JPH03183971A - Zero-phase voltage detecting device - Google Patents

Abstract

PURPOSE:To obtain the small-sized, high-accuracy detecting device which is usable even for an overhead line, etc., by detecting voltages by the phases of an AC cable run and adding them, and making corrections by a circuit which has two memories. CONSTITUTION:A measuring instrument 100 detects the voltages by the phases of three-phase power distribution lines 9a - 9c. Those outputs are outputted by an adding circuit 17 as a zero-phase voltage component. This output is zero in a stationary state and not zero in case of a ground-fault accident, which can be detected. Then a data group of the latest momentary values by specific electric angles in >=1 cycle of commercial frequency and a past data group of reference stored values corresponding to them are stored in the 1st and 2nd memories 21 and 22 of a correction arithmetic circuit 18. A microprocessor 20 substracts the corresponding reference stored values from the momentary values by the electric angles in the memory 1 and performs development into a Fourier series to make corrections. Thus, an error component is removed to securely detect the zero-phase voltage in the ground-fault accident.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a zero-sequence voltage detection device for detecting zero-sequence voltage that occurs when a ground fault occurs in a power distribution line.

[Conventional technology]

FIG. 5 is a configuration diagram showing a conventional zero-phase voltage detection device disclosed in, for example, Japanese Patent Laid-Open No. 58-204721.

In the figure, a conventional zero-sequence voltage detection device has a high-voltage bushing (11), a main capacitor (31) connected to a high-voltage terminal (21) for connection to a distribution line (31, and a metal shield box (4)).
, One end is connected to the main capacitor (3), and the other end is the lead wire (51), which connects all three phases in the shield box (41), the ground terminal (61, the lead wire (three-phase - A voltage dividing circuit (5) connected between the bracket and the ground terminal (6)
), a capacitor (7), a divided voltage extraction terminal (8) for extracting the zero-sequence voltage, etc.

The voltage of the distribution line applied to the high voltage terminal (2) is divided by both capacitors (31[71].The voltage dividing part is connected to the lead wire (5) for the three phases, so the divided voltage A zero-phase voltage component obtained by combining three phases is obtained at the extraction terminal (8).

Under normal conditions, when no ground fault has occurred on the distribution line, the combined value of the three-phase voltages on the distribution line is zero. However, when a ground fault occurs in a power distribution line, even if the three-phase voltages are combined, they do not reach zero, and a zero-phase voltage occurs. Each time a ground fault detection relay (not shown) such as a ground fault direction relay is connected to this partial voltage extraction terminal (8), the distribution line is protected from a ground fault accident.

[Problem to be solved by the invention]

In general, in order to quickly and accurately discover fault points, limit power outage areas as much as possible, and shorten recovery time, many zero-sequence voltage detection devices should be installed not only in substations but also in the middle of distribution lines. is desirable.

However, in the conventional zero-phase voltage detection device, three-phase high (6) pressure bushings are installed all at once in a metal seal I/box.
n! Since it is an i-type construction, the device becomes large in size, and this tendency becomes particularly noticeable as the distribution voltage increases, which poses a problem in that it is unsuitable for use on overhead electric wires and the like.

Additionally, if a voltage measurement means is provided for each phase and the detection outputs are combined, the characteristics of the voltage measurement means will differ for each phase, which will cause an error and generate an apparent zero-sequence voltage, causing the protection circuit to fail. This had the problem of malfunction.

This invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a small and highly accurate zero-sequence voltage detection device that can be used even on overhead electric wires.

[Means and operations for solving the problem] The zero-sequence voltage detection device according to the invention of claim 1 is provided for each phase of an AC line, and includes a measuring means for detecting the voltage of each phase, and a measuring means for detecting the voltage of each phase. Adding means for adding signals and outputting them as zero-phase voltage components; of the output from this adding means, at least the latest for commercial use <7) The instantaneous value at every predetermined electrical angle of the output for a period of one wave number period or more a first storage means for storing data as a group;
The same number of past addition means corresponding to each electrical angle of the instantaneous value data group detected before the instantaneous value data group stored in the first storage means and stored in the first storage means a second storage means for storing a group of instantaneous value data of the output from the first reference storage value as a first reference storage value; a first calculation means for subtracting the first reference storage value of each corresponding electrical angle stored in the storage means and outputting the result as a first subtraction value for each electrical angle; a second calculation means that expands into a Fourier series and calculates only the commercial frequency component value; a third calculation means that calculates an effective value from the commercial frequency component value calculated by the second calculation means; Determine whether the effective value is above or below a predetermined set value, and if the effective value is below the set value, erase the instantaneous value data group stored in the second storage means (8). to update the instantaneous value data group stored in the first storage means, and if the effective value is equal to or higher than the set value, the instantaneous value data group stored in the second storage means is updated for at least one cycle thereafter. The fourth calculation means does not update the value data group, and the output means outputs the data from the second calculation means to the burden means.

Assuming that there is a difference in characteristics between the measuring means for each phase, the output of the adding means will include an apparent zero-sequence voltage component.

Then, the first storage means stores the output from the addition means at a predetermined electrical angle, for example, 30 degrees, for example, at 1 of the commercial frequency.
Data sampled over a period is stored.

The second storage means stores data sampled one cycle before in a similar manner.

The first calculating means subtracts the data stored in the re-storing means, but since the apparent zero-sequence voltage component due to the characteristic difference of the measuring means does not change within this period unit time difference, this error The minute is subtracted from the output of the (9) first calculation means.

Therefore, if zero-sequence voltage is not occurring in the actual AC circuit, the first subtraction value will be approximately zero, and the commercial frequency component value determined by the second calculation means and its effective value determined by the third calculation means becomes almost zero.

In this case, the fourth calculation means sequentially updates the data in the storage means and continues the same operation.

Here, if a ground fault or the like occurs in the AC line at a certain period and a zero-sequence voltage actually occurs, the subtraction value from the data in the previous period will rise significantly, and the commercial frequency component will be output by the output means. It is output to the load means and used for protection operations, etc. Moreover, each time the effective value of the component exceeds the set value of the fourth calculation means, the data in the second storage means is not updated at a predetermined period. Therefore, during this period,
The first to third calculation means continuously output signals corresponding to the actually generated zero-sequence voltage components.

Furthermore, the zero-sequence voltage detection device according to the invention of claim 2 includes a third storage (10) means for storing the effective value calculated by the third calculation means in the device according to the invention of claim 1. a fourth storage means for storing a past effective value calculated before the effective value stored in the third storage means as a second reference storage value, the latest stored in the third storage means; a fifth calculation means for subtracting the second reference storage value stored in the fourth storage means from the effective value of and outputting the result as a second subtracted value; In place of the means, it is determined whether the second subtraction value is greater than or equal to a predetermined set value, and when the second subtraction value is less than or equal to the set value, the second storage means is stored. The stored instantaneous value data group is deleted and updated to the instantaneous value data group stored in the first storage means, and the second reference storage value stored in the fourth storage means is updated. The instantaneous value is updated to the effective value stored in the third storage means, and the instantaneous value is stored in the second storage means for at least one cycle thereafter when the second subtracted value is equal to or greater than the set value. A sixth calculation means that does not update the data group is provided.

In this case, the third and fourth storage means store the temporally successive values of the effective value from the (11) third calculation means, and the fifth calculation means subtracts both of the effective values. Output as the second subtraction value.

Then, the detection of the zero-sequence voltage is determined based on the magnitude of the second subtraction value, and if this value is less than the set value, the data in the second storage means is updated to new data, and the data in the fourth storage means is updated. The effective value is also updated to a new one.

Furthermore, the zero-sequence voltage detection device according to the invention of claim 3 uses the measuring means of the devices of the above-mentioned inventions as a voltage dividing capacitor provided for each phase of the AC line, and a voltage dividing capacitor and a ground static voltage of each phase. It consists of a photovoltage sensor that outputs an optical signal corresponding to the voltage divided by the capacitance, and the addition means adds the optical signals from the photovoltage sensor, converts it into an electrical signal, and outputs it as a zero-phase voltage component. It was designed to do so.

In this case, the voltage of each phase is detected in the form of an optical signal from an optical voltage sensor by capacitor voltage division using ground capacitance.

Optical fibers and the like transmit optical signals and at the same time (12) provide electrical insulation between the electrical circuit and the ground. Furthermore, since the addition of each phase is performed at the optical signal stage, only one photoelectric converter is required, and therefore there is no zero-phase error due to differences in characteristics between photoelectric converters.

〔Example〕

FIG. 1 is a block diagram showing the configuration of a zero-sequence voltage detection device according to an embodiment of the present invention.

In Figure 1, three-phase distribution lines (9a) (9b) (9
c) are respectively divided voltage capacitors (7a) and (7b).
(7c) is connected, and each voltage dividing capacitor (7a) (7
b) Optical voltage sensors (lla) (llb) (Inc) using the Pockels effect are connected between both terminals of (7c), respectively. Partial voltage capacitor (7a) (7b
) (7c) and optical voltage sensor (lla) (llb
) (llc) is the container (12a) (+2b) (12c
) is housed in.

Note that the capacitor (10a) (IOb) indicated by the dotted line
(10c) shows the floating capacitance in the air to the ground. Each optical voltage sensor (I la) (eye b) (Ilc)
Optical fibers (15a) (15b) <1
5c), the light emitting elements (13a) (13b) (1
3c) and light receiving elements (14a) (14b) (14
c) is connected. Therefore, electrical insulation between the power distribution line (9a), etc. and the ground where this detection device (13) is installed is provided by optical fiber (
15a) etc. Then, voltage dividing capacitors (7a) (7b) (7c), optical voltage sensor (lla
> (Ilb) (Ilc), light emitting element (+3a) (+
3b) (13c), light receiving element (14a) (14b
) (14c) and optical fibers (15a) (15b
) (15C) and the like constitute the measuring means (+001).

The output signals of each light receiving element (14a) (14b) (14c) are sent to a signal processing circuit (16a) (+6b), respectively.
(16c), and further signal processing circuit (16a)
(16b) The output signal of (+6c) is the adder circuit (17
) is entered. The output signal of the adder circuit (17) is input to a correction calculation circuit (18).

The voltage of the three-phase distribution line (9a) etc. is connected to the voltage dividing capacitor (7a
) etc. and ground capacitance (10a) etc.,
It is applied to a photovoltage sensor (lla), etc. On the other hand, the light incident on the optical voltage sensor (11a) etc. from the light emitting element (+3a) etc. via the optical fiber (15a) etc. is light intensity modulated in proportion to the above-mentioned partial voltage due to the Pockels effect of the optical voltage sensor. After that, it is sent to a light receiving element (14a) etc. via an optical fiber (+5a) etc. The signal photoelectrically converted by the light receiving element (14a) etc. is converted into a signal proportional to the voltage applied to the photovoltage sensor (lla) etc. by the signal processing circuit (14) (+6a) etc., and then sent to the adding circuit (17). These signals are combined and added.

Here, assuming that there is no difference in characteristics between the equipment of each phase,
When the three-phase distribution line is in a normal steady state, the sum of the voltages of each phase becomes zero, and the output signal of the adding circuit (17) also becomes zero. In addition, if a ground fault occurs in the three-phase distribution line,
Even if the voltages of each phase are added, the voltage does not become zero and a zero-phase voltage is generated, so the output signal of the adder circuit (17) has a value proportional to the zero-phase voltage, and this output signal can prevent ground faults in three-phase distribution lines. For example, each time a protection relay is activated, more appropriate protection of the power distribution line can be achieved.

However, in general, the optical voltage sensor (lla) and the like and the signal processing circuit (16a) have temperature characteristics. Furthermore, the ground capacitance (10a) and the like change due to changes in atmospheric humidity, and there are also differences in individual characteristics. Therefore, the ratio between each voltage of the three-phase distribution line (9a) and each output signal of the signal processing circuit (16a) etc. varies between each phase due to changes in ambient temperature, etc. Therefore, the addition port (15) The output signal of (17) does not become zero even when zero-sequence voltage is not actually generated in the three-phase distribution line, causing the protective relay to malfunction.

The correction calculation circuit (18) is for preventing the above-mentioned malfunction, and has a microprocessor (18) as a hardware configuration.
201, memory (21) consisting of RAM memory, (
22) It has... Memory (21), (2
It goes without saying that 2)... each have a storage area greater than the number of samples of data to be stored.

Generally, the error component of the zero-sequence voltage changes relatively slowly due to differences in the temperature characteristics of each signal processing circuit or the humidity characteristics of stray capacitance, and the error component due to noise is instantaneous. be. Furthermore, although the zero-sequence voltage component due to a ground fault occurs instantaneously, it lasts for a relatively long time compared to the case due to noise.

The correction arithmetic circuit (18) was invented focusing on the above points, and removes the error component in the above-mentioned front stage portion, and reliably detects the zero-sequence voltage due to a ground fault. The operation will be explained below using the flowchart shown in FIG.

(16) In step S1, an initial value is stored in, for example, a memory (22) that acts as a second storage means.

Each instantaneous value data group stored in the memory (22) is
jHj represents the order of data sampled every predetermined electrical angle, 30 degrees here. ), then B(1
) to B (+21) are stored. Normally, 0 is input to all these addresses as initial values. Here, the sampling period for one data group is set to the commercial frequency (here , 60Hz) 1
It is set as the period.

Next, in steps S2, S3, and S5, initial values are set to =cl, 1=60, and j=1.

In step S6, data for the latest one cycle of the AC output, which is the output signal from the adder circuit <17), is converted into a digital signal as an instantaneous value at every predetermined electrical angle, here 30 degrees, and is stored in the first storage means; For example, memory (21)
is stored as A (j>).

Next, in step S7, the microprocessor (20) serving as the first calculation means processes the jth <17> data A(j) stored in the first storage means (memory (21)). to the second storage means (memory (22
) Performs an operation to subtract the same j-th data B(j) stored in ). That is, assuming that the result is the first subtraction value C(j), C(j)-A (j)-B 1 is executed.

Note that steps S6 and S7 are repeated until 12 pieces of data for one cycle are obtained (step S8゜59). Generally, differences in humidity characteristics of ground (floating) capacitance of measurement means, optical voltage sensors, signal processing circuits, etc. Since the difference in temperature characteristics hardly changes over a short period of time (for example, 1 second), it is considered that all sampling data uniformly includes an error due to this difference in temperature/humidity characteristics.Therefore, the difference obtained by the above subtraction process is Error components due to differences in temperature/humidity characteristics of the measuring means are removed from each subtracted value C(j).In other words, the actual zero-sequence voltage component occurring in the distribution line can be detected with high accuracy. This means that it can be done.

However, immediately after initialization in step Sl, (18
) In the calculation step, that is, the calculation step of k=1 (step S4), since all the data B (j) are O, it becomes C (j) - A (j), which is not substantially subtracted, but After the next calculation step in which data B (j) is updated in step SI8, which will be described later, the effect of error component removal described above is obtained every time.

The microprocessor (20) then acts as a second computing means. That is, the subtracted value C(j) is expanded into a Fourier series, and the value of the commercial frequency component is calculated (step StO). In general, the output from the adder circuit (17) includes high frequency components and low frequency components due to noise etc. in addition to commercial frequency components, and these components are superimposed. Therefore, if only the commercial frequency component is extracted each time it is expanded into a Fourier series and frequency analysis is performed, the calculated commercial frequency component will not include any error component.

Next, the microprocessor (20) acts as an output means and outputs the calculated commercial frequency component value for the secondary burden (23) (step 511). Since the magnitude and phase of the zero-sequence voltage can be obtained from this (19) output value, it becomes possible to grasp situations such as ground faults by combining with other current information, etc.

In step SI2, the microprocessor (20)
acts as a third calculating means, and calculates the effective value E from the commercial frequency component value calculated in step SIO.

Further, in step S13, it is determined whether or not =1. In other words, if the counter value k is 1 (1<-1
), immediately after the zero-sequence voltage detection device starts operating,
As for the reference storage values that are yet to be stored in the second storage means, O is stored (nothing has been input). Therefore, the process proceeds to step S18 in order to transfer all the data stored in the first storage means that was sampled first to the second storage means before performing sampling in the next period.

Once step SI8 is passed, the value of counter 1 is incremented (step S4), so the determination in step S13 becomes NO and the process proceeds to step SI4, but here (90), the value of counter 1 is initialized to 1-60. So (step S
3) Proceed directly to step S16, and determine whether the effective value E is greater than or equal to a predetermined set value S (fourth calculation means). 50-90% of the operating level is suitable.

Here, if the effective value E is smaller than the predetermined set value S,
Since this is a normal situation with no ground faults occurring,
A second storage means (memory) is used to prepare for the next calculation process.
22> ), and the instantaneous data group and effective value stored in the first storage means (memory (2+)) are used as new storage values in the second storage means. The contents are updated (step 518).

If the effective value E is larger than the predetermined set value S, a ground fault or the like has occurred, and the three-phase distribution line must be disconnected from the power source. In general, operating the secondary burden (23) to disconnect a three-phase distribution line from the power source requires approximately 1
It is sufficient to output a current corresponding to the zero-sequence voltage per second.

However, once the zero-sequence voltage due to the ground fault rate (21〉 Since all the sampled instantaneous value data includes the zero-sequence voltage component due to the ground fault, the zero-sequence voltage component due to the ground fault is canceled out in the bar calculation process executed in step S7. For example, in order to continue outputting the commercial frequency component value corresponding to the zero-sequence voltage for one second, the past data stored in the second storage means, that is, the data that does not include the component due to the ground fault, is left as is, and the data stored in the first storage means is Only the data including the component due to the latest ground fault accident to be stored in the storage means is updated.

Then, the above calculation process is repeated for 1 second after detecting the zero-sequence voltage component due to the ground fault, that is, for 60 cycles in the case of AC 60 Hz. Steps S14 and S15 are for performing the above processing and form part of the action of the fourth calculation means.

FIG. 3 is a flowchart illustrating the operation of another embodiment. What differs from the contents of FIG. 2 (22) is the accident determination method based on the effective value E of the commercial frequency component obtained from the data C(j), and this point will be mainly explained below.

Immediately after the start, the determination in step SI3 becomes YES and the data B (j) is updated in step S18, which is the same as in the case of FIG. 2.

Next, when k=2 and the determination in step S13 becomes NO, the microprocessor (20) acts as the fifth calculation means. That is, from the effective value E of the commercial frequency component value obtained in step S12 and stored in another storage area of the memory (21) as the third storage means, for example, the fourth storage means is stored in the memory (22). A second reference storage value H stored in another storage area is subtracted to calculate a second subtraction value F.

(Step 519).

Further, in step S20, the microprocessor (20>) acts as a sixth calculation means and determines whether the second subtraction value F is greater than or equal to a predetermined set value S.

The appropriate setting value S is 50-90% of the operating level of the ground fault detection relay of the secondary burden (23).

(23) Here, if the second subtraction value F is smaller than the predetermined set value S, it is a normal state in which no ground fault has occurred, so the second subtraction value F and All data stored in the fourth storage means (memory (22)) is erased, and all data stored in the first and third storage means (memory (22)) is deleted.
)) The instantaneous data group and the effective value stored in the data are updated as new stored values in the second and fourth storage means (step S18.822).

If the second subtraction value F is larger than the predetermined set value S, a ground fault or the like has occurred, and the three-phase distribution line must be disconnected from the power source. In this case, in anticipation of the continuation of the accident, updating of data for 60 cycles, for example, is not performed in steps S14 and Si2, as in the case of FIG. 2. However, here, the first reference storage value B(j> stored in the second storage means and the second reference storage value H stored in the fourth storage means are the targets).

In this embodiment, the zero-sequence voltage is detected by the difference F between the effective values of the commercial frequency components c')4) Therefore, it is expected that the influence of residual errors in the measurement system etc. will be further reduced.

FIG. 4 is a block diagram showing the configuration of a zero-sequence voltage detection device according to still another embodiment. The difference from the embodiment shown in FIG. 1 is that an optical adder (24) is newly provided. In other words, the optical voltage sensor (lla>(llb)) changes in response to the voltage of the three-phase distribution lines (9a) (9b) (9c).
Each Wako signal from (llc) is transmitted through an optical fiber (15a
> (15b) Optical adder (24) via (15c)
Here, the signals are combined and added in the form of optical signals, then photoelectrically converted by the light receiving element (14), and then processed through the signal processing circuit (16) and the like.

Here, as the optical adder (24), a so-called mixer rod type star coupler in which a mixing rod is inserted between a plurality of optical fibers, a so-called twist fusion type star coupler in which a plurality of optical fiber cores are twisted and fused, etc. are used. An appropriate one is selected from those available.

In the case of this example, since the configuration is such that each phase is added in the optical signal state (25) without photoelectrically converting the optical signal, which is the original information of each phase voltage, the light receiving element and signal processing circuit are It is possible to remove zero-sequence voltage component errors due to characteristic differences between devices that are unavoidable when installed for each phase, and the error factors are reduced accordingly, improving the accuracy of the zero-sequence voltage detection device. do.

Of course, since it uses a capacitor voltage division method that utilizes ground capacitance and uses an optical voltage sensor, it is easy to install on distribution lines, and electrical insulation from ground is easily ensured using optical fiber. Furthermore, since the optical signal is transmitted, it is resistant to electromagnetic noise and various surges, which can be cited as a powerful effect, as in the case of the embodiment shown in FIG.

In each of the above embodiments, the predetermined electrical angle for sampling data was set to 30 degrees, but if the processing speed of a microprocessor or the like can be increased, it may be further subdivided into 30 degrees or less. On the other hand, if high precision is not required, the angle may be made rougher than 30 degrees. Further, the number of data stored in the memories (21) and (22) (26) and the number of instantaneous values for determining the effective value are each 12 for one period, but may be for two or more periods. As this value is increased, the calculation accuracy improves, but the processing speed decreases.

Furthermore, after the zero-sequence voltage is detected due to a ground fault, the time to continue outputting the average value data corresponding to the zero-sequence voltage was set to 1 second (60 cycles), but the operation of the ground fault detection relay of secondary burden (23) If the time is short, the above period may be shortened.Furthermore, the correction calculation circuit (18), the signal processing circuit (16a), etc., and the addition circuit (17) may all be configured by a microprocessor.

Further, the correction calculation circuit (18) in each of the above embodiments is
The invention is not limited to the case where each zero-sequence voltage is measured via an optical signal, but can be widely applied to cases where other types of voltage measuring means are employed.

〔Effect of the invention〕

Since the present invention is configured as described above, it is possible to eliminate the detection error of the zero-sequence voltage component based on the difference in the characteristics of each phase of the measuring means and the influence of high-frequency and low-frequency noise, thereby reducing the zero-sequence voltage caused by a ground fault, etc. Component abnormalities are accurately detected (27) and appropriate protective actions are ensured.

Further, in the invention of claim 2, since the zero-sequence voltage is detected by the time difference of the effective value of the commercial frequency component, the influence of residual error of the measuring means can be suppressed to a lower level.

Furthermore, in the invention of claim 3, since the voltage of each phase is detected in the form of an optical signal from an optical voltage sensor by capacitor partial pressure using ground capacitance, the measuring means is small and easy to install, and electromagnetic noise is eliminated. The effects of this are also removed. and,
Since the adding means adds each phase at the optical signal stage and then performs photoelectric conversion, the error due to the difference in characteristics of each phase in at least the photoelectric conversion part may exist, but the error in the phase voltage component is reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a zero-phase voltage detection device according to one embodiment of the present invention, FIG. 2 is a flowchart showing the operation of its correction calculation circuit, and FIG. 3 is a block diagram showing the operation of the correction calculation circuit according to another embodiment. Flowchart 1 showing the operation, FIG. 4 is a block diagram showing the configuration of a zero-sequence voltage detecting device (28) according to another embodiment, and FIG. 5 is a diagram showing a conventional zero-sequence voltage detecting device. In the figure, (7a) etc. are voltage dividing capacitors, (9a) etc. are three-phase distribution lines as AC circuits, (10a) etc. are ground capacitances, (lla) etc. are optical voltage sensors, (+38) etc. are light emitting elements, (14a) etc. are light receiving elements, (15a) etc. are optical fibers, (17) is an addition circuit as addition means, (1
8) is a correction calculation circuit, (20) is a microprocessor as each calculation means, (21) (22> is a memory as each storage means, (23) is a secondary burden as a burden means, and (24) is an addition An optical adder is used as a means, and (100) is a measuring means.The same reference numerals in each figure indicate the same or corresponding parts.

Claims (3)

[Claims] (1) Measuring means provided for each phase of the AC line to detect the voltage of each phase; an adding means for adding the signals from the measuring means and outputting the result as a zero-sequence voltage component; , a first storage means for storing instantaneous values at each predetermined electrical angle of the latest output for a period of at least one cycle of the commercial frequency or more as a data group; from the instantaneous value data group stored in the first storage means; was also previously detected,
A second storage means stores instantaneous value data groups of outputs from the same number of past adding means corresponding to each electrical angle of the instantaneous value data groups stored in the first storage means as a first reference storage value. a storage means, from each of the instantaneous value data groups for each electrical angle stored in the first storage means, first reference stored values of the respective corresponding electrical angles stored in the second storage means; a first calculation means for subtracting and outputting it as a first subtraction value for each electrical angle; a second calculation means for expanding the first subtraction value into a Fourier series and calculating only the commercial frequency component value; a third calculating means for calculating an effective value from the commercial frequency component value calculated by the second calculating means; determining whether the effective value is above or below a predetermined set value; If it is below the set value, the instantaneous value data group stored in the second storage means is deleted and updated to the instantaneous value data group stored in the first storage means, and the effective value is a fourth calculation means that does not update the instantaneous value data group stored in the second storage means for at least one cycle if the value is equal to or greater than the set value; and data from the second calculation means. A zero-sequence voltage detection device equipped with an output means for outputting the voltage to a burden means. (2) Measuring means provided for each phase of the AC circuit to detect the voltage of each phase; an adding means for adding the signals from the measuring means and outputting the result as a zero-sequence voltage component; , a first storage means for storing instantaneous values at each predetermined electrical angle of the latest output for a period of at least one cycle of the commercial frequency or more as a data group; from the instantaneous value data group stored in the first storage means; was also previously detected,
A second storage means stores instantaneous value data groups of outputs from the same number of past adding means corresponding to each electrical angle of the instantaneous value data groups stored in the first storage means as a first reference storage value. a storage means, from each of the instantaneous value data groups for each electrical angle stored in the first storage means, first reference stored values of the respective corresponding electrical angles stored in the second storage means; a first calculation means for subtracting and outputting it as a first subtraction value for each electrical angle; a second calculation means for expanding the first subtraction value into a Fourier series and calculating only the commercial frequency component value; a third calculation means for calculating an effective value from the commercial frequency component value calculated by the second calculation means; a third storage means for storing the effective value calculated by the third calculation means; A past effective value calculated before the effective value stored in the storage means is stored as a second
a fourth storage means for storing as a reference storage value;
The fourth effective value is calculated from the latest effective value stored in the storage means.
a fifth calculation means for subtracting a second reference storage value stored in the storage means and outputting it as a second subtraction value; If the second subtraction value is less than or equal to the set value, the instantaneous value data group stored in the second storage means is deleted and stored in the first storage means. At the same time, the second reference storage value stored in the fourth storage means is updated to the effective value stored in the third storage means, and the second subtraction value is updated to the instantaneous value data group. is equal to or greater than the set value, a sixth calculation means that does not update the instantaneous value data group stored in the second storage means for at least one cycle thereafter; and A zero-sequence voltage detection device equipped with an output means for outputting data to a burden means. (3) The measurement means is a voltage dividing capacitor provided for each phase of the AC line, and a photovoltaic voltage that outputs an optical signal corresponding to the voltage divided by this voltage dividing capacitor and the ground capacitance of each phase. The zero-sequence voltage according to claim 1 or 2, wherein the zero-sequence voltage is comprised of a sensor, and is configured to add the optical signals from the optical voltage sensor using an adding means and then convert it into an electrical signal and output it as a zero-sequence voltage component. Detection device.