Adaptive directional lockout overcurrent protection method for closed loop operation of a ship power supply network

Abstract

The application relates to an adaptive directional lockout overcurrent protection method for closed-loop operation of a ship power supply network. In view of the complex topological structure and dynamic operation characteristics of the ship power supply system in closed-loop operation, the protection method introduces a directional judgment and a multi-point information fusion protection concept, designs a protection strategy with directional recognition ability and a multi-point cooperative mechanism, can effectively cope with challenges such as system operation mode switching, load mutation and short-circuit current increase, realizes rapid, accurate and reliable fault positioning and isolation of the ship power supply system under different operation conditions, significantly reduces the protection misoperation and refusal risk, improves the system fault handling efficiency and power supply continuity, and provides a powerful guarantee for the safe operation of the ship power system.

Description

Technical Field

[0001] This invention relates to the field of power supply protection technology, and in particular to an adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network. Background Technology

[0002] Traditional overcurrent protection is one of the most basic and commonly used protection methods in power systems. Its core principle is to detect whether the current in the line exceeds a set threshold (i.e., overcurrent setting) to determine whether a short circuit or overload fault has occurred, and trigger protection actions (such as circuit breaker tripping) accordingly to isolate the fault area and prevent the fault from spreading.

[0003] In the closed-loop operation mode of ship power supply system, traditional overcurrent protection methods face many challenges and are difficult to meet the system's requirements for high reliability, high selectivity and fast response.

[0004] First, traditional overcurrent protection lacks directional judgment capability, failing to identify the direction of fault current flow. This leads to poor selectivity in closed-loop systems, potentially causing cascading trips, expanding the outage area, and affecting the normal operation of critical equipment. Second, traditional protection has limited detection capabilities for low-current or high-impedance faults, especially in closed-loop operation where fault current may be shunted, making timely response difficult and increasing system operational risks. Furthermore, the operating conditions of shipboard closed-loop power supply systems are complex and variable. Traditional overcurrent protection settings are typically fixed, making it difficult to adapt to dynamic operating conditions, easily leading to maloperation or failure to operate, reducing system safety and stability. In summary, traditional overcurrent protection in closed-loop operation suffers from a series of problems, including poor selectivity, low sensitivity, difficult setting, slow response speed, lack of directionality, poor coordination, and complex maintenance. Therefore, there is an urgent need to introduce new protection strategies such as directional protection, adaptive protection, and station-domain protection to improve the safety and intelligence of shipboard power supply systems. Summary of the Invention

[0005] To address the problems of poor selectivity, low sensitivity, difficult setting, slow response speed, lack of directionality, and poor coordination in traditional overcurrent protection in closed-loop systems, an adaptive directional blocking overcurrent protection method for closed-loop operation of ship power supply networks is proposed. By introducing the concepts of directional judgment and multi-point information fusion protection, the method can achieve rapid, accurate, and reliable fault location and isolation of ship power supply systems under different operating conditions, thereby improving the safety, stability, and intelligence level of system operation.

[0006] The technical solution of this invention is: an adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network, comprising the following steps: 1) In the closed-loop power supply network of the ship, each circuit breaker is equipped with a comprehensive protection device, which includes directional elements and overcurrent elements, forming a check unit; 2) Collect voltage and current signals at each circuit breaker in real time to determine whether an overcurrent fault has occurred; 3) When an overcurrent fault occurs, the short-circuit current direction determination is initiated, and the actual direction of the short-circuit current is determined based on the phase difference between the voltage and current signals; 4) Each inspection unit sends a blocking signal in the opposite direction of the short-circuit current it detects; 5) The controller determines the area between two adjacent nodes that send interlocking signals in different directions as the fault area based on the direction of the interlocking signals sent by each inspection unit, and uses these two adjacent nodes as the fault isolation point. 6) The inspection unit that meets the tripping conditions shall perform the tripping operation: the tripping condition is that the local overcurrent protection is activated and no blocking signal is received.

[0007] Furthermore, the mathematical expression for the tripping condition is: In the formula, it refers to No interlocking signal received Set the local overcurrent protection start value.

[0008] Furthermore, the blocking signal is transmitted between the integrated protection devices via at least one communication medium, such as optical fiber, power line, or wireless network.

[0009] Furthermore, when the blocking signal is directed toward the busbar, all other circuit breakers connected to the busbar, except for the circuit breaker that sends the blocking signal toward that busbar, are blocked.

[0010] Furthermore, when a line fault occurs, the inspection units on both sides of the fault point send blocking signals to their respective busbars, causing the protection units on both sides of the fault point to activate because they have not received the blocking signals, while the remaining protection units are blocked.

[0011] Furthermore, when a busbar fault occurs, all inspection units connected to the faulty busbar do not receive a blocking signal and thus trip, while the protection units on the remaining non-faulty busbars are blocked.

[0012] Furthermore, the method is applicable to at least one of the following fault types in a ship's power supply network: jumper wire fault, bus fault, generator terminal fault, and load-side fault.

[0013] Furthermore, the adaptive directional blocking overcurrent protection method unifies the action time and current setting of the backup protection, eliminating the need for coordination between upper and lower levels through time differences.

[0014] Furthermore, when a circuit breaker trips first due to not receiving a blocking signal, the system re-evaluates the short-circuit current path. If the conditions for releasing the blocking of the originally blocked circuit breaker are met, the circuit breaker will trip after a delay to complete the fault isolation.

[0015] Furthermore, the reliability of the protection system is improved through a communication self-testing mechanism between the integrated protection devices.

[0016] The beneficial effects of this invention are as follows: The adaptive directional blocking overcurrent protection method for closed-loop operation of ship power supply network of this invention is designed with directional identification capability and multi-point coordination mechanism to address the complex topology and dynamic operating characteristics of ship power supply system in closed-loop operation. It can effectively cope with challenges such as system operation mode switching, load change, and short-circuit current increase, thereby significantly reducing the risk of protection maloperation and failure to operate, improving system fault handling efficiency and power supply continuity, and providing strong guarantee for the safe operation of ship power system. Attached Figure Description

[0017] Figure 1A This is a schematic diagram of the power supply network during normal operation in the adaptive directional blocking protection principle of this invention; Figure 1B This is a schematic diagram of the locking direction after a fault in the adaptive directional locking protection principle of the present invention; Figure 2A This is a topology diagram of the closed-loop power supply network for line faults in this invention; Figure 2B This is a topology diagram of the closed-loop power supply network for bus faults in this invention; Figure 3 This is a schematic diagram of a line fault according to an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating a fault in the jumper cable during a stand-alone operation in an embodiment of the present invention. Figure 5 This is a schematic diagram of a busbar fault according to an embodiment of the present invention; Figure 6 This is a schematic diagram of a generator terminal fault according to an embodiment of the present invention; Figure 7 This is a schematic diagram of a load-side fault according to an embodiment of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0019] When traditional backup protection is applied to closed-loop power supply network protection, it becomes difficult to coordinate with dead loops and fault location isolation protection. This makes it challenging to resolve the conflict between improving power supply reliability and balancing the speed and selectivity of backup protection in closed-loop power supply networks. Therefore, an adaptive directional blocking overcurrent protection scheme is proposed. For marine closed-loop power supply networks, a communication-based adaptive cascaded directional blocking protection scheme is adopted. This scheme exhibits good adaptability to different power supply network topologies, operating modes, and faulty components.

[0020] Figure 1A This is a schematic diagram of the power supply network during normal operation in the adaptive directional blocking protection principle. In the ship's closed-loop power supply network, each protection unit consists of a check unit connected in series with directional elements and overcurrent elements, such as... Figure 1A Inspection units PR1, PR2, and PR3 are installed on the three circuit breakers on one power supply line in the network.

[0021] When a short-circuit fault occurs in a power supply circuit, all overcurrent devices on the same circuit are activated, initiating a short-circuit current direction determination process. The direction of the short-circuit current is determined by collecting the voltage and current signals flowing through each circuit breaker and analyzing the phase difference between these signals. The blocking signal is the reverse direction of the determined short-circuit current. Figure 1B The diagram illustrates the blocking direction after a fault in the adaptive directional blocking protection principle. For example, when fault F1 occurs, a short-circuit current is fed to the fault point. The short-circuit current direction checking unit PR1 detects it as rightward, while checking units PR2 and PR3 detect it as leftward. Therefore, the blocking signal is the opposite direction of the short-circuit current signal; that is, checking unit PR1 outputs a leftward blocking signal, and checking units PR2 and PR3 output a rightward blocking signal. Thus, the controller determines that the area between two adjacent nodes that issue blocking signals in different directions is the fault region. These two adjacent nodes serve as isolated fault points. The fault at F1 is selectively cleared by protections PR1 and PR2, while the remaining protections are notified to block. Here, blocking means that the circuit breaker in the closed state is not allowed to open.

[0022] After the controller receives the overcurrent signal and initiates short-circuit current direction analysis, it determines the isolated fault point based on the blocking signal and then enters fault protection. At this time, the protection trip condition of the adaptive directional blocking overcurrent protection principle is that the local overcurrent protection is activated and no blocking signal is received. In the formula, it refers to No interlocking signal received Set the local overcurrent protection start value.

[0023] Unlike differential protection, which needs to overcome issues such as synchronous sampling and real-time exchange of large amounts of sampled information from dual / multi-terminal sources, directional blocking principle can achieve full-line rapid operation during line faults. It also eliminates the need for synchronous sampling and has low communication bandwidth requirements. By using communication to exchange blocking signals, control cables can be significantly reduced, improving interoperability between protection systems. Furthermore, the communication self-testing mechanism can be fully utilized to enhance protection reliability.

[0024] In shipboard power supply networks, various media such as fiber optics, power lines, and even wireless networks can be selected to transmit and receive blocking signals, depending on different needs. It should be noted that when the blocking direction is towards the busbar, all circuit breakers connected to the busbar, except those sending the blocking signal towards the busbar, are blocked.

[0025] Take a simple ring network as an example. When a fault occurs in the ring network, the direction of the fault is determined by the directional element, and the blocking direction is the opposite direction of the short-circuit current.

[0026] In actual power grid protection, each switch is equipped with an integrated protection device. The protection of the power grid is controlled by the integrated protection device. The circuit breaker in the example diagram is open only to indicate how many circuit breakers are currently open. Under normal operating conditions, all circuit breakers in the diagram are closed. When a fault occurs, the integrated protection device at each node will calculate and analyze the data and issue a tripping command to the circuit breaker. The circuit breaker closest to the fault point should trip, while other distant circuit breakers remain closed. In the example diagram, the red arrow indicates the direction of the short-circuit current fed from the generator to the fault point during a fault. The gray area indicates the direction of the blocking signal. The integrated protection device at each circuit breaker collects the voltage and current signals flowing through the circuit breaker, calculates the direction of the short-circuit current, and then sends a blocking signal in the opposite direction of the short-circuit current.

[0027] The above rules are explained using the two basic fault types of line faults and bus faults respectively.

[0028] 1) such as Figure 2A The diagram shows the topology of a closed-loop power supply network with line faults. When a line fault occurs, the current collection characteristics at fault point F1 are as follows: Figure 2A As shown, for the lower protection device of the left crossover connection, the short-circuit current direction is from the busbar where the B bus tie is located to the line. Therefore, this protection device sends a blocking signal to the busbar where the B bus tie is located, blocking the B bus tie switch and the G4 unit switch. For the upper protection device of the left crossover connection, the short-circuit current direction is from the busbar where the A bus tie is located to the line. Therefore, it sends a blocking signal to the busbar where the A bus tie is located, blocking the A bus tie switch and the G1 unit switch. Ultimately, only the protection devices on both sides of the fault point operate because they do not receive blocking signals, and the line fault is selectively cleared.

[0029] 2) When a busbar fault occurs, the current-carrying characteristics of fault point F2 are as follows: Figure 2BAs shown, the blocking direction of each protection device on the faulty bus is opposite to that bus. Except for the circuit breaker connected to the faulty bus, which did not receive a blocking signal, all other line protections are reliably blocked.

[0030] Adaptive directional blocking backup protection unifies the time and current settings of backup protection by blocking backup protection for non-faulty lines, solving the problems of low sensitivity and dead loops in protection coordination. It achieves fault location identification, disconnecting only the faulty line when a short-circuit fault occurs, maximizing the preservation of the ship's power supply system's capabilities. This solves the problem of traditional backup protection schemes being unable to distinguish fault locations, and also addresses the difficulty of traditional protection schemes in ensuring the reliability of closed-loop power supply networks, guaranteeing strong power supply continuity. Adaptive directional protection achieves coordination between levels by sending blocking signals, eliminating the need for cascading time differences. Therefore, adaptive directional blocking backup protection can set uniform time settings for backup protection at all locations, resolving the contradiction between speed and selectivity in traditional backup protection applications in closed-loop power supply networks.

[0031] Case 1: Fault on the jumper wire side: When a fault occurs at the left crossover point of the line, the current flow trend is as follows: Figure 3 As shown, only circuit breakers CB5 and CB6 did not receive a blocking signal and therefore operated, as indicated by the red box in the figure; all other circuit breakers were blocked. If the blocking direction of CB5 points towards busbar 1, then CB1 and bus tie A circuit breakers connected to the busbar, excluding CB5, are blocked.

[0032] like Figure 4 As shown in the left figure, G1 is on the network, and a short-circuit fault occurs on the left cross line. Based on the blocking direction at bus tie A and the previously mentioned blocking principle, the faulty branch CB5 is blocked, while the blocking at other locations is normal. Since CB6 is not blocked, it will disconnect first. Subsequently, the short-circuit current will flow directly into the fault point through CB1 and CB5, no longer flowing through bus tie A. Therefore, bus tie A will no longer send a blocking signal to CB5. At this time, CB5 is released from blocking. Figure 4 As shown in the right figure, CB5 disconnects after a time delay, isolating the fault.

[0033] Case 2: Busbar Fault When busbar 1 fails, the current flow trend is as follows: Figure 5 As shown, at this time, none of the circuit breakers connected to bus 1 received a blocking signal and operated, and the remaining circuit breakers were blocked.

[0034] Case 3: Generator terminal fault: When a fault occurs at the generator G1 terminal, the current flow trend is as follows: Figure 6As shown, at this time only circuit breaker CB1 did not receive a blocking signal and operated, while all other circuit breakers were blocked.

[0035] Case 4: Load-side fault: When a load-side fault occurs, the bus flow trend is as follows: Figure 7 As shown, at this time only circuit breaker CB9 did not receive a blocking signal and operated, while all other circuit breakers were blocked.

[0036] The embodiments described above merely illustrate specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An adaptive directional blocking overcurrent protection method for closed-loop operation of a ship's power supply network, characterized in that, Includes the following steps: 1) In the closed-loop power supply network of the ship, each circuit breaker is equipped with a comprehensive protection device, which includes directional elements and overcurrent elements, forming a check unit; 2) The voltage and current signals at each circuit breaker are collected in real time to determine whether an overcurrent fault has occurred. 3) When an overcurrent fault occurs, the short-circuit current direction judgment is initiated, and the actual direction of the short-circuit current is determined based on the phase difference between the voltage and current signals; 4) Each inspection unit sends a blocking signal in the opposite direction of the short-circuit current it detects. 5) The controller determines the area between two adjacent nodes that send blocking signals in different directions as the fault area based on the direction of the blocking signals sent by each inspection unit, and uses these two adjacent nodes as the fault isolation point; 6) Inspection units that meet the tripping conditions perform the tripping operation: the tripping condition is that the local overcurrent protection is started and no blocking signal is received.

2. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, The mathematical expression for the tripping condition is: In the formula, it refers to No interlocking signal received Set the local overcurrent protection start value.

3. The method according to claim 1, characterized in that, The blocking signal is transmitted between the integrated protection devices via at least one communication medium, such as optical fiber, power line, or wireless network.

4. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, When the blocking signal is directed toward the busbar, all other circuit breakers connected to the busbar, except for the circuit breaker that sent the blocking signal toward that busbar, are blocked.

5. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, When a line fault occurs, the inspection units on both sides of the fault point send blocking signals to their respective busbars, causing the protection units on both sides of the fault point to activate because they have not received the blocking signals, while the remaining protection units are blocked.

6. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, When a busbar fault occurs, all inspection units connected to the faulty busbar do not receive a blocking signal and thus trip, while the protection units on the remaining non-faulty busbars are blocked.

7. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, The method is applicable to at least one of the following fault types in a ship's power supply network: jumper fault, bus fault, generator terminal fault, and load-side fault.

8. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, The adaptive directional blocking overcurrent protection method unifies the action time and current setting of the backup protection, eliminating the need for coordination between upper and lower levels through time differences.

9. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, When a circuit breaker trips first due to not receiving a blocking signal, the system re-evaluates the short-circuit current path. If the conditions for releasing the blocking of the originally blocked circuit breaker are met, the circuit breaker will trip after a delay to complete the fault isolation.

10. The adaptive directional blocking overcurrent protection method for closed-loop operation of a ship power supply network according to claim 1, characterized in that, The integrated protection devices improve the reliability of the protection system through a communication self-test mechanism.

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