Distribution network single-phase grounding fault detection system and method

Abstract

The present invention provides a single-phase grounding fault detection system and method for a distribution network. The system comprises: two synchronous signal sources, one at each end of a fault line, which simultaneously and synchronously inject a high-voltage signal with a completely identical voltage waveform into the fault line at both ends of the fault phase under GNSS time reference control; because the current reference direction is from one signal source toward the other, the current phases of the fault lines on both sides of the fault point are opposite; and a synchronous detector, which determines the grounding fault point by detecting the current phase reversal point on the fault line under GNSS time reference control. The single-phase grounding fault detection system and method for a distribution network provided by the present invention can effectively solve the problem of difficulty in determining the amplitude detection threshold and frequent misjudgments in existing detection processes.

Description

Technical Field

[0001] The present invention relates to the technical field of distribution network automation, and in particular to a single-phase grounding fault detection system and method for a distribution network. Background Art

[0002] The single-phase ground fault location method of distribution network is divided into the split line detector method and the online real-time fault location method. The offline detector method is further divided into the AC method and the DC method.

[0003] The AC method means that after a line fault occurs, the power is cut off, an AC signal is injected into the fault phase, and then a handheld detector is used to find the fault point along the line using the binary method. Ground detection does not require climbing a pole.

[0004] The DC method means that after a line fault occurs, the power is cut off, a DC signal is injected into the fault phase, and then a handheld clamp ammeter is used to find the fault point along the line using the binary method. During the detection, the clamp ammeter needs to be clamped on the wire and the detection needs to be carried out by climbing a pole.

[0005] The biggest features of the AC method and the DC method are: single-ended injection, amplitude detection, when the signal is detected, the fault point is downstream, when no signal is detected, the fault point is upstream, and the fault point is where the signal disappears.

[0006] AC method: After a line fault occurs, the power is cut off and an AC signal is injected into the fault phase. Then, a handheld detector is used to find the fault point along the line using the binary method.

[0007] The disadvantages of the existing AC method are that the amplitude detection threshold is difficult to determine and misjudgment is often made. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a single-phase grounding fault detection system and method for a distribution network, which can effectively solve the problem that the amplitude detection threshold is difficult to determine and misjudgment often occurs in the existing detection process.

[0009] To solve the above-mentioned technical problems, the present invention provides a single-phase ground fault detection system for a distribution network, the system comprising: two synchronous signal sources, respectively arranged at the two end points of the fault line, and which, under the control of a GNSS time reference, simultaneously and synchronously inject high-voltage signals with completely identical voltage waveforms into the fault line at both ends of the fault phase; since the current reference direction is from one signal source toward the other signal source, the current phases of the fault lines on both sides of the fault point are opposite; and a synchronous detector, which determines the ground fault point by detecting the current phase reversal point on the fault line.

[0010] In some embodiments, the synchronization signal source includes: a GNSS module, for providing longitude and latitude and second pulse signals to a single-chip microcomputer; a signal source single-chip microcomputer, connected to the GNSS module, for synchronously driving an inverter circuit according to the longitude and latitude and second pulse provided by the GNSS module; an inverter circuit, connected to the signal source single-chip microcomputer, for converting the DC power signal output by the power supply into a voltage-synchronized AC current signal under the drive of the signal source single-chip microcomputer, and outputting the voltage-synchronized AC signal to the fault line.

[0011] In some embodiments, the inverter circuit includes: four switching tubes interconnected to form an inverter full-bridge structure.

[0012] In some embodiments, the synchronous signal source further includes: a switch tube driver connected between the switch tube and the signal source microcontroller, for driving the switch tube according to the control signal output by the signal source microcontroller to complete the synchronous inversion of the DC signal.

[0013] In some embodiments, the synchronization signal source further includes: a filter circuit, including a filter capacitor and a filter inductor, connected to the output end of the inverter circuit, and used to filter out the high-frequency signal output by the inverter circuit.

[0014] In some embodiments, the synchronization signal source further includes: an output boost transformer connected to the output end of the filter circuit, for boosting the voltage-synchronous AC signal.

[0015] In some embodiments, the signal source microcontroller synchronously triggers the inverter circuit according to the received second pulse time reference.

[0016] In some embodiments, the synchronous detector includes: an acquisition coil for collecting the AC current signal of the fault line; a detector GNSS module for providing longitude and latitude and a second pulse time reference to the detector microcontroller; a detector microcontroller connected to the acquisition coil and the detector GNSS module for determining the phase and phase reversal point of the AC current signal based on the second pulse.

[0017] In some embodiments, the synchronous detector further includes: an amplifier connected to the acquisition coil, for amplifying the AC current signal collected by the acquisition coil; an active filter connected to the amplifier, for amplifying the amplified signal; a differential converter connected between the active filter and the detector microcontroller, for performing differential conversion on the amplified signal and outputting it to the detector microcontroller.

[0018] In addition, the present invention also provides a method for detecting single-phase grounding faults in a distribution network, the method comprising: injecting voltage synchronization signals into the fault line at the two end points of the fault line respectively. Since the current reference direction is from one signal source toward the other signal source, the current phases of the fault lines on both sides of the fault point are opposite; detecting the phase and phase reversal point of the AC current signal in the fault line; and taking the detected phase reversal point as the grounding fault point.

[0019] After adopting such a design, the present invention has at least the following advantages:

[0020] The double-ended AC injection and phase detection of the present invention improves the fault location accuracy compared with single-ended injection amplitude detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] Figure 1 is a structural diagram of a synchronization signal source provided by an embodiment of the present invention;

[0023] Figure 2 Schematic diagram of the principle of the double-ended signal injection method provided by an embodiment of the present invention;

[0024] Figure 3 4 is a structural diagram of a synchronous detector provided by an embodiment of the present invention.

[0025] Description of reference numerals:

[0026] 1 Lithium battery 2 Filter inductor

[0027] 3 Filter capacitor 4 Output step-up transformer

[0028] 5 Switching tube driver 6 Switching tube driver

[0029] 7 Switching tube driver 8 Switching tube driver

[0030] 9 MCU 10 GNSS module

[0031] 11 AC current transformer T1 switch tube

[0032] T2 switch tube T3 switch tube

[0033] T4 switch tube 21 synchronization signal source

[0034] 22 Synchronous signal source 31 Detector coil

[0035] 32 Active Filter 33 Adjustable Amplifier

[0036] 34 Active Filter 35 Differential Converter

[0037] 36 MCU 37 LCD

[0038] 38 detector GNSS module DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0040] The present invention aims to detect a ground fault in a distribution network by simultaneously injecting an AC voltage signal at both ends of the fault phase. This creates a 180-degree phase shift between the currents on either side of the fault point, i.e., the currents on either side of the fault point are in opposite phase. A handheld detector uses a binary method to detect phase shift along the line, identifying the fault point where the current phase reverses.

[0041] The present invention includes two parts: a synchronous signal source and a synchronous detector. The voltage of the signal source at both ends injects the signal in the same phase, which is called synchronization. The technical solution of the synchronous signal source is as follows: Figure 1 shown.

[0042] See also Figure 1 , the synchronization signal source includes the following components.

[0043] The lithium battery 1 is used to provide power, and its power supply parameters are 60V and 10AH.

[0044] Switching tubes T1, T2, T3, and T4 are four switching tubes, which are interconnected to form an inverter full bridge.

[0045] Filter inductor 2 is used to filter out the high-frequency signal of the switching tube.

[0046] Filter capacitor 3 is used to absorb high-frequency signals.

[0047] The output step-up transformer 4 outputs an AC 80Hz 110mA constant current signal.

[0048] The switch tube drivers 5, 6, 7, and 8 are respectively used to drive corresponding switch tubes under the control of the single chip microcomputer.

[0049] The microcontroller 9, with its 10-bit AD, samples the current signal input from the current transformer 11 into a digital signal. A serial port receives the longitude and latitude input from the GNSS module 10. Two external interrupt sources receive 1PPS pulses per second.

[0050] The GNSS module 10, Beidou Navigation System, provides longitude and latitude and pulse per second to the single chip microcomputer 9. The GNSS module 10 ensures synchronization, which is the key to the present invention.

[0051] The AC current transformer 11 is used to provide a current sampling signal to the single chip microcomputer 9 to ensure a constant current output.

[0052] Double-ended signal injection method Figure 2 See Figure 2 , synchronous signal sources 21 and 22, AC 80Hz 110mA constant current, the two signal sources output signals simultaneously and synchronously under GNSS 1PPS control.

[0053] The reference directions of the power line currents are consistent, and so are currents i1 and i2. This is because the detector's detection direction remains unchanged. At this point, currents i1 and i2 have the same amplitude but opposite phases.

[0054] Synchronous detector technology solutions such as Figure 3 See Figure 3 The detector coil 31 is hollow with 1000 turns. The signal current in the induced power line must be in the same direction during the detection process.

[0055] Active filters 32 and 34 allow 80 Hz signals to pass through.

[0056] The adjustable amplifier 33 amplifies the signal to a level where the waveform is stable.

[0057] The differential converter 35 converts the common ground single-ended signal into a balanced signal.

[0058] The microcontroller 36, with its 10-bit AD, samples the current signal into a digital signal. A serial port receives the longitude and latitude input from the GNSS 10. The 1PPS pulse per second is received and used as a phase reference point, which is the key to the present invention.

[0059] The liquid crystal display 37 has a display pixel of 64*128.

[0060] The detector GNSS module 38, Beidou navigation system, provides longitude and latitude and second pulse to the single chip microcomputer 6.

[0061] The phase difference between the detections of the synchronous detector on both sides of the fault point is about 180 degrees.

[0062] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art can make some simple modifications, equivalent changes or modifications based on the technical content disclosed above, which all fall within the scope of protection of the present invention.

Claims

1. A single-phase grounding fault detection system for a distribution network, characterized in that: include: Two synchronous signal sources are respectively set at the two ends of the fault line, and under the control of the GNSS time reference, they simultaneously and synchronously inject high-voltage signals with completely identical voltage waveforms into the fault line at both ends of the fault phase; because The current reference direction is from one signal source to another signal source, so the fault line current phases on both sides of the fault point are opposite. The synchronization signal sources include: GNSS module, used to provide latitude and longitude and pulse-per-second signals to the microcontroller as a time reference; The signal source microcontroller is connected to the GNSS module and is used to drive the inverter circuit to generate a voltage-synchronized AC signal based on the longitude and latitude provided by the GNSS module and the second pulse; an inverter circuit connected to the signal source microcontroller, and configured to convert the DC power signal output by the power supply into a voltage-synchronized AC signal under the drive of the signal source microcontroller, and output the voltage-synchronized AC signal to the fault line; A synchronous detector locates the ground fault point by detecting the current phase reversal point on the fault line under GNSS time reference control. The synchronous detector includes: Acquisition coil, used to collect AC current signal of fault line; The detector GNSS module is used to provide the latitude and longitude and pulse-per-second time reference to the detector microcontroller; The detector microcontroller is connected to the acquisition coil and the detector GNSS module and is used to determine the phase and phase reversal point of the AC current signal based on the second pulse; an amplifier, connected to the collection coil, for amplifying the current AC signal collected by the collection coil; an active filter connected to the amplifier for filtering the amplified signal; The differential converter is connected between the active filter and the detector microcontroller, and is used to perform differential conversion on the filtered signal and output it to the detector microcontroller.

2. The single-phase grounding fault detection system for distribution network according to claim 1, characterized in that: The inverter circuit includes four switching tubes connected to each other to form an inverter full-bridge structure.

3. The single-phase grounding fault detection system for distribution network according to claim 2, characterized in that: Synchronous signal sources also include: The switch tube driver is connected between the switch tube and the signal source microcontroller, and is used to drive the switch tube according to the control signal output by the signal source microcontroller to complete the synchronous inversion of the DC signal.

4. The single-phase grounding fault detection system for distribution network according to claim 1, characterized in that: Synchronous signal sources also include: The filter circuit, including a filter capacitor and a filter inductor, is connected to the output end of the inverter circuit and is used to filter the high-frequency signal output by the inverter circuit.

5. The distribution network single-phase grounding fault detection system according to claim 4, characterized in that: Synchronous signal sources also include: The output boost transformer is connected to the output end of the filter circuit and is used to boost the voltage synchronous AC signal.

6. The single-phase grounding fault detection system for distribution network according to claim 1, characterized in that: The signal source single chip microcomputer synchronously triggers the inverter circuit to generate a voltage synchronization signal according to the received second pulse time reference.

7. A method for detecting single-phase grounding faults in a distribution network, characterized in that: include: A single-phase grounding fault detection system for a distribution network according to any one of claims 1 to 6; At the two ends of the fault line, voltage synchronization signals are injected into the fault line respectively, and the current phases of the fault lines on both sides of the fault point are opposite; Detecting a phase reversal point of an AC current signal in a fault line; The detected current phase reversal point is regarded as the ground fault point.

Images