JP2611589B2 - Vacuum switch vacuum failure detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum failure detecting device for a vacuum switch. More specifically, the present invention relates to a vacuum failure detection device for a vacuum valve used in a vacuum switch.

[0002]

2. Description of the Related Art A conventional vacuum failure detection device for a vacuum switch and
Is to the load side ground voltage that would after blocking completion is not detected in the normal state, by detecting over descending rated breaking Toki以 by installing the electroscopic insulator on the load side, the vacuum of the vacuum valve of the vacuum switch Apparatus for detecting defects
It disclosed in JP-59-58728.

[0003]

In general, it is rare for all three of the vacuum valves of the vacuum switch to fail in vacuum at the same time. Considering the case where the one-phase or two-phase vacuum valve becomes defective in vacuum, only the phase having a normal vacuum valve is the first phase in which the phase current is initially set to zero. Then, the interruption of the interruption second phase and the interruption third phase is a series interruption. The series shutoff means that after one of the three phases is shut off, the shutoff is performed in a state where the remaining two-phase vacuum valves are connected in series with each other. For this reason, even if those two phases include a phase including a vacuum valve with a vacuum failure, each phase is normally shut off depending on the degree of the vacuum failure, and the total shutoff time does not increase. Therefore, the conventional vacuum failure detection device that detects the load-to-ground voltage after the rated cutoff time has a problem that the vacuum failure cannot be detected in the above case.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide an apparatus for reliably detecting a vacuum failure even when a vacuum failure occurs only in a single-phase vacuum valve. With the goal.

[0005]

SUMMARY OF THE INVENTION According to the present invention, there is provided a vacuum failure detecting apparatus for a vacuum switch, comprising: a current measuring means for measuring a current flowing in each phase of the vacuum switch; The first is to determine which of the phases the current flowing first becomes 0 after the start of shutoff of the vacuum switch.
Determining means, which is performed each time the vacuum switch is shut off,
Storage means for storing the number of determinations for each phase by the determination means, and comparing the number of determinations for each phase stored in the storage means with the total number of determinations, and determining the total number of determinations for each phase. To determine the phase whose ratio to is stochastically lower than the other phase
Determination means.

[0006]

Each time a shut-off is performed in the vacuum switch, the first
The determination means determines which phase of the current measured by the current measuring means has become 0 first, that is, which phase has become the cutoff first phase, and stores it. After a predetermined number of such memories have been stored, the ratio of the number of times that the first determination means determines that the first phase has been cutoff for each phase to the total number of times of determination has been compared with each other, and the first phase has been determined as the cutoff first phase. The phase in which the frequency ratio is stochastically low is determined by the second determination means.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When a vacuum failure occurs in a vacuum valve of one phase of a vacuum switch, the shutoff performance of that phase is reduced. As a result, the shut-off time in that phase is longer than the shut-off time of the other normal phases, so that the vacuum-defective phase cannot be the shut-off first phase. That is, if all phases are normal, all phases will be the shut-off first phase with the same probability, whereas if a vacuum failure occurs in any one phase, the probability of the shut-off first phase will be only for that phase. descend. The present invention makes use of the above-described characteristics of the vacuum valve when a vacuum failure occurs, and performs a first determination as to which phase has become the shutoff first phase each time shutoff is performed, The number of times is stored. Further, after the storage of the memory for a predetermined number of times, a second determination is made as to which of the phases becomes less frequently the cutoff first phase, and it is reliably detected that a vacuum failure has occurred, Is to be specified.

FIG. 2 is a circuit diagram in which the vacuum switch and the vacuum failure detecting device of the vacuum switch of the present invention are connected. The vacuum valves 1a, 1b, 1c of the vacuum switch 1 are connected to buses 2a, 2b, 2c of a, b and c phases, respectively, and the load side of the vacuum switch 1 is connected to a load side circuit 3. . Each CT 4a, 4b, 4c that measures the current flowing through each vacuum valve 1a, 1b, 1c, that is, the current of each phase
Are connected to the vacuum failure detection device 5. Further, a control circuit 6 of the vacuum switch is connected to the vacuum failure detection device 5.

FIG. 1 is a block diagram of a vacuum failure detecting device for a vacuum switch according to the present invention. The analog output from each of the CTs 4a, 4b, 4c is converted into a digital signal by the A / D converters 22a, 22b, 22c and input to the microcomputer 24 via the input interface 23. Furthermore, the control circuit 6 of the vacuum switch
Is also input to the microcomputer 24. Memory 24 in microcomputer 24
In accordance with the program stored in a, the CPU 24b processes these input signals using a built-in clock, and determines the occurrence of a vacuum defect and the phase in which the vacuum defect has occurred. The result of the determination is displayed on a display unit 26 connected via the output interface 25 and configured by, for example, an alarm lamp or the like.

FIGS. 3 to 5 show flowcharts of programs stored in the memory 24a. In step 31, a cutoff start signal is input from the control circuit 6 of the vacuum switch. After the cutoff start signal is input, the process proceeds to step 32, where a timer built in the microcomputer starts counting (T). On the other hand, a cutoff start signal is input to the vacuum switch 1 to excite the trip coil. Thereafter, until any one of the three phases a, b and c is cut off first and the current of that phase becomes 0, that is, until any phase becomes the cut-off first phase, each step 33a, 33b, 33c and 35 are repeated. In other words, a first determination for determining which phase has become the first phase of interruption is performed by these steps.

[0011] In addition, it generally takes about 20 msec from the transmission of the cutoff start signal to the cutoff of any phase. On the other hand, the rated cutoff time is usually set to about 50 msec with more time to complete the cutoff of all phases. Therefore, if none of the phases is interrupted within the rated shutoff time, an alarm indicating an abnormality of the vacuum switch is displayed on the display unit 26 in a vacuum switch abnormality step 35a following the step 35.

In a normal case, the current of one of the phases, for example, the phase a becomes 0 first, the output of the CT 4a becomes 0 in step 33a, and the process proceeds to step 34a, where the count of the memory 1 provided in the memory 24a is incremented by one. Add one. That is, the memory 1 is a storage unit that stores the number of times that the phase a is determined to be the cutoff first phase. The memories 2 and 3 in Steps 34b and 34c are storage means for storing the number of times that the b-phase and the c-phase are determined to be the cutoff first phases, respectively, similarly to the memory 1.

The next step from step 34a, 34b or 34c
Proceeds to 37, storing the total number of the first determination described above as the total number N ₄ of the cutoff in the memory 4 provided in the memory 24a.
It is considered that when the total number of cutoffs becomes a certain number, for example, 30 or more, the number of times that each phase becomes the first phase of the cutoff with respect to the total number of cutoffs can be stochastically determined. So step
In 38, it is determined that the total number of cutoffs has become 30 or more, and the process proceeds to the following steps 39a, 39b and 39c.

When all the vacuum valves of each phase are normal,
The frequency at which any one of the phases a, b and c becomes the cutoff first phase should be stochastically 1/3. On the other hand, if the number of times the phase becomes the shut-off first phase due to a vacuum failure of the valve of a certain phase decreases, or the phase cannot be the shut-off first phase, the phase becomes the shut-off first phase. Frequency is 1/10 (= 0.1)
It is considered that: Therefore when a phase step 39a determines that the ratio of the number N ₁ and the total number N ₄ of blockade is determined to cut off the first phase is 0.1 or less, bad vacuum valve a phase proceeds to step 40a Is displayed on the display
Output to 26. Similarly, in steps 39b and 39c, b
It is determined whether or not the number of times N ₂ and N ₃ determined to be the first phase shutoff of the phase and the c phase is stochastically lower than the total number of determinations N ₄ ,
In steps 40b and 40c, an alarm is output. That is, in steps 40a, 40b, and 40c, the second determination of determining the phase in which the number of times the first phase is shut off is stochastically low is performed. If the number of times the first phase of the cutoff is not probabilistically low in any phase compared to the other phases, it indicates that all phases are normal. After that, step from step 31
Repeat 39c for each interruption.

As described above, the trueness of the vacuum switch of the present invention is as follows.
According to the empty defect detection device , even when it is determined that the entire vacuum switch is normally shut off from the shut-off time, the phase that has become stochastically low as the shut-off first phase is determined. The determination has an effect that a vacuum failure of a specific phase can be reliably detected.

[Brief description of the drawings]

FIG. 1 is a block diagram of a vacuum defect detection device according to the present invention.

FIG. 2 is a connection circuit diagram of a vacuum switch and a vacuum failure detection device.

FIG. 3 is a first half of a flowchart for operating the vacuum defect detection device of the present invention;

FIG. 4 is a latter half of a flowchart for operating the vacuum defect detection device of the present invention.

FIG. 5 is a diagram showing a correlation between FIGS. 3 and 4;

[Explanation of symbols]

 1 vacuum switch 4a CT 4b CT 4c CT 24 microcomputer 24a memory 24b CPU 5 vacuum failure detector

Claims (1)

(57) [Claims] 1. A current measuring means for measuring a current flowing for each phase of a vacuum switch, wherein a current flowing in any phase among the currents measured by the current measuring means is initially set to 0 after the start of shutting off of the vacuum switch. First determining means for determining whether or not each of the conditions has been satisfied; storage means for storing the number of determinations for each phase performed by the first determining means each time the vacuum switch is shut off; A second determination unit that compares the number of determinations for each phase with the total number of determinations and determines a phase in which the ratio of the number of determinations for each phase to the total number of determinations is stochastically lower than the other phases. Vacuum switch vacuum failure detector.