Leakage current detection method and system for feeder monitoring device of low-voltage power distribution network

Abstract

The invention relates to a leakage current detection method and system for a feeder monitoring device of a low-voltage power distribution network. The method comprises the following steps of: adding a secondary side leakage transformer on a current acquisition side of the feeder monitoring device of the low-voltage power distribution network to acquire a leakage current detection signal of the low-voltage power distribution network; converting the collected leakage current detection signal into a digital signal, and processing the digital signal to obtain a leakage current measurement value; and comparing the leakage current measurement value with a set threshold value, and generating an alarm mark according to a comparison result. The low-voltage power distribution network feeder line monitoring device can be used for realizing low-voltage power distribution network leakage current detection, meets the requirements of acquisition precision and real-time response, and prevents electrical fire accidents caused by single-phase grounding.

Description

Technical Field

[0001] The present invention relates to the technical field of low-voltage distribution network fault detection, and in particular to a leakage current detection method and system for a low-voltage distribution network feeder monitoring device. Background Art

[0002] A leakage fault refers to the current flowing from a normal circuit to the ground or other places through an unexpected path. The possible causes of a leakage fault include line insulation damage, equipment leakage current, ground fault, etc. When a leakage fault occurs in the line, it will cause current leakage, which may cause personal safety accidents and also cause the system to trip. Leakage protection is an effective measure to achieve safe and reliable operation of low-voltage distribution networks. At present, many ground fault leakage protectors on the market use software to synthesize leakage current algorithms for three-phase current acquisition. Although this design can also detect and output the leakage current signal when a ground fault occurs in the AC circuit and achieve the purpose of cutting off the AC circuit, it does not directly collect leakage current. Therefore, there is a certain error compared to directly collecting leakage current. The acquisition operation takes time, and real-time response is difficult to guarantee.

[0003] The low-voltage distribution network feeder monitoring device is mainly installed in the distribution station room, the pole-mounted integrated distribution cabinet or the low-voltage cable branch box. It can monitor the electrical quantity and state quantity of one or more low-voltage circuits at the same time, and upload the monitoring data to the edge computing terminal on the substation side through the low-voltage distribution network communication network. The currently used low-voltage distribution network feeder monitoring device does not yet have the leakage current detection function. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a leakage current detection method and system for a low-voltage distribution network feeder monitoring device, which can use the low-voltage distribution network feeder monitoring device to realize low-voltage distribution network leakage current detection, and meet the collection accuracy and real-time response requirements, thereby preventing electrical fire accidents caused by single-phase grounding.

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a leakage current detection method of a low-voltage distribution network feeder monitoring device, comprising the following steps:

[0006] A secondary leakage current transformer is added to the current collection side of the low-voltage distribution network feeder monitoring device to collect the leakage current detection signal of the low-voltage distribution network;

[0007] The collected leakage current detection signal is converted into a digital signal and then processed to obtain a leakage current measurement value;

[0008] The leakage current measurement value is compared with the set threshold value, and an alarm sign is generated according to the comparison result.

[0009] Furthermore, the low-voltage distribution network is a three-phase four-wire system.

[0010] Furthermore, the secondary-side leakage current transformer is used to collect three-phase line current and neutral line current, and convert the current signal of the secondary mutual inductance into a voltage signal through resistance voltage division to obtain a leakage current detection signal.

[0011] Furthermore, the collected leakage current detection signal is converted into a digital signal and then processed to obtain a leakage current measurement value, including:

[0012] The collected leakage current detection signal is amplified and converted into a digital signal through ADC;

[0013] Extract the spectrum information of the converted digital signal and eliminate noise and distortion through spectrum analysis to obtain the processed signal;

[0014] The leakage current measurement value is calculated using the obtained processed signal.

[0015] Furthermore, the extraction of spectrum information of the converted digital signal is achieved by fast Fourier transform.

[0016] Furthermore, it also includes:

[0017] Determine whether it is necessary to start the leakage protection action according to the alarm sign. If necessary, perform low-voltage distribution network topology identification and perform leakage protection action according to the topology identification result.

[0018] The present invention also provides a leakage current detection system of a low-voltage distribution network feeder monitoring device, which is used to implement the above method, including:

[0019] The acquisition module is used to add a secondary side leakage transformer to the current acquisition side of the low voltage distribution network feeder monitoring device to collect the leakage current detection signal of the low voltage distribution network;

[0020] A processing module, used for converting the collected leakage current detection signal into a digital signal and then processing it to obtain a leakage current measurement value;

[0021] The comparison module is used to compare the leakage current measurement value with the set threshold value and generate an alarm sign according to the comparison result.

[0022] Furthermore, the processing module includes:

[0023] A filter, used for filtering the collected leakage current detection signal;

[0024] An amplifier, used for amplifying the filtered leakage current detection signal;

[0025] ADC, used for converting the amplified leakage current detection signal into a digital signal;

[0026] FFT module, used to extract the spectrum information of the converted digital signal;

[0027] Noise reduction module, used to eliminate noise and distortion through spectrum analysis to obtain processed signals;

[0028] The calculation module is used to calculate the leakage current measurement value using the obtained processed signal.

[0029] Furthermore, the low-voltage distribution network feeder monitoring device is used to monitor the electrical information of one or more low-voltage electrical circuits, and upload the monitoring data to the edge computing terminal on the substation side through the communication network of the low-voltage distribution network.

[0030] Furthermore, the low-voltage distribution network feeder monitoring device comprises:

[0031] A low-voltage distribution network monitoring unit is used to access a DC power supply, a voltage signal and a communication bus through a cascade interface, and collect and process electrical information of one or more low-voltage electrical circuits;

[0032] The low-voltage distribution network communication unit is used to receive the electrical information collected by the low-voltage distribution network monitoring unit and upload it according to instructions.

[0033] Furthermore, the low-voltage distribution network feeder monitoring device also includes a low-voltage distribution network power supply module that provides a DC power supply to a plurality of low-voltage distribution network monitoring units via a cascade interface.

[0034] Beneficial Effects

[0035] Due to the adoption of the above-mentioned technical scheme, the present invention has the following advantages and positive effects compared with the prior art: the present invention realizes leakage current detection of the low-voltage distribution network feeder monitoring device by adding a secondary-side leakage mutual inductor to the current collection side of the low-voltage distribution network feeder monitoring device, combined with the electrical quantity and state quantity information collection capability of the low-voltage distribution network feeder monitoring device, and meets the collection accuracy and real-time response requirements, so as to realize timely discovery and reporting of leakage faults in the low-voltage distribution network, effectively reduce the occurrence of single-phase grounding fault accidents caused by electric shock and leakage, and ensure the safe and stable operation of the low-voltage distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of a current collection scheme according to a first embodiment of the present invention;

[0037] Figure 2 is a schematic structural diagram of a leakage current detection system according to a first embodiment of the present invention;

[0038] Figure 3 4 is a flowchart of the leakage current detection signal processing according to the first embodiment of the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0040] A first embodiment of the present invention relates to a leakage current detection method for a low-voltage distribution network feeder monitoring device, comprising the following steps:

[0041] A secondary leakage current transformer is added to the current collection side of the low-voltage distribution network feeder monitoring device to collect the leakage current analog signal of the low-voltage distribution network;

[0042] The collected leakage current analog signal is converted into a digital signal and then processed to obtain a leakage current measurement value;

[0043] The leakage current measurement value is compared with the set threshold value, and an alarm sign is generated according to the comparison result.

[0044] The low-voltage distribution network feeder monitoring device adopted in this embodiment is suitable for 0.4kV distribution network. It is installed in a distribution station room, a pole-mounted integrated distribution cabinet, a low-voltage pole-mounted circuit breaker or a low-voltage cable branch box. It consists of a low-voltage distribution network communication unit, a low-voltage distribution network power supply module and a low-voltage distribution network monitoring unit. It can simultaneously monitor the electrical quantities and status quantities of one or more low-voltage circuits, and upload the monitoring data to the edge computing terminal on the substation side through the low-voltage distribution network communication network.

[0045] Among them, the low-voltage distribution network communication unit can connect to multiple low-voltage distribution network monitoring units, intelligent circuit breakers and other equipment downward, and has a module with data collection and unified upward communication functions.

[0046] The low-voltage distribution network monitoring unit is connected to the DC power supply, voltage signal and communication bus through the cascade interface, collects and processes the electrical quantity, switch quantity and other information of the low-voltage electrical circuit, connects to the communication unit, and has modules with functions such as phase sequence identification and event processing.

[0047] The low-voltage distribution network power supply module provides DC power supply, voltage signal and communication bus to multiple monitoring units through a cascade interface.

[0048] like Figure 1 As shown in the figure, the low-voltage distribution network is a three-phase four-wire system. The additional secondary-side leakage transformer is used to collect the three-phase line current and the neutral line current, and the four currents A, B, C, and N are collected through the same leakage transformer. The system structure after adding leakage current analog signal collection is as follows Figure 2 shown.

[0049] This implementation adopts the leakage current direct access method, and uses resistance voltage division to convert the leakage current signal of the secondary mutual inductance into a voltage signal to access the device. The device takes 128 points per cycle to ensure the accuracy of leakage current collection. The hardware is equipped with filtering and operational amplifier circuits to handle the clutter on the leakage current signal and ensure that the waveform used in the leakage current calculation is normal. The sampling calculation uses the FFT algorithm to ensure accuracy and reliability, and can also ensure millisecond-level data calculation.

[0050] Specifically, if Figure 3 As shown, first initialize and configure the underlying hardware, such as setting the amplifier gain to ensure that the hardware device is running in the required state. Secondly, it is necessary to read the sampled data in the ADC, and use FFT to process the waveform signal after obtaining the data to eliminate the interference or distortion of the signal itself. It is necessary to calculate and process the processed signal data to obtain a visual measurement value. After successfully obtaining the measurement value, it is possible to determine whether the measurement value exceeds the limit and provide an alarm sign.

[0051] A second embodiment of the present invention relates to a leakage current detection system for a low-voltage distribution network feeder monitoring device, which is used to implement the above method, including:

[0052] The acquisition module is used to add a secondary side leakage transformer to the current acquisition side of the low voltage distribution network feeder monitoring device to collect the leakage current detection signal of the low voltage distribution network;

[0053] A processing module, used for converting the collected leakage current analog signal into a digital signal and then processing it to obtain a leakage current measurement value;

[0054] The comparison module is used to compare the leakage current measurement value with the set threshold value and generate an alarm sign according to the comparison result.

[0055] The processing module includes:

[0056] A filter, used for filtering the collected leakage current analog signal;

[0057] An amplifier, used for amplifying the filtered leakage current analog signal;

[0058] ADC, used for converting the amplified leakage current analog signal into a digital signal;

[0059] FFT module, used to extract the spectrum information of the converted digital signal;

[0060] Noise reduction module, used to eliminate noise and distortion through spectrum analysis to obtain processed signals;

[0061] The calculation module is used to calculate the leakage current measurement value using the obtained processed signal.

[0062] The low-voltage distribution network feeder monitoring device adopted in this embodiment is suitable for 0.4kV distribution network. It is installed in a distribution station room, a pole-mounted integrated distribution cabinet, a low-voltage pole-mounted circuit breaker or a low-voltage cable branch box. It consists of a low-voltage distribution network communication unit, a low-voltage distribution network power supply module and a low-voltage distribution network monitoring unit. It can simultaneously monitor the electrical quantities and status quantities of one or more low-voltage circuits, and upload the monitoring data to the edge computing terminal on the substation side through the low-voltage distribution network communication network.

[0063] Among them, the low-voltage distribution network communication unit can connect to multiple low-voltage distribution network monitoring units, intelligent circuit breakers and other equipment downward, and has a module with data collection and unified upward communication functions.

[0064] The low-voltage distribution network monitoring unit is connected to the DC power supply, voltage signal and communication bus through the cascade interface, collects and processes the electrical quantity, switch quantity and other information of the low-voltage electrical circuit, connects to the communication unit, and has modules with functions such as phase sequence identification and event processing.

[0065] The low-voltage distribution network power supply module provides DC power supply, voltage signal and communication bus to multiple monitoring units through a cascade interface.

Claims

1. A leakage current detection method for a low voltage distribution network feeder monitoring device, characterized in that: The following steps are involved: A secondary leakage current transformer is added to the current collection side of the low-voltage distribution network feeder monitoring device to collect the leakage current detection signal of the low-voltage distribution network; The collected leakage current detection signal is converted into a digital signal and then processed to obtain a leakage current measurement value; The leakage current measurement value is compared with the set threshold value, and an alarm sign is generated according to the comparison result.

2. The method according to claim 1, characterized in that The low-voltage distribution network is a three-phase four-wire system.

3. The method according to claim 2, characterized in that The secondary-side leakage current transformer is used to collect three-phase line current and neutral line current, and convert the current signal of the secondary mutual inductance into a voltage signal through resistance voltage division to obtain a leakage current detection signal.

4. The method according to claim 1, characterized in that The step of converting the collected leakage current detection signal into a digital signal and then processing it to obtain a leakage current measurement value includes: The collected leakage current detection signal is amplified and converted into a digital signal through ADC; Extract the spectrum information of the converted digital signal and eliminate noise and distortion through spectrum analysis to obtain the processed signal; The leakage current measurement value is calculated using the obtained processed signal.

5. The method according to claim 1, characterized in that Also includes: Determine whether it is necessary to start the leakage protection action according to the alarm sign. If necessary, perform low-voltage distribution network topology identification and perform leakage protection action according to the topology identification result.

6. A leakage current detection system for a low voltage distribution network feeder monitoring device, characterized in that: Used to implement the method according to claims 1-5, comprising: The acquisition module is used to add a secondary side leakage transformer to the current acquisition side of the low voltage distribution network feeder monitoring device to collect the leakage current detection signal of the low voltage distribution network; A processing module, used for converting the collected leakage current detection signal into a digital signal and then processing it to obtain a leakage current measurement value; The comparison module is used to compare the leakage current measurement value with the set threshold value and generate an alarm sign according to the comparison result.

7. The system according to claim 6, characterized in that The processing module comprises: A filter, used for filtering the collected leakage current detection signal; An amplifier, used for amplifying the filtered leakage current detection signal; ADC, used for converting the amplified leakage current detection signal into a digital signal; FFT module, used to extract the spectrum information of the converted digital signal; Noise reduction module, used to eliminate noise and distortion through spectrum analysis to obtain processed signals; The calculation module is used to calculate the leakage current measurement value using the obtained processed signal.

8. The system according to claim 6, characterized in that The low-voltage distribution network feeder monitoring device is used to monitor the electrical information of one or more low-voltage electrical circuits, and upload the monitoring data to the edge computing terminal on the substation side through the communication network of the low-voltage distribution network.

9. The system according to claim 8, characterized in that The low voltage distribution network feeder monitoring device comprises: A low-voltage distribution network monitoring unit is used to access a DC power supply, a voltage signal and a communication bus through a cascade interface, and collect and process electrical information of one or more low-voltage electrical circuits; The low-voltage distribution network communication unit is used to receive the electrical information collected by the low-voltage distribution network monitoring unit and upload it according to instructions.

10. The system according to claim 8, characterized in that The low-voltage distribution network feeder monitoring device also includes a low-voltage distribution network power supply module that provides a DC power supply to a plurality of low-voltage distribution network monitoring units through a cascade interface.

Images