A self-healing method for differential protection of a multi-contact power supply system

Abstract

The application discloses a self-healing method for differential protection of a multi-contact power supply system, comprising an active power supply and a standby power supply, wherein a protection area switch capable of cutting off power supply of the active power supply or the standby power supply to the differential protection area is a to-be-operated switch, a comparison unit calculates a difference between a pulse corresponding to an inflow current and a pulse corresponding to an outflow current, and when the difference exceeds a threshold value, the comparison unit sends a trip signal to cut off the to-be-operated switch, and then closes the contact switch to make the standby power supply supply power, and for the to-be-operated switch which sends the pulse to the comparison unit through the optical fiber, the comparison unit sends the trip signal to the to-be-operated switch through the optical fiber. The method can realize rapid self-healing of other areas outside the protection area.

Description

Technical Field

[0001] This invention relates to the field of power line protection, and more specifically to a self-healing method for differential protection of multi-connection power supply systems. Background Technology

[0002] Differential protection is a line protection method. Traditional differential protection obtains parameters such as current and voltage at both ends of the line through current transformers (CTs), converts them into messages, and sends them to a computer. The computer interprets the messages and compares the current at the upstream and downstream points of the line to see if they are equal. If they are not equal, a fault is determined, and the line switch is disconnected to isolate the faulty line. However, the process of message writing, generation, transmission, reception, and interpretation involves many steps, including numerous devices, large computational load, complex algorithms, long overall processing time, and high difficulty in designing reliable devices. Invention patent CN 111463758 B discloses a power line protection method that converts the current at the power inlet and outlet into pulses through a voltage-to-frequency conversion circuit, and uses a comparison unit to compare the inlet pulse and outlet pulse for differential protection.

[0003] In a multi-connection power supply system, there are multiple power sources, namely the active power source supplying power to the system and the backup power source disconnected from the power supply area. When a certain differential protection zone cuts off the power input switch through differential protection, how to automatically continue to supply power to the remaining areas outside the fault point so that these areas can achieve self-healing, and further achieve low-cost, faster and safer self-healing, is a problem that must be solved to improve power supply quality and economic efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a self-healing method for differential protection of a multi-connection power supply system. After a fault occurs in the protected area, this method can not only quickly disconnect the switch at the power inlet of the protected area to clear the fault, but also use the original differential protection system to quickly disconnect the switch at the power outlet associated with the backup power supply, thereby achieving rapid self-healing in other areas outside the protected area.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A self-healing method for differential protection of a multi-connection power supply system includes one or more active power supplies and one or more backup power supplies. The power supply area of ​​the active power supply is set into a differential protection zone via a protection zone switch. The backup power supply is disconnected from the power supply area via a connection switch. The protection zone switch that can cut off the power supply from the active power supply or the backup power supply to the differential protection zone is a standby switch. The current of the protection zone switch is converted into pulses by a voltage-to-frequency conversion circuit and sent to a comparison unit. At least one of the standby switches sends the pulses to the comparison unit via an optical fiber. The comparison unit calculates the difference between the pulse corresponding to the current flowing into the protection zone switch and the pulse corresponding to the current flowing out of the protection zone switch during the same time period. When the difference exceeds a threshold, the comparison unit sends a trip signal to cut off the standby switch, and then closes the connection switch to supply power to the backup power supply. For the one or more standby switches that send pulses to the comparison unit via the optical fiber, the comparison unit also sends the trip signal to these standby switches via an optical fiber.

[0007] Preferably, the optical fiber through which the comparison unit sends the trip signal to the switch to be operated is the same optical fiber as the optical fiber through which the comparison unit receives pulses from the switch to be operated, or they are two different optical fibers.

[0008] Preferably, if the switch to be operated fails to trip after receiving the trip signal via optical fiber, it sends a trip signal to the next-level switch to be operated to trip the next-level switch to be operated. If the next-level switch to be operated is the tie switch, the tie switch remains open.

[0009] Preferably, the trip signal is a number of pulses or a pulse train with a duty cycle and a number of pulses.

[0010] Preferably, the switch to be operated, which transmits the pulse via optical fiber, initiates tripping after detecting the undervoltage of the differential protection line via a voltage transformer and receiving the tripping signal via optical fiber.

[0011] Preferably, the interconnecting switch detects the loss of voltage on the active power supply side through a voltage transformer. If no trip signal is received within a set delay waiting time, the interconnecting switch closes. If the interconnecting switch receives a trip signal, the interconnecting switch does not close.

[0012] Preferably, the optical fiber through which the comparison unit sends the trip signal to the switch to be operated is the same optical fiber as the optical fiber through which the comparison unit receives pulses from the switch to be operated, and the photoelectric conversion modules on both sides of the optical fiber are dual-wavelength multiplexed single-fiber transceiver integrated optical modules.

[0013] Preferably, the optical fiber through which the comparison unit sends the trip signal to the switch to be operated and the optical fiber through which the comparison unit receives pulses from the switch to be operated are two different optical fibers in the same optical fiber bundle, and the two ends of the optical fiber bundle adopt a dual-fiber transceiver integrated optical module.

[0014] In the above technical solution, a differential protection zone is set up through a protection zone switch. Then, a voltage-to-frequency conversion circuit is used to convert the current of the protection zone switch into pulses and transmit them to the comparison unit. This allows for rapid determination of whether a fault has occurred using the technology of invention patent CN 111463758 B. If a fault occurs, a trip signal is issued for the switches that need to be disconnected. If these switches are connected to the comparison unit via optical fiber, the trip signal is transmitted via optical fiber to trip these switches. The trip signal can be transmitted using the same optical fiber as the one that sends the pulse. This allows the original differential protection architecture to be used, requiring only the use of dual-wavelength multiplexed single-fiber transceiver modules at both ends of the optical fiber, thereby greatly reducing construction and equipment costs. Furthermore, this point-to-point dedicated optical fiber transmission can greatly reduce the complexity of the transmitted trip signal content. For example, the trip signal can be only a pulse train composed of the number of pulses or the duty cycle and the number of pulses. That is, the trip signal does not need to include protection zone coding, nor does it require message compilation or interpretation, making it both fast and safe. Alternatively, a trip signal can be transmitted using a different fiber from the one used for transmitting the pulse within the same fiber bundle. This fiber has already been pre-installed within the fiber bundle, thus incurring no additional cost. In this case, a dual-fiber transceiver module can be used. The resulting self-healing method for the power supply system is ingeniously designed and cost-effective, exhibiting extremely high speed and reliability. Attached Figure Description

[0015] Figure 1 A schematic diagram of the topology and differential protection settings for a first embodiment of a multi-connection power supply system (only the power supply and switches are shown, the load is not shown, and only one differential protection zone is shown; other protection zones are not shown).

[0016] Figure 2 A schematic diagram of the topology and differential protection settings for a second embodiment of a multi-connection power supply system (only the power supply and switches are shown, the load is not shown, and only one differential protection zone is shown; other protection zones are not shown).

[0017] Figure 3 A schematic diagram of the topology and differential protection settings for a third embodiment of a multi-connection power supply system (only the power supply and switch are shown, the load is not shown, and only one differential protection zone is shown; other protection zones are not shown). Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings:

[0019] Example 1

[0020] like Figure 1 As shown, the multi-connection power supply system includes power supply 100, power supply 200, and power supply 300. Power supply 100 is currently supplying power to the line area and is therefore the active power supply. Power supply 200 is disconnected from the power supply area via connection switch 12, and power supply 300 is disconnected from the power supply area via connection switch 10. Power supplies 200 and 300 are used as backup power supplies. Within the power supply area of ​​the active power supply 100, several differential protection zones are set up through switches on each branch line. For example, the areas within the inlet switch 5 where power flows in and the outlet switches 6, 7, and 8 where power flows out are set up as several protection zones (this embodiment uses this as an example; of course, several other differential protection zones can also be set up). The switches used to set up the protection zones, namely inlet switch 5, outlet switch 6, outlet switch 7, and outlet switch 8, are all called protection zone switches. Specifically, at the inlet switch 5 where electrical energy flows in, the current is acquired by the current transformer 1, then converted into pulses (i.e., electrical pulses) by the voltage-to-frequency conversion circuit VFC1 and transmitted to the comparison unit 15 (the voltage-to-frequency conversion circuit VFC1 and the comparison unit 15 can generally be set up on a single circuit board and located locally at the inlet switch 5, so that after the voltage-to-frequency conversion circuit VFC1 converts the current into pulses, it can be directly transmitted to the comparison unit 15 as an electrical signal; of course, the pulses converted by the voltage-to-frequency conversion circuit VFC1 can also be transmitted to the comparison unit 15 via optical fiber). At the outlet switch 6 where electrical energy flows out, the current is acquired by the current transformer 2, then converted into electrical pulses by the voltage-to-frequency conversion circuit VFC2, and then the electrical pulses are converted into optical pulses by the photoelectric conversion module 13 (which can convert electricity to light or light to electricity), and then transmitted to the photoelectric conversion module 14 (which can convert electricity to light or light to electricity) via optical fiber 16. The photoelectric conversion module 14 then converts the electrical pulses into electrical pulses. The electrical pulse is then transmitted to the comparison unit 15. Similarly, the current at the output switch 7 is obtained by the current transformer 3 and converted into an electrical pulse by the voltage-frequency conversion circuit VFC3. Then, it is transmitted to the photoelectric conversion module 14 via the photoelectric conversion module (not shown in the figure) and the optical fiber 17. The photoelectric conversion module converts it into an electrical pulse and then transmits it to the comparison unit 15. The current at the output switch 8 is obtained by the current transformer 4 and converted into an electrical pulse by the voltage-frequency conversion circuit VFC4. It is then converted into an optical pulse by the photoelectric conversion module and transmitted to the photoelectric conversion module 14 via the optical fiber 18. The photoelectric conversion module converts it into an electrical pulse and then transmits it to the comparison unit 15. The comparison unit 15 compares the difference between the input pulse corresponding to the input switch 5 and the sum of the output pulses corresponding to the three output switches 6, 7, and 8. If the difference exceeds the threshold, the first alarm signal is sent to the control device of the input switch 5. The control device operates the input switch 5 to trip, thereby eliminating the fault at the input switch 5.

[0021] At this point, since the fault point relative to power supplies 200 and 300 has not been eliminated, the connecting switches 12 and 10 cannot be directly closed to utilize the backup power supply. Only by tripping the exit switches 6 and 7 and then closing the connecting switches 10 and 12 can the power supply to the area outside the fault point be restored, thus achieving self-healing. In this invention, the protection zone switch capable of cutting off the supply of power from the active power supply or backup power to the differential protection zone is called a standby switch. For example, the inlet switch 5 can cut off the supply of power from the active power supply 100 to the differential protection zone, the outlet switch 6 can cut off the supply of power from the backup power supply 300 to the differential protection zone, and the outlet switch 7 can cut off the supply of power from the backup power supply 200 to the differential protection zone; therefore, all are standby switches. However, the outlet switch 8 cannot cut off the power supply to the differential protection zone; therefore, the outlet switch 8 is only a protection zone switch and not a standby switch. To achieve self-healing of the power supply area outside the differential protection zone, the following steps are taken:

[0022] First, after the inlet switch 5 trips, the photoelectric conversion module 14 on the comparator unit 15 side begins to emit optical signals (i.e., the photoelectric conversion module 14 can receive optical pulses and also emit optical signals). This optical signal is a trip signal, which can be the number of optical pulses or a pulse train with a duty cycle and pulse number. It is sent to the outlet switch 6 and outlet switch 7 respectively through optical fibers. The photoelectric conversion modules on the outlet switch 6 and outlet switch 7 side receive the trip signal (they can both emit optical pulses and receive optical signals), and then issue a second alarm signal. After receiving the second alarm signal, the operating mechanisms of outlet switch 6 and outlet switch 7 respectively operate outlet switch 6 and outlet switch 7 to trip. In a preferred embodiment, the optical fiber used by the photoelectric conversion module on the comparator unit 15 side to emit optical signals is the same optical fiber used by the comparator unit 15 side to receive optical pulses. In this case, the photoelectric conversion modules on both sides of the optical fiber are generally selected as dual-wavelength multiplexed single-mode single-fiber transceiver modules, and both transmission and reception can work independently. This can maximize the saving of optical fiber usage, which is especially advantageous when there are no other spare optical fibers in the fiber bundle. In another embodiment, the optical fiber used by the photoelectric conversion module on one side of the comparison unit 15 to transmit the optical signal is one of two fibers from the same fiber bundle as the optical fiber originally used to receive the optical pulse on the same side of the comparison unit 15. In this case, the photoelectric conversion modules on both sides of the optical fiber are generally dual-fiber transceiver modules. Using optical fiber to transmit the trip signal can utilize the existing differential protection hardware configuration, eliminating the cost added by setting up transmission methods such as 5G, and the signal transmission is faster and more secure, avoiding the disadvantages of low protection security caused by the instability of 5G transmission. In one embodiment, the outlet switch 6 and outlet switch 7 detect the voltage status of the differential protection line through a voltage transformer. After detecting the loss of voltage in the protection line and receiving the trip signal through the optical fiber, the trip is initiated, which can further ensure the safety of operation.

[0023] After the inlet switch 5 trips, the tie switches 12 and 10 detect the loss of voltage on the active power supply 100 side through the voltage transformer. After a set delay, after the preset outlet switches 6 and 7 trip, if the tie switches 10 and 12 do not receive a trip signal, they close and supply power to the outlet switches 6 and 7 after the trip through the backup power supply 300 and power supply 200, thereby achieving self-healing of the area outside the fault point.

[0024] In one embodiment, if a preset output switch fails to trip after receiving a trip signal via optical fiber (i.e., it does not trip), it sends a trip signal to the next-level switch to trip it. For example, if the photoelectric conversion module on the output switch 6 receives a trip signal and issues a second alarm signal, and output switch 6 fails to trip, it will send a trip signal to the next-level switch 9. Switch 9 will then trip upon receiving the trip signal, thereby enhancing the security of the protection. Similarly, if output switch 7 fails to trip, it will send a trip signal to trip switch 11. If the next-level switch is a tie switch 12 or a tie switch 13, then tie switch 12 or tie switch 13 remains open.

[0025] Example 2

[0026] like Figure 2 As shown, the difference from Embodiment 1 is that switch 8 is also connected to the active power supply 400. That is, both active power supply 100 and active power supply 400 supply power to the differential protection zone defined by switches 5, 6, 7, and 8. (Either active power supply 100 and active power supply 400 supply power to the differential protection zone simultaneously, or active power supply 100 and active power supply 400 alternately supply power to the differential protection zone. For example, active power supply 100 supplies power to the differential protection zone while charging active power supply 400, and then active power supply 400 supplies power to the differential protection zone.) While supplying power to the protected area, the existing power supply 100 is also charged. Correspondingly, switches 5 and 8 are both inlet switches, or one of them is an outlet switch (switch 8 is the outlet switch when charging the existing power supply 400, or switch 5 is the outlet switch when charging the existing power supply 100). However, both switches 5 and 8 can cut off the supply of power from the existing power supply 200 or 400 to the differential protected area. Switches 5, 6, 7, and 8 are all protected area switches capable of cutting off the supply of power from the existing or backup power supply to the protected area, and therefore are all switches awaiting operation. Similar to Embodiment 1, the comparison unit 15 compares the difference between the pulse corresponding to the inlet current at inlet switches 5 and 8 and the pulse corresponding to the outlet current at outlet switches 6 and 7. When this difference exceeds a threshold, the comparison unit issues an alarm signal and cuts off each switch awaiting operation. The transmission of pulses and optical signals via optical fibers is similar to or the same as in Embodiment 1. This will not be repeated here.

[0027] Example 3

[0028] The difference between this embodiment and Embodiment 1 is that switch 8 is not used as a protection zone switch. That is, the differential protection zone is only set via switches 5, 6, and 7. The current at switch 8 is not collected. The comparison unit only compares the difference between the pulses corresponding to the inlet currents and the pulses corresponding to the outlet currents at switches 5, 6, and 7, and then checks whether the difference exceeds a threshold. Specifically, the threshold must be equal to or greater than the pulse corresponding to the maximum power current flowing through switch 8; that is, the current corresponding to the maximum power of all loads in the branch below switch 8 is converted into pulses. For more information on this point, please refer to the invention patent application CN116593935A. Other operations are the same as or similar to Embodiment 1, and will not be repeated here.

[0029] The above embodiments are merely illustrative of the concept and implementation of the present invention and are not intended to limit it. Under the concept of the present invention, technical solutions without substantial changes are still within the scope of protection.

Claims

1. A self-healing method for differential protection of a multi-connection power supply system, comprising one or more active power supplies and one or more backup power supplies, wherein the power supply area of ​​the active power supply is set into a differential protection zone via a protection zone switch, and the backup power supply is disconnected from the power supply area via a connection switch, wherein a protection zone switch capable of cutting off the power supply from the active power supply or the backup power supply to the differential protection zone is a switch to be operated, wherein the current of the protection zone switch is converted into pulses by a voltage-to-frequency conversion circuit and sent to a comparison unit, and at least one of the switches to be operated transmits the pulses to the comparison unit via an optical fiber, wherein the comparison unit calculates the difference between the pulse corresponding to the current flowing into the protection zone switch and the pulse corresponding to the current flowing out of the protection zone switch during the same time period, and when the difference exceeds a threshold, the comparison unit issues a trip signal to cut off the switch to be operated, and then closes the connection switch to supply power to the backup power supply, characterized in that: For a switch to be operated that uses the optical fiber to send pulses to the comparison unit, the comparison unit sends the trip signal to the switch to be operated via the optical fiber.

2. The self-healing method for differential protection of multi-connection power supply systems as described in claim 1, characterized in that: The optical fiber through which the comparison unit sends the trip signal to the switch to be operated is the same optical fiber as the optical fiber through which the comparison unit receives pulses from the switch to be operated, or they are two different optical fibers.

3. The self-healing method for differential protection of multi-connection power supply systems as described in claim 1, characterized in that: If the switch to be operated fails to trip after receiving the trip signal via optical fiber, it sends a trip signal to the next-level switch to be operated to trip the next-level switch to be operated. If the next-level switch to be operated is the tie switch, the tie switch remains open.

4. The self-healing method for differential protection of multi-connection power supply systems as described in claim 1, 2, or 3, characterized in that: The trip signal is either the number of pulses or a pulse train with a duty cycle and a number of pulses.

5. The self-healing method for differential protection of multi-connection power supply systems as described in claim 1, characterized in that: The switch to be operated, which transmits the pulse via optical fiber, initiates tripping after detecting the undervoltage of the differential protection line via a voltage transformer and receiving the tripping signal via optical fiber.

6. The self-healing method for differential protection of a multi-connection power supply system as described in claim 1, characterized in that: The interconnecting switch detects the loss of voltage on the active power supply side through a voltage transformer. If no trip signal is received within the set delay waiting time, the interconnecting switch closes. If the interconnecting switch receives a trip signal, the interconnecting switch does not close.

7. The self-healing method for differential protection of a multi-connection power supply system as described in claim 2, characterized in that: The optical fiber through which the comparison unit sends the trip signal to the switch to be operated is the same optical fiber through which the comparison unit receives pulses from the switch to be operated, and the photoelectric conversion modules on both sides of the optical fiber are dual-wavelength multiplexed single-fiber transceiver integrated optical modules.

8. The self-healing method for differential protection of a multi-connection power supply system as described in claim 2, characterized in that: The optical fiber through which the comparison unit sends the trip signal to the switch to be operated and the optical fiber through which the comparison unit receives the pulse from the switch to be operated are two different optical fibers in the same optical fiber bundle, and the two ends of the optical fiber bundle adopt a dual-fiber transceiver integrated optical module.

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