KR940003002B1 - Over current relay - Google Patents

Abstract

The digital circuit breaker is designed according to an IEC 225 restrictions and is operated by user defined functions. The digital circuit breaker includes a phase current detector (10) for detecting current levels of phases, an A/D converter (30) for converting current level into digital level, a switch unit (50) for setting rated current, instantaneous condition of circuit breaking and trip time, a dip switch (70) for selecting characteristic curve of overload and earth, a comparator (90) for comparing the reference current level with the detected current level, a current level display (120) for displaying current data, and a control signal generator (140) for generating control signal according to control data transmitted from a CPU (40).

Description

Digital overcurrent relay

1 is a conventional digital overcurrent relay circuit diagram.

2 is a block diagram of a digital overcurrent relay according to the present invention.

3 is a detailed circuit diagram of a digital overcurrent relay according to the present invention.

4 is an overcurrent detection characteristic curve according to the present invention.

* Explanation of symbols for main parts of the drawings

10: phase current detector 11-1 to 14-1: burden circuit

12-1 to 14-2: Rectification section 11-3 to 14-3: Filter section

20: gain control unit 30: analog / digital conversion unit

40: central processing unit 50: switch unit

60: pyrom 70: dip switch unit

80 latch 90 comparison unit

100: fault display drive unit 110: fault display unit

120: current display driver 130: current display

140: control signal generator

The present invention relates to a digital overcurrent relay, and in particular, that the characteristic curve of the overcurrent with respect to the rated current is in accordance with the characteristic curve of the international standard (IEC 225), and is suitable for the overload protection of the switchgear system against the overcurrent by using three-phase and ground fault Digital overcurrent relay.

In general, the power system protects the entire system from the terminal for the purpose of protecting power plant protection, transmission line protection, bus line protection, transformer protection and substation protection by dividing into accident point detection, accident section, accident type, etc. The system is configured to protect and monitor the power system from various accidents. These are recently in the electronic stage of the transition phase, the present invention is a device for the three-phase over-current protection installed in the distribution board used in the feeder (end feeder) of these, the protection here is the over-current to the rated current Compared according to size, it means tripping operation in trip area designed to fit characteristic curve.

In the conventional relay, a method of comparing the primary side current with a reference value after detecting the magnitude of the current using a current transformer (CT), an analog method, an induction disk (Electro-magmetic), etc. are used. In this method, after converting the output of the current transformer into a voltage source and converting it into a DC current, the RC integrator detects the current stably, and compares the detected current with a reference value through a comparator to detect an overload, but varies the reference value. It is possible to estimate the overcurrent curve by the operation value according to the size. In addition, the induction disk type is a mechanical configuration, and since the magnitude of the current detected in the current transformer is proportional to the magnetic flux density, the disk is rotated by the magnitude of the magnetic flux density. Most of the domestic relays (about 90%) use the induction disk type. I use it.

However, in such an induction disk type or analog type, there is a problem in that it does not exactly comply with the international relay standard (IEC 255-1C), the size of the installation part increases, and the user cannot easily control the desired control characteristics.

Therefore, in recent years, digital relays have been developed and are widely used, which detects currents through current transformers, converts them into voltage sources, converts them into DC currents, filters input signals, and samples / holds. After converting the digital signal through an analog-to-digital converter, the digital signal is processed by the central processing unit to satisfy the characteristic curve of the general requirements required by the relay standard (IEC 255-4).

FIG. 1 is a conventional digital overcurrent relay circuit diagram, as shown here, a current transformer CT for detecting current from the line L, and a rectifier circuit for rectifying the output signal of the current transformer 1. 2) and the A / D converter 3 which converts the output signal of the rectifier circuit 2 into a digital signal, and the output signal of the A / D converter 3 to a reference value to detect overcurrent according to the program. A central processing unit (4), a correction circuit (5) for setting a reference value to the central processing unit (4), a ROM (6) storing a program for overcurrent detection, and the center A RAM 7 for storing data during program execution of the processing device 4, an output circuit 8 for performing control output upon detection of an overcurrent of the central processing device 4, and the A / D converter. A register (9) which receives the output signal of (3) and stores the maximum value among the previous values, and an output signal of the register (9) The digital comparator 10 was configured to receive the output signal of the A / D converter 3 and output the enable signal to the register 9 only when the output signal of the A / D converter 3 is large. .

In the conventional digital overcurrent relay circuit configured as described above, the current flowing in the line L is detected by the current transformer 1, rectified by the rectifier circuit 2, and then converted into digital data by the A / D converter 3 to be processed centrally. Input to the device 4. At this time, since the reference data for overcurrent detection is set in the correction circuit 5, the central processing unit 4 uses the overcurrent detection program of the ROM 6 and the reference data of the correction circuit 5 and the A / D converter 3 Compared to the current detection data, the control output is output to the output circuit 8 when the over current is detected. Accordingly, the output circuit 8 performs the trip and display control output according to the over current detection. Since the digital comparator 10 compares the previous maximum value with the current detection data and enables the register 9 when the current value is large, the register 9 is stored with the maximum value updated, and the register 9 is stored therein. The central processing unit 4 reads the maximum value stored in the memory, and uses it for overcurrent detection and control output calculation, and displays the maximum value.

However, in the conventional digital overcurrent relay circuit, there is a problem that each unit must be installed for each phase in order to detect and control the overcurrent of each of the R, S, and T phases, and to set a reference value through the correction circuit 5. However, since the correction circuit 5 initially sets the reference value, it is not possible to adjust the overcurrent detection characteristic curve according to the load condition, and thus there is a problem that the desired control characteristic cannot be easily adjusted.

An object of the present invention is to monitor and control the fault current of three phases (R, S, T phase) and the overload of ground fault (N phase) as one unit, satisfy the characteristic curve conforming to the international standard and provide instantaneous function It is to provide a digital overcurrent relay that has an exaggerated time function and can satisfy the desired control characteristics.

According to the present invention having the above object, rectifying and filtering the currents of the respective firms detected through the current transformer are input to adjust the gain according to the magnitude of the analog signal, and the user sets the reference value set through the dip switch. ) And the reference value and the digitally converted current detection value are compared and processed. If an error occurs in the corresponding phase, the corresponding fault is displayed, and the current value is displayed through 7 segments, causing the user to cause trouble. It is achieved by configuring a digital overcurrent relay circuit so as to find quickly, it will be described in detail with reference to the accompanying drawings as follows.

FIG. 2 is a block diagram of a digital overcurrent relay according to the present invention, and FIG. 3 is a detailed circuit diagram of the digital overcurrent relay according to the present invention. A phase current detection unit 10 for receiving a current of N phase) (INPUT1 to INPUT4), applying a current load, and then rectifying and filtering the current, and a gain adjusting unit for adjusting the gain of each phase output signal outputted from the phase current detection unit 10. (20) and the analog / digital conversion section 30 for sampling / holding the output signal of the gain adjusting section 20 and converting the signal into digital data, and for the user to set the rated current, instantaneous conditions, trip time, and the like. A switch unit 50, an EPROM 60 for storing the setting value of the switch unit 50 even when the power is turned off, and a dip switch unit 70 for selecting an overload and ground fault characteristic curve. ) And the output signal of the dip switch unit 70 The latch 80 to latch, the output signal of the latch 80, the output signal of the switch unit 50, and the like are input, and the current detection value of each phase of the analog / digital conversion unit 30 is input to detect the overcurrent. The central processing unit which performs display control, etc., the comparing unit 90 which receives and compares the detection current data and the reference data from the central processing unit 40, and the output data of the comparing unit 90, Drives 110 and receives current data from the fault display driver 100 for outputting the gain control signals add-1 and addr-2 of the gain control unit 20 and the central processing unit 40. The current display driver 120 driving the current display unit 130 and the control data of the CPU 40, the current display unit 130, the current display driver 120 and the dip switch unit 70 and The control signal generator 140 controls the operation of the latch unit 80.

Here, the phase current detector 10 selects a resistance value by the dip switch signals dip-1 and dip-2 to charge the three-phase current inputs INPUT1 to INPUT3 and the N-phase input INPUT4 current. Rectifier 11-2 for full-wave rectifying the input burden circuits 11-1 to 13-1 and 14-1 and the output signals of the burden circuits 11-1 to 13-1 and 14-1. 14-2) and filter sections 11-3 to 14-3 for filtering the output signals of the rectifiers 11-2 to 14-2.

The gain adjusting unit 20 includes selectors 20-1 and 20-2 which generate gain control signals by the addresses addr-1 and addr-2 of the display driver 100; Gain control by the gain control signals of the selectors 20-1 and 20-2 to amplify the output signals of the filter units 11-3, 12-3, 13-3, 14-3, respectively. And amplifying sections 21, 22, 23, and 24 for outputting.

The analog / digital conversion unit 30 includes an interface 31 for receiving a current detection output signal from the gain adjustment unit 20 under the control of the central processing unit 40, and the interface 31. A / D for sampling / holding the output signal of the sample / hold circuit 32 and for outputting the sample / hold signal to the sample-hold circuit 32 and for converting the sampled / held current detection signal into digital data. The converter 33 is comprised.

The dip switch unit 70 includes a dip switch DIP-1 for selecting an overload characteristic and a dip switch DIP-2 for selecting a characteristic for the ground current.

The fault display unit 110 is configured to display faults of the corresponding lines (three phases and ground faults) through the light emitting diodes, and the current display unit 130 is controlled by the central processing unit 40. It is configured to display the current fault current value through 7 segments according to the set characteristic.

Referring to the operation and effects of the present invention configured as described above are as follows.

First, currents of the respective phases R, S, T, and N are detected through the current transformer CT and input to the phase current detection unit 10 of FIG. 3 according to the present invention. The load circuits 11-1 to 14-1 of the phase current detection unit 10 apply current loads with variable resistors and resistors, respectively, at this time, depending on the characteristic values set in the dip switches DIP-1 and DIP-2. The relays RELAY SPDT are controlled by the control signals dip-1 and dip-2 to adjust the input bias of three phases (R, S, T phase) and N phase. After that, fine adjustment is made by adjusting the variable resistors respectively, and the Zener diodes ZNR1 to ZNR4 are connected to the burden circuits 11-1 to 14-1, respectively, and when the burden is changed, the current transformer is opened and destroyed instantaneously. Prevent what can be.

The current detection signals input through the burden circuits 11-1 to 14-1 are full-wave rectified through the rectifiers 11-2 to 14-2, respectively, and through the rectifiers 11-2 to 14-2. The full-wave rectified signal is filtered through the filter units 11-3 to 14-3 and input to the gain adjusting unit 20.

The gain adjusting unit 20 is controlled by the central processing unit 40 and is selected by the selectors 20-1 and 20-2 by the addresses addr-1 and addr-2 of the display driver 100. ) Generates a gain control signal, and the amplification sections 21, 22, 23, and 24 provide the filter sections 11-3, 12- by the gain control signals of the selectors 20-1, 20-2. 3) and amplify the output signals of (13-3, 14-3) and output them (output 1 to output 4). Here the gain is set to 2Hz.

The detection current value of each phase that is gain-adjusted and output by the gain adjusting unit 20 is converted into digital data by the analog / digital conversion unit 30 and input to the central processing unit 40. The analog / digital conversion unit 30 ), The interface unit 31 selects and outputs the current value of each phase input through the gain adjusting unit 20 at a predetermined period under the control of the central processing unit 40, and is inputted through the interface unit 31. The current value is sampled and held in the sample / hold circuit 32 and converted into digital data in the analog / digital converter 33. That is, under the control of the central processing unit 40, the analog digital conversion unit 30 receives the current detection values of the R, S, T, and N phases at predetermined cycles and converts the digital data into digital data.

On the other hand, the central processing unit 30 sets each set value through the switches SW1-SW6, and the test, reset, increase, 7-segment shift, and light emitting diodes are selected for selection of rated current, instantaneous condition and trip time. To set the movement, mode selection, etc., the setting value of the switch unit 50 is erased at power-off so as to remove the hassle that needs to be reset. A characteristic curve is selected through 70, wherein the first dip switch DIP-1 selects the overload characteristic curve and the second dip switch DIP-2 selects the characteristic curve for the ground current.

Therefore, the central processing unit 40 calculates the detection current data output from the analog / digital conversion unit 30 and reference data according to control characteristics set by the dip switch unit 70 and the switch unit 50 to detect the overcurrent. Control. That is, under the control of the central processing unit 40, the output data of the analog / digital conversion unit 30 is buffered through the buffer 91 of the comparator 90 and input to one side input of the comparator 92. The reference data of the central processing unit 40 is input to the comparison input of the comparator 92 and compared. Accordingly, when the overcurrent detection output signal is generated in the comparator 90, the faulty display driver 100 drives the light emitting diode of the fault display unit 110 to display the corresponding fault, and the central processing unit 40 is then displayed. The control signal addr-1 or addr-2 for gain selection of the gain adjusting unit 20 is output from the driver 102 of the fault display driver 100 by the data according to the set characteristic curve to make the gain selection. do.

In addition, when a fault is detected and a fault is displayed, the current display unit 130 is driven through the current display driver 120 to display a fault current value. That is, the current display is controlled by the central processing unit 40 through the control signal generation unit 140 to output the current value at the time of failure by the value set by the user through the dip switch, and displayed through the 7-segment. do.

4 is an overcurrent detection characteristic curve according to the present invention. As shown in the drawing, ① is set to move up and down in the characteristic curve of the long time, and ② is the case where the short time is set. It operates after trip time according to setting value. When ② is not set, it operates only in the long time of ①.

As described above, in the conventional relay, each installation of each phase is easy as one unit up to three phases and ground faults, and a number of existing units can be implemented as one unit, which facilitates inventory management, quality control, and the like. In addition, it has the effect of satisfying international standard (IEC 255-4), and it can also add up to the short-time performance by intercepting the instantaneous value according to the load condition by selecting the desired characteristic curve for each characteristic curve. It works.

Claims (6)

Phase current detection unit 10 for receiving current from each phase (R, S, T, N phases) through current transformer CT, receiving current load, and then rectifying and filtering the wave, and the phase current detection unit 10 A gain adjusting unit 20 for adjusting the gain of each phase output signal outputted from the control panel, an analog / digital conversion unit 30 for sampling / holding the output signal of the gain adjusting unit 20 and converting it into digital data, and a user. Switch unit 50 for setting the rated current, instantaneous condition, trip time, etc., ipirom 60 for storing the setting value of the switch unit 50 to be maintained even at power-off, overload and ground fault A dip switch unit 70 for selecting a characteristic curve, a latch 80 for latching an output signal of the dip switch unit 70, an output signal of the latch 80, and an output of the switch unit 50; Receives a signal lamp and receives the current detection value of each phase of the analog / digital converter 30 A central processing unit 40 for performing the flow detection and display control, a comparison unit 90 for receiving and comparing the detected current data and the reference data from the central processing unit 40, and the output of the comparison unit 90 The fault display driver 100 which drives the fault display unit 110 by data and outputs gain control signals addr-1 and addr-2 to the gain control unit 20 by the control data of the central processing unit 40. ), A current display driver 120 driving the current display unit 130 by receiving current data from the central processing unit 40, and the current display unit 130 by the control data of the central processing unit 40. And a current display driver (120), and a control signal generator (140) for controlling the operation of the dip switch unit (70) and the latch unit (80). According to claim 1, The phase current detection unit 10, the resistance value is selected by the dip switch signal (dip-1) (dip-2), the three-phase current input (INPUT1 ~ INPUT4) and N-phase input (INPUT4) Rectifying section for full-wave rectifying the burden circuits 11-1 to 13-1 and 14-1 receiving the electric current and inputting the output signals of the burden circuits 11-1 to 13-1 and 14-1, respectively. (11-2 to 14-2) and filter sections (11-3 to 14-3) for filtering the output signals of the rectifiers (11-2 to 14-2). The gain adjusting unit 20 includes: a selector 20-1 for generating a gain control signal by the gain control addresses addr-1 and addr-2 of the display driver 100; (20-2) and gain control by the gain control signals of the selectors 20-1 and 20-2 to control the filter units 11-3, 12-3, and 13-3, 14-3. Digital over-current relay, characterized in that composed of amplifying section (21, 22, 23, 24) for amplifying and outputting the output signal of each. The analog / digital converter (30) according to claim 1, further comprising: an interface (31) for receiving a current detection output signal from the gain adjuster (20) under the control of the central processing unit (40), and A sample / hold circuit 32 for sampling / holding an output signal of the interface 31 and a sample / hold signal are output to the sample-hold circuit 32, and the sample / holded current detection signal is converted into digital data. Digital overcurrent relay, characterized in that consisting of the A / D converter 33. The dip switch unit 70 is configured of a dip switch DIP-1 for selecting an overload characteristic and a dip switch DIP-2 for selecting a characteristic for a ground current. Digital high current relay. According to claim 1, wherein the fault display unit 110 is configured to display the fault of the corresponding line (three phases and ground fault) through the light emitting diode, respectively, and the current display unit 130 of the central processing unit 40 A digital overcurrent relay, characterized in that configured to display the current fault current value through seven segments in accordance with the characteristics set by the user by control.