KR19980083497A - DC Cable Ground Detector - Google Patents

Abstract

The present invention relates to a ground fault detector for detecting a ground fault and a position of a ground fault when a ground fault occurs in a DC line, a detector for detecting a ground fault of a DC feeder, and a low pass filter (LPF1) for removing noise in a detected state. The ground fault detection level is detected by the signal converter which detects the phase of the filtered state and converts the effective value, and the ground current that has passed the signal converter by A / D converter and software in the computer. Only when a ground fault occurs, the circuit is configured so that the AC voltage flows through the ground resistance and the line, and the voltage used for this circuit is obtained by using the DC-DC converter to obtain the DC voltage. By using an AC voltage of 11 ㎐, the effect of AC 60 ㎐ can be minimized, and the ripple frequency that causes noise in DC can be reduced. There are effective.

Description

DC Cable Ground Detector

The present invention relates to a ground fault detector for detecting the position of the ground fault and ground fault when the DC line used in power plants, etc. occurs.

The ground fault detector used in the prior art generates an alarm by comparing with the set value when a ground fault occurs. The ground fault detector includes a DC drop method and an AC voltage drop method. Since 20 [Hz] is used, AC 60 [㎐] has a big influence and a ripple frequency that causes noise in DC is generated.

And most of the detector was a laminated type of clip-type silicon steel sheet.

1 is a configuration diagram of a ground fault detector using a conventional DC voltage drop method. In order to detect a ground fault of a DC feeder, two circuits are provided between a positive side and a negative side of a feeder. The resistors R1 and R3 are connected, and a common connection point of the resistor R1 and the resistor R3 is connected to the variable resistor P1, and a resistor R2 connected to the variable resistor P1 is connected to the ground GND. A P-side ground fault detection DC amplifier connected to the movable terminal of the variable resistor P1 in common to the bases of the transistors Q1 and Q2 and connected to the emitter of the transistor Q1 to detect ground faults. (1), the N-side DC detection DC amplifier (2) connected to the collector of the transistor Q2 and detecting the ground fault and the ground fault signal detected by the ground fault detection DC amplifiers (1, 2) are converted into DC. It consists of a DC-DC converter 3.

According to the configuration, when a ground fault occurs in the positive feeder, current flows from the positive feeder to ground (GND) and the resistor (R2) to the P1 feeder.

Therefore, the base voltage of transistor Q1 becomes a negative potential, and the base voltage of transistor Q2 also becomes negative.

Accordingly, the transistor Q1 operates and the P-side ground detection DC amplifier 1 drives to drive the relay.

According to the above, since the voltage across the variable resistor P1 and the resistor R2 is the voltage between the transistor base and the emitter, the sensitivity is determined because the operating voltage of the transistor can be adjusted by adjusting the variable resistor P1.

On the other hand, if the ground of the negative feeder is different from the ground of the positive feeder, the direction of the current is reversed and the transistor Q2 is operated so that the N-side ground fault detection DC amplifier 2 The relay operates to generate an alarm.

2 is a configuration diagram of a ground fault detector using a conventional AC voltage drop method, and includes resistors R4 and R5, resistors R4 and resistors connected between the positive and negative feeders of a series (DC) feeder. (R5) Resistor R6 transmits a signal of a comparison resistor P1 'connected to the connection point, a square wave generator 4 for generating a square wave of a predetermined frequency and transmitting it to the resistor, and a connection point between the resistors R4 and R5. The linear amplifier 6 for receiving and amplifying the signal through the capacitor, and the signal at the connection point of the resistor R4 and the resistor R5 is inputted through the capacitor C2 to ground the input signal of the log amplifier 7 and the log amplifier. A signal between the first transistor T1 for bypassing the signal, the second transistor T2 for controlling the transfer of the output of the log amplifier 7 to the next stage, the square wave generator 4 and the comparison resistor The sequential controller 5 for controlling the transistors T1 and T2 for ground fault detection, and the signal of the second transistor T2 A capacitor C3 for charging the charging characteristics of the lock resistor, an amplifier 8 for amplifying the charged signal, a first switch 9 for exchanging the signal of the amplified signal and the linear amplifier 6, and a switched A counter 10 for indicating the state of the signal, a second switch 11 for switching and grounding the state of the counted signal and the classifying state of the classifier 12, and generating a gap in response to an amplifier signal and an alarm set point; A gap device 13, a delay device 14 for delaying a signal of the gap device, and an alarm 15 for generating an alarm in accordance with the delayed signal.

In FIG. 2, the voltage Ug of the square wave generator generally generates a square wave of ± 10V.

The current flowing through the comparison resistor is shown in the following equation (1).

And the equivalent ground resistance value is expressed as the following equation (2).

In Equations (1) and (2), Ur represents the voltage change between the circuit and ground, and P represents the comparative resistance of about 1 ㏁.

If the ground resistance is 100K, the voltage of the voltage change (Ur) between the circuit and ground becomes about 1.1V by the above equation.

However, since the AC voltage drop method has a large comparative resistance (P), the charging time is required until a stable Ur voltage is obtained by the capacitance of the line, so the cycle of the square wave generator is about 1.5 minutes.

Therefore, if the capacitance is small, the period of the square wave generator may be reduced.

Since the AC voltage drop method as described above uses an applied AC voltage of 20 [kW], the AC voltage drop has a great effect on AC 60 [kW], which is normally input, and causes a ripple frequency that causes noise.

In order to solve the above problems, the present invention, when a ground fault occurs in the DC line, the alarm is detected, and the ground resistance and the position of the ground fault is detected, and the applied alternating current voltage to AC 60 [60] using 11 [㎐] The goal is to reduce the effect on the signal as much as possible and to reduce the ripple frequency that causes noise in direct current.

1 is a block diagram of a ground fault detector using a conventional DC voltage drop method.

2 is a configuration diagram of a ground fault detector using a conventional AC voltage drop method.

3 is a block diagram of a ground fault detector to which the present invention is applied.

4 is a characteristic diagram of a 11 [kV] signal generating circuit according to the present invention;

5 is an internal block diagram of a signal converter according to the present invention;

Explanation of symbols on the main parts of the drawing

17: first central processing unit 18: second central processing unit

19: 11 ㎐ signal generator 19a: photocoupler

19b: rectifier 20: DC wire

21: self-diagnosis machine 22: DC-DC converter

23 sensor 23a, 23b, 23c current transformer

24, 36: low pass filter 25: signal conversion unit

26: alarm 27: monitor

28: printer 29: mouse & keyboard

30, 31a: null modem 31b: other computer

32: power 33: loader

34: surge suppression resistor (RG) 35: AC amplifier

37 Gain Amplifier 38 Effective Value Converter

39: square wave waveform shaper 40: polarity and phase measurement circuit

41: latch

In order to achieve the above object, the ground fault detector according to the present invention detects the ground fault detection level when a ground fault occurs in the DC line 20 used in a power plant or the like, and the control signal and 11 [㎐] square wave signal of each component. A first central processing unit (17) for outputting a control signal for generation, and a self-diagnostic apparatus (21) for checking the abnormality of the sensor under operation control of the first central processing unit and notifying the result to the first central processing unit (21). ), A DC-DC converter 22 for converting a voltage supplied from the DC line 20 into an element operating voltage, a control signal of the first CPU 17 and an operating voltage of the DC-DC converter. Is attached to the 11 [㎐] signal generator 19 for generating a 11 [㎐] square wave signal and the DC line 20, and the generated square wave signal is applied to the DC line through parallel resistance. Ground fault phase of the DC line A sensor 23 for detecting a signal, a low pass filter 24 for removing noise other than 11 [kHz] components of the detected signal, a signal converter 25 for converting a phase and an effective value of the removed signal, A second central processing unit 18 which receives the converted signal and compares it with data collected before the system installation, determines whether a ground fault has occurred, and transmits the determination result to the first central processing unit 17; The alarm 26 receives the confirmation result of (21) and the determination result from the said 2nd central processing unit 18, and receives the control according to the determination result of the 2nd central processing unit 18, and generates an alarm, and a ground fault is received. The monitor 27 and printer 28 outputting the name of the generated DC line 20 and the degree of ground fault, and the control according to the determination result of the second central processing unit 18 of the DC line 20 Use your mouse or keyboard (29) to know your name and ground level When characterized by consisting of a null modem (30, 31b) for transmitting ground data to the other computer (31b).

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

3 is a block diagram of a ground fault detector to which the present invention is applied.

The ground fault detector includes a DC line 20, a sensor 23 for detecting a ground fault in the DC line, and a predetermined number of low pass filters for removing noise other than 11 [㎐] of the detected signals. (Low Pass Filter, LPF) 24, a Signal Converter Unit (SCU) 25 for detecting the phase of the removed signal and converting the effective value, and data collected before the system installation by receiving the converted signal. The result of the determination of the second central processing unit 18 for determining the degree of ground fault, the self-diagnostic device 21 for diagnosing whether the sensor 23 operates normally, and the second central processing unit 18 as compared with And a first central processing unit (17) for controlling the ground state data output, controlling the self-diagnosis unit (21), and outputting each control signal for generating the 11 [㎐] square wave signal; 20 to convert the power supply (125V) 32 supplied to a predetermined direct current operating voltage Control for generating 11 [kV] signals from the DC-DC converter 22 on the power plant side to be applied to the 11 [kV] signal generator 19 and the first central processing unit 17. It consists of an 11 [kW] signal generator 19 which receives the signal and the converted DC voltage, and generates an 11 [kW] square wave signal through the parallel resistance to the DC cable.

An alarm 26 for generating an alarm under the control of the first central processing unit 17 and a monitor for allowing the user to check the ground fault occurrence state data under the control of the first central processing unit 17 ( 27) and the printer 28 and other computers so that other users can recognize the mouse & keyboard 29 and the output of the ground fault detection status data to the first central processing unit 17 at another location. A modem 30 for transmitting to 31b) may be installed. In this case, the first CPU 17, the alarm 26, the monitor 27, the mouse and keyboard 29, and the modem 31a may be configured as one personal computer.

4 is an internal configuration diagram of the 11 kHz signal generation unit.

The configuration includes a photocoupler 19a for switching in accordance with a control signal generated from the first CPU 17 and outputting an operation signal converted from the DC-DC converter 22, and an operation output from the photocoupler. It is comprised by the bridge rectifier 19b which rectifies a signal.

A square wave signal of 11 [kW] is supplied from the 11 [kW] amplification processing device 17 to the resistance of the power plant side through the photocoupler 19a, and the feeder contains 11 [kW] of signal components. The power required to supply the signal of is used by using a DC-DC converter 22 in a DC feeder 20 on the power plant side.

Once the 11 [㎐] square wave component is supplied to the feeder and there is a surge resistance as shown in Fig. 4, the signal component of 11 [㎐] flows through the surge suppression resistor 34, so that the current transformers 23a, 23b, 23c for detecting ), As much as the signal of the ground component is generated, it is possible to find the feeder is a ground fault.

5 is an internal block diagram of a signal converter according to the present invention.

The configuration includes an AC amplifier 35 for amplifying the signal input from the sensor, a low pass filter (LPF) 36 for filtering only 11 [Hz] ground fault components of the signal passing through the AC amplifier, and a gain of the filtered signal. A gain amplifier 37 and an effective value converter 38 for amplifying and converting the ground current into an effective value, a square wave waveform shaper 39 for shaping the square wave of the ground current passing through the gain amplifier 37, and the polarity of the squared square wave and It consists of a polarity and phase measurement circuit 40 for measuring phase, and a latch 41 for temporarily storing the output of the measured polarity and phase for transmission to another computer.

Referring to the operation according to the configuration, first, the input from the sensor is applied to the Chebyshev third-stage low-pass filter 36 through the AC amplifier 35 to filter only 11 [락] ground fault components, and the filtered signal is gained. Through the amplifier 37, the effective value converter 38 converts the ground fault current into the effective direct current.

The ground current value converted to direct current is applied to the analog / digital (A / D) multiplexer (MUX).

Then, the 11 [kPa] ground fault current through the gain amplifier 37 is applied to the polarity and phase measurement circuit 40 through the square wave waveform shaper 39, and the output thereof is transmitted to another computer through the latch 41. COMPUTER).

Looking at the overall operation of the present invention according to the above configuration.

First, when the sensor 23 is abnormally operated by controlling the self-diagnostic device 21, the first central processing unit 17 which constantly supplies 11 [square] square wave signals so as not to be influenced by temperature and other environments. This is notified through the alarm 26, the monitor 27, and the printer 28. On the other hand, when the sensor 23 operates normally, the first CPU 17 outputs a control signal for generating an 11 kHz square wave signal.

The 11 kHz signal generator 19 receiving this control signal supplies the 11 ㎐ square wave signal to the DC wire path 20. At this time, the 11 kW signal generator 19 receives the device operating voltage from the DC-DC converter 22 and operates the photocoupler 19a according to the control signal received from the first CPU 17 to bridge the rectifier 19b. 11) square wave signal is supplied to the DC line 20 through the parallel resistor.

When a ground fault occurs in the DC line 20, the 11 Hz component detected by the sensor 23 using the current transformer is transmitted to the low pass filter 24. The low pass filter 24 receiving the transmitted signal removes noise of the signal and sends the removed signal to the signal converter 25.

When the signal conversion unit 25 receives the converted data for use in the central processing unit and sends the converted data to the second central processing unit 18, the previously converted data and the converted data are compared by the second central processing unit. Determine if a ground fault has occurred.

If a ground fault occurs after the determination, the first central processing unit 17 generates an alarm so that the user can sense it acoustically through the alarm 26, and the first central processing unit 17 transmits the transmitted data. Is compared with the reference data and outputs the name of the feeder on which the ground fault is generated and the degree of the ground fault through the monitor 27 and the printer 28.

Then, the user operates the mouse and the keyboard 29 to set the initial resistance value of the self-diagnostic device 21, and informs the first central processing unit 17 to another computer through the null modems 30 and 31a, or The ground state data is output through the monitor 27 and the printer 28. As a result, the situation of the site inside the power plant can be checked in other offices.

As described above, when the ground fault of the present invention is a ground fault in a DC line used in a power plant or the like, the ground fault detector may detect the degree of ground fault and the position of the ground fault as well as generating an alarm compared to the set value. By using 11 [사용한] of applied AC voltage used in AC voltage drop method, the effect of AC 60 [㎐] can be reduced as much as possible, and the ripple frequency that causes noise in DC can be reduced.

Claims (4)

In the ground fault detector which detects the ground fault detection level when the DC cable used in the power plant etc. has a ground fault, A sensor for detecting a ground fault in the DC line; A predetermined number of low-pass filters for removing noise other than 11 [Hz] of the detected signals; A signal converter for detecting a phase of the removed signal and converting an effective value; A second central processing unit that receives the converted signal and compares the data collected before installing the system to determine the degree of ground fault; A self-diagnostic device for diagnosing whether the sensor operates normally; A first central processing unit which receives the determination result of the second central processing unit to control the ground state data output, to control the self-diagnosis unit, and to output a control signal for generating an 11 [㎐] square wave signal; A direct current-to-direct current (DC-DC) converter on the power plant side, which is applied to an 11 [kW] signal generator for converting the power supplied to the direct current line into a predetermined direct current operating voltage; And A control signal for generating the 11 [kW] signal from the first central processing unit and an 11 [kW] signal generator for generating the 11 [kW] square wave signal through the parallel resistance in the DC line by receiving the converted DC voltage. DC line ground fault detector. The method of claim 1, wherein the signal generator A photocoupler for switching according to the square wave signal generated from the first central processing unit and outputting an operation signal converted from the DC-DC converter; A switch circuit for switching in accordance with an operation signal output from the photocoupler; And a rectifier for rectifying the operation signal output from the photocoupler and transmitting the rectified signal to the parallel resistor. The method of claim 1, wherein the signal conversion unit An amplifier for amplifying the signal input from the sensor; A low pass filter (LPF) for filtering only 11 [Hz] ground fault components of the signal passed through the amplifier; A gain amplifier and an effective value converter for amplifying the gain of the filtered signal and converting the gain to an effective ground fault current; A square wave waveform shaper for shaping a square wave of a ground fault current passing through the gain amplifier; A polarity and phase measurement circuit for measuring the polarity and phase of the shaped square wave; A direct current line ground fault detector comprising: a latch for temporarily storing the output of the measured polarity and phase to another computer. 2. The system of claim 1, wherein said first central processing unit DC line ground fault detector, which is equipped with alarm, monitor, printer, mouse, keyboard, and modem so that users can know the situation in the office.