JP3264571B2 - Power fluctuation detection relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power fluctuation detection relay for detecting a fluctuation and a loss of synchronism in a power system when the system has a fluctuation.

[0002]

2. Description of the Related Art Conventionally, a multi-stage overcurrent relay has been used as a relay for taking in a power flow of a power system into a relay and detecting a fluctuation of the current (a value obtained by converting the power flow of the power system for a relay operation). is there.

[0003] The amplitude value of the current taken into the relay is calculated, and a plurality of predetermined current value levels K1 to K are calculated.
n. The operation of the multi-stage overcurrent relay when system oscillation occurs will be described with reference to FIG. FIG. 8A shows a state of a current when system fluctuation occurs. FIG. 8B
Indicates the output of the multi-stage overcurrent relay. When the current value exceeds the current value level K1 to Kn, or below for issuing a predetermined time t ₃ output when the output as shown in FIG. 8 (b) comes out.

[0004]

Next, the operation of the multi-stage overcurrent relay when a simple system fault occurs will be described with reference to FIG. FIG. 9A shows the state of current when a simple system fault occurs. Although a large fault current flows, the fault is immediately eliminated by the response of another relay. FIG.
(B) shows the output of the multi-stage overcurrent relay. Multistage overcurrent relay as a conventional power swing detection - because it is in the above-described functional configuration, when the current value exceeds the current value level K1 to Kn, or a predetermined time (t ₃₎ when below so produce output As shown in FIG. 9B, an output occurs for a certain time when an accident occurs and when the accident is eliminated.

Therefore, in the conventional relay that takes in only the power flow of the power system, that is, in the above-mentioned multi-stage overcurrent relay, since the level of the power flow is simply determined, it operates both when the system is shaken and when a simple system fault occurs. Therefore, it is not possible to determine whether the system is upset or a simple system accident.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a power fluctuation detection relay which does not operate in a simple system accident and operates reliably when the system is vibrated. I do.

[0007]

In the power fluctuation detecting relay 10 according to the present invention, as shown in FIG. 1, a power flow change detecting unit 12 for detecting a power flow change of a system, and a power flow change detecting unit 1 for detecting the power flow change.
2 is provided with an output continuation determining unit 13 for detecting that the output of the second unit has continued for a predetermined time. The tidal current used in the following description means a current.

[0008] Here, the tidal change detecting unit 12 detects the current time (t
₀ ) and a predetermined first predetermined time (t ₁ )
Is compared with the previous tidal current value, and if the difference is equal to or greater than the set value (K), it is output. In the output continuation determining unit 13, the output of the tidal current change detecting unit 12 is set to a predetermined second predetermined time (t ₂ ).
When the above is continued, it is determined that the system is unstable. At this time, the time t
₁ and t ₂ are set to values that are sufficiently longer than the normal power system accident duration and shorter than half of the system oscillation period.

[0009]

First, the state of the system will be described. Normally,
The power flow value (current value) of the power system is almost constant. When an accident occurs, the current changes significantly due to the accident current during the accident, and when the accident is eliminated, the power flow value of the power system becomes almost constant again. However, when the power system is oscillating or out of synchronization, the magnitude of the power flow value changes at a certain oscillating cycle.

The operation of the power fluctuation detection relay according to the present invention in the case of a simple system fault will be described with reference to FIG. In tide change detector 12, sufficiently longer than the current of the current value of the first predetermined time t ₁ hour (in the accident time, for example 1
00 to 150 msec) Compare with the previous current value. Therefore, during the occurrence of a system fault (for example, 70 msec), the current value before the occurrence of the fault and the current value during the fault (present) are compared, and the difference is large, so that an output of “large change in power flow” is output. Immediately after the removal of the accident, the current value (= immediately after the removal of the accident) is compared with the current value before the accident. In the case of a simple system fault, there is almost no difference between the current values before the occurrence of the fault and after the fault is removed, and therefore, the output of the power flow change detecting unit 12 does not appear immediately after the fault is removed. Therefore, the output of the power flow change detection unit 12 continues for the time during the accident.

[0011] The output continuation judging section 13 calculates a _second predetermined time t ₂
(Time sufficiently longer than the time during the accident, for example, 100 to 500 msec
) It detects that there has been an output of the tidal current change detection unit 12 for a longer time, and outputs an output. As described above, the power flow change detection unit 12 outputs only during the time during the accident, so that no output is output from the output continuation determination unit 13.

Next, the operation of the power fluctuation detection relay according to the present invention when the fluctuation and step-out occurs in the system will be described. Since the current value is constantly changing in accordance with a certain fluctuation period (for example, about 1200 msec) determined by a constant of a certain power system, the output of the power flow change detection unit 12 continues to operate for about half the fluctuation period. The output continuation determining unit 13 outputs the output when the output of the power flow change detecting unit 12 is continued for a time t ₂ (a time shorter than half of the oscillation period). Put out.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention based on the above-described means and operation will be described below in detail with reference to the drawings.
The tidal current used in the following description means a current. One embodiment according to the present invention is shown in FIG. The power fluctuation detection relay 10 includes an input unit 11, a power flow change detection unit 12, and an output continuation determination unit 13 which take in a power flow value of the power system into a relay device, and perform a filtering process and a digitizing process.

The power flow change detection unit 12 takes in the power flow of the power system, calculates its amplitude value (referred to as current amplitude value), saves this amplitude value in the storage unit, and performs the following. Assuming that the current amplitude value is I (t ₀ ) and the current amplitude value t ₁ hours ago is I (t ₀ −t ₁ ), I (t ₀ −t ₁ )
The value of (t ₀ −t ₁ ) is called out, the operation represented by the expression (1) is performed, and when the condition is satisfied, “large change in power flow” is output. Here, t ₁ is a time (for example, 150 msec) sufficiently longer than the time during accident (for example, 70 msec).

[0015]

| I (t ₀ ) −I (t ₀ −t ₁ ) |> K (1) K: Set value In the output continuation judging unit 13, the output of “large flow change” of the flow change detection unit 12 is output. but put the output in the case that has been continued t ₂ hours.
Here, t ₂ is a time sufficiently longer than the time during the accident (for example, 20
0 msec), and is set (by simulation or the like in advance) in accordance with the line constant of the power system to which this relay is applied, the power supply to be connected, and the state of the load.

The details of the power flow change detecting unit 12 will be described with reference to the configuration diagram of FIG. The storage unit 21 stores the power flow value for a predetermined period output from the input unit 11. First predetermined time t ₁ before the power flow value I difference calculation unit 22 to be stored in the storage unit (t ₀ -t
₁ ), and calculates the absolute value of the difference between the current power flow value I (t ₀ ) output from the input unit 11 and the stored power flow value I (t ₀ −t ₁ ). The comparing unit 23 compares the absolute value of the difference calculated by the difference calculating unit 22 with the set value K, and when the absolute value of the difference is larger than the set value K, generates a detection output. Output to

Next, the operation of the relay according to the present embodiment when a system oscillation occurs will be described with reference to FIG. FIG. 3 (a)
Represents a change in power flow (current) when a system fluctuation occurs. FIG. 3B shows an output result of the power flow change detection unit 12. When the power system fluctuation occurs at time t ₀ and the power flow change from the time t ₁ before exceeds K, the power flow change detection unit 12 outputs “large power flow change”. The output is continued while the fluctuation of the current is greater than or equal to K, but is different for t ₁ time around the maximum (or minimum) of the current fluctuation as shown in FIG. The output stops during the time period in which the two currents are compared. Therefore, when the output of the power flow change detection unit 12 is the longest, the output lasts for about half the oscillation period.

FIG. 3C shows the output of the output continuation determining unit 13. Since the output of the power flow change detection unit 12 to continue for about half of the upset periods, simulators and t ₂ from the line constants, etc. - so that the Deployment to preset half value less than the upset periods which are (for example, 200 msec) strains Output comes out when shaking or stepping out.

FIG. 4 shows the operation of the relay of the present embodiment when a relatively short fault occurs among simple (general) system faults. 4A shows the state of the change in the current value, FIG. 4B shows the output of the power flow change detecting unit 12, and FIG. 4C shows the output of the output continuation determining unit 13. Twice when the accident has elapsed when the accident after t ₁ hour generated, power flow change detection unit 12 issues an output for the same time as the accident duration. However, since the accident time sufficiently shorter than t _2, the output continuation determining section 13 does not issue an output.

FIG. 5 shows the operation of the relay when a relatively long fault among simple system faults occurs. FIG.
5A shows the state of the change in the current value, FIG. 5B shows the output of the power flow change detecting unit 12, and FIG. 5C shows the output of the output continuation determining unit 13. When an accident occurs and after a lapse of t1 time from the elimination of the accident, the power flow change detecting unit 12 outputs an output for the time t1. However, by setting t2 (200 msec) longer than t1 (150 msec), the output continuation determining unit 13 does not output.

That is, it is possible to provide a power fluctuation detection relay that reliably operates during system fluctuations and does not operate during a simple system fault as described above. Next, another embodiment will be described.

In the above-described embodiment, t ₁ <t _2. However, in this embodiment, t ₁ > t ₂ (for example, t ₁ = t ₂ ).
150 msec, t ₂ = 100 msec) will be described. Other conditions are the same as in the above-described embodiment. At the time of current fluctuation, fluctuation can be detected in the same manner as in the above-described embodiment. The operation of the relay when a simple system fault occurs will be described with reference to FIGS.

FIG. 6 shows how the relay operates when the duration of the accident is relatively short. As in the previous embodiment, the relay does not operate. FIG. 7 shows the operation of the relay when an accident having a relatively long accident duration occurs. FIG.
7A shows the state of the change in the current value, FIG. 7B shows the output of the power flow change detecting unit 12, and FIG. 7C shows the output of the output continuation determining unit 13. When an accident occurs and after a lapse of t ₁ hours from the elimination of the accident, the power flow change detection unit 12 outputs an output for the time t ₁ . t
₂ shorter than t _1, the output continuation determination unit 13 issues an output. If the duration of the accident is long, there is a high possibility that the system will oscillate. Therefore, if t ₁ > t ₂ is set, the system sway can be detected earlier.

[0024]

As described above, according to the present invention,
By using only the current of the system, it is possible to reliably determine a system fault and a system fluctuation / step-out, and to provide a power fluctuation detection relay for improving operation reliability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a power fluctuation detection relay according to the present invention.

FIG. 2 is a detailed configuration diagram of a power flow change detection unit according to the present invention.

FIG. 3 is an operation signal response diagram at the time of current fluctuation of a relay according to the present invention.

FIG. 4 is an operation signal response diagram at the time of a simple system fault of the relay according to the present invention.

FIG. 5 is an operation signal response diagram at the time of a simple system fault of the relay according to the present invention.

FIG. 6 is an operation signal response diagram at the time of a simple system fault of a relay according to another embodiment.

FIG. 7 is an operation signal response diagram at the time of a simple system fault of a relay according to another embodiment.

FIG. 8 is an operation signal response diagram at the time of current fluctuation of a conventional relay.

FIG. 9 is an operation signal response diagram of a conventional relay when a simple system fault occurs.

[Explanation of symbols]

10 power fluctuation detection relay, 11 input unit, 12 power flow change detection unit, 13 output continuation determination unit, 21 storage unit, 22 difference calculation unit, 23 comparison unit, t _1, first predetermined Time (power flow change detection time), t ₂ ... Second predetermined time (output continuation determination time), K... Set value (power flow change detection value).

Claims (5)

(57) [Claims] And 1. A input unit for taking a current value from the power system, the current value of the current value output from the input unit in advance
A power flow change detection unit that compares a value before a first predetermined time set to a time longer than the set fault current duration at the time of the fault in the power system, and generates a detection output when the difference is larger than a set value. If, setting the output of the trend change detection section in advance
An output continuation determination unit that generates a relay output when the power system continues for a second predetermined time set to a time longer than the specified fault current continuation time at the time of the power system fault. relay. 2. A method according to claim 1, wherein the trend change detection unit includes a storage unit for storing a current value output from the input section, the current value of the current value output from the input unit storage unit A difference calculation unit that calculates a difference from the value before the first predetermined time stored in the storage unit, and a comparison unit that generates a detection output when the difference calculated by the difference calculation unit is larger than a set value. Power fluctuation detection relay. 3. The power fluctuation detection relay according to claim 1, wherein the second predetermined time is set to a time shorter than half of a power fluctuation cycle determined by a line constant or the like of the power system. 4. The power fluctuation detecting relay according to claim 1, wherein the second predetermined time is set to a time longer than the first predetermined time. 5. The power fluctuation detecting relay according to claim 1, wherein the first predetermined time is set to a time longer than the second predetermined time.