Active power distribution grid distributed protection system

Abstract

The application provides an active power distribution network distributed protection system, which comprises an in-station switch, a first intelligent terminal, a second intelligent terminal and a third intelligent terminal; wherein the in-station switch is used for tripping after a first quick-break protection time is delayed when a fault of a power distribution network line is monitored, and closing after a first closing time is delayed after tripping; when current communication delay is greater than or equal to a preset time threshold and less than the first delay, the first intelligent terminal is used for tripping if only local fault information is monitored within the first delay and local voltage is zero after the first delay; tripping if there is no local fault information but local voltage is continuously zero within the second delay; the second and third intelligent terminals are both used for tripping if local voltage is zero after the first delay when fault information is monitored. The above system reduces the situation of abnormal locking protection of system communication, and reduces the dependence on unlimited communication delay.

Description

Technical Field

[0001] This invention relates to the field of distributed protection technology, and in particular to an active distributed protection system for power distribution networks. Background Technology

[0002] Intelligent distributed protection, through horizontal information exchange between intelligent terminals, can quickly identify the faulty section and achieve rapid fault isolation by locally tripping the switches on both sides of the faulty section. This method offers accurate fault isolation and rapid power restoration, making it widely used in high-reliability power supply areas. In recent years, with the development of 5G (5th-Generation Mobile Communication Technology), intelligent distributed protection based on 5G wireless communication has been widely applied. However, it has the following shortcomings in practical applications:

[0003] First, the uncertainty of wireless communication affects the correct operation of protection systems. Most intelligent distributed pilot projects based on 5G wireless communication utilize the low latency of 5G. However, in actual operation, the latency of 5G wireless communication varies greatly. If the latency exceeds the set value, the distributed protection will become unusable, frequently causing communication anomaly alarms. This leads to frequent blocking of intelligent distributed protection systems, rendering them ineffective. Summary of the Invention

[0004] In view of this, the present invention provides an active distributed protection system for power distribution networks, which can solve the problem of distributed protection failure caused by changes in wireless communication delay.

[0005] In a first aspect, embodiments of the present invention provide an active distribution network distributed protection system, comprising: an in-station switch, a first intelligent terminal, a second intelligent terminal, and a third intelligent terminal;

[0006] The first intelligent terminal is the first intelligent terminal on the distribution network line outside the substation; the second intelligent terminal is the end intelligent terminal on the distribution network line; the third intelligent terminal is the intelligent terminal on the distribution network line other than the first and second intelligent terminals; adjacent intelligent terminals are connected through remote communication.

[0007] The station switch is used to trip after a delay of the first instantaneous overcurrent protection time when a fault is detected in the distribution network line, and to close the circuit after a delay of the first closing time after tripping.

[0008] When the current communication delay is greater than or equal to a preset time threshold and less than a first delay, the first intelligent terminal is used to trip if only fault information is detected at the local end within the first delay and the local voltage is detected to be zero after the first delay; if there is no fault information at the local end within the second delay but the local voltage remains zero, the terminal trips; the second and third intelligent terminals are both used to trip if the local voltage is detected to be zero after the first delay in which fault information is detected.

[0009] In one possible implementation, the first delay is greater than the first instantaneous overcurrent protection time and less than a target time and value, wherein the target time and value are the sum of the first instantaneous overcurrent protection time and the first closing time; the second delay is greater than the first delay.

[0010] In one possible implementation, the power distribution network includes a main line and branch lines; the system also includes a branch switch; the branch switch is the first intelligent terminal located on the branch line, close to the main line side;

[0011] The first intelligent terminal includes a first intelligent terminal located on the main line and a first intelligent terminal located on a branch line; the first intelligent terminal located on the main line is adjacent to the station switch and is the first intelligent terminal located on the main line; the first intelligent terminal located on the branch line is located on the branch line and is adjacent to the branch switch.

[0012] The second delay includes a first preset time and a second preset time;

[0013] The first intelligent terminal located on the main line is specifically used for:

[0014] If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage on this end is detected to be zero when the first delay timer expires, the circuit breaker will trip.

[0015] If there is no fault information at this end and the voltage at this end is zero, then start the first preset timer. If the voltage at this end is still zero when the first preset timer expires, then trip.

[0016] The first smart terminal located on the branch line is specifically used for:

[0017] If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage on this end is detected to be zero when the first delay timer expires, the circuit breaker will trip.

[0018] If there is no fault information at this end and the voltage at this end is zero, then start the second preset timer. If the voltage at this end is still zero when the second preset timer expires, then trip.

[0019] The second preset time is greater than the first preset time.

[0020] In one possible implementation, the third smart terminal is specifically used for:

[0021] If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage is detected to be zero when the first delay timer expires, the circuit breaker will trip.

[0022] If the current communication delay is greater than or equal to a preset time threshold but less than the first delay, and if there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the first delay timer is started. If the voltage on this end is zero when the first delay timer expires, then the circuit breaker is tripped.

[0023] In one possible implementation, the power distribution network includes a main line and branch lines; the system also includes a branch switch, which is the first intelligent terminal located on the branch line and adjacent to the main line.

[0024] The first intelligent terminal includes a first intelligent terminal located on the main line and a first intelligent terminal located on a branch line; the first intelligent terminal located on the main line is adjacent to the station switch and is the first intelligent terminal located on the main line; the first intelligent terminal located on the branch line is located on the branch line and is adjacent to the branch switch.

[0025] The branch switch is used to trip after a second fast-acting protection time is delayed after detecting a fault in the distribution network line, and to close after a second closing time is delayed after tripping.

[0026] The first intelligent terminal located on the main line is also used for:

[0027] If the current communication delay is less than the preset time threshold, and there is a fault information on the local end, a third delay is started. If no fault information is received from the adjacent smart terminal during the third delay time, the circuit breaker is tripped when the third delay time expires. If there is no fault information on the local end but the local voltage is detected to be zero, a first preset time is started. If the local voltage is still zero when the first preset time expires, the circuit breaker is tripped.

[0028] The first smart terminal located on the branch line is also used for:

[0029] If the current communication delay is less than the preset time threshold, and there is a fault information at this end, a fourth delay is started. If no fault information is received from a neighboring smart terminal during the fourth delay, the circuit breaker will trip when the fourth delay expires. If there is no fault information at this end but the voltage at this end is detected to be zero, a second preset time delay is started. If the voltage at this end is still zero when the second preset time expires, the circuit breaker will trip.

[0030] The third delay is less than the first instantaneous overcurrent protection time and greater than the second instantaneous overcurrent protection time; the second instantaneous overcurrent protection time is less than the first instantaneous overcurrent protection time.

[0031] The fourth delay is less than the second instantaneous overcurrent protection time;

[0032] The second preset time is greater than the first preset time.

[0033] In one possible implementation, the second smart terminal is further used for:

[0034] If a fault exists on the local end when the current communication delay is less than the preset time threshold, the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

[0035] If the current communication delay is less than the preset time threshold, and there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

[0036] In one possible implementation, the third smart terminal is further used for:

[0037] If the current communication delay is less than the preset time threshold, and there is a fault information on the local end, the third delay is started. If no fault information is received from the adjacent smart terminal during the third delay time, the circuit breaker is tripped when the third delay time expires.

[0038] If the current communication delay is less than the preset time threshold, and there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

[0039] In one possible implementation, the first smart terminal, the second smart terminal, and the third smart terminal are respectively further used for:

[0040] If the current communication delay is greater than or equal to the second time threshold, the device is immediately locked.

[0041] In one possible implementation, the system further includes a boundary switch for separating the distribution network side and the user side;

[0042] The sectionalizing switch is used to trip immediately when a fault is detected at this end.

[0043] Secondly, embodiments of the present invention provide an active distribution network distributed protection system, including: an in-station switch, a first intelligent terminal, a second intelligent terminal, a third intelligent terminal, and a tie switch;

[0044] The first intelligent terminal is the first intelligent terminal on the distribution network line outside the substation; the second intelligent terminal is the end intelligent terminal on the distribution network line; the third intelligent terminal is the intelligent terminal on the distribution network line other than the first and second intelligent terminals; adjacent intelligent terminals are connected through remote communication.

[0045] The communication switch is used for:

[0046] When a voltage loss is detected on one side and a switch trip signal is received from at least one smart terminal on the same line, a fifth delay is initiated. If no fault signal is received from the adjacent smart terminal on the side of the voltage loss during the fifth delay, and no switch failure signal is received from any smart terminal on the same line, and the voltage on the side of the voltage loss is still zero when the fifth delay is reached, the circuit breaker is closed.

[0047] The beneficial effects of the embodiments of the present invention compared with the prior art are as follows:

[0048] The active distribution network distributed protection system provided in this invention determines the corresponding processing strategy based on the length of the communication delay and divides the intelligent terminals on the distribution network lines into three categories. When the current communication delay is greater than or equal to a preset time threshold but less than a first delay, the first intelligent terminal trips if it detects only a fault information at its own end within the first delay and then detects that the voltage at its own end is zero after the first delay; if there is no fault information at its own end within the second delay but the voltage at its own end remains zero, it trips. The second and third intelligent terminals both trip when they detect that the voltage at their own end is zero after the first delay in detecting the fault information. The above system ensures the coordination between different switches during fault isolation by setting different delays, clarifies the processing strategy under the corresponding communication delay, and avoids the situation in the prior art where the system blocks protection when the communication delay is greater than the preset time threshold, thereby reducing the dependence on infinite communication delay. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the structure of the active power distribution network distributed protection system provided in the embodiment of the present invention. Detailed Implementation

[0051] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0052] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments will be described below in conjunction with the accompanying drawings.

[0053] refer to Figure 1 This invention provides a schematic diagram of the structure of an active distribution network distributed protection system, including: an in-station switch, a first intelligent terminal, a second intelligent terminal, and a third intelligent terminal;

[0054] The first intelligent terminal is the first intelligent terminal on the distribution network line outside the substation; the second intelligent terminal is the end intelligent terminal on the distribution network line; the third intelligent terminal is the intelligent terminal on the distribution network line other than the first and second intelligent terminals; adjacent intelligent terminals are connected through remote communication.

[0055] The station switch is used to trip after a delay of the first instantaneous overcurrent protection time when a fault is detected in the distribution network line, and to close the circuit after a delay of the first closing time after tripping.

[0056] When the current communication delay is greater than or equal to a preset time threshold and less than a first delay, the first intelligent terminal is used to trip if only fault information is detected at the local end within the first delay and the local voltage is detected to be zero after the first delay; if there is no fault information at the local end within the second delay but the local voltage remains zero, the terminal trips; the second and third intelligent terminals are both used to trip if the local voltage is detected to be zero after the first delay in which fault information is detected.

[0057] In one possible implementation, the first delay is greater than the first instantaneous overcurrent protection time and less than a target time and value, wherein the target time and value are the sum of the first instantaneous overcurrent protection time and the first closing time; the second delay is greater than the first delay.

[0058] In this embodiment, the smart terminal is specifically a smart distributed terminal. Its switch can divide a line into multiple segments, hence it is also called a segmented switch. It is used to monitor the switch status, line current and other power distribution network operation parameters corresponding to the terminal in real time. It can also control the switch when a fault is detected. It is an important actuator for quickly cutting off faults. The smart terminals communicate remotely with each other through 5G wireless communication technology.

[0059] The first intelligent terminal is the first intelligent terminal closest to the substation on a distribution network line outside the substation. The second intelligent terminal is the last intelligent terminal on a distribution network line outside the substation, excluding tie switches and boundary switches. The boundary switches are located between the distribution network side and the user side, used to demarcate the two sides. The third intelligent terminal is any other intelligent terminal on the distribution network line outside the substation besides the first intelligent terminal, the second intelligent terminal, tie switches, and boundary switches. For example... Figure 1 As shown, Figure 1 The diagram illustrates a power distribution network, where the longest horizontal line is the main trunk line, and the two vertical lines are branch lines. On the main trunk line, according to the aforementioned division rules, Main Trunk 1# is the first intelligent switch. Excluding tie switches and boundary switches, the terminal intelligent terminal on the main trunk line is Main Trunk 3#, therefore Main Trunk 3# is the second intelligent terminal, and Main Trunk 2# is the third intelligent terminal. Figure 1 On the branch lines extending downwards, Branch 2# is the first intelligent terminal adjacent to the main line, i.e., a branch switch. This branch switch is equivalent to the substation switch within the main line. Branch line segment 1# is the first intelligent switch adjacent to the branch switch, and is therefore the first intelligent switch. Branch line segment 2# is the end intelligent switch on the branch line excluding the tie switch, and is therefore the second intelligent switch. On another branch line, Branch 1# is a branch switch.

[0060] Classifying smart terminals using the above method allows staff to quickly determine their category based on their installation location during the initial installation phase, and then determine the programs to be loaded based on the category, making it easier for staff to operate.

[0061] In this embodiment, when the intelligent terminal detects that the actual current flowing through its own terminal is greater than the rated current, it sets D to 1; otherwise, it sets D to 0. When the intelligent terminal detects that D = 1 in its own terminal, it determines that there is fault information in its own terminal; otherwise, it determines that there is no fault information in its own terminal. Each intelligent terminal can transmit its own tripping / opening information and fault information to adjacent terminals, and adjacent terminals can transmit the tripping / opening information and fault information received from other intelligent terminals to their adjacent terminals.

[0062] In this embodiment, when the switch in the station detects overcurrent information, it determines that a fault has occurred on the distribution network line corresponding to the substation. Therefore, it trips after a first instantaneous overcurrent protection time and then closes the circuit after a first closing time.

[0063] Specifically, the preset time threshold T0 can be the substation I-stage protection operation time or a set value. When the preset time threshold T0 is a set value, T0 = 50ms, and the substation I-stage protection operation time is a value greater than zero. The first delay T1 is greater than the first instantaneous overcurrent protection time and less than the target time and value, where the target time and value are the sum of the first instantaneous overcurrent protection time and the first closing time. The preset time threshold T0 is less than the first delay T1. The first instantaneous overcurrent protection time corresponding to the switch in the substation is 0.3s, the first closing time is 1.5s, and T1 = 1.5s. The second delay T2 is greater than the first delay T1.

[0064] In this embodiment, when the current communication delay is greater than a preset time threshold but less than a first delay, a fault isolation strategy is adopted. By setting different delay times, each smart terminal can cooperate with each other during fault isolation, making the operation more reliable.

[0065] As can be seen from the above embodiments, the system ensures the coordination between different switches during fault isolation by setting different delays, and clarifies the processing strategy under the corresponding communication delay, thereby reducing the dependence on infinite communication delay. Secondly, after classifying the different smart terminals, this application can quickly locate and isolate faults by setting different delays and tripping conditions for various smart terminals / switches, making it simple to implement and more applicable.

[0066] In one possible implementation, the distribution network line includes a main line and branch lines; the system also includes a branch switch; the branch switch is the first intelligent terminal located on the branch line, close to the main line side;

[0067] The first intelligent terminal includes a first intelligent terminal located on the main line and a first intelligent terminal located on a branch line; the first intelligent terminal located on the main line is adjacent to the station switch and is the first intelligent terminal located on the main line; the first intelligent terminal located on the branch line is located on the branch line and is adjacent to the branch switch.

[0068] The second delay includes a first preset time and a second preset time;

[0069] The first intelligent terminal located on the main line is specifically used for:

[0070] If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage on this end is detected to be zero when the first delay timer expires, the circuit breaker will trip.

[0071] If there is no fault information at this end and the voltage at this end is zero, then start the first preset timer. If the voltage at this end is still zero when the first preset timer expires, then trip.

[0072] The first smart terminal located on the branch line is specifically used for:

[0073] If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage on this end is detected to be zero when the first delay timer expires, the circuit breaker will trip.

[0074] If there is no fault information at this end and the voltage at this end is zero, then start the second preset timer. If the voltage at this end is still zero when the second preset timer expires, then trip.

[0075] The second preset time is greater than the first preset time.

[0076] In this embodiment, the first preset time T2′ can be 10s, and the second preset time T2″ can be 25s.

[0077] In this embodiment, when the current communication delay is greater than or equal to a preset time threshold and less than a first delay, the first intelligent terminal located on the main line / the first intelligent terminal located on the branch line, upon detecting that its local voltage D=1, immediately initiates the first delay T1. Within T1, if no fault information is received from any of the adjacent intelligent terminals, the circuit breaker trips when the first delay T1 arrives and the local voltage is detected to be zero. If fault information is received from an adjacent intelligent terminal, the circuit breaker remains closed. If the first intelligent terminal located on the main line detects that its local voltage D=0 (i.e., no fault information) and collects that its local voltage is zero, it initiates a first preset time T2′ delay. After T2′ arrives, if the local voltage is still zero, the circuit breaker trips. If the first intelligent terminal located on the branch line detects that its local voltage D=0 (i.e., no fault information) and collects that its local voltage is zero, it initiates a second preset time T2″ delay. After T2″ arrives, if the local voltage is still zero, the circuit breaker trips.

[0078] In one possible implementation, the second smart terminal is used for:

[0079] If the current communication delay is greater than or equal to a preset time threshold but less than the first delay, and if there is a fault information on this end or a fault information sent by a neighboring smart terminal is received, the first delay timer is started. If the voltage on this end is zero when the first delay timer expires, the circuit breaker is tripped.

[0080] In this embodiment, if the current communication delay of the second smart terminal is greater than or equal to a preset time threshold and less than the first delay, and there is no fault information in either the local or adjacent smart terminals, then the power is kept on.

[0081] The above method for the second intelligent terminal can be applied to both trunk lines and branch lines.

[0082] In one possible implementation, the third smart terminal is specifically used for:

[0083] If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage is detected to be zero when the first delay timer expires, the circuit breaker will trip.

[0084] If the current communication delay is greater than or equal to a preset time threshold but less than the first delay, and if there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the first delay timer is started. If the voltage on this end is zero when the first delay timer expires, then the circuit breaker is tripped.

[0085] In this embodiment, when the current communication delay is greater than or equal to a preset time threshold and less than the first delay, if the third intelligent terminal detects fault information at its own end and detects fault information sent by the adjacent intelligent terminal during the first delay timer, or if neither its own end nor the adjacent intelligent terminal detects fault information, then the closed state is maintained.

[0086] Specifically, previous intelligent distributed systems based on 5G wireless communication were mostly applicable to cable lines, but traditional methods are no longer suitable for complex overhead lines with multiple branches. Some solutions, to adapt to multi-branch power supply networks, adopt multi-terminal communication distributed protection schemes, incorporating branch switches into the intelligent distributed system. This method involves many terminals, complex logic, and an extremely high failure rate, resulting in low safety during operation and maintenance, and high equipment costs. Furthermore, in complex overhead line structures, there are often branch switches between the terminal distributed switches and tie switches. After a power outage due to a fault, traditional methods do not consider the impact of branch faults on power restoration, often causing incorrect tie-switching operations.

[0087] This embodiment designs different control strategies for intelligent terminals, station switches, connecting switches, and boundary switches located at different positions on the line. When the communication delay between intelligent terminals is greater than or equal to a preset time threshold but less than a first delay, a slow-motion protection strategy is adopted through the coordinated actions of the station switches, the first, second, and third intelligent terminals. This allows the fault to be cleared by the station switches, branch switches, and boundary switches, and the fault to be isolated by the intelligent terminals. This avoids the problem of low system security caused by malfunctions and improves the security of distributed protection.

[0088] In one possible implementation, when the current communication delay is less than the preset time threshold, this embodiment adopts a fast-acting strategy, mainly used for fault clearing and isolation. Specifically, the distribution network line includes a main line and branch lines; the system also includes a branch switch, which is the first intelligent terminal located on the branch line and adjacent to the main line.

[0089] The first intelligent terminal includes a first intelligent terminal located on the main line and a first intelligent terminal located on a branch line; the first intelligent terminal located on the main line is adjacent to the station switch and is the first intelligent terminal located on the main line; the first intelligent terminal located on the branch line is located on the branch line and is adjacent to the branch switch.

[0090] The branch switch is used to trip after a second fast-acting protection time is delayed after detecting a fault in the distribution network line, and to close after a second closing time is delayed after tripping.

[0091] The first intelligent terminal located on the main line is also used for:

[0092] If the current communication delay is less than the preset time threshold, and there is a fault information on the local end, a third delay is started. If no fault information is received from the adjacent smart terminal during the third delay time, the circuit breaker is tripped when the third delay time expires. If there is no fault information on the local end but the local voltage is detected to be zero, a first preset time is started. If the local voltage is still zero when the first preset time expires, the circuit breaker is tripped.

[0093] The first smart terminal located on the branch line is also used for:

[0094] If the current communication delay is less than the preset time threshold, and there is a fault information at this end, a fourth delay is started. If no fault information is received from a neighboring smart terminal during the fourth delay, the circuit breaker will trip when the fourth delay expires. If there is no fault information at this end but the voltage at this end is detected to be zero, a second preset time delay is started. If the voltage at this end is still zero when the second preset time expires, the circuit breaker will trip.

[0095] The third delay is less than the first instantaneous overcurrent protection time and greater than the second instantaneous overcurrent protection time; the second instantaneous overcurrent protection time is less than the first instantaneous overcurrent protection time.

[0096] The fourth delay is less than the second instantaneous overcurrent protection time;

[0097] The second preset time is greater than the first preset time.

[0098] In one possible implementation, the system further includes a boundary switch for separating the distribution network side and the user side;

[0099] The sectionalizing switch is used to trip immediately when a fault is detected at this end.

[0100] Specifically, the speed protection time of the sectionalizing switch is zero.

[0101] In this embodiment, the third delay can be the sum of the current communication delay and 50ms. The fourth delay is the third delay minus the target level difference, where the target level difference is the time difference between the first instantaneous overcurrent protection time and the second instantaneous overcurrent protection time.

[0102] In one possible implementation, the second smart terminal is further used for:

[0103] If a fault exists on the local end when the current communication delay is less than the preset time threshold, the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

[0104] If the current communication delay is less than the preset time threshold, and there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

[0105] In one possible implementation, the third smart terminal is further used for:

[0106] If the current communication delay is less than the preset time threshold, and there is a fault information on the local end, the third delay is started. If no fault information is received from the adjacent smart terminal during the third delay time, the circuit breaker is tripped when the third delay time expires.

[0107] If the current communication delay is less than the preset time threshold, and there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

[0108] In one possible implementation, the first smart terminal, the second smart terminal, and the third smart terminal are respectively further used for:

[0109] If the current communication delay is greater than or equal to the second time threshold, the device is immediately locked.

[0110] In this embodiment, when the communication delay between smart terminals is greater than or equal to the second time threshold, or when the horizontal communication is interrupted, the first smart terminal, the second smart terminal, and the third smart terminal are distributed protection interlocked, and overcurrent protection is activated.

[0111] As can be seen from the above embodiments, this embodiment proposes an intelligent distributed solution under different delays through multi-level delay design, which reduces the system's dependence on wireless communication delay and can meet the usage requirements of most fields.

[0112] Secondly, embodiments of the present invention provide an active distribution network distributed protection system, including: an in-station switch, a first intelligent terminal, a second intelligent terminal, a third intelligent terminal, and a tie switch;

[0113] The first intelligent terminal is the first intelligent terminal on the distribution network line outside the substation; the second intelligent terminal is the end intelligent terminal on the distribution network line; the third intelligent terminal is the intelligent terminal on the distribution network line other than the first and second intelligent terminals; adjacent intelligent terminals are connected through remote communication.

[0114] The communication switch is used for:

[0115] When a voltage loss is detected on one side and a switch trip signal is received from at least one smart terminal on the same line, a fifth delay is initiated. If no fault signal is received from the adjacent smart terminal on the side of the voltage loss during the fifth delay, and no switch failure signal is received from any smart terminal on the same line, and the voltage on the side of the voltage loss is still zero when the fifth delay is reached, the circuit breaker is closed.

[0116] In this embodiment, based on the fault isolation scheme of the active distribution network distributed protection system provided in the first aspect above, fault recovery is performed through delay design, realizing system self-healing. Specifically, the fifth delay is the difference between the second preset time and the first preset time, and the fifth delay is greater than the first preset time. For example, the fifth delay can be 15 to 30 seconds.

[0117] As can be seen from the above embodiments, this embodiment considers the recovery problem of different fault locations under complex grid structures, and ensures the coordination of fault isolation and self-healing through delay design. The size and relationship of the delay are specified, and the delay coordination is adopted, abandoning the power-on reconnection method, which greatly improves the safety.

[0118] This embodiment provides a specific example, wherein the preset time threshold is 50ms, the first delay T1 = 1.5s, the first preset time T2′ = 10s, the second preset time T2″ = 25s, the third delay T3 = 250ms, the fourth delay T4 = 100ms, the fifth delay T5 = 15s, the first instantaneous overcurrent protection time is 0.3s, the first closing time is 15s, the second instantaneous overcurrent protection time is 0.15s, and the second closing time is 1.5s.

[0119] Table 1

[0120]

[0121] refer to Figure 1 When the faults occur respectively Figure 1 When F1, F2, F3, F4, F5, F6, F7, F8, and F9 are selected, if the current communication delay T < 50ms, the processing strategies for substation switches, smart terminals, tie switches, branch switches, and boundary switches in the distribution network line are shown in Table 1.

[0122] If the current communication delay is 50ms≤T<1.5s, the processing strategies for substation switches, smart terminals, tie switches, branch switches, and boundary switches in the distribution network are shown in Table 2.

[0123] Table 2

[0124]

[0125] When T≥1.5s, the distribution network line performs conventional overcurrent protection.

[0126] As can be seen from the above embodiments, the active distribution network distributed protection system provided in this application is not only applicable to main lines, which can adopt a three-level coordination of "instantaneous overcurrent protection of in-station switches - intelligent distributed protection of sectionalizing switches - instantaneous overcurrent protection of branch switches", but also applicable to long branch lines, which can adopt a three-level coordination of "instantaneous overcurrent protection of the first branch switch + intelligent distributed protection of sectionalizing switches on the branch line + instantaneous overcurrent protection of the boundary switch", forming a five-level coordination mode of "instantaneous overcurrent protection of in-station switches - intelligent distributed protection of sectionalizing switches - instantaneous overcurrent protection of branch switches + intelligent distributed protection of sectionalizing switches on the branch line + instantaneous overcurrent protection of boundary switches". Considering the coordination with reclosing of in-station switches and branch switches and the coordination with instantaneous overcurrent protection, the distributed protection is interspersed between differential protection, forming a fault handling mode of "differential protection + intelligent distributed", which improves the adaptability with existing protection, is simple to implement, and has stronger applicability.

[0127] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An active distributed protection system for power distribution networks, characterized in that, This includes station switches, a first intelligent terminal, a second intelligent terminal, and a third intelligent terminal; The first intelligent terminal is the first intelligent terminal on the external distribution network line of the substation; The second intelligent terminal is the end-point intelligent terminal on the power distribution network line; The third intelligent terminal is an intelligent terminal on the distribution network line other than the first and second intelligent terminals; adjacent intelligent terminals are connected through remote communication. The station switch is used to trip after a first instantaneous overcurrent protection time when a fault is detected in the distribution network line, and to close after a first closing time after tripping. When the current communication delay is greater than or equal to a preset time threshold but less than the first delay, the first intelligent terminal is used to trip if only fault information is detected at its own end within the first delay and the voltage at its own end is zero after the first delay; and trip if no fault information is detected at its own end within the second delay but the voltage at its own end remains zero. The second and third intelligent terminals are both used to trip when the voltage at its own end is zero after the first delay in detecting fault information. The first delay is greater than the first instantaneous overcurrent protection time but less than a target time and value, where the target time and value are the sum of the first instantaneous overcurrent protection time and the first closing time. The second delay is greater than the first delay.

2. The active distribution network distributed protection system according to claim 1, characterized in that, The power distribution network includes main lines and branch lines; the system also includes branch switches; the branch switch is the first intelligent terminal located on the branch line, close to the main line side; The first intelligent terminal includes a first intelligent terminal located on the main line and a first intelligent terminal located on the branch line; The first intelligent terminal located on the main line is the first intelligent terminal located on the main line adjacent to the switch in the station. The first intelligent terminal located on the branch line is an intelligent terminal located on the branch line and adjacent to the branch switch; The second delay includes a first preset time and a second preset time; The first intelligent terminal located on the main line is specifically used for: If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage on this end is detected to be zero when the first delay timer expires, the circuit breaker will trip. If there is no fault information at this end and the voltage at this end is zero, then start the first preset timer. If the voltage at this end is still zero when the first preset timer expires, then trip. The first smart terminal located on the branch line is specifically used for: If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage on this end is detected to be zero when the first delay timer expires, the circuit breaker will trip. If there is no fault information at this end and the voltage at this end is zero, then start the second preset timer. If the voltage at this end is still zero when the second preset timer expires, then trip. The second preset time is greater than the first preset time.

3. The active distribution network distributed protection system according to claim 1, characterized in that, The third smart terminal is specifically used for: If the current communication delay is greater than or equal to a preset time threshold and less than the first delay, and there is a fault information on this end, the first delay timer will be started. If no fault information is received from the adjacent smart terminal during the first delay timer, and the voltage is detected to be zero when the first delay timer expires, the circuit breaker will trip. If the current communication delay is greater than or equal to a preset time threshold but less than the first delay, and if there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the first delay timer is started. If the voltage on this end is zero when the first delay timer expires, then the circuit breaker is tripped.

4. The active distribution network distributed protection system according to claim 1, characterized in that, The power distribution network includes main lines and branch lines; the system also includes a branch switch, which is the first intelligent terminal located on the branch line and adjacent to the main line. The first intelligent terminal includes a first intelligent terminal located on the main line and a first intelligent terminal located on the branch line; The first intelligent terminal located on the main line is the first intelligent terminal located on the main line adjacent to the switch in the station. The first intelligent terminal located on the branch line is an intelligent terminal located on the branch line and adjacent to the branch switch; The branch switch is used to trip after a second fast-acting protection time is delayed after detecting a fault in the distribution network line, and to close after a second closing time is delayed after tripping. The first intelligent terminal located on the main line is also used for: If the current communication delay is less than the preset time threshold, and there is a fault information on the local end, a third delay is started. If no fault information is received from the adjacent smart terminal during the third delay time, the circuit breaker is tripped when the third delay time expires. If there is no fault information on the local end but the local voltage is detected to be zero, a first preset time is started. If the local voltage is still zero when the first preset time expires, the circuit breaker is tripped. The first smart terminal located on the branch line is also used for: If the current communication delay is less than the preset time threshold, and there is a fault information at this end, a fourth delay is started. If no fault information is received from a neighboring smart terminal during the fourth delay, the circuit breaker will trip when the fourth delay expires. If there is no fault information at this end but the voltage at this end is detected to be zero, a second preset time delay is started. If the voltage at this end is still zero when the second preset time expires, the circuit breaker will trip. The third delay is less than the first instantaneous overcurrent protection time and greater than the second instantaneous overcurrent protection time; The second instantaneous overcurrent protection time is shorter than the first instantaneous overcurrent protection time; The fourth delay is less than the second instantaneous overcurrent protection time; The second preset time is greater than the first preset time.

5. The active distribution network distributed protection system according to claim 4, characterized in that, The second smart terminal is also used for: If a fault exists on the local end when the current communication delay is less than the preset time threshold, the third delay is initiated, and the circuit breaker trips when the third delay timer expires. If the current communication delay is less than the preset time threshold, and there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

6. The active distribution network distributed protection system according to claim 4, characterized in that, The third smart terminal is also used for: If the current communication delay is less than the preset time threshold, and there is a fault information on the local end, the third delay is started. If no fault information is received from the adjacent smart terminal during the third delay time, the circuit breaker is tripped when the third delay time expires. If the current communication delay is less than the preset time threshold, and there is no fault information on this end but a fault information is received from a neighboring smart terminal, then the third delay is initiated, and the circuit breaker trips when the third delay timer expires.

7. The active distribution network distributed protection system according to any one of claims 1 to 6, characterized in that, The system also includes a boundary switch for separating the distribution network side and the user side; The sectionalizing switch is used to trip immediately when a fault is detected at this end.

8. The active distribution network distributed protection system according to any one of claims 1 to 6, characterized in that, The first smart terminal, the second smart terminal, and the third smart terminal are respectively used for: If the current communication delay is greater than or equal to the second time threshold, the device is immediately locked.

9. An active distribution network distributed protection system, characterized in that, include: Station switches, first intelligent terminal, second intelligent terminal, third intelligent terminal and communication switch; The first intelligent terminal is the first intelligent terminal on the external distribution network line of the substation; The second intelligent terminal is the end-point intelligent terminal on the power distribution network line; The third intelligent terminal is any intelligent terminal on the power distribution network line other than the first and second intelligent terminals; adjacent intelligent terminals are connected via remote communication. The communication switch enables remote communication with the adjacent second smart terminal; The station switch is used to trip after a first instantaneous overcurrent protection time when a fault is detected in the distribution network line, and to close after a first closing time after tripping; when the current communication delay is greater than or equal to a preset time threshold and less than the first delay, the first intelligent terminal is used to trip if only fault information is detected at its own end within the first delay and the voltage at its own end is zero after the first delay; if there is no fault information at its own end within the second delay but the voltage at its own end remains zero, it will trip; the second intelligent terminal and the third intelligent terminal are both used to trip when the voltage at their own end is zero after the first delay in detecting fault information; the first delay is greater than the first instantaneous overcurrent protection time and less than a target time and value, the target time and value being the sum of the first instantaneous overcurrent protection time and the first closing time; the second delay is greater than the first delay; The communication switch is used for: When a voltage loss is detected on one side and a switch trip signal is received from at least one smart terminal on the same line, the fifth delay is initiated. If no fault signal is received from the adjacent smart terminal on the side of the voltage loss during the fifth delay, and no switch failure signal is received from any smart terminal on the same line, and the voltage on the side of the voltage loss is still zero when the fifth delay is reached, the circuit is closed. The fifth delay is the difference between the second preset time and the first preset time, and the fifth delay is greater than the first preset time.

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