JPH09261839A - Protection relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable protection while distinguishing an accident current generated in power system from noises such as surge caused by switching. SOLUTION: In order to neglect the judgement output of a first wave of input electric amount just after system accident generation, a term is previously set in an amplitude value operating means 12. In the term, sampled values of the input electric amount are added in the amplitude value operating means 12. When it is judged by a judging means 13 that the operated amount corresponding to the calculated amplitude value of the input electric amount exceeds a constant value (k), the output of the judging means is made continuous by an off-delay timer 16 having a previously selected first delay time. The output of the off-delay timer 16 is operation-delayed by an on-delay timer 17 having a previously selected second delay time. The logic product of the output of the on-delay timer 17 and the output of the judging means 13 is made continuous by a second off-delay timer 19 having a previously selected third delay time, and outputted as a protective command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective relay that avoids erroneous detection due to a surge or the like generated in a power system and detects an accident that has occurred in the power system at high speed.

[0002]

2. Description of the Related Art When an accident such as a short circuit or a ground fault occurs in a power system, it causes damage to power equipment, interruption of power supply, and the like, and the effects thereof are great. When a system accident occurs, this accident can be detected at high speed and the accident point can be quickly separated from the power system to minimize the spread of damage and to continue the stable power supply. desired.

On the other hand, noise is generated in the system such as lightning and surge due to opening / closing of the system circuit. This noise is too large to handle accidents. However, in the protective relay device, erroneous detection due to noise may occur. It is the responsibility to avoid and detect only the system fault reliably and at high speed.

In recent years, along with the progress of digital technology, various types of protection relays have been made into digital relays, and the detection speed of system faults has been greatly improved compared to the conventional one. FIG. 7 is a block diagram of a digital relay. E in FIG.
Is a power supply, which supplies power to the grid through the breaker CB. CT is an instrument current transformer, and introduces the current flowing in the system L into the protective relay 1. In this protective relay 1, the current i introduced from the current transformer CT for the instrument is sampled at a constant cycle through the analog / digital converter (A / D) 2 and converted into a digital amount.

The central processing unit (CPU) 3 follows the above-mentioned digital amount and data memory (RAM) 5 according to a program previously stored in a program memory (ROM) 4.
When the amplitude value is calculated using and, and as a result, an excessive current due to a system fault is detected, the output unit (OUT)
A protection command 7 is issued from 6 to CB. Note that FIG. 8 shows one of the output characteristics of the protective relay, and as shown in FIG. 8, the delay time determined by the magnitude of the amplitude value of the input current also has an inverse time characteristic.

As a means for avoiding erroneous detection due to noise such as surge, the conventional configuration is shown in FIG. In FIG. 9, the digital / analog converted sample value is stored in the data memory 11, and the amplitude value calculation means 12 calculates a calculation amount corresponding to the amplitude value of the input electric quantity.

Here, the calculation executed by the amplitude value calculation means 12 is a well-known addition type amplitude value calculation, and the average value of the input electric quantity is calculated from the sample value in the half cycle or the period of an integral multiple of the half cycle. It is to be calculated.

When the calculation amount | P _m ″ | calculated by the amplitude value calculating means 12 is judged to be larger than the constant k ″ which is previously selected by the judging means 13, there is a preselected time limit. A protection command is output via the on-delay timer (TDE) 14.

[0009]

The on-delay timer 14 has a role of distinguishing whether the determination result of the determination means 13 is due to noise or a system fault, and its time is It was necessary to consider the amount of calculation | P _m ″ | until the influence of noise was removed.

In other words, as a means for surely determining a system fault, it is a condition that an input of an excessive amount of electricity continues for a certain time or longer.
The detection time was delayed by 14 hours.

The present invention has been made to solve the above problems, and reliably distinguishes a fault current generated in a power system from noise such as lightning and surges caused by opening and closing of a system circuit, and prevents a system fault. It is an object of the present invention to provide a protective relay that can detect an accident at high speed in some cases.

[0012]

A protective relay according to claim 1 of the present invention comprises a data memory for sampling an input quantity of electricity at a constant time interval and taking in analog / digital converted sample values, and a preselected one. Amplitude value calculating means for adding the sample values of the input electric quantity in the first period and calculating the calculation quantity corresponding to the amplitude value of the input electric quantity, and the calculation quantity calculated by the amplitude value calculating means are selected in advance. A reset delay timer having a first preselected delay time for inputting the judgment output of the judgment means, and the output of this return delay timer. The operation delay timer having a second delay time selected in advance and the output of this operation delay timer and the output of the judging means are ANDed and the output of this AND is input. A second return delay timer having a third delay time that is preselected that, and means for outputting the output of the second return delay timer as Protection Directive.

According to another aspect of the protection relay of the present invention, a sample of the input electricity quantity during a period preselected by the amplitude value computing means is ignored so as to ignore the determination output of the first wave of the input electricity quantity immediately after the occurrence of the system fault. When the determination unit determines that the calculation amount corresponding to the calculated amplitude value of the input electric amount exceeds the constant value k, the output of the determination unit is set to the first delay selected in advance. It is made continuous by an off-delay timer having time, the output of this off-delay timer is delayed by an on-delay timer having a second delay time selected in advance, and further the output of this on-delay timer and the output of the judging means are provided. This output is made continuous by a second off-delay timer having a preselected third delay time and output as a protection command.

In short, since the judgment result for the first wave of the input electric quantity immediately after the occurrence of the system fault is ignored, in the case of a surge input in which only one wave is generated, the output of the judgment means Is not output as a protection command, and in the case of a continuous and excessive amount of electricity generated by a system accident, that is, in the case of a continuous alternating current waveform, etc. At the same time, it becomes possible to output a protection command. Therefore, it is possible to avoid erroneous detection by the amount of electricity generated by the surge and to reliably and quickly detect the occurrence of a system fault.

A protective relay according to a second aspect of the present invention samples an input electric quantity at a constant time interval and outputs an analog / analog signal.
Amplitude value calculation means for adding a data memory for fetching digitally converted sample values and a sample value of the input electric quantity in the first period selected in advance to calculate an arithmetic quantity corresponding to the amplitude value of the input electric quantity. And a protection relay having a judgment means for outputting when the amount of calculation calculated by the amplitude value calculation means is larger than a preselected constant, a preselected first delay for inputting the judgment output of the judgment means. A return delay timer having time, an operation delay timer having a preselected second delay time for inputting the output of the return delay timer, and a logical product of the output of the operation delay timer and the output of the judging means are obtained. Then, a first circuit including a second return delay timer having a third delay time selected in advance for inputting the output of the logical product, and the output of the data memory of the first circuit. Connected to that, by adding the sample values of the electric quantity of the second period selected longer than the first period,
Second amplitude value calculation means for calculating a calculation quantity corresponding to the amplitude value of the input electric quantity, and a second amplitude value calculation means for outputting when the calculation quantity calculated by the amplitude value calculation means is larger than a second constant selected in advance. A second circuit including a judging means, and a second logical product is obtained from the output of the second return delay timer and the output of the second circuit, and the output of the second logical product is obtained. And means for outputting as a protection command.

According to a third aspect of the present invention, in the protective relay according to the second aspect, the output of the second determining means is connected to a second operation delay timer having a preselected fourth delay time,
The output of the second operation delay timer and the output of the second return delay timer having a preselected third delay time are processed by logical sum, and the output of this logical sum is output as a protection command. Equipped with means.

According to a fourth aspect of the present invention, in the protective relay according to the third aspect, the second operation delay timer is replaced with a counter time limit timer having a delay time determined by the magnitude of the amplitude value of the input electric quantity. .

[0018]

FIG. 1 is a block diagram showing an embodiment of a protection relay according to the present invention. Further, since the entire structure of the protective relay is the same as that shown in FIG. 7, the description thereof will be omitted. Note that FIG. 1 is a functional block diagram illustrating an on-delay timer, an off-delay timer, and a logical product process that ignores the determination output of the first wave of the input electric quantity immediately after the occurrence of the system fault.

In FIG. 1, a sample value of an input electric quantity converted into a digital quantity by an analog / digital converter is taken in and stored in a data memory 11. It should be noted that in FIG. 1, it is represented as a sample value P _{m for} each time sampled at a constant time interval and subjected to analog / digital conversion.

The sampled values stored in the data memory 11 are added by the amplitude value calculating means 12 to n sample values in a preselected period as shown in the equation (1), and the calculation corresponding to the amplitude value of the electric quantity. Calculate the quantity | P _m |. Further, the judging means 13 makes a judgment based on the equation (2).

[Formula 1] | P _m | = | P _m | + | P _m-1 | + | P _m-2 | + ... + | P _mn | ... (1) | P _m | ≧ k …………………………………… (2)

The determination output of the determination means 13 becomes an intermittent output when the sample number n is reduced. This output is made continuous in the off-delay timer (TDD1) 16, and its output is passed through the on-delay timer (TDE1) 17 to the TDE1.
The logical product of the output and the output of the overcurrent detection determination means 13 (AN
D) By taking the logical product in 18, the judgment output of the input electric quantity immediately after the system fault is ignored.

With respect to the amount of electricity continuously input, it is intermittently output after a time determined by TDE1. Therefore, the output of the logical product (AND) 18 is further made continuous by the off-delay timer (TDD2) 19 and the protection command 20 is issued, so that only an excessive amount of electricity that is sustainable at the time of a system fault can be reliably and at high speed. It becomes possible to detect.

FIG. 2 is a time chart of the functions of FIG. 1 executed in the central processing unit. The figure shows the signal state in each process of the on-delay timer and the off-delay timer that ignores the first wave of the input current immediately after the occurrence of the system fault, and the protection relay that has the process of the logical product. The case of “present” is expressed as “1”.
The figure shows the operation timing of each output when an alternating current is input.

First, the amplitude value calculation means 12 calculates the amount of calculation corresponding to the amplitude value by using n sample values in a preselected period. The determination means 13 makes a determination based on the equation (2) using this calculation amount, and outputs the result. The off-delay timer (TDD1) 16 receives this output, delays the return for the first time t1 selected in advance, that is, outputs the result of the determination means in a continuous manner.

Next, the off-delay timer (TDD1) 16
Is output to the on-delay timer (TDE1) 17, which delays the operation for the second time t2 selected in advance and outputs the delayed signal. Next, a logical product (AND) 18 executes a logical product process of the output of the on-delay timer (TDE1) 17 and the output of the judging means 13, and outputs the result.

When the input electric quantity is not continuous, for example, a surge current input, by performing this logical product processing, the time t1 of the off-delay timer (TDD1) 16 is increased.
On delay timer (TDE1) 17 time t2 and (2)
When the relation of the time α for which the expression is satisfied is t1 + α> t2, the output delayed by the off-delay timer (TDD1) 16 is delayed by t2 of the on-delay timer (TDE1) 17.
It becomes a later output, and it becomes possible to prevent this output from being output as a protection command.

When t1 + α≤t2, this logical product process is not particularly required, but t2 needs to be longer than half a cycle. That is, this logical product process has a function of determining whether or not the input electric quantity has continuity, and by executing this logical product process, t2 of the on-delay timer (TDE1) 17 is t1, t2, and It is possible to reduce the time to a half cycle or less without being influenced by the relationship of α.

The output of the logical product (AND) 18 is made continuous by an off-delay timer (TDD2) 19 which performs a return delay for a preselected third time t3, so that the judgment output of the first wave is obtained. It is possible to ignore and output the judgment output of the second and subsequent waves as the protection command 20.

On the other hand, FIG. 3 is a time chart showing a surge current input, and an on-delay timer (TDE1) 17
The operation timing of the output up to is similar to that of the description of FIG. For a surge current input that does not have continuity, the output of the AND (AND) 18 of the output of the on-delay timer (TDE1) 17 and the output of the judgment process becomes "0", and as a result, the protection command is not output. It is possible to avoid erroneous detection due to surge.

As described above, according to the present embodiment, when an excessive current is generated due to a system fault, it is possible to output a protection command at high speed after the system fault is detected by the judging means. In addition, it is possible to prevent erroneous detection due to surge current input.

In the above embodiment, the number of sample values used for calculating the amount of calculation corresponding to the amplitude value is expressed as n. However, this number n is not particularly fixed and the protective relay is not fixed. Should be commensurate with the required detection speed.

That is, in order to increase the detection speed, the value of n may be decreased. For example, the highest speed in the above-described embodiment is when the amount of calculation corresponding to the amplitude value is calculated from one sample value, and when n = 1, extremely high-speed detection is possible.

Further, in the above embodiment, the time of the off-delay timer (TDD1) 16 is expressed as t1. However, this time t1 is not particularly fixed and the output of the overcurrent detection judging section is made continuous. Any value will suffice.

Further, the on-delay timer (TDE1) 17
Although the time t2 is expressed as t2, this time t2 is not particularly fixed, and may be any time as long as it is possible to sufficiently avoid surge input and is less than the detection time allowed by the protective relay.

Furthermore, an off-delay timer (TDD2)
Although the time of 19 is expressed as t3, this time t3 is not particularly fixed and may be any value that is sufficient to make the protection command continuous. If the continuation of the protection command is unnecessary, omit it. May be.

Further, in the above-mentioned embodiment, the input electricity quantity at the time of a system fault is explained by the AC current waveform, but the input electricity quantity is not particularly limited to the AC current waveform, and the needle wave current flowing in the arrester It may be corrugated. FIG. 4 shows a time chart when a needle-shaped current waveform is input.
The state of each output is the same as when the AC current waveform is input, and the same effect can be obtained even when the input electricity amount is the needle current waveform.

Furthermore, in the above-described embodiment, the input electric quantity at the time of a system fault is an alternating current waveform or a needle wave current waveform, but the present invention is not limited to this, and the input electric quantity is a square wave, Even when a special waveform such as a sawtooth wave or a DC waveform is used, the signal state in each process is the same, and the same effect as that of the above-described embodiment can be obtained.

FIG. 5 is a block diagram showing another embodiment of the protective relay according to the present invention. Data memory in the figure
11, amplitude value calculation means 12, determination means 13, off-delay timer (TDD1) 16, on-delay timer (TDE1) 1
7, logical product (AND) 18, off-delay timer (TDD
2) The functions of 19 and protection command 31 have the same functions as those described in FIG.

Then, the amplitude value calculating means 21 uses the n'sample values, which are the number of the second periods longer than the preselected period described in the above-mentioned embodiment, as shown in the equation (3). The calculation amount | P _m ′ | corresponding to the value is calculated. Further, the judging means 22 makes a judgment based on the equation (4), and outputs it when it is judged to be a system fault.

[Formula 2] | P _m ′ | = | P _m | + | P _m-1 | + | P _m-2 | + ... + | P _mn ′ | ………… (3) | P _m ′ | ≧ k ' ………………………………………(Four)

Then, a logical product (AND) 30 of this output and the output of the off-delay timer (TDD2) 19 is output as a protection command 31. In the above embodiment, an example in which the number n of sample values used to calculate the amount of calculation corresponding to the amplitude value is reduced in order to increase the detection speed has been described. However, reducing n decreases the detection speed. Although the speed can be increased, the detection level of Eq. (2) decreases.

In order to prevent this decrease in the detection level, the detection sensitivity k of the judging means 13 is set to high sensitivity, and the amount of calculation using the sample value of the number n'of the second period as in the present embodiment is used. Is determined by the determination means 22 to obtain the output of the logical product (AND) 30, the detection speed can be improved and the detection accuracy can be further improved.

It should be noted that the deciding means 22 may erroneously detect the surge input, but the output of one of the off-delay timers (TDD2) 19 does not output to the surge input, which is a particular problem. It never becomes.

FIG. 6 is a block diagram showing another embodiment of the protective relay according to the present invention. In this example, instead of using the protection command 31 of the embodiment of FIG. 5 as the output of the logical product (AND) 30 of the off-delay timer (TDD2) 19 and the output of the judging means 22, the output of the judging means 22 is changed. Preselected time limit t4
This output, the output of the off-delay timer (TDD2) 19 and the logical sum (OR) 33 are used as protection commands via the on-delay timer (TDE2) 32 of FIG.

In this example, the decrease in the detection level of the above-mentioned expression (2) is made up by the expression (4), and the detection sensitivity k of the judging means 13 remains unchanged, and the detection of that point is judged. It is carried out by means 22.

The magnitude of the current that requires detection accuracy is
It is near the limit of equation (4), and the current itself is small. Therefore, in order to prevent the malfunction of the equation (4) due to the surge input, there is no problem even if only the time of false detection due to the surge input is delayed by the time period t4 of the on-delay timer (TDE2) 32 and then output.

Further, although the timer of the above embodiment is an on-delay timer of a preselected time period, instead of this, an anti-time period having a delay time determined by the magnitude of the amplitude value of the input current as shown in FIG. It may be a timer.

Furthermore, in each of the above-mentioned embodiments, the protection relay in which the input waveform is the current is used, but the input is not limited to the current and high-speed detection is required, and erroneous detection due to noise may occur. A protective relay having an input voltage may be used as long as it requires protection. According to this example, malfunction can be prevented.

[0048]

As described above, according to the present invention, the judgment output is divided into the output through the processing of the off-delay timer and the on-delay timer having the preselected delay time and the output of the logical product of the judgment output. By using the judgment output of the judgment processing so as to ignore the first wave of the input electric quantity after the system fault, an accident occurring in the power system, a lightning current, a surge current input due to switching of the system circuit, etc. Definitely distinguish,
Moreover, in the case of a system accident, it can be detected at high speed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a protective relay according to the present invention.

FIG. 2 is a time chart of the present invention when the input is an alternating current.

FIG. 3 is a time chart of the present invention when the input is a surge current.

FIG. 4 is a time chart of the present invention when the input is a needle wave current.

FIG. 5 is a configuration diagram showing another embodiment of the protective relay according to the present invention.

FIG. 6 is a configuration diagram showing another embodiment of the protective relay according to the present invention.

FIG. 7 is a basic configuration diagram of a digital relay.

FIG. 8 is a time characteristic diagram of a counter time limit timer.

FIG. 9 is a configuration diagram of an embodiment of a conventional technique.

[Explanation of symbols]

 1 protection relay 2 analog / digital conversion unit 3 central processing unit 4 program memory 5, 11 data memory 6 output unit 7, 15, 20, 31 protection command 12, 21 amplitude value calculation means 13, 22 judgment means 14, 17, 32 On-delay timer 16, 19 Off-delay timer 18, 30 Logical product 33 Logical sum

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shuichi Gondo 1-24-2, Harumi-cho, Fuchu-shi, Tokyo Inside Toshiba System Technology Co., Ltd.

Claims (4)

[Claims] 1. A data memory for sampling an input electric quantity at a constant time interval and taking in analog / digital converted sample values, and adding a sample value of the input electric quantity in a preselected first period, In a protective relay having an amplitude value calculation means for calculating a calculation quantity corresponding to an amplitude value of an input electricity quantity, and a judgment means for outputting when the calculation quantity calculated by the amplitude value calculation means is larger than a preselected constant A return delay timer having a preselected first delay time for inputting the judgment output of the judging means, and an operation delay timer having a preselected second delay time for inputting the output of the return delay timer , A second return delay having a third delay time selected in advance to obtain the logical product of the output of the operation delay timer and the output of the judging means and input the output of the logical product A protective relay comprising a timer and means for outputting the output of the second return delay timer as a protection command. 2. A data memory for sampling an input electric quantity at a constant time interval and taking in analog / digital converted sample values, and adding a sample value of the input electric quantity in a first period selected in advance, In a protective relay having an amplitude value calculation means for calculating a calculation quantity corresponding to an amplitude value of an input electricity quantity, and a judgment means for outputting when the calculation quantity calculated by the amplitude value calculation means is larger than a preselected constant A return delay timer having a preselected first delay time for inputting the judgment output of the judging means, and an operation delay timer having a preselected second delay time for inputting the output of the return delay timer , A second return delay having a third delay time selected in advance to obtain the logical product of the output of the operation delay timer and the output of the judging means and input the output of the logical product A first circuit composed of a timer and an output stage of the data memory of the first circuit,
The second amplitude value calculating means for adding the sample value of the electric quantity in the second period selected longer than the above period to calculate the calculation quantity corresponding to the amplitude value of the input electric quantity, and the amplitude value calculating means. And a second circuit configured to output when the calculated amount of calculation is larger than a second constant selected in advance, the output of the second return delay timer and the second circuit.
And a means for taking a second logical product with the output of the circuit and outputting the output of the second logical product as a protection command. 3. The output of the second judging means is connected to a second operation delay timer having a preselected fourth delay time, and the output of the second operation delay timer and the preselected third
3. The protective relay according to claim 2, further comprising means for processing a logical sum with an output of a second return delay timer having a delay time of, and outputting the output of the logical sum as a protection command. 4. The protective relay according to claim 3, wherein the second operation delay timer is replaced with an anti-time limit timer having a delay time determined by the magnitude of the amplitude value of the input electric quantity.