Three-section protection cooperation method and system based on rapid identification algorithm

Abstract

The invention discloses a three-section protection cooperation method and system based on a rapid identification algorithm, and the method comprises the steps: setting a rapid-response voltage and current electrical quantity threshold value according to an application scene, and building a superior and subordinate protection system; an upper-level protection system and a lower-level protection system are connected through an optical cable, so that a device controller arranged in the system monitors current, voltage and electrical quantity of a circuit system in real time; sending a locking signal to a superior controller corresponding to the system according to the judgment conditions of the optical fiber locking device and the subordinate controller; and the upper-level controller reads the locking signal of the corresponding locking concentrator so as to lock the local device in a delayed manner. Rapid protection cooperation is realized through optical fibers by using different positions and different effects of the device in upper and lower circuits, thereby ensuring rapid fault removal when a system has a fault, and realizing continuous power supply of a power grid. According to the scheme, the phenomenon of large-area load shedding caused by simultaneous action of multiple stages of rapid devices when a short-circuit fault occurs can be avoided, and the selective function of accurately isolating a short-circuit fault point at a head wave is achieved.

Description

Technical Field

[0001] The present invention relates to the field of upper and lower level protection coordination relay protection of multi-level circuit breakers in a 3.6-40.5 kV medium voltage system, and in particular to a three-stage protection coordination method and system based on a fast identification algorithm. Background Art

[0002] At present, for the 3.6-40.5kV medium voltage system, the time step difference of the comprehensive protection device and the amplitude and direction of the current and voltage are used as the basis for the three-stage protection setting. When formulating the coordination of the upper and lower protections in the system, it is often the result of a compromise between selectivity, speed, sensitivity and reliability. For occasions using end switches, busbar residual voltage holding devices and zero-loss deep current limiting devices, the selectivity and speed of relay protection can be achieved within an extremely short time step through a three-stage protection coordination method based on rapid identification. Summary of the invention

[0003] The present invention proposes a three-stage protection coordination method based on rapid identification, which can at least solve one of the technical problems in the background technology.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A three-stage protection coordination method based on a fast identification algorithm, characterized in that it includes the following steps:

[0006] S100, set voltage and current electrical quantity thresholds according to application scenarios, and build upper and lower level protection systems;

[0007] S200, use optical cables to connect the upper and lower protection systems, so that the device controller built into the system can monitor the current, voltage and electrical quantity of the circuit system in real time;

[0008] S300, the optical fiber interlocker in the device controller and the lower controller use a fast voltage identification algorithm and a fast current identification algorithm to identify the fault, read the location of the fault through the optical fiber interlocker, and send a blocking signal to the upper controller corresponding to the system;

[0009] S400, the upper controller reads the locking signal of the corresponding locking concentrator to delay locking of the local device to achieve three-stage protection.

[0010] Furthermore, the fast voltage algorithm method in step S300 of the present invention is as follows:

[0011] S311, collect electrical signal U in real time through the voltage transformer of the device, assuming that the sampling frequency is f Z , the power frequency is ω, then the sampling time interval ΔT=1 / f z , U 1 , U2 is the continuously sampled voltage signal;

[0012]

[0013]

[0014] Among them, A m represents the amplitude of the three-phase voltage, ω is the power frequency, t represents the sampling time, is the initial phase angle of zero-sequence voltage;

[0015] S312, Algebraic Theorem Introduces A m

[0016]

[0017] Since the sampling frequency is very high and the sampling time interval is very small, sin(ω×ΔT) is a positive value, and formula (3) can be written as:

[0018]

[0019] S313, calculating the voltage amplitude.

[0020] Furthermore, the fast current algorithm method in step S300 of the present invention is as follows:

[0021] In the fast judgment, 2ms sampling is used, the sampling frequency is 6.4kHz, and the influence of the short-circuit time constant on the short-circuit process is not considered;

[0022] The transient expression of current I is:

[0023]

[0024] Perform the first-order Taylor expansion of (5)

[0025]

[0026] Assume that during the detection process, a group of instantaneous current values ​​detected are i1, i2, i3, i4…ik. Then according to formula (5), we have

[0027] in According to the least squares method, we can obtain β 1 and β 2 :

[0028]

[0029] By using formula (8) to obtain β 1 and β 2 After that, the current amplitude I and phase θ can be obtained from β1 and β 2 Expressed as:

[0030]

[0031] Furthermore, in step S300 of the present invention, the optical fiber locking device reads the fault occurrence position, including:

[0032] When the optical fiber locker reads that the fault occurs at the final stage, the final stage controller directly sends a trip signal to the end switch, and the controller at this stage sends a delay instruction to the feeder bus residual pressure holding device, and directly locks the device at this stage after a specified delay.

[0033] Furthermore, the final-stage controller of the present invention sends a locking signal to the locking concentrator of the same stage, and the controller of the same stage reads the locking signal of the locking concentrator of the same stage, delays 2ms, and directly locks the device of the same stage.

[0034] Furthermore, in step S300 of the present invention, the optical fiber locking device reads the fault location situation and further includes:

[0035] When the fiber optic interlock reads that a fault has occurred at this level, the controller at this level also identifies the location of the fault based on the current and voltage electrical quantities, and sends a locking signal to the upper-level interlocking concentrator. The upper-level controller also reads the locking signal of the lower-level interlocking concentrator, delays 2ms, and directly locks the upper-level device.

[0036] In yet another aspect, a three-stage protection coordination system based on a rapid identification algorithm includes: a control device, an eddy current driven circuit breaker, and a fiber optic locking concentrator;

[0037] The control device is provided with a fast identification algorithm;

[0038] The plurality of eddy current driven circuit breakers are used to quickly cut off faults;

[0039] The optical fiber locking concentrator is connected to a control device;

[0040] The control equipment is connected to the eddy current driven circuit breaker, and the control equipment is connected to the optical fiber locking concentrator;

[0041] Several eddy current driven circuit breakers are divided into four groups and connected in parallel on four sections of system buses. The four sections of the bus are 10KV section one of the main step-down station, 10KV section two of the main step-down station, 10KV section one of the switch station, and 10KV section two of the switch station. Among them, the 10KV section one of the main step-down station and the 10KV section two of the main step-down station, the 10KV section one of the switch station and the 10KV section two of the switch station are connected through circuit breakers respectively.

[0042] Furthermore, the eddy current driven circuit breaker for performing fault clearing of the present invention comprises a terminal switch device for clearing the fault, a busbar residual voltage holding device, and a zero-loss deep current limiting device.

[0043] Furthermore, the circuit breaker of the present invention adopts a capacitor energy storage method, receives the opening and closing instructions of the device body controller, releases the energy of the energy storage capacitor through the opening and closing coil, and realizes rapid opening and closing of the circuit breaker.

[0044] Furthermore, in the three-stage protection coordination described in the present invention, when the short-circuit current of the system circuit exceeds the standard, a zero-loss deep current limiting device is used to limit the current first, and then the upper and lower level protection coordination is achieved through the time step difference; when the short-circuit current of the system circuit does not exceed the standard, the upper and lower level protection coordination is achieved through the time step difference.

[0045] It can be seen from the above technical solutions that the three-stage protection coordination method, system and device based on rapid identification of the present invention have the following advantages compared with the traditional protection system:

[0046] 1. The solution of the present invention cooperates with the upper and lower level protections. If the short-circuit current exceeds the standard, the current is limited first to ensure the safe disconnection of the circuit breaker in the system.

[0047] 2. The solution of the present invention locates the fault within a 2ms time step difference through the coordination of upper and lower level protections, and eliminates the fault within 20ms to avoid the expansion of the accident.

[0048] 3. The solution of the present invention can avoid the phenomenon of large-scale load shedding caused by simultaneous operation of multiple fast devices when a short-circuit fault occurs. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the process flow of the three-stage protection coordination method of the present invention;

[0050] Figure 2 This is a circuit schematic diagram of the first-level unlimited current three-stage protection coordination system of the present invention;

[0051] Figure 3 This is a circuit diagram of the first-level current-limiting three-stage protection coordination system of the present invention. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0053] like Figure 1 As shown, the three-stage protection coordination method based on rapid identification described in this embodiment has the following specific steps:

[0054] S100, set voltage and current electrical quantity thresholds according to application scenarios, and build upper and lower level protection systems;

[0055] S200, use optical cables to connect the upper and lower protection systems, so that the device controller built into the system can monitor the current, voltage and electrical quantity of the circuit system in real time;

[0056] S300, the optical fiber interlocker in the device controller and the lower controller use a fast voltage identification algorithm and a fast current identification algorithm to identify the fault, read the location of the fault through the optical fiber interlocker, and send a blocking signal to the upper controller corresponding to the system;

[0057] S400, the upper controller reads the locking signal of the corresponding locking concentrator to delay locking of the local device to achieve three-stage protection.

[0058] The following is a detailed description of each step:

[0059] S100, set voltage and current electrical quantity thresholds according to application scenarios, and build upper and lower level protection systems;

[0060] The upper and lower protection systems are specifically three-stage protection coordination systems including control equipment, several eddy current driven circuit breakers, and optical fiber locking concentrators;

[0061] The control device is provided with a fast identification algorithm;

[0062] The eddy current driven circuit breaker is used to quickly cut off the fault;

[0063] The optical fiber locking concentrator is connected to a control device;

[0064] The control equipment is connected to the eddy current driven circuit breaker, and the control equipment is connected to the optical fiber locking concentrator;

[0065] Several eddy current driven circuit breakers that quickly execute fault clearing are divided into four groups and connected in parallel on four sections of system buses. The four sections of the bus are 10KV section one of the main step-down station, 10KV section two of the main step-down station, 10KV section one of the switch station, and 10KV section two of the switch station. Among them, the 10KV section one and the 10KV section two of the main step-down station, the 10KV section one of the switch station and the 10KV section two of the switch station are connected through circuit breakers respectively.

[0066] A control device connected to a rapid identification algorithm is connected to an eddy-current driven circuit breaker that rapidly executes fault removal, and the control device is connected to an optical fiber locking concentrator; wherein, the eddy-current driven circuit breaker that rapidly executes fault removal comprises an end switch device that rapidly removes the fault, a bus residual voltage holding device, and a zero-loss depth current limiting device; and the circuit breaker adopts a capacitor energy storage method, receives the opening and closing instructions of the device body controller, releases the energy of the energy storage capacitor through the opening and closing coil, and realizes rapid opening and closing of the circuit breaker.

[0067] S200, optical cables connect the upper and lower protection systems, so that the device controller built into the system can monitor the current, voltage and electrical quantity of the circuit system in real time;

[0068] S300, the optical fiber interlocker in the device controller and the lower controller use a fast voltage identification algorithm and a fast current identification algorithm to identify the fault, read the location of the fault through the optical fiber interlocker, and send a blocking signal to the upper controller corresponding to the system;

[0069] The optical cable and interlock concentrator are connected to the upper and lower device controllers. The upper and lower device controllers use fast algorithms to identify the location of the fault based on the current and voltage electrical quantities and read the location where the work occurs through the optical fiber interlock;

[0070] The principle of the fast voltage identification algorithm is as follows:

[0071] S311, collect electrical signal U in real time through the voltage transformer of the device, assuming that the sampling frequency is f Z , the power frequency is ω, then the sampling time interval ΔT=1 / f z , U 1 , U 2 is the continuously sampled voltage signal;

[0072]

[0073] Among them, A m represents the amplitude of the three-phase voltage, ω is the power frequency, t represents the sampling time, is the initial phase angle of the zero-sequence voltage.

[0074] S312, according to the algebraic theorem, deduce A m

[0075]

[0076] Since the sampling frequency is very high and the sampling time interval is very small, sin(ω×ΔT) is a positive value, so formula (3) can be written as:

[0077]

[0078] S313, calculating the voltage amplitude.

[0079] The principle of the fast current algorithm is as follows:

[0080] In the fast judgment, 2ms sampling is used, the sampling frequency is 6.4kHz, and the influence of the short-circuit time constant on the short-circuit process is not considered. Take the A phase current as an example;

[0081] The transient expression of current I is:

[0082]

[0083] Perform the first-order Taylor expansion of (5)

[0084]

[0085] Assume that during the detection process, a group of instantaneous current values ​​detected are i1, i2, i3, i4…ik. Then according to formula (5), we have

[0086] in According to the least squares method, we can obtain β 1 and β 2 :

[0087]

[0088] By using formula (8) to obtain β 1 and β 2 After that, the current amplitude I and phase θ can be obtained from β 1 and β 2 Expressed as:

[0089]

[0090] If the fault occurs at the last stage, the last stage controller directly sends a tripping signal to the terminal switch and sends a locking signal to the locking concentrator at this stage. The controller at this stage reads the locking signal of the locking concentrator at this stage, delays 2ms and directly locks the device at this stage. If the fault occurs at this stage, the controller at this stage also identifies the location of the fault based on the current and voltage electrical quantities, and sends a locking signal to the upper-level locking concentrator. The upper-level controller also reads the locking signal of the lower-level locking concentrator, delays 2ms and directly locks the upper-level device.

[0091] S400, the upper controller reads the locking signal of the corresponding locking concentrator to delay locking of the local device to achieve three-stage protection.

[0092] The delayed locking device is a direct locking device with a delay of 2MS, which is performed by the controller reading the locking signal of the locking device.

[0093] The following is a detailed description of different system failure scenarios using embodiments:

[0094] Embodiment 1: Figure 2As shown, a short-circuit fault occurs at the third level of the system (fault at point K3): when the fast opening of the switchgear identifies the short-circuit fault current, it immediately operates and sends an optical fiber locking signal to the feeder bus residual voltage holding device of the (general step-down station); when the feeder bus residual voltage holding device of the (general step-down station) identifies the short-circuit fault current, it delays 2ms to monitor the optical fiber locking signal, and after receiving the locking signal, it is determined that a fault occurs at the lower level, and the locking protection does not operate;

[0095] A short-circuit fault occurs at the secondary level of the system (fault at point K2): the quick-opening part of the (switch station) does not operate without fault current and does not output a locking signal. When the feeder bus residual voltage holding device of the (main drop station) identifies the short-circuit fault current, it delays 2ms to monitor the optical fiber locking signal. If it does not receive the locking signal from the quick-opening part of the (switch station), it is determined that a fault has occurred at this level and the protection is immediately activated.

[0096] Embodiment 2: A short-circuit fault occurs at the third level of the system (fault at point K3, and the short-circuit current does not exceed the standard): when the quick opening of the (switch station) identifies the short-circuit fault current, it immediately acts and sends a fiber optic locking signal to the bus residual voltage holding device of the (general drop station) feeder; when the (general drop station) feeder bus residual voltage holding device identifies the short-circuit fault current, it immediately sends a fiber optic locking signal to the primary current limiting device, and delays 2ms to monitor the fiber optic locking signal, receives the quick opening locking signal of the (switch station), determines that a fault occurs at the lower level, and the protection locking does not act; when the current limiting device identifies the short-circuit fault current, it delays 2ms to monitor the fiber optic locking signal, receives the locking signal of the bus residual voltage holding device of the (general drop station) feeder, determines that a fault occurs at the lower level, and the locking protection does not act;

[0097] A short-circuit fault occurs at the secondary level of the system (fault at point K2, and the short-circuit current does not exceed the standard): the quick-opening position of the (switch station) does not operate or output a locking signal if there is no fault current. The bus residual voltage holding device of the (main step-down station) identifies the short-circuit fault current and the short-circuit current does not exceed the standard, and immediately sends a fiber optic locking signal to the primary current limiting device, and delays 2ms to monitor the fiber optic locking signal. If no quick-open locking signal from the switch station is received, it is determined that a fault has occurred at this level, and the protection is activated; when the current limiting device identifies the short-circuit fault current and the short-circuit current does not exceed the standard, it delays 2ms to monitor the fiber optic locking signal, and receives the locking signal of the bus residual voltage holding device of the (main step-down station), and determines that a fault has occurred at the lower level, and the locking protection does not operate;

[0098] like Figure 3 As shown, a short-circuit fault occurs in the secondary system (fault at point K2 and the short-circuit current exceeds the standard): the quick-opening part of the (switch station) does not operate without fault current and does not output a locking signal. When the bus residual voltage holding device of the (main step-down station) identifies the short-circuit fault current, it does not send a locking signal because the short-circuit current exceeds the standard, and the locking protection does not operate. The current limiting device identifies the short-circuit fault current and the short-circuit current exceeds the standard, and immediately performs a protective action to perform the predetermined current limiting, and then the bus residual voltage holding device of the (main step-down station) performs a protective action.

[0099] A short-circuit fault occurs at the first level of the system (fault at point K1 and the short-circuit current exceeds the standard): there is no fault current at the quick opening device of the switchgear station or the feeder bus residual voltage holding device of the main drop station, and the device does not operate or output a locking signal; the current limiting device identifies the short-circuit fault current and the short-circuit current exceeds the standard, and immediately operates the protection to limit the current, providing conditions for the safe opening and closing of the lower-level circuit breaker.

[0100] In summary, the present invention is based on a three-stage protection coordination system and method for rapid identification. It mainly coordinates the upper and lower level protections. If there is a short-circuit current exceeding the standard, the current is limited first to ensure the safe disconnection of the circuit breaker in the system, locate the location of the fault within a time step difference of 2ms, and remove the fault within 20ms to avoid the expansion of the accident. The scheme of the present invention can avoid the simultaneous operation of multiple-stage rapid devices when a short-circuit fault occurs, thereby causing a large-scale load shedding phenomenon.

[0101] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0102] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0103] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A three-stage protection coordination method based on a fast identification algorithm, characterized in that , including the following steps: S100, set voltage and current electrical quantity thresholds according to application scenarios, and build upper and lower level protection systems; S200, use optical cables to connect the upper and lower protection systems, so that the device controller built into the system can monitor the current, voltage and electrical quantity of the circuit system in real time; S300, the optical fiber interlocker in the device controller and the lower controller use a fast voltage identification algorithm and a fast current identification algorithm to identify the fault, read the location of the fault through the optical fiber interlocker, and send a blocking signal to the upper controller corresponding to the system; S400, the upper controller reads the locking signal of the corresponding locking concentrator to delay locking of the local device to achieve three-stage protection.

2. The three-stage protection coordination method based on the rapid identification algorithm according to claim 1 is characterized in that: The algorithm method for quickly identifying voltage in step S300 is as follows: S311, collect electrical signal U in real time through the voltage transformer of the device, assuming that the sampling frequency is f Z , the power frequency is ω, then the sampling time interval ΔT=1 / f z , U1 and U2 are continuously sampled voltage signals; Among them, A m represents the amplitude of the three-phase voltage, ω is the power frequency, t represents the sampling time, is the initial phase angle of zero-sequence voltage; S312, Algebraic Theorem Introduces A m Since the sampling frequency is very high and the sampling time interval is very small, sin(ω×ΔT) is a positive value, and formula (3) is written as: S313, calculating the voltage amplitude.

3. The three-stage protection coordination method based on the rapid identification algorithm according to claim 1 is characterized in that: The algorithm method for quickly identifying the current in step S300 is as follows: In the fast judgment, 2ms sampling is used, the sampling frequency is 6.4kHz, and the influence of the short-circuit time constant on the short-circuit process is not considered; The transient expression of current I is: Perform the first-order Taylor expansion of (5) Assume that during the detection process, a group of instantaneous current values ​​detected are i1, i2, i3, i4…ik. Then according to formula (5), we have in Then, according to the least squares method, β1 and β2 are obtained: After β1 and β2 are obtained from equation (8), the current amplitude I and phase θ are expressed by β1 and β2 as follows:

4. The three-stage protection coordination method based on the rapid identification algorithm according to claim 1 is characterized in that: In step S300, the optical fiber locking device is used to read the location where the fault occurs, and a locking signal is sent to the upper controller corresponding to the system, including: When the optical fiber locker reads that the fault occurs at the final stage, the final stage controller directly sends a trip signal to the end switch, and the controller at this stage sends a delay instruction to the feeder bus residual pressure holding device, and directly locks the device at this stage after a specified delay.

5. The three-stage protection coordination method based on the rapid identification algorithm according to claim 4 is characterized in that: The final controller sends a locking signal to the locking concentrator of this stage, and the controller of this stage reads the locking signal of the locking concentrator of this stage, delays 2ms and directly locks the device of this stage.

6. The three-stage protection coordination method based on the rapid identification algorithm according to claim 4 is characterized in that: The step S300 of reading the location of the fault by the optical fiber locker and sending a lock signal to the upper controller corresponding to the system also includes: When the fiber optic interlock reads that a fault has occurred at this level, the controller at this level also identifies the location of the fault based on the current and voltage electrical quantities, and sends a locking signal to the upper-level interlocking concentrator. The upper-level controller also reads the locking signal of the lower-level interlocking concentrator, delays 2ms, and directly locks the upper-level device.

7. The three-stage protection coordination method based on the rapid identification algorithm according to claim 1 is characterized in that: When the short-circuit current of the system circuit exceeds the standard, the zero-loss deep current limiting device will limit the current first, and then the upper and lower protection systems will coordinate through the time step difference; when the short-circuit current of the system circuit does not exceed the standard, the upper and lower protection systems will coordinate through the time step difference.

8. A three-stage protection coordination system based on a rapid identification algorithm, used to implement any one of the three-stage protection coordination methods based on a rapid identification algorithm of claims 1 to 6, characterized in that: include: control equipment, several eddy current driven circuit breakers, and fiber optic blocking concentrators; The control device is provided with a fast identification algorithm; The eddy current driven circuit breaker is used to quickly cut off the fault; The optical fiber locking concentrator is connected to a control device; The control equipment is connected to the eddy current driven circuit breaker, and the control equipment is connected to the optical fiber locking concentrator; Several eddy current driven circuit breakers are divided into four groups and connected in parallel on four sections of system buses. The four sections of the bus are 10KV section one of the main step-down station, 10KV section two of the main step-down station, 10KV section one of the switch station, and 10KV section two of the switch station. Among them, the 10KV section one of the main step-down station and the 10KV section two of the main step-down station, the 10KV section one of the switch station and the 10KV section two of the switch station are connected through circuit breakers respectively.

9. The three-stage protection coordination system based on the rapid identification algorithm according to claim 8 is characterized in that: The eddy current driven circuit breaker comprises a terminal switch device for cutting off the fault, a busbar residual voltage holding device, and a zero-loss deep current limiting device.

10. The three-stage protection coordination system based on the rapid identification algorithm according to claim 8 is characterized in that: The eddy current driven circuit breaker adopts a capacitor energy storage method, receives the opening and closing instructions of the device body controller, releases the energy of the energy storage capacitor through the opening and closing coil, and realizes the rapid opening and closing of the circuit breaker.

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