JP3496998B2 - Power fluctuation detection device for power system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power fluctuation detecting device for blocking a cutoff command output from a protective relay device in response to a power fluctuation detection output in a power system.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram including a power fluctuation detecting device of a power system shown in a prior application (filed on Apr. 27, 2006) filed by the applicant of the present application. This power fluctuation detection device includes an impedance change rate detection circuit, an accident detection timer, and a cancellation circuit, and has a function of canceling the interruption command output inhibition by the power fluctuation detection by detecting an accident during power fluctuation.

In FIG. 5, the protective relay device 1 has a short-circuited first-stage moire relay 3-5, a short-circuited second-stage moire relay 6-8 and a short-circuited 3
Stage Morrelays 9-11, AND circuits 13-15, 1-stage output OR circuit 16, 1-stage protected output inhibit circuit 17, AND circuits 18-20, 2-stage output OR circuit 21, and 3-stage output OR circuit 22. And a two-stage protection timer 23 constituting a time-delay operation circuit, a three-stage protection timer 24 constituting a time-delay operation circuit, a two-stage protection output AND circuit 25, and a shutoff command output OR circuit 26. The power fluctuation detection device 2 includes a short circuit offset mode relay 12, an OR circuit 27 for three-stage protection output, a prohibition circuit 28, a power fluctuation detection timer 29 that constitutes a time delay operation circuit, and a power fluctuation detection that constitutes a time delay operation / time delay reset circuit. The holding timer 30, the power oscillation detection output OR circuit 31, the impedance relay 32, the accident detection timer 33, and the release circuit 34 are provided. Impedance relay 32 constitutes an impedance change rate detection circuit that detects the rate of change of impedance due to current and voltage of the power system, and operates if the rate of change (change width) is a certain value or less. The accident detection timer 33 is connected to the output of the impedance relay 32, and the release circuit 3
Numeral 4 is a prohibition circuit which receives the output of the accident detection timer 33 as a prohibition input and also receives the output of the power oscillation detection output OR circuit 31 as an input, and the output of the release circuit 34 is the one-stage protection output of the protection relay 1. It is input to the prohibition input of the use prohibition circuit 17. The impedance relay 32 is, specifically, | R (t) -R (t-180) | <0.5Ω ... (1) | X (t) -X (t- 180) | <0.5Ω ... In the above formula, R
(T) and X (t) represent the resistance component and the reactance component of the impedance, respectively, and R (t-180), X (t-18)
0) shows the data before half cycle. Therefore, in FIG. 7, for example, if F3 = 10Ω and F4 = 2Ω,
The equation (1) is not satisfied, and the equation (2) is satisfied, so that the impedance relay 32 does not operate. Also, F3 = 10
If Ω and F4 = 9.6Ω, both equations (1) and (2) are established, and therefore the impedance relay 32 operates.

Next, the operation of this conventional example will be described with reference to FIG. When the power fluctuation occurs in the power system, the change in the current and the change in the voltage change more slowly than those at the time of the power system failure, and follow the impedance locus as shown in FIG. According to the impedance locus at the time of shaking, the short circuit offset mode relay 12 at the time t1.
After the operation of the
1 works. If the time difference t1-t2 between the operation time t1 and the operation time t2 is equal to or greater than the time limit operation value of the power fluctuation detection timer 29, it is considered that power fluctuation is occurring in the power system, and the power fluctuation detection device 2 Is output to the prohibition input of the one-stage protection output prohibiting circuit 17 by outputting a power fluctuation detection output of "1" having a high potential, the protection relay device 1 outputs the interruption command unnecessarily. 2 blocks in advance. In addition, even when the impedance locus during oscillation shown in FIG. 6 moves from within the protection range of the short circuit mode relays 9 to 11 to outside the protection range of the short circuit offset mode relay 12, the power oscillation detection device 2 causes the oscillation detection holding timer 3 to operate.
By outputting a low-potential power fluctuation detection output of "0" after the time limit recovery of 0 to the prohibition input of the one-stage protection output prohibition circuit 17, the protection relay device 1 returns to a state in which it can output the cutoff command. .

On the other hand, when an electric power system fault occurs within the protection range of the short circuit relays 9 to 11 during the detection of the power fluctuation, the locus of the impedance, which has been slowly changing until then, becomes the fault point F1 as shown in FIG. Moving. Accident point F
Since the impedance of 1 has a substantially constant value, the impedance relay 32 detects the power system fault, the detection timer 33 operates for a fixed time after a fixed time, and the OR circuit 3
The release circuit 34 releases the high-potential “1” power fluctuation detection output to the protective relay device 1 due to 1. As a result, the two-step protection timer 23 and the three-step protection timer 24 are protected regardless of the magnitude of the time-limit return of the operation detection holding timer 30 and the time-limit operation of the two-step protection timer 23 and the three-step protection timer 24. After the time delay operation or without waiting for the time detection reset of the operation detection and holding timer 30, the shutoff command output OR circuit 26 outputs the shutoff command.

Further, following the distant electric power system accident indicated by the symbol F2 in FIG. 6 in which the short-circuit offset relay 12 operates and the short-circuit relays 9 to 11 do not operate, the short-circuit offset relays 9 to 11 are coded within the protection section. When a power system fault indicated by F1 occurs, the impedance relay 32 detects the fault at the fault point F1 in the same manner as described above, so that the detection timer 33 operates for a time limit and a certain delay occurs due to this time limit action. After a lapse of time, the detection timer 33 outputs a high potential "1" to the prohibition input of the AND circuit 34, and the AND circuit 34 outputs a high potential "1" to the protection relay device 1 by the operation detection output OR circuit 31. The power fluctuation detection output is canceled and the time detection return of the operation detection holding timer 30 and the time delay operation of the two-step protection timer 23 and the three-step protection timer 24 are related to each other. Without after time limit operation of the two-stage protective timer 23 and 3-stage protection for the timer 24, or, without waiting for the time limit return operation detection holding timer 30,
The shutoff command output OR circuit 26 outputs a shutoff command.

Further, even when a one-phase ground fault accident occurs in the protection section of the ground fault protection device (not shown), the protection range of the short-circuit offset Moh relay 12 is wide, so that the short-circuit offset Moh relay 12 operates. , System power operation detection device 2
Outputs a system operation detection output having a high potential of "1" to the prohibition input of the one-stage protection output prohibition circuit 17, and the cutoff command of the protection relay device 1 is unnecessarily blocked. When a system fault of two or more phases continues after such a one-phase ground fault, the AND circuit 34 detects the system fault and the AND circuit 34 causes the operation detection output OR circuit 31 to operate in the same manner as described above. Since the blocking signal to the protective relay device 1 due to is released, the shutoff command output OR circuit 26 outputs a shutoff command.

[0008]

Since the conventional power fluctuation detection device is constructed as described above, the interruption prevention is canceled by the impedance detection by the impedance relay (impedance change rate detection circuit) even after the power fluctuation is detected. ,
Although highly reliable, in the impedance relay detection method, a change in the data of the resistance component and the reactance component half cycle before is determined by a certain reference value (0.5% in the conventional example).
Ω) was used to make a determination, so
There is a problem in that it may be difficult to detect an accident when the power fluctuation of the power system progresses slowly, and it is very difficult to set a criterion for judging the rate of change.

The present invention has been made in order to solve the above problems, and provides a power fluctuation detecting apparatus for a power system, which enables stable accident determination even when the impedance change speed during power fluctuation of the power system is slow. The purpose is to get.

Another object of the present invention is to obtain a power fluctuation detecting device for a power system having a function of preventing erroneous detection of power fluctuation during a distant accident.

[0011]

A first aspect of the present invention provides an impedance change rate measuring circuit 50 for measuring the rate of change of impedance during power fluctuation detection and an impedance change rate detecting circuit (impedance relay 32). And an impedance change rate setting circuit 51 for setting a determination reference value for detecting the value according to the measurement value of the impedance change rate measurement circuit 50.

In the second aspect of the invention, the impedance change rate measuring circuit 52 measures the rate of change of the impedance during the fluctuation detection based on the difference between the impedance at the time of the power fluctuation detection and the impedance a certain time before the detection. It is characterized by doing.

According to a third aspect of the present invention, the difference between the impedance when the impedance locus enters the power fluctuation determination region and the impedance before a fixed time before the power fluctuation determination region enters,
An accident agitation determination circuit 5 that determines whether a power system accident or an electric power agitation is made based on the result of comparing the difference between the impedance after the power agitation determination and the impedance after a certain time after the determination.
3 is provided.

In the fourth aspect of the invention, the impedance change rate measuring circuit 50 calculates the rate of change of impedance during power fluctuation by measuring the time taken for the impedance locus during power fluctuation to pass through the power fluctuation determination region, and changes the impedance. The impedance change rate setting circuit 51 sets the rate of change in impedance for accident determination based on the rate.

In the fifth aspect of the invention, the impedance change rate measuring circuit 52 directly calculates the rate of change of the impedance when the power fluctuation is detected by a predetermined mathematical expression, and the impedance change rate setting circuit 51 uses the rate of change for accident determination. It is characterized in that the rate of change of the impedance of is set.

[0016]

In the first aspect of the invention, the impedance change rate measuring circuit 50 determines the rate of change of impedance during power fluctuation detection.
The impedance change rate setting circuit 51 sets the determination reference value in the impedance change rate detection circuit (impedance relay 32) according to the measured value.
Therefore, the impedance change rate detection circuit detects the impedance change rate based on the determination reference value. This makes it possible to determine an accident even if the power fluctuation speed changes.

In the second invention, the impedance change rate during the power fluctuation detection is based on the difference between the impedance at the time of the power fluctuation detection and the impedance at a fixed time before the detection by the impedance change rate measuring circuit 52. Measured.

In the third aspect of the present invention, the power system accident or the power fluctuation is determined by determining the difference between the impedance when the impedance locus enters the power fluctuation determination region and the impedance before a certain time before the impedance locus, and after the power fluctuation determination. The difference between the impedance and the impedance before a fixed time after the judgment is compared by the accident shake judgment circuit 53, and the judgment of the accident is made based on the comparison result.

In the fourth aspect of the invention, the impedance change rate measuring circuit 50 measures the time taken to pass the power fluctuation judgment region of the impedance locus during power fluctuations, and the impedance change rate during power fluctuations corresponds to the passing time. The impedance change rate setting circuit 51 sets the change rate of the impedance for accident determination based on the calculated change rate.

In the fifth aspect of the present invention, the impedance change rate measuring circuit 5 determines the rate of change of impedance during power fluctuation.
2, the impedance change rate setting circuit 51 sets the change rate of the impedance for accident determination based on the change rate.

[0021]

Embodiments of the present invention will be described below. Example 1. 1 is a block diagram including a power fluctuation detecting device according to a first embodiment of the present invention. In FIG. 1, the protective relay device 1 includes a short-circuit 1-stage Mo relay 3 to 5, a short-circuit 2 stage Mo relay 6 to 8, a short-circuit 3 stage Mo relay 9 to 11, an AND circuit 13 to 15, a 1-stage output OR circuit 16 and 1 stage. Protective output prohibiting circuit 17, AND circuits 18 to 20, two-stage output OR circuit 21, three-stage output OR circuit 22, two-stage protection timer 23 forming a time-limit operating circuit, and three-stage forming a time-limit operating circuit A protection timer 24, a two-stage protection output AND circuit 25, and a shutoff command output OR circuit 26 are provided. The power fluctuation detection device 2 includes short-circuit offset mohre relays 12 and 3
Stage protection output OR circuit 27, prohibition circuit 28, and power fluctuation detection timer 29 that constitutes a time-delay operation circuit and time-delay operation
Timer 3 for power fluctuation detection and holding that constitutes the time delay recovery circuit
0, a power fluctuation detection output OR circuit 31, an impedance relay 32, an accident detection timer 33, and a release circuit 34. Impedance relay 32 constitutes an impedance change rate detection circuit that detects the rate of change of impedance due to current and voltage of the power system, and operates if the rate of change (change width) is a certain value or less. The accident detection timer 33 is connected to the output of the impedance relay 32, and the release circuit 34 serves as a prohibition circuit that receives the output of the accident detection timer 33 as a prohibition input and the power oscillation detection output OR circuit 31 as an input. The output of the release circuit 34 is input to the inhibition input of the one-stage protection output inhibition circuit 17 of the protection relay 1.

Further, an impedance change rate measuring circuit 50 and an impedance change rate setting circuit 51, which characterize the first embodiment, are provided. The impedance change rate measurement circuit 50 measures the rate of change in impedance during power fluctuation detection, includes a timer counter (not shown), and includes a count start signal from the short circuit offset mode relay 12 for power fluctuation detection and the short circuit mode relays 9 to 9. The count stop signal from 11 is input, and the time from the operation of the short circuit offset Mo relay 12 to the operation of the short circuit Morre relays 9 to 11 is measured by the timer counter, and the power fluctuation is based on the measured time. Measure the rate of change of impedance during detection. The impedance change rate setting circuit 51 sets a determination reference value for the impedance relay (impedance change rate detection circuit) 32 to detect the change rate of impedance according to the measurement value of the impedance change rate measurement circuit 50.

Next, the operation of the first embodiment will be described.
Here, the description of the same operation as the conventional example is omitted, and the characteristic operation is described. In order to simplify the description, the difference between the operating areas of the short circuit offset Mohre relay 12 and the short circuit Mohle relays 9, 10 and 11 is ΔZ as shown in FIG. 2 and is obtained by the timer counter of the impedance change rate measuring circuit 50. When the timer count time is ΔT, the impedance change rate obtained by the impedance change rate measuring circuit 50 at this time can be set to ΔZ / ΔT. The impedance change rate setting circuit 51 uses the rate of change in impedance for accident determination, for example, when looking at the change in impedance from a half cycle before the accident determination (ΔZ
/ ΔT) × (t0 / k1) is used as the determination reference value. Here, t0 is a half cycle time, k1 is a value of impedance change at the time of power fluctuation / impedance change at the time of power system failure, for example, if k1 = 10 is set, it is 1/10 of the impedance change at the time of power fluctuation. When the impedance changes, it can be judged as an accident. At this time, the impedance relay (impedance change rate measuring circuit) 32 can detect the impedance change rate based on the determination reference value from the impedance change rate setting circuit 51, and output a signal for determining whether power fluctuation or accident. It will be possible.

Here, as a judgment formula for judging whether the electric power is shaking or an accident

[0025]

[Equation 1]

There is The right side of this equation (3) is an equation showing the difference between the impedance at time t and the impedance half cycle before time t. In this way, power fluctuation and an accident can be determined simply by setting k1. Moreover, even if the power fluctuation is slow, it is possible to judge the accident.

Although the impedance change rate measuring circuit 50 is provided with the timer counter in the present embodiment, the method of counting at the calculation time interval (sampling interval) which is a feature of the digital relay may be used.

As described above, according to the first embodiment,
The impedance change rate during power fluctuation is calculated by measuring the time that the impedance locus during power fluctuation passes through the power fluctuation determination area, and the impedance change rate for accident determination is automatically set based on that rate of change. So let's
Even if the power fluctuation speed of the power system changes, it can follow up, and highly reliable accident determination can be performed.

Example 2. 3 is a block diagram including a power fluctuation detecting device according to a second embodiment of the present invention. In FIG. 3, the same components as those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 3, the power fluctuation detection device 2 includes an impedance at the time of power fluctuation detection,
An impedance change rate measuring circuit 52 is provided for measuring the rate of change in impedance during the detection of power fluctuation based on the difference from the impedance at a certain time before the detection. The impedance change rate measuring circuit 52 has an input connected to the output of the fluctuation detection timer 29 and an output connected to the input of the impedance change rate setting circuit 51.

Next, the operation of the third embodiment will be described.
Here, the description of the same operation as the conventional example is omitted, and the characteristic operation is described. The impedance change rate measurement circuit 52 inputs the output of the fluctuation detection timer 29, and changes the impedance during power fluctuation detection based on the difference between the impedance at the time of vibration detection and the impedance at, for example, a half cycle before this detection. Calculate the rate by the following formula.

[0031]

[Equation 2]

Here, tA represents the time when the output of the fluctuation detecting timer 29 is input to the impedance change rate measuring circuit 52. From this equation (4), the impedance change rate A during the half cycle at the time of motion detection is obtained by the impedance change rate measurement circuit 52 and input to the impedance change rate setting circuit 51. The impedance change rate setting circuit 51 sets the impedance change rate A to A / k1.
(K1 has the same meaning as in the first embodiment) and is input to the impedance relay 32.

[0033]

[Equation 3]

When the equation (3) is established, the accident determination signal is output from the impedance relay 32.

As described above, according to the second embodiment,
The impedance change rate at the time of power fluctuation detection is directly calculated by an equation, and the impedance change rate for accident determination is automatically set based on the value, which enables more accurate accident determination.

Example 3. 4 is a block diagram including a power fluctuation detecting device according to a third embodiment of the present invention. 4, the components corresponding to those shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 4, the power fluctuation detection device 2 includes a difference between the impedance when the impedance locus enters the power fluctuation determination region and the impedance before the constant time before the impedance fluctuation region, the impedance after the power fluctuation determination, and the constant after the power fluctuation determination. An accident agitation determination circuit 53 is provided for determining a power system accident or power agitation based on the result of comparison with the difference with the impedance before time. The accident shaking determination circuit 53 has two inputs connected to the input and the output of the shaking detection timer 29, and an output connected to the input of the cancellation circuit 34.

Next, the operation of the third embodiment will be described.
Here, the description of the same operation as the conventional example is omitted, and the characteristic operation is described. The accident shake determination circuit 53 calculates the difference B between the impedance values at the time of input and output of the shake detection timer 29 by the following formula.

[0038]

[Equation 4]

Here, tA is the time when the motion detection timer 29 outputs a signal, and tB is the motion detection timer 2.
9 shows the time when the signal is input. Also, tA-tB
= TC, the impedance difference C between time t and t-tC
Is calculated by the following formula.

[0040]

[Equation 5]

Here, the impedance differences B and C have almost the same value during power fluctuation, but the short circuit offset mode relay 12 and the short circuit mode relays 9, 10, 1 due to an accident after the fluctuation is detected.
Those that entered the sway determination area between 1 are | CB | >> 1
Becomes Therefore, it becomes possible to determine the accident by determining | CB−> k2 (k2 is set to 1 or more), and at this time, detection of power fluctuation is blocked.

As described above, according to the third embodiment,
Since the impedance change can be determined by constantly measuring the impedance change and comparing the impedance change before and after entering the power fluctuation judgment region with the impedance value, erroneous detection of the accident in the power fluctuation region can be prevented.

[0043]

As described above, according to the first aspect of the present invention, the impedance change rate during power fluctuation detection is measured, and the determination reference value of the impedance change rate detection circuit is set according to the measured impedance change rate. Since it is configured so that it can follow the power fluctuation speed of the power system, it can perform stable accident judgment even when the impedance change speed during power fluctuation is slow, and the reliability of the accident judgment can be improved. The effect that is improved is obtained.

According to the second invention, the impedance change rate measurement for measuring the impedance change rate during the power fluctuation detection based on the difference between the impedance at the time of the power fluctuation detection and the impedance at a fixed time before the detection. Since the circuit is provided, it is possible to measure the impedance change rate at the time of power fluctuation detection, and it is possible to achieve the effect of the first invention by making an accident determination using a determination reference value based on the change rate. To be

According to the third aspect of the present invention, since the accident determination can be performed by comparing the impedance value before and after entering the power fluctuation judgment area with the impedance value, the accident detection of the accident in the power fluctuation area can be performed. Therefore, it is possible to prevent erroneous detection even in the case of an accident such as a long-distance failure or a one-phase ground fault, and thus the reliability of the accident determination is improved.

According to the fourth aspect of the invention, the impedance change rate measuring circuit calculates the impedance change rate during power fluctuation by measuring the time taken for the impedance locus during power fluctuation to pass through the power fluctuation determination area. Since the impedance change rate setting circuit is designed to set the impedance change rate for accident determination based on the change rate, the impedance change rate for accident determination can be set automatically, and the power fluctuation speed can be set. Even if changes occur, it is possible to obtain the effect of being able to follow up and make a highly reliable accident determination.

According to the fifth aspect of the invention, the impedance change rate measuring circuit directly calculates the rate of change of the impedance when the power fluctuation is detected by a predetermined mathematical expression, and the impedance change rate setting circuit is used for the accident determination based on the change rate. Since the rate of change of the impedance is set, it is possible to obtain a more accurate accident determination even if the power fluctuation speed changes.

[Brief description of drawings]

FIG. 1 is a block diagram including a power fluctuation detection device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a locus of impedance and the like during power fluctuation in the first embodiment.

FIG. 3 is a block diagram including a power fluctuation detecting device according to a second embodiment of the present invention.

FIG. 4 is a block diagram including a power fluctuation detector according to a third embodiment of the present invention.

FIG. 5 is a block diagram including a conventional power fluctuation detection device.

FIG. 6 is a diagram showing a locus of impedance and the like during power fluctuation in a conventional example.

FIG. 7 is an operation explanatory view of an impedance relay in a conventional example.

[Explanation of symbols]

1 protection relay device, 2 power fluctuation detection device, 3-5 short-circuit 1-stage moi relay, 6-8 short-circuit 2-stage mor relay, 9-
11 short-circuited three-stage moh relay, 12 short-circuited offset moh relay (power fluctuation detection relay), 13, 14, 15, 1
8, 19, 20, 25 AND circuit, 16, 21, 2
2, 26, 27, 31 OR circuit, 32 impedance relay (impedance change rate detection circuit), 33 accident detection timer, 34 release circuit, 50, 52 impedance change rate measurement circuit, 51 impedance change rate setting circuit, 53 accident fluctuation judgment circuit.

Claims (5)

(57) [Claims] 1. A power fluctuation detection device for a power system, which blocks a cutoff command output from a protection relay device for protecting the power system according to a power fluctuation detection output of the power system, wherein the impedance of the power system is An impedance change rate detection circuit for detecting a change rate, an accident detection timer operated by the output of the impedance change rate detection circuit, and a logical product of the output of the accident detection timer and the power fluctuation detection output to the protective relay device. Of the cutoff command is released, further, an impedance change rate measurement circuit for measuring the rate of change of impedance during power fluctuation detection, and the impedance change rate detection circuit for detecting the rate of change of impedance Impeder that sets the judgment reference value according to the measured value of the impedance change rate measurement circuit A power fluctuation detecting device for a power system, comprising: a change rate setting circuit. 2. The impedance change rate measuring circuit comprises:
The impedance change rate during power fluctuation detection is measured based on the difference between the impedance at the time of power fluctuation detection and the impedance at a certain time before the detection of this power fluctuation. Power fluctuation detector. 3. A power fluctuation detection device of a power system for blocking a cutoff command output from a protection relay device for protecting the power system according to a power fluctuation detection output of the power system, wherein: An impedance change rate detection circuit for detecting a change rate, an accident detection timer operated by the output of the impedance change rate detection circuit, and a logical product of the output of the accident detection timer and the power fluctuation detection output to the protective relay device. And a cancellation circuit for canceling the interruption command inhibition, and further, after the power fluctuation judgment, the difference between the impedance when the impedance locus enters the power fluctuation judgment area and the impedance before a fixed time before entering the power fluctuation judgment area. Of the power system based on the result of comparison between the impedance of the An electric power fluctuation detection device for an electric power system, comprising an accident fluctuation judgment circuit for judging whether an accident or an electric power fluctuation. 4. The impedance change rate measuring circuit calculates the impedance change rate during power fluctuation by measuring the time taken for the impedance locus during power fluctuation to pass through the power fluctuation determination area, and based on the rate of change, the impedance change rate is calculated. The power fluctuation detecting apparatus for a power system according to claim 1, wherein the change rate setting circuit is configured to set a change rate of the impedance for accident determination. 5. The impedance change rate measuring circuit directly calculates the rate of change of impedance when a power fluctuation is detected by a predetermined mathematical expression, and the impedance change rate setting circuit calculates the rate of change of impedance for accident determination based on the change rate. The power fluctuation detection device for a power system according to claim 1, wherein the power fluctuation detection device is set.