, the transition diode conducts, providing a protection trigger signal to the thyristor and preventing damage from overvoltage.

[0162] (2) Typical case operation results:

[0163] Based on the above equipment parameters, an operational overvoltage simulation model was built in the electromagnetic simulation software PSCAD, as shown in the attached figure. Figure 4 As shown.

[0164] Taking the tripping operation of the No. 2 refining furnace as an example, the overvoltage value during the tripping operation is illustrated. Without using the circuit breaker operation overvoltage elimination system provided in this embodiment, there is no operation overvoltage when the vacuum circuit breaker has no current cutoff. As the current cutoff value increases, the operation overvoltage value increases accordingly, and the overvoltage amplitude is directly proportional to the current cutoff value of the vacuum circuit breaker. When the current cutoff value is 300A, a peak operation overvoltage of approximately 160kV with rapid decay was generated during the tripping operation of the vacuum circuit breaker of the No. 2 refining furnace at 2 seconds. This overvoltage value is relatively high and propagates along the power distribution line in the network, generating similar overvoltages on the 35kV side of the total drop and the 35kV side of the No. 1 furnace. If there are weak points in the insulation, breakdown and discharge will occur, damaging the insulation and even developing into a stable short-circuit fault, causing equipment outage. The voltage and current waveforms corresponding to this operation are as follows: Figure 5 As shown, the waveforms include “35kV side voltage waveform of No. 1 LF furnace transformer”, “35kV side voltage waveform of No. 2 LF furnace transformer”, “35kV side current waveform of No. 1 LF furnace transformer” and “35kV side current waveform of No. 2 LF furnace transformer”.

[0165] After using the circuit breaker overvoltage elimination system provided in this embodiment of the invention, with the system and load parameters unchanged and the current-cutting value of the vacuum circuit breaker remaining consistent, a simulation is performed again. The simulation interface is as follows: Figure 6 As shown in the figure, there are a large number of thyristors. An equivalent modeling method is used, with every four strings of thyristors equivalent to one string in the model. The vacuum circuit breaker has a current-cutting value of 300A. At 2 seconds, the vacuum circuit breaker of refining furnace #2 issues a tripping command. The rising edge detection unit of the tripping detection and trigger signal generation unit in this invention detects a rapidly rising step signal from 0 at 2 seconds and synchronously generates a high-level signal with a fixed time width t (t=10ms in this embodiment). The signal is shown in the attached figure. Figure 7 As shown. The signal is simultaneously sent to the A-phase electro-optical conversion unit, the B-phase electro-optical conversion unit, and the C-phase electro-optical conversion unit. These three units convert the electrical signal into three optical signals of the same width, which are then input to the A-phase splitter, B-phase splitter, and C-phase splitter respectively via the A-phase main optical fiber, B-phase main optical fiber, and C-phase main optical fiber. The A-phase splitter, B-phase splitter, and C-phase splitter synchronously send a 10ms gate turn-on signal to the thyristor devices connected in reverse parallel across all layers of the three-phase valve body. After the main circuit vacuum circuit breaker trips, the thyristors that meet the conditions turn on, and the three-phase current of the thyristor valve body is triggered by light, as shown in the attached diagram. Figure 8 As shown in the figure. The simulation results show that after the main circuit vacuum circuit breaker is tripped, the three-phase thyristors are turned on simultaneously. After 10ms, the first thyristor with the current crossing zero is turned off first, and then the other two thyristors are turned off simultaneously at the subsequent current crossing zero point. The longest conduction time is less than 20ms.

[0166] After the thyristor turns off at zero crossing, the valve group status detection phase begins. In this embodiment, no damaged thyristor is configured; therefore, the three-phase calculation results fully satisfy the criteria.

[0167]

[0168] One minute later, the valve normal signal is set to the valid position. After the corresponding valve normal signal node is closed, the normally open node of the auxiliary vacuum circuit breaker is also in the closed position. Then the trip coil TQ2 of the auxiliary vacuum circuit breaker is energized, and the auxiliary vacuum circuit breaker trips.

[0169] The voltage and current waveforms corresponding to this operation are as follows: Figure 9 The waveforms shown include the voltage waveforms on the 35kV side of the #1 LF furnace transformer, the voltage waveforms on the 35kV side of the #2 LF furnace transformer, the current waveforms on the 35kV side of the #1 LF furnace transformer, and the current waveforms on the 35kV side of the #2 LF furnace transformer. Simulation results of the voltage and current waveforms at different electrical nodes show that, after adopting the system provided in this embodiment of the invention, the current turn-off time of the #2 LF furnace is delayed by 18ms, all three-phase currents are zero-crossing turn-off, and there is no operational overvoltage, fundamentally solving the overvoltage problem and achieving the expected goal.

[0170] As can be seen from the above description, the circuit breaker operation overvoltage elimination system and operation method provided by the embodiments of the present invention have the following technical effects compared with the prior art:

[0171] (1) This invention can fundamentally solve the problem of frequent operation of the vacuum circuit breaker of LF refining furnace causing overvoltage to threaten equipment insulation and cause system interference. It replaces the RC absorption circuit, thereby eliminating the risks of increased loss, system resonance, harmonic amplification and other risks caused by multiple RC configurations in the system. It also saves space in the power distribution cabinet and simplifies the selection and design of surge arresters.

[0172] (2) This invention not only eliminates overvoltage during circuit breaker tripping but also prevents arcing in the circuit breaker, thus increasing the service life of the equipment. It is understood that due to the frequent operation and large voltage surges of the LF refining furnace vacuum circuit breaker, and the frequent arcing of the contacts, its service life is relatively low, and it is generally replaced once a year. After adopting the system provided in this embodiment of the invention, it is expected that the replacement cycle of the circuit breaker can be increased from once a year to once every five years.

[0173] (3) The present invention does not change the wiring method of the existing power distribution device and load. The detection signal is taken from both ends of the trip coil of the auxiliary circuit breaker. The thyristor valve body is connected in parallel to the first and second ends of the vacuum circuit breaker. All of them are parallel connections.

[0174] (4) In the newly added equipment of the present invention, the circuit breaker detection and trigger signal generation unit at low potential, the optical splitter at high potential and the optical trigger thyristor valve body are all connected by optical fiber. The optical fiber has good anti-electromagnetic interference capability and good insulation performance, thus realizing electrical insulation between high and low potentials.

[0175] (5) The thyristor valve body in the newly added equipment of this invention uses a light-triggered thyristor, eliminating the need for a high-potential board and removing high-potential functional circuits such as power extraction, status detection, and status return. This simplifies the electrical and functional design of the valve body to the greatest extent, thereby reducing failure points and improving the reliability of equipment operation. The light-triggered thyristor has a built-in overvoltage protection switch diode, simplifying the protection of valve body components. When the voltage at the thyristor terminal exceeds the overvoltage protection action value of the switch diode, the switch diode conducts, providing a protection trigger signal to the thyristor and preventing the thyristor from being damaged by overvoltage. Therefore, the valve body used in this invention eliminates the valve control protection system, requiring only a simple signal detection and light system to achieve the expected goals.

[0176] (6) The valve body of the present invention has a self-detection function. When the thyristor inside the valve body is damaged, the fault can be quickly identified through the thyristor status monitoring circuit, and the damaged thyristor area can be quickly located, which improves the automation and intelligence level of the thyristor valve body operation.

[0177] (7) The present invention adopts a short-time operation mode, and the thyristor only carries current for less than one cycle (20ms) in each working cycle. Therefore, there is no need for a complex cooling system. The thyristor working current can be designed to withstand one surge current. There is no need to consider the residual heat and temperature after the last operation, thus eliminating the need for heat dissipation system design.

[0178] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0179] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A circuit breaker operation overvoltage elimination system, characterized in that, This system is applied to a power supply system, which includes a working power supply and a main circuit vacuum circuit breaker. The upper and lower terminals of the main circuit vacuum circuit breaker are respectively connected to the positive terminal of the working power supply and the load. The circuit breaker operation overvoltage elimination system includes: an auxiliary vacuum circuit breaker, a light-triggered thyristor valve body, a trip detection and trigger signal generation unit, a beam splitter, and a circuit breaker operation circuit. The upper and lower terminals of the auxiliary vacuum circuit breaker are respectively connected to the upper terminal of the main circuit vacuum circuit breaker and the upper terminal of the optically triggered thyristor valve body, and the lower terminal of the optically triggered thyristor valve body is connected to the lower terminal of the main circuit vacuum circuit breaker; The optically triggered thyristor valve body includes multiple valve body assemblies connected in series, and each valve body assembly includes two optically triggered thyristors connected in parallel with opposite directions; The circuit breaker operating circuit includes a main circuit breaker tripping circuit and an auxiliary circuit breaker closing circuit; the main circuit breaker tripping circuit includes a main circuit tripping node, a normally open node of the main circuit vacuum circuit breaker, a normally open node of the auxiliary vacuum circuit breaker, and a tripping coil of the main circuit vacuum circuit breaker connected in series; the auxiliary circuit breaker closing circuit includes a normally closed node of the auxiliary vacuum circuit breaker and a closing coil of the auxiliary vacuum circuit breaker connected in parallel across the normally open node of the auxiliary vacuum circuit breaker and the tripping coil of the main circuit vacuum circuit breaker. The input terminal of the trip detection and trigger signal generation unit is connected in parallel with the closing coil of the auxiliary vacuum circuit breaker. The output terminal of the trip detection and trigger signal generation unit outputs a trigger optical signal. The trigger optical signal is connected to the input terminal of the optical splitter through the output optical fiber. The output terminal of the optical splitter is connected to the gate input terminal of the optical trigger thyristor.

2. The circuit breaker operation overvoltage elimination system according to claim 1, characterized in that: The main circuit vacuum circuit breaker and the auxiliary vacuum circuit breaker each include an A-phase switch, a B-phase switch, and a C-phase switch; the optically triggered thyristor valve body includes an A-phase optically triggered thyristor valve body, a B-phase optically triggered thyristor valve body, and a C-phase optically triggered thyristor valve body; wherein, each of the A-phase optically triggered thyristor valve body, the B-phase optically triggered thyristor valve body, and the C-phase optically triggered thyristor valve body includes an even number of valve body assemblies connected in series; The upper terminal of the A-phase optically triggered thyristor valve body is connected to the lower terminal of the A-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal of the A-phase optically triggered thyristor valve body is connected to the lower terminal of the A-phase switch of the main circuit vacuum circuit breaker. The upper terminal of the B-phase optically triggered thyristor valve body is connected to the lower terminal of the B-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal of the B-phase optically triggered thyristor valve body is connected to the lower terminal of the B-phase switch of the main circuit vacuum circuit breaker. The upper terminal of the C-phase optically triggered thyristor valve body is connected to the lower terminal of the C-phase switch of the auxiliary vacuum circuit breaker, and the lower terminal of the C-phase optically triggered thyristor valve body is connected to the lower terminal of the C-phase switch of the main circuit vacuum circuit breaker.

3. The circuit breaker operation overvoltage elimination system according to claim 1 or 2, characterized in that: The valve body assembly further includes a static voltage equalizing resistor, a dynamic voltage equalizing resistor, and a dynamic voltage equalizing capacitor; the static voltage equalizing resistor is connected in parallel with the two optically triggered thyristors, and the dynamic voltage equalizing resistor and the dynamic voltage equalizing capacitor are connected in series and then connected in parallel with the two optically triggered thyristors.

4. The circuit breaker operation overvoltage elimination system according to claim 2, characterized in that: The beam splitter includes an A-phase beam splitter, a B-phase beam splitter, and a C-phase beam splitter; wherein... The A-phase splitter, the B-phase splitter, and the C-phase splitter each have multiple optical output ports, which are respectively connected to the gate input terminals of multiple valve body components of the A-phase optical trigger thyristor valve body, the B-phase optical trigger thyristor valve body, and the C-phase optical trigger thyristor valve body.

5. The circuit breaker operation overvoltage elimination system according to claim 1, characterized in that: The circuit breaker tripping detection and trigger signal generation unit includes a rising edge detection unit and an electro-optical conversion unit; wherein... The rising edge detection unit is used to output a high-level electrical signal of a preset time length after detecting that the closing coil of the auxiliary vacuum circuit breaker is energized. The electro-optic conversion unit is used to convert the high-level electrical signal into a trigger optical signal.

6. The circuit breaker operation overvoltage elimination system according to claim 1, characterized in that: The circuit breaker operating circuit also includes an auxiliary circuit breaker tripping circuit and a main circuit breaker closing circuit; wherein... The auxiliary circuit breaker tripping circuit includes a valve normal signal node, a normally open node of the auxiliary vacuum circuit breaker, and a tripping coil of the auxiliary vacuum circuit breaker connected in series. The main circuit breaker closing circuit includes a main circuit closing node, a normally closed node of the main circuit vacuum circuit breaker, and a closing coil of the main circuit vacuum circuit breaker connected in series.

7. The circuit breaker operation overvoltage elimination system according to claim 6, characterized in that: It also includes a valve condition monitoring voltage transformer and a valve condition detection unit; among which, The high-voltage terminal of the valve status monitoring voltage transformer is connected in parallel with the optically triggered thyristor valve body, and the low-voltage terminal of the valve status monitoring voltage transformer is connected to the input terminal of the valve status detection unit; the output terminal of the valve status detection unit is connected to the valve normal signal node.

8. The circuit breaker operation overvoltage elimination system according to claim 7, characterized in that: The valve status monitoring voltage transformer includes an A-phase valve status monitoring voltage transformer, a B-phase valve status monitoring voltage transformer, and a C-phase valve status monitoring voltage transformer. Each of the A-phase, B-phase, and C-phase valve status monitoring voltage transformers is composed of two single-phase electromagnetic voltage transformers connected in series. The common terminal of the two single-phase electromagnetic voltage transformers is connected to the intermediate node of multiple series-connected valve body components of the optically triggered thyristor valve body.

9. An operating method for the circuit breaker operation overvoltage elimination system as described in claim 7, characterized in that, include: The main circuit tripping node is closed, the closing coil of the auxiliary vacuum circuit breaker is energized, and the auxiliary vacuum circuit breaker is closed. The circuit breaker detection and trigger signal generation unit generates a high-level electrical signal of a preset time length and converts the high-level electrical signal into a trigger optical signal; The trigger optical signal is transmitted to the gate input terminal of the optical trigger thyristor valve body through the beam splitter, so that the optical trigger thyristor valve body enters the trigger waiting state; When the normally open contact of the auxiliary vacuum circuit breaker closes, the closing coil of the main circuit vacuum circuit breaker is energized, and the main circuit vacuum circuit breaker opens. The optically triggered thyristor valve body is turned on to eliminate overvoltage, and after the preset time length, the optically triggered thyristor valve body current turns off at zero. The valve terminal voltage of the optically triggered thyristor valve body is obtained based on the valve status monitoring voltage transformer, and the valve group status is detected based on the valve status detection unit. If the valve group status detection result is normal, the normal signal node of the control valve is closed, the trip coil of the auxiliary vacuum circuit breaker is energized, and the auxiliary vacuum circuit breaker is tripped.

10. The operating method according to claim 9, characterized in that: Based on the valve state detection unit, valve group state detection is performed on the optically triggered thyristor valve body, including: Determine whether multiple voltage criteria conditions are met simultaneously; if yes, determine that the valve group status detection result is normal; if no, determine that the valve group status detection result is abnormal. The plurality of voltage criterion conditions include: In the formula, , , These represent the induced voltage values ​​corresponding to the voltage division of the upper half of the valve string in the A-phase, B-phase, and C-phase optically triggered thyristor valve bodies, respectively. , , These are the induced voltage values ​​corresponding to the voltage division of the lower half of the valve string in the A-phase, B-phase, and C-phase optically triggered thyristor valve bodies, respectively. N K1 and K2 are the rated voltage of the power supply system, K1 and K2 are preset criterion coefficients, and pu is the per-unit value of the power system.

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