Rapid identification method for short-circuit fault of feeder terminal equipment

Abstract

The invention provides a feeder line terminal equipment short circuit fault rapid identification method, which utilizes a first half wave breaking phenomenon to carry out instant fault detection and identification, and comprises the following steps: establishing a fault database in a fault identification process, a longitudinal coordinate ifind at a curve intersection point of the shortest operation time t1 necessary for terminal equipment and a fault current waveform curve i2 is taken as a current instantaneous setting value S2, an absolute value of a curve slope of an intersection point p of the ifind and the fault current waveform curve i2 is taken as a setting value K2 = di2 (t) / dt of a current change rate, and fault current characteristic information (S2, K2) is stored in a fault library as a rapid identification criterion. The short-circuit fault database is continuously updated along with the fault identification process, and the short-circuit fault database is compared with the criterion stored in the fault database when the fault occurs, so that the fault identification can be completed in a 1 / 4 period, that is, the identification of the fault current can be completed in t2 time.

Description

Technical Field

[0001] The present application relates to the technical field of feeder terminals, and in particular to a method for quickly identifying short-circuit faults in feeder terminal equipment. Background Art

[0002] The statements in this section merely provide background technical information related to the present application and do not necessarily constitute prior art.

[0003] At present, in the field of domestic feeder terminals, the most widely used method is to identify short-circuit faults by calculating the effective value of current. This method usually requires a complete cycle of current waveform, calculates the square of each instantaneous value of the current waveform within the time period T, integrates these square values ​​from the beginning to the end of the cycle (usually 0 to T), divides the integration result by the cycle T, and obtains the average value of the square of the current. Taking the square root of the average value is the effective value (RMS value) of the current.

[0004] Accurately calculating the effective value of current requires considering the current changes over a complete cycle to ensure that the value obtained can accurately reflect the average energy delivery capacity of the current throughout the entire cycle. If the waveform is not a sine wave or other periodic regular waveform, then it is also necessary to calculate based on the entire cycle to accurately capture its characteristics.

[0005] As the power grid develops towards intelligence and automation, the requirements for fault response speed and processing accuracy are increasing. Traditional fault identification technology is limited by the complexity and delay of signal processing, which affects the timely processing of power grid faults. The existing technology uses the effective value of the primary and secondary fusion of pole-mounted switches to identify short-circuit faults, which has the following defects: 1) It takes a long time to calculate the effective value of current, and a faster identification solution is needed to meet the needs of new power relay protection; 2) The traditional method cannot save the historical short-circuit fault characteristic information, and each fault identification requires a new logical judgment. Summary of the invention

[0006] In order to solve the problem in the background technology, the present application proposes a method for quickly identifying a short-circuit fault of a feeder terminal device.

[0007] The present application provides a method for quickly identifying a short-circuit fault of a feeder terminal device, comprising the following steps: S101: collect the output current of the corresponding three-phase CT in real time through its own AD sampling circuit to obtain a discrete sample signal; S102: Using a sliding window to truncate the sample signal in real time, and the window opening time is set to half a cycle; S103: The ordinate i_find at the intersection of the shortest operation time t1 required by the terminal device and the fault current waveform curve i2 is taken as the instantaneous current setting value S2; S104: The absolute value of the slope of the intersection point p of i_find and the fault current waveform curve (i2) is used as the setting value K2=|di2(t) / dt| of the current change rate; S105: The fault current characteristic information (S2, K2) is stored in the fault database as a criterion for rapid identification. The criterion formula is: ; S106: Calculate the absolute value of the real-time current value in the slider Is it greater than or equal to |S2|, and the absolute value of the current change rate at the intersection of the curve and the i_find line Is it greater than or equal to |K2|? If both conditions are met, it is determined that a short circuit fault occurs at this moment.

[0008] Preferably, a group of pole switches for segmentation points are provided in the feeder terminal, each pole switch for segmentation points is provided with a power supply PT to convert the 10kv line voltage into an AK220v output power supply voltage, and is provided with a CT for collecting current information.

[0009] Preferably, the feeder terminal includes an AD sampling circuit, a control circuit, and a storage unit. The AD sampling circuit collects the three-phase current of the corresponding pole switch, the control circuit monitors the AD sampling part in real time, performs denoising, fault logic judgment and sends a trip signal of the sample point, and the storage unit completes the storage of protection settings, parameters and fault models.

[0010] Preferably, in step S103, the shortest operation time t1 is an empirical value, the setting range is 3-5 ms, and the fault current waveform curve i2 is a fault recording of the fault current.

[0011] Preferably, the short circuit fault rapid identification method further includes updating the fault library, and the specific method is as follows: S201: After power is supplied, the control circuit accesses the storage unit through the serial port, reads the fault library stored in the storage unit, and filters out noise points and performs verification and comparison on the collected real-time fault current waveform curve; S202: Perform short-circuit fault judgment on the real-time fault current waveform curve through the method of steps S102 to S106. If a certain fault current waveform curve is identified as a non-short-circuit current, but the traditional method identifies the corresponding fault current waveform curve as a short-circuit current, then the (Sx, Kx) corresponding to the corresponding fault current waveform curve is saved in the storage unit.

[0012] Preferably, when the control circuit determines that a short circuit fault occurs, a trip command is issued, and after the trip countdown is completed, a signal is sent to the trip relay to drive the column switch to perform the trip operation.

[0013] Compared with the prior art, the beneficial effects of this application are: (1) The present application selects half-cycle sampling through a sliding window, utilizes the characteristics of increasing and rapidly changing short-circuit current values, takes the ordinate i_find at the intersection of the shortest operation time t0 required by the terminal device and the maximum short-circuit current i2 curve under the maximum mode as the instantaneous current setting value S1, takes the slope of the curve at the intersection p of i_find and the fault current waveform curve as the setting value K1 of the current change rate, and stores the fault current (S1, K1) in the fault library as a criterion for rapid identification. The identification speed is fast, which is in line with the development trend of automation and intelligence of power equipment.

[0014] (2) The present application utilizes a storage unit to store fault judgment criteria and updates the same, thereby further reducing the recognition speed of short-circuit faults, adapting to the differences among feeder terminals, and improving recognition accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0016] Figure 1 This is a schematic diagram of extracting characteristic fault points from fault current waveforms in this application. Figure 2 This is a characteristic diagram of the fault current and non-fault current of this application, Figure 3 Schematic diagram of the method flow of this application. DETAILED DESCRIPTION

[0017] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0018] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0019] In the present disclosure, terms such as "upper", "lower", "left", "right", "front", "back", "vertical", "horizontal", "side", "bottom" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. They are relational words determined only for the convenience of describing the structural relationships of the various parts or elements of the present disclosure, and do not specifically refer to any part or element in the present disclosure and should not be understood as limitations on the present disclosure.

[0020] Example 1 like Figures 1 to 3 As shown, the present application provides a method for quickly identifying short-circuit faults in feeder terminal equipment, including two steps of quickly identifying short-circuit faults and automatically updating a fault model library.

[0021] Among them, the rapid identification of short-circuit faults first constructs the feeder terminal, in which a group of pole switches for segmentation points are set. Each segmentation point pole switch is equipped with a power supply PT (voltage transformer) to convert the 10kv line voltage into an AK220v output power supply voltage, and is equipped with a CT (current transformer) for collecting current information. The feeder terminal includes an AD sampling circuit, a control circuit, and a storage unit. The AD sampling circuit collects the three-phase current of the corresponding pole switch. The control circuit monitors the AD sampling part in real time, performs sample point denoising, fault logic judgment, and sends a trip signal. The storage unit completes the storage of protection settings, parameters, and fault models: The specific steps include: Step 1: When the terminal device is powered on, it immediately calculates the line fault current. The fault line current calculation collects the output current of the corresponding three-phase CT in real time through its own AD sampling circuit, and reads the real-time current sample value through a fixed AD channel; Step 2: Use a sliding window (a flow control technology) to truncate the AD sampling signal in real time. Set the window opening time to half a cycle. Calculate the shortest operation time t1 required by the terminal device and the vertical coordinate i_find at the intersection of the fault current waveform curve i2 as the instantaneous current setting value S2. Calculate the slope of the curve at the intersection p of i_find and the fault current waveform curve as the setting value K2=|di2(t) / dt| of the current change rate. Store the fault current characteristic information (S2, K2) in the fault library as a criterion for rapid identification. The criterion formula is: Step 3: Calculate the real-time current data of the feeder terminal equipment and calculate the absolute value of the real-time current value by moving the slider Is it greater than or equal to |S2|, and the absolute value of the current change rate at the intersection of the curve and the i_find line Is it greater than or equal to |K2|? If both conditions are met, it is determined that a short circuit fault occurs at this moment; Step 4: Continuously update the fault database as short - circuit faults occur during the operation of the device: After the feeder terminal device is powered on, the control circuit accesses the storage unit in the form of a serial port, reads the fault library saved in the storage unit, filters out noise points from the real - time power information collected by the AD and performs verification and comparison: If the current curve is i3, record the instantaneous value S3 of the i3 current curve at time t1 through the sliding window, record the curve slope (current change rate) at the intersection with i_find, K3 = |di3(t) / dt|, and judge the recorded values using the criterion formula. After judgment, S3 < S2 and K3 < K2, that is, it is determined that the current is a non - short - circuit current; If the current curve is i1, record the instantaneous value S1 of the i1 current curve at time t1 through the sliding window, record the curve slope (current change rate) at the intersection with i_find, K1 = |di1(t) / dt|, and judge the recorded values using the criterion formula. S1 ≥ S2 and K1 ≥ K2, that is, it is determined that the current is a short - circuit current. When the control circuit determines a short - circuit fault, it issues a tripping command. After the tripping countdown ends, it sends a signal to the tripping relay to drive the pole - mounted switch to perform a tripping operation.

[0022] Step 5: When the current criterion cannot determine a short - circuit fault, but it is determined to be a short - circuit fault by the traditional method, record the (Sx, Kx) fault information at this time, and first judge whether the fault library is full. If the fault library is not full, store this fault characteristic information in the storage unit.

[0023] The storage unit is a non - volatile memory.

[0024] In step 2, the shortest operation time t1 is an empirical value, and the setting range is 3 - 5 ms. The fault current waveform curve i2 is the fault recording of the fault current.

[0025] In step 5, multiple criteria in the fault library are used through an "OR" logic. As long as one criterion is met, it can be determined that there is a short - circuit fault.

[0026] The traditional method is the method of collecting the current waveform of a complete cycle as a sample in the background technology to determine the waveform characteristics and then judge the short - circuit fault. The traditional method is set in the control circuit of this application and is executed in parallel with the method of this application.

[0027] As Figure 1 and Figure 2 shown, the method of this application can complete fault identification within 1 / 4 cycle, that is, it can complete the identification of the fault current within time t2. The waveform in the figure is a 1 / 2 bun - shaped wave, and t2 and t3 are the time points of 1 / 4 cycle.

[0028] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0029] Although the above describes the specific implementation methods of the present application in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present application. Technical personnel in the relevant field should understand that on the basis of the technical solution of the present application, various modifications or deformations that can be made by technical personnel in this field without creative work are still within the scope of protection of the present application.

Claims

1. A method for quickly identifying short-circuit faults in feeder terminal equipment, characterized in that: The method comprises the following steps: S101: collecting the output current of the corresponding three-phase CT in real time through its own AD sampling circuit to obtain a discrete sample signal; S102: Using a sliding window to truncate the sample signal in real time, and the window opening time is set to half a cycle; S103: The ordinate i_find at the intersection of the shortest operation time t1 required by the terminal device and the fault current waveform curve i2 is taken as the instantaneous current setting value S2; S104: The absolute value of the slope of the intersection point p of i_find and the fault current waveform curve (i2) is used as the setting value K2=|di2(t) / dt| of the current change rate; S105: The fault current characteristic information (S2, K2) is stored in the fault database as a criterion for rapid identification. The criterion formula is: ； S106: Calculate the absolute value of the real-time current value in the slider Is it greater than or equal to |S2|, and the absolute value of the current change rate at the intersection of the curve and the i_find line Is it greater than or equal to |K2|? If both conditions are met, it is determined that a short circuit fault occurs at this moment.

2. A method for quickly identifying a short-circuit fault of a feeder terminal device according to claim 1, characterized in that: A group of pole switches for segmentation points are set in the feeder terminal. Each pole switch for segmentation points is equipped with a power supply PT to convert the 10kv line voltage into an AK220v output power supply voltage, and is equipped with a CT to collect current information.

3. A method for quickly identifying a short-circuit fault of a feeder terminal device according to claim 2, characterized in that: The feeder terminal includes an AD sampling circuit, a control circuit, and a storage unit. The AD sampling circuit collects the three-phase current of the corresponding pole switch. The control circuit monitors the AD sampling part in real time, performs noise removal, fault logic judgment, and sends a trip signal at the sample point. The storage unit completes the storage of protection settings, parameters, and fault models.

4. A method for quickly identifying a short-circuit fault of a feeder terminal device according to claim 1, characterized in that: In the step S103, the shortest operation time t1 is an empirical value, the setting range is 3-5 ms, and the fault current waveform curve i2 is a fault recording of the fault current.

5. A method for quickly identifying a short-circuit fault of a feeder terminal device according to claim 3, characterized in that: The short circuit fault rapid identification method also includes updating the fault library, and the specific method is as follows: S201: After power is supplied, the control circuit accesses the storage unit through the serial port, reads the fault library stored in the storage unit, and filters out noise points and performs verification and comparison on the collected real-time fault current waveform curve; S202: Perform short-circuit fault judgment on the real-time fault current waveform curve through the method of steps S102 to S106. If a certain fault current waveform curve is identified as a non-short-circuit current, but the traditional method identifies the corresponding fault current waveform curve as a short-circuit current, then the (Sx, Kx) corresponding to the corresponding fault current waveform curve is saved in the storage unit.

6. A method for quickly identifying a short-circuit fault of a feeder terminal device according to claim 5, characterized in that: The storage unit is a non-volatile memory.

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