JP7196716B2 - Short-circuit monitoring device, short-circuit monitoring method, and program - Google Patents

Description

TECHNICAL FIELD Embodiments of the present invention relate to a short-circuit monitoring device, a short-circuit monitoring method, and a program.

When a short-circuit accident occurs in a distribution line, a current (overcurrent) generally larger than the current supplied to the load flows from each power supply toward the short-circuit point.
A device for detecting overcurrent, such as an overcurrent relay (OCR), is installed at a branching portion from a distribution substation to each distribution line. The OCR detects a short-circuit accident when a current greater than a set threshold flows for a certain period of time, and operates a circuit breaker on the faulty distribution line to protect the distribution line.

With respect to technology for detecting short-circuit accidents in distribution lines, there is known a technology for detecting short-circuit accidents in distribution lines and protecting the entire system in a power supply system using a converter (see, for example, Patent Document 1). ). In this technology, the protection device consists of a harmonic supply unit that supplies harmonics (integer harmonics or interharmonics) to the bus, a voltage measurement unit that measures the voltage of the bus, and a current that measures the current in the distribution line. a current measurement unit that calculates a harmonic component from each of the measured waveforms of the voltage and current; an impedance calculation unit that calculates impedance from the harmonic components of the voltage and current; and a control unit that determines whether or not a short-circuit accident has occurred in the distribution line based on the above. As a result, it is possible to detect a short-circuit accident that has occurred in a distribution line, disconnect the concerned distribution line from the busbar, and prevent the power failure of the entire system.

JP 2018-183034 A

Consider a system configuration in which rotating machines such as diesel generators are disconnected from the power supply, and renewable energy such as solar power and wind power and a storage battery are used as the main power sources of the system. Such a system configuration is also called an off-grid system. In other words, an off-grid system refers to a power system that is not connected to a power transmission/distribution system, which is a power network in which power is transmitted from a power company to consumers such as homes through electric wires.
In such an electric power system, a storage battery is provided with a power conditioner (PCS: Power Conditioning System). The PCS converts the DC power output by the storage battery from DC to AC, and outputs the converted AC power to the transformer. The transformer adjusts the voltage of the converted AC power output by the PCS, and outputs the voltage-adjusted power to the bus. A plurality of distribution line feeders are connected to the busbar. An OCR is connected to each of the plurality of distribution lines. Consumers are connected to the distribution line.
If a short circuit occurs in the distribution line, the short-circuit current limited to the PCS capacity is supplied from the PCS to the distribution line via the transformer and the bus. is smaller than the threshold set in the OCR, and it is assumed that a current greater than the threshold does not flow through the OCR. Therefore, even if a short-circuit accident occurs, the OCR may not be able to detect the occurrence of the short-circuit.
If the threshold value set in the OCR is changed to a smaller value, there is a possibility that the short-circuit current and the load current cannot be distinguished.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned points, and its object is to provide a short-circuit monitoring device capable of monitoring short-circuits occurring in distribution lines in a system configuration in which renewable energy and a storage battery are the main power sources of the system. , short circuit monitoring method and program.

One aspect of the present invention is a short-circuit monitoring device for monitoring a short circuit in a distribution line that supplies electricity output by a power conditioner installed in a storage battery to a load in an off-grid system, and includes information indicating current flowing in the distribution line. a receiving unit for receiving information indicating the power factor angle of the distribution line; a current change amount deriving unit for deriving the amount of change in the current based on the information indicating the current received by the receiving unit; a power factor angle change amount derivation unit for deriving a change amount of the power factor angle based on the information indicating the power factor angle received by the reception unit; a determining unit that determines whether or not the distribution line is short-circuited based on information indicating the amount of change and information indicating the amount of change in the power factor angle derived by the power factor angle change amount deriving unit; A short circuit monitoring device comprising:
In the short-circuit monitoring device according to the aspect of the present invention, the determination unit divides a value obtained by normalizing the amount of change in the current by a limit value of the current output by the power conditioner, and the power factor angle It is determined that the distribution line is short-circuited when the sum of the value obtained by multiplying the change amount by the weighting factor is greater than the change rate threshold.
In one aspect of the short circuit monitoring device of the present invention, the weighting factors are derived based on a three-phase short circuit.
In the short-circuit monitoring device of one aspect of the present invention, the change rate threshold is derived based on past actual measurement data.
In the short-circuit monitoring device according to one aspect of the present invention, the reception unit receives information indicating a bus voltage, which is a voltage flowing in a bus to which the distribution line is connected, and the short-circuit monitoring device receives information received by the reception unit. a voltage change amount derivation unit for deriving a change amount of the bus voltage based on the information indicating the bus voltage, and the determination unit determines the change amount of the bus voltage derived by the voltage change amount derivation unit. Based on the information shown, it is determined whether or not the distribution line is short-circuited.
One aspect of the present invention is a short-circuit monitoring method executed by a short-circuit monitoring device that monitors a short-circuit in a distribution line that supplies electricity output by a power conditioner installed in a storage battery to a load in an off-grid system. a step of receiving information indicating the current flowing through the distribution line and information indicating the power factor angle of the distribution line; and a step of deriving the amount of change in the current based on the information indicating the current received in the receiving step. deriving the amount of change in the power factor angle based on the information indicating the power factor angle received in the receiving step; information indicating the amount of change in the current; and the change in the power factor angle. and determining whether the distribution line is short-circuited based on the information indicating the quantity.
In one aspect of the present invention, in an off-grid system, a computer of a short-circuit monitoring device that monitors short-circuits in distribution lines that supply electricity output by a power conditioner attached to a storage battery to a load is provided with information indicating the current flowing in the distribution lines. a step of receiving information indicating the power factor angle of the distribution line, a step of deriving the amount of change in the current based on the information indicating the current received in the receiving step, and a step of receiving in the receiving step deriving the amount of change in the power factor angle based on the information indicating the power factor angle; based on information indicating the amount of change in the current; and information indicating the amount of change in the power factor angle. and determining whether or not the distribution line is short-circuited.

According to the embodiment of the present invention, it is possible to monitor a short circuit occurring in a distribution line in a system configuration in which renewable energy and a storage battery are the main power sources of the system.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which shows an example of the electric power system in which the short circuit monitoring apparatus of embodiment is applied. 1 is a schematic diagram showing an example of a case where a solar cell stops in an electric power system to which the short-circuit monitoring device of the embodiment is applied; FIG. FIG. 2 is a diagram showing Example 1 of a phenomenon that occurs when a short-circuit accident occurs; FIG. 10 is a diagram showing Example 2 of a phenomenon that occurs when a short-circuit accident occurs in a feeder; FIG. 10 is a diagram showing example 3 of a phenomenon that occurs when a short-circuit accident occurs in a feeder; FIG. 5 is a diagram showing an example of waveforms of phase-to-phase voltages when a short-circuit accident occurs in a feeder; FIG. 5 is a diagram showing an example of waveforms of phase currents when a short-circuit accident occurs in a feeder; FIG. 5 is a diagram showing an example of changes in power factor angle when a short-circuit accident occurs in a feeder; It is a figure which shows the comparative example of the interphase voltage, phase current, and power factor angle before and after the short circuit accident of a two-phase short circuit and a three-phase short circuit. It is a figure which shows an example of the short circuit monitoring apparatus of embodiment. FIG. 5 is a diagram showing an example of the relationship between load current and the sum of change rates; It is a figure which shows an example of the relationship between load current and change rate. 4 is a sequence chart showing an example of the operation of the short circuit monitoring system of the embodiment;

Next, the short-circuit monitoring device, short-circuit monitoring method, and program of this embodiment will be described with reference to the drawings. The embodiments described below are merely examples, and embodiments to which the present invention is applied are not limited to the following embodiments.
In addition, in all the drawings for explaining the embodiments, the same reference numerals are used for the parts having the same functions, and repeated explanations are omitted.
In addition, "based on XX" in the present application means "based on at least XX", and includes cases based on other elements in addition to XX. Moreover, "based on XX" is not limited to the case of using XX directly, but also includes the case of being based on what has been calculated or processed with respect to XX. "XX" is an arbitrary element (for example, arbitrary information).

(embodiment)
(power system)
FIG. 1 is a schematic diagram showing an example of a power system to which a short circuit monitoring device according to an embodiment is applied.
The power system 1 of the first embodiment is an off-grid system. As described above, an off-grid system refers to a power system that is not connected to a power transmission and distribution system, which is a power network that transmits power from power companies to consumers such as homes through wires.
The power system 1 includes a voltage source 10a, a transformer 20a, an OCR 30, a short-circuit monitoring device 100, a sensor-incorporated automatic switch remote controller 40-1, a sensor-incorporated automatic switch remote controller 40-2, It has a remote controller 40-3 for an automatic switch with a built-in sensor, a current source 10b, and a transformer 20b.
The voltage source 10a includes a storage battery 12a and a PCS 14a. The storage battery 12a, the PCS 14a, and the transformer 20a are connected to the bus B by a transmission/distribution line TLa. The OCR 30, the sensor built-in automatic switch remote controller 40-1, the sensor built-in automatic switch remote controller 40-2, and the sensor built-in automatic switch remote controller 40-3 are connected by a feeder (distribution line) F. , is connected to the bus B. A consumer is connected to the feeder F. The short-circuit monitoring device 100 is installed side by side with the OCR 30 .
The current source 10b includes a solar cell 12b and a PCS 14b. Solar cell 12b, PCS 14b, and transformer 20b are connected to bus B by transmission/distribution line TLb.

The storage battery 12a is a battery (secondary battery) that can store electricity by charging and can be used repeatedly. A lead-acid battery, a nickel-hydrogen storage battery, a lithium-ion battery, a redox flow battery, or the like can be applied as the storage battery 12a. The storage battery 12a outputs the stored electricity to the PCS 14a.
The PCS 14a is connected to the storage battery 12a by a transmission line TLa. The PCS 14a acquires electricity (discharge power) output by the storage battery 12a and converts the acquired electricity from direct current to alternating current. The PCS 14a outputs the electricity converted into alternating current to the transformer 20a.
In addition, the PCS 14a performs output suppression in order to transmit the electricity output by the storage battery 12a to the power system.
If a short-circuit accident occurs in the feeder F, the PCS 14a outputs a short-circuit current limited to the output capacity of the storage battery 12a to the transformer 20a. For example, the short-circuit current output by the PCS 14a is limited to 1.1 to 1.5 times the output capacity of the storage battery 12a. Hereinafter, the ratio of the short-circuit current output by the PCS 14a to the output capacity of the storage battery 12a is referred to as "limitation ratio".
The transformer 20a is connected to the PCS 14a by a transmission line TLa. The transformer 20a converts the voltage of the AC power output by the PCS 14a for transmission to the power system, and outputs the AC power whose voltage has been converted to the bus B.
The solar cell 12b is a power device that utilizes the photovoltaic effect and converts light energy into power. The solar cell 12b immediately converts light into electric power by the photovoltaic effect, and outputs the electric power obtained by converting the light into electric power to the PCS 14b.
The PCS 14b is connected to the solar cell 12b by a transmission line TLb. The PCS 14b acquires the power output by the solar cell 12b and converts the acquired power from direct current to alternating current. The PCS 14b outputs the electricity converted into alternating current to the transformer 20b.
In addition, the PCS 14b performs output suppression in order to transmit the electricity output by the solar cell 12b to the power system.
If a short-circuit accident occurs in the feeder F, the PCS 14b outputs a short-circuit current limited to the output capacity of the solar cell 12b to the transformer 20b. For example, the short-circuit current output by the PCS 14b is limited to 1.1 to 1.5 times the output capacity of the solar cell 12b.
The transformer 20b is connected to the PCS 14b by a transmission line TLb. The transformer 20b converts the voltage of the AC power output by the PCS 14b so as to transmit it to the power system, and outputs the voltage-converted AC power to the bus B.
The bus B is a conductor that becomes the main circuit of the power receiving and transforming equipment. A bus B is an electric line from the secondary side of a transformer to a distribution circuit breaker in a high-voltage power receiving consumer. AC power is supplied to bus B from transformers 20a and 20b. Mother B outputs to feeder F the AC power supplied from transformer 20a and transformer 20b.

OCR 30 is connected to bus line B via feeder F. The OCR 30 detects current based on AC power supplied from the bus B through the feeder F. In addition, the OCR 30 determines that a short-circuit accident has occurred in the feeder F when a current larger than the set threshold flows in the feeder F for a certain period of time, and the breaker of the feeder F where the short-circuit accident has occurred to operate.
The OCR 30 also detects a power factor angle and outputs information indicating the detected power factor angle to the short-circuit monitoring device 100 together with information indicating the detected current.
The OCR 30 receives the short-circuit occurrence notification output by the short-circuit monitoring device 100 and obtains information indicating that a short-circuit accident has occurred, which is included in the received short-circuit occurrence notification. OCR30 operates the breaker of the feeder F connected with OCR30 based on the information which shows that the acquired short circuit accident has generate|occur|produced.
The voltage sensor 50 measures the bus voltage, which is the voltage applied to the bus B, and superimposes on the bus B information indicating the measured bus voltage. Information indicative of the bus voltage superimposed on bus B is transmitted to feeder F.
Each of the sensor built-in automatic switch remote controller 40-1, the sensor built-in automatic switch remote controller 40-2, and the sensor built-in automatic switch remote controller 40-3 is electrically connected (turned on) between its terminals. and insulation (open). The remote controller 40-1 for the automatic switch with sensor, the remote controller 40-2 for the automatic switch with sensor, and the remote controller 40-3 for the automatic switch with sensor are each used for recovering from the feeder F accident. If applicable, it automatically switches from open to closed under certain conditions. An example of an accident is a short circuit. In addition, when an accident such as a ground fault occurs in the feeder F, the circuit breaker of the substation is opened by the relay, and the remote controller 40-1 for the automatic switch with a sensor and the remote controller 40- for the automatic switch with a sensor are installed. 2 and the sensor built-in automatic switch remote controller 40-3 are also opened. In addition, each of the remote controller 40-1 for automatic switch with sensor, the remote controller 40-2 for automatic switch with sensor, and the remote controller 40-3 for automatic switch with sensor is used for the circuit breaker of the substation. When power is supplied from a predetermined direction by re-supplying, the timer is activated, and when the timer detects the elapse of the predetermined time, the power is switched to on.
Here, consider a case where the solar cell 12b stops due to nighttime, rainy weather, or the like.
FIG. 2 is a schematic diagram showing an example of a case where the solar cell stops in the electric power system to which the short-circuit monitoring device of the embodiment is applied.
When the solar cell 12b stops due to nighttime, rain, or the like, the electricity converted into alternating current is not output from the current source 10b to the transformer 20b. That is, when it is nighttime or rainy weather, the solar cell 12b has little light energy, so the power obtained by converting the light energy into power is also small, so it is stopped.
When the solar cell 12b stops, power is supplied to the feeder F from the voltage source 10a. In this case, since the power supplied from the current source 10b to the feeder F can be omitted, the description will be continued assuming that power is supplied to the feeder F from the voltage source 10a.
A case where a short circuit occurs at the short-circuit point SP of the feeder F while the solar cell 12b is stopped and power is being supplied from the voltage source 10a to the feeder F will be described. In other words, a case where a short-circuit accident occurs in the feeder F while power is being supplied to the feeder F from the voltage source 10a will be described.
In this embodiment, when a ground fault occurs, the ground fault current passes through the ground fault relay from the accident point via the grounded voltage transformer (EVT). Since it is a path, it does not depend on the connection or disconnection of diesel. For this reason, it is possible to detect ground faults and cut off ground faults with existing equipment, so the description will be omitted.
Also, when diesel is connected to bus B, that is, when diesel is connected to bus B, or when diesel, storage battery 12a, and solar battery 12b are connected in parallel to bus B , a short-circuit current that can be detected by the OCR 30 flows from the diesel, so the existing equipment can detect a ground fault and cut off, so the description is omitted.
The short-circuit current Is supplied from the voltage source 10a is represented by Equation (1) when the rated value of the high voltage is 3.3 kV.

Is = (output capacity of storage battery [kVA]) / (√3 x 3.3 [kV]) x (limit magnification) (1)

It is assumed that the output capacity of the storage battery 12a is 8 MWh, and the limiting multiplier of the current supplied from the PCS 14a to the transformer 20a to the capacity of the storage battery 12a is 1.1. By substituting the above numerical values into equation (1), Is = 154 [A] is obtained. That is, when a short-circuit accident occurs in the feeder F, it is assumed that a short-circuit current of Is=154 [A] flows through the distribution line TLa. Hereinafter, the short-circuit current Is may also be referred to as a current limit value IL.
In an off-grid system in which the storage battery 12a and the solar battery 12b are connected in parallel to the bus B, the power stored in the storage battery 12a is supplied to the feeder F without using the power generated by the solar battery 12b. is assumed to be the most severe condition. In other words, in the case where the power stored in the storage battery 12a is supplied to the feeder F, if a short-circuit accident occurs in the feeder F, it is assumed that it is difficult to detect the short-circuit accident. Therefore, in the present embodiment, the case where the power stored in the storage battery 12a is supplied to the feeder F without using the power generated by the solar cell 12b will be described.
If 345 [A] is set in the OCR 30 as a setting value for detecting the occurrence of a short-circuit accident, the setting value is the above-described short-circuit current Is (=154 [A]) bigger than OCR 30 cannot detect that a short-circuit accident has occurred even when a short-circuit accident has occurred in the feeder F.
In this embodiment, the short-circuit monitoring device 100 attached to the OCR 30 determines whether or not the feeder F has a short-circuit accident.
The short-circuit monitoring device 100 receives the measurement result of the voltage superimposed on the feeder F, and accepts the received measurement result of the voltage. The short-circuit monitoring device 100 receives the information indicating the current output from the OCR 30 and the information indicating the power factor angle, and accepts the received information indicating the current and the information indicating the power factor angle.
The short-circuit monitoring device 100 derives the voltage change amount based on the received information indicating the voltage. The short-circuit monitoring device 100 determines whether or not a short-circuit accident has occurred based on the derived information indicating the amount of change in voltage.
When the short-circuit monitoring device 100 determines that a short-circuit accident has occurred, the short-circuit monitoring device 100 derives the amount of change in current based on the received information indicating the current. The short-circuit monitoring device 100 derives the amount of change in the power factor angle based on the received information indicating the power factor angle. The short-circuit monitoring device 100 identifies the feeder F in which the short-circuit accident has occurred based on the derived information indicating the amount of change in current and the information indicating the amount of change in the power factor angle.

Here, with reference to FIGS. 3 to 5, a phenomenon that occurs when a short-circuit accident occurs in the feeder F will be described.
FIG. 3 is a diagram showing Example 1 of a phenomenon that occurs when a short-circuit accident occurs.
FIG. 3 shows changes in system voltage when a short-circuit accident occurs in each of the bus B and the feeder F. In FIG. In FIG. 3, the horizontal axis is time and the vertical axis is voltage. In FIG. 3, the left side of the dashed line shows the situation before the occurrence of the short-circuit accident, and the right side shows the situation after the occurrence of the short-circuit accident. Compared to the power supply voltage before the short circuit occurred, after the short circuit occurred, the amplitude decreased when the short circuit occurred on the bus B and when the short circuit occurred on the feeder F. I know you do. Furthermore, when a short-circuit fault occurs at the end of a distribution line and a short-circuit fault occurs at a bus bar, it can be seen that the amount of decrease in amplitude is greater when a short-circuit fault occurs at the bus bar.

FIG. 4 is a diagram showing example 2 of a phenomenon that occurs when a short-circuit accident occurs in a feeder.
FIG. 4 shows changes in current when a short circuit accident occurs in the feeder F. FIG. In FIG. 4, the horizontal axis is time and the vertical axis is current. In FIG. 4, the left side of the dashed line shows the situation before the short circuit accident, and the right side of the broken line shows the situation after the short circuit accident.
It can be seen that the amplitude of the short-circuit current after the occurrence of the short-circuit fault is increased compared to the load current before the occurrence of the short-circuit fault. This is because when a short-circuit accident occurs in the feeder F, the PCS 14a suppresses the short-circuit current based on the output capacity of the storage battery 12a and the limit magnification, but the suppressed short-circuit current is larger than the load current. is.

FIG. 5 is a diagram showing example 3 of a phenomenon that occurs when a short-circuit accident occurs in a feeder.
FIG. 5 shows changes in the power factor angle when an interphase two-phase short-circuit fault between the a phase and the b phase of the feeder F occurs. FIG. 5 shows the phase voltage va of the a-phase, the phase voltage vb of the b-phase, the inter-phase voltage vab of the a-phase and the b-phase, and the inter-phase voltage vbc of the b-phase and the c-phase before the short-circuit accident occurs. , and the phase-to-phase voltage vca between the c-phase and the a-phase are indicated by dashed lines.
Further, FIG. 5 shows the phase voltage va of the a phase after the occurrence of the short circuit, the phase voltage vb of the b phase, the interphase voltage vab of the a phase and the b phase, and the interphase voltage of the b phase and the c phase. The voltage vbc and the phase-to-phase voltage vca between the c-phase and the a-phase are indicated by solid lines.
It can be seen that the power factor angle varies with the phase voltage and the phase current in each phase in the two-phase short-circuit fault and the three-phase short-circuit fault. In other words, when Ia indicated by the solid line and Ia indicated by the broken line are compared, it can be seen that there is a change.

FIG. 6 is a diagram showing an example of the interphase voltage waveform when a short-circuit accident occurs in the feeder. The example shown in FIG. 6 shows the result of a simulation when a two-phase short-circuit accident between phases a and b under heavy load occurs. In FIG. 6, the left side of the dashed line is the interphase voltage waveform before the short circuit accident (steady state), and the right side of the broken line is the interphase voltage waveform after the short circuit fault (short circuit state). be.
As can be seen from FIG. 6, when a short-circuit fault occurs between the a-phase and the b-phase, the interphase voltage between the a-phase and the b-phase decreases. Therefore, it can be determined that a short-circuit accident has occurred when a drop in inter-phase voltage is detected.
Here, the case where the inter-phase voltage between the a-phase and the b-phase drops when a short-circuit fault occurs between the a-phase and the b-phase is shown. The same applies to the case where a short-circuit accident occurs and the case where a short-circuit accident occurs between the c-phase and the a-phase. When a short-circuit accident occurs between the b-phase and the c-phase, the interphase voltage between the b-phase and the c-phase decreases. When a short-circuit accident occurs between the c phase and the a phase, the interphase voltage between the c phase and the a phase drops.
However, when it is determined that a short-circuit fault has occurred by detecting a drop in the inter-phase voltage, the inter-phase voltage is detected by measuring the voltage applied to the bus. The feeder F in which the short-circuit accident occurred cannot be identified only by detection. Furthermore, when it is determined that a short-circuit accident has occurred based on the detection of a drop in the voltage between phases, priority selective cutoff is required.

FIG. 7 is a diagram showing an example of waveforms of phase currents when a short-circuit accident occurs in a feeder. The example shown in FIG. 7 shows the results of a simulation when a two-phase short-circuit accident between phases a and b under heavy load occurs. In FIG. 7, the left side of the dashed line is the waveform of the phase current before the occurrence of the short circuit (steady state), and the right side of the broken line is the waveform of the phase current after the occurrence of the short circuit (short circuit state). be.
According to FIG. 7, the current amplitudes of the a-phase, b-phase, and c-phase currents increase at the moment when a short-circuit fault occurs between the a-phase and the b-phase. After that, it can be seen that the current amplitude of any one of the a-phase, b-phase, and c-phase currents continues to increase under the control of the PCS 14a. Therefore, it can be determined that a short-circuit accident has occurred when the a-phase, b-phase, and c-phase phase currents increase.
Here, the case where the current amplitudes of the a-phase, b-phase, and c-phase currents increase at the moment when a short-circuit fault occurs between the a-phase and the b-phase is shown. However, the same applies to cases where a short-circuit fault occurs between the b-phase and the c-phase and between the c-phase and the a-phase. That is, at the moment when a short-circuit accident occurs between the b-phase and the c-phase, the current amplitudes of the a-phase, b-phase, and c-phase phase currents increase. , the current amplitude of any one of the a-phase, b-phase, and c-phase currents remains increased. At the moment when a short-circuit fault occurs between the c phase and the a phase, the current amplitudes of the a phase current, the b phase current, and the c phase current increase. As a result, the current amplitude of any one of the a-phase, b-phase, and c-phase currents remains increased.
However, if it is determined that a short-circuit accident has occurred when the a-phase current, the b-phase current, and the c-phase current increase, the difference between the load current and the short-circuit current must be calculated. It may not be detected.

FIG. 8 is a diagram showing an example of changes in the power factor angle when a short-circuit accident occurs in the feeder. The example shown in FIG. 8 shows simulation results of the a-phase voltage and the a-phase current when a two-phase short-circuit accident between the a-phase and the b-phase occurs under heavy load. In FIG. 8, the left side of the broken line is the power factor angle before the occurrence of the short circuit (steady state), and the right side of the broken line is the power factor angle after the occurrence of the short circuit (short circuit state).
According to FIG. 8, it can be seen that the power factor angle changes when a short-circuit fault occurs between the a-phase and the b-phase. Therefore, when the power factor angle changes, it can be determined that a short-circuit accident has occurred.
Here, the case where the power factor angle changes when a short-circuit fault occurs between the a-phase and the b-phase is shown. The same applies to the case where a short-circuit accident occurs between the phase and the a-phase. That is, when a short-circuit accident occurs between the b-phase and the c-phase, the power factor angle changes. When a short-circuit accident occurs between the c-phase and the a-phase, the power factor angle changes.
However, if it is determined that a short-circuit accident has occurred when the power factor angle has changed, there is a risk that the accuracy of the detected phase will be poor when the load is light because the change in phase is small.
According to FIGS. 6 to 8, it is possible to determine whether or not a short-circuit fault has occurred based on changes in the voltage between phases, and whether a short-circuit fault has occurred can be determined based on changes in the phase currents and changes in the power factor angle. It can be seen that the feeder F can be identified. In other words, it can be determined that a short-circuit accident has occurred when a drop in interphase voltage is detected. Further, by identifying the feeder F in which an increase in the a-phase, the b-phase, and the c-phase phase current is detected and a change in the power factor angle is detected, a short-circuit fault is detected. can be specified.

FIG. 9 is a diagram showing a comparative example of interphase voltages, phase currents, and power factor angles before and after a two-phase short circuit and a three-phase short circuit.
FIG. 9 shows phase-to-phase voltage (voltage [V]), phase current (current [A]), and power factor angle (power factor angle [°]) for each of light load and heavy load. is shown. Specifically, regarding the interphase voltage (voltage [V]), the interphase voltage before the short circuit (before), the interphase voltage after the short circuit (after), and the amount of change in the interphase voltage before and after the short circuit ( change). Regarding the phase current (current [A]), the phase current before the short circuit (before), the phase current after the short circuit (after), and the amount of change (change) in the phase current before and after the short circuit. shown. Regarding the power factor angle (power factor angle [°]), the power factor angle before the short circuit (before), the power factor angle after the short circuit (after), and the power factor angle before and after the short circuit. The amount of change (change) is indicated.
According to FIG. 9, regarding the phase-to-phase voltage, the change in the phase-to-phase voltage before and after the short circuit is smaller for the light load than for the heavy load. It can be seen that the amount of change in interphase voltage before and after the accident is small.
Regarding phase currents, the amount of change in phase current before and after a short circuit is smaller for heavy loads than for light loads. It can be seen that the amount of change in is slightly small.
Regarding the power factor angle, the amount of change in power factor angle before and after a short circuit is smaller for heavy loads than for light loads. It can be seen that the amount of change in the power factor angle is small.
From the above, when a three-phase short circuit occurs under heavy load, the amount of change in the interphase voltage, the amount of change in the phase current, and the amount of change in the power factor angle before and after the short circuit are small. is difficult.
The short-circuit monitoring device 100 included in the power system 1 will be described below.

(Short circuit monitoring device 100)
FIG. 10 is a diagram illustrating an example of a short-circuit monitoring device according to the embodiment; The short-circuit monitoring device 100 is implemented by a device such as a personal computer, server, or industrial computer. The short-circuit monitoring device 100 includes a communication unit 105, a storage unit 110, an information processing unit 130, and buses such as an address bus and a data bus for electrically connecting each component as shown in FIG. line 150;
Communication unit 105 is realized by a communication module. Specifically, the communication unit 105 is configured by a device that performs wired communication. A communication unit 105 communicates with external devices such as the OCR 30 and the voltage sensor 50 . Specifically, the communication unit 105 receives information indicating the voltage superimposed on the bus B by the voltage sensor 50 from the feeder F, and outputs information indicating the received voltage to the information processing unit 130 . Further, the communication unit 105 receives the information indicating the current output from the OCR 30 and the information indicating the power factor angle, and transmits the received information indicating the current and the information indicating the power factor angle to the information processing unit 130. Output. Further, the communication unit 105 acquires the short-circuit accident occurrence notification output by the information processing unit 130 and transmits the acquired short-circuit accident occurrence notification to the OCR 30 .
Also, the communication unit 105 may be configured by a wireless device that performs wireless communication using a wireless communication technology such as Wi-Fi (registered trademark). The communication unit 105 may wirelessly communicate with the voltage sensor 50 and the OCR 30 .

The storage unit 110 is implemented by, for example, a RAM (Random Access Memory), ROM (Read Only Memory), HDD (Hard Disk Drive), flash memory, or a hybrid storage device in which a plurality of these are combined. Storage unit 110 stores program 111 executed by information processing unit 130 and application 112 .
The program 111 is, for example, an operating system, which is located between a user or application program and hardware, provides a standard interface to the user or application program, and at the same time, efficiently manages each resource such as hardware. management.
The application 112 causes the short circuit monitoring device 100 to receive the information indicating the voltage transmitted by the voltage sensor 50 . Application 112 receives information indicating the voltage received by short-circuit monitoring device 100 . The application 112 causes the short-circuit monitoring device 100 to derive the amount of voltage change based on the received information indicating the voltage. The application 112 causes the short-circuit monitoring device 100 to determine whether or not a short-circuit accident has occurred based on the derived information indicating the amount of change in voltage.
The application 112 causes the short-circuit monitoring device 100 to receive information indicating the current flowing through the feeder F and information indicating the power factor angle of the feeder F. FIG. The application 112 causes the short-circuit monitoring device 100 to derive the current change amount based on the received information indicating the current. The application 112 causes the short-circuit monitoring device 100 to derive the amount of change in the power factor angle based on the received information indicating the power factor angle.
The application 112 determines whether or not the feeder F is short-circuited based on the derived information indicating the amount of change in the current and the derived information indicating the amount of change in the power factor angle. Let The application 112 outputs information indicating that a short-circuit has occurred when the short-circuit monitoring device 100 determines that a short-circuit has occurred based on the determination result of whether or not the feeder F is short-circuited. and causes a short-circuit occurrence notification addressed to the OCR 30 to be created and causes the created short-circuit occurrence notification to be transmitted.

All or part of the information processing unit 130 is, for example, a functional unit (hereinafter referred to as software function unit). Note that all or part of the information processing unit 130 may be realized by hardware such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), or FPGA (Field-Programmable Gate Array). It may be realized by a combination of units and hardware.
The information processing unit 130 functions as, for example, a reception unit 131 , a voltage change amount derivation unit 132 , a current change amount derivation unit 133 , a power factor angle change amount derivation unit 134 , and a determination unit 135 .

The receiving unit 131 acquires the information indicating the voltage output by the communication unit 105 and receives the acquired information indicating the voltage. Reception unit 131 outputs information indicating the received voltage to voltage change amount derivation unit 132 .
The reception unit 131 acquires the information indicating the current and the information indicating the power factor angle output by the communication unit 105, and receives the obtained information indicating the current and the information indicating the power factor angle. Reception unit 131 outputs information indicating the received current to current change amount derivation unit 133 . Reception unit 131 outputs information indicating the received power factor angle to power factor angle change amount derivation unit 134 .
The voltage change amount deriving unit 132 acquires the information indicating the voltage output by the receiving unit 131, and based on the obtained information indicating the voltage V2 and the information indicating the voltage V1 obtained before the information indicating the voltage V2. to derive the amount of voltage change ΔV (V2−V1). For example, information indicating the voltage is output from the reception unit 131 to the voltage change amount derivation unit 132 at a predetermined cycle such as 0.1 s. The voltage change amount derivation unit 132 outputs information indicating the derived voltage change amount ΔV to the determination unit 135 .

The current change amount deriving unit 133 acquires the information indicating the current output by the receiving unit 131, and based on the obtained information indicating the current I2 and the information indicating the current I1 obtained before the information indicating the current I2. to derive the change amount ΔI of the current. For example, information indicating the current is output from the receiving unit 131 to the current change amount deriving unit 133 at a predetermined cycle such as 0.1 s. Specifically, current change amount derivation unit 133 normalizes current I2 and derives normalized current I2rms, which is the normalized current. The current change amount derivation unit 133 normalizes the current I1 and derives a normalized current I1rms, which is the normalized current. Current change amount derivation unit 133 derives difference ΔIrms (I2rms−I1rms) between normalized current I2rms and normalized current I1rms. The current change amount derivation unit 133 derives the current change amount ΔI by dividing the derived difference ΔIrms by the current limit value IL of the PCS 14a. That is, the current change amount deriving unit 133 derives the current change amount ΔI from the equation (1).

ΔI=ΔIrms/IL (1)

Current change amount derivation unit 133 outputs information indicating the derived current change amount ΔI to determination unit 135 .
The power factor angle change amount deriving unit 134 acquires the information indicating the power factor angle output by the receiving unit 131, and the information indicating the acquired power factor angle θ2 and the information indicating the power factor angle θ2 acquired before the information indicating the power factor angle θ2. Based on the information indicating the power factor angle θ1, the amount of change Δsin θ in the power factor angle is derived. For example, information indicating the power factor angle is output from the reception unit 131 to the power factor angle change amount derivation unit 134 at a predetermined cycle such as 0.1 s. Specifically, the power factor angle change amount deriving unit 134 derives the power factor angle change amount Δsin θ from Equation (2).
Δsin θ=sin θ2−sin θ1 (2)
The power factor angle change amount derivation unit 134 outputs information indicating the derived change amount Δsin θ of the power factor angle to the determination unit 135 .

The determination unit 135 acquires information indicating the voltage change amount ΔV output by the voltage change amount deriving unit 132 . The determination unit 135 acquires information indicating the amount of change ΔI in the current output by the current change amount deriving unit 133 . The determination unit 135 acquires information indicating the power factor angle change amount Δsin θ output by the power factor angle change amount deriving unit 134 .
The determination unit 135 determines whether or not a short-circuit accident has occurred based on the acquired information indicating the amount of change ΔV in voltage. Specifically, the determination unit 135 determines whether or not the voltage change amount ΔV satisfies Expression (4). Determination unit 135 determines that a short-circuit accident has occurred when the amount of change ΔV in voltage satisfies expression (4), and determines that a short-circuit accident has not occurred when expression (4) is not satisfied. judge.

ΔV>threshold α (4)

Here, the threshold α is a value obtained by decreasing the rated voltage by a predetermined percentage. For example, the threshold α may be a value that is 25% lower than the rated voltage.

The determination unit 135 determines whether or not a short-circuit accident has occurred in the feeder F based on the acquired information indicating the amount of change ΔI in the current and the information indicating the amount of change Δsin θ in the power factor angle. Specifically, the determination unit 135 determines whether or not the sum of the current change amount ΔI and the result of multiplying the weighting coefficient k by the power factor angle change amount Δsin θ is less than the threshold value β. That is, the determination unit 135 determines whether or not Expression (5) is satisfied.

ΔI+k×Δsin θ>threshold β (5)

The determination unit 135 determines that a short-circuit accident has occurred in the feeder F in which the short-circuit monitoring device 100 is installed when the formula (5) is satisfied, and determines that the feeder F has a short circuit accident when the formula (5) is not satisfied. It is determined that a short-circuit accident has not occurred in F.
Here, the threshold value β will be explained. The threshold β is derived based on actual measurements.
FIG. 11 is a diagram showing an example of the relationship between the load current and the sum of the rate of change. Here, the sum of change rates is the calculation result of ΔI+k×Δsin θ shown in Equation (5).
FIG. 11 shows two relationships between the load current [A] and the sum of the rates of change (hereinafter referred to as "feeder A" and "feeder B") when no short-circuit fault has occurred. Furthermore, FIG. 11 shows the relationship between the sum of the load current and the rate of change when a two-phase short circuit occurs between the a phase and the b phase (hereinafter referred to as “two-phase short circuit (between a and b)”), and the three-phase 3 shows the relationship between the sum of the load current and the rate of change when a short circuit occurs (hereinafter referred to as "three-phase short circuit").
In the relationship between the load current and the sum of the rate of change when no short-circuit fault has occurred, feeder A shows a case where a DG (diesel generator) is connected to bus B and the DG supplies power, and feeder B indicates the case where the storage battery 12a connected to the bus B supplies electric power. Feeder A and feeder B are obtained from actual measurements. For example, it can be obtained from actual measurements for about six months to one year. In other words, feeder A and feeder B show steady-state variations.
According to FIG. 11, it can be seen that the sum of the rate of change indicated by the two-phase short circuit (between a and b) and the three-phase short circuit is greater than the sum of the rate of change indicated by feeder A and feeder B. . In other words, the sum of the rates of change increases due to the occurrence of a short-circuit accident.
It can also be seen that the sum of the rates of change exhibited by the three-phase short is smaller than the sum of the rates of variation exhibited by the two-phase short (between a and b).
Therefore, in the present embodiment, the threshold β is set to be larger than the sum of the change rates indicated by the feeders A and B and smaller than the sum of the change rates indicated by the three-phase short circuit. In this embodiment, as an example, as shown in FIG. 11, a straight line passing through two points (0, 0.5) and (154, 0) sets the threshold value β. When the load current is "I", the threshold β is expressed as β=-0.003I+0.5.
Although the case where the threshold β is set by a straight line passing through two points (0, 0.5) and (154, 0) has been described here, the present invention is not limited to this example. For example, a straight line passing through two points (0,0.5) and (0,120) may be used to set the threshold β, or two points (0,1) and (0,154) may be set. A straight line passing through the points may be used to set the threshold value β. In other words, a straight line that is greater than the sum of the rate of change indicated by feeder A and feeder B and less than the sum of rate of change indicated by the three-phase short circuit is acceptable. Also, the threshold value β may be changed when a predetermined condition is established.

Here, the weighting factor k will be explained.
FIG. 12 is a diagram showing an example of the relationship between load current and rate of change.
FIG. 12 shows the relationship between the load current [A] and the change rate of the current change amount ΔI when a two-phase short circuit occurs (hereinafter referred to as “ΔI (two-phase short circuit)”), and the relationship when a two-phase short circuit occurs. 2 shows the relationship between the load current [A] and the rate of change of the power factor angle change amount Δsin θ (hereinafter referred to as “Δsin θ (two-phase short circuit)”).
Furthermore, FIG. 12 shows the relationship between the load current [A] and the change rate of the current change amount ΔI when a three-phase short circuit occurs (hereinafter referred to as “ΔI (three-phase short circuit)”), and the three-phase short circuit. The relationship between the load current [A] and the rate of change of the power factor angle change amount Δsin θ (hereinafter referred to as “Δsin θ (three-phase short-circuit)”) is shown.
When no short-circuit fault occurs, it is assumed that both the rate of change of the current change amount ΔI and the change rate of the power factor angle change amount Δsin θ are substantially zero with respect to the load current [A].
According to FIG. 12, ΔI (two-phase short circuit), Δsin θ (two-phase short circuit), ΔI (three-phase short circuit), and Δsin θ (three-phase short circuit) are , the rate of change is large. In other words, the rate of change increases due to the occurrence of a short-circuit accident.
According to FIG. 12, the change indicated by ΔI (three-phase short) and Δsin θ (three-phase short) compared to the rate of change indicated by ΔI (two-phase short) and Δsin θ (two-phase short) It can be seen that the rate is small.
Therefore, in the present embodiment, the weighting coefficient k set. In this embodiment, as an example, as shown in FIG. 12, a value obtained by dividing the slope of ΔI (three-phase short circuit) by the slope of Δsin (three-phase short circuit) is set as the weighting coefficient k. That is, the weighting factor k is derived based on the three-phase short circuit. Returning to FIG. 10, the description continues.
The determination unit 135 determines that a short-circuit accident has occurred when the condition shown in the above-described formula (4) is satisfied. When determining that a short-circuit accident has occurred, the determining unit 135 determines whether or not the condition shown in Expression (5) is satisfied. , it is determined that a short-circuit accident has occurred. When determining that a short-circuit accident has occurred, the determination unit 135 creates a short-circuit accident occurrence notification including information indicating that a short-circuit accident has occurred, addressed to the OCR 30, and transmits the created short-circuit accident occurrence notification. Output to unit 105 .

(Operation of short-circuit monitoring system)
FIG. 13 is a sequence chart showing an example of the operation of the short circuit monitoring system of the embodiment.
(Step S1)
Voltage sensor 50 measures the voltage on bus B.
(Step S2)
The voltage sensor 50 transmits information indicating the measured voltage of the bus B to the short-circuit monitoring device 100 .
(Step S3)
The communication unit 105 of the short-circuit monitoring device 100 receives the information indicating the voltage transmitted by the voltage sensor 50 and outputs the received information indicating the voltage to the information processing unit 130 .
(Step S4)
OCR 30 measures the current through feeder F and the power factor angle.
(Step S5)
The OCR 30 transmits information indicating the measured current and information indicating the power factor angle to the short circuit monitoring device 100 .

(Step S6)
The communication unit 105 of the short-circuit monitoring device 100 receives the information indicating the current and the information indicating the power factor angle transmitted by the OCR 30, and processes the received information indicating the current and the information indicating the power factor angle. Output to unit 130 .
(Step S7)
The receiving unit 131 of the short-circuit monitoring device 100 acquires the voltage measurement result output by the communication unit 105 and receives the acquired voltage measurement result. Reception unit 131 outputs the received voltage measurement result to voltage change amount derivation unit 132 .
The voltage change amount deriving unit 132 acquires the information indicating the voltage output by the receiving unit 131, and based on the obtained information indicating the voltage V2 and the information indicating the voltage V1 obtained before the information indicating the voltage V2. to derive the amount of voltage change ΔV. The voltage change amount derivation unit 132 outputs information indicating the derived voltage change amount ΔV to the determination unit 135 .
(Step S8)
The reception unit 131 of the short-circuit monitoring device 100 acquires the information indicating the current and the information indicating the power factor angle output by the communication unit 105, and receives the obtained information indicating the current and the information indicating the power factor angle. . Reception unit 131 outputs information indicating the received current to current change amount derivation unit 133 .
The current change amount deriving unit 133 acquires the information indicating the current output by the receiving unit 131, and based on the obtained information indicating the current I2 and the information indicating the current I1 obtained before the information indicating the current I2. to derive the change amount ΔI of the current. Current change amount derivation unit 133 outputs information indicating the derived current change amount ΔI to determination unit 135 .
(Step S9)
Reception unit 131 of short-circuit monitoring device 100 outputs information indicating the received power factor angle to power factor angle change amount derivation unit 134 .
The power factor angle change amount deriving unit 134 acquires the information indicating the power factor angle output by the receiving unit 131, and the information indicating the acquired power factor angle θ2 and the information indicating the power factor angle θ2 acquired before the information indicating the power factor angle θ2. Based on the information indicating the power factor angle θ1, the amount of change Δsin θ in the power factor angle is derived. The power factor angle change amount derivation unit 134 outputs information indicating the derived change amount Δsin θ of the power factor angle to the determination unit 135 .

(Step S10)
The determination unit 135 acquires information indicating the voltage change amount ΔV output by the voltage change amount derivation unit 132 . The determination unit 135 acquires information indicating the amount of change ΔI in the current output by the current change amount derivation unit 133 . The determination unit 135 acquires information indicating the power factor angle change amount Δsin θ output by the power factor angle change amount deriving unit 134 .
The determination unit 135 determines whether or not a short-circuit accident has occurred based on the acquired information indicating the amount of change ΔV in voltage.
The determination unit 135 determines whether or not a short-circuit accident has occurred in the feeder F based on the acquired information indicating the amount of change ΔI in the current and the information indicating the amount of change Δsin θ in the power factor angle.
Determination unit 135 determines that a short-circuit accident has occurred based on information indicating the amount of change ΔV in voltage, and based on information indicating amount ΔI of change in current and information indicating amount Δsin θ of change in power factor angle. When it is determined that a short-circuit accident has occurred in the feeder F, a short-circuit accident occurrence notification including information indicating that a short-circuit accident has occurred is created and addressed to the OCR 30, and the created short-circuit accident occurrence notification is sent to Output to the communication unit 105 .
(Step S11)
The communication unit 105 acquires the short-circuit accident occurrence notification output by the information processing unit 130 and transmits the acquired short-circuit accident occurrence notification to the OCR 30 .
(Step S12)
The OCR 30 receives the notification of occurrence of a short-circuit accident transmitted by the short-circuit monitoring device 100 .
(Step S13)
The OCR 30 operates the circuit breaker based on information indicating that a short-circuit accident has occurred, which is included in the received notification of the occurrence of a short-circuit accident.

In the above-described embodiment, as an example of an off-grid system, a case in which a solar battery and a storage battery are used as the main power sources of the system has been described, but this is not the only option. For example, wind power generation and a storage battery may be used as the main power sources of the system, geothermal power generation and a storage battery may be used as the main power sources of the system, hydroelectric power generation and a storage battery may be used as the main power sources of the system, Biomass power generation and a storage battery may be used as the main power source of the system. Further, the number of main power supply systems is not limited to two, and may be three or more.
In the above-described embodiment, the case where the short-circuit monitoring device 100 is attached to the OCR 30 has been described, but this is not the only option. For example, the short-circuit monitoring device 100 may be connected to the feeder F without being attached to the OCR 30 . In this case, the short-circuit monitoring device 100 outputs information indicating the current and information indicating the power factor angle to the feeder F, and the OCR 30 outputs information indicating the current output by the short-circuit monitoring device 100 to the feeder F and power receive information indicative of the index angle;
In the above-described embodiment, the case where one feeder F is connected to the bus B has been described, but this is not the only option. For example, a plurality of feeders F may be connected to the bus B.
In the above-described embodiment, the feeder F is connected to the sensor built-in automatic switch remote controller 40-1, the sensor built-in automatic switch remote controller 40-2, and the sensor built-in automatic switch remote controller 40-3. This is not the case. For example, the number of remote controllers for sensor built-in automatic switches connected to the feeder F may be 1-2, or may be 4 or more.
In the above-described embodiment, when the short-circuit monitoring device 100 determines that a short-circuit has occurred based on the information indicating the voltage, the short-circuit fault is detected based on the information indicating the current and the information indicating the power factor angle. Although the case of identifying the feeder F in which the error has occurred has been described, the present invention is not limited to this example. For example, the short-circuit monitoring device 100 does not determine whether a short-circuit has occurred based on the information indicating the voltage, but based on the information indicating the current and the information indicating the power factor angle. You may specify the feeder F which generate|occur|produced. By configuring in this way, the process of measuring the bus voltage can be omitted.
In the above-described embodiment, the case where the rated value of the high voltage is 3.3 kV has been described, but the present invention is not limited to this example. For example, it can be applied when the rated value of the high voltage is 6.6 kV.

According to the short-circuit monitoring device 100 of the present embodiment, in a system configuration in which the storage battery 12a and the solar cell 12b are the main power sources, for example, in an off-grid configuration, in addition to current changes occurring in the power system, voltage changes and power factor angles By paying attention to the change in , it is possible to distinguish between the load current and the short-circuit current when a short-circuit accident occurs. Therefore, it is possible to identify the distribution line in which the short-circuit accident has occurred, which contributes to reliable short-circuit protection. Conventionally, in an off-grid system, which is a power system that does not have a rotating machine power supply such as a diesel generator, the short-circuit current is small, so it is difficult to detect short-circuit accidents with the conventional protection cooperation logic that detects short-circuits based on current changes. there were.

<Configuration example>
As one configuration example, in an off-grid system, a short-circuit monitoring device for monitoring a short circuit in a distribution line that supplies electricity output by a power conditioner attached to a storage battery to a load, wherein information indicating the current flowing in the distribution line; A receiving unit that receives information indicating a power factor angle of a distribution line, a current change amount derivation unit that derives a current change amount based on the information indicating the current received by the receiving unit, and a power factor angle received by the receiving unit A power factor angle change amount derivation unit for deriving the amount of change in the power factor angle based on the information indicating the information indicating the amount of change in the current derived by the current change amount derivation unit, and the power factor angle change amount derivation unit and a determination unit that determines whether or not the distribution line is short-circuited based on the derived information indicating the amount of change in the power factor angle.
As one configuration example, the determination unit divides the normalized value of the current change amount by the current limit value output by the power conditioner, and the sum of the value obtained by multiplying the change amount of the power factor angle by a weighting factor. is greater than the change rate threshold, it is determined that the distribution line is short-circuited.
As an example configuration, the weighting factors are derived based on a three-phase short circuit.
As one configuration example, the change rate threshold is derived based on past actual measurement data.
As one configuration example, the reception unit receives information indicating a bus voltage, which is a voltage flowing in a bus to which the distribution line is connected, and the short-circuit monitoring device receives the bus voltage based on the information indicating the bus voltage received by the reception unit. A voltage change amount derivation unit for deriving a voltage change amount is provided, and the determination unit determines whether or not the distribution line is short-circuited based on the information indicating the bus voltage change amount derived by the voltage change amount derivation unit. do.

Although the embodiments have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention. These embodiments are included in the scope and gist of the invention, and at the same time, are included in the scope of the invention described in the claims and equivalents thereof.
Note that the above-described short-circuit monitoring device 100 may be realized by a computer. In that case, a program for realizing the function of each functional block is recorded in a computer-readable recording medium. The program recorded on this recording medium may be loaded into the computer system and executed by the CPU. The "computer system" here includes hardware such as an OS (Operating System) and peripheral devices.
A "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM. A "computer-readable recording medium" includes a storage device such as a hard disk built into a computer system.

Furthermore, the "computer-readable recording medium" may include those that dynamically retain the program for a short period of time. For a short period of time, a program is dynamically stored in a communication line for transmitting a program via a network such as the Internet or a communication line such as a telephone line.
In addition, the "computer-readable recording medium" may also include a medium that retains the program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client. Further, the program may be for realizing part of the functions described above. Moreover, the above program may be one capable of realizing the functions described above in combination with a program already recorded in a computer system. Moreover, the program may be implemented using a programmable logic device. A programmable logic device is, for example, an FPGA (Field Programmable Gate Array).

Note that the short-circuit monitoring device 100 described above has a computer therein. Each process of the short-circuit monitoring device 100 described above is stored in a computer-readable recording medium in the form of a program, and the above process is performed by reading and executing this program by a computer.
Here, the computer-readable recording medium includes a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, and the like. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer receiving the distribution may execute the program.
Further, the program may be for realizing part of the functions described above.
Further, it may be a so-called difference file (difference program) that can realize the above-described functions in combination with a program already recorded in the computer system.

Reference Signs List 1 power system 10a voltage source 10b current source 12a storage battery 12b solar cell 14a, 14b PCS 20a, 20b transformer 30 OCR 40-1, 40-2, 40 -3...Remote controller for automatic switch with built-in sensor, 50...Voltage sensor, 100...Short-circuit monitoring device, 105...Communication unit, 110...Storage unit, 111...Program, 112...Application, 130...Information processing unit, 131...Reception Part 132... Voltage change amount derivation part 133... Current change amount derivation part 134... Power factor angle change amount derivation part 135... Judgment part

Claims (7)

In an off-grid system, a short circuit monitoring device for monitoring a short circuit in a distribution line that supplies electricity output by a power conditioner attached to a storage battery to a load,
a reception unit that receives information indicating a current flowing through a distribution line and information indicating a power factor angle of the distribution line;
a current change amount deriving unit for deriving a change amount of the current based on the information indicating the current received by the receiving unit;
a power factor angle change amount deriving unit that derives the amount of change in the power factor angle based on the information indicating the power factor angle received by the receiving unit;
The distribution line based on information indicating the amount of change in the current derived by the current change amount deriving unit and information indicating the amount of change in the power factor angle derived by the power factor angle change amount deriving unit. A short-circuit monitoring device comprising: a determination unit that determines whether or not is short-circuited. The determination unit determines a value obtained by dividing a normalized value of the amount of change in the current by a limit value of the current output from the power conditioner, and a value obtained by multiplying the amount of change in the power factor angle by a weighting factor. 2. A short circuit monitor according to claim 1, wherein said distribution line is determined to be short-circuited when the sum is greater than a change rate threshold. 3. The short circuit monitor of claim 2, wherein the weighting factors are derived based on three-phase short circuits. 4. The short-circuit monitoring device according to claim 2, wherein said change rate threshold value is derived based on past actual measurement data. The reception unit receives information indicating a bus voltage, which is a voltage flowing in a bus to which the distribution line is connected,
The short circuit monitoring device
a voltage change amount deriving unit for deriving the amount of change in the bus voltage based on the information indicating the bus voltage received by the receiving unit;
The determining unit determines whether or not the distribution line is short-circuited based on the information indicating the amount of change in the bus voltage derived by the voltage change amount deriving unit. A short circuit monitor according to any one of the preceding claims. In an off-grid system, a short-circuit monitoring method executed by a short-circuit monitoring device that monitors a short-circuit in a distribution line that supplies electricity output by a power conditioner attached to a storage battery to a load,
receiving information indicating a current flowing in a distribution line and information indicating a power factor angle of the distribution line;
deriving an amount of change in the current based on the information indicating the current received in the receiving step;
deriving an amount of change in the power factor angle based on the information indicating the power factor angle received in the receiving step;
determining whether or not the distribution line is short-circuited based on information indicating the amount of change in the current and information indicating the amount of change in the power factor angle. In the off-grid system, the computer of the short circuit monitoring device that monitors the short circuit of the distribution line that supplies the electricity output by the power conditioner attached to the storage battery to the load,
receiving information indicating a current flowing in a distribution line and information indicating a power factor angle of the distribution line;
deriving an amount of change in the current based on the information indicating the current received in the receiving step;
deriving an amount of change in the power factor angle based on the information indicating the power factor angle received in the receiving step;
determining whether or not the distribution line is short-circuited based on information indicating the amount of change in the current and information indicating the amount of change in the power factor angle.

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