KR0146091B1 - Digital selection ground relay - Google Patents

Abstract

The present invention relates to a fault detection method using high-speed pager operation of a digital selective ground relay. In the conventional case of a digital selective ground relay, multiplication and addition are performed if a non-recursive DFT is used to calculate a phaser of image voltage and image current. Due to the large amount of calculations, the operation time is long, resulting in delays in relay operation determination, and in the case of using a general microprocessor without using a signal processing device (DSP), the operation may sometimes encounter limitations in operation. There is this. Therefore, in the present invention, in the method of processing the input signal, the signal processing method used for the pager calculation is performed by using the recursive DFT to calculate the pager so that the calculation can be performed quickly with fewer calculations, thereby enabling high speed failure determination. .

Description

Fault Detection Method Using Phaser High Speed Operation of Digital Selective Ground Relay

1 is an external wiring diagram of a conventional analog selective ground relay.

2 is an operational phase characteristic diagram of an analog selective ground relay in FIG.

3 is an external wiring diagram of a conventional digital selective ground relay.

4 is an internal configuration diagram of a conventional digital selective ground relay.

5 is a flowchart of fault determination through high-speed operation of a pager of the digital selective ground fault relay of the present invention.

6 is a phase operation characteristic diagram of the digital selective ground relay of the present invention.

* Explanation of symbols for main parts of the drawings

10: video current detector 20: video voltage detector

30: operation unit 40: input signal conversion unit

50: filter unit 60: amplification unit

70: analog / digital converter 80: microprocessor

90: drive unit 100: display unit

110: correction unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a selective ground relay that selectively blocks an accident line in case of a ground fault in a distribution line, and in particular, a phaser high speed of a digital selective ground relay that enables faster signal processing in calculating a phase voltage of an input voltage and image current. The present invention relates to a fault detection method using arithmetic operations.

As shown in FIG. 1, the external connection diagram of the conventional analog selective ground relay includes an image current detection unit 10 which detects a vector difference of three-phase current in an AC line (R, S, T) and detects an image current of a line. The image voltage detector 20 detects the image voltage in the AC line, the image current detected through the image current detector 10 and the image voltage detected through the image voltage detector 20 as input signals. It consists of a trip part 30 which drives an induction disk inside the relay with a torque represented by the phase difference between the voltage and the image current and the product thereof, and trips the operation part of the relay.

In addition, the digital selective ground relay includes an input signal converter 40 for detecting an image current and an image voltage using ZCT and GPT and outputting the detected signal, as shown in FIGS. 3 and 4; A filter unit 50 for filtering the signal transmitted through the input signal conversion unit 40, an amplification unit 60 for amplifying the signal filtered by the filter unit 50 to a predetermined level, and the amplification The relay is driven through the driver 90 by the analog / digital converter 70 for converting the signal amplified by the unit 60 into digital data and the data input through the analog / digital converter 70. The microprocessor 80 and the analog / digital conversion unit 70 to correct the operation correction values for the image current and the image voltage input to the microprocessor 80 through the data bus Giving correction unit 110, It consists of a display unit 100 that displays the measurement value or the correction condition for the electric charge to the anti-operating state.

Referring to the prior art configured in this way in detail as follows.

First, in the case of the analog type selective ground relay, the image current Io flowing through the three-phase (R, S, T) power distribution line of FIG. 1 is input through the image current detection unit 10 that detects using ZCT, and the image voltage ( Derivation of the inside of the relay by the torque represented by the phase difference between the image current Io and the image voltage Vo and the product between the image current Io and the image voltage Vo is received through the image voltage detection unit 20 that detects Vo using GPT. As shown in Fig. 2, when the image current Io is 37 ° more than the image voltage Vo, the maximum torque is generated in the induction plate to show the phase characteristics that work best. The operating range is within ± 90 ° of the maximum sensitivity phase.

In the case of the digital selective ground relay, the image current Io detected using the ZCT and the image voltage Vo detected using the GPT are different from the internal current transformer CT shown in FIG. When the signal level is inputted to the internal transformer PT and the signal level is changed and transmitted to the filter unit 50, the filter unit 50 uses a low pass filter to remove higher-order harmonic components included in the input signal. The harmonic components are removed and amplified to a predetermined level through the amplifier 60 for improving the resolution of the analog / digital converter 70 for the small signal and supplied to the analog / digital converter 70.

Then, the analog / digital conversion unit 70 converts the digital value into a digital value and outputs it to the microprocessor 80 through a data bus, and performs digital signal processing using digital signal processing in the microprocessor 80. The treatment method is as follows.

When the number of samples per cycle is N, the digital value collected through the filter unit 50, the amplifier 60, and the analog / digital converter 70 by receiving the image voltage and the image current is Zk (k = 0 , 1,2, …… N-1), the real part and the imaginary part of the electric quantity collected at the kth sampling point are non-recursive discrete Fourier transform (hereinafter referred to as non-recursive DFT). Using can be found as follows. Here, the DFT is a Discrete Fourier Transform.

Using the equations (1) and (2), the phaser for the fundamental wave is calculated for the image voltage Vo and the image current Io.

Where Vor: image voltage DML real component Voi: imaginary component of image voltage

Ior: Real component of video current Ioi: Imaginary component of video FB

Find the size of the image voltage phaser with.

Find the size of the image voltage phaser with.

For motion phase discrimination

T = | Vo || Io | COS (θ-θo)

However, θ = θi-θv, θ: Maximum operating sensitivity phase

If T 0 is calculated, it is determined as an operation region, and θ _O is a value corrected by the correction unit 110 of FIG. 4.

In this way, when calculating the phaser of the image voltage and the image current, COS (2πr / N) and SIN (2πr / N) are used to update the real and imaginary component values of the electric quantity at one sample point as shown in Equations (1) and (2). 2) is taken from the look-up table on the ROM inside the microprocessor 80, and 2 (N + 1) multiplication operations and 2 N addition operations are required.

When the driver 90 is operated when it is determined to be a failure through the above operation, the driver 90 drives the circuit breaker of the switchboard.

However, in the conventional technology as described above, in the case of the analog selective ground fault relay, since the phase delay is set by hardware, the maximum sensitivity phase cannot be changed when the maximum sensitivity phase angle is changed according to the configuration of each distribution line. Since it operates as a torque of the voltage and the image current, if one value is at least the other value is large, the operation is made, and thus the setting of the operating image voltage and the operating image current is difficult.

In addition, even in the case of digital selective ground relay, which compensates for the shortcomings of the analog type, if the non-recursive DFT is used to calculate the phase of the image voltage and the image current, the operation time is long because the calculation and addition operation is long, and thus the relay operation decision In addition to reducing delay, when a general microprocessor is used without using a signal processing device (DSP), there may be a problem in that an operation may encounter limitations.

Accordingly, an object of the present invention is to improve the signal processing method used for the pager calculation in the method of processing the input signal, so that it can be calculated quickly with fewer operations, so that a high speed fault determination is possible. It is to provide a fault detection method using high speed operation.

In order to achieve the above object, the present invention provides a first step of collecting digital values for an analog / digital converted image voltage and an image current, and an image voltage obtained by a recursive DFT with the digital values collected in the first step. A second step of calculating a real component and an imaginary component of each phaser of an image current; a third step of calculating a pager size of a fundamental wave for the image voltage and the image current obtained in the second step; and the second step In step 4, if the size of the phaser obtained is smaller than the predetermined operating value, and if the size of the phaser is large, the fourth step of calculating the phase difference between the image voltage phaser and the image current phaser, and the operation phase using the digital value and phase difference obtained in the above step. The fifth step of determining the operation and if the operation phase discrimination value obtained in the fifth step is greater than 0, it is determined that the fault is driven to drive the drive unit, and if it is small That perform comprises a sixth step.

The present invention for achieving each step as described above is the same as the configuration shown in FIG. 3 and FIG. 4, and FIG. 5 for the digital signal processing for the input signal performed in the microprocessor by the configuration. Based on the following.

The image voltage Vo detected by the input signal converter 40 using the GPT and the image current Io detected using the ZCT are included in these signals after the signal level is changed by the internal CT and the internal PT. After passing through the filter unit 50 consisting of a low-band pass filter to remove higher-order harmonic components, the amplification unit 60 is amplified to a predetermined level through an amplification unit 60 for improving the analog / digital conversion resolution for small signals. The converter 70 is supplied.

Then, by using the signal converted into a digital value in the analog / digital conversion unit 70 in the microprocessor (80) inside the signal through the following signal processing method different from the non-recursive DFT which is a conventional signal processing method Calculate the pager.

At this time, when the number of samples per cycle is N, the digital value collected through the filter unit 50, the amplifier unit 60, and the analog / digital conversion unit 70 by receiving the image voltage and the image current is assumed to be Zk. The real and imaginary components of the amount of electricity collected at the first sampling point can be obtained as follows using recursive DFT.

If the phaser of the input electric quantity at the Kth sampling point is Z _k ,

Where the real component Zrk and the imaginary component Zik of the pager

Z _rk-1, Z _ik-1 : Real component and imaginary component of sample phaser one before kth

Z _rk-N, Z _ik-N : Real and imaginary components of sample phaser one cycle before kth

Using the equations (3) and (4), the phaser for the fundamental wave is calculated for the image voltage Vo and the image current Io.

Where Vor: real component of image voltage, Ioi: imaginary component of image voltage

Ior: Real component of image current, Voi: Imaginary component of image current

In the case of calculating the image voltage and the phaser as described above, COS (2πK / N) and SIN (2πK /) are used to update the real and imaginary components of the electric quantity at one sampling point as shown in equations (3) and (4). N) When the part is taken from the look-up table on the ROM, it is possible to perform 2x1 multiplication operations and 2x2 addition operations.

The conventional non-recursive DFT calculates the pager using two (N + 1) summation operations (N is the number of samples per cycle) and two or N addition operations to update the real and imaginary components of the electric quantity at one sampling point. Compared to doing this, every step is used to calculate the pager, which enables faster computation.

On the other hand, the electrical phaser is updated at every sampling point, which enables high-speed operation in the event of a failure.

Using the phaser for the fundamental wave of the image voltage (Vo) and the image current (Io) calculated through equations (3) and (4)

The magnitude of the image current

The magnitude of the video voltage Obtain as

θ is the difference between the phase angle of the image current and the phase angle of the image voltage

θ = θ _I -θ _V

In the operating phase characteristic of FIG. 6, when θc-90 ° θ θc + 90 °, it is in the operating region. θc is the maximum sensitivity phase angle set according to the characteristics of the distribution system for installing the relay in the correction unit 110 of FIG.

-90 ° θ -θc 90 °

If COS (θ-θc) is 0, it is an operating condition.

Therefore, the operating condition under which the relay operates is the magnitude of the image voltage obtained from Equation (7). The magnitude of the video current obtained by the correction unit 110 of FIG. Is greater than or equal to the operating image current corrected by the correcting unit 110 of FIG. 4 and is operated when the phase discrimination equation T = | Vo | | Io | COS (θ -θc) 0.

Using the same method as described above, it is possible to calculate the pager with very few calculations, so that the higher speed calculation is possible, thereby making it possible to determine the high speed operation when a failure occurs.

Claims (1)

The first step of collecting the digital values for the analog / digital-converted image voltage and the image current, and the real components of each of the phaser of the image voltage and the image current by the recursive DFT with the digital values collected in the first stage. And a second step of calculating an imaginary component, a third step of calculating a pager size of the fundamental wave with respect to the image voltage and the image current obtained in the second step, and a pager obtained in the third step, than the preset operating value. Performing a first step if small, and calculating a phase difference between the image voltage pager and the image current phaser; and a fifth step of determining an operation phase using the digital value and the phase difference obtained in the step; If the operation phase discrimination value obtained in the step is greater than zero, it is determined that it is a fault and the driving unit is driven. Fault detection method using pager high speed operation of digital selective ground fault relay.