JPH04364319A - Protective unit for power system - Google Patents

Abstract

PURPOSE:To detect fault of power system reliably by providing means for detecting a fault and holding the fault detection for a predetermined time. CONSTITUTION:A fault detecting section 12a detects occurrence of fault based on an averaged value of power operated at a power value operating section 11b and a power operated at a power operating section 11a. A fault removal detecting section 12b detects occurrence of fault based on an averaged value of power operated at a power averaged value operating section 11b and a power operated at the power operating section 11a. An under fault detecting section 17 detects under fault based on signals detected at the fault detecting section 12a and the fault removal detecting section 12b. In other words, upon detection of a fault 91D1 a fault occurrence detecting/holding section 13a holds a fault occurrence signal for a predetermined time, and an under fault detection 14 signal is set based on the output from an under fault recording/holding section 13c. According to the invention, under fault can be detected reliably.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power system protection device that stabilizes a power system by using information after the fault has been removed when a power system fault occurs.

0002

[Prior art] When a severe accident occurs in the power system,
Simply removing the accident quickly may not stabilize the power system. Assuming such a case, it is common practice to install a power system protection device for the purpose of stabilizing the power system. One such example is a method of measuring the power of a generator to be protected, detecting the phase angle of the generator from the power of the generator at the time of occurrence of the accident, and predicting a step-out phenomenon. An outline of this device will be explained using FIG. 4. Instrument current transformer 15a and instrument transformer 15
b converts the power grid current and voltage for input to the device 16; The current/voltage acquisition unit 10 converts current and voltage so that they can be used for calculations inside the device 16.

[0003] The power calculation section 11a calculates the power P using the current and voltage taken into the device 16 by the current and voltage reception section 10. In the power average value calculation unit 11b,
The average power value PM over a certain period of time in the past is calculated from the power calculated by the power calculation unit 11a. From P and PM, the accident detection unit 17a detects an accident as shown in equation (3), which will be described later. The phase angle change after an accident is detected in the generator is determined by the phase angle calculating section 71 at the time of the accident detection as shown in equations (1) and (2). A phase angle prediction section 71a predicts the phase angle based on the phase angle determined by the phase angle calculation section 71, and a step-out determination section 72 performs a step-out determination based on the phase angle predicted value. Step-out determination section 7
If step-out is determined in step 2, the generator cutoff section 73 cuts off the generator end to stabilize the power system.

[0004] Here, the phase angle calculation section 71 and the phase angle prediction section 71a will be explained with reference to FIG. Figure 5(a) shows the change in power of the generator when an accident occurs. PM indicates the average value of power. From this, PM
Calculate the angular acceleration ω of the generator by integrating the value of . Here, it is a constant determined from the generator inertia constant. The results are shown in Figure 5(b). ω=k*(PM −P)dt
......(1)
δ=*ωdt
......(2)
Note that the * mark is an integral symbol. The phase angle δ of the generator is determined by integrating ω obtained from equation (1) as shown in equation (2). This result is shown in Figure 5 (
c) Shown below. (2) The future value of δ is predicted by curve approximation using several points of δ determined by the formula. An example of the prediction is shown in Figure 5(d). The predicted value of δ during an accident may show an impossibly large value for the actual δ. However, at times when an accident is not occurring, the future value of δ is predicted. For this reason, the predicted value is not used to determine step-out during an accident. In order to accurately detect a step-out phenomenon using the method described above, it is necessary to reliably detect the occurrence of an accident.

[0005] Conventionally, the occurrence of an accident has been detected by detecting that the electric power P decreases when an accident occurs and returns when the accident is removed. Since P is constantly changing in the power system, the average value of P over a certain period of time is used as the power reference PM, and by detecting changes in P with respect to PM, a drop in power or a recovery is detected. FIG. 6 shows the change in power P from the occurrence of the accident until its removal. Average value of power P shown in FIG. 6 PM 2
0, if the drop in power PM 21 is greater than a certain value α, an accident occurs according to equation (3) 91D1 24
shall be. Here, PM is the average value of P for 1 second when there is no accident. When the power recovery ΔPUP23 is equal to or greater than a certain value β with respect to the maximum power drop ΔPMAX 22 during the accident, the accident is removed 91D2 25 according to equation (4). Figure 7 shows a conventional accident detection method. That is, as shown in FIG. 7, the accident occurrence 91D1 determined by equation (3)
24 Accident elimination determined by formula (4) 91D2 2
The period up to 5 is determined to be 27 during the accident.

[0006]

[Problems to be Solved by the Invention] It is known that in actual power system accidents, there are fluctuations in the power at the time of the accident. FIG. 8 shows an example of power changes from the occurrence of an accident to the removal of the accident. The average value of power PM is 20, and the value during the actual accident is 31.
, the electric power is 20a, the detection of the occurrence of an accident using the formula (3) is 24a to 24d, the detection of accident elimination using the formula (4) is 25a to 25c, and the detection of the accident during an accident using the conventional method (the method shown in FIG. 7) is 27a to 27c. Shown below. When an accident occurs and the electric power 20a fluctuates, accident occurrence (24a to 24d) and accident removal (25a to 25a) occur accordingly.
25d) is detected. If an accident is detected using the method shown in Figure 7, one accident will be detected as an accident (27a to 27d).
) is detected three times. For this reason, the time period (28a to 28
d) occurs.

[0007] If there is a time period during which it is determined that an accident is not occurring even though an accident is occurring, the power protection device described above for stabilizing the system cannot accurately predict system fluctuations. There is a possibility of making an incorrect judgment. In order to eliminate false judgments, it is necessary to reliably detect when an accident is occurring. The present invention was made to solve the above-mentioned drawbacks, and an object of the present invention is to provide a power system protection device that can reliably detect an accident.

[0008]

[Means for Solving the Problems] In order to solve the above object, the power system protection device according to the present invention includes a first means for holding the detection for a certain period of time after detecting the occurrence of an accident, and a first means for detecting the accident removal. The vehicle is configured to include means for detecting that the second means has output after a predetermined time after the outputs of the second means and the first means, and determining that an accident is occurring during that time. [Operation] As an example of power at the time of an accident, there is a phenomenon in which the power fluctuates rapidly at the beginning of the accident, the power fluctuations gradually converge, and the power is restored when the fault is removed. In the power system protection device according to the present invention, when an accident accompanied by power fluctuations as described above occurs, when the power fluctuations are severe in the initial stage of the accident occurrence, the occurrence of the accident and the removal of the accident are detected alternately. Further, in the process of convergence of power fluctuations, the occurrence of an accident is detected, and the removal of the accident is no longer detected. At the time of accident removal, only the accident removal is detected. In order to deal with such a phenomenon, the occurrence of an accident can be reliably detected by providing means for holding the detection for a certain period of time after detecting the occurrence of an accident. The operation of the accident determination method will be explained below. As shown in FIG. 8, a case will be described in which an accident occurs accompanied by power fluctuations in which the power fluctuations are large at the beginning of the accident occurrence and the fluctuations gradually become smaller. Accident occurrence and accident removal are performed in the same manner as before. That is, as shown in FIG. 6, when there is a drop in power PM-P21 of a constant value α or more with respect to the power average value PM 20, it is determined that an accident has occurred 91D1 24 according to equation (3). ΔP of power for the maximum value of power drop during an accident ΔPMAX 22
When UP23 is equal to or greater than a certain value β, the accident is removed 91D2 25 according to equation (4).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention based on the above-described operation will be described below with reference to the drawings. FIG. 1 shows an example of the configuration of a power system protection device according to the present invention. In FIG. 1, parts that are the same as those in FIG. 4 are given the same reference numerals, and description thereof will be omitted. 12a is the accident detection section, 12b
1 is an accident removal detection section, and 17 is an accident detection section. Here, the accident detecting section 17 includes an accident occurrence detection holding section 13a, an accident detection priority section 13b, and an accident record holding section 13c. The accident detection unit 12a includes the power average value calculation unit 11
The occurrence of an accident is detected using equation (3) from the average value of the power calculated in b and the power calculated in the power calculation unit 11a. The accident removal detection unit 12b includes the power average value calculation unit 1
The occurrence of an accident is detected using equation (4) from the average value of the power calculated in step 1b and the power calculated in power calculation section 11a.

Accident detection section 12a and accident removal detection section 1
The signal detected by 2b is used to detect the occurrence of an accident by the accident detection section 17. That is, when the accident occurrence 91D1 is detected, the accident occurrence detection and holding section 13a holds the accident occurrence signal for a certain period of time. When the occurrence of an accident is detected, the signal of the accident detection 14 is set by the output of the accident record holding section 13c. Further, when accident removal is detected, the output of the accident record holding section 13c is canceled and the signal of the accident detection 14 is canceled only when there is no accident detection signal.

FIG. 2 is a block diagram of another embodiment of the accident detection section. Figure 2(a) shows the accident occurrence detection holding unit 13 in Figure 1.
a is replaced with an accident occurrence detection extension section 51. FIG. 2(b) shows the case in which the accident removal holding section 52 of FIG. 1 is inserted. FIG. 2(c) shows an arrangement in which the accident occurrence detection holding section 13a in FIG. 1 is replaced with an accident occurrence detection extension section 51, and an accident removal holding section 52 is added in FIG. 1 to obtain the same effect as the present invention. be. Figure 2(d)
In this example, an accident removal stretching section 51 is added to FIG. 1 to obtain the same effect as the present invention. Note that FIG. 3 is a diagram showing an example in which a signal during an accident is used in an actual device. In other words, if there is a signal indicating an accident, the input conditions of the logic element 32 remain intact, and the output of the element 31 that is valid when there is no accident cannot be derived.

0012

As described above, according to the present invention, it is possible to provide an extremely reliable power system protection device that can reliably detect an accident in the power system.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a configuration example of a power system protection device to which the fault detection method of the present invention is applied.

FIG. 2 is a configuration diagram of another embodiment of the accident detecting section.

FIG. 3 is a diagram showing an example of how a signal during an accident is used in an actual device.

FIG. 4 is a diagram illustrating a conventional device.

FIG. 5 is a diagram for predicting step-out.

FIG. 6 is a diagram showing power changes during an ideal accident, and shows accident occurrence detection, accident removal detection, and movement during an accident.

FIG. 7 is a diagram showing an example of a conventional accident determining method.

FIG. 8 is a diagram illustrating an example of power change during an accident in an actual system, and showing detection of accident occurrence, detection of accident removal, and movement during the accident.

[Explanation of symbols]

10 Current/voltage intake section 11a Power calculation section 11b Power average value calculation section 12a Accident detection section 12b Accident removal detection section 13a Accident detection holding part 13b Accident detection priority section 13c Accident Record Department 14 Accident detection 15a　　　Measurement current transformer 15b Instrument transformer 16　Device 17 Accident detection unit

Claims (1)

[Claims] [Claim 1] A means for calculating power by taking in voltage and current from a power system, a first means for detecting a decrease in power and determining that an accident has occurred, and a first means for detecting that power has been restored. A second means for determining that the accident has been eliminated, and a means for detecting that the second means is output after a predetermined time after the output of the first means and determining that an accident is occurring during that time. A power system protection device characterized by: