CN110596519A - A DC system ground fault detection system and detection method based on Fourier transform - Google Patents

Abstract

The present invention provides a DC system ground fault detection system based on Fourier transform. The DC system ground fault detection system includes a signal acquisition unit, a signal conditioning unit, an A/D conversion unit, a control processing unit, a drive unit, a storage unit, a display unit, a key input unit, an alarm unit and a communication unit; the DC system ground fault detection system uses Fourier transform to analyze the collected signals to determine whether the DC system is connected to AC power or a ground fault occurs , and send an alarm signal in time, and upload it to the monitoring center through the communication unit. The invention provides a DC system grounding fault detection system and method based on Fourier transform, which detects the DC system in various aspects and improves the reliability and safety of the DC system.

Description

A DC system ground fault detection system and its detection based on Fourier transform method

technical field

The invention belongs to the technical field of electric power detection, and in particular relates to a Fourier transform-based DC system grounding fault detection system and a detection method thereof.

Background technique

As one of the important components of the power system, the DC system provides reliable DC power for the relay protection devices and automation systems of the power system, and is an important guarantee for ensuring the safe and reliable operation of power equipment and power systems.

When the DC system fails, it will cause faults such as relay protection malfunction, which may lead to other larger accidents. In order to avoid the short-circuit fault of the DC system caused by grounding, and then lead to abnormal actions such as control loops and relay protection, it is necessary to detect the DC system in real time. The invention proposes a DC system grounding fault detection system based on Fourier transform, which detects the DC system in various aspects and improves the reliability and safety of the DC system.

Contents of the invention

The invention provides a DC system grounding fault detection system and method based on Fourier transform, which detects the DC system in various aspects and improves the reliability and safety of the DC system.

The present invention is specifically a DC system ground fault detection system based on Fourier transform. The DC system ground fault detection system includes a signal acquisition unit, a signal conditioning unit, an A/D conversion unit, a control processing unit, a drive unit, a storage unit, a display unit, a key input unit, an alarm unit, and a communication unit, the signal acquisition unit is sequentially connected to the signal conditioning unit, the A/D conversion unit, the control processing unit, and the drive unit in a sequential ring, and the The control processing unit is also respectively connected with the storage unit, the display unit, the key input unit, the alarm unit, and the communication unit; the DC system ground fault detection system adopts Fourier transform to collect The signal is analyzed to determine whether the DC system is connected to AC power or whether a ground fault occurs, and an alarm signal is sent in time, and is uploaded to the monitoring center through the communication unit.

The signal acquisition unit uses a voltage sensor to collect the voltage signal of the DC system, and uses a current sensor to collect the branch leakage current signal of the DC system; the voltage sensor is installed on the DC bus, and the current sensor is installed on the on each branch of the DC system.

The signal conditioning unit includes an integrating circuit and a filter circuit, the integrating circuit is connected to the current sensor, the signals output by the current sensor are connected in parallel, and then the voltage signal that can be collected is output through the integrating circuit; the filtering circuit A low-pass filter is used to filter out interfering signals.

The driving unit receives a driving signal from the control processing unit to drive the voltage sensor and the current sensor to collect signals.

The key input unit combines the storage unit and the display unit to perform parameter setting and information query; the alarm unit uses an audible and visual alarm, which can send out an audible and visual alarm signal when a ground fault occurs in the DC system, and The fault display is carried out via the display unit.

The communication unit adopts RS485 communication circuit, which has good anti-interference performance, and can upload the detection results and alarm signals of the DC system ground fault detection system to the monitoring center; the DC system ground fault detection system can also The control signal of the monitoring center is received through the communication unit.

The control processing unit performs Fourier transform on the voltage signal, extracts the AC voltage signal, and calculates the effective value of the AC voltage signal; calculates the average value of the voltage signal within a single cycle as the effective value of the DC voltage signal, Obtaining the positive pole-to-ground voltage signal and the negative pole-to-ground voltage signal of the DC system; judging whether a ground fault occurs in the DC system according to the leakage current signal.

The present invention also provides a detection method of a DC system ground fault detection system based on Fourier transform, and the detection method includes the following steps:

Step (1): The signal acquisition unit acquires the DC system voltage signal and branch leakage current signal;

Step (2): converting the branch leakage current signal into a voltage signal through the integrating circuit;

Step (3): filter out the interference signal through the filter circuit;

Step (4): A/D conversion is performed through the A/D conversion unit;

Step (5): The control processing unit performs Fourier transform on the voltage signal to extract an AC voltage signal;

Step (6): Calculate the effective value of the AC voltage signal;

Step (7): judging whether the effective value of the AC voltage signal is greater than zero, if greater than zero, an alarm is issued through the alarm unit, and the display unit displays the alarm of AC intrusion and the effective value of the AC voltage signal ;

Step (8): Calculate the average value of the voltage signal collected in a single cycle as a DC voltage value, and obtain the positive pole-to-ground voltage signal and the negative pole-to-ground voltage signal of the DC system;

Step (9): judging whether the current signal is greater than zero, if greater than zero, a ground fault occurs in the DC system;

Step (10): Calculate the grounding resistance by combining the positive pole-to-ground voltage signal and the negative pole-to-ground voltage signal, and send an alarm signal through the alarm unit, and display the ground fault, ground current value and ground fault through the display unit resistance;

Step (11): Upload the detection result to the monitoring center through the communication unit.

Description of drawings

FIG. 1 is a schematic structural diagram of a DC system ground fault detection system based on Fourier transform according to the present invention.

Fig. 2 is a working flowchart of a detection method of a DC system ground fault detection system based on Fourier transform in the present invention.

Detailed ways

The specific implementation of a DC system ground fault detection system based on Fourier transform of the present invention will be described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the DC system ground fault detection system of the present invention includes a signal acquisition unit, a signal conditioning unit, an A/D conversion unit, a control processing unit, a drive unit, a storage unit, a display unit, a key input unit, an alarm unit and A communication unit, the signal acquisition unit is sequentially connected to the signal conditioning unit, the A/D conversion unit, the control processing unit, and the drive unit in a sequential ring, and the control processing unit is also respectively connected to the storage unit, The display unit, the key input unit, the alarm unit, and the communication unit are connected; the DC system ground fault detection system uses Fourier transform to analyze the collected signals to determine whether the DC system has The AC power is connected in series, whether there is a ground fault, and an alarm signal is sent in time, and uploaded to the monitoring center through the communication unit.

The signal acquisition unit uses a voltage sensor to collect the voltage signal of the DC system, and uses a current sensor to collect the branch leakage current signal of the DC system; the voltage sensor is installed on the DC bus, and the current sensor is installed on the on each branch of the DC system.

The signal conditioning unit includes an integrating circuit and a filter circuit, the integrating circuit is connected to the current sensor, the signals output by the current sensor are connected in parallel, and then the voltage signal that can be collected is output through the integrating circuit; the filtering circuit A low-pass filter is used to filter out interfering signals.

The driving unit receives a driving signal from the control processing unit to drive the voltage sensor and the current sensor to collect signals.

The key input unit combines the storage unit and the display unit to perform parameter setting and information query; the alarm unit uses an audible and visual alarm, which can send out an audible and visual alarm signal when a ground fault occurs in the DC system, and The fault display is carried out via the display unit.

The communication unit adopts RS485 communication circuit, which has good anti-interference performance, and can upload the detection results and alarm signals of the DC system ground fault detection system to the monitoring center; the DC system ground fault detection system can also The control signal of the monitoring center is received through the communication unit.

The control processing unit performs Fourier transform on the voltage signal, extracts the AC voltage signal, and calculates the effective value of the AC voltage signal; calculates the average value of the voltage signal within a single cycle as the effective value of the DC voltage signal, Obtaining the positive pole-to-ground voltage signal and the negative pole-to-ground voltage signal of the DC system; judging whether a ground fault occurs in the DC system according to the leakage current signal.

As shown in Figure 2, the present invention also provides a detection method of a DC system ground fault detection system based on Fourier transform, and the detection method includes the following steps:

Step (1): The signal acquisition unit acquires the DC system voltage signal and branch leakage current signal;

Step (2): converting the branch leakage current signal into a voltage signal through the integrating circuit;

Step (3): filter out the interference signal through the filter circuit;

Step (4): A/D conversion is performed through the A/D conversion unit;

Step (5): The control processing unit performs Fourier transform on the voltage signal to extract an AC voltage signal;

Step (6): Calculate the effective value of the AC voltage signal;

Step (7): judging whether the effective value of the AC voltage signal is greater than zero, if greater than zero, an alarm is issued through the alarm unit, and the display unit displays the alarm of AC intrusion and the effective value of the AC voltage signal ;

Step (8): Calculate the average value of the voltage signal collected in a single cycle as a DC voltage value, and obtain the positive pole-to-ground voltage signal and the negative pole-to-ground voltage signal of the DC system;

Step (9): judging whether the current signal is greater than zero, if greater than zero, a ground fault occurs in the DC system;

Step (10): Calculate the grounding resistance by combining the positive pole-to-ground voltage signal and the negative pole-to-ground voltage signal, and send an alarm signal through the alarm unit, and display the ground fault, ground current value and ground fault through the display unit resistance;

Step (11): Upload the detection result to the monitoring center through the communication unit.

Finally, it should be noted that the combination of the above embodiments only illustrates the technical solution of the present invention rather than limiting it. Those of ordinary skill in the art should understand that those skilled in the art can modify or equivalently replace the specific embodiments of the present invention, but these modifications or changes are within the protection scope of the pending claims.

Claims (8)

1. A direct current system ground fault detection system based on Fourier transform is characterized by comprising a signal acquisition unit, a signal conditioning unit, an A/D conversion unit, a control processing unit, a driving unit, a storage unit, a display unit, a key input unit, an alarm unit and a communication unit, wherein the signal acquisition unit is sequentially and annularly connected with the signal conditioning unit, the A/D conversion unit, the control processing unit and the driving unit, and the control processing unit is respectively connected with the storage unit, the display unit, the key input unit, the alarm unit and the communication unit; the direct current system ground fault detection system analyzes the acquired signals by adopting Fourier transform, judges whether the direct current system has series alternating current or not and has ground fault or not, timely sends out alarm signals and uploads the alarm signals to a monitoring center through the communication unit.

2. The direct current system ground fault detection system based on the Fourier transform as claimed in claim 1, wherein the signal acquisition unit adopts a voltage sensor to acquire a voltage signal of the direct current system, and adopts a current sensor to acquire a branch leakage current signal of the direct current system; the voltage sensor is installed on a direct current bus, and the current sensor is installed on each branch of the direct current system.

3. The system for detecting the ground fault of the direct current system based on the Fourier transform as claimed in claim 2, wherein the signal conditioning unit comprises an integrating circuit and a filtering circuit, the integrating circuit is connected with the current sensor, the signal output by the current sensor is connected in parallel, and then the voltage signal which can be collected is output through the integrating circuit; the filter circuit filters interference signals by adopting a low-pass filter.

4. The system according to claim 3, wherein the driving unit receives the driving signal from the control processing unit to drive the voltage sensor and the current sensor to collect signals.

5. The system for detecting the ground fault of the direct current system based on the Fourier transform as claimed in claim 4, wherein the key input unit is combined with the storage unit and the display unit to perform parameter setting and information query; the alarm unit adopts an audible and visual alarm, when the direct current system has a ground fault, an audible and visual alarm signal can be sent out, and fault display is carried out through the display unit.

6. The direct current system ground fault detection system based on the Fourier transform as claimed in claim 5, wherein the communication unit adopts an RS485 communication circuit, has good anti-interference performance, and can upload the detection result and the alarm signal of the direct current system ground fault detection system to the monitoring center; the direct current system ground fault detection system can also receive a control signal of the monitoring center through the communication unit.

7. The system according to claim 6, wherein the control processing unit performs fourier transform on the voltage signal, extracts an ac voltage signal, and calculates an effective value of the ac voltage signal; calculating an average value in a single period of the voltage signal as an effective value of the direct current voltage signal to obtain a positive electrode voltage-to-ground signal and a negative electrode voltage-to-ground signal of the direct current system; and judging whether the direct current system has a ground fault according to the leakage current signal.

8. The detection method of the ground fault detection system of the direct current system based on the Fourier transform according to any one of claims 1 to 7, characterized in that the detection method comprises the following steps:

step (1): the signal acquisition unit acquires the voltage signal of the direct current system and the branch leakage current signal;

step (2): converting the branch leakage current signal into a voltage signal through the integrating circuit;

and (3): filtering interference signals through the filter circuit;

and (4): performing A/D conversion by the A/D conversion unit;

and (5): the control processing unit performs Fourier transform on the voltage signal and extracts an alternating voltage signal;

and (6): calculating the effective value of the alternating voltage signal;

and (7): judging whether the effective value of the alternating voltage signal is greater than zero, if so, sending an alarm through the alarm unit, and displaying the alternating current entering alarm and the effective value of the alternating voltage signal through the display unit;

and (8): calculating the average value of the voltage signals collected in a single period as a direct current voltage value to obtain a positive electrode voltage-to-ground voltage signal and a negative electrode voltage-to-ground voltage signal of the direct current system;

and (9): judging whether the current signal is greater than zero, if so, generating a ground fault in the direct current system;

step (10): calculating a grounding resistance by combining the anode voltage-to-ground signal and the cathode voltage-to-ground signal, sending an alarm signal through the alarm unit, and displaying a grounding fault, a grounding current value and a grounding resistance value through the display unit;

step (11): and uploading the detection result to the monitoring center through the communication unit.