Short-circuit current suppression device for variable-impedance superconducting current-limiting transformer and application method of short-circuit current suppression device
The variable impedance superconducting current limiting transformer automatically loses over and changes into a resistive state after a short circuit fault and uses a fast switch to remove the parallel branch. Combined with the series structure of the main current limiting and auxiliary winding, the high-amplitude asymmetric short-circuit current in the power grid is solved. Suppressing difficulties has achieved improvements in the safety and stability of the power system.
Patent Information
- Application Number
- CN202411346992.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-26
- Publication Date
- 2024-12-31
AI Technical Summary
The prior art is difficult to effectively suppress the asymmetric short-circuit current in the power grid, especially when the first current half wave cannot be limited, resulting in difficulty in circuit breaker opening and closing, affecting the safe and stable operation of the power system.
The short-circuit current suppression device of variable impedance superconducting current limit transformer is adopted. The superconducting current limit transformer will automatically lose the over-transform into a resistive state after a short-circuit fault. The parallel branch is removed by using a quick switch to double the current limiting resistance, combined with the main current limiting The series structure with the auxiliary winding realizes the suppression of short-circuit current.
It quickly and greatly suppresses short-circuit current, reduces its impact on the system, improves the safety and stability of the power system, and ensures the normal interruption of the circuit breaker.
Smart Images
Figure CN119231455A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of power systems and automation, and in particular to a short-circuit current suppression device for a variable impedance superconducting current limiting transformer and an application method thereof. Background Art
[0002] With the continuous development of the economy and society, the capacity of the power system is constantly increasing, which makes the short-circuit current amplitude of the power grid gradually increase. With the continuous development of the DC system, the access of a large number of DC makes the system time constant gradually exceed the rated breaking time constant of the circuit breaker. The high-amplitude asymmetric short-circuit current makes it difficult for the circuit breaker to break after a fault occurs. At the same time, the short-circuit DC component will also cause the iron core in the AC system to saturate, making the transformer, mutual inductor, etc. unable to work normally or the protection malfunction, seriously endangering the safe and stable operation of the power system.
[0003] At present, short-circuit current is often suppressed by means such as grid de-looping, installing series reactors and neutral point grounding reactors, but the effect is limited and cannot improve the impact of the DC component of the asymmetric short-circuit current. It is necessary to study more effective means to reduce the impact of asymmetric short-circuit current and reduce the difficulty of opening circuit breakers.
[0004] Chinese patent application CN114844022A uses a fast switch to put in a current limiting reactor after detecting a short-circuit current to achieve current limiting, but current limiting can only be achieved after the circuit breaker is disconnected, so the short-circuit current suppression effect is poor, especially in the first current half-wave. Therefore, how to improve the current limiting effect of the short-circuit current and enhance the safety of the circuit system is a technical problem that needs to be solved. Summary of the invention
[0005] The purpose of the present invention is to provide a short-circuit current suppression device for a variable impedance superconducting current limiting transformer and an application method thereof in order to overcome the defects of the above-mentioned prior art. The short-circuit current first half-wave peak value is suppressed by the resistance after the superconducting current limiting transformer automatically quenches. After a short-circuit fault is detected, the quench resistance is doubled by the rapid switch opening under the joint action of the main current limiting branch and the auxiliary winding, thereby achieving the effect of suppressing the short-circuit current.
[0006] The purpose of the present invention can be achieved by the following technical solutions:
[0007] According to one aspect of the present invention, a variable impedance superconducting current limiting transformer short-circuit current suppression device is provided, comprising a superconducting current limiting transformer module, a fault detection and judgment module and a circuit breaker.
[0008] The superconducting current limiting transformer module includes a low-temperature dewar, a high-voltage winding, a low-voltage winding, an auxiliary winding, a lead-out tap and a fast switch. The high-voltage winding, the low-voltage winding and the auxiliary winding are all immersed in the coolant inside the low-temperature dewar and are led out through the lead-out tap. The low-voltage winding includes a main current-carrying winding and a main current-limiting winding arranged in parallel. The main current-carrying winding and the main current-limiting winding are respectively connected in series with the auxiliary winding. The fast switch is connected in series with the main current-carrying branch and then in parallel with the main current-limiting branch.
[0009] The fault detection module includes a current detection unit, a temperature detection unit and a fault judgment unit.
[0010] Furthermore, the winding parameters of the main current-passing winding and the main current-limiting winding are the same. The winding directions of the main current-limiting winding and the auxiliary winding connected in series are opposite, and the winding directions of the main current-passing winding and the auxiliary winding connected in series are the same.
[0011] The auxiliary winding includes two anti-parallel superconducting windings, and the length and number of superconducting tapes are the same. The number of parallel tapes of the two branches of the auxiliary winding is the same as that of the low-voltage winding, and the tape length is less than the length of a single tape of the low-voltage winding, which is determined by the voltage reduction after current limiting and the requirement for increasing the current limiting impedance.
[0012] The high voltage winding, low voltage winding and auxiliary winding are all superconducting windings, the high voltage winding and the low voltage winding are connected in a star or triangle manner, and the superconducting winding includes yttrium barium copper oxide YBCO or bismuth strontium calcium copper oxide BSCCO.
[0013] The superconducting winding automatically quenches under short-circuit current and turns into a resistive current limiting state. The resistance is doubled by cutting off the parallel branch through a fast switch. During normal operation, the auxiliary winding is in a non-inductive state and the voltage is 0 because the two branches are wound forward and reversely and the current is the same. When the circuit breaker is disconnected, the reverse-wound part of the auxiliary winding after the circuit breaker is disconnected will induce a voltage in the opposite direction of the main current limiting winding, which is superimposed to reduce the voltage. At the same time, the current limiting resistance after quenching is increased through the series connection of resistors.
[0014] According to another aspect of the present invention, there is provided an application method of a short-circuit current suppression device for a variable impedance superconducting current limiting transformer, the application method comprising the following steps:
[0015] S1, the fault detection and judgment module continuously samples the current and temperature signals of the variable impedance superconducting current limiting transformer;
[0016] S2, the fault detection and judgment module analyzes the sampled current and temperature data to determine whether the current magnitude and duration are greater than the expected set value;
[0017] S3, when the sampled instantaneous current value is greater than the set first protection action value and the duration is greater than the set time, or the instantaneous current value is greater than the set second protection action value, or the temperature is greater than the set protection action temperature, enter step S4, otherwise return to S2 to continue sampling;
[0018] S4, the switch is opened quickly, the main current branch of the variable impedance superconducting current limiting transformer is cut off, the auxiliary winding is decoupled, and the superconducting current limiting impedance is doubled;
[0019] S5. Under the action of the current limiting impedance, the amplitude and time constant of the asymmetric short-circuit current are greatly reduced, and the asymmetric short-circuit current is suppressed.
[0020] S6. The system circuit breaker on the short-circuit side is disconnected, the short-circuit current after current limiting is cut off, and the fault is cleared.
[0021] Furthermore, the first protection action value of the instantaneous current is an overload protection value, which is between the rated current peak value of the superconducting transformer and the total critical current of the superconducting transformer, the second protection action value is a short circuit protection value, and the first protection action value is less than the second protection action value. The protection action temperature is the maximum value of the operating temperature of the superconducting current limiting transformer, and a superconducting current limiting transformer exceeding the protection action temperature is considered to have quenched.
[0022] Compared with the prior art, the present invention has the following beneficial effects:
[0023] (1) Rapidly and greatly suppress short-circuit current: The winding automatically quenches and turns into a resistive state, and the fast switch is cut off to increase the current limiting resistance, so that the time constant of the DC component of the short-circuit current is greatly reduced and quickly decays to zero, minimizing the impact of asymmetric short-circuit current on the system.
[0024] (2) Improved current limiting effect and increased safety of the power system: By connecting an auxiliary winding in series to generate a reverse voltage and increase resistance, the current limiting effect on the short-circuit current is further improved, thereby increasing the safety and stability of the power system. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 It is a three-phase wiring topology diagram;
[0026] Figure 2 This is the current path diagram under normal working conditions;
[0027] Figure 3 This is the current path diagram after the fast switch is opened;
[0028] Figure 4 A flow chart of a method for suppressing asymmetrical short-circuit current of a variable impedance superconducting current limiting transformer;
[0029] Figure 5This is the current limiting effect diagram.
[0030] Description of the numbers in the figure:
[0031] 1. Low temperature dewar, 2. High voltage winding, 3. Low voltage winding, 4. Auxiliary winding, 5. Lead tap, 6. Fast switch, 7. Current detection unit, 8. Circuit breaker. DETAILED DESCRIPTION
[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 should fall within the scope of protection of the present invention.
[0033] like Figure 1 As shown, a variable impedance superconducting current limiting transformer short-circuit current suppression device includes a superconducting current limiting transformer module, a fault detection and judgment module and a circuit breaker 8.
[0034] Among them, the superconducting current limiting transformer module includes a low-temperature dewar 1, a high-voltage winding 2, a low-voltage winding 3, an auxiliary winding 4, a lead tap 5 and a fast switch 6. The high-voltage winding 2, the low-voltage winding 3 and the auxiliary winding 4 are all immersed in the internal coolant of the low-temperature dewar 1 and are led out through the lead tap 5. The low-voltage winding 3 includes a main current-carrying winding and a main current-limiting winding arranged in parallel. The main current-carrying winding and the main current-limiting winding are respectively connected in series with the auxiliary winding 4. The fast switch 6 is connected in series with the main current-carrying branch and then in parallel with the main current-limiting branch. The fault detection module includes a current detection unit 7, a temperature detection unit and a fault judgment unit.
[0035] The winding parameters of the main current-passing winding and the main current-limiting winding are the same. The winding directions of the main current-limiting winding and the auxiliary winding 4 connected in series are opposite, and the winding directions of the main current-passing winding and the auxiliary winding 4 connected in series are the same.
[0036] The auxiliary winding 4 includes two anti-parallel wound superconducting windings, and the length and number of superconducting tapes are the same. The number of parallel tapes of the two branches of the auxiliary winding 4 is consistent with that of the low-voltage winding, and the tape length is less than the length of a single tape of the low-voltage winding, which is determined by the voltage reduction after current limiting and the requirement for increasing the current limiting impedance.
[0037] The high voltage winding 2, the low voltage winding 3 and the auxiliary winding 4 are all superconducting windings. The high voltage winding 2 and the low voltage winding 3 are connected in a star or triangle manner. The superconducting windings include yttrium barium copper oxide YBCO or bismuth strontium calcium copper oxide BSCCO.
[0038] The superconducting winding automatically quenches under short-circuit current and turns into a resistive current limiting state. The resistance is doubled by cutting off the parallel branch through a fast switch. During normal operation, the auxiliary winding is in a non-inductive state and the voltage is 0 because the two branches are wound forward and reversely and the current is the same. When the circuit breaker is disconnected, the reverse-wound part of the auxiliary winding after the circuit breaker is disconnected will induce a voltage in the opposite direction of the main current limiting winding, which is superimposed to reduce the voltage. At the same time, the current limiting resistance after quenching is increased through the series connection of resistors.
[0039] like Figure 2 As shown, under normal operating conditions, all superconducting windings on the low-voltage side are conducting current, and since the parameters of the main current-passing branch and the main current-limiting branch are the same and they are in a current-sharing state, the auxiliary winding is in a tightly coupled state and the voltage across both ends is zero.
[0040] like Figure 3 As shown, under fault conditions, after the fast switch 6 is disconnected, the main current-passing branch connected in series with it is disconnected, and the main current-limiting winding continues to pass current, transform voltage, and limit current together with the quench resistor of the auxiliary winding, and the current-limiting impedance is doubled. At the same time, the auxiliary winding will generate a voltage in the opposite direction to the main current-limiting winding, which will reduce the voltage of the low-voltage side power supply and further enhance the current-limiting effect.
[0041] like Figure 4 As shown, an application method of a short-circuit current suppression device for a variable impedance superconducting current limiting transformer is provided, and the application method comprises the following steps:
[0042] S1, the fault detection and judgment module continuously samples the current and temperature signals of the variable impedance superconducting current limiting transformer;
[0043] S2, the fault detection and judgment module analyzes the sampled current and temperature data to determine whether the current magnitude and duration are greater than the expected set value;
[0044] S3, when the sampled instantaneous current value is greater than the set protection action value I1 and the duration is greater than the set time t1, or the instantaneous current value is greater than the set protection action value I2, or the temperature is greater than the set protection action temperature T0, enter step S4, otherwise return to S2 to continue sampling;
[0045] S4, the switch is opened quickly, the main current branch of the variable impedance superconducting current limiting transformer is cut off, the auxiliary winding is decoupled, and the superconducting current limiting impedance is doubled;
[0046] S5. Under the action of the current limiting impedance, the amplitude and time constant of the asymmetric short-circuit current are greatly reduced, and the asymmetric short-circuit current is suppressed.
[0047] S6. The system circuit breaker on the short-circuit side is disconnected, the short-circuit current after current limiting is cut off, and the fault is cleared.
[0048] Among them, the protection action value I1 of the instantaneous current is the overload protection value, and its value is between the rated current peak of the superconducting transformer and the total critical current of the superconducting transformer. The protection action value I2 is the short-circuit protection value, and I1 is less than I2. The protection action temperature T0 is the maximum operating temperature of the superconducting current limiting transformer. The superconducting current limiting transformer that exceeds the protection action temperature is considered to have quenched.
[0049] like Figure 5 As shown, time a is the time when an asymmetric short circuit fault occurs. After a short circuit occurs, an asymmetric expected short circuit current with a high DC component will be generated in the circuit. In the present invention, the variable impedance superconducting current limiting transformer performs preliminary current limiting after the first half-wave automatic quench. At the same time, after detecting the short circuit fault, the fast switch 6 opens at time b to cut off the main current branch, so that the power supply voltage is reduced and the current limiting impedance is immediately increased several times, so as to achieve deep suppression of the asymmetric short circuit current with a high DC component.
[0050] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.
Claims
1. A short-circuit current suppression device for a variable impedance superconducting current limiting transformer, characterized in that: It includes an auxiliary winding (4) connected in series with the low voltage winding (3), The device also includes a superconducting current limiting transformer module, a fault detection and judgment module and a circuit breaker (8). The superconducting current limiting transformer module comprises a low-temperature dewar (1), a high-voltage winding (2), a low-voltage winding (3), an auxiliary winding (4), a lead-out tap (5) and a fast switch (6); the high-voltage winding (2), the low-voltage winding (3) and the auxiliary winding (4) are immersed in a cooling liquid inside the low-temperature dewar (1) and are led out through the lead-out tap (5); the low-voltage winding (3) comprises a main current-carrying winding and a main current-limiting winding arranged in parallel; the main current-carrying winding and the main current-limiting winding are respectively connected in series with the auxiliary winding (4); the fast switch (6) is connected in series with the main current-carrying branch and then connected in parallel with the main current-limiting branch; The fault detection module comprises a current detection unit (7), a temperature detection unit and a fault judgment unit.
2. A variable impedance superconducting current limiting transformer short-circuit current suppression device according to claim 1, characterized in that: The winding parameters of the main current-passing winding and the main current-limiting winding are the same.
3. The short-circuit current suppression device of a variable impedance superconducting current limiting transformer according to claim 2, characterized in that: The coils of the main current-limiting winding and the auxiliary winding (4) connected in series therewith are wound in opposite directions, and the coils of the main current-passing winding and the auxiliary winding (4) connected in series therewith are wound in the same direction.
4. The short-circuit current suppression device of a variable impedance superconducting current limiting transformer according to claim 1, characterized in that: The auxiliary winding (4) comprises two anti-parallel wound superconducting windings, the length of the superconducting tapes and the number of parallel windings are the same.
5. The short-circuit current suppression device of a variable impedance superconducting current limiting transformer according to claim 4, characterized in that: The number of parallel strips of the two branches of the auxiliary winding (4) is consistent with that of the low-voltage winding (3), and the strip length is less than the length of a single strip of the low-voltage winding (3), which is determined by the voltage reduction after current limiting and the requirement for increasing the current limiting impedance.
6. The short-circuit current suppression device of a variable impedance superconducting current limiting transformer according to claim 1, characterized in that: The high voltage winding (1), the low voltage winding (2) and the auxiliary winding (4) are all superconducting windings. The high voltage winding (1) and the low voltage winding (2) are connected in a star or triangle manner. The superconducting windings include yttrium barium copper oxide (YBCO) or bismuth strontium calcium copper oxide (BSCCO).
7. A variable impedance superconducting current limiting transformer short-circuit current suppression device according to claim 6, characterized in that: The superconducting winding automatically quenches under short-circuit current and transforms into a resistive state current limiting, and the parallel branch is cut off by a fast switch (6) to double the resistance.
8. An application method of a variable impedance superconducting current limiting transformer short-circuit current suppression device, applicable to the device as claimed in any one of claims 1 to 7, characterized in that: The method of use comprises the following steps: S1, the fault detection and judgment module continuously samples the current and temperature signals of the variable impedance superconducting current limiting transformer; S2, the fault detection and judgment module analyzes the sampled current and temperature data to determine whether the current magnitude and duration are greater than the expected set value; S3, when the sampled instantaneous current value is greater than the set first protection action value and the duration is greater than the set time, or the instantaneous current value is greater than the set second protection action value, or the temperature is greater than the set protection action temperature, enter step S4, otherwise return to S2 to continue sampling; S4, the fast switch (6) is opened, the main current branch of the variable impedance superconducting current limiting transformer is cut off, the auxiliary winding is decoupled, and the superconducting current limiting impedance is doubled; S5. Under the action of the current limiting impedance, the amplitude and time constant of the asymmetric short-circuit current are greatly reduced, and the asymmetric short-circuit current is suppressed. S6. The system circuit breaker (8) on the short-circuit side is disconnected, the short-circuit current after current limiting is cut off, and the fault is cleared.
9. The application method of the variable impedance superconducting current limiting transformer short-circuit current suppression device according to claim 8, characterized in that: The first protection action value of the instantaneous current is an overload protection value, whose value is between the rated current peak value of the superconducting transformer and the total critical current of the superconducting transformer, and the second protection action value is a short-circuit protection value, and the first protection action value is less than the second protection action value.
10. The application method of the variable impedance superconducting current limiting transformer short-circuit current suppression device according to claim 8, characterized in that: The protection action temperature is the maximum value of the working temperature of the superconducting current limiting transformer. A superconducting current limiting transformer exceeding the protection action temperature is considered to have quenched.