JP7678745B2 - Under-frequency relays and power systems - Google Patents

Description

The present invention relates to an under-frequency relay and a power system.

The importance of strengthening the resilience of power grids has been reaffirmed in the wake of large-scale power outages caused by natural disasters in recent years. Meanwhile, with growing demands for decarbonization, there are hopes that renewable energy sources will become the main source of power. As is well known, renewable energy sources are sources that undermine the inertia of power grids, and when renewable energy sources are connected to power grids, the stability of the power grid frequency decreases.

Non-Patent Document 1 discloses a method for adjusting an under-frequency relay as a power frequency stabilization technology that takes into account various system conditions such as renewable energy power sources. This under-frequency relay is a circuit breaker that disconnects the load from the power system when the power frequency drops significantly due to a large-scale power source loss, etc., and restores the power frequency of the power system to its original frequency.

On the other hand, IEC 61850 is an international standard that defines the communication protocols for intelligent equipment in substations. IEC 61850 is a technical standard compiled by the Technical Committee of the International Electrotechnical Commission, and specifies communication protocols that correspond to the type of intelligent equipment.

Turaj. Amraee, Mohammad. Ghaderi. Darebaghi, Alireza. Soroudi and Andrew. Keane, "Probabilistic Under Frequency Load Shedding Considering RoCoF Relays of Distributed Generators," in IEEE Transactions on Power Systems, vol. 33, no. 4, pp. 3587-3598 (2018).

However, at present, no under-frequency relays that comply with IEC 61850 have been developed. Considering that renewable energy sources will increasingly become the main power source in the future, it is necessary to develop under-frequency relays that comply with IEC 61850 as soon as possible to increase the versatility of under-frequency relays. It is expected that increasing the versatility of under-frequency relays will further promote the use of renewable energy sources as the main power source.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an under-frequency relay and power system that comply with IEC 61850.

To achieve the above objective, the present invention employs, as a first solution for the under-frequency relay, a means for disconnecting a lower system from a higher system by receiving a request signal conforming to the IEC 61850 communication protocol from a system control device.

The present invention employs, as a second solution relating to the frequency down relay, a means in which the first solution described above is provided with an information model unit that stores modeling information that models the functions of non-controlled devices among the various devices that make up the lower system and the upper system, and the functions of the device's own high-performance electronic device, based on the provisions of IEC 61850.

The present invention adopts a third solution related to the under-frequency relay, which is the second solution described above, in which the modeling information includes an islanding function modeling section that governs the disconnection of the lower system and a setting value that is the disconnection threshold.

The present invention employs a fourth solution related to the under-frequency relay, which is any one of the first to third solutions described above, in which the lower system is equipped with a renewable energy power source.

The present invention employs a fifth solution for a frequency down relay, which is any of the first to fourth solutions described above, in which the relay is composed of a relay main body and a high-performance electronic device that communicate with each other in accordance with the communication protocol.

In the present invention, as a solution for the power system, a frequency down relay according to any one of the first to fifth solutions is provided between the lower system and the upper system.

The present invention makes it possible to provide an under-frequency relay and power system that comply with IEC 61850.

1 is a system diagram showing a configuration of a power system in one embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a frequency down-relay according to an embodiment of the present invention. 1 is a block diagram showing a configuration of a system control device according to an embodiment of the present invention; FIG. 2 is a schematic diagram showing a communication procedure between a power system control device and a frequency down relay in an embodiment of the present invention. FIG. 13 is a block diagram illustrating a variation of a frequency down-regulation relay according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of an information model unit of a frequency down-relay according to an embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the power system A in this embodiment will be described. This power system A is a power system for supplying power to the power receiving equipment of a consumer, and integrates power generation, power transformation, power transmission, and power distribution. The power system A is operated and managed by a specific power utility, but generally, renewable energy sources operated and managed by a power utility different from the specific power utility are interconnected.

As shown in Figure 1, such a power system A includes a main system 1, two transformers 2a, 2b, two first busbars 3a, 3b, six load feeders 4a to 4f, six under-frequency relays 5a to 5f, six lower systems 6a to 6f, and a system control device 7. Of these components, the main system 1, the two transformers 2a, 2b, and the two first busbars 3a, 3b constitute the upper system of the present invention.

Of these components, the components other than the six lower systems 6a to 6f are managed and operated by a specific power utility that primarily manages and operates power system A. In contrast, the six lower systems 6a to 6f are primarily managed and operated by a power utility other than this specific power utility.

The main system 1 is made up of power plants and power transmission and distribution networks that are exclusively operated and managed by the electric power utility, and is the main component of the electric power system A. This main system 1 includes electrical facilities traditionally known as power plants, such as thermal power plants, hydroelectric power plants, and nuclear power plants. This main system 1 has traditionally been operated and managed by former general electric utilities (i.e. specific electric power utility companies) that have traditionally operated electric power businesses throughout the country.

The two transformers 2a and 2b are provided between the main system 1 and the first busbars 3a and 3b. That is, one input/output terminal of the transformer 2a is connected to the main system 1, and the other input/output terminal is connected to one of the first busbars 3a. The other transformer 2b has one input/output terminal connected to the main system 1, and the other input/output terminal connected to the other of the first busbars 3b. Such transformers 2a and 2b are power devices that convert the voltage of the power transmitted and received between the main system 1 and the first busbars 3a and 3b.

In general, the voltage (main system voltage) of the power (main system power) of the main system 1 is higher than the voltage (first system voltage) of the power (first system power) of the first busbars 3a, 3b. When the flow of system power is from the main system 1 to the first busbars 3a, 3b, each transformer 2a, 2b steps down the main system voltage of the main system power and converts it to the first voltage. On the other hand, when the flow of system power is from the first busbars 3a, 3b to the main system 1, each transformer 2a, 2b steps up the first system voltage of the first system power and converts it to the main system voltage.

The two first busbars 3a, 3b are electric wires provided corresponding to the two transformers 2a, 2b. That is, one first busbar 3a is connected to the other input/output terminal of one transformer 2a, and the other first busbar 3b is connected to the other input/output terminal of the other transformer 2b. Such first busbars 3a, 3b aggregate the six load feeders 4a to 4f into two systems corresponding to the two transformers 2a, 2b.

The six load feeders 4a to 4f are distribution lines (connection lines) for connecting the six sub-systems 6a to 6f to the main system 1 via the transformers 2a, 2b and the first busbars 3a, 3b, and are provided corresponding to the six sub-systems 6a to 6f. That is, the first load feeder 4a is provided corresponding to the first sub-system 6a, with one end connected to one of the first busbars 3a and the other end connected to the first sub-system 6a.

The second load feeder 4b is provided in correspondence with the second sub-system 6b, with one end connected to one of the first busbars 3a and the other end connected to the second sub-system 6b. The third load feeder 4c is provided in correspondence with the third sub-system 6c, with one end connected to one of the first busbars 3a and the other end connected to the third sub-system 6c.

The fourth load feeder 4d is provided in correspondence with the fourth sub-system 6d, with one end connected to one of the second busbars 3b and the other end connected to the fourth sub-system 6d. The fifth load feeder 4e is provided in correspondence with the fifth sub-system 6e, with one end connected to one of the second busbars 3b and the other end connected to the fifth sub-system 6e. The sixth load feeder 4f is provided in correspondence with the sixth sub-system 6f, with one end connected to one of the second busbars 3b and the other end connected to the sixth sub-system 6f.

The under-frequency relays 5a to 5f are digital relays conforming to IEC 61850 and are provided in the middle of the load feeders 4a to 4f corresponding to the lower systems 6a to 6f, respectively. That is, the under-frequency relays 5a to 5f are provided in the power system A between the lower systems 6a to 6f and the upper system (the main system 1, the transformers 2a and 2b, and the first busbars 3a and 3b).

The first under-frequency relay 5a is provided in the middle of the first load feeder 4a in correspondence with the first sub-system 6a. The second under-frequency relay 5b is provided in the middle of the second load feeder 4b in correspondence with the second sub-system 6b. The third under-frequency relay 5c is provided in the middle of the third load feeder 4c in correspondence with the third sub-system 6c.

The fourth down frequency relay 5d is provided in the middle of the fourth load feeder 4d in correspondence with the fourth sub-system 6d. The fifth down frequency relay 5e is provided in the middle of the fifth load feeder 4e in correspondence with the fifth sub-system 6e. The sixth down frequency relay 5f is provided in the middle of the sixth load feeder 4f in correspondence with the sixth sub-system 6f.

Each of these under-frequency relays 5a to 5f sets whether the subordinate systems 6a to 6f are connected to the first busbars 3a, 3b (i.e., connected to the main system 1) based on the system frequency of the first system power. As will be described in detail later, each of the under-frequency relays 5a to 5f has a function of detecting the rate of change (frequency change rate) of the system frequency of the first system power, and switches the connection state between one end and the other end of the load feeders 4a to 4f between a conductive state (ON state) and a non-conductive state (OFF state) based on the frequency change rate and a pre-stored set value DO.

In other words, when the rate of change of the frequency of the first system power is within the range of the set value DO, the under-frequency relays 5a to 5f set the load feeders 4a to 4f to a conductive state (ON state), thereby connecting the lower systems 6a to 6f to the upper system consisting of the main system 1, the transformers 2a and 2b, and the first busbars 3a and 3b.

On the other hand, when the rate of change of the frequency of the first system power deviates from the range of the set value DO, each of the under-frequency relays 5a to 5f controls the load feeders 4a to 4f to a non-conductive state (OFF state), thereby disconnecting the lower systems 6a to 6f from the upper system. The set value DO of each of the under-frequency relays 5a to 5f is a release threshold value that governs the release of the connection of the lower systems 6a to 6f to the upper system.

Each of these under-frequency relays 5a to 5f is also a power interruption device with an external control function. That is, in addition to autonomously switching between the conductive state (ON state) and non-conductive state (OFF state) based on the above-mentioned frequency change rate and set value DO, each of the under-frequency relays 5a to 5f controls switching between the conductive state (ON state) and non-conductive state (OFF state) based on a request signal S1 received from the system control device 7.

Although details will be described later, each of the under-frequency relays 5a to 5f has a communication function for performing two-way communication with the system control device 7 according to a communication protocol compliant with IEC 61850 (IEC 61850 communication protocol), and receives a request signal S1 generated by the system control device 7 based on the above-mentioned IEC 61850 communication protocol.

The first frequency down relay 5a controls whether the first sub-system 6a is connected to or not connected to the main system 1 based on the request signal S1 received by the above IEC communication protocol. The second frequency down relay 5b controls whether the second sub-system 6b is connected to or not connected to the main system 1 based on the request signal S1 received by the above IEC 61850 communication protocol. The third frequency down relay 5c controls whether the third sub-system 6c is connected to or not connected to the main system 1 based on the request signal S1 received by the above IEC communication protocol.

The fourth frequency down relay 5d controls whether the fourth sub-system 6d is connected to or not connected to the main system 1 based on the request signal S1 received via the IEC 61850 communication protocol. The fifth frequency down relay 5e controls whether the fifth sub-system 6e is connected to or not connected to the main system 1 based on the request signal S1 received via the IEC 61850 communication protocol. The sixth frequency down relay 5f controls whether the sixth sub-system 6f is connected to or not connected to the main system 1 based on the request signal S1 received via the IEC 61850 communication protocol.

Each of these six under-frequency relays 5a to 5f has the functional components shown in FIG. 2, namely, a circuit breaker 5g, a transformer 5h, an analog input/output unit 5i, a communication unit 5j, an information model unit 5k, an under-frequency relay calculation unit 5m, and a digital input/output unit 5n. Of these components, the analog input/output unit 5i, the communication unit 5j, the information model unit 5k, the under-frequency relay calculation unit 5m, and the digital input/output unit 5n constitute an IED (Intelligent Electronic Device) as shown in the figure. This IED has specifications that comply with the provisions of IEC 61850.

The circuit breaker 5g is provided at an intermediate location of the load feeders 4a to 4f, and turns on/off the connection between one end and the other end of the load feeders 4a to 4f based on a switching signal input from the digital input/output unit 5n. That is, in the conductive state, the circuit breaker 5g connects the lower systems 6a to 6f to the first busbars 3a, 3b (main system 1), and in the open state, the circuit breaker 5g switches the lower systems 6a to 6f to a non-connected state with respect to the first busbars 3a, 3b (main system 1).

The input end of the transformer 5h is connected to the first busbars 3a and 3b of the load feeders 4a to 4f, i.e., the upstream side of the circuit breaker 5g, and steps down the first system voltage of the load feeders 4a to 4f (i.e., the first system) and outputs it to the analog input/output unit 5i. In other words, this transformer 5h steps down the first system voltage to a voltage (measurement signal) that can be handled by an IED that complies with IEC 61850.

The analog input/output unit 5i is an interface circuit that accepts measurement signals. This analog input/output unit 5i converts the measurement signals, which are analog signals, into digital signals that can be handled by the frequency down-regulation relay calculation unit 5m, and outputs the measurement data generated by the conversion to the frequency down-regulation relay calculation unit 5m.

The communication unit 5j is a functional component that communicates with the system control device 7 in accordance with the IEC 61850 communication protocol, and receives, for example, a request signal S1 in accordance with the IEC 61850 communication protocol. The communication unit 5j outputs various requests received from the system control device 7 as the request signal S1 to the information model unit 5k or the digital input/output unit 5n.

The information model unit 5k is a storage unit that stores modeling information that models the functions of non-controlled devices among the various devices that make up the power system A and the functions of the IED based on the provisions of IEC 61850. This information model unit 5k outputs the modeling information to the under-frequency relay calculation unit 5m in response to a request from the under-frequency relay calculation unit 5m.

The modeling information includes multiple Logical Nodes/Data Objects (LN/DO) that are required to be implemented by IEC 61850, and "PFRCs" that are "Logical Nodes" defined in the IEC 61850 communication protocol for frequency rate of change relays, as described in detail below. This PFRC includes the setting value DO used in the under-frequency relay calculation unit 5m.

In the frequency reduction relay calculation unit 5m, the comparison process between the frequency change rate calculated by a different calculation method for each PFRC and the set value DO is performed simultaneously in parallel for each PFRC. The necessity to output a switching control signal is finally determined by a logical calculation of the result of the comparison process between the frequency change rate and the set value DO performed simultaneously in parallel.

The frequency down relay calculation unit 5m calculates the rate of change (frequency change rate) in the system frequency of the main system power and the first system power based on the measurement data input from the analog input/output unit 5i, and determines whether or not to switch the circuit breaker 5g from a conductive state to an open state based on the frequency change rate and the set value DO acquired from the information model unit 5k. When the frequency down relay calculation unit 5m determines that the circuit breaker 5g should be switched from a conductive state to an open state, it generates a switch request signal indicating the switch and outputs it to the digital input/output unit 5n.

The digital input/output unit 5n is an interface circuit that converts the switching control signal, which is a digital signal, into a switching signal that can drive the circuit breaker 5g. This digital input/output unit 5n generates a switching signal based on the switching control signal input from the frequency down relay calculation unit 5m or the switching request input from the communication unit 5j, and outputs the switching signal to the circuit breaker 5g to directly operate the circuit breaker 5g.

The digital input/output unit 5n also acquires a signal (switching state signal) indicating the operating state of the circuit breaker 5g from the circuit breaker 5g. The digital input/output unit 5n outputs the switching state signal to the information model unit 5k. The information model unit 5k stores the operating state of the circuit breaker 5g based on the switching state signal.

The six sub-systems 6a to 6f are power generation facilities connected to the main system 1 via the load feeders 4a to 4f, the first busbars 3a and 3b, and the transformers 2a and 2b. That is, the first sub-system 6a is connected to the main system 1 via the first load feeder 4a, one of the first busbars 3a, and one of the transformers 2a. The second sub-system 6b is connected to the main system 1 via the second load feeder 4a, one of the first busbars 3a, and one of the transformers 2a. The third sub-system 6c is connected to the main system 1 via the third load feeder 4c, one of the first busbars 3a, and one of the transformers 2a.

Furthermore, the fourth sub-system 6d is connected to the main system 1 via the fourth load feeder 4d, the other first busbar 3b, and the other converter 2b. The fifth sub-system 6e is connected to the main system 1 via the fifth load feeder 4e, the other first busbar 3b, and the other converter 2b. The sixth sub-system 6f is connected to the main system 1 via the sixth load feeder 4f, the other first busbar 3b, and the other converter 2b.

As shown in the figure, each of these lower systems 6a to 6f includes a power generation device, a PCS (Power Conditioning Subsystem), a load, and a second bus. The power generation device is a renewable energy source such as a wind power generator or a solar cell. The PCS converts the DC power generated by the power generation device into AC.

The PCS is a power conditioner connected to the second busbar, which converts the power of the renewable energy power source and the power generation device into the first system power of the first busbars 3a and 3b, and outputs it to the second busbar as lower system power. The load is connected to the second busbar, and is a power consuming device that consumes the first system power or the lower system power.

These six lower-level systems 6a to 6f output status signals S2 indicating their own power generation status to the system control device 7. That is, the PCS of the first lower-level system 6a outputs a first status signal S2 indicating the operating status of its own power generation device to the system control device 7. The PCS of the second lower-level system 6b outputs a second status signal S2 indicating the operating status of its own power generation device to the system control device 7. The PCS of the third lower-level system 6c outputs a third status signal S2 indicating the operating status of its own power generation device to the system control device 7.

The PCS of the fourth lower-level system 6d outputs a second status signal S2 indicating the operating status of its own renewable energy power source and power generation device to the system control device 7. The PCS of the fifth lower-level system 6e outputs a fifth status signal S2 indicating the operating status of its own renewable energy power source and power generation device to the system control device 7. The PCS of the sixth lower-level system 6f outputs a sixth status signal S2 indicating the operating status of its own renewable energy power source and power generation device to the system control device 7.

The system control device 7 generates a request signal S1 based on this status signal S2, and controls each of the under-frequency relays 5a to 5f by transmitting the request signal S1 to each of the under-frequency relays 5a to 5f. As will be described in detail later, the system control device 7 generates a request signal S1 that complies with the IEC communication protocol based on the status signal S2, and transmits the request signal S1 to each of the under-frequency relays 5a to 5f in a procedure that complies with the IEC communication protocol.

For example, when the system control device 7 detects based on the status signal S2 that power generation in any of the lower systems 6a to 6f has stopped or is predicting such a stop, it generates a request signal S1 to disconnect a load corresponding to the amount of power generation (loss amount) of the stopped power generation (power loss) from the main system 1. In other words, the system control device 7 maintains the system frequencies of the main system power and the first system power within the normal range by disconnecting a load with a power consumption amount equivalent to the amount of power loss from the first busbars 3a and 3b.

As shown in FIG. 3, such a system control device 7 includes a data acquisition unit 7a, a characteristic generation unit 7b, a control unit 7c, and a communication unit 7d. In addition, the control unit 7c includes a control target selection unit 7e and an adjustment unit 7f.

The data acquisition unit 7a acquires the power generation output (renewable energy output) of the renewable energy power sources in each of the lower-level systems 6a to 6f in real time based on the status signal S2. This data acquisition unit 7a calculates the total value of the power generation output of each of the lower-level systems 6a to 6f. In addition, this data acquisition unit 7a acquires the power consumed by the load of each of the lower-level systems 6a to 6f (load power) in real time based on the status signal S2.

The characteristic generating unit 7b generates a renewable energy dropout characteristic that indicates the amount of dropout of renewable energy power sources according to the frequency change rate of the system power of the power system A, based on the power generation output of each of the lower systems 6a to 6f acquired by the data acquiring unit 7a. This renewable energy dropout characteristic is a graph in which the horizontal axis indicates the frequency change rate of the system power and the vertical axis indicates the amount of dropout of renewable energy power sources, and has the characteristic that the amount of dropout increases as the frequency change rate increases, and the amount of dropout saturates when the frequency change rate reaches a certain value.

The control unit 7c generates a request signal S1 based on the renewable energy shedding characteristics generated by the characteristic generation unit 7b. That is, the control unit 7c generates the request signal S1 so as to disconnect from the main grid 1 a load power equivalent to the amount of shedding in accordance with the renewable energy shedding characteristics. Such a control unit 7c includes a control target selection unit 7e and an adjustment unit 7f.

The control target selection unit 7e selects the under-frequency relays 5a to 5f to be switched from a conductive state to a released state based on the load power of each of the lower systems 6a to 6f acquired by the data acquisition unit 7a. For example, the control target selection unit 7e selects the under-frequency relays 5a to 5f connected to the lower systems 6a to 6f that have a load power equivalent to the amount of dropout of the renewable energy power source as the control target.

The adjustment unit 7f generates a control command to adjust the set value DO of the control object selected by the control object selection unit 7e and outputs the control command to the communication unit 7d. In other words, the adjustment unit 7f controls the control object by adjusting the set value DO of the control object so that the control object is switched from a conductive state to a released state.

The communication unit 7d is a functional component that communicates with the communication unit 5j of each of the under-frequency relays 5a to 5f in accordance with the IEC 61850 communication protocol. This communication unit 7d generates a request signal S1 in accordance with the IEC 61850 communication protocol based on a control command input from the adjustment unit 7f, and transmits it to the communication unit 5j of each of the under-frequency relays 5a to 5f.

The communication unit 7d receives modeling information such as the set value DO from the communication unit 5j of each of the under-frequency relays 5a to 5f and outputs it to the adjustment unit 7f. The adjustment unit 7f generates control commands by also referring to the modeling information acquired from each of the under-frequency relays 5a to 5f. In other words, the system control device 7 acquires and rewrites the set value DO of each of the under-frequency relays 5a to 5f through two-way communication that complies with the IEC 61850 communication protocol.

Next, the operation of the power system A according to this embodiment, in particular the operation of disconnecting the lower-level systems 6a to 6f through cooperation between the system control device 7 and the frequency down relays 5a to 5f, will be described in detail with reference to FIG. 4.

Here, each of the under-frequency relays 5a to 5f autonomously switches the circuit breaker 5g from the conductive state to the open state by a judgment process based on the rate of change of the frequency of the main system power (first system power) calculated by the under-frequency relay calculation unit 5m and the set value DO pre-stored in the information model unit 5k. In other words, each of the under-frequency relays 5a to 5f disconnects each of the lower systems 6a to 6f from the main system 1 so that the system frequency of the main system power (first system power) does not become abnormal.

In addition to this autonomous operation, each of the under-frequency relays 5a to 5f switches the circuit breaker 5g from the conductive state to the open state based on various requests received from the system control device 7. In other words, each of the under-frequency relays 5a to 5f disconnects each of the subordinate systems 6a to 6f from the main system 1 under the control of the system control device 7 based on various requests that comply with the IEC 61850 communication protocol.

For example, when acquiring the preset setting value DO of each of the under-frequency relays 5a to 5f, the system control device 7 transmits a setting value acquisition request to each of the under-frequency relays 5a to 5f as shown in FIG. 4(a). This setting value acquisition request is a request signal that instructs each of the under-frequency relays 5a to 5f to transmit the setting value DO included in the modeling information of each of the under-frequency relays 5a to 5f, and is transmitted from the communication unit 7d to the communication unit 5j of each of the under-frequency relays 5a to 5f using "GetDataValues" or "Report" defined in the IEC61850 communication protocol.

When each of the under-frequency relays 5a to 5f receives the above-mentioned setting value acquisition request via the communication unit 5j, it acquires the setting value DO from the information model unit 5k and transmits a setting value report to the system control device 7. This setting value report is a signal that includes the setting value DO stored in the information model unit 5k as part of the modeling information, and is transmitted from the communication unit 5j to the communication unit 7d of the system control device 7 using the "GetDataValues response+" defined in the IEC61850 communication protocol.

When rewriting the set value DO of each under-frequency relay 5a to 5f, the system control device 7 transmits a set value rewrite request to each under-frequency relay 5a to 5f as shown in FIG. 4(b). This set value rewrite request is a request signal for rewriting the set value DO of each under-frequency relay 5a to 5f, and includes an updated value for the set value DO. The communication unit 7d of the system control device 7 transmits such a set value rewrite request to the communication unit 5j of each under-frequency relay 5a to 5f using "SetDataValues" defined in the IEC 61850 communication protocol.

When each of the frequency down relays 5a to 5f receives the above-mentioned setting value rewrite request via the communication unit 5j, it transmits a reception report to the system control device 7. This reception report notifies the system control device 7 that the setting value rewrite request has been received normally, and is transmitted from the communication unit 5j to the communication unit 7d of the system control device 7 using the "SetDataValues response+" defined in the IEC61850 communication protocol.

When the transmission of the reception report is completed, each of the frequency down relays 5a to 5f rewrites the set value DO stored in the information model unit 5k to the updated value of the setting value rewrite request. When the rewrite is completed, each of the frequency down relays 5a to 5f transmits a rewrite completion report to the system control device 7. This rewrite completion report is a signal that includes the updated value and the rewrite time, and is transmitted from the communication unit 5j to the communication unit 7d of the system control device 7 using "Report" defined in the IEC 61850 communication protocol.

Here, when the system control device 7 identifies the control target based on the state signal S2, it transmits a setting value rewrite request only to the control target, causing the information model unit 5k to rewrite the setting value DO to the updated value of the setting value rewrite request. As a result of this rewrite, the frequency down relay calculation unit 5m of the control target switches the circuit breaker 5g from the conductive state to the open state based on the frequency change rate of the main system power (first system power) and the updated value of the information model unit 5k.

Furthermore, when each of the under-frequency relays 5a to 5f is to be forcibly operated, the system control device 7 transmits a switching request to each of the under-frequency relays 5a to 5f as shown in Fig. 4(c). This switching request is a request signal for switching the circuit breaker 5g in each of the under-frequency relays 5a to 5f from a conductive state to a cut-off state, and is transmitted to the communication unit 5j of each of the under-frequency relays 5a to 5f using "Operate", "GOOSE" or "R-GOOSE" as specified in the IEC 61850 communication protocol.

Each of the frequency down relays 5a to 5f transmits a reception report to the system control device 7 only when the communication unit 5j receives the above-mentioned switching request by "Operate". This reception report notifies the system control device 7 that the switching request has been received normally, and is transmitted from the communication unit 5j to the communication unit 7d of the system control device 7 using "Operate response+" defined in the IEC 61850 communication protocol.

When the transmission of the reception report is completed, each of the down-frequency relays 5a to 5f generates a switching signal based on the switching request in the digital input/output unit 5n. Then, each of the down-frequency relays 5a to 5f outputs the switching signal to the circuit breaker 5g, thereby switching the circuit breaker 5g from a conductive state to a cut-off state.

When the switching of the circuit breaker 5g is completed, each of the under-frequency relays 5a to 5f transmits a switching completion report to the system control device 7. This switching completion report is a signal including the switching time, etc., and is transmitted from the communication unit 5j to the communication unit 7d of the system control device 7 using "Report", "GOOSE" or "R-GOOSE" defined in the IEC 61850 communication protocol.

With such power system A and under-frequency relays 5a to 5f, each under-frequency relay 5a to 5f can be controlled by communication between the system control device 7 and each under-frequency relay 5a to 5f that complies with the IEC 61850 communication protocol. Therefore, according to this embodiment, it is possible to provide under-frequency relays 5a to 5f and power system A that comply with IEC 61850.

The present invention is not limited to the above embodiment, and the following modifications are possible. For example, in the above embodiment, the IED (high performance electronic device) in each of the frequency down relays 5a to 5f is configured as a pair of devices, but the present invention is not limited to this. For example, as shown in FIG. 5, the IED (high performance electronic device) may be configured with two devices, and the same functions as the IED in the above embodiment may be realized by mutual communication between the two devices.

In the configuration example shown in FIG. 5, the under-frequency relays 5a'-5f' (relay main body) are composed of a circuit breaker 5g, a transformer 5h, and an MU including an analog input/output unit 5i, a communication unit 5j, an information model unit 5k, and a digital input/output unit 5n, and an IED 8 (high performance electronic device) including a communication unit 8a, an information model unit 8b, and a calculation unit 8c is configured as a separate device from the under-frequency relays 5a'-5f'. The communication units 5j of the under-frequency relays 5a'-5f and the communication unit 8a of the IED 8 communicate in accordance with the IEC 61850 communication protocol.

Finally, the above-mentioned information model units 5k and 8b will be further explained with reference to FIG. 6. Each of the information model units 5k and 8b includes an islanding detection active method modeling unit M1, an islanding detection passive method 1 modeling unit M2, and an islanding detection active method 2 modeling unit M3. One or more of these islanding detection active method modeling units M1, islanding detection passive method 1 modeling units M2, and islanding detection active method 2 modeling units M3 are provided in the information model units 5k and 8b.

The active islanding detection modeling unit M1 has four PFRCs 1 to 4 as shown in the figure, and performs switching control based on the comparison results between the four frequency change rates and thresholds. On the other hand, the passive islanding detection modeling unit M2 has a single PFRC 5, and the active islanding detection modeling unit M3 has a single PFRC 6.

The islanding detection passive method 1 modeling unit M2 and the islanding detection active method 2 modeling unit M3 each perform switching control based on the result of comparing one frequency change rate with a threshold value. Note that each of the PFRCs 1 to 6 constituting the information model units 5k and 8b can individually set the frequency change rate calculation method and the setting value DO.

A Power system S1 Request signal S2 Status signal 1 Main system 2a, 2b Transformer 3a, 3b First busbar 4a to 4f Load feeder 5a to 5f Under-frequency relay 5g Circuit breaker 5h Transformer 5i Analog input/output unit 5j Communication unit 5k Information model unit 5m Under-frequency relay calculation unit 5n Digital input/output unit 6a to 6f Subsystem 7 System control device 7a Data acquisition unit 7b Characteristics generation unit 7c Control unit 7d Communication unit 7e Control target selection unit 7f Adjustment unit 8 IED
8a Communication unit 8b Information model unit 8c Under-frequency relay calculation unit

Claims (4)

By receiving a request signal conforming to the IEC 61850 communication protocol from the system control device, the lower system is disconnected from the upper system ;
an information model unit that stores modeling information obtained by modeling functions of non-controllable devices among various devices constituting the lower system and the upper system and functions of its own high-performance electronic device based on the provisions of IEC 61850;
The modeling information includes an islanding function modeling unit that governs the disconnection of the lower system and a setting value that is a disconnection threshold value,
rewriting the setting value by receiving a setting value rewrite request conforming to the IEC 61850 communication protocol from the system control device;
2. An under-frequency relay comprising: The under frequency relay of claim 1 , wherein the sub-system comprises a renewable energy source. 3. The frequency downconversion relay according to claim 1, further comprising a relay body and a high-performance electronic device which communicate with each other in accordance with the communication protocol. 4. An electric power system comprising: a frequency down relay according to claim 1 between the lower system and the upper system.

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