JP2766426B2 - Digital type distance relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital distance relay used in a distance relay protection system of a power system.

[0002]

2. Description of the Related Art FIG. 4 shows an example of the configuration of a digital distance relay using a microcomputer which is used to protect a distance relay of a power system. In FIG. 4, the voltage of the power system,
The current is taken in through an input converter 41 that houses the PCT in a concentrated manner, and is filtered by a filter (FIL) 42 that extracts only the commercial frequency components of the voltage and current. Since each filter output is an analog signal, it is input to an analog / digital converter (A / D) 45 via a sample / hold circuit (S / H) 43 and a multiplexer (MPX) 44 to be converted into a digital signal. . The converted digital signal of voltage and current is
The data is temporarily stored in a data memory (RAM) 47 via a direct memory access (DMA) 46. The CPU 48 performs digital operation processing of the distance relay according to the processing procedure stored in the program memory (ROM) 49 based on the voltage and current data stored in the RAM 47.

FIG. 5 is an example of a conventional phase characteristic diagram of a distance relay, and FIG. 6 is an example of a conventional processing flowchart. FIG.
In the above, the phase characteristic of the distance relay is represented by an AND characteristic of a reactance element having a distance measuring function, a blinder element having a function of discriminating a power flow (load current), and a direction element having a forward / backward determining function. The sensitivity angle of the blinder element is -15 degrees on the right side and 180 degrees on the left side. In FIG. 6, in step S101, known L and R arithmetic processing (P-114 of the lecture "Protective Relay Engineering" of the Institute of Electrical Engineers of Japan, an example of the direct impedance calculation method in Table 6.3) is performed. Step S10
Numeral 2 is a reactance element determination process, which is performed, for example, in the following manner: L <Ls...... Note that X = ωL, Xs = ωLs
(X: reactance, ω: angular frequency, L: inductance, Xs: set value).
L: Defined as reactance and explained as L = X. Step S107 is a right-hand blinder element determination process, for example, L> (R−Rs) tan (75 °) (2). Rs is a set value. Step S10
Reference numeral 8 denotes a left-side blinder element determination process, which is performed by, for example, R <-R's... (3). Note that R's is a set value. Step S
Reference numeral 104 denotes direction element determination processing, where I: current, Vm: voltage with memory (for example, the voltage two cycles before), θ: lead angle of Vm with respect to I, and sensitivity angle = 60 °, I · Vm cos (θ (−60 °)> 0 Perform the processing in (4). Next, in step S105, an AND process is performed to obtain equation (1)
, (2), (3), and (4) are determined as AND. In step S106, when the AND output of the above step is present in the relay output processing, a relay operation determination result is output.

[0004]

Consider the effect of load current (current) on the impedance seen by the distance relay (Tokyo Denki University Press, "Protective Relay Technology" P260-
P263, FIG. 3 ・ 15, FIG. 3 ・ 16). Fig. 7 (a)
Is a system diagram showing an accident under load, and FIG. 7 (b) is an impedance seen by the relay under load. In FIG. 7A, P is a power source, A is a relay installation point, J is a branch point,
Consider an accident F on a branch line. Relays may have a sending current and a receiving current. In the RX plane of FIG. 7B, the straight line AJ is on the line impedance angle with A as the origin, and as the fault point F becomes farther from the branch point J, the impedance seen by the relay moves on an arc from J. Then, L transmission or L reception is reached. In considering the protection capability against a fault beyond the branch point (far-end retrofit protection capability), it is necessary to consider the effect of the load current described above. The conventional distance relay (having the phase characteristic shown in FIG. 5) has a problem that the operation capability of the third quadrant is narrow, so that the ability to detect an accident beyond the branch point at the time of receiving power flow is particularly poor. In comparison with the action described later). Further, in view of the burden of digital arithmetic processing, it is desirable that arithmetic processing can be performed by a simpler operation equation instead of calculating the right blinder equation (2) and the left blinder equation (3). Further, from the viewpoint of the number of set values, it is desirable that the number of set values of the blinder can be one rather than two on the left and right.
The present invention has been made in view of the above circumstances, and at the time of sending power flow and receiving power flow, while improving the protection ability against accidents beyond the branch point, reducing the computational load, reducing the integer constant, and simplifying the device. It is an object of the present invention to provide an improved digital distance relay.

[0005]

In order to achieve the above object, a digital distance relay according to the present invention comprises an L / R calculating means, a reactance element judging means, and a right / left blinder element judging apparatus using an absolute value of an R value in an operation equation. Means, direction element determination means, AND determination means and relay output means, and the characteristics of the right and left blinder elements, starting from the same point in the negative direction of the origin of the X axis of the RX diagram, There is provided a left and right blinder element determining means which is symmetric with respect to the X axis and expands the operation range with respect to the sending flow and the receiving flow.

The AND judgment of the conventional L / R calculation, the reactance element and the direction element, and the left and right blinder elements which are symmetrical with respect to the X axis in the R-X diagram and whose operating regions are substantially equal for the sending power flow and the receiving power flow. And perform relay output. Therefore, the operating range is expanded for the sending flow and the receiving flow, and the setting value of the blinder is reduced to one to simplify the operation.

[0006]

An embodiment will be described below with reference to the drawings. FIG.
FIG. 3 is a phase characteristic diagram of the digital distance relay of the present invention.
In FIG. 1, the phase characteristic of the distance relay is represented by an AND characteristic of a reactance element, a left and right blinder element, and a direction element. The sensitivity angle of the left and right blinder elements is -15 on the right.
Degrees, left 195 degrees. FIG. 2 is a processing flowchart of the present invention. In FIG. 2, step S101 is L,
Performs R operation processing. Step S102 is a reactance element determination process, for example, according to the above equation (1). Step S103 is a left / right blinder element determination process, which is performed, for example, by R <L / tan (75 °) + Rs (5). Here, the left side is the absolute value of the R value, and Rs
Is a set value (one). Step S104 is a direction element determination process, for example, according to the above equation (4). Step S10
Reference numeral 5 denotes an AND determination process for performing an AND determination of whether (1), (5), or (4) holds. In step S106, when the AND output of the above step is present in the relay output processing, a relay operation determination result is output.

FIG. 3 is a diagram showing the operation and effect of the present invention. In FIG. 3, the R-X plane shows the phase characteristics of the present invention (solid line) and the conventional example (dashed line) and the impedance seen by the distance relay under load. Here, the blinder is 1
There is enough room for line opening, power fluctuation, etc. The difference between the present invention and the conventional example lies in the characteristics of the left blinder, and the present invention has a wider operating range. The present invention prevents the relay from malfunctioning when the left and right blinders send and receive power.
It ensures that distant accidents with a load can be detected. In particular, while the conventional example was inferior in the ability to detect a distant accident beyond the branch point at the time of the receiving power flow, in the present invention, the operation range of the distant accident detection for the sending / receiving power flow is almost symmetric, and Improves accident detection capability. This effect is remarkable in the trend that the line impedance angle is approaching 90 degrees recently. Further, in the present invention, since the left and right blinders are calculated by the expression (5) (1), the calculation load is reduced and the settling value is reduced by calculating the expressions (2) and (3) of the prior art. One is sufficient. This has the effect of simplifying the device.

Hereinafter, other embodiments will be listed and described. In the above embodiment, the sensitivity angle of the right blinder element was described as 75 degrees, but the present invention is not limited to this, and may be any value of, for example, about 65 to 85 degrees. In the above-described embodiment, the explanation has been made by the expression (5). However, it is obvious that the following may be used. R <L · cot (75 °) −Rs (6) R−Rs <L / tan (75 °) (7) where L: reactance value, R: resistance value, Rs: set value. In the above embodiment, the direction element is described as a linear characteristic, but a circular characteristic shown below may be used. ZIVm cos (θ−60 °) −VVm> 0 (8) Here, Z: set value, I: current, V: voltage, and Vm: voltage with memory. In the above embodiment, the sensitivity angle of the reactance element and the sensitivity angle of the direction element were described as 90 degrees and 60 degrees, respectively. However, the present invention is not limited to this. For example, it may be 75 degrees.

[0009]

As described above, according to the present invention, the characteristics of the left and right blinders are taken into consideration in consideration of the impedance seen by the distance relay when there is a load, so that even in the case of an accident beyond the branch point at the time of the sending / receiving power flow. The reliable operation of the digital distance relay becomes possible. Further, since the left and right blinders can be realized by a simple operation formula, the calculation load is reduced, the integer constant is reduced, and the apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a phase characteristic diagram of a digital distance relay according to the present invention.

FIG. 2 is a processing flowchart of the present invention.

FIG. 3 is an explanatory diagram of the operation and effect of the present invention.

FIG. 4 is a configuration diagram of a digital distance relay using a microcomputer.

FIG. 5 is a phase characteristic diagram of a conventional distance relay.

FIG. 6 is a processing flowchart of a conventional distance relay.

FIG. 7 is an explanatory diagram of a problem of the conventional technique.

[Explanation of symbols]

 S101 L and R calculation processing S102 Reactance element determination processing S103 Left and right blinder element determination processing S104 Direction element determination processing

Claims (1)

(57) [Claims] 1. In a digital distance relay having means for taking in voltage and current of a transmission line and elements responding to a directional element, a resistance and a reactance value, characteristics of right and left blinder elements are represented by R-X diagrams. Of the origin of the X axis
Starting from the same point, symmetrical with the X axis and the tidal current
And a left and right blinder element judging means for enlarging an operation range with respect to a receiving power flow .