JPH0538042A - Digital distance relay - Google Patents

Abstract

PURPOSE:To effectively operate a relay at the time of a forward accident by controlling an output of an element or a calculated value to be used for decision so to forcibly operate a reactance element and a blinder element even if an input current exceeds a full-scale. CONSTITUTION:A momentary value is extracted by using current data stored in a RAM. Full scale-over detecting means S102 decides whether the momentary value is larger or smaller than a full scale decision value, and reactance element forcible means S103 forcibly operates a reactance element if the value is larger. Then, a blinder element forcible means S104 forcibly operates a blinder element. Then, direction element deciding means S105 forcibly operates a direction element. Thereafter, an AND operation of the operation outputs of the elements is decided by the means S103-S105, and decision result of a relay operation is output by relay output means S107. Thus, a relay at the time of forward accident can be effectively operated.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art An example of a digital range relay using a microcomputer used for protection of a range relay of a power system will be described with reference to FIG. In FIG. 3, the voltage and current of the power system are taken in through an input converter 31 that centralizes and stores the PCT, and is filtered by a filter (FL) 32 that takes out only the commercial frequency components of the voltage and current. Done. Since each filter output is an analog signal, it is input to an analog / digital converter (A / D) 35 through a sample hold circuit (S / H) 33 and a multiplexer (MPX) 34 to be converted into a digital signal. . The voltage and current digital signals converted here are
It is temporarily stored in the data memory (RAM) 37 via the direct memory access (DMA) 36. The CPU 38 performs the digital arithmetic processing of the distance relay on the current and voltage data stored in the RAM 37 according to the processing procedure stored in the read only memory (ROM) 39.

FIG. 4 shows the phase characteristic of the distance relay, and FIG. 5 shows a conventional processing flowchart. In FIG.
The phase characteristic of the distance relay is indicated by an AND characteristic of a blinder element having a function of identifying a reactance element having a distance measuring function and a tidal current (load current), and a direction element having a front / rear determination function. In FIG. 5, step S108 is a conventionally known L / R calculation process (P-49 of “Digital Cooperative Research” Vol. 41 No. 4, “Digital Relay”, example of direct impedance calculation method in Table 4-2-1), for example, in derivative approximation method, the current instantaneous value i _m, i _m-1, the voltage instantaneous value v _m, v _m-1 (where denotes the sampling _{time), I m = i m +} i m-1, J _m = (i _m −i _m−1 ) · k
(K: constant), V _m = v _m + v _m-1 Like.

Step S109 is a reactance element determination process, which is performed by the following equation (2), for example. L ≦ L _s (set value) (2) Next, step S110 is blinder element determination processing, for example, At. Step S111 is a directional element determination process, where, for example, I: current, V _M : voltage with memory (for example, voltage of the previous two cycles), I · V _M cos (θ−ψ)> 0 ... ). Where θ: lead angle of V _M with respect to I, ψ:
Sensitivity angle (eg 60 °), then step S106 is an AND decision
AND judgment is performed to establish (2), (3), and (4). Step
S107 outputs the relay operation determination result when the AND output in the above step is present in the relay output process.

[0005]

Regarding the characteristics of the current full scale over range of the distance relay, see, for example, P-51 of "Digital Cooperative Research", Vol. 41, No. 4, "Digital Relay".
As described in FIG. 4-3-4 (see FIG. 6 of the present specification).
(Refer to (a)), and shows an underreach tendency due to saturation of the current input. If this underreach exceeds the current / impedance characteristics of the system, there is no problem. Here, the system current / impedance is obtained as follows. Figure 6
In (b), E: power supply voltage, Z _s : back impedance, Z _l : settling impedance, and I: current,
It has the relation of equation (5). Example) When Z _s = 0.635 Ω, Z _l = 0.25 Ω, and E = 63.5 V, I = 100 A at x = 0, I = 83.6 A at x = 0.5, I = 71.8 A at x = 1. is there.

However, as shown in FIG. 6 (c), when the underreach characteristic of the distance relay is lower than the current / impedance characteristic of the system, there is a possibility of malfunction due to an accident in the protection section. When the current is full scale over
The output of the analog / digital converter (A / D) 35 in FIG. 7 is in a form in which the upper limit is applied, and has a waveform as shown in FIG. Here, the current instantaneous value i _m, i _m-1 is i _m * i
Therefore, _m−1 (note that * means almost equal. The same applies hereinafter), and thus the combined current amount J _{m in the} equation (1) can be J _m * 0. As a result, the denominator of L in the equation (1) becomes close to zero, and the voltage amount V _{m in the} equation (1) satisfying the equation (2) becomes a small value. That is, regarding the input current I and the current V to the input converter 31 of FIG. 3, when the current I is constant, the voltage V is small, and therefore the impedance seen by the relay is small,
As shown in FIG. 6 (c), a steep underreach characteristic is exhibited.

As described above, when the underreach characteristic becomes remarkable with respect to the current full scale over and the current / impedance characteristic of the system is lowered, there is a possibility of malfunction due to an accident in the protection section. There was a drawback.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a digital distance relay that can reliably operate even when a current full scale is exceeded.

[0008]

In order to achieve the above object, the digital distance relay according to the present invention compares the input current amplitude value with the input current amplitude value and the current full scale value to judge the magnitude. Full-scale over detection means, and a forcible operation means of reactance element and direction element,
The L / R value calculating means, the reactance element determining means, the direction element determining means, the AND determining means, and the relay output means are included.

First, the amplitude value of the input current is calculated, it is determined whether the amplitude value is larger or smaller than the full scale value (predetermined value), and full scale over is detected. When full scale over is detected, the reactance element and direction element are forcibly operated,
Perform relay output. If there is no full-scale over detection, the same processing as in the prior art is performed.

[0009]

Embodiments will be described below with reference to the drawings. Figure 1
4 is a CPU processing flowchart of the digital distance relay of the present invention. Step S101 is means for calculating the amplitude value of the input current. For example, an instantaneous value is extracted using the current data stored in the RAM 37 shown in FIG. Step S102 is a full scale over detection means, and the following (6)
As equation, the instantaneous value of the full scale determination value (for example, a positive 98% of the maximum hexadecimal 7FF) is large or small or determined _{from, i m> k ............ (6} ) When a large become the It proceeds to step S103. Step S103 is a reactance element forcible operation means for forcibly operating the reactance element regardless of the equation (2). Next step
S104 is a blinder element forced operation means,
Force the blinder element to operate regardless of the formula. Then, the process proceeds to step S105. Step S105 is a directional element determination means, and the directional element is forcibly operated regardless of the equation (4). Next, step S106 is an AND determination means, and step S1
The AND logic of the operation output of each element in 03, S104, S105 is judged. Then, the relay output determination result of step S107 is output.

When the current instantaneous value is smaller than the full-scale judgment value in step S102, that is, when full-scale over is not detected, L and R calculations are performed in step S108 as in the case of FIG. 5, and step S109 is executed. Then, the reactance element determination is performed by the equation (2), and the blinder element determination is performed by the equation (3) in step S110. Next, in step S105, the direction element determination is performed by the above equation (4).
Then, the process proceeds to steps S106 and S107. According to this embodiment,
Even if the input current is full scale over and the denominator of L in the equation (1) becomes close to zero, and the equation (2) holds at a small voltage V, and there is a possibility of underreach characteristics, the reactance element , Force the blinder element and direction element to operate. Therefore, when full scale over does not occur in an accident beyond the settling point and full scale over occurs in an accident closer to the settling point, erroneous malfunction can be prevented, which is effective. Other examples will be listed and described below.

In the above embodiment, the instantaneous value (corresponding to the peak value) is used as the means for calculating the magnitude of the input current and the full-scale detecting means, but a known method may be used for calculating the amplitude value. For example, by the area method, It can also be done at. Furthermore, the above-mentioned “Electric cooperative research”
Volume 41 Issue 4 "Digital Relay" P-44 4-1
Table 2 Each method of amplitude value calculation can be used.

In the above embodiment, the method of forcibly operating the reactance element and the blinder element has been described, but a method of controlling the L and R values to zero may be used. Figure 2
Is a processing flowchart in this case. The same block numbers indicate the same functions as in FIG. Step S112
Is an L / R value zero control means, and forcibly sets L = 0 and R = 0 when a full scale over is detected in step S102. Next, in step S109, the equation (2) is determined, and L = 0
Then, Eq. (2) is satisfied, so it is a reactance element operation. In step S110, the equation (3) is judged, and when R = 0,
Since equation (3) holds, the blinder element operation is performed.

In the above embodiment, an example of the reactance blinder element by the L and R calculation method of the differential approximation has been described. However, a conventionally known phase detection method, for example, reactance: X · I ² −IV cos (θ−ψ ′)> 0 (8) where ψ ′: sensitivity angle (eg 90 °) blinder: R · I ² −IV cos (θ−ψ ″)> 0 (9) Here, even in the case of ψ ″: sensitivity angle (eg, 0 °, 180 °), the reactance blinder forced operation process can be applied.

In the above embodiment, the directional element is described as the linear characteristic, but the polygonal line characteristic shown below is used. Here, for example, ψ ₁ = 60 ° and ψ ₂ = 45 ° may be set. Also, the following circular characteristics may be used. _{ZIV M cos (θ-ψ)} -VV M> 0 ...... (11) where, Z: setpoint

Further, although the blind relay element is included in the distance relay, there are not a few cases where there is no problem in application (system with a small load current) even if it is ANDed only with the reactance element and the direction element (straight line or circle). The present invention is also applicable to range relays that do not have blinder elements.

In the above-described embodiment, after the reactance element, the blinder element and the direction element forming the distance relay are forcibly operated at the time of detecting the full scale over, A
The example of performing the ND determination has been described. However, the method is not limited to this example, and the relay output means 107 at the time of detection of full scale over may be directly forcibly operated.

[0017]

As described above, according to the present invention, even if there is a full scale over of the input current, the element output or the calculation value used for the determination is controlled so as to forcibly operate the reactance element (and the blinder element). With this configuration, the digital distance relay can reliably operate in the event of a frontal accident.

[Brief description of drawings]

FIG. 1 is a processing flowchart of a digital distance relay according to the present invention.

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

FIG. 3 is a block diagram of a digital type distance relay using a microcomputer.

FIG. 4 is a phase characteristic diagram of a distance relay.

FIG. 5 is a processing flowchart of a conventional distance relay.

FIG. 6 is an explanatory diagram of problems in the conventional technology.

FIG. 7 is a waveform diagram illustrating the cause of inconvenience when full scale is over.

[Explanation of symbols]

S101 Input current amplitude value calculation means S102 Full scale over detection means S103 Reactance element forced operation means S104 Blinder element forced operation means S105 Directional element forced operation means S108 L, R computing means S109 Reactance element determination means S110 Blinder element determination means S111 Direction element determination means S112 L / R value zero control means

Claims (2)

[Claims] 1. A first means for calculating the amplitude of data acquired from an input current in a digital type distance relay which introduces a voltage and a current of a transmission line and comprises a directional element and an element which responds to a resistance and a reactance value. And a second comparison by comparing the output of the first means and the full scale value of the current.
And the second means, when it is determined that the output of the first means is larger or equal, all the elements constituting the distance relay or the final relay output is forcibly operated.
And a fourth means for judging all the elements constituting the distance relay when the output of the first means is judged to be smaller as a result of the second means. Characteristic digital type distance relay. 2. A first means for calculating the amplitude of data acquired from an input current in a digital type distance relay which introduces a voltage and a current of a transmission line and comprises a directional element and an element which responds to a resistance and a reactance value. And a second comparison by comparing the output of the first means and the full scale value of the current.
And the second means, when it is determined that the output of the first means is larger or equal to the second means, the third means for controlling the resistance and reactance values to zero, and the second means. As a result, when the output of the first means is judged to be smaller, there is provided fourth means for judging all the elements constituting the distance relay, and a digital type distance relay.