CN110794335A - Single-phase grounding detection system based on waveform difference and detection method thereof - Google Patents

Abstract

The invention provides a single-phase grounding detection system based on waveform difference. The detection system includes a zero-sequence current acquisition unit, a voltage acquisition unit, a control processing unit, a key input unit, a storage unit, a display unit, an alarm unit and a communication unit. The detection system judges the ground fault phase according to the collected signal, and then judges the ground fault line according to the difference of the zero sequence current when the ground fault occurs. The invention provides a single-phase grounding detection system and method based on waveform difference, which can accurately and quickly determine the faulty phase and the specific faulty line when a grounding fault occurs, so as to ensure the working reliability of the distribution line.

Description

A single-phase grounding detection system and detection method based on waveform difference

technical field

The invention belongs to the technical field of electric power detection, and in particular relates to a single-phase grounding detection system based on waveform difference and a detection method thereof.

Background technique

When a single-phase ground fault occurs in the system, a relatively small zero-sequence current will be generated, and the line voltage will be almost the same, and it will not have much impact on the load power supply, so it is not necessary to trip immediately. At present, most of the power systems used in my country can still operate normally for 1-2 hours after a single-phase grounding fault occurs, so as to prevent the negative impact of sudden interruption of power supply on users. The requirements for power supply quality and safety are gradually rising. Although the system can operate normally after a ground fault occurs, it increases the ground voltage of the non-faulty phase, and long-term operation with faults can easily damage the insulation at the weak link of the system, resulting in two-phase short circuit or even three-phase short circuit. If arc grounding occurs, it may cause overvoltage of the entire system, which will bring a great threat to the stable operation of the entire power grid. Therefore, it is necessary to accurately judge the fault point.

The invention proposes a single-phase grounding detection system and a detection method based on waveform difference. When a single-phase grounding fault occurs in the system, it is determined whether the grounding fault and the faulty phase occur according to the phase voltage signal, and then according to the zero-sequence current. The consistency principle is used to calculate the difference between the faulty line and the non-faulty line in the signal waveform, accurately determine the faulty line, reduce the power supply range that needs to be processed for power outages, and ensure the normal power supply of the ungrounded line.

SUMMARY OF THE INVENTION

The invention provides a single-phase grounding detection system and method based on waveform difference, which can accurately and quickly determine the faulty phase and the specific faulty line when a grounding fault occurs, so as to ensure the working reliability of the distribution line.

The present invention is specifically a single-phase grounding detection system based on waveform difference. The detection system includes a zero-sequence current acquisition unit, a voltage acquisition unit, a control processing unit, a key input unit, a storage unit, a display unit, an alarm unit and a communication unit. The control processing unit is respectively connected with the zero-sequence current acquisition unit, the voltage acquisition unit, the key input unit, the storage unit, the display unit, the alarm unit, and the communication unit The detection system judges the ground fault phase according to the collected signal, and then judges the ground fault line according to the difference of the zero sequence current when the ground fault occurs.

The zero-sequence current acquisition unit uses zero-sequence current sensors to collect zero-sequence current signals of all lines; the voltage acquisition unit uses voltage sensors to collect voltage signals of each phase.

The display unit adopts an LCD display screen, and cooperates with the key input unit and the storage unit to set parameters of the detection system.

The alarm unit adopts an acousto-optic alarm device, which can issue an alarm signal in time when a ground fault occurs.

The communication unit adopts wireless communication technology to upload the information of the detection system to the monitoring center, including an RF905 wireless receiving module and a wireless sending module, and the wireless receiving module can receive the control instructions of the monitoring center and perform the parameter setting. , the wireless sending module uploads the information of the detection system to the monitoring center.

The present invention also provides a detection method for a single-phase grounding detection system based on waveform difference, the detection method comprising the following steps:

Step (1): the voltage acquisition unit collects the voltage signals of each phase;

Step (2): The control and processing unit judges whether one phase of the phase voltage signal drops to zero, and the other two phases rise to the line voltage value, if so, go to step (3); if not, return to step (1) ;

Step (3): control the alarm unit to issue an alarm, and display the fault on the display screen: the phase corresponding to the phase voltage drop to zero has a ground fault;

Step (4): control the communication unit to upload the alarm information to the monitoring center;

Step (5): collect the zero-sequence current signals of all lines of the faulty phase, and record the zero-sequence current signal data of one cycle before and after the fault;

i_x(n)为x线路的零序电流信号，i_y(n)为y线路的零序电流信号，N为一个信号周期内的采样个数；Step (6): carry out pairwise correlation analysis on the zero-sequence current signals extracted from each line, and obtain the pairwise correlation coefficient between the lines:

i _x (n) is the zero-sequence current signal of the x line, i _y (n) is the zero-sequence current signal of the y line, and N is the number of samples in one signal cycle;

M为线路总数；Step (7): Calculate the comprehensive correlation coefficient of each line:

M is the total number of lines;

Step (8): the comprehensive correlation coefficient of each line is compared numerically to obtain the maximum value of the comprehensive correlation coefficient;

Step (9): the comprehensive correlation coefficient of each line is compared with the numerical value to obtain the minimum value of the comprehensive correlation coefficient;

Step (10): calculating the difference between the maximum value of the comprehensive correlation coefficient and the minimum value of the comprehensive correlation coefficient;

Step (11): judge whether the difference is greater than the difference reference value, if so, go to step (8); if not, go to step (9);

Step (12): judged as a bus failure, enter step (14);

Step (13): It is determined that the line where the difference between the minimum value of the comprehensive correlation coefficient is located is faulty, and the process proceeds to step (15).

Step (14): controlling the display screen to display the bus failure, and controlling the communication unit to upload the bus failure information to the monitoring center;

Step (15): control the display screen to display the line fault where the minimum difference value is located, and control the communication unit to upload the fault information to the monitoring center.

Compared with the prior art, the detection system first determines whether a ground fault occurs and the faulty phase according to the phase voltage signal, and then calculates the signal waveforms of the faulty line and the fault-free line according to the consistency principle of the zero-sequence current. Comparing with the above differences, the fault line can be accurately judged.

Description of drawings

FIG. 1 is a structural diagram of a single-phase grounding detection system based on waveform difference of the present invention.

Fig. 2 is a working flow chart of a detection method of a single-phase grounding detection system based on waveform difference of the present invention

Detailed ways

The specific implementation of a single-phase grounding detection system based on waveform difference of the present invention will be described in detail below with reference to the accompanying drawings.

As shown in Figure 1, the detection system of the present invention includes a zero-sequence current acquisition unit, a voltage acquisition unit, a control processing unit, a key input unit, a storage unit, a display unit, an alarm unit and a communication unit. The acquisition unit, the voltage acquisition unit, the key input unit, the storage unit, the display unit, the alarm unit and the communication unit are connected.

The zero-sequence current acquisition unit uses zero-sequence current sensors to collect zero-sequence current signals of all lines; the voltage acquisition unit uses voltage sensors to collect voltage signals of each phase.

The display unit adopts an LCD display screen, and cooperates with the key input unit and the storage unit to set the parameters of the detection system.

The alarm unit adopts sound and light alarm, which can send out an alarm signal in time when there is a ground fault.

The communication unit adopts wireless communication technology to upload the information of the detection system to the monitoring center, including RF905 wireless receiving module and wireless sending module. The wireless receiving module can receive the control command of the monitoring center and set parameters, and the wireless sending module uploads the information of the detection system. to the monitoring center.

As shown in FIG. 2, a detection method of a single-phase grounding detection system based on waveform difference of the present invention includes the following steps:

Step (1): the voltage acquisition unit collects the voltage signals of each phase;

Step (2): the control processing unit judges whether the phase voltage signal appears to drop to zero in one phase, and the other two phases rise to the line voltage value, if so, enter step (3); if not, return to step (1);

Step (3): control the alarm unit to issue an alarm, and display the fault on the display screen: the phase corresponding to the phase voltage drop to zero has a ground fault;

Step (4): the control communication unit uploads the alarm information to the monitoring center;

Step (5): collect the zero-sequence current signals of all lines of the faulty phase, and record the zero-sequence current signal data of one cycle before and after the fault;

i_x(n)为x线路的零序电流信号，i_y(n)为y线路的零序电流信号，N为一个信号周期内的采样个数；Step (6): carry out pairwise correlation analysis on the zero-sequence current signals extracted by each line, and obtain the pairwise correlation coefficient between the lines:

i _x (n) is the zero-sequence current signal of the x line, i _y (n) is the zero-sequence current signal of the y line, and N is the number of samples in one signal cycle;

M为线路总数；Step (7): Calculate the comprehensive correlation coefficient of each line:

M is the total number of lines;

Step (8): the comprehensive correlation coefficient of each line is compared with the numerical value to obtain the maximum value of the comprehensive correlation coefficient;

Step (9): the comprehensive correlation coefficient of each line is compared with the numerical value to obtain the minimum value of the comprehensive correlation coefficient;

Step (10): calculate the difference between the maximum value of the comprehensive correlation coefficient and the minimum value of the comprehensive correlation coefficient;

Step (11): judge whether the difference is greater than the difference reference value, if so, go to step (8); if not, go to step (9);

Step (12): judged as a bus failure, enter step (14);

Step (13): It is determined that the line where the difference between the minimum value of the comprehensive correlation coefficient is located is faulty, and the process proceeds to step (15).

Step (14): control the display screen to display the bus failure, and control the communication unit to upload the bus failure information to the monitoring center;

Step (15): control the display screen to display the fault of the line where the minimum difference value is located, and control the communication unit to upload the fault information to the monitoring center.

The difference reference value is determined according to the total number of system lines, and the general value is

When a single-phase grounding fault occurs, on the one hand, the staff must manually select the line, and the power distribution line without single-phase grounding fault must be cut off, interrupting the normal power supply and affecting the reliability of power supply. On the other hand, single-phase grounding occurs. The power distribution line will be out of operation. In the process of finding fault points and eliminating faults, the normal power consumption of users cannot be guaranteed, especially in the crop growth period, harsh weather conditions such as strong wind, rain and snow, and complex areas such as mountainous areas and forest areas, as well as at night. It is not conducive to finding and eliminating faults, and will cause long-term and large-scale power outages, which will have a greater impact on the reliability of power supply. The above detection method can quickly and accurately determine whether a ground fault has occurred and the correct line, reducing the need for power outage processing. Power supply range to ensure normal power supply for ungrounded lines.

Finally, it should be noted that the technical solutions of the present invention are only described in conjunction with the above embodiments, but not limited thereto. Those skilled 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 all within the protection scope of the pending claims.

Claims (6)

1. The single-phase grounding detection system based on waveform difference is characterized by comprising a zero-sequence current acquisition unit, a voltage acquisition unit, a control processing unit, a key input unit, a storage unit, a display unit, an alarm unit and a communication unit, wherein the control processing unit is respectively connected with the zero-sequence current acquisition unit, the voltage acquisition unit, the key input unit, the storage unit, the display unit, the alarm unit and the communication unit; the detection system judges the earth fault phase according to the acquired signals, and then judges the earth fault line according to the difference of zero sequence current in the earth fault.

2. The system according to claim 1, wherein the zero-sequence current acquisition unit acquires zero-sequence current signals of all lines by using a zero-sequence current sensor; the voltage acquisition unit adopts a voltage sensor to acquire voltage signals of each phase.

3. The system according to claim 1, wherein the display unit is an LCD display screen, and the key input unit and the storage unit are used to set parameters of the detection system.

4. The system for detecting the single-phase grounding based on the waveform difference as claimed in claim 1, wherein the alarm unit employs an audible and visual alarm, and can send out an alarm signal in time when a grounding fault occurs.

5. The system according to claim 1, wherein the communication unit uploads the information of the detection system to a monitoring center by using a wireless communication technology, and the system comprises an RF905 wireless receiving module and a wireless transmitting module, the wireless receiving module can receive the control command of the monitoring center and perform the parameter setting, and the wireless transmitting module uploads the information of the detection system to the monitoring center.

6. The detection method of the single-phase grounding detection system based on the waveform difference as claimed in any one of claims 1 to 5, wherein the detection method comprises the following steps:

step (1): the voltage acquisition unit acquires voltage signals of each phase;

step (2): the control processing unit judges whether one phase of the phase voltage signals is reduced to zero, the other two phases of the phase voltage signals are increased to the value of line voltage, if yes, the step (3) is carried out; if not, returning to the step (1);

and (3): controlling the alarm unit to give an alarm, and displaying a fault on the display screen: a phase corresponding to zero phase voltage drop has a ground fault;

and (4): controlling the communication unit to upload alarm information to the monitoring center;

and (5): acquiring zero-sequence current signals of all lines of a fault phase, and recording zero-sequence current signal data of each period before and after the fault;

and (6): and carrying out pairwise correlation analysis on the zero sequence current signals extracted by each line, and solving pairwise correlation coefficients between the lines:i_x(n) is zero sequence current signal of x line, i_y(N) is a zero sequence current signal of the y line, and N is the sampling number in one signal period;

and (7): calculating the comprehensive correlation coefficient of each line:

m is the total number of lines;

and (8): comparing the numerical values of the comprehensive correlation coefficients of all lines to obtain the maximum value of the comprehensive correlation coefficients;

and (9): comparing the numerical values of the comprehensive correlation coefficients of all lines to obtain the minimum value of the comprehensive correlation coefficients;

step (10): calculating the difference value between the maximum value of the comprehensive correlation coefficient and the minimum value of the comprehensive correlation coefficient;

step (11): judging whether the difference value is larger than a difference value reference value or not, if so, entering a step (8); if not, entering the step (9);

step (12): judging that the bus is in fault, and entering the step (14);

step (13): and (5) judging that the line fault is the line fault where the minimum value difference value of the comprehensive correlation coefficient is positioned, and entering the step (15).

Step (14): controlling the display screen to display bus faults and controlling the communication unit to upload bus fault information to the monitoring center;

step (15): and controlling the display screen to display the line fault where the minimum difference value is located, and controlling the communication unit to upload fault information to the monitoring center.

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