Real-time online protection setting method suitable for ship looped network

Abstract

The invention relates to a real-time protection online setting method suitable for a ship closed-loop power grid, and the method comprises the steps: adding an online setting device for protection on the basis of a preset loop-opening point backup protection scheme, forming an online setting calculation scheme based on a preset loop-opening point, and enabling the online setting device to monitor a fault through a starting element, when the protected starting element detects that a fault occurs, a starting signal is provided for the measuring element, otherwise, protection is locked; when the starting element detects that a fault occurs, the online setting device calculates equivalent impedance and equivalent potential of the system according to data measured in real time, and automatically updates a setting value. The method can effectively solve the problem that a traditional open-loop protection method is insufficient in selectivity and sensitivity under a closed-loop topological structure, solves the problem that a traditional protection setting method is difficult to ensure the sensitivity and selectivity under a closed-loop power grid structure, and achieves the real-time matching and online adjustment of a protection setting value and an operation mode.

Description

Technical Field

[0001] This invention belongs to the field of marine power system protection technology, specifically relating to a real-time online protection setting method and system suitable for closed-loop power grid topology. By coordinating the preset loop-breaking point and the online setting device, the protection selectivity and sensitivity problems caused by bidirectional power flow are solved. Background Technology

[0002] Figure 1 This is a closed-loop power grid topology diagram for AC dual-power stations, with two generating units per station. The current traditional protection setting scheme is as follows: The backup protection time setting principle for the traditional open-loop network is that when a three-phase or two-phase short-circuit fault occurs in the power grid and the main protection fails to operate, the short-delay protection will adopt a time-delay action strategy: the load circuit breaker will operate first, followed by the jumper circuit breaker, then the bus tie circuit breaker, and finally the generator circuit breaker. The setting principle is that the generator, bus tie, and jumper short-delay setting values ​​are set according to 2.56 times the rated current of a single generator unit; the load short-delay setting value is set according to 2.56 times the rated current of the load.

[0003] Traditional protection setting schemes are not entirely applicable to closed-loop power grid topologies. While improving the reliability and safety of the ship's power system, the closed-loop operation mode also increases its operational complexity. During closed-loop operation, issues such as bidirectional power flow and bidirectional power generation arise, posing challenges to traditional protection setting schemes for ship power systems. Therefore, there is an urgent need to propose a real-time online protection setting method suitable for ship ring networks, aiming to achieve real-time matching and online adjustment of protection settings with the operating mode.

[0004] Among existing related technologies, such as the online setting method for relay protection disclosed in patent document (CN103474972A), although online setting is achieved, it has three key drawbacks: 1) it relies on step-by-step recursive calculation, resulting in low efficiency; 2) it does not consider the special characteristics of ring network topology; and 3) the setting process may affect the operation of upstream protection. For example, the adaptive setting method for setting values ​​based on a full-model protection of distribution networks disclosed in patent document (CN115588961A) has the following problems: 1) it relies on Pearson coefficient matching based on historical data, resulting in insufficient real-time performance; 2) it is only applicable to radial distribution network structures; and 3) it cannot handle bidirectional fault currents in closed-loop systems.

[0005] Furthermore, when a fault is detected in the line or the load circuit breaker fails to operate, the traditional time-based setting principle lacks selectivity, making it difficult to guarantee the improved reliability of the closed-loop power supply network. Therefore, it is urgent to propose a real-time protection online setting method suitable for shipboard closed-loop power grids, aiming to achieve real-time matching and online adjustment of protection settings and operating modes. Summary of the Invention

[0006] The problem this invention aims to solve is to propose a real-time protection online setting method suitable for ship closed-loop power grids, with the goal of achieving real-time matching and online adjustment of protection settings and operating modes. Under closed-loop operation, the operating state of a ship is more variable, and the direction of power flow is more complex. Problems such as bidirectional power flow and bidirectional power flow cause the short-circuit current flowing through the lines to become shunt, leading to a decrease in the protection sensitivity of traditional protection setting schemes.

[0007] To achieve the above objectives, the technical solution of the present invention is: a real-time protection online setting method suitable for ship closed-loop power grids. Based on a backup protection scheme with a preset loop break point, an online setting device is added to the protection to form an online setting calculation scheme based on the preset loop break point. The online setting device uses a starting element to monitor faults. When the starting element of the protection detects a fault, it provides a starting signal to the measuring element; otherwise, it locks out the protection. When the starting element detects a fault, the online setting device calculates the equivalent impedance and equivalent potential of the system based on real-time measured data and automatically updates the setting value.

[0008] Furthermore, by monitoring fault conditions through the starting element, if the starting element is triggered, the preset unlooping point is disconnected, unlooping the ring network structure into an open-loop structure, and the setting value is calculated online according to the system operating status.

[0009] Furthermore, the online setting time of the load-side protection is set to t. DP The online setting device delay for L2 cross-line protection is t. DP +4Δt, where no online setting device is configured at the loop unblocking point, and the online setting device delay of the protection at the bus tie switch is consistent with that of the cross line L2.

[0010] Furthermore, the fault monitoring of the starting element adopts the current change in the starting element to monitor phase-to-phase faults and ground faults, including phase-to-phase current change in the starting element and zero-sequence current change in the starting element for judgment.

[0011] Furthermore, the criterion for initiating the interphase current surge is as follows:

[0012]

[0013] In the formula This refers to the three phases AB, BC, and CA. K refers to a specific point in the current time of the protection sampling. T = 24 is the number of sampling points per week. KT refers to the value taken from point K one week ago, and K-2T refers to the value taken from point K two weeks ago. QD The starting current setting for phase-to-phase changes can be adjusted to a sensitivity coefficient greater than 1.2 under the condition of satisfying the minimum short-circuit current of the system.

[0014] Criterion for starting element with zero-sequence current mutation:

[0015] Δ3I0>I QD0

[0016] In the formula, Δ3I0 is the zero-sequence current abrupt change, I QD0 The starting current setting for zero-sequence change can be adjusted to a sensitivity coefficient greater than 1.2 under the condition of satisfying the minimum zero-sequence current of the system.

[0017] Furthermore, the calculation formula for interphase overcurrent setting is as follows:

[0018]

[0019] In the formula K is the phase electromotive force of the system's equivalent power source. sen Z is the sensitivity coefficient, which is 1.2. S This is the equivalent system impedance, which will vary depending on the system's operating mode. Z L This is the impedance of the entire protected crossover line. Since the crossover line impedance is relatively small, this value is ignored.

[0020] Furthermore, when a phase-to-phase fault occurs in the system, the system impedance Z in the phase-to-phase overcurrent setting calculation formula is... S The fault supplementary network is obtained by combining the fault component method. Let the direction of the busbar to the cross-line be the positive direction of the current, and M be the protection installation point. The corresponding positive sequence fault supplementary network is obtained by using the symmetrical component method.

[0021] Furthermore, when the system is operating in open loop, approximately 0.5Z is located within the L1 zone across the line. L1 When a fault occurs, the system's equivalent positive sequence impedance Z 1m The positive sequence component is obtained by measuring it at device M, i.e.

[0022]

[0023] When the system power supply side impedance Z S When it is known, the system's equivalent potential is

[0024] E m =U m +I m Z S

[0025] In the formula U m I m To protect the voltage and current at the M installation point.

[0026] When the system is operating in open loop, the fault occurs at 0.75Z across line L1. L At this time, the equivalent positive-sequence impedance Z of the system in the positive-sequence fault-addition network is... 1m It can be approximated as the following formula

[0027]

[0028] The location relationship between the fault point and the protection M, as well as the positive sequence system impedance calculated online, are summarized in the table.

[0029] Furthermore, the zero-sequence overcurrent setting calculation formula is as follows:

[0030]

[0031] In the formula Z is the system's equivalent zero-sequence potential. S0 It is the zero-sequence equivalent system impedance, which varies with the system's operating mode.

[0032] Furthermore, when the system is operating in open loop and a fault occurs outside the positive zone of protection M, the zero-sequence equivalent system impedance Z at protection M in the zero-sequence fault supplementary network of the system is... 0m It can be determined by measuring the zero-sequence component, i.e.

[0033]

[0034] When the system is operating in open loop, the 0.25Z area within the L1 zone of the cross-line... L When a fault occurs, the zero-sequence equivalent system impedance Z at protection M in the zero-sequence fault supplementary network of the system is... 0m It can be determined by measuring the zero-sequence component, i.e.

[0035]

[0036] The location relationship between the fault point and the protection M, as well as the zero-sequence system impedance calculated online, are summarized in the table.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. This invention proposes a real-time protection online setting method suitable for ship closed-loop power grids;

[0039] 2. The technical approach of this method primarily involves monitoring fault conditions through a starting element. If the starting element is triggered, a preset loop-breaking point is disconnected, breaking the ring network structure into an open-loop structure. The setting value is then calculated online based on the system's operating status. This method effectively addresses the insufficient selectivity and sensitivity of traditional open-loop protection methods in closed-loop topologies. By fully utilizing the electrical status information of the entire network and adapting to changes in ring network topology and operating modes, it solves the problem of traditional protection setting methods failing to guarantee sensitivity and selectivity in closed-loop power grid structures, achieving real-time matching and online adjustment of protection settings and operating modes. Attached Figure Description

[0040] Figure 1 This is a closed-loop power grid topology diagram for AC dual power plants, with two generating units per power plant;

[0041] Figure 2 This is a flowchart of the online tuning calculation based on preset solution loop points;

[0042] Figure 3 This is a schematic diagram of the component delay in the online tuning calculation scheme based on preset loop resolution points;

[0043] Figure 4 This is a closed-loop diagram of four generating units;

[0044] Figure 5 A diagram showing the additional network for faults within the positive sequence region (0.5Z) L1 );

[0045] Figure 6 A diagram showing the additional network for faults within the positive sequence region (0.75Z) L1 );

[0046] Figure 7 Additional network diagram for the open-loop operation protection M positive zone external fault zero-sequence fault;

[0047] Figure 8 A supplementary network diagram for zero-sequence faults in the L1 zone of the cross-line during open-loop system operation;

[0048] Figure 9 This is a schematic diagram of a load-side fault.

[0049] Figure 10 A schematic diagram for solving loop point faults;

[0050] Figure 11 This is a schematic diagram of a cross-line L2 fault. Detailed Implementation

[0051] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] like Figures 1 to 11 As shown, this invention provides a real-time protection online setting method for a ship's closed-loop power grid. Based on a preset loop-break point backup protection scheme, an online setting device is added to the protection, forming an online setting calculation scheme based on the preset loop-break point. The online setting device uses a starting element to monitor faults. When the protection's starting element detects a fault, it provides a starting signal to the measuring element; otherwise, it locks out the protection. When the starting element detects a fault, the online setting device calculates the system's equivalent impedance and equivalent potential based on real-time measured data and automatically updates the setting value. Its online setting calculation flowchart is shown below. Figure 2 As shown.

[0053] The online setting device for load-side protection in the scheme has a delay of t. DP The online setting device delay for L2 cross-line protection is t.DP +4Δt. No online setting device is configured at the loop-breaking point; the online setting device delay at the bus tie switch is consistent with that of the cross-line L2.

[0054] The delay relationships of each component are as follows: Figure 3 As shown in the diagram. In this scheme, t DP Δt should be appropriately small. In the diagram, DP and L2P represent the online setting delay of the protection devices at the load and L2 cross-line. Current surges can be used to activate components to monitor phase-to-phase and ground faults.

[0055] Criteria for starting element based on interphase current change

[0056]

[0057] In the formula This refers to the three phases AB, BC, and CA. K refers to a specific point in the current time of the protection sampling. T = 24 is the number of sampling points per week. (KT) refers to the value taken one week ago from point K, and (K-2T) refers to the value taken two weeks ago from point K. QD The starting current setting for phase-to-phase changes can be adjusted to a sensitivity coefficient greater than 1.2 under the condition of satisfying the minimum short-circuit current of the system.

[0058] Criterion for starting element with zero-sequence current mutation:

[0059] Δ3I0>I QD0

[0060] In the formula, Δ3I0 is the zero-sequence current abrupt change, I QD0 The starting current setting for zero-sequence change can be adjusted to a sensitivity coefficient greater than 1.2 under the condition of satisfying the minimum zero-sequence current of the system.

[0061] The formula for calculating phase-to-phase overcurrent setting is as follows:

[0062]

[0063] In the formula K is the phase electromotive force of the system's equivalent power source. sen Z is the sensitivity coefficient, which is 1.2. S This is the equivalent system impedance, which will vary depending on the system's operating mode. L This is the impedance of the entire protected crossover line. Since the crossover line impedance is small, this value can be ignored.

[0064] When a phase-to-phase fault occurs in the system, in the above formula, the protected system impedance Z S The fault can be determined using a combination of fault-addition networks and fault component methods. For example... Figure 4 As shown in the figure, the direction of the current from the busbar to the cross-line is considered to be the positive direction, and M is the location where the protection is installed.

[0065] Since the four generators in the topology are of the same model, the impedance of all four generators can be represented by Z. g1 express.

[0066] Z g1 =Z g1,1 =Z g2,1 =Z g3,1 =Z g4,1

[0067] The corresponding positive-sequence fault supplementary network can be obtained using the symmetric component method, such as... Figure 5 As shown. When the system is operating in open loop, the cross-line L1 zone is approximately 0.5Z. L1 When a fault occurs, the equivalent positive sequence impedance Z of the system in the figure is... 1m The positive-sequence component can be measured at device M to determine the result.

[0068]

[0069] When the system power supply side impedance Z S When it is known, the system's equivalent potential is

[0070] E m =U m +I m Z S

[0071] In the formula U m I m To protect the voltage and current at the M installation point.

[0072] When the system is operating in open loop, the fault occurs at approximately 0.75Z across line L1. L When dealing with a positive-sequence fault, an additional network is provided, such as... Figure 6 As shown.

[0073] System equivalent positive sequence impedance Z 1m It can be approximated as the following formula

[0074]

[0075] In summary, the location relationship between the fault point and the protection M, as well as the positive sequence system impedance calculated online, can be summarized in the table below.

[0076] Table 1 Summary of Positive Sequence System Impedances

[0077]

[0078] The zero-sequence overcurrent setting calculation formula is as follows:

[0079]

[0080] In the formula Z is the system's equivalent zero-sequence potential. S0 It is the zero-sequence equivalent system impedance, which varies with the system's operating mode.

[0081] When the system is operating in open loop, and a fault occurs outside the positive zone of protection M, the system's zero-sequence fault supplementary network is as follows: Figure 7 As shown.

[0082] The zero-sequence equivalent system impedance Z at point M in the figure is protected. 0m It can be determined by measuring the zero-sequence component, i.e.

[0083]

[0084] When the system is operating in open loop, the distance within the L1 zone across the line is approximately 0.25Z. L When a fault occurs, the system's zero-sequence fault supplementary network is as follows: Figure 8 As shown in the figure. The zero-sequence equivalent system impedance Z at point M is... 0m It can be determined by measuring the zero-sequence component, i.e.

[0085]

[0086] In summary, the location relationship between the fault point and the protection M, as well as the zero-sequence system impedance calculated online, can be summarized in the table below.

[0087] Table 2 Summary of Zero-Sequence System Impedance

[0088]

[0089] Specific application examples:

[0090] The following section describes the operating conditions and protection settings for the AC dual-power station topology with two generating units per station. See the detailed topology below. Figure 1 A schematic diagram assuming a load-side fault is shown below. Figure 9 .

[0091] When a load failure occurs, such as Figure 9 As shown. After the fault, t DP At that time, the load-side online setting device DP calculates and updates the overcurrent protection setting value of switch CB11 in real time. DP At +Δt, CB11 activates to isolate the fault.

[0092] When troubleshooting loop point faults, such as Figure 10 As shown. At this time, no short-circuit current flows through the load, and the online setting device and overcurrent protection do not activate; other components and the online setting device do not operate due to time delay constraints, and finally t DP After +2ΔT, switches CB5 and CB6 activate to isolate the fault.

[0093] When a cross-line L2 fault occurs, such as Figure 11As shown. At this time, no short-circuit current flows through the load, and the online setting device and overcurrent protection do not activate; fault t DP After +2ΔT, the switches on both sides of the loop breaker point activate, and the system switches to open-loop operation; t DP At +3ΔT, the online setting device DP of the cross-line L2 calculates and updates the overcurrent protection settings of the switches on both sides of the cross-line in real time; t DP At +4ΔT, the switches CB7 and CB8 on both sides of the L2 line operate to isolate the fault.

Claims

1. A real-time protection online setting method suitable for ship closed-loop power grids, characterized in that, Based on the backup protection scheme with a preset loop break point, an online setting device is added to the protection to form an online setting calculation scheme based on the preset loop break point. The online setting device uses a starting element to monitor the fault. When the starting element of the protection detects a fault, it provides a starting signal to the measuring element; otherwise, it will lock the protection. When the starting element detects a fault, the online setting device calculates the equivalent impedance and equivalent potential of the system based on the real-time measured data and automatically updates the setting value.

2. The real-time protection online setting method for ship closed-loop power grids according to claim 1, characterized in that, By monitoring fault conditions through the starting element, if the starting element is triggered, the preset unlooping point is disconnected, the ring network structure is unlooped into an open-loop structure, and the setting value is calculated online according to the system operating status.

3. The real-time protection online setting method for ship closed-loop power grids according to claim 3, characterized in that, The online setting device for load-side protection is set to have a delay of t. DP The online setting device delay for L2 cross-line protection is t. DP +4Δt, where no online setting device is configured at the loop unblocking point, and the online setting device delay of the protection at the bus tie switch is consistent with that of the cross line L2.

4. The real-time protection online setting method for ship closed-loop power grids according to claim 1, characterized in that, The fault monitoring of the starting element adopts the current change in the starting element to monitor phase-to-phase faults and ground faults, including the phase-to-phase current change in the starting element and the zero-sequence current change in the starting element for judgment.

5. The real-time protection online setting method for ship closed-loop power grids according to claim 4, characterized in that, Criteria for starting element based on phase-to-phase current change In the formula This refers to the three phases AB, BC, and CA. K refers to a specific point in the current time of the protection sampling. T = 24 is the number of sampling points per week. KT refers to the value taken from point K one week ago, and K-2T refers to the value taken from point K two weeks ago. QD The starting current setting for phase-to-phase changes can be adjusted to a sensitivity coefficient greater than 1.2 under the condition of satisfying the minimum short-circuit current of the system. The criterion for starting a component with a sudden change in zero-sequence current is Δ3I0 > I. QD0 In the formula, Δ3I0 is the zero-sequence current abrupt change, I QD0 The starting current setting for zero-sequence change can be adjusted to a sensitivity coefficient greater than 1.2 under the condition of satisfying the minimum zero-sequence current of the system.

6. The real-time protection online setting method for ship closed-loop power grids according to claim 1, characterized in that, The formula for calculating phase-to-phase overcurrent setting is as follows: In the formula K is the phase electromotive force of the system's equivalent power source. sen Z is the sensitivity coefficient, which is 1.

2. S This is the equivalent system impedance, which will vary depending on the system's operating mode. Z L This is the impedance of the entire protected crossover line. Since the crossover line impedance is relatively small, this value is ignored.

7. The real-time protection online setting method for ship closed-loop power grids according to claim 6, characterized in that, When a phase-to-phase fault occurs in the system, the system impedance Z in the phase-to-phase overcurrent setting calculation formula is... S The fault supplementary network is obtained by combining the fault component method. Let the direction of the busbar to the cross-line be the positive direction of the current, and M be the protection installation point. The corresponding positive sequence fault supplementary network is obtained by using the symmetrical component method.

8. The real-time protection online setting method for ship closed-loop power grids according to claim 7, characterized in that, When the system is operating in open loop, approximately 0.5Z is located within the L1 zone across the line. L1 When a fault occurs, the system's equivalent positive sequence impedance Z 1m The positive sequence component is obtained by measuring it at device M, i.e. When the system power supply side impedance Z S When it is known, the system's equivalent potential is E m =U m +I m Z S In the formula U m I M To protect the voltage and current at the M installation point. When the system is operating in open loop, the fault occurs at 0.75Z across line L1. L At this time, the equivalent positive-sequence impedance Z of the system in the positive-sequence fault-addition network is... 1m It can be approximated as the following formula The location relationship between the fault point and the protection M, as well as the positive sequence system impedance calculated online, are summarized in the table.

9. The real-time protection online setting method for ship closed-loop power grids according to claim 7, characterized in that, The formula for zero-sequence overcurrent setting is as follows: In the formula Z is the system's equivalent zero-sequence potential. S0 It is the zero-sequence equivalent system impedance, which varies with the system's operating mode.

10. The real-time protection online setting method for ship closed-loop power grids according to claim 7, characterized in that, When the system is operating in open loop and a fault occurs outside the positive zone of protection M, the zero-sequence equivalent system impedance Z at protection M in the zero-sequence fault supplementary network of the system is... 0m It can be determined by measuring the zero-sequence component, i.e. When the system is operating in open loop, the 0.25Z area within the L1 zone of the cross-line... L When a fault occurs, the zero-sequence equivalent system impedance Z at protection M in the zero-sequence fault supplementary network of the system is... 0m It can be determined by measuring the zero-sequence component, i.e. The location relationship between the fault point and the protection M, as well as the zero-sequence system impedance calculated online, are summarized in the table.

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