A ring network line protection method and device based on a closed loop operation condition

Abstract

The embodiment of the present application relates to a loop network line protection method and device based on a loop operation condition, the method comprising: judging whether an overcurrent fault exists in a node switch, if the overcurrent fault exists, then executing the next step; judging whether an action condition exists in a first switch, if the action condition exists, then the first switch acts; judging whether an action condition exists in a main switch, if the action condition exists, then the main switch acts. The technical scheme provided by the embodiment of the present application solves the problem that when a short circuit or a ground fault occurs during double power supply loop operation, the fault section is effectively judged in combination with conventional distributed intelligent logic, and the fault area is effectively isolated.

Description

Technical Field

[0001] This invention relates to the field of power system fault protection technology, and in particular to a method and device for protecting ring network lines under closed-loop operation conditions. Background Technology

[0002] In power systems, distribution networks directly face the user end. In recent years, the large-scale integration of distributed energy resources (DERs) into distribution networks has transformed them into active networks with bidirectional energy flow. This has increased the volatility of power flow and voltage, posing new challenges to the protection, control, and operation and maintenance management of distribution networks. Among these solutions, intelligent distributed feeder automation (FA) relies on peer-to-peer communication networks and the mutual communication and cooperation of intelligent feeder terminal devices at various distribution switches to achieve fault location, fault isolation, and power restoration within tens of seconds. GOOSE, or General Object-Oriented Substation Events, allows intelligent feeder terminals to collect information in just tens of milliseconds and is currently widely used in intelligent distributed FA.

[0003] Currently, fault detection for intelligent distributed FA ring network lines typically employs a non-directional three-stage current protection method. This protection method is only applicable to single-side power supply lines and cannot solve the problem of directional protection when dual power supply loops are in operation. Summary of the Invention

[0004] Based on the above-mentioned situation of the prior art, the purpose of this invention is to provide a ring network line protection method and device based on closed-loop operation conditions, which solves the problem that when a short circuit or grounding fault occurs during dual-power closed-loop operation, the fault section can be effectively identified by combining conventional distributed intelligent logic, and the fault area can be effectively isolated.

[0005] To achieve the above objectives, according to one aspect of the present invention, a method for protecting a ring network line under closed-loop operation conditions is provided. The ring network line includes at least one primary switch and multiple main switches. The primary switch is a switch connected at one end to a substation, and the main switches are switches located on the main line of the ring network other than the primary switch. The protection method includes:

[0006] Determine if there is an overcurrent fault in this node switch. If an overcurrent fault exists, proceed to the next step.

[0007] Determine if the first switch has an activation condition; if so, activate the first switch.

[0008] Determine if the main switch has the operating condition; if so, the main switch will operate.

[0009] Furthermore, it also includes:

[0010] Set an action delay for the first switch and the main switch.

[0011] Furthermore, an overcurrent fault is determined to exist in this node switch based on the following conditions:

[0012] When GOOSE communication is normal, the line current exceeds the preset value and the fault confirmation time is exceeded, and the fault component is in the positive direction;

[0013] When GOOSE communication is abnormal, the line current exceeds the preset value and the fault confirmation time is exceeded.

[0014] Furthermore, the conditions for the first switch to operate include:

[0015] The fault component of the overcurrent fault is positive and no fault information is received from adjacent nodes; or,

[0016] The fault component of the overcurrent fault is in the negative direction.

[0017] Furthermore, the operating conditions of the main switch include:

[0018] When this node detects a fault, and receives a fault message from only one of the nodes, the main switch upstream of that faulty node is faulty.

[0019] When this node does not detect any fault information, and receives fault information from only one node on either side of this node, the main switch downstream of that faulty node is faulty.

[0020] According to another aspect of the present invention, a ring network line protection device based on closed-loop operation conditions is provided, wherein the ring network line includes at least one primary switch and multiple main switches, the primary switch being a switch connected at one end to a substation, and the main switches being switches located on the main line of the ring network other than the primary switch; the protection device includes:

[0021] The node overcurrent fault detection module is used to determine whether there is an overcurrent fault in the switch of this node. If there is an overcurrent fault, the next step is executed.

[0022] The first switch fault judgment module is used to determine whether the first switch has an operating condition. If it does, the first switch will operate.

[0023] The main switch fault diagnosis module is used to determine whether the main switch has an operating condition. If it does, the main switch will operate.

[0024] Furthermore, it also includes:

[0025] The delay setting module is used to set the action delay for the first switch and the main switch.

[0026] Furthermore, the node overcurrent fault detection module determines whether an overcurrent fault exists in the node switch based on the following conditions:

[0027] When GOOSE communication is normal, the line current exceeds the preset value and the fault confirmation time is exceeded, and the fault component is in the positive direction;

[0028] When GOOSE communication is abnormal, the line current exceeds the preset value and the fault confirmation time is exceeded.

[0029] Furthermore, the conditions for the first switch to operate include:

[0030] The fault component of the overcurrent fault is positive and no fault information is received from adjacent nodes; or,

[0031] The fault component of the overcurrent fault is in the negative direction.

[0032] Furthermore, the operating conditions of the main switch include:

[0033] When this node detects a fault, and receives a fault message from only one of the nodes, the main switch upstream of that faulty node is faulty.

[0034] When this node does not detect any fault information, and receives fault information from only one node on either side of this node, the main switch downstream of that faulty node is faulty.

[0035] In summary, this invention provides a method and apparatus for protecting ring network lines under closed-loop operation conditions. The method includes: determining whether an overcurrent fault exists at the current node switch; if an overcurrent fault exists, proceeding to the next step; determining whether the first switch has an operating condition; if so, the first switch operates; and determining whether the main switch has an operating condition; if so, the main switch operates. The technical solution provided by this invention, by considering the set value, delay, and direction of the fault component of the line fault to determine the fault section, solves the problem of effectively identifying the fault section and achieving effective isolation of the fault area when a short circuit or ground fault occurs during dual-power closed-loop operation, combined with conventional distributed intelligent logic. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of a typical single-ring network line structure;

[0037] Figure 2 This is a schematic diagram of the line structure when a line in a single-ring network experiences a fault.

[0038] Figure 3 This is a schematic diagram of a single-shot circuit without direction.

[0039] Figure 4 This is a schematic diagram of a directional single-ring network.

[0040] Figure 5 This is a principle vector diagram of a 90° associated directional element;

[0041] Figure 6 This is a schematic diagram of a ring network provided in an embodiment of the present invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0043] Fault handling logic for typical single-ring network distributed FA

[0044] Figure 1 The diagram shows a typical single-ring network circuit structure. Figure 1 In this circuit, 1#-601, 1#-602, 2#-601, and 2#-602 are main line switches; 1#-601 is the first switch; 2#-602 is the tie switch; and 1#-F1 is the branch line switch. The input virtual terminals include:

[0045] Three signals from four adjacent controllers on the main trunk: node fault, adjacent switch fails to trip, and fault isolation is successful;

[0046] Two signals for a branch boundary controller: adjacent switch failure to trip and overcurrent blocking isolation.

[0047] Node fault signals are used to distinguish faulty sections. Adjacent-side switch failure-to-trip signals are used to disconnect and isolate backup protection in case of fault failure. Fault isolation success signals are used to notify the contact switch to close and restore power supply after isolating the faulty area. Overcurrent blocking isolation is exclusive to branch boundary switches; when a branch switch experiences overcurrent, the main switch is blocked from receiving false tripping signals from only one side of the fault. Specific GOOSE input virtual terminal definitions are shown in Table 1.

[0048] Table 1 Definition of GOOSE Input Virtual Terminals

[0049]

[0050]

[0051] Each controller outputs the same four signals, and the names of the virtual terminals of the G00SE output are shown in Table 2.

[0052] Table 2 G00SE Output Virtual Terminal Names

[0053] 1 Node failure reported 2 Fault isolation successfully enabled 3 Switch fails to trip 4 Overcurrent blocking isolation exit

[0054] Figure 2 The diagram shows a schematic of the line structure when a fault occurs in the aforementioned single-ring network.

[0055] When K1 fails, CB1 trips, the line loses power, the No. 1 601 main switch trips due to undervoltage, and the fault is isolated.

[0056] When K2 fails, switches 1#601 and 1#F1 detect the fault current. Switch 1#601 triggers "Fault at this node", with the corresponding output virtual terminal name "Node Fault Output", transmitting "Node Fault Signal" to both sides. Switch 1#602 receives "M-side Node Fault Signal". Switch 1#F1 triggers "Lockout at this node", with the corresponding output virtual terminal name "Overcurrent Lockout Isolation Output". Switch F1 performs fault clearing action, transmitting "Overcurrent Lockout Signal" to both sides. Switches 1#601 and 1#602 do not operate upon receiving the "Overcurrent Lockout Isolation Signal".

[0057] When K3 fails, switches 1#601 and 1#602 detect the fault and trigger "Fault in this node". The corresponding output virtual terminal name is "Node Fault Output", and "Node Fault Signal" is transmitted to both sides respectively. Switch 1#601 does not operate when it receives the node fault signal from the N side, while switch 1#602 operates to clear the fault when it receives the node fault signal from the M side. Switch 2#601 does not detect the fault but receives the node fault signal from the M side and performs fault isolation. After successful operation (segmentation and no current), it sends out a "Fault Isolation Successful Signal", with the corresponding output virtual terminal name "Fault Isolation Successful Output". Switch 2#602 receives the "M-side Fault Isolation Successful" signal. Due to the tie switch and single-sided voltage loss, the power supply is switched after the delay time.

[0058] Non-directional three-stage current protection is only applicable to single-side power supply lines and cannot solve the problem of directional protection when dual power supply loops are running. Figure 3 The diagram shows a schematic of a non-directional single-shot line, such as... Figure 3 As shown, for example, when a short-circuit fault occurs at point K in a single-sided power supply line, the actual direction of the short-circuit current is from the power source to the short-circuit point, that is, from the busbar to the line. Without needing to determine the current direction, the fault area can be identified and fault isolation completed using existing technical solutions. To address the above problems, the purpose of this invention is to provide a ring network line protection method and device based on closed-loop operation conditions to solve the fault detection problem of lines during closed-loop operation. Figure 4 The diagram shows a directional single-ring network. For example, if a fault occurs at point k1, if I... k1 >I set.2 If QF2 malfunctions, then I will malfunction; k2 >I set.5 If the circuit is short-circuited in the opposite direction, the QF5 may malfunction; it may also malfunction when short-circuited in the opposite direction.

[0059] The technical solutions of the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The embodiments of the present invention provide a ring network line protection method based on closed-loop operation conditions. By combining the fault direction determined by the directional element with the conventional distributed FA processing logic, the method effectively identifies the fault section when a short circuit or ground fault occurs during closed-loop operation. The directional element can determine the direction of the fault by judging the phase relationship between the current and voltage, and here a 90° correlation method is used. A (I B ,I C ), U BC (U CA U AB This addresses the issue of directional element malfunction in the 0° connection mode under conditions such as a three-phase short circuit at the positive output, a two-phase-to-ground short circuit (AB or CA), or a phase-to-ground short circuit (A-phase). The 90° connection mode eliminates dead zones for all phase-to-phase short-circuit faults and guarantees directionality for all types of short-circuit faults. Furthermore, the 90° connection mode ensures that when a three-phase short circuit occurs at the protection device output, the line voltage U... AB U BC U CA When the voltage is 0V, the power directional element cannot make an accurate judgment. For situations where there is a judgment dead zone due to a three-phase short circuit at the outlet, the line voltage (memory voltage) before the fault and the short-circuit current after the fault are used for directional judgment. The principle vector diagram of the 90° associated directional element is shown below. Figure 5 As shown, there are two equations of motion:

[0060]

[0061]

[0062] Where α=-φ sen For the interior angle of the direction element, To incorporate the angle between the voltage and current of the directional element, φ sen For the maximum sensitivity angle, φ sen =φ k -90°, φ k The short-circuit impedance angle is usually selected as 60° or 45°.

[0063] The ring network line described in this embodiment of the invention includes at least one primary switch and multiple main switches. The primary switch is a switch connected to a substation at one end, and the main switches are the switches on the main line of the ring network excluding the primary switch. A distributed intelligent logic protection scheme based on closed-loop operation conditions is illustrated using a petal-shaped network structure on the left. Figure 6Taking the ring network line shown in the figure as an example, the possible fault points of the line are shown in the figure. The main ring network adopts a fast-acting intelligent distributed processing strategy based on optical fiber communication. Since it is a closed-loop operation, the condition for judging whether there is an overcurrent fault in this node and sending fault information to the adjacent switch is that the line current is greater than the overcurrent setting value and the fault component is in the positive direction. The positive direction is defined as the current flowing from a certain outlet circuit breaker of the bus to the line. When... Figure 6 As shown, the direction of current flow from the substation to the line is defined as the positive direction, and the direction of current flow from the line to the substation is defined as the negative direction. For example... Figure 6 The fault points F1 and F2 are as follows: when F1 fails, the current flowing through switch 101 of cabinet #1 flows from the line to the substation; when F2 fails, the current flowing through switch 101 of cabinet #1 flows from the substation to the line. During normal operation, all switches are in the closed position, and the line is energized. In the network structure, switches 110 of ring main unit #1 and switch 110 of ring main unit #3 are the primary switches, and the remaining switches are main switches. The operating delay of the two primary switches is set longer than that of the other switches.

[0064] The protection method provided in this embodiment of the invention includes the following steps:

[0065] S1. Determine if there is an overcurrent fault in the switch of this node. If so, proceed to the next step. After the distributed logic direction element is engaged, under normal GOOSE communication conditions, the following conditions must be met simultaneously to determine if there is an overcurrent fault in the switch of this node:

[0066] (1) The line current was detected to exceed the set value and the fault confirmation time was exceeded;

[0067] (2) The fault component detected is in the positive direction.

[0068] In the event of a GOOSE communication anomaly, the condition for determining whether there is an overcurrent fault in the switch of this node is: the line current is detected to exceed a set value and the fault confirmation time has been exceeded.

[0069] S2. Determine if the first switch has an activation condition. If it does, then the first switch activates. The activation condition for the first switch is:

[0070] (1) If an overcurrent is detected and the direction is positive, the circuit breaker will trip if no fault information is received from the adjacent side.

[0071] (2) If an overcurrent is detected and the direction is negative, the circuit breaker will trip.

[0072] S3. Determine if the main switch has the operating conditions. If it does, the main switch will operate. Under the above conditions, the operating conditions for the main switches of the line, excluding the first switch, are:

[0073] The conditions that must be met for the upstream switch to disconnect the fault are:

[0074] (1) The fault information was detected by itself;

[0075] (2) Fault information is received from one side only.

[0076] The conditions that must be met for a downstream switch to isolate a fault are:

[0077] (1) No fault information was detected by itself;

[0078] (2) Fault information is received from one node on one side only.

[0079] Table 3 shows the... Figure 6 The circuit diagram shown is an example of a test scheme under normal GOOSE communication conditions.

[0080] Table 3 Test plan under normal GOOSE communication conditions

[0081]

[0082]

[0083] An embodiment of the present invention also provides a ring network line protection device based on closed-loop operation conditions. The ring network line includes at least one primary switch and multiple main switches. The primary switch is a switch connected to a substation at one end, and the main switches are switches located on the main line of the ring network other than the primary switch. The protection device includes:

[0084] The node overcurrent fault detection module is used to determine whether there is an overcurrent fault in the switch of this node. If there is an overcurrent fault, the next step is executed.

[0085] The first switch fault judgment module is used to determine whether the first switch has an operating condition. If it does, the first switch will operate.

[0086] The main switch fault diagnosis module is used to determine whether the main switch has an operating condition. If it does, the main switch will operate.

[0087] The process by which each module in the ring network line protection device under closed-loop operation conditions in this embodiment of the invention realizes its function is the same as the steps in the ring network line protection method under closed-loop operation conditions in the above embodiment, and will not be repeated here.

[0088] In summary, this invention relates to a method and device for protecting ring network lines under closed-loop operation conditions. The method includes: determining whether an overcurrent fault exists at the current node switch; if an overcurrent fault exists, proceeding to the next step; determining whether the first switch has an operating condition; if so, the first switch operates; and determining whether the main switch has an operating condition; if so, the main switch operates. The technical solution provided by this invention converts the hardware principle of power relays into a software algorithm and applies it to actual field engineering. During closed-loop operation, current flows on both sides of the fault point. Direction, setpoint, and delay are used to ensure the correct operation of switches on both sides of the fault. By considering the setpoint, delay, and direction of the fault component in the line fault for fault section determination, this method effectively identifies the fault section and achieves effective isolation of the fault area when a short circuit or ground fault occurs during dual-power closed-loop operation, combined with conventional distributed intelligent logic.

[0089] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for protecting ring network lines under closed-loop operation conditions, characterized in that, The ring network line includes at least one primary switch and multiple main switches. The primary switch is a switch connected to a substation at one end, and the main switches are switches on the main line of the ring network other than the primary switch. The protection method includes: Determine if there is an overcurrent fault in this node switch. If there is an overcurrent fault, proceed to the next step. The following conditions are used to determine if there is an overcurrent fault in this node switch: when GOOSE communication is normal, the line current exceeds the preset value and exceeds the fault confirmation time, and the fault component is in the positive direction; when GOOSE communication is abnormal, the line current exceeds the preset value and exceeds the fault confirmation time. Determine whether the first switch has an operating condition. If it does, the first switch is activated. The operating conditions for the first switch include: the fault component of the overcurrent fault is in the positive direction and no fault information from the adjacent node is received; or, the fault component of the overcurrent fault is in the negative direction. Determine whether there are any operating conditions for the main switches other than the first switch. If so, the main switches are activated. The operating conditions for the main switches other than the first switch include: when the node detects a fault and receives fault information from only one node, the main switch upstream of the node is faulty; when the node does not detect a fault and receives fault information from only one node on either side of the node, the main switch downstream of the node is faulty.

2. The method according to claim 1, characterized in that, Also includes: Set an action delay for the first switch and the main switch.

3. A ring network line protection device based on closed-loop operation conditions, characterized in that, The ring network line includes at least one primary switch and multiple main switches. The primary switch is a switch connected to a substation at one end, and the main switches are switches on the main line of the ring network other than the primary switch. The protective device includes: The node overcurrent fault detection module is used to determine whether there is an overcurrent fault in the node switch. If there is an overcurrent fault, the next step is executed. The node switch is judged to have an overcurrent fault based on the following conditions: when GOOSE communication is normal, the line current exceeds the preset value and exceeds the fault confirmation time, and the fault component is in the positive direction; when GOOSE communication is abnormal, the line current exceeds the preset value and exceeds the fault confirmation time. The first switch fault judgment module is used to determine whether the first switch has an operating condition. If it does, the first switch is activated. The operating conditions of the first switch include: the fault component of the overcurrent fault is in the positive direction and no fault information from the adjacent node is received; or, the fault component of the overcurrent fault is in the negative direction. The main switch fault judgment module is used to determine whether there are any operating conditions for the main switches other than the first switch. If so, the main switches are activated. The operating conditions for the main switches other than the first switch include: when the node detects fault information and receives fault information from only one node, the main switch upstream of the node is faulty; when the node does not detect fault information and receives fault information from only one node on either side of the node, the main switch downstream of the node is faulty.

4. The apparatus according to claim 3, characterized in that, Also includes: The delay setting module is used to set the action delay for the first switch and the main switch.

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