CN106229239A - Control demarcation circuit breaker trip method and demarcation circuit breaker - Google Patents

Abstract

The invention relates to a method for controlling the tripping of a boundary circuit breaker and a boundary circuit breaker, including a sampling circuit, a filter circuit and a detection circuit, which respectively collect, filter and detect two kinds of frequency signals of the line, and the boundary circuit breaker also includes a circuit breaker according to the detection output The results are calculated by the calculation unit of the dual-frequency measurement current ratio, the judgment unit for judging whether there is a single-phase ground fault in the next stage of the boundary circuit breaker according to the calculation results, and the communication module that transmits the judgment results and calculation results to the monitoring system. By sampling the two frequencies and calculating their signal ratio, it can be judged whether there is a single-phase ground fault, which can realize local judgment and improve the accuracy. In addition, it can directly report the fault point, upload less data, and have high accuracy, and report the fault directly. The point system fault location detection method is simpler, and the fault point location is effective.

Description

Controlling boundary circuit breaker tripping method and boundary circuit breaker

technical field

The invention relates to a method for controlling tripping of a boundary circuit breaker and the boundary circuit breaker.

Background technique

At present, the boundary circuit breaker comprehensively judges whether there is a single-phase ground fault through the power frequency zero-sequence current data reported to the monitoring system. Using this method, the system structure is complicated. And because only the power frequency zero-sequence current signal is collected, the power frequency zero-sequence current of all lines changes, and the length of the lines is different, and the non-fault current may be larger than the fault current, which leads to inaccurate measurement. In addition, the collected The amount of signal data is relatively large, and the probability of disconnection in the GPRS transmission method is relatively high, which will cause data loss, and the reported information will be inaccurate. In addition, the boundary circuit breaker cannot be judged on the spot, and it needs to be confirmed by the monitoring system to issue instructions from the background. make the wiring more complicated.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a method for controlling the tripping of the boundary circuit breaker and a boundary circuit breaker, which can improve the accuracy and realize on-site judgment , so that the system fault location detection method is simpler, and the fault point location is effectively performed.

The technical scheme that the present invention solves above technical problem is:

The method for controlling the tripping of the boundary circuit breaker includes the following steps: collecting and calculating the zero-sequence current component of the system, judging whether the power frequency zero-sequence current is greater than the zero-sequence protection setting value, judging whether the direction of the zero-sequence current changes, collecting and calculating the first injection frequency signal and the first injection frequency signal Two injection frequency signal values and their signal ratio difference, judge whether there is a fault problem according to the ratio difference between the first injection frequency and the second injection frequency signal, if two or more conditions are met, then control the boundary circuit breaker to trip.

The boundary circuit breaker includes a sampling circuit, a filter circuit and a detection circuit, which respectively collect, filter and detect the power frequency and two frequency signals of the line, and calculate the ratio of the dual-frequency measurement current and the calculation of the zero-sequence current component according to the detection output results unit, the boundary circuit breaker also includes whether the power frequency zero-sequence current is greater than the zero-sequence protection setting value, whether the direction of the zero-sequence current changes, and judging whether there is a fault problem according to the signal ratio difference between the first injection frequency and the second injection frequency and whether A judging unit that satisfies two or more conditions for judging, and a control unit that controls the tripping of the boundary circuit breaker according to the judging result.

The beneficial effects of the present invention are: by sampling the two frequencies, calculating their signal ratio, and comprehensively judging whether there is a single-phase grounding fault through the zero-sequence current component of the power frequency, the local judgment can be realized and the accuracy can be improved. In addition, it can be directly reported Fault points, less uploaded data, high accuracy, simpler detection methods for fault points, and effective fault location.

Description of drawings

Fig. 1 is the functional block diagram of circuit breaker circuit of the present invention;

Fig. 2 is the software flow chart of the method for tripping the control boundary circuit breaker of the present invention;

Fig. 3 schematic block diagram of the sampling filter circuit of the demarcation circuit breaker of the present invention;

Fig. 4 is a schematic circuit diagram of a single-phase ground fault detection method of the present invention;

Fig. 5 is a circuit schematic diagram of the low excitation impedance transformer grounding protection device of the present invention.

detailed description

Example 1

As shown in Figure 4, it is the circuit principle diagram of the single-phase ground fault detection method of the present invention, the single-phase ground fault detection principle of injecting dual-frequency characteristic signal through the low excitation impedance transformer is as follows: when a single phase ground fault occurs, the low excitation impedance transformer The grounding device operates to implement parallel shunt protection in the fault phase. The dual-frequency detection signal is injected through the low excitation impedance transformer. At this time, the low excitation impedance transformer is the signal voltage source, and the detection signal only exists in the fault phase.

Under one frequency action there are:

I1=U/Xc1+U/Xc2+U/R

I2=U/Xc2

Among them, U is the injected signal voltage, Xc is the line capacitive reactance, and R is the grounding resistance;

Change the frequency of the injected signal and keep the voltage of the injected signal constant. Since the capacitive reactance is inversely proportional to the frequency, k is the ratio of the two frequencies. At this time:

I11=k.U/Xc1+k.U/Xc2+U/R

I21=k.U/Xc2

The two frequency measurements are ratioed:

I11/I1=(k.U/Xc1+k.U/Xc2+U/R)/(U/Xc1+U/Xc2+U/R)! =k

I21/I2= (k.U/Xc2)/(U/Xc2)=k

The detection result of non-fault loop is the same as I2. For non-fault detection loops, the loop impedance is capacitive, and the current ratio is close to K. For fault detection loops, the loop impedance is resistive plus capacitive, and the current ratio is less than K. When the frequency of the injected signal is known, it is easy to distinguish Faulty loops and faulty sections.

The single-phase ground fault detection method of injecting dual-frequency signals through low-excitation impedance transformers, on the one hand, uses signal voltage sources to avoid traditional current source signal injection methods, which are affected by distributed capacitive reactance shunts, and the characteristics of fault loop signals are not obvious; on the other hand, dual-frequency The signal injection method, the single-phase grounding judgment is based on the ratio of the two frequency signal detection values, and is not affected by factors such as line properties, geographical conditions, boundary circuit breaker measurement accuracy, and installation interval distance.

Based on the above technical principles, the low excitation impedance transformer grounding protection device is as follows:

As shown in Figure 5, the low excitation impedance transformer grounding protection device includes a grounding protection cabinet and a secondary control panel. Primary equipment includes: single-phase circuit breaker, low excitation impedance transformer, zero-sequence current transformer, switch cabinet and related accessories; secondary equipment includes control panel 1, which is single-phase grounding protection control unit and signal generator and signal generator , The single-phase grounding protection control unit includes a single-phase grounding phase selection control unit, a grounding line selection unit and a drive blocking unit. It is the core part of the single-phase grounding comprehensive protection device of the distribution network, and realizes functions such as grounding phase selection, line selection, and fault phase impedance measurement. One end of the switches K1, K2, and K3 of the single-phase circuit breaker 2 are respectively connected to the busbar of the substation, and the other end is connected to the grounding network 6 through a low excitation impedance transformer. When the system is in normal operation, it is in the open state. It is an actuator that forces the faulty phase and the earth to be equipotential, and there are electrical and program locks between them. Under any circumstances, only one phase circuit breaker is allowed to close. The low excitation impedance transformer 3 includes three coils, which are primary coil W1, secondary secondary coil W2 and main secondary coil W3, wherein one end of the primary coil W1 is connected to the single-phase circuit breaker 2, and the other end is connected to the grounding grid 6; The secondary coil W2 is connected to the single-phase grounding protection control unit 1 for signal measurement; the main secondary coil W3 is connected to the signal generator 4 for coupling frequency signals. The control terminal of the signal generator is connected to the output terminal of the single-phase ground protection control unit, the signal generator is a signal generator capable of generating the second frequency, and the single-phase ground protection control unit includes a A storage unit for control instructions, and a processor unit for generating two-frequency processing instructions after the single-phase circuit breaker is closed. A processor unit that issues processing commands that generate two frequencies. According to the instruction of the single-phase grounding protection control unit, the signal generator injects two kinds of frequency signals into the system for fault location and automatic fault recovery. The two frequencies can be set as required, or both frequencies can be selected as high-frequency signals. The specific way in this embodiment is to use the first frequency as 75 Hz, the second frequency as 225 Hz, and the second frequency signal as a high-frequency signal. The zero-sequence current transformer 5 is installed on the connecting line between the low excitation impedance transformer and the ground grid, and is used for measuring the ground current flowing through the low excitation impedance transformer. The grounding condition of the single-phase grounding protection device in the distribution network determines the effect of the grounding protection. The device is required to be well connected to the grounding grid to minimize the grounding impedance. The ground phase selection control unit includes a first frequency filter circuit and a first detection circuit connected in series, and the first frequency filter circuit is a filter circuit capable of filtering two frequencies. In this embodiment, the filter circuit can use Two band-pass filters are connected in parallel, and the grounding phase selection control unit also includes a calculation unit for calculating the grounding impedance of the system according to the detection output result and a control unit for controlling the opening of the single-phase circuit breaker according to the calculation result.

Working process: single-phase ground fault location and isolation system injected by low excitation impedance transformer signal real-time acquisition of substation bus phase, line voltage, zero-sequence voltage, judging whether there is single-phase grounding in the system according to the change of model angle between zero-sequence voltage and line voltage Fault and grounding phases, when a single-phase grounding fault occurs, control the corresponding phase single-phase grounding circuit breaker (K1, K2, K3) to quickly close, and after the corresponding phase single-phase circuit breaker is closed, force the fault phase to ground Equipotential, to achieve extinguishing the grounding arc, while providing effective protection for personal induction, to avoid personal injury accidents. When the grounding property is intermittent grounding, this device can transform the unstable grounding into a steady metal grounding to avoid intermittent overvoltage.

The grounding protection line selection unit records waves before and after the action of the single-phase grounding circuit breaker. According to the change of the zero-sequence current of each line before and after the closing of the split-phase circuit breaker, the zero-sequence current characteristic equation is used to determine the grounding fault line.

After the single-phase circuit breaker is closed, after a set time delay, the signal generator is started, and a special frequency voltage is injected into the system through the main secondary coil W3 of the low excitation impedance transformer connected to the signal generator to generate a grounding current, and the grounding phase is selected. The control unit collects the voltage and current signals fed back by the secondary coil W2 of the low excitation impedance transformer, separates the injected special frequency signals, and calculates the change of the system grounding impedance. The phase control unit controls the opening of single-phase circuit breakers (K1, K2, K3) to realize automatic recovery of single-phase grounding faults.

Specific embodiments of the present invention are as follows: as shown in Figures 1 to 3, the boundary circuit breaker includes a sampling circuit, a filter circuit and a detection circuit, which respectively collect, filter and detect the power frequency and two frequency signals of the line, The filter circuit adopts the parallel output mode of two narrow-band filters, as shown in Figure 3, it can also be realized by connecting the analog filter and the digital filter in series, and also includes calculating the dual-frequency measurement according to the detection output result The calculation unit of the current ratio and the zero-sequence current component, the boundary circuit breaker also includes whether the power frequency zero-sequence current is greater than the zero-sequence protection fixed value, whether the zero-sequence current direction changes, according to the first injection frequency and the second injection frequency signal The ratio difference judges whether there is a fault problem and whether two or more conditions are met, and the judgment unit is used for judging, and the control unit is used to control the tripping of the boundary circuit breaker according to the judgment result. It also includes a communication module for sending the judgment result to the monitoring system.

As shown in Figure 3, it is a schematic block diagram of the sampling filter circuit of the boundary circuit breaker, which is an embodiment of the second filter of the present invention. In view of the current situation that the detection is difficult due to severe interference, a method for detecting injected signals combining analog filtering and digital filtering is studied, and the analog filter and digital filter are designed respectively. The method has high sensitivity and reliability, and can fully meet the requirements of field application. This method can accurately separate the 1mA injection current signal from the power frequency 5A current signal and perform effective calculation. The sensor circuit is a CT sampling circuit, the secondary filter amplifier circuit is the same as the filter amplifier circuit, and the addition circuit superimposes the negative half cycle filter signal to the positive half cycle, and through the above hardware circuit, the required signal is sent to the AD module of the CPU. CPU calculation analysis. After the analog signal volume is collected, it is filtered by DC and harmonics, and then the frequency component of the injected signal is extracted by digital narrowband bandpass filter for fast Fourier calculation. After filtering, fast Fourier transform can accurately calculate the effective value of incoming and outgoing signals.

Example 2

As shown in Figures 1 to 3, 1. The method for controlling the tripping of the boundary circuit breaker includes the following steps:

1) Collect and calculate the zero-sequence current component of the system,

2) Determine whether the power frequency zero-sequence current is greater than the start-up value, if it is greater than the start-up value, then perform step 3) if it is less than the start-up value, then perform step 1),

4) Determine whether the power frequency zero-sequence current is greater than the zero-sequence protection setting value,

5) Determine whether the direction of the zero-sequence current changes,

6) Acquisition and calculation of the first injection frequency signal and the second injection frequency signal value and their signal ratio difference,

7) Judging whether there is a fault problem according to the signal ratio difference between the first injection frequency and the second injection frequency,

8) Judging whether two or more conditions are satisfied, if so, control the boundary circuit breaker to trip, if not, end the program.

9) Send the judgment result to the monitoring system.

In fact, in the execution process of steps 1) to 8), some of the steps can be performed in any order except that there is a front-to-back execution relationship. Therefore, the present invention also has many related variant embodiments, all of which belong to the protection scope of the present invention.

Example 3

As shown in Figures 1 to 3, the method for controlling the tripping of the boundary circuit breaker includes the following steps: collecting and calculating the zero-sequence current component of the system, judging whether the power frequency zero-sequence current is greater than the zero-sequence protection setting value, judging whether the direction of the zero-sequence current changes, Collect and calculate the value of the first injection frequency signal and the second injection frequency signal and their signal ratio difference, judge whether there is a fault problem according to the ratio difference between the first injection frequency signal and the second injection frequency signal, if two or more conditions are met, Then the control demarcation circuit breaker trips.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements can also be made without departing from the technical principle of the present invention. and modifications, these improvements and modifications should also be considered as the protection scope of the present invention.

Claims (5)

1. control demarcation circuit breaker trip method, it is characterised in that: comprise the steps: that gathering calculating system zero-sequence current divides Amount, it is judged that whether power frequency zero-sequence current is more than zero-sequenceprotection definite value, it is judged that whether zero-sequence current direction changes, and gathers calculating first Injected frequency signal and the second injected frequency signal value and signal ratio thereof, believe according to the first injected frequency and the second injected frequency Number ratio determines whether failure problems, if meeting two or more condition, then controls demarcation circuit breaker tripping operation.

Control demarcation circuit breaker trip method the most according to claim 1, it is characterised in that；If less than initiation value, then Continue to gather calculating system zero-sequence current component.

Boundary open circuit trip method the most according to claim 1 and 2, it is characterised in that: also comprise the steps: will determine that Result sends to monitoring system；Demarcation circuit breaker tripping operation is controlled by monitoring system.

4. demarcation circuit breaker, it is characterised in that: including sample circuit, filter circuit and testing circuit, they are respectively to circuit Power frequency and two kinds of frequency signals are acquired, filter and detect, according to detection output result computing double frequency measure current ratio and The arithmetic element of zero-sequence current component, it is the most fixed more than zero-sequenceprotection that described demarcation circuit breaker also includes power frequency zero-sequence current Whether value, zero-sequence current direction change, judge whether faulty according to the first injected frequency and the second injected frequency signal ratio Problem and whether meet the judging unit that two or more condition carries out judging, and control point according to judged result The control unit of boundary's circuit breaker trip.

Demarcation circuit breaker the most according to claim 4, it is characterised in that: also include will determine that result sends to monitoring system Communication module.