JPH06343231A - System-interconnection protecting apparatus - Google Patents

Abstract

PURPOSE:To separate a receiving-point breaker quickly without an expensive transfer breaking device by providing a higher-harmonic power supply in each in-plant and always monitoring the higher-harmonic impedance on the system side in a system interconnection system, wherein a plurality of non-utility generating devices are interconnected to a utility system and there is reverse current. CONSTITUTION:Harmonic-wave generators 17a and 17b, which inject the higher harmonic waves that are synchronized with the voltage of the system and have the equal phase, frequency and voltage, respectively into a point A and a point B, are provided for the system buses of the in-plant in non-utility generating devices 1a and 1b. Furthermore, current transformers 19a and 19b, which detect the higher-harmonic current on the receiving side, and impedance detecting circuits 18a and 18b, which operate the impedance of the receiving side based on the outputs of the current transformers 19a and 19b, are provided. The service interruption on the system side is detected based on the impedance change obtained from the impedance detecting circuits 18a and 18b. Thus, a transfer breaking device can be omitted between a receiving-line sending breaker 5 and receiving-point breakers 14a and 14b in the demand house for the non- utility generating device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection protection device in case of a system accident in a system interconnection system (commercial power line interconnection system).

[0002]

2. Description of the Related Art In general, a grid interconnection system as shown in FIG. 5 is used by a high-voltage customer for grid interconnection of private power generation equipment such as cogeneration (hereinafter referred to as private power generation equipment). That is, in the system interconnection system of FIG. 5, 1a is a private power generation facility, 2 is a system busbar, 3 is a distribution substation, 4 is a transformer, 5 is a circuit breaker, and 6 is a transfer receiving device. The transfer receiving device 6 releases the circuit breaker 14a of the in-house private power generation equipment 1a in response to a signal from the substation 3 at the time of a system fault in the case of reverse power flow. The private power generation facility 1a includes a generator 11a driven by an engine (not shown), an automatic voltage regulator (hereinafter, referred to as AVR) 12a that controls the voltage of the generator 11a, and a generator 11a in a local system. And a circuit breaker 14a connecting the system bus 2 and the premises system 10, a premises load 15a, and a premises load circuit breaker 16a, and an undervoltage relay 21a as a protection device. , Frequency reduction relay 22a, overvoltage relay 23a, overcurrent relay 24a, directional ground fault relay 25a, reverse power relay 26
a, a generator abnormality detection relay 27a. Further, 1b is a customer equipped with a private power generation facility having the same configuration as the private power generation facility 1a, and 1c is a power receiving facility without a private power generation facility (circuit breaker 14c and premises load 15c).
It is a customer equipped with only.

When the following abnormality occurs in the grid interconnection system thus configured, it is necessary to immediately disconnect the private power generation equipment 1a, 1b from the power grid. (1) In the case of a customer's premises accident with a cogeneration installation (2) In the event of a power system accident

As a method of detecting the accident state at the time of these accidents, it is usually detected by a protective relay device as shown in FIG. That is, when there is no reverse power flow, the overcurrent relay 24a, the ground fault relay 25a, the generator abnormality detection relay 2
7a, reverse power relay 26a, frequency reduction relay 22a, etc. detect an abnormality at the time of an accident in the private power generation equipment or the grid,
The circuit breaker 14a is opened to disconnect from the system. On the other hand, when there is a reverse power flow, there is a case where the above-mentioned relay or the like cannot detect the disconnection of the substation circuit breaker 14a when the system is abnormal. Therefore, the transfer breaker 6 is provided in the dedicated line interconnection for protection. Is going.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide an expensive transfer interruption device in a dedicated line interconnection in the presence of reverse power flow in a high voltage distribution system interconnection. It is an object of the present invention to provide a system interconnection protection device that can detect a generator independent operation in the event of an accident on the system side in a private power generation facility in a premises.

[0006]

In order to achieve the above object, a system interconnection protection device of the present invention is used in a system interconnection system in which a plurality of private power generation facilities are system interconnected in a high voltage distribution system with reverse flow. , A harmonic generator that is synchronized with the system voltage for each local system bus and injects harmonics with the same phase, frequency, and voltage, and a current transformer that detects the harmonic current on the receiving side, An impedance calculation circuit for calculating the impedance on the power receiving side by the output of the sink is provided, and a power failure on the system side is detected by a change in the impedance obtained from the impedance calculation circuit.

[0007]

The system interconnection protection device of the present invention is made by paying attention to the fact that the system impedance greatly changes when a power failure occurs in the system bus having a plurality of private power generation facilities. When a power failure occurs, the detected impedance changes to a value set in advance by the system impedance map, so that it is possible to quickly detect that a power failure has occurred in the system. At this time, if other consumers having other private power generation equipment also have harmonic generators of the same frequency synchronized with the system voltage,
Since the states of the generators and loads of other consumers are irrelevant to the harmonic impedance of the power receiving point, most of them are impedances on the system side, so that power failure on the system side can be accurately detected.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram of a system interconnection protection device for an in-house power generation facility that is an embodiment of the present invention. The configuration different from the conventional system interconnection system of FIG. The only point is that the transfer breaker 6 is eliminated by providing the wave generators 17a and 17b and the impedance detection circuits 18a and 18b. Therefore, the same components as those of the conventional system interconnection system are designated by the same reference numerals and their description will be omitted. Omit it.

In FIG. 1, the harmonic generator 17a and the impedance detection circuit 18a of the private power generation equipment 1a are connected to a point A on the premises system bus, and the private power generation equipment 1b.
Harmonic generator 17b and impedance detection circuit 18
b is connected to point B on the system bus. 19a, 19
Reference numeral b denotes a current detecting current transformer for measuring the current on the power receiving side, which is configured to output a cutoff command to the power receiving circuit breakers 14a and 14b by the outputs of the impedance detecting circuits 18a and 18b. There is. As in the case of the private power generation facility 1a, an undervoltage relay 21b, a frequency lowering relay 22b, an overvoltage relay 23b, an overcurrent relay 2 are provided as protective devices.
4b, a directional ground fault relay 25b, a reverse power relay 26b, and a generator abnormality detection relay 27b.

FIG. 2 is a circuit diagram of the harmonic generator 17a. In FIG. 2, reference numeral 171 is an inverter device as a harmonic generation source, which is a three-phase bridge transistor inverter. Reference numeral 172 is a capacitor that is a supply source of the harmonic voltage, 173 is a transformer for injecting the harmonic wave, and 174 is a transformer for detecting the harmonic voltage, which is for returning the harmonic voltage generator. A harmonic voltage control circuit 175 controls the frequency, voltage, and phase of the harmonic voltage.

FIG. 3 shows the impedance detection circuit 18a.
181 is a transformer for detecting a harmonic voltage, 182 is a first filter circuit for detecting only the harmonic voltage component of the transformer 181, and 183 is a voltage from the output of the current transformer. It is a second filter circuit that converts and detects only the harmonic component of the voltage. 184 and 185 are DC voltage conversion circuits that convert the harmonic components of the voltage and current into DC voltages, 186 is an impedance calculation circuit that calculates the impedance of the harmonic components from the voltage component and current component, and 187 is the calculation circuit. The output circuit operates the output relay by comparing the output level with a preset impedance value and exceeding the set value.

By the way, the impedance on the power receiving point side as seen from the point A of the injection point of the harmonic voltage of the consumer shown in FIG.
As shown in (a), the generators and loads of other customers and the impedance of the system are connected in parallel. Here, generally, the total impedance Xbc (parallel impedance of XGb, XLb, and XLc) of another consumer and the system impedance X
In B, there is a relationship of XB << Xbc. However, the point of injecting the harmonic voltage is the power receiving point A of the in-house private power generation facility, and it is also the power receiving point B in other consumers having other private power generation, and the phase, frequency, and voltage are completely eliminated. If they are made equal, harmonic currents do not flow through the generators and loads in each premises, so the influence of the impedance of other consumers with private power generation equipment can be ignored,
The impedance circuit diagram shown in FIG.

Next, the operation of this embodiment will be described.
In the system interconnection system of the private power generation equipment according to the present embodiment of FIG. 1, the private power generation equipment 1a on the premises and the private power generation equipment 1b on the premises of other customers generate power by the generators 11a and 11b, respectively. The loads 15a and 15b may be in a so-called reverse power flow operation in which electric power is supplied from the generators 11a and 11b and the system side, or electric power is supplied from the generators 11a and 11b to the load and the system side. In the latter case of reverse power flow operation, if the harmonic voltage is injected into points A and B of each private power generation facility, the harmonic voltage and harmonic current from point A to the power receiving side are detected by impedance detection in Fig. 3. The impedance is calculated by inputting it to the circuits 18a and 18b, but this value is naturally less than or equal to a preset value. However, in this state, for some reason, the circuit breaker 5 on the system side
When the circuit is opened, the impedance at the power receiving point seen from point A is only the load of another customer who does not have a private power generation facility, the impedance detection value in the impedance detection circuit 18a in FIG. 3 changes, and a power failure on the system side is known. It will be. Therefore, the power receiving point breaker 14a can be quickly disconnected.

If a similar harmonic generator is also installed in a customer who does not have a private power generation facility, the load can ignore the effect of impedance, and in that case, only the presence or absence of system impedance will occur. The impedance detection circuit can also be extremely simple by detecting only the presence or absence of harmonic current.

[0015]

As described above, according to the system interconnection protection device of the present invention, in a system interconnection system with reverse power flow in which a plurality of private power generation facilities are connected to a high voltage distribution system,
When a power system power failure occurs, a harmonic power source is installed in each premises without receiving a signal from the distribution substation, and the power system power failure can be detected by constantly monitoring the harmonic impedance on the system side. It is possible to quickly disconnect the power receiving point breaker without providing an expensive transfer breaker between the electric wire feeding circuit breaker and the private power generation facility customer power receiving point circuit breaker.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a system interconnection protection device for a private power generation facility that is an embodiment of the present invention.

FIG. 2 is a circuit diagram of the harmonic generator of FIG.

FIG. 3 is an impedance detection circuit diagram of FIG.

FIG. 4 is an impedance circuit diagram of FIG.

FIG. 5 is a circuit diagram of a conventional system interconnection protection device for a private power generation facility.

[Explanation of symbols]

1a, 1b ... Private power generation equipment, 2 ... System busbar, 3 ... Distribution substation, 4 ... Transformer, 5 ... Circuit breaker, 6 ... Transfer receiving device,
10 ... internal system bus, 11a, 11b ... AC generator, 1
2a, 12b ... Automatic voltage regulator, 13a, 13b, 1
4a, 14b, 14c, 16a, 16b ... Circuit breaker, 15
a, 15b, 15c ... In-house load, 17a, 17b ... Harmonic generation circuit, 18a, 18b ... Impedance detection circuit, 19a, 19b ... Current transformer, 21a, 21b ... Undervoltage relay, 22a, 22b ... Frequency drop relay, 23
a, 23b ... Overvoltage relay, 24a, 24b ... Overcurrent relay, 25a, 25b ... Direction ground fault relay, 26a, 26
b ... Reverse power relay, 27a, 27b ... Generator abnormality detection relay.

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[Procedure amendment]

[Submission date] August 31, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

[Title of Invention] System interconnection protection device

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection protection device in case of a system accident in a system interconnection system (commercial power line interconnection system).

[0002]

2. Description of the Related Art Generally, a grid interconnection system as shown in FIG. 5 is used by a customer to grid-connect a private power generation facility such as cogeneration (hereinafter referred to as private power generation facility). That is, in the system interconnection system of FIG. 5, 1a is a private power generation facility, 2 is a system busbar, 3 is a distribution substation, 4 is a transformer, 5 is a receiving wire sending circuit breaker, 6
Is a transfer receiver. This transmission / reception device 6 uses a signal from the substation 3 in the event of a system fault in the case of reverse power flow, to generate power from the in-house private power generation equipment 1a
4a is released. In addition, the above-mentioned private power generation facility 1
a is a generator 1 driven by an engine (not shown)
1a, an automatic voltage regulator (hereinafter referred to as AVR) 12a that controls the voltage of the generator 11a, a circuit breaker 13a that connects the generator 11a to the premises system, and a circuit breaker that connects the system bus 2 to the premises system 10. 14a, a premises load 15a,
It has an internal load circuit breaker 16a, and further has an undervoltage relay 21a and a frequency lowering relay 2 as protection devices.
2a, an overvoltage relay 23a, an overcurrent relay 24a, a direction ground fault relay 25a, a reverse power relay 26a, and a generator abnormality detection relay 27a. Further, 1b is a customer equipped with a private power generation facility having the same configuration as the private power generation facility 1a described above, and 1c is a demand provided with only a power receiving facility (circuit breaker 14c and premises load 15c) that does not have a private power generation facility. Home

When the following abnormality occurs in the grid interconnection system thus configured, it is necessary to immediately disconnect the private power generation equipment 1a, 1b from the power grid. (1) In the case of a customer's premises accident with a cogeneration installation (2) In the event of a power system accident

As a method of detecting the accident state at the time of these accidents, it is usually detected by a protective relay device as shown in FIG. That is, when there is no reverse power flow, the overcurrent relay 24a, the ground fault relay 25a, the generator abnormality detection relay 2
7a, reverse power relay 26a, frequency reduction relay 22a, etc. detect an abnormality at the time of an accident in the private power generation equipment or the grid,
The circuit breaker 14a is opened to disconnect from the system. On the other hand, when there is a reverse power flow, there is a case where the above-mentioned relay or the like cannot detect the disconnection of the substation circuit breaker 5 when the system is abnormal. Therefore, the transfer breaker 6 is provided for protection.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to connect a distribution system without an expensive transfer interruption device in the case of reverse power flow and to have a private house on the premises. An object of the present invention is to provide a system interconnection protection device capable of detecting a generator independent operation in the case of a system side accident in a power generation facility.

[0006]

In order to achieve the above object, a system interconnection protection device of the present invention is provided in a system interconnection system in which a plurality of private power generation facilities are connected to a distribution system with a reverse flow. A harmonic generator that synchronizes with the system voltage to the local system bus and injects harmonics with the same phase, frequency, and voltage, a current transformer that detects the harmonic current on the receiving side, and the current transformer And an impedance calculation circuit for calculating the impedance on the power receiving side based on the output of 1., and a power failure on the system side is detected by a change in the impedance obtained from the impedance calculation circuit.

[0007]

The system interconnection protection device of the present invention is made by paying attention to the fact that the system impedance greatly changes when a power failure occurs in the system bus having a plurality of private power generation facilities. When a power failure occurs, the detected impedance changes to a value set in advance by the system impedance map, so that it is possible to quickly detect that a power failure has occurred in the system. At this time, if other consumers having other private power generation equipment also have harmonic generators of the same frequency synchronized with the system voltage,
Since the states of the generators and loads of other consumers are irrelevant to the harmonic impedance of the power receiving point, most of them are impedances on the system side, so that power failure on the system side can be accurately detected.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram of a system interconnection protection device for an in-house power generation facility that is an embodiment of the present invention. The configuration different from the conventional system interconnection system of FIG. It is the same as the conventional system interconnection system because it has the wave generators 17a and 17b and the impedance detection circuits 18a and 18b to eliminate the transfer interruption device 6 and the reverse power flow, which eliminates the reverse power relay 26a. The same reference numerals are given to the components and the description thereof will be omitted.

In FIG. 1, the harmonic generator 17a and the impedance detection circuit 18a of the private power generation equipment 1a are connected to a point A on the premises system bus, and the private power generation equipment 1b.
Harmonic generator 17b and impedance detection circuit 18
b is connected to point B on the system bus. 19a, 19
Reference numeral b denotes a current detecting current transformer for measuring the current on the power receiving side, which is configured to output a cutoff command to the power receiving circuit breakers 14a, 14b by the outputs of the impedance detecting circuits 18a, 18b. There is. In addition, the private power generation facility 1b,
As with the private power generation equipment 1a, an undervoltage relay 21b, a frequency lowering relay 22b, an overvoltage relay 2 as protection devices.
3b, an overcurrent relay 24b, a direction ground fault relay 25b, and a generator abnormality detection relay 27b.

FIG. 2 is a circuit diagram of the harmonic generator 17a. In FIG. 2, reference numeral 171 is an inverter device as a harmonic generation source, which is a three-phase bridge transistor inverter. Reference numeral 172 is a capacitor that is a supply source of the harmonic voltage, 173 is a transformer for injecting the harmonic wave, and 174 is a transformer for detecting the harmonic voltage, which is for returning the harmonic voltage generator. A harmonic voltage control circuit 175 controls the frequency, voltage, and phase of the harmonic voltage.

FIG. 3 shows the impedance detection circuit 18a.
181 is a transformer for detecting a harmonic voltage, 182 is a first filter circuit for detecting only the harmonic voltage component of the transformer 181, and 183 is a voltage from the output of the current transformer. It is a second filter circuit that converts and detects only the harmonic component of the voltage. 184 and 185 are DC voltage conversion circuits that convert the harmonic components of the voltage and current into DC voltages, 186 is an impedance calculation circuit that calculates the impedance of the harmonic components from the voltage component and current component, and 187 is the calculation circuit. The output circuit operates the output relay by comparing the output level with a preset impedance value and exceeding the set value.

By the way, the impedance on the power receiving point side as seen from the point A of the injection point of the harmonic voltage of the consumer shown in FIG.
As shown in (a), the generators and loads of other customers and the impedance of the system are connected in parallel. Here, generally, the total impedance Xbc (parallel impedance of XGb, XLb, and XLc) of another consumer and the system impedance X
In B, there is a relationship of XB << Xbc. However, the point of injecting the harmonic voltage is the power receiving point A of the in-house private power generation facility, and the power receiving point B is the same for other customers having other private power generations. If they are made equal, harmonic currents do not flow in the generators and loads in each premises, so the influence of the impedance of other consumers with private power generation equipment can be ignored,
The impedance circuit diagram shown in FIG.

Next, the operation of this embodiment will be described.
In the system interconnection system of the private power generation equipment according to the present embodiment of FIG. 1, the private power generation equipment 1a on the premises and the private power generation equipment 1b on the premises of other customers generate power by the generators 11a and 11b, respectively. The loads 15a and 15b may be in a so-called reverse power flow operation in which electric power is supplied from the generators 11a and 11b and the system side, or electric power is supplied from the generators 11a and 11b to the load and the system side. In the latter case of reverse power flow operation, if the harmonic voltage is injected into points A and B of each private power generation facility, the harmonic voltage and harmonic current from point A to the power receiving side are detected by impedance detection in Fig. 3. The impedance is calculated by inputting it to the circuits 18a and 18b, but this value is naturally less than or equal to a preset value. However, in this state, for some reason, the circuit breaker 5 on the system side
When the circuit is opened, the impedance at the power receiving point seen from point A is only the load of another customer who does not have a private power generation facility, the impedance detection value in the impedance detection circuit 18a in FIG. 3 changes, and a power failure on the system side is known. It will be. Therefore, the power receiving point breaker 14a can be quickly disconnected.

If a similar harmonic generator is also installed in a customer who does not have a private power generation facility, the load can ignore the effect of impedance, and in that case, only the presence or absence of system impedance will occur. The impedance detection circuit can also be extremely simple by detecting only the presence or absence of harmonic current.

[0015]

As described above, according to the system interconnection protection device of the present invention, in a system interconnection system with reverse power flow in which a plurality of private power generation facilities are connected to the distribution system, power distribution is performed at the time of a power system power failure. It is possible to detect a power system power failure by installing a harmonic power supply in each premises and constantly monitoring the harmonic impedance on the system side without receiving a signal from the utility substation, so It is possible to quickly disconnect the power receiving point breaker without providing an expensive transfer breaker with the private power generation facility consumer power receiving point breaker.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a system interconnection protection device for a private power generation facility that is an embodiment of the present invention.

FIG. 2 is a circuit diagram of the harmonic generator of FIG.

FIG. 3 is an impedance detection circuit diagram of FIG.

FIG. 4 is an impedance circuit diagram of FIG.

FIG. 5 is a circuit diagram of a conventional system interconnection protection device for a private power generation facility.

[Explanation of Codes] 1a, 1b ... Private power generation facility, 2 ... System busbar, 3 ... Distribution substation, 4 ... Transformer, 5 ... Receiving wire feeding breaker, 6 ...
Transfer / reception device, 10 ... Local system bus, 11a, 11b ...
Alternator, 12a, 12b ... Automatic voltage regulator, 14
a, 14b ... In-house power generation facility customer receiving point circuit breaker, 13
a, 13b, 14c, 16a, 16b ... Circuit breaker, 15
a, 15b, 15c ... In-house load, 17a, 17b ... Harmonic generation circuit, 18a, 18b ... Impedance detection circuit, 19a, 19b ... Current transformer, 21a, 21b ... Undervoltage relay, 22a, 22b ... Frequency drop relay, 23
a, 23b ... Overvoltage relay, 24a, 24b ... Overcurrent relay, 25a, 25b ... Direction ground fault relay, 26a ... Reverse power relay, 27a, 27b ... Generator abnormality detection relay.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (1)

[Claims] 1. In a system interconnection system in which a plurality of private power generation facilities are connected to a high-voltage distribution system with reverse power flow, the system voltage is synchronized with each system grid bus and the respective phases, frequencies, and voltages are synchronized. A harmonic generator that injects equal harmonics, a current transformer that detects the harmonic current on the receiving side,
An impedance calculation circuit for calculating the impedance on the power receiving side based on the output of the current transformer, and a system connection characterized by being configured to detect a power failure on the system side by a change in impedance obtained from the impedance calculation circuit. System protection device.