CN201045627Y - Intelligent Power Line Fault Indicator - Google Patents

Abstract

An intelligent electric power line fault indicator of the utility model is used for detecting the short circuit and ground faults of the electric power line, which comprises a short circuit detecting circuit comprising an open current transformer, a bridge rectifying circuit, a low-pass filtering circuit and a historical current peaks holding and comparing circuit, a peak sequence comparing and braking circuit, a power-supplying direction detecting circuit comprising a zero-cross detecting circuit, a pulse shaping circuit and a counting circuit, a ground pulse detecting circuit comprising a band-pass circuit and a phase comparing circuit, and a central core logic processing unit comprising a micro power-consuming single chip microcomputer as the core. The utility model is mainly used to solve the problems that the false action is caused by the inverted transmission of the line when the fault indicator detects the short circuit, and the ground fault detection is not suitable for the loop-network power supply line.

Description

Intelligent Power Line Fault Indicator

Technical field:

The utility model relates to a power line fault indicating device, in particular to a power line fault indicator.

Background technique:

Line fault indicator is a device installed on overhead lines, power cables and switchgear busbars to indicate faulty circuits. Once a short circuit occurs in the power circuit, the line patrol personnel can quickly determine the fault section, branch, and fault point with the help of the red alarm display on the indicator. Completely change the backward method of blindly searching for wires in the past, and finding the faulty section by section closing. The main problems existing in power line fault indicators are as follows:

1. The increase of power cables on the line makes the distributed capacitance of the cable generate a capacitive discharge pulse to the fault point when a short-circuit fault occurs. The amplitude of this pulse is often very high, which may easily cause the indicator to malfunction.

2. The system load often has a large number of motors. When the line fails, these motors become generators due to the load inertia and send power backwards to the fault point or the system, which may also cause the fault indicator to malfunction.

3. At present, the first half-wave method is generally used to detect ground faults, that is, the first half-wave of the capacitive current at the moment of grounding is sampled and the first half-wave of the voltage at the moment of grounding, and their phases are compared. When the capacitive current at the moment of sampling grounding changes suddenly and is greater than a certain value, and When it is in phase with the first half wave of the voltage at the moment of grounding, it is considered that a ground fault has occurred. This method requires the fault indicator to be installed in a certain direction (such as towards the direction of the substation), otherwise the indicator cannot operate correctly, but in the distribution network line , due to the change of power supply capacity, load or load optimization, the action of load reversal will be frequently performed. When the load is reversed, the original power supply direction will change, resulting in the fault indicator that was originally installed correctly not working correctly. Therefore Such fault indicators are hardly available in practice.

Therefore, aiming at many imperfect problems existing in current fault indicators, the utility model provides an intelligent power line fault indicator.

Invention content:

The purpose of this utility model is to provide an intelligent power line fault indicator to solve the malfunction caused by the reverse power transmission of the line and the ground fault detection which is not suitable for the ring network power supply in the current fault indicator. A series of problems such as lines.

The technical solution adopted by the utility model to solve its technical problems is: the fault indicator is composed of a short-circuit current detection circuit, a peak sequence comparison circuit, a power supply direction detection circuit, a grounding pulse detection circuit and a core control circuit, and is characterized in that: short-circuit current The detection circuit, the peak sequence comparison circuit, the power supply direction detection circuit, and the ground pulse detection circuit are respectively electrically connected to the core control circuit, and the core control circuit makes a comprehensive judgment and indicates the fault line.

The working principle of the utility model: In the short-circuit detection circuit composed of open current transformer, bridge rectification, low-pass filter, historical current peak value holding and comparison circuit, rectification and low-pass filtering are used to eliminate high-frequency interference, and historical current peak value The keeper saves the previous peak value as the set value of the short-circuit current, and prepares to compare it with the value detected next time, thereby detecting the short-circuit current. When a short-circuit fault current is detected, the peak sequence comparison braking circuit starts to compare the magnitudes of adjacent peak values of the fault current one by one. If the magnitudes of adjacent peak values are relatively close, it is considered to be a real fault current, thus confirming the short-circuit fault. And an alarm signal is given by the central core logic processing unit. If the adjacent peak value is gradually decreasing, it is considered to be a short-circuit pulse current caused by reverse power transmission, and the central core logic processing unit will not give an alarm signal. The zero-crossing detection circuit in the power supply direction detection circuit changes the sine wave of current and voltage into a trapezoidal wave respectively, and the pulse shaping shapes the trapezoidal wave to make it into a square wave, and the two square waves respectively trigger the phase counting unit to count , and compare the value of the counter with the set value to determine the power supply direction. The ground pulse detection circuit composed of band-pass filter and phase comparison circuit is used to judge whether a single-phase ground fault occurs, and the central core logic processing unit makes a comprehensive judgment and indicates the fault circuit through the corresponding command sending unit and display circuit.

Compared with the prior art, the beneficial effect of the utility model is that it can solve the malfunction caused by the reverse power transmission of the line in the current short-circuit fault detection in the current fault indicator, and the ground fault detection is not suitable for a ring network power supply line and the like. series of questions.

Description of drawings:

Fig. 1 is the structural representation of the utility model

Fig. 2 is a block diagram of the utility model

Fig. 3 is the short-circuit current fault detection circuit diagram of the utility model

Fig. 4 is the braking circuit diagram of peak sequence comparison of the present utility model

Fig. 5 is the power supply direction detection circuit diagram of the utility model

Fig. 6 is the grounding pulse detection circuit diagram of the utility model

Fig. 7 is a diagram of filtering parameters of the grounding pulse detection circuit of the present invention

1 open current transformer (CT), 2 electric field signal pickup board, 3 signal processing board, 4 stepper motor

Detailed ways:

Below in conjunction with the accompanying drawings, the utility model intelligent power line fault indicator is further described:

As shown in Figure 1: the current signal of the utility model is taken from the opening CT (1) stuck on the wire, which is composed of a magnetically permeable material and a coil wound on it, and it can linearly convert the current signal on the power line into The voltage signal is processed by the logic circuit below. The electric field signal pickup board (2) is composed of a metal conductor and a voltage equalizing ring. It is in the electric field formed by the high-voltage wire. There is an alternating potential between it and the wire. Use it to pick up the electric field signal that is proportional to the voltage of the wire. . The signal processing board (3) processes and judges the current and electric field signals, converts them into corresponding logic signals and connects them to the central core logic processing control unit for comprehensive judgment processing. The stepper motor (4) consists of two sets of coils and a permanent The rotor of the magnet is composed of a fault identification plate installed on the rotor of the permanent magnet. The two sets of coils are the display coil and the reset coil. When the indicator detects that a fault occurs, the display coil is driven to attract the magnetic poles of the permanent magnet to its vicinity. As a result, it is in an alarm state. When the timing time is up, the reset coil is driven to act, and the magnetic pole of the permanent magnet is attracted to the vicinity of the reset coil, so that the indicator is in a reset state.

As shown in Figures 2, 3, and 4: the short-circuit current detection circuit is composed of an open CT, a bridge rectifier, a low-pass filter, and a peak value comparison circuit. The bridge rectification is completed by B1 in Figure 3, which converts the sinusoidal AC current signal into a pulsating DC signal, passes through the low-pass filter circuit composed of R1 and C1 to filter out some high-frequency interference on the line, and sends the signal to the peak hold circuit and peak comparator circuit. The peak hold circuit is composed of U1, C2 and A1. The core processing unit collects the peak value of the line every certain time, stores it in C2, uses A1 to perform impedance transformation, and outputs the signal to A2 for peak comparison to determine whether there is a short circuit pulse. Zener tubes D1, R3 and R2 form a potential shift voltage divider circuit, which makes the input signal greater than the characteristic voltage of D1 to be compared. R3 and R2 divide the signal to make the pulse current greater than a certain value of the load current. Generate a pulse signal. Usually the load current is less than the peak hold voltage Uh*(R2+R3)/R2+VD1, so the comparator outputs a high level, when a short circuit fault occurs, the current suddenly increases, and when it is greater than the above value, the comparator outputs a low level , thus giving a short-circuit pulse signal. But whether the signal is a real short-circuit pulse depends on the results of the peak sequence comparison braking circuit. As shown in Figure 4, U2 and C3 form the peak hold circuit of the n-1th cycle, U3 and C4 form the peak hold circuit of the nth cycle, and the central core logic processing unit generates the zero-crossing signal according to the voltage signal and the internal The timing circuit controls U2 and U3 to sample and hold near the current peak value through RC2 and RC3 respectively, and compares the switching gap between RC2 and RC3 to judge whether the short-circuit pulse is a real short-circuit pulse or a pulse caused by reverse power transmission. When power is supplied, the display will be locked and the short-circuit pulse flag will be cleared, thereby effectively preventing misoperation caused by non-fault factors such as reverse power transmission. Otherwise, it will be judged as a real short-circuit fault and trigger the flop circuit for display.

As shown in Figure 5: R4, R5, D2, D3, A5 and A6 in the power supply direction detection circuit form a zero-crossing detection circuit, in which D2 and D3 are mainly used to protect the input terminal of the amplifier from being damaged by negative voltage. When the input voltage is greater than zero, the amplifier outputs a high level, which is sent to the lower circuit for processing after being shaped by U6 and U7. C5, C6, CRY and U4 form a clock reference circuit to generate a 1MHz reference clock, which is sent to U5 as a 10-bit counting clock after 16 frequency division. When the current crosses the zero phase, the counter of U5 is cleared. At this time, U5 starts counting from 0. When the voltage zero crosses, an interrupt is applied to the central control processor, and the central control processor reads the count value of the counter to the memory. Then make a judgment to determine the power supply direction.

As shown in Figure 6, the two band-pass filters extract the current pulse and voltage pulse generated when the ground fault occurs and send them to the two interrupt application input terminals of RB1 and RB2 of the central core logic processing unit, and connect the circuit The flow direction is processed to determine whether a single-phase ground fault has occurred. The frequency characteristics of the filter are shown in Figure 7, the center frequency is selected as 5kHz, and the bandwidth is 500Hz.

Finally, the central core logic processing unit synthesizes the above multi-channel information, judges and indicates the fault line.

Claims (6)

1. Intelligent power line fault indicator, which is composed of short-circuit current detection circuit, peak sequence comparison circuit, power supply direction detection circuit, ground pulse detection circuit and central core logic processing unit, characterized in that: short-circuit current detection circuit , the peak sequence comparison circuit, the power supply direction detection circuit, and the ground pulse detection circuit are respectively electrically connected to the central core logic processing unit, and the central core logic processing unit makes a comprehensive judgment and indicates a fault. 2. The intelligent power line fault indicator as claimed in claim 1, characterized in that: the short-circuit current detection circuit consists of an open current transformer circuit, a bridge rectifier circuit, a low-pass filter circuit, a historical peak holding circuit and a peak comparison circuit Sequentially connected electrically. 3. The intelligent power line fault indicator as claimed in claim 1, characterized in that: the output signal of the short-circuit current detection circuit is connected to the peak sequence comparison circuit, and the peak sequence comparison braking circuit judges the waveform of the short-circuit current, when When it is judged to be a short-circuit waveform, the core control circuit will give an alarm signal, and it is judged to be a short-circuit fault; when the waveform is judged to be reversed power transmission, the core control circuit will not trigger the alarm circuit, thereby avoiding misjudgment caused by reverse power transmission. 4. The intelligent power line fault indicator according to claim 1, characterized in that: the power supply direction detection circuit is used to judge the power supply direction, and is composed of a zero-crossing detection circuit, a pulse shaping circuit and a counter circuit electrically connected in sequence. 5. The intelligent power line fault indicator according to claim 1, wherein the ground pulse detection circuit is used to judge whether a single-phase ground fault occurs, and is composed of a band-pass filter circuit, a pulse discrimination circuit and a phase comparison circuit. 6. The intelligent power line fault indicator according to claim 1, characterized in that: the central core logic processing unit is composed of a micro-power consumption single-chip microcomputer, an execution command sending unit and a display circuit.

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