JP5618758B2 - Method and system for monitoring short-circuit capacity of power system - Google Patents

Description

  The present invention relates to a short-circuit capacity monitoring method and system for a power system capable of measuring a short-circuit capacity in accordance with the actual situation.

  When a short circuit failure occurs in the power system, a short circuit current flows from the generator connected to the system toward the short circuit point. The value obtained by multiplying the short-circuit current by the line voltage is the short-circuit capacity, but the short-circuit capacity tends to increase in recent power systems. This is because large-scale power sources are unevenly distributed in the backbone system, and the introduction of distributed power sources is expanding in the lower-level systems.

  If the short-circuit capacity of the electric power system increases, the short-circuit current that flows in the event of a system failure also increases, which may exceed the rated breaking capacity of existing circuit breakers. In this case, it is conceivable to replace the existing circuit breaker with a higher rated circuit breaker, but it cannot be denied that the cost will rise. In view of this, there has been proposed a technique for suppressing the short-circuit capacity of the power system by adopting a high-impedance device or a current-limiting reactor or by dividing the system.

  Above all, system division is very effective as a countermeasure for suppressing short-circuit capacity. Specifically, there are known methods such as a system that always divides the system, a method that introduces a new high-order system voltage and divides the existing system, and a method that divides the AC system using DCB (Back to Back). It has been.

  However, if the system division operation is implemented as a countermeasure for suppressing the short-circuit capacity of the power system, the system operation may be stiffened, and the merit of the grid connection may be impaired. In other words, in order to ensure the flexibility of system operation, it is desirable to minimize the system division operation.

  For that purpose, it is essential to accurately grasp the short-circuit capacity. By grasping the exact short-circuit capacity, it is possible to select a protection relay set value that matches the actual situation. That is, it is important to know the short-circuit capacity from the viewpoint of system protection.

  However, the short-circuit capacity of the power system depends on various factors such as the state of the system configuration at the time of the occurrence of a short-circuit failure (for example, system switching in the host system), the number of generators in parallel, the position of the short-circuit point, and the type of failure. , Its size and distribution change constantly.

  Since it is difficult to directly measure the short-circuit capacity of an electric power system, conventionally, the short-circuit capacity is calculated by using constants of predetermined system facilities such as transmission lines, transformers, and generators that make up the system. (For example, refer nonpatent literature 1). However, when using the constants of the system equipment, it is necessary to calculate after reflecting all the generator parallel arrangement states and the system configuration, which is troublesome. As a method for measuring a short-circuit capacity, an indirect short-circuit capacity measurement method for a power system is generally used. For example, the short-circuit capacity is indirectly obtained from the measured value of the voltage fluctuation rate associated with the insertion of the power capacitor or the shunt reactor (see Non-Patent Document 2).

Nittame Yuzo, “Application of Power System Technology Calculation”, Denki Shoin, Chapter 5, p.121-194 Nittame Shinzo, “Application of Power System Technology Calculation”, Denki Shoin, Chapter 9, p.401-402

  However, as already described, the short-circuit capacity of the power system constantly changes depending on the state of the system configuration. Therefore, it is not easy to strictly determine the short-circuit capacity that matches the actual situation, and the following problems have been pointed out in the above-described prior art. That is, as in Non-Patent Document 1, even if the short-circuit capacity is obtained by calculation using a system facility constant, it has not been possible to evaluate whether or not the calculation result actually shows the state of the system.

  Further, as in Non-Patent Document 2, when a simple calculation method for obtaining the short-circuit capacity indirectly from the measured value of the voltage fluctuation rate is used, the short-circuit capacity is determined based on the power capacitor or the shunt reactor input timing. Is measured. For this reason, it is difficult to measure the short-circuit capacity for a desired cross section.

  The present invention has been proposed to solve the above-described problem, and by using a plurality of data measured synchronously over time at a plurality of measurement points, the short-circuit capacity that matches the actual state in a desired cross section is grasped. It is an object of the present invention to provide a method and system for monitoring a short-circuit capacity of a power system that can be monitored.

  In order to achieve the above object, the present invention is a method for monitoring a short-circuit capacity of an electric power system, in which at least two measurement points via power transmission lines in the electric power system, the phasor amounts of voltage and current at each measurement point A data measurement step for synchronous measurement over time, a data collection step for collecting measurement data measured in the data measurement step, and a plurality of data at predetermined intervals based on the measurement data collected in the data collection step A data set creation step for creating a data set having the number of data, a back impedance estimation step for estimating a back impedance when the power source side is viewed from a short circuit point using the data set created in the data set creation step, and The short-circuit capacity is determined by the back impedance estimated in the back impedance estimation step. Characterized in that it comprises a short circuit capacity calculating step of calculation to.

  According to the short-circuit capacity monitoring method and system of the power system according to the present invention, the voltage and current phasor amounts are synchronously measured at a plurality of measurement points, and the back impedance is estimated and calculated using a plurality of synchronous measurement data. Based on the estimated back impedance, it is possible to calculate a short-circuit capacity that matches the actual situation, and it is possible to grasp and monitor an accurate short-circuit capacity.

1 is a configuration diagram of a first embodiment according to the present invention. The figure which shows the processing flow of 1st Embodiment. Explanatory drawing of the process which produces the data set for estimation from the voltage / current phasor amount of each measurement point in 1st Embodiment. Explanatory drawing of the electric power system at the time of the short circuit generation | occurrence | production in 1st Embodiment. Explanatory drawing of the equivalent circuit before the short circuit in 1st Embodiment. Explanatory drawing of the short circuit impedance in 1st Embodiment. Explanatory drawing of the equivalent circuit at the time of the short circuit in 1st Embodiment. Explanatory drawing of the electric power system at the time of short circuit generation | occurrence | production at the time of measuring at two points via a power transmission line in 1st Embodiment. Explanatory drawing of the equivalent circuit before a short circuit at the time of measuring in two points via a power transmission line in 1st Embodiment. Explanatory drawing of the short circuit impedance at the time of measuring in two points via a power transmission line in 1st Embodiment. Explanatory drawing of the equivalent circuit at the time of a short circuit at the time of measuring at two points via a power transmission line in 1st Embodiment. The figure which shows the processing flow of 2nd Embodiment which concerns on this invention. In 3rd Embodiment which concerns on this invention, it is a graph for demonstrating the case where the micro fluctuation | variation of a system | strain is large, Comprising: (a) is a distribution map of the amount of phasors of the estimation data set, (b) is a time change Conceptual diagram. In 3rd Embodiment which concerns on this invention, it is a graph for demonstrating the case where the micro fluctuation | variation of a system | strain is small, Comprising: (a) is a distribution map of the phasor amount of the estimation data set, (b) is a time change Conceptual diagram. It is a graph for demonstrating 4th Embodiment which concerns on this invention, Comprising: The graph which shows distribution without an outlier in the measured amount of voltage phasors. It is a graph for demonstrating 4th Embodiment which concerns on this invention, Comprising: The graph which shows distribution with the outlier in the measured voltage phasor amount. It is a graph for demonstrating 5th Embodiment which concerns on this invention, Comprising: When there is no outlier in the measured short circuit capacity, (a) is a short circuit capacity calculation result for every time, (b) is a fixed period The graph which shows distribution of short circuit capacity. It is a graph for demonstrating 5th Embodiment which concerns on this invention, Comprising: When a measured short circuit capacity has an outlier, the graph which shows distribution with an outlier in the measured voltage phasor amount. The figure which shows the processing flow of 6th Embodiment which concerns on this invention. The block diagram of the 7th Embodiment which concerns on this invention. Explanatory drawing of the process which produces the data set for estimation from the voltage / current phasor amount of each measurement point in other embodiment of this invention.

  Hereinafter, an example of an embodiment according to the present invention will be specifically described with reference to the drawings. In addition, in each embodiment, the same code | symbol is attached | subjected about the same structure and the overlapping description is abbreviate | omitted.

(1) First Embodiment [Configuration]
A first embodiment according to the present invention will be described with reference to FIG. The first embodiment is a system for monitoring a short-circuit capacity in the power system 1, and FIG. 1 is a configuration diagram of the first embodiment. As shown in FIG. 1, a plurality of generators 2 are connected to the power system 1 and a plurality of loads 4 are connected via a power transmission line 3. A synchronous measurement terminal 5 is installed at the connection point of each load 4. Reference numeral 6 denotes a synchronization signal satellite.

  The synchronization signal satellite 6 transmits a GPS (Grobal Positioning System) signal to the synchronization measurement terminal 5 as a synchronization signal. The synchronization measurement terminal 5 is configured to synchronously measure the phasor amount of the line voltage and the line current at the connection point of the load 4 over time using the synchronization signal transmitted from the synchronization signal satellite 6. Has been. In the following description, voltage and current represent line voltage and line current, respectively, and voltage / current phasor amounts are data relating to the magnitude and phase of voltage and current.

  The synchronous measurement terminal 5 incorporates a PMU (Phasor Measurement Unit). The PMU is a device that receives a GPS signal from the synchronization signal satellite 6 at a predetermined measurement period, realizes highly accurate phasor synchronous measurement using the received GPS signal as a synchronization signal, and outputs measurement data (phasor). (For communication standards, see IEEE Standard C37.118-2005). Each synchronous measurement terminal 5 is provided with a communication means for transmitting the voltage / current phasor amount as measurement data.

  In the short-circuit capacity monitoring system according to the first embodiment, the synchronous measurement terminal 5 and the synchronization signal satellite 6 constitute data measuring means, and the short-circuit capacity monitoring device 7 constitutes a main part of the system. The short-circuit capacity monitoring device 7 is connected to each synchronous measurement terminal 5 via communication means, and has a part having the following functions. That is, the short-circuit capacity monitoring device 7 includes a data collection storage unit 8 that collects and stores measurement data from each synchronous measurement terminal 5, an arithmetic processing unit 9 that performs an operation for obtaining a short-circuit capacity based on the measurement data, and a parameter. And a display / input / output unit 10 for setting and displaying results. The arithmetic processing unit 9 of the short-circuit capacity monitoring device 7 is provided with a data set creation unit 91, a back impedance estimation unit 92, and a short-circuit capacity calculation unit 93 as functional parts responsible for arithmetic processing.

[Overall process flow]
Next, the short-circuit capacity monitoring method for the power system according to the first embodiment will be specifically described with reference to the processing flow of FIG. First, using the synchronization signal transmitted from the synchronization signal satellite 6, the synchronization measurement terminal 5 synchronously measures the phasor amount D101 of the voltage / current at the measurement points 1 and 2 that are the measurement points over time (data measurement). Step S101), the data collection storage unit 8 of the short-circuit capacity monitoring device 7 collects and stores the voltage / current phasor amount D101 (data collection / storage step S102).

  Further, in the arithmetic processing unit 9 of the short-circuit capacity monitoring device 7, the data set creation step S103 by the data set creation unit 91, the back impedance estimation step S104 by the back impedance estimation unit 92, and the short circuit capacity calculation step S105 by the short circuit capacitance calculation unit 93 are performed. Do it sequentially.

  That is, the data set creation unit 91 creates a data set D102 having a plurality of data numbers n for each measurement cycle T0 based on the collected and stored phasor amounts D101 of voltage / current (data set creation step S103). Using this data set D102, the back impedance estimation means 92 estimates the back impedance D103 (back impedance estimation step S104). Finally, the short-circuit capacity calculating unit 93 calculates the short-circuit capacity D104 based on the estimated back impedance D103 (short-circuit capacity calculating step S105).

[Data set creation step]
Hereinafter, steps S103 to S105 performed by the arithmetic processing unit 9 will be described in detail. First, the data set creation step S103 by the data set creation unit 91 will be described with reference to FIG. FIG. 3 is an explanatory diagram regarding a method of creating the data set D102 from the voltage / current phasor amount D101 at the measurement points 1 and 2. FIG.

The voltage / current phasor amount D101 in FIG. 3 is the phasor amount of the line voltage and line current that are synchronously measured over time by the synchronous measurement terminal 5 at the measurement points 1 and 2. In the example shown in FIG. 3, n phasor amounts V _1k and I _1k of the voltage and current at each measurement point 1 and 2 are collected for each measurement period T0 (k = 1, 2,... N).

That is, on the measurement point 1 side, the phasor amounts V ₁₁ , I ₁₁ ,... V _1n , I _1n of n voltages and currents are collected, and a data set D102A is created from these measurement data. Also, n voltage and current phasor amounts V ₂₁ , I ₂₁ ,... V _2n , I _2n are collected on the measurement point 2 side, and a data set D102B is created from these measurement data. Note that the estimated sample interval T1 of the estimation data set D102 is set equal to the measurement interval T0. Further, in FIG. 3, a side point is added on the alphabet indicating the electric quantity, which indicates the phasor quantity. The same applies to the description of the phasor amount in the other drawings and the mathematical expressions described later.

[Back impedance estimation step]
In the back impedance estimation step S104, the back impedance estimation unit 92 estimates the back impedance using a plurality of data sets D102 created as described above.

FIG. 4 is a diagram showing a power system at the time of occurrence of a short circuit as a rear impedance Z _sys0 (= R _sys0 + jX _sys0 ) when viewing the power supply side from the short circuit point and a load impedance Z _{L2 when} viewing the load side from the short circuit point. is there. FIG. 5 is an equivalent circuit before a short circuit, and V _G (= V _Gr + jV _Gi ) is a back voltage.

_Regarding the back voltage V _G and the back impedance Z _sys0 , and the voltage / current phasor quantities V _k and I _k (k = 1, 2,... N), which are measurement data at one point, the relationship of the following equation (1) To establish.

If the following equation (2) is substituted into the above equation (1), the relationship of equation (1) can be expressed by equation (3).

At each measurement point, assuming that n voltage / current phasor quantities V _k and I _k are measured only during a minute fluctuation of the system and the rear impedance Z _sys0 does not change, V _rk , V _ik , The above equation (3) is established for a plurality of measurement data I _rk and I _ik .

Accordingly, for example, by applying the least square method, the back voltage V _G (= V _Gr + jV _Gi ) and the back impedance Z _sys0 (= R _sys0 + jX _sys0 ) can be obtained. The _solution of the back voltage V _G and the back impedance Z _sys0 is not limited to the least square method, and can be arbitrarily selected as long as it is a method for obtaining a solution that minimizes the error in the expression (3).

[Short-circuit capacity calculation step]
In the short circuit capacity calculation step S105, the short circuit capacity calculator 93 calculates the short circuit impedance Z _sc using the estimated back impedance Z _sys0 and the load impedance Z _L2 , and calculates the short circuit current I _sc and the short circuit capacity P _sc therefrom. To do.

The load impedance Z _L2 is obtained from the measured values of the voltage V and the current I by the following equation (4).

From Thevenin's theorem, the internal impedance viewed from the short-circuit point becomes the short-circuit impedance Z _sc (see FIG. 6), and the short-circuit impedance Z _sc is given by the following equation (5). That is, the product of the load impedance _{Z L2} and backward impedance _{Z sys0,} a value obtained by dividing by the sum of the load impedance _{Z L2} and back impedance _{Z sys0} becomes a short-circuit impedance _{Z sc.}

The value obtained by dividing the measurement point voltage V before short-circuiting by the short-circuit impedance Z _sc thus obtained is the short-circuit current _Isc (see equations (7) and (6)).

Furthermore, as shown in (7) below, can be determined short capacity P _sc by multiplying the measurement point voltage V before shorting the short-circuit current I _sc.

As described above, the short-circuit capacity calculator 92 uses the back impedance Z _sys0 estimated by the back impedance estimator 92 and the above equations (4) to (7), so that the short-circuit capacity P _sc and the short-circuit current I _sc. Is calculated. The obtained short-circuit capacity P _sc short-circuit current I _sc is obtained as a distribution of the number of data n in the data set D102. Therefore, the actual short-circuit capacity P _sc or the short-circuit current I _sc employs a median, mode or average value as a representative value.

[Back impedance estimation process when measured at two points via a transmission line]
Since there are transmission lines and loads in the system, in addition to measuring at multiple short-circuited points, measuring the phasor amount at points via the transmission lines provides redundancy and It is necessary to improve the accuracy of impedance estimation. Here, the back impedance estimation step in the case of measuring at two points through the power transmission line will be described.

About the power system at the time of occurrence of a short circuit, when represented by a rear impedance Z _sys (= R _sys + jX _sys ) viewed from the load end via the transmission line, a transmission line impedance Z _line , a load impedance Z _L1 , Z _L2 , As shown in FIG. An equivalent circuit before the short circuit is shown in FIG. From Thevenin's theorem, the internal impedance viewed from the short-circuit point is the short-circuit impedance Z _sc , which is expressed by the following equation (8) (see FIG. 10). An equivalent circuit at the time of a short circuit is shown in FIG.

Here, the load impedances Z _L1 and Z _L2 can be calculated from the measured values according to equations (9) and (10), respectively.

The transmission line impedance Z _line is calculated as a formula (11) using a constant or using a measured value.

In the case of two-point measurement, the back voltage V _G , the back impedance Z _sys , the transmission line impedance Z _line, and the measurement data (a plurality of voltage / current phasor amounts measured over time) V _1k , I _1k , V Regarding _2k and _I2k , the relationship of the following equation (12) is established.

When the following equation (13) is substituted into the above equation (12), the relationship of equation (12) is expressed by equation (14).

For the back voltage V _G (= V _Gr + jV _Gi ) and the back impedance Z _sys (= R _sys + jX _sys ), for example, the least square method is applied to the equation (14) in the same manner as in the case of one-point measurement. Can be solved. Note that the solution of the back voltage V _G and the back impedance Z _sys is not limited to the least square method, but can be selected as appropriate as long as it is a method for obtaining a solution that minimizes the error in equation (14). It is the same as the case of.

[Short-circuit capacity calculation processing when measured at two points via a transmission line]
The short-circuit impedance Z _sc can be calculated from the back impedance Z _sys estimated as described above and the above equations (8) to (11). The calculation result and the above equations (4) to (7) It is possible to determine the short-circuit current _Isc and the short-circuit capacitance _Psc . When such two-point measurement is performed, the load fluctuation at each measurement point can be captured by the measurement data, so that the estimation error of the back impedance Z _sys can be reduced.

[Function and effect]
As described above, in the first embodiment, the back impedance is estimated using a plurality of synchronous measurement data, and the short circuit capacity is calculated based on the estimated back impedance. It is possible to accurately determine the short-circuit capacity that matches the actual condition of the required cross section.

  Accordingly, it is possible to regularly monitor an accurate short-circuit capacity, and it is possible to limit the implementation to the minimum necessary case in the operation of system division as a short-circuit capacity suppression measure. Thereby, the flexibility of grid operation can be secured and the merit of grid connection can be utilized. Moreover, since the protection relay setting value that matches the actual situation can be selected, it is possible to contribute to the improvement of power quality.

(2) Second Embodiment [Configuration]
Next, a second embodiment according to the present invention will be described with reference to FIG. FIG. 12 shows an example of a processing procedure in the second embodiment.

  In the short-circuit capacity monitoring system for the power system according to the second embodiment, the three-phase voltage / current phasor amount D101 ′ at each measurement point is used as measurement data that is synchronously measured over time by the synchronous measurement terminal 5, The arithmetic processing unit 9 of the short-circuit capacity monitoring device 7 is characterized in that a positive phase calculation step S106 for performing a positive phase calculation is performed between the data collection / storage step S102 and the data set creation step S103.

  In the positive phase component calculation step S106, the three-phase voltage / current phasor amount D data 101 ′ measured by the synchronous measurement terminal 5 is input, and the positive phase component D105 of the voltage / current phasor amount is calculated by performing symmetric coordinate conversion. Further, the obtained normal phase portion D105 is sent to the data set creation means 91.

  Note that the normal phase calculation step S106 may be performed not on the calculation processing unit 9 of the short-circuit capacity monitoring device 7 but on the synchronous measurement terminal 5 side. In this case, the synchronous measurement terminal 5 synchronously measures the positive phase portion D104 of the voltage / current phasor amount with time, and sends the measured positive phase portion D105 to the short-circuit capacity monitoring device 7.

[Function and effect]
In the second embodiment, in addition to the operational effects of the first embodiment, the three-phase voltage / current phasor amount D101 ′ is adopted as measurement data, thereby eliminating the influence of unbalance in the system. it can. For this reason, it is possible to obtain the short-circuit capacity with higher accuracy.

(3) Third Embodiment [Configuration]
Subsequently, a third embodiment according to the present invention will be described. A feature of the third embodiment resides in a data set creation step S103 by the data set creation unit 91 of the short-circuit capacity monitoring device 7.

Since the estimation data set is composed of the voltage phasor amount and the current phasor amount measured multiple times, it has a certain distribution. In the third embodiment, in the data set creation step S103 by the data set creation unit 91, the sample period T1 and the data sets V _1k , I _1k , V _2k , I _2k (k = 1, 2,..., N). The feature is that the number n of included data is variable, and the measurement periods of the data sets V _1k , I _1k , V _2k , and I _2k are selected based on the distribution of the magnitude of the current I ₂ at an arbitrary measurement point. is there. For example, 10 measurement values of the distribution in which the standard deviation σ becomes a certain value within 30 minutes are selected as the estimation data sets V _1k , I _1k , V _2k , and I _2k . Since the magnitude of the standard deviation σ depends on the magnitude of the load at the measurement point, for example, a distribution that is 5% or more of the average load value is selected.

  Here, the graphs of FIGS. 13 and 14 are used to determine how to select the estimation data set when the minute fluctuation of the power system 1 is large and when the minute fluctuation of the power system 1 is small. explain. FIG. 13 shows the phasor amount distribution when the minute fluctuation of the power system 1 is large, and FIG. 14 shows the phasor amount distribution when the minute fluctuation of the system is small.

In FIGS. 13 and 14, (a) on the left side is a distribution chart of phasor amounts of data sets V _1k , I _1k , V _2k , and I _2k whose frequency is shown on the vertical axis, and (b) on the right side is the vertical axis. FIG. 6 is a conceptual diagram of time change showing the current I _2, and shows the distribution of the magnitude of the current I ₂ at one measurement point measured at a certain time.

Among these, the fact that the minute fluctuation of the power system 1 is large indicates that the distribution of the data sets V _1k , I _1k , V _2k , I _2k is large (in FIG. 13A, the data interval is left and right). Shows the spread in the direction). Further, if the minute fluctuation of the power system 1 is small, the dispersion of the distribution of the data sets V _1k , I _1k , V _2k , I _2k is also small (in FIG. 13B, the state where the data sections are gathered in the left-right direction). Show). At this time, if the measurement periods of the data sets V _1k , I _1k , V _2k , and I _2k are too short, a calculation error occurs. On the other hand, if the measurement periods of the data sets V _1k , I _1k , V _2k , and I _2k are too long, the rear impedance Z _{sys0 of the} system may change during the measurement period.

Therefore, in the third embodiment, the data sets V _1k , I _1k , V _2k , I _2k are considered in consideration of the measurement periods of the data sets V _1k , I _1k , V _2k , I _2k according to the fluctuation state of the system. The estimation data set creation unit 91 selects the sampling period T1 and the number of data n in the estimation data set so that the distribution width of the voltage / current phasor amount in FIG. In the above description, the measurement periods of the estimation data sets V _1k , I _1k , V _2k , and I _2k are selected on the basis of the current distribution. You may make it select the measurement period of a data set on the basis of distribution and phase distribution.

[Function and effect]
The third embodiment as described above has the following unique operational effects. That is, in the data set creation step S103 in the data set creation unit 91, when the data sets V _1k , I _1k , V _2k , and I _2k are created, the sample period T1 and the number of data n are variable, so that the back impedance Z _sys0 Can be estimated with high accuracy. Thereby, the calculation error can be reduced and the short-circuit capacity can be obtained with high accuracy.

(4) Fourth Embodiment [Configuration]
Next, a fourth embodiment according to the present invention will be described with reference to FIGS.

In the fourth embodiment, as in the third embodiment, the data set creation step S103 by the data set creation unit 91 is improved. That is, in the data set creation step S103 in the fourth embodiment, outliers are detected from the collected data sets V _1k , I _1k , V _2k , and I _2k , and after removing these, the data sets V _1k , I _1k , V _2k , and I _2k are created.

The data sets V _1k , I _1k , V _2k , and I _2k are composed of a voltage phasor amount and a current phasor amount that are measured a plurality of times, and thus have a constant distribution. The same applies to the current or phase distribution. 15 and 16 show the distribution of the magnitude of the voltage phasor amount at one measurement point measured at a certain time.

Of these, FIG. 15 shows a distribution with no outliers in the voltage phasor amount, and FIG. 16 shows a distribution with outliers in the voltage phasor amount. Outliers are data that deviate significantly from other distributions due to unforeseen fluctuations in the system. Such outliers can be detected by performing statistical processing such as Smirnov-Grubbs test. As shown in FIG. 16, when there is a value deviating from other measurement values in the distribution of the estimation data sets V _1k , I _1k , V _2k , and I _2k , the data set creation unit 91 excludes the outliers. In addition, data sets V _1k , I _1k , V _2k , and I _2k are created and given to the back impedance estimation unit 92.

[Function and effect]
According to the fourth embodiment as described above, outliers are previously removed from the data sets V _1k , I _1k , V _2k , and I _{2k in} the data set creation step S103 performed by the data set creation unit 91. There is no worry of being affected by unexpected fluctuations in the system. Therefore, it is possible to increase the estimation accuracy of the back impedance Z _sys0 and reduce the calculation error. Thereby, it is possible to always obtain an accurate short-circuit capacity.

(5) Fifth Embodiment [Configuration]
Next, a fifth embodiment according to the present invention will be described with reference to FIGS.

The fifth embodiment, like the fourth embodiment, excludes outliers at the time of calculation processing, but does not exclude outliers when performing the data set creation step S103. It is characterized in that outliers are excluded from the short-circuit capacity P _sc or the short-circuit current I _sc when S105 is performed.

In the conceptual diagrams shown in FIGS. 17 and 18, the calculation result of the short-circuit capacity P _{sc at} each time ((a) in the upper part of each figure) and the distribution of the short-circuit capacity P _sc for a certain period ((b) in the lower part of each figure). ). By sequentially repeating the short-circuit capacity calculation step by the short-circuit capacity calculator 93, the time change of the short-circuit capacity P _sc can be seen. FIG. 17 shows a case where there is no outlier of the short-circuit capacity P _sc , and FIG. 18 shows a case where there is an outlier of the short-circuit capacity P _sc .

In the short-circuit capacity calculation performed once by the execution of the short-circuit capacity calculation step S105, the distribution of the short-circuit capacity P _sc is obtained. Therefore, representative values (for example, the median value, the mode value, or the average value of the distribution) are calculated and plotted. ing. The representative value of the short-circuit capacitance P _sc for a certain period has a distribution. At this time, if there is an outlier that deviates from other measured values in the distribution of the short-circuit capacity calculation results as shown in FIG. 18B, the outlier is removed. Note that outliers can be detected by performing statistical processing such as the Smirnov-Grubbs test, as in the fourth embodiment.

[Function and effect]
According to the fifth embodiment as described above, by removing the short-circuit capacity P _sc that is an outlier in the short-circuit capacity calculation step by the short-circuit capacity calculation unit 93, it is possible to reliably prevent the influence of unexpected fluctuations or sudden changes in the system. Can be eliminated.

(6) Sixth Embodiment [Configuration]
A sixth embodiment according to the present invention will be described with reference to FIG. FIG. 19 is a diagram illustrating a processing flow according to the sixth embodiment.

As shown in FIG. 19, in the sixth embodiment, a plurality of short-circuit capacity calculation methods 1 to m having different characteristics are prepared and set in advance in the short-circuit capacity calculation step S105 by the short-circuit capacity calculator 93. One of the plurality of short-circuit capacity calculation methods 1 to m is selected based on the determined criteria. At this time, with respect to criterion calculation method, system configuration status, short-circuit capacity P _sc size, it is possible to set the time change, such as small fluctuation range of the system, a plurality of reference short-circuit capacity P _sc.

For example, five short-circuit capacity calculation methods are prepared, and the most common calculation method is the calculation method 1. Calculation method 2 has a characteristic of being resistant to minute fluctuations in the system, and calculation method 3 is effective when there is a load between measurement points. The calculation method 4 can cope with the time change of the short-circuit capacity P _sc , and the calculation method 5 is advantageous when the short-circuit capacity P _sc is small.

In such calculation methods 1 to 5, the calculation method 1 is the default, and the determination criteria for determining the selection of the calculation methods 2 to 5 are as follows. In calculation method 2, the threshold value σ of minute fluctuations, in calculation method 3, the presence of a load, in calculation method 4, the presence / absence of a change in the short-circuit capacity P _sc over time, and in calculation method 5, the threshold P _scX of the short-circuit capacity P _sc .

That is, when the system minute fluctuation is smaller than the threshold value σ, or when there is no load between the measurement points, or when the short circuit capacity is constant, or when the short circuit capacity P _sc is larger than the threshold value P _scX , the short circuit capacity calculation unit 93 In the short-circuit capacity calculation step S105, the short-circuit capacity calculation method 1 is adopted.

On the other hand, the calculation method 2 is adopted when the system minute fluctuation is larger than the threshold σ. Further, calculation method 3 is adopted when there is a load between measurement points, and calculation method 4 is adopted when the short-circuit capacitance P _sc changes over time. Furthermore, when the short-circuit capacity P _sc is smaller than the threshold value P _scX , the calculation method 5 is employed.

  In addition, when the adoption criteria of the calculation methods 2-5 overlap, the priority of each calculation method adopts only one calculation method as the order of the calculation methods 2, 3, 4, 5. For example, when the system minute fluctuation is larger than the threshold value σ and there is a load between the measurement points, the calculation method 2 is adopted because the adoption criteria of the calculation methods 2 and 3 are satisfied.

In addition, when the short-circuit capacity _sc varies with time and the short-circuit capacity P _sc is smaller than the threshold value P _scX , the calculation criteria 4 and 5 are satisfied, and therefore the calculation method 4 is adopted. Instead of adopting only one calculation method, a plurality of calculation methods among the calculation methods 1 to 5 are employed to obtain a plurality of short-circuit capacities P _sc , and finally one short-circuit capacity P _sc. May be selected.

[Function and effect]
According to the sixth embodiment as described above, in addition to the operation and effect of the above embodiment, the short-circuit capacity can be obtained with high accuracy by adopting an optimal calculation method according to the state of the system. It can demonstrate its own effects.

(7) Seventh Embodiment [Configuration]
A seventh embodiment according to the present invention will be described with reference to FIG. FIG. 20 is a configuration diagram of the seventh embodiment. As shown in FIG. 20, in the short-circuit capacity monitoring system according to the seventh embodiment, the short-circuit capacity monitoring device 7 includes the communication control unit 11, and the voltage / current phasor amount is online from the synchronous measurement terminal 5 via the transmission line 12. It is characteristic to collect in.

[Function and effect]
According to the seventh embodiment having the above-described configuration, the short-circuit capacity estimation calculation can be sequentially performed using the voltage / current phasor amount measured online. For this reason, the short-circuit capacity can be continuously monitored continuously, which can contribute to the improvement of the reliability of the power system.

(8) Other Embodiments The present invention is not limited to the above embodiment, and the number of synchronous measurement terminals installed, the configuration of the short-circuit capacity monitoring device, and the like can be changed as appropriate. For example, in the first embodiment, the estimated sample interval T1 of the estimation data set D102 is equal to the measurement interval T0. However, the estimated sample interval T1 may not be equal to the measurement interval T0, as shown in FIG. Alternatively, the estimated sample interval T1> the measurement interval T0 may be set. In this way, it is also possible to create a data set D102 with the number of data n for each estimated sample period T1.

DESCRIPTION OF SYMBOLS 1 ... Electric power system 2 ... Generator 3 ... Transmission line 4 ... Load 5 ... Synchronous measurement terminal 6 ... Synchronous signal satellite 7 ... Short-circuit capacity monitoring device 8 ... Data collection and storage part 9 ... Arithmetic processing part 91 ... Data set preparation part 92 ... Back impedance estimation unit 93 ... Short circuit capacity calculation unit 10 ... Display / input / output unit 11 ... Communication control unit 12 ... Transmission path

Claims (6)

A method for monitoring a short-circuit capacity of a power system,
A data measurement step for synchronously measuring the phasor amount of the voltage and current at each measurement point over time at at least two measurement points via a transmission line in the power system,
A data collection step for collecting measurement data measured in the data measurement step;
A data set creation step for creating a data set having a plurality of data per predetermined period based on the measurement data collected in the data collection step;
A back impedance estimation step for estimating a back impedance when the power source side is viewed from a short circuit point using the data set created in the data set creation step;
A method for monitoring a short-circuit capacity of a power system, comprising a short-circuit capacity calculation step of calculating a short-circuit capacity based on the back impedance estimated in the back impedance estimation step.   The method for monitoring a short-circuit capacity of an electric power system according to claim 1, wherein, in the data set creation step, the sampling period and the number of data included in the data set are made variable according to the fluctuation state of the system.   3. The short-circuit capacity monitoring method for a power system according to claim 1, wherein outliers are excluded from the data set in the data set creation step. Wherein the short circuit capacity calculating step, short capacity monitoring method for a power system according to any one of claims 1 to 3, characterized in that except for the outliers in the calculated short capacity. A communication step of collecting the voltage and current phasor amounts collected in the short-circuit capacity measurement step online;
Short space monitoring method for a power system according to any one of claims 1 to 4, characterized in that to calculate the short-circuit capacity sequentially in the short capacity calculation step. A system for monitoring the short-circuit capacity of a power system,
Data measurement means for synchronously measuring the amount of phasor of voltage and current at each measurement point over time at at least two measurement points via a transmission line in the power system;
Data collection means for collecting measurement data measured by the data measurement means;
Data set creation means for creating a data set having a plurality of data per predetermined cycle based on the measurement data collected by the data collection means,
A back impedance estimating means for estimating a back impedance when the power source side is viewed from a short circuit point using the data set created by the data set creating means;
A short-circuit capacity monitoring system for a power system, comprising short-circuit capacity calculating means for calculating a short-circuit capacity based on the back impedance estimated by the back impedance estimating means.

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