Universe quick-break protection device and method for power distribution network

Abstract

The invention discloses a global quick-break protection device and method for a power distribution network, and belongs to the technical field of power distribution network short circuit fault handling. The global quick-break protection device comprises an optical transponder and switch assemblies associated with protection switches at all levels, the switch assemblies are connected through optical fibers, the switch assemblies and the optical transponder are connected through optical fibers, and each switch assembly comprises a protection switch and an associated controller. The controller is configured to send out a blocking optical signal once a short-circuit fault is detected and send out a starting optical signal when the switch is opened, the blocking optical signal is uploaded to a superior protection switch through the optical transponder or the cascade optical fiber to block the superior protection switch, and the starting optical signal is downloaded through the optical transponder or the cascade optical fiber; therefore, the power supply switching device carries out power supply switching. According to the invention, when the protection switch closest to the short-circuit fault point is quickly broken, the superior protection switch is locked, and the standby power supply can be selectively switched, so that the adverse effect of the short-circuit fault on the power distribution system is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of short-circuit fault handling of power distribution network, and more particularly to a global instantaneous trip protection device and method for power distribution network. BACKGROUND

[0002] In a power distribution network, when a short-circuit fault occurs at the end, the end-stage protection switch and its upper-stage protection switch will all capture the short-circuit fault current, and if there is no connection between these protection switches, they will all trip, thereby causing large-area power outage. The existing solution is to use a differential time delay, the core goal of which is to ensure that when a fault occurs, the protection device close to the fault point acts first to remove the fault, while avoiding unnecessary action of the upper-stage protection device, thereby reducing the power outage range and improving the power supply reliability and continuity of the power distribution network. Specifically, the end-stage protection switch can be set as an instantaneous trip protection, the time setting of the instantaneous trip protection of the direct upper-stage protection switch of the end-stage protection switch is set to, for example, 100 milliseconds, and the time setting of the instantaneous trip protection of the direct upper-stage protection switch of the upper-stage protection switch is set to, for example, 200 milliseconds. In this case, if a short-circuit fault occurs at the end, the end-stage protection switch will immediately start protection tripping, while the upper-stage protection switch will not trip immediately due to the set delay action, and before the delay time of the upper-stage protection switch ends, the fault line will be isolated by the end-stage protection switch having tripped, thereby avoiding tripping.

[0003] The defect of this solution is that the use of differential time delay protection tripping will cause the power distribution system to continuously experience the impact of short-circuit current during the delay time before the protection switch closest to the short-circuit fault point trips, and the voltage will be very low during this period (the power swing time is long) until the associated protection switch or the upper-stage protection switch trips. Moreover, the closer to the power supply side the fault occurs, the longer the time for the corresponding protection switch to trip, and the longer the system power swing time. When a short-circuit fault occurs near the power supply end, the generated short-circuit current is larger, and if the corresponding protection switch does not timely remove the short-circuit fault, the damage will be greater. SUMMARY

[0004] In view of the fact that the differential time delay protection scheme of the prior art causes the protection switch closer to the power supply side to have a longer tripping delay when a short-circuit fault occurs, thereby causing the power distribution system to have a longer power swing time and short-circuit time, and causing great harm to the power distribution system, the present application proposes a global instantaneous trip protection method, which does not need to set a differential time delay for the protection switch, and even the protection switch close to the power supply side can achieve instantaneous tripping, thereby effectively reducing the adverse effects of the existing differential time delay protection scheme on the power distribution system when a short-circuit fault occurs.

[0005] In one aspect of the present application, a global instantaneous trip protection device for a power distribution network is provided, the power distribution network comprising a power source, a primary distribution station, and a secondary distribution station as a lower level of the primary distribution station, the global instantaneous trip protection device comprising an optical repeater and switch assemblies CB1, CB2, CB3 and CB4, each switch assembly comprising a switch and a controller associated with the switch, wherein switch 1 in switch assembly CB1 is a terminal protection switch of the secondary distribution station, switch 2 in switch assembly CB2 is a line in protection switch of the secondary distribution station, switch 3 in switch assembly CB3 is a preceding protection switch of a line in of the secondary distribution station, and switch 4 in switch assembly CB4 is a line in protection switch of the primary distribution station; the optical repeater comprises a higher level optical repeater and a lower level optical repeater, the higher level optical repeater is connected to switch assemblies CB3 and CB4 through optical fibers respectively, and the lower level optical repeater is connected to switch assemblies CB1 and CB2 through optical fibers respectively; the lower level optical repeater is configured to receive a blocking optical signal from switch assembly CB1 and to forward the blocking optical signal to switch assembly CB2; the higher level optical repeater is configured to receive a blocking optical signal from switch assembly CB3 and to forward the blocking optical signal to switch assembly CB4; switch assembly CB2 and switch assembly CB3 are connected through a cascade optical fiber, wherein switch assembly CB2 is configured to forward the blocking optical signal to switch assembly CB3 through the cascade optical fiber once the blocking optical signal is received; each switch assembly is further configured to send out a blocking optical signal and calculate a tripping time once a short-circuit fault is detected, and if the blocking optical signal is received before the tripping time, the operation of the switch in the switch assembly receiving the blocking optical signal is blocked, and if the blocking optical signal is not received until the tripping time, the switch in the switch assembly not receiving the blocking optical signal is caused to perform a tripping operation at the tripping time.

[0006] In the above first aspect, the lower level optical repeater comprises a first lower level input interface and a first higher level output interface, wherein switch assembly CB1 is connected to the first lower level input interface through an optical fiber, and switch assembly CB2 is connected to the first higher level output interface through an optical fiber; the higher level optical repeater comprises a second lower level input interface and a second higher level output interface, wherein switch assembly CB3 is connected to the second lower level input interface through an optical fiber, and switch assembly CB4 is connected to the second higher level output interface through an optical fiber.

[0007] In the above first aspect, the switch comprises a high-speed split-phase circuit breaker, the tripping time of which is less than 1.5 milliseconds, and the tripping dispersion of which is less than 0.2 milliseconds.

[0008] In the first aspect, the secondary distribution station further comprises a lower-level backup power source controlled by the power switching device; each switch assembly is further configured to send an enabling optical signal when detecting a short-circuit fault and tripping the switch in the switch assembly that does not receive the blocking optical signal; the lower-level optical repeater further comprises a first upper-level input interface and a first lower-level output interface, and the upper-level optical repeater further comprises a second upper-level input interface and a second lower-level output interface, wherein the switch assembly CB2 is connected to the power switching device; the switch assembly CB4 is connected to the second upper-level input interface of the upper-level optical repeater through an optical fiber, and the switch assembly CB3 is connected to the second lower-level output interface of the upper-level optical repeater through an optical fiber; wherein the switch assembly CB3 sends an enabling optical signal to the switch assembly CB2 through a cascaded optical fiber when detecting a short-circuit fault and tripping the switch 3, and the switch assembly CB2 sends an enabling signal to the power switching device after receiving the enabling optical signal, and the power switching device starts power switching to switch to the lower-level backup power source after receiving the enabling signal; wherein the switch assembly CB4 sends an enabling optical signal when detecting a short-circuit fault and tripping the switch 4, and forwards the enabling optical signal to the switch assembly CB3 through the upper-level optical repeater, the switch assembly CB3 forwards the enabling optical signal to the switch assembly CB2 through a cascaded optical fiber, the switch assembly CB2 sends an enabling signal to the power switching device after receiving the enabling optical signal, and the power switching device starts power switching to switch to the lower-level backup power source after receiving the enabling signal.

[0009] Further, the controller comprises an analog unit, a control unit, a signal input unit, a signal output unit and a power supply unit, wherein the analog unit is configured to collect three-phase current and voltage, zero sequence current and voltage; the signal input unit comprises a first electrical interface and a first optical interface, the first electrical interface is used to detect the on-off state of the switch, and the first optical interface is configured with an optical receiving module used to receive a blocking optical signal and a starting optical signal; the signal output unit comprises a second electrical interface and a second optical interface, the second electrical interface is used to output a closing signal used to close the switch, and the second optical interface is configured with an optical transmitting module used to send a starting optical signal, a blocking optical signal and an opening signal; the control unit is configured to detect a short-circuit fault based on the three-phase current and voltage, the zero sequence current and voltage, and once the short-circuit fault is detected, send a blocking optical signal to an optical repeater or a superior controller through the optical transmitting module of the second optical interface, and calculate an opening time; if the blocking optical signal is received through the optical receiving module of the first optical interface before the opening time, the blocking optical signal is forwarded through the optical transmitting module of the second optical interface to block the operation of the switch associated with the controller; if the blocking optical signal is not received until the opening time, an opening signal is sent to the switch associated with the controller through the optical transmitting module of the second optical interface to make the switch perform an opening operation at the opening time, and a starting optical signal is sent to the optical repeater or the subordinate controller through the optical transmitting module; and when the starting optical signal is received through the optical receiving module of the first optical interface, the starting optical signal is forwarded to the subordinate controller or the optical repeater through the optical transmitting module of the second optical interface; and the power supply unit is used to supply power to the analog unit, the control unit, the signal input unit and the signal output unit.

[0010] In the second aspect of the present application, a global instantaneous trip protection method for a power distribution network is provided, which is implemented by the global instantaneous trip protection device of the first aspect of the present application. The global instantaneous trip protection method comprises: if a short-circuit fault occurs at the end of a secondary power distribution station, the switch assembly CB1 sends a blocking optical signal to a lower-level optical transponder upon detecting the short-circuit fault, and calculates a tripping time point to make switch 1 perform a tripping operation at the tripping time point; the lower-level optical transponder receiving the blocking optical signal forwards the blocking optical signal to switch assembly CB2; switch assembly CB2 receiving the blocking optical signal forwards the blocking optical signal to switch assembly CB3 through a cascade optical fiber; switch assembly CB3 receiving the blocking optical signal forwards the blocking optical signal to an upper-level optical transponder; the upper-level optical transponder receiving the blocking optical signal forwards the blocking optical signal to switch assembly CB4; switch assemblies CB2, CB3 and CB4 receiving the blocking optical signal block the operation of their associated switches before the tripping time point; if a short-circuit fault occurs on a bus of the secondary power distribution station, switch assembly CB2 sends a blocking optical signal to switch assembly CB3 through a cascade optical fiber upon detecting the short-circuit fault, and calculates a tripping time point to make switch 2 perform a tripping operation at the tripping time point; switch assembly CB3 receiving the blocking optical signal forwards the blocking optical signal to an upper-level optical transponder; the upper-level optical transponder receiving the blocking optical signal forwards the blocking optical signal to switch assembly CB4; switch assemblies CB3 and CB4 receiving the blocking optical signal block the operation of their associated switches before the tripping time point; if a short-circuit fault occurs on a connecting line between the secondary power distribution station and the primary power distribution station, switch assembly CB3 sends a blocking optical signal to an upper-level optical transponder upon detecting the short-circuit fault, and calculates a tripping time point to make switch 3 perform a tripping operation at the tripping time point; the upper-level optical transponder receiving the blocking optical signal forwards the blocking optical signal to switch assembly CB4; switch assembly CB4 receiving the blocking optical signal blocks the operation of its associated switch before the tripping time point; if a short-circuit fault occurs on a bus of the primary power distribution station, switch assembly CB4 calculates a tripping time point upon detecting the short-circuit fault to make switch 4 trip at the tripping time point.

[0011] In the second aspect described above, if a short-circuit fault occurs on a connecting line between the secondary power distribution station and the primary power distribution station, switch assembly CB3 sends a start optical signal to switch assembly CB2 through a cascade optical fiber upon detecting the short-circuit fault and making switch 3 trip; switch assembly CB2 receiving the start optical signal sends a start signal to a power switching device; the power switching device starts power switching to switch to a lower-level backup power source upon receiving the start signal.

[0012] Further, if a short-circuit fault occurs on the bus of the primary power distribution station, the switch assembly CB4 sends a start-up optical signal to the upper optical repeater through the second upper input interface of the upper optical repeater when detecting the short-circuit fault and tripping the switch 4; the upper optical repeater receiving the start-up optical signal forwards the start-up optical signal to the switch assembly CB3; the switch assembly CB3 receiving the start-up optical signal forwards the start-up optical signal to the switch assembly CB2 through the cascade optical fiber; the switch assembly CB2 receiving the start-up optical signal sends a start-up signal to the power switching device; the power switching device starts power switching to the lower standby power source after receiving the start-up signal.

[0013] In the embodiment of the present application, the time for the switch assembly CB1 to send the blocking optical signal to the lower optical repeater and for the lower optical repeater to forward the blocking optical signal to the upper optical repeater is less than 50 microseconds.

[0014] In the embodiment of the present application, the tripping time is related to the current zero-crossing time, and the time interval from the tripping time to the current zero-crossing time is not less than the tripping time of the switch.

[0015] The present application has the following advantages: The present application connects the controller associated with the protection switch of the power distribution network through the optical fiber and the optical repeater, so that the controller sends a blocking optical signal as soon as it detects a short-circuit fault, and forwards the blocking optical signal to the upper protection switch through the optical repeater or the optical fiber to block the operation of the upper protection switch, and the controller calculates a tripping time related to the current zero-crossing time when detecting the short-circuit fault, and blocks the operation of the associated switch if the blocking optical signal is received before the tripping time, and makes the associated switch perform a tripping operation at the tripping time if the blocking optical signal is not received until the tripping time, so that the upper and lower switches can both trip when a short-circuit fault occurs, and all the upper switches performing the tripping are blocked at the same time, effectively reducing the adverse effects on the power distribution system when a short-circuit fault occurs.

[0016] The present application also makes the controller send a start-up optical signal when detecting a short-circuit fault and tripping the associated protection switch, and forwards the start-up optical signal to the lower controller through the optical repeater or the optical fiber, so as to send a start-up signal to the power switching device through the related controller to start power switching to the lower standby power source, effectively improving the reliability and continuity of power supply of the power distribution station.

[0017] The forwarding of the optical signal of the present application is realized through pure hardware, and the forwarding time is in microseconds, which is much smaller than the time from detecting a short-circuit fault by the controller to sending a tripping signal, so that all the upper protection switches performing the tripping can be timely blocked.

[0018] The switch of the application adopts high-speed phase disconnector, whose breaking time is less than 1.5ms, greatly shortening the fault isolation time, effectively protecting the power equipment and reducing the influence of the fault on the power grid.

[0019] The global instantaneous trip protection device of the application can be applied to two-stage or more power distribution systems, and has good application extension range. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which form a part of the present application, are used to provide further understanding of the application, and make the other features, objectives, and advantages of the present application more apparent. The illustrative embodiments of the drawings and their descriptions serve the purpose of explaining the present application, and are not intended to limit the present application.

[0021] In addition, throughout the drawings, same or similar reference numerals are used to represent same or similar elements. It should be understood that the drawings are schematic, and the elements and elements are not necessarily drawn to scale.

[0022] In the drawings: Figure 1 is a distribution diagram of the global instantaneous trip protection device of the application.

[0023] Figure 2 is a structure block diagram of the lower-level optical transponder and the upper-level optical transponder of the application.

[0024] Figure 3 is a function block diagram of the controller of the application.

[0025] Figure 4 is a control logic flow chart of the controller of the application. DETAILED DESCRIPTION

[0026] Embodiments of the present disclosure will be described in more detail hereinafter with reference to the drawings. Although some embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms, and should not be interpreted as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes, and are not intended to limit the scope of protection of the present disclosure.

[0027] Referring to Figure 1The application provides a global instantaneous trip protection device for a power distribution network, the power distribution network comprising a power supply, a primary power distribution station and a secondary power distribution station as a lower level of the primary power distribution station, the global instantaneous trip protection device comprising an optical transponder and switch assemblies CB1, CB2, CB3 and CB4, each switch assembly comprising a switch and a controller associated with the switch, switches 1, 2, 3 and 4 corresponding to switch assemblies CB1, CB2, CB3 and CB4 respectively, wherein switch 1 is a final protection switch of the secondary power distribution station; switch 2 is a line protection switch of the secondary power distribution station; switch 3 is a front protection switch of a line of the secondary power distribution station; and switch 4 is a line protection switch of the primary power distribution station. It should be noted that switch 1 as a branch protection switch of the secondary power distribution station can be one or more in number; similarly, switch 3 as a branch protection switch of the primary power distribution station can also be one or more in number.

[0028] The optical transponder has an input interface and an output interface, and comprises an upper level optical transponder and a lower level optical transponder, the upper level optical transponder being connected to the switch assembly (for example, CB3, CB4) of the primary power distribution station through an optical fiber, and the lower level optical transponder being connected to the switch assembly (for example, CB1, CB2) of the secondary power distribution station through an optical fiber.

[0029] In an embodiment of the application, in the case of no standby power supply and only considering minimizing the impact of short-circuit faults occurring in the power distribution network on the power distribution network in terms of power swing time and short-circuit current, referring to Figure 2 , the lower level optical transponder comprises a first lower level input interface and a first upper level output interface, wherein the switch assembly CB1 is connected to the first lower level input interface through an optical fiber, and the switch assembly CB2 is connected to the first upper level output interface through an optical fiber, and the lower level optical transponder is configured to receive a blocking optical signal from the lower level protection switch (for example, the switch assembly CB1) through the first lower level input interface, and to forward the blocking optical signal to the directly upper level protection switch (for example, the switch assembly CB2) of the lower level protection switch through the first upper level output interface.

[0030] The upper level optical transponder comprises a second lower level input interface and a second upper level output interface, wherein the switch assembly CB3 is connected to the second lower level input interface through an optical fiber, and the switch assembly CB4 is connected to the second upper level output interface through an optical fiber, and the upper level optical transponder is configured to receive a blocking optical signal from the lower level protection switch (for example, the switch assembly CB3) through the second lower level input interface, and to forward the blocking optical signal to the directly upper level protection switch (for example, the switch assembly CB4) of the lower level protection switch through the second upper level output interface.

[0031] The switch assembly CB2 and the switch assembly CB3 are connected through the cascade optical fiber 7, wherein the switch assembly CB2 retransmits the blocking optical signal to the switch assembly CB3 through the cascade optical fiber 7 once receiving the blocking optical signal, and the switch assembly CB3 retransmits the blocking optical signal to the switch assembly CB4 through the upper optical retransmitter once receiving the blocking optical signal.

[0032] In the power distribution network, the controllers of the switch assemblies CB1, CB2 and CB3 are configured to issue the blocking optical signal once detecting the short-circuit fault, and calculate the tripping time related to the current zero-crossing time, block the operation of the associated switch if the blocking optical signal is received before the tripping time, and make the associated switch perform the tripping operation at the tripping time if the blocking optical signal is not received until the tripping time. It should be noted that the current zero-crossing time should be calculated before the tripping time, and the technology for calculating the current zero-crossing time is the prior art, which is not the innovative technology of the present application, and thus is not described herein. Regarding the tripping of the switch, on the one hand, the switch is preferably tripped at the current zero-crossing time, because the stability of the arc at this time is poor, and the tripping at this time can effectively reduce the damage of the arc to the switch device, improve the service life of the switch, and make the controller calculate the current zero-crossing time first, which can ensure that the switch operates at the optimal tripping time before the natural current zero-crossing, so as to reserve sufficient time for the contact separation of the switch to a safe open distance, ensure that the arc is reliably extinguished at the current zero-crossing, and ensure that the arc gap medium strength quickly recovers at the current zero-crossing, preventing the arc from reigniting. On the other hand, if the switch receives the blocking signal before the tripping time, it means that other switches have already taken on the task of fault removal, and the switch itself does not need to act, avoiding overstep tripping, and if the switch does not receive the blocking signal, it confirms that it is the "switch closest to the fault point" and needs to perform tripping to quickly isolate the fault.

[0033] It should be noted that, since the retransmission of the light in the optical retransmitter and the controller of the present application is completed by pure hardware, the time for sending the blocking optical signal from the last-stage protection switch to the lower-stage optical retransmitter to the lower-stage optical retransmitter retransmitting the blocking optical signal to the upper-stage optical retransmitter is less than 50 microseconds, so that the controllers of the protection switches at all levels can block the operation of all upper-stage protection switches of the protection switch closest to the short-circuit fault point during the period from detecting the short-circuit fault to the tripping time, and make the protection switch trip at the tripping time. In addition, preferably, the switches 1, 2, 3 and 4 of the present application adopt high-speed split-phase circuit breakers, which have controllable independent tripping capability of each phase, and the tripping time is less than 1.5 milliseconds, greatly shortening the fault clearing time, effectively protecting the power equipment, and reducing the impact of the fault on the power grid.

[0034] In one embodiment of the present application, the time interval from the switching-off moment to the current zero-crossing moment is not less than the switching-off time of the switch, for example, 2 milliseconds, so as to reserve sufficient time for the contacts of the switch to separate to a safe distance, to ensure that the arc is reliably extinguished at the current zero-crossing moment, and to ensure that the arc gap medium strength quickly recovers at the current zero-crossing moment, preventing the arc from reigniting.

[0035] In one embodiment of the present application, in order to improve the reliability and continuity of power supply for key equipment and systems, and for occasions such as chemical industry, steel, chip manufacturing, etc. that have extremely high requirements for power reliability and continuity, the present application also considers the scheme of backup power supply. Specifically, the secondary distribution station further comprises a lower backup power supply associated with the power switching switch assembly CB5 controlled by the power switching device.

[0036] In this case, the controller in the aforementioned embodiment is further configured to send a start optical signal when detecting a short-circuit fault and causing the associated switch to open. The lower optical repeater in the aforementioned embodiment further comprises a first upper input interface and a first lower output interface, and the upper optical repeater in the aforementioned embodiment further comprises a second upper input interface and a second lower output interface, wherein the switch assembly CB2 is connected to the power switching device; the switch assembly CB4 is connected to the second upper input interface of the upper optical repeater through an optical fiber, and the switch assembly CB3 is connected to the second lower output interface of the upper optical repeater through an optical fiber.

[0037] The switch assembly CB3 sends a start optical signal when detecting a short-circuit fault and causing the switch 3 to open, and sends the start optical signal to the switch assembly CB2 through the cascaded optical fiber 7, and the switch assembly CB2 sends a start signal to the power switching device after receiving the start optical signal, and the power switching device starts power switching to switch to the lower backup power supply after receiving the start signal. It is worth noting that since the switch assembly CB2 is connected to the power switching device, and the existing power switching device does not have an optical interface for starting switching, the controller of the switch assembly CB2 can be configured to have an optical-electric conversion function for converting the received start optical signal into a start signal that can be received by the existing power switching device.

[0038] The switch assembly CB4 sends a start optical signal when detecting a short-circuit fault and causing the switch 4 to open, and sends the start optical signal to the upper optical repeater through the second upper input interface of the upper optical repeater, and the upper optical repeater forwards the start optical signal to the switch assembly CB3 through the second lower output interface, and the switch assembly CB3 forwards the start optical signal to the switch assembly CB2 through the cascaded optical fiber 7, and the switch assembly CB2 sends a start signal to the power switching device after receiving the start optical signal, and the power switching device starts power switching to switch to the lower backup power supply after receiving the start signal.

[0039] In one embodiment of the present application, referring to Figure 3 The controller mentioned herein comprises an analog unit, a control unit, a signal input unit, a signal output unit and a power supply unit, wherein the analog unit is configured to collect three-phase current and voltage, zero sequence current and voltage; the signal input unit comprises a first electrical interface and a first optical interface, the first electrical interface is used to detect the on-off state of a switch, and the first optical interface is configured with an optical receiving module for receiving a blocking optical signal and a starting optical signal; the signal output unit comprises a second electrical interface and a second optical interface, the second electrical interface is used to output a closing signal for closing the switch, and the second optical interface is configured with an optical transmitting module for sending a starting optical signal, a blocking optical signal and an opening signal for opening the switch.

[0040] Referring to Figure 4 , the control unit is configured to calculate the transient fault power direction based on the three-phase current and voltage, zero sequence current and voltage collected by the analog unit to detect a short-circuit fault, and send a blocking optical signal to an optical repeater or a superior controller through the optical transmitting module of the second optical interface once the short-circuit fault is detected. It should be noted that the technology of calculating the transient fault power direction based on the three-phase current and voltage, zero sequence current and voltage to detect the short-circuit fault is also prior art, which is not the innovative technology of the present application, and therefore is not described herein.

[0041] The control unit calculates the opening time while sending the blocking optical signal: if a blocking optical signal is received through the optical receiving module of the first optical interface before the opening time, the blocking optical signal is forwarded through the optical transmitting module of the second optical interface to block the operation of the switch associated with the controller; if no blocking optical signal is received until the opening time, an opening signal is sent to the switch associated with the controller through the optical transmitting module of the second optical interface to make the switch perform an opening operation at the opening time, and a starting optical signal is sent to the optical repeater or the subordinate controller through the optical transmitting module.

[0042] When the starting optical signal is received through the optical receiving module of the first optical interface, the starting optical signal is forwarded to the subordinate controller or the optical repeater through the optical transmitting module of the second optical interface.

[0043] The power supply unit of the controller is used to supply power to the analog unit, the control unit, the signal input unit and the signal output unit, and provide power support for the normal operation of the controller, and the power supply unit is used to convert the externally input high voltage (AC / DC 220V) into suitable low voltage (5V, 12V, -12V or 24V).

[0044] The application also provides a global instantaneous trip protection method for a power distribution network, which is implemented by the global instantaneous trip protection device. Figure 1 In the case of no backup power supply and only the impact of short-circuit fault on the power distribution network on the minimum power swing time and short-circuit current, the specific operation of the global instantaneous trip protection method is as follows.

[0045] If the short-circuit fault occurs at the end of the secondary power distribution station, for example, at d1, the switch assembly CB1 sends a blocking optical signal to the lower-level optical transponder upon detecting the short-circuit fault, and calculates the tripping time to make switch 1 perform the tripping operation at the tripping time, the lower-level optical transponder receiving the blocking optical signal forwards the blocking optical signal to the switch assembly CB2, the switch assembly CB2 receiving the blocking optical signal forwards the blocking optical signal to the switch assembly CB3 through the cascade optical fiber 7, the switch assembly CB3 receiving the blocking optical signal forwards the blocking optical signal to the upper-level optical transponder, and the upper-level optical transponder receiving the blocking optical signal forwards the blocking optical signal to the switch assembly CB4. The switch assemblies CB2, CB3 and CB4 receiving the blocking optical signal can block the operation of their associated switches before the tripping time.

[0046] Under the prior art conditions, the controller can detect the short-circuit fault within 2.5 milliseconds, and then start calculating the current zero-crossing time of each phase current. From the judgment of the short-circuit fault to the current zero-crossing time, it will exceed 5 milliseconds. The blocking optical signal of the application is sent from the end-stage protection switch to the uppermost protection switch only needs about 50 microseconds. The tripping time of the high-speed split-phase circuit breaker of the application is less than 1.5 milliseconds, and the tripping dispersion is less than 0.2 milliseconds. Therefore, it can be ensured that the protection switch closest to the short-circuit fault point is tripped, and the upper protection switch is blocked before the tripping time.

[0047] It should be noted that the switch assemblies CB2, CB3 and CB4 can also detect the short-circuit fault when it occurs at the end of the secondary power distribution station. The switch assemblies CB2 and CB3 also send a blocking optical signal to their upper protection switch upon detecting the short-circuit fault. The switch assembly CB4 is the uppermost protection switch, and its controller can be set not to send a blocking optical signal. In this example, the switch assemblies CB2 and CB3 forward the blocking optical signal sent by their lower switch assembly if they have not sent a blocking optical signal upon receiving the blocking optical signal sent by their lower switch assembly; and send a blocking optical signal to their upper protection switch if they do not receive the blocking optical signal sent by their lower switch assembly.

[0048] If the short-circuit fault occurs on the bus of the secondary power distribution station, for example, at d2, the switch assembly CB2 sends a blocking optical signal to the switch assembly CB3 through the cascaded optical fiber 7 upon detecting the short-circuit fault, and calculates the tripping time to make the switch 2 perform the tripping operation at the tripping time; the switch assembly CB3 receiving the blocking optical signal forwards the blocking optical signal to the upper optical transponder; the upper optical transponder receiving the blocking optical signal forwards the blocking optical signal to the switch assembly CB4; and the switch assemblies CB3 and CB4 receiving the blocking optical signal block the operation of the switches associated therewith before the tripping time.

[0049] As in the case where the short-circuit fault occurs at d1, the switch assemblies CB3 and CB4 can also detect the short-circuit fault when the short-circuit fault occurs on the bus of the secondary power distribution station, so in this example, the switch assembly CB3 also sends a blocking optical signal upon detecting the short-circuit fault, and forwards the blocking optical signal sent by the lower switch assembly if the switch assembly CB3 has not sent the blocking optical signal upon receiving the blocking optical signal sent by the lower switch assembly; and sends the blocking optical signal to the upper protection switch if the blocking optical signal sent by the lower switch assembly is not received.

[0050] If the short-circuit fault occurs on the connecting line between the secondary power distribution station and the primary power distribution station, for example, at d3, the switch assembly CB3 sends a blocking optical signal to the upper optical transponder upon detecting the short-circuit fault, and calculates the tripping time to make the switch 3 perform the tripping operation at the tripping time; the upper optical transponder receiving the blocking optical signal forwards the blocking optical signal to the switch assembly CB4; and the switch assembly CB4 receiving the blocking optical signal blocks the operation of the switch associated therewith before the tripping time.

[0051] If the short-circuit fault occurs on the bus of the primary power distribution station, for example, at d4, the switch assembly CB4 calculates the tripping time to make the switch 4 perform the tripping operation at the tripping time upon detecting the short-circuit fault.

[0052] In an embodiment of the application, further, if the short-circuit fault occurs on the connecting line between the secondary power distribution station and the primary power distribution station, the switch assembly CB3 sends a starting optical signal to the switch assembly CB2 through the cascaded optical fiber 7 upon detecting the short-circuit fault and making the switch 3 trip; the switch assembly CB2 receiving the starting optical signal sends a starting signal to the power switching device; and the power switching device starts the power switching to switch to the lower standby power source upon receiving the starting signal, in consideration of the standby power source.

[0053] In one embodiment of the present application, in the case of considering the backup power supply, further, if a short-circuit fault occurs on the bus of the primary power distribution station, the switch assembly CB4 sends a start-up optical signal to the upper optical repeater through the second upper input interface of the upper optical repeater when detecting the short-circuit fault and tripping the switch 4; the upper optical repeater receiving the start-up optical signal transmits the start-up optical signal to the switch assembly CB3; the switch assembly CB3 receiving the start-up optical signal transmits the start-up optical signal to the switch assembly CB2 through the cascade optical fiber 7; the switch assembly CB2 receiving the start-up optical signal sends a start-up signal to the power supply switching device; the power supply switching device starts the power supply switching to switch to the lower backup power supply after receiving the start-up signal.

[0054] It should be noted that although the present application is described only for two-level power distribution stations, in fact, three-level or more level power distribution stations can also use the global instantaneous tripping scheme of the present application, the connection mode of the protective switches and optical repeaters of each level is the same, and the operation method is also the same, so the present application is not limited to the specific embodiments described in this application, but can be extended to any multi-level power distribution system which can be applied to the global instantaneous tripping scheme of the present application.

Claims

1. A global instantaneous protection device for a power distribution network including a power source, a primary distribution station, and a secondary distribution station as a subordinate of the primary distribution station, characterized by, The global instantaneous trip protection device comprises optical transponders and switch assemblies CB1, CB2, CB3 and CB4, each of which comprises a switch and a controller associated with the switch, wherein switch 1 in switch assembly CB1 is the last stage protection switch of the secondary distribution station, switch 2 in switch assembly CB2 is the incoming line protection switch of the secondary distribution station, switch 3 in switch assembly CB3 is the preceding stage protection switch of the incoming line of the secondary distribution station, and switch 4 in switch assembly CB4 is the incoming line protection switch of the primary distribution station; The optical transponders comprise upper-level optical transponders and lower-level optical transponders, the upper-level optical transponders are connected to switch assemblies CB3 and CB4 through optical fibers respectively, and the lower-level optical transponders are connected to switch assemblies CB1 and CB2 through optical fibers respectively; the lower-level optical transponders are configured to receive the blocking optical signal from switch assembly CB1 and to forward the blocking optical signal to switch assembly CB2; the upper-level optical transponders are configured to receive the blocking optical signal from switch assembly CB3 and to forward the blocking optical signal to switch assembly CB4; Switch assemblies CB2 and CB3 are connected through a cascade optical fiber, wherein switch assembly CB2 is configured to forward the blocking optical signal to switch assembly CB3 through the cascade optical fiber as soon as the blocking optical signal is received; Each switch assembly is further configured to send out a blocking optical signal and calculate a tripping time once a short-circuit fault is detected, and if the blocking optical signal is received before the tripping time, the operation of the switch in the switch assembly receiving the blocking optical signal is blocked, and if the blocking optical signal is not received until the tripping time, the switch in the switch assembly not receiving the blocking optical signal is caused to perform a tripping operation at the tripping time.

2. The global instantaneous trip protection device for a power distribution network according to claim 1, wherein The lower-level optical transponders comprise a first lower-level input interface and a first upper-level output interface, wherein switch assembly CB1 is connected to the first lower-level input interface through an optical fiber, and switch assembly CB2 is connected to the first upper-level output interface through an optical fiber; The upper-level optical transponders comprise a second lower-level input interface and a second upper-level output interface, wherein switch assembly CB3 is connected to the second lower-level input interface through an optical fiber, and switch assembly CB4 is connected to the second upper-level output interface through an optical fiber.

3. The global instantaneous protection device for power distribution networks according to claim 1, characterized in that, The switches comprise high-speed split-phase circuit breakers, the tripping time of which is less than 1.5 milliseconds, and the tripping dispersion of which is less than 0.2 milliseconds.

4. The global instantaneous protection device for power distribution networks according to claim 1, characterized in that, The secondary distribution station further comprises a lower-level backup power source controlled by a power source switching device; Each switch assembly is further configured to send out a start-up optical signal when a short-circuit fault is detected and the switch in the switch assembly not receiving the blocking optical signal is tripped; The lower-level optical transponders further comprise a first upper-level input interface and a first lower-level output interface, and the upper-level optical transponders further comprise a second upper-level input interface and a second lower-level output interface, wherein switch assembly CB2 is connected to the power source switching device; switch assembly CB4 is connected to the second upper-level input interface of the upper-level optical transponder through an optical fiber, and switch assembly CB3 is connected to the second lower-level output interface of the upper-level optical transponder through an optical fiber, Wherein, the switch assembly CB3 sends an enabling optical signal to the switch assembly CB2 through the cascaded optical fiber when detecting the short-circuit fault and tripping the switch 3, the switch assembly CB2 sends an enabling signal to the power switching device after receiving the enabling optical signal, the power switching device starts the power switching to switch to the lower-level backup power source after receiving the enabling signal; Wherein, the switch assembly CB4 sends an enabling optical signal when detecting the short-circuit fault and tripping the switch 4, and retransmits the enabling optical signal to the switch assembly CB3 through the upper-level optical repeater, the switch assembly CB3 retransmits the enabling optical signal to the switch assembly CB2 through the cascaded optical fiber, the switch assembly CB2 sends an enabling signal to the power switching device after receiving the enabling optical signal, the power switching device starts the power switching to switch to the lower-level backup power source after receiving the enabling signal.

5. A global instantaneous protection device for an electrical distribution network according to claim 4, characterized in that, The controller comprises an analog unit, a control unit, a signal input unit, a signal output unit and a power supply unit, wherein, The analog unit is configured to collect three-phase current and voltage, zero sequence current and voltage; The signal input unit comprises a first electrical interface and a first optical interface, the first electrical interface is used to detect the on-off state of the switch, and the first optical interface is configured with an optical receiving module for receiving the blocking optical signal and the enabling optical signal; The signal output unit comprises a second electrical interface and a second optical interface, the second electrical interface is used to output the closing signal for closing the switch, and the second optical interface is configured with an optical transmitting module for sending the enabling optical signal, the blocking optical signal and the tripping signal; The control unit is configured to: detect the short-circuit fault based on the three-phase current and voltage, the zero sequence current and voltage, and once detecting the short-circuit fault, send the blocking optical signal to the optical repeater or the upper-level controller through the optical transmitting module of the second optical interface, and calculate the tripping time: if the blocking optical signal is received through the optical receiving module of the first optical interface before the tripping time, retransmit the blocking optical signal through the optical transmitting module of the second optical interface to block the operation of the switch associated with the controller; if the blocking optical signal is not received until the tripping time, send the tripping signal to the switch associated with the controller through the optical transmitting module of the second optical interface to make the switch perform the tripping operation at the tripping time, and send the enabling optical signal to the optical repeater or the lower-level controller through the optical transmitting module; and When the enabling optical signal is received through the optical receiving module of the first optical interface, retransmit the enabling optical signal to the lower-level controller or the optical repeater through the optical transmitting module of the second optical interface; The power supply unit is used to supply power to the analog unit, the control unit, the signal input unit and the signal output unit.

6. A method for a global instantaneous protection of an electrical distribution network, characterized in that, The all-domain instantaneous trip protection method is implemented by the all-domain instantaneous trip protection device of any one of claims 1 to 5, and the all-domain instantaneous trip protection method comprises: If the short-circuit fault occurs at the end of the secondary power distribution station, the switch assembly CB1 sends a blocking optical signal to the lower-level optical transponder upon detecting the short-circuit fault, and calculates the switching-off time to make switch 1 perform the switching-off operation at the switching-off time; the lower-level optical transponder receiving the blocking optical signal transmits the blocking optical signal to the switch assembly CB2; the switch assembly CB2 receiving the blocking optical signal transmits the blocking optical signal to the switch assembly CB3 through the cascaded optical fiber; the switch assembly CB3 receiving the blocking optical signal transmits the blocking optical signal to the upper-level optical transponder; the upper-level optical transponder receiving the blocking optical signal transmits the blocking optical signal to the switch assembly CB4; the switch assemblies CB2, CB3 and CB4 receiving the blocking optical signal block the operation of the switches associated therewith before the switching-off time; If the short-circuit fault occurs on the bus of the secondary power distribution station, the switch assembly CB2 sends a blocking optical signal to the switch assembly CB3 through the cascaded optical fiber upon detecting the short-circuit fault, and calculates the switching-off time to make switch 2 perform the switching-off operation at the switching-off time; the switch assembly CB3 receiving the blocking optical signal transmits the blocking optical signal to the upper-level optical transponder; the upper-level optical transponder receiving the blocking optical signal transmits the blocking optical signal to the switch assembly CB4; the switch assemblies CB3 and CB4 receiving the blocking optical signal block the operation of the switches associated therewith before the switching-off time; If the short-circuit fault occurs on the connecting line between the secondary power distribution station and the primary power distribution station, the switch assembly CB3 sends a blocking optical signal to the upper-level optical transponder upon detecting the short-circuit fault, and calculates the switching-off time to make switch 3 perform the switching-off operation at the switching-off time; the upper-level optical transponder receiving the blocking optical signal transmits the blocking optical signal to the switch assembly CB4; the switch assembly CB4 receiving the blocking optical signal blocks the operation of the switch associated therewith before the switching-off time; If the short-circuit fault occurs on the bus of the primary power distribution station, the switch assembly CB4 calculates the switching-off time to make switch 4 perform the switching-off operation at the switching-off time upon detecting the short-circuit fault.

7. A global instantaneous protection method for an electrical distribution network according to claim 6, characterized in that, Further comprising: If the short-circuit fault occurs on the connecting line between the secondary power distribution station and the primary power distribution station, the switch assembly CB3 sends a starting optical signal to the switch assembly CB2 through the cascaded optical fiber upon detecting the short-circuit fault and making switch 3 perform the switching-off operation; The switch assembly CB2 receiving the starting optical signal sends a starting signal to the power switching device; The power switching device starts the power switching to switch to the lower-level standby power source upon receiving the starting signal.

8. The method for global instantaneous protection of an electrical distribution network according to claim 7, characterized in that, Further comprising: If the short-circuit fault occurs on the bus of the primary power distribution station, the switch assembly CB4 sends a starting optical signal to the upper-level optical transponder through the second upper-level input interface of the upper-level optical transponder upon detecting the short-circuit fault and making switch 4 perform the switching-off operation; The upper-level optical transponder receiving the starting optical signal transmits the starting optical signal to the switch assembly CB3; The switch assembly CB3 receiving the starting optical signal transmits the starting optical signal to the switch assembly CB2 through the cascaded optical fiber; The switch assembly CB2 receiving the starting optical signal sends a starting signal to the power switching device; The power switching device starts the power switching to switch to the lower-level standby power source upon receiving the starting signal. The power switching device starts power switching to switch to the lower-level standby power source after receiving the start signal.

9. A global instantaneous protection device for an electrical distribution network according to claim 8, characterized in that, The time for the lower-level optical transponder to receive the blocking optical signal from the switch assembly CB1 and to forward the blocking optical signal to the upper-level optical transponder is less than 50 microseconds.

10. A zonal under-reach protection device for an electrical distribution network according to any one of claims 6 to 9, characterised in that, The switching-off moment is related to the current zero-crossing moment, and the time interval from the switching-off moment to the current zero-crossing moment is not less than the switching-off time of the switch.

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