KR20000006347U - Digital protective relay - Google Patents

Abstract

The present invention relates to a protection relay, and more particularly, to a digital protection relay for protecting a motor used as a power source of a factory. The device of the present invention is connected to a control panel including a key for setting a sequence input mode and a sequence interface to be connected to a PC. When the sequence input mode is set using the control panel, a PC can be used to input a sequence. And a microprocessor that receives and calculates a digital signal from an A / D converter and a digital processor for determining operation of a load when restarting after a power failure by a sequence input to the sequence interface. Since the plurality of relays are connected to each other, it is possible to operate according to the state of each relay. Therefore, the present invention allows the user to set the sequence with a PC or a PLC, and is easy to maintain, and can be used by connecting a plurality of relays to provide the effect of protecting the motor by operating in consideration of the load condition.

Description

Digital protective relay

The present invention relates to a protection relay, and more particularly, to a digital protection relay for protecting a motor used as a power source of a factory.

In general, the protective relay plays an important role to secure the reliability of the plant by monitoring the abnormality of the power system to prevent the impact of the accident in advance. Recently, according to the complexity and diversification of the plant facilities, digital protective relays have been developed that can be used for various purposes and to reduce wiring for easy installation, maintenance, and repair. In particular, the motor protection digital protection relay used as a power source of the factory can be largely divided into a monitoring function, a protection function, and a measurement function. Here, the main functions of protection and monitoring include overload, overcurrent, current shortage, phase loss and ground fault.The control functions include starting and running control of motors, switchgear control, restart sequence control after momentary power failure, and interlocking with external accidents. Operation control, etc.

Conventional digital protective relays required additional electrical work when the plant's equipment became more complex and needed to change existing control sequences. In addition, in the automatic restart after power failure, the motor is automatically restarted or not depending on the load characteristics, and the reference range of the instantaneous power failure is also set according to the mechanical inertia and the system. For example, in an automatic restart after a momentary power failure, the range of the instantaneous power failure can be set to 0 to 3 seconds, and when the power is restored after the power failure, the device restarts according to the automatic restart setting time. do. At this time, if the motor is restarted at the same time, the transformer on the top is temporarily overloaded due to the starting current. This problem has been solved by sequentially setting the restart time of the motor. However, it is dangerous to operate the state of the motor in operation by momentary power failure without judging the state of the load according to the set time, and in case of operating a large number of digital protection relays, it is simple to set the time when checking the relay interworking state. There was a problem in the operation method according to.

Accordingly, an object of the present invention is to allow a user to input a sequence program to solve the above problems, and to provide an input / output device and a communication function capable of interlocking a digital protective relay, according to a sequence input by the user. It is to provide digital protection relay that can be operated in integrated environment by restarting motor and providing motor and load status under digital protection relay to upper digital protection relay.

1 is a block diagram showing a digital protective relay according to an embodiment of the present invention;

2 is a configuration diagram using a plurality of relays of the device of FIG.

※ Explanation of code for main part of drawing

1 sensor input unit 2 first filter unit

3: first voltage detector 4: second voltage detector

5: phase detection part 6: overcurrent detection part

7: A / D conversion unit 8: microprocessor

9 self-diagnosis circuit 10: operation and display unit

11: local input / output unit 12: abnormal power detection unit

13: NETWORK 14: Serial Communication Port

15: ROM 16: RAM

17: Auto Save RAM 18: Sequence Interface

19: ground fault signal input unit 20: second filter unit

The digital protection relay according to the present invention for achieving the above object is connected to the operation unit including a key for setting the sequence input mode, the PC and the sequence interface is possible, when the sequence input mode is set using the operation unit, It receives and operates the sequence interface part that enables the input of the sequence using a PC and the digital signal of the A / D conversion part, and judges the load status when restarting after power failure by the sequence inputted to the sequence interface part. It includes a microprocessor to control the operation, and the network is installed, it is possible to operate according to the state of each relay by interconnecting a plurality of relays.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a digital protection relay according to an embodiment of the present invention, in which the first filter unit 2 is connected to a sensor input unit 1 that receives a current of a motor in the apparatus of FIG. 1. The first filter unit 2 inputs the filtered signal to the first voltage detector 3, the second voltage detector 4, the image detector 5, and the overcurrent detector 6, respectively, and then performs A / D conversion. The output is connected to the unit (7). Meanwhile, the A / D converter 7 is connected to receive the filtered signal of the second filter unit 20, and the second filter unit 20 is connected to the output terminal of the ground fault signal input unit 19. The microprocessor 8 is connected to the output terminal of the A / D conversion unit 7, and the self-diagnosis circuit unit 9 and the abnormal power supply detection unit 12 are connected to the input terminal of the microprocessor 8. In addition, the operation unit and the display unit 10 and the local input / output unit 11 are connected to the microprocessor 8 so as to enable input / output. In addition, the microprocessor 8 is connected to the ROM 15, the RAM 16, and the automatic storage RAM 17 through an internal bus, respectively, and a network 13 connecting a plurality of relays, and an external PC or PLC. Serial communication port 14 connected to the, and the sequence interface unit 18 is connected.

The operation of the digital protective relay according to the present invention configured as described above will be described with reference to FIG.

In the apparatus of FIG. 1, the sensor input unit 1 receives a current value flowing through a motor, converts it into a voltage value, and outputs it to the first filter unit 2. The first filter unit 2 filters the noise from the input signal and transmits the filtered signal to the first voltage detector 3, the second voltage detector 4, the imaging detector 5, and the overcurrent detector 6. Output each. In order to use the dynamic range of the A / D converter 7 widely, the first voltage detector 3 and the second voltage detector 4 detect an appropriate voltage value from a small value and a large value of the input signal. Output to D conversion section 7. In addition, the image detection unit detects an image formation from the filtered signal input from the first filter unit 2 and outputs an image presence / absence signal to the A / D conversion unit 7, and the overcurrent detection unit 6 detects the overcurrent to detect the overcurrent. The value is held and the overcurrent detection signal is output to the A / D converter 7. Meanwhile, the ground fault signal input unit 19 processes a signal input from an image current transformer (not shown) and outputs the signal to the second filter unit 20. The second filter unit 20 outputs a ground fault signal to the A / D converter. Output to (7). The A / D converter 7 receives the signals and converts the signals into digital data and outputs them to the microprocessor 8, and the microprocessor 8 calculates them. The self-diagnosis circuit unit 9 monitors the software runaway occurring during the operation of the microprocessor 8 and diagnoses the hardware when the user applies a test signal through a switch provided in the operation unit and the display unit 10 to check the result of the micro-control. Output to processor 8. Then, the microprocessor 8 determines the abnormality and displays the corresponding signal on the screen through the operation unit and the display unit 10. In addition, when the user inputs various variables through the operation unit and the display unit 10, the microprocessor 8 receives them and stores them in the RAM 16 and the automatic storage RAM 17 through the internal bus lines. The RAM 16 stores various variables in the data area, and the automatic storage RAM 17 stores data necessary for restarting the motor, and this data is automatically stored in the nonvolatile area even at power down. The ROM 15 also stores a program. On the other hand, the local input / output unit 11 inputs and outputs signals to and from the microprocessor 8 for controlling various switches required for starting the motor. In addition, the abnormal power detector 12 monitors the input power and outputs an abnormal signal to the microprocessor 8 when the power drops below a certain level, where the microprocessor 8 enables the automatic storage RAM 17. (enable) to save the current running state. At this time, the value stored in the automatic storage RAM 17 is used at the time of automatic restart after a power failure. Here, the network 13 connected with the microprocessor 8 makes it possible to connect a plurality of relays of the apparatus of FIG. 1 as shown in FIG. The serial communication port 14 and the sequence interface 18 connected to the microprocessor 8 are connected to an external PC (or PLC), and the serial communication port 14 allows the user to download information related to the motor to the PC. Used to receive or set a variable. The sequence interface unit 18 allows a user to input a sequence using a PC and is appropriately operated on the result of the calculation in the microprocessor 8. That is, when the user sets the sequence input mode through the control unit 10 and the microprocessor 8 inputs the sequence using the PC through the serial communication port 14, one of the first to fourth relays is used. Send the current relay status to the PC. Therefore, the user sets the motor starting condition of the relay to be set in consideration of the states of the plurality of relays, or inputs a sequence to set the interlocking conditions so that the plurality of relays (first to fourth relays) can be operated integrally. Can be set. According to such a condition, the motor connected to the relay is started according to the load state of the motor transmitted from the plurality of relays upon automatic restart. In addition, even when not used in conjunction, the sequence can be input to the current relay, and when the input sequence is not suitable for the sequence connected to the current relay, an error is output through the operation unit and the display unit 10, and the user can output the sequence. To prevent errors. If the user does not input the sequence, the relay restarts the motor after the automatic restart time input by the user through the control unit 10 has elapsed.

As described above, the present invention allows the user to set the sequence with a PC or a PLC, which is easy to maintain, and can be used by connecting a plurality of relays. to provide.

Claims (2)

A digital protective relay comprising an A / D converter for receiving a voltage detected at the time of motor operation and a presence / absence signal, an overcurrent and a ground fault signal, and converting the signal into a digital signal. An operation unit including a key for setting a sequence input mode; A sequence interface unit connected to a PC to enable a sequence interface, and configured to input a sequence using a PC when a sequence input mode is set using the operation unit; A microprocessor configured to receive and calculate the digital signal of the A / D converter, and to determine operation of the load when restarting after a power failure by a sequence input to the sequence interface unit; A digital protective relay that can be operated according to the status of each relay by connecting a plurality of relays with a network installed. The digital protective relay as claimed in claim 1, wherein the sequence interface unit is capable of inputting a sequence to a PLC.