JPH07131931A - System interconnection protector - Google Patents

Abstract

PURPOSE:To detect the single operation of a generator at accident on system side, within a private power generation facility, in the interconnection of a power distribution system without providing an expensive transmission breaker, in case that there is a reverse current, by providing a high frequency generating mechanism inside the generator, and monitoring the high frequency impedance on system side at all times. CONSTITUTION:A higher harmonics generator is incorporated in the generator 11 a inside a private power generation facility 1a. In case of reverse-current operation, the higher harmonics voltage and higher harmonic current from point A to power reception side are inputted into an impedance detecting circuit 31A so as to operate impedance, but this value is not more than the value set in advance. But, if the breaker 5 on system side opens by any reason in this condition, the impedance at power reception point viewed from point A becomes only the generator of a customer and the load, and the detection value of impedance in a detecting circuit 31a changes, and a user can know the power stoppage on system side. Accordingly, the breaker 14a on power reception point 14a can be cut off quickly.

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. In addition, 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 the generator 11a as a local system. It is provided with a circuit breaker 13a to be connected, a circuit breaker 14a to connect the system bus 2 to 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 drop relay 22a, overvoltage relay 23a, overcurrent relay 24a, directional ground fault relay 25a, reverse power relay 26
a, a generator abnormality detection relay 27a.

Reference numeral 1b is a customer equipped with a private power generation facility having the same structure as the private power generation facility 1a, and 1c.
Is a customer who has only power receiving equipment (circuit breaker 14c and premises load 15c) without private power generation equipment.

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

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.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its object is to connect a high-voltage power distribution system without providing an expensive transfer interruption device in a dedicated line connection in the case of reverse power flow. 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 system.

[0007]

In order to achieve the above object, the system interconnection protection device of the present invention is a system interconnection system in which a private power generation facility is connected to a high-voltage distribution system with reverse power flow. Harmonic generator that injects higher harmonics into the internal system busbar installed inside the generator of the private power generation facility, current transformer that detects the harmonic current on the power receiving side, and impedance on the power receiving side due to the output of the current transformer And an impedance calculation circuit for calculating the above, and a power failure on the system side is detected by a change in impedance obtained from the impedance calculation circuit.

[0008]

The system interconnection protection device of the present invention is made by paying attention to the fact that the system impedance changes during a power failure on the system bus side. The system impedance is constantly monitored, and when a power failure occurs, the detected impedance is detected in advance. By changing to the value set by the system impedance map, it is possible to promptly detect that a power failure has occurred in the system.

[0009]

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 a private power generation facility that is an embodiment of the present invention. The configuration different from the conventional system interconnection system of FIG. 5 is a generator 11a in the private power generation facility 1a. This is the point that the harmonic generator is built in and the impedance detection circuit 31a is provided and the transfer interruption device 6 is abolished. Therefore, the same components as those of the conventional system interconnection system are designated by the same reference numerals and the description thereof will be omitted. .

In FIG. 1, the impedance detection circuit 31a of the private power generation equipment 1a is connected to a point A on the local system bus. Reference numeral 32a is a current detecting current transformer for measuring the current on the power receiving side, and is configured to output a cutoff command to the internal power receiving circuit breaker 14a by the output of the impedance detection circuit 31a.

As for the generation of higher harmonics inside the generator 11a, it is not possible that a normal sinusoidal waveform does not contain any higher harmonics. Paying attention to the fact that the content ratio of higher harmonics of each order can be changed by changing the value or changing the pitch of the winding on the stator side, for example, as shown in FIG. If the gap is kept constant, the result is shown in Fig. 2 (b).
A trapezoidal distorted waveform is obtained, and a generator having a harmonic generation mechanism can be configured by emphasizing higher harmonics than a normal sinusoidal waveform. Of course, at this time, the waveform deviation rate of the generator output waveform including harmonics is 10%.
Must be within

FIG. 3 shows the impedance detection circuit 31a.
In the figure, 311 is a transformer for detecting harmonic voltage, 312 is a first filter circuit for detecting only the harmonic voltage component of the transformer 311, and 313 is a voltage of the output of the current transformer. Is a second filter circuit that detects the harmonic component of the voltage by converting Reference numerals 314 and 315 denote a DC voltage conversion circuit for converting the harmonic components of the voltage and current into a DC voltage, 316 is an impedance calculation circuit for calculating the impedance of the harmonic component from the voltage component and the current component, and 317 is the calculation circuit 316. Is an output circuit for operating the output relay when the output level is compared with the impedance value set by the setting device 318 in advance and exceeds the set value.

By the way, as shown in FIG. 4, the impedance on the power receiving point side seen from the point A in FIG. 1 is a parallel connection of the generator and load of another consumer and the impedance of the system.
Here, 13b, 14b and 16b are circuit breakers of the consumer 1b,
Reference numeral 14c is a circuit breaker for the customer 1c, and generally, the customer's premises impedance Xbc (XGb, XLb, X
Lc parallel impedance) and system impedance XB
Then, there is a relationship of XB << Xbc.

The operation of the embodiment thus constructed will be described below. In the grid 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 are generators 11 respectively.
Power is generated at a and 11b. 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, the harmonic voltage and harmonic current from point A to the power receiving side are input to the impedance detection circuit 31a in FIG. 3 to calculate the impedance, but this value is naturally set in advance. It is less than or equal to the value. However, if the circuit breaker 5 on the system side is opened for some reason in this state, the impedance of the power receiving point seen from point A is only the generators and loads of other consumers, and the impedance detection circuit 31a in FIG. 3 detects the impedance. The value changes, and the power failure on the grid side is known. Therefore, the power receiving point breaker 14a can be quickly disconnected. In addition, it does not particularly relate to the presence or absence of the harmonic generation mechanism in the private power generation equipment 1b of other customers.

In addition to the above harmonic generating mechanism, a method of superimposing the slot ripple on the fundamental wave without applying skew may be considered. The ripple frequency fs in this case is determined by the following equation. Here, ns: number of slots, N: number of rotations (rpm) fs = ns × N ÷ 60

[0016]

As described above, according to the present invention, in the grid interconnection system with reverse power flow in which the private power generation equipment is interconnected to the high-voltage distribution system, the signal from the distribution substation is received when the power system is interrupted. Even if you do not have it, you can detect a power failure in the power system by installing a harmonic generation mechanism inside the generator and constantly monitoring the harmonic impedance on the system side.
The receiving point circuit breaker can be quickly disconnected without providing an expensive transfer breaking device between the receiving wire feeding circuit breaker and the private power generation facility customer receiving point circuit breaker.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram including the shape of a magnetic pole and harmonics.

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 system 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, 21a ... undervoltage relay, 22a ... frequency drop relay, 23a ... overvoltage relay, 24a ... overcurrent relay, 25a ... direction grounding relay,
26a ... Reverse power relay, 27a ... Generator abnormality detection relay, 31a ... Impedance detection circuit, 32a ... Current transformer.

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[Procedure amendment]

[Submission date] September 9, 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, private power generation facility 1a
Is a generator 11 driven by an engine (not shown)
a, 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, a system bus 2 and a premises system 1
0 is provided with a circuit breaker 14a for connecting to 0, a premises load 15a, and a premises load circuit breaker 16a. Further, as a protection device, an undervoltage relay 21a and a frequency lowering relay 22 are provided.
a, 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.

Reference numeral 1b is a customer equipped with a private power generation facility having the same structure as the private power generation facility 1a, and 1c.
Is a customer who has only power receiving equipment (circuit breaker 14c and premises load 15c) without private power generation equipment.

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

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.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide on-site private power generation in a distribution system interconnection without providing an expensive transfer interruption device in the case of reverse power flow. 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 an accident on the system side in the facility.

[0007]

In order to achieve the above object, a system interconnection protection device of the present invention is a system interconnection system in which an in-house power generation facility is connected to a distribution system with reverse power flow. Harmonic generator that injects harmonics to the internal system busbar installed inside the generator of the facility, current transformer that detects the harmonic current on the power receiving side, and the impedance on the power receiving side is calculated from the output of the current transformer And an impedance calculation circuit for performing a power failure on the system side based on a change in impedance obtained from the impedance calculation circuit.

[0008]

The system interconnection protection device of the present invention is made by paying attention to the fact that the system impedance changes during a power failure on the system bus side. The system impedance is constantly monitored, and when a power failure occurs, the detected impedance is detected in advance. By changing to the value set by the system impedance map, it is possible to promptly detect that a power failure has occurred in the system.

[0009]

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 a private power generation facility that is an embodiment of the present invention. The configuration different from the conventional system interconnection system of FIG. 5 is a generator 11a in the private power generation facility 1a. And a point that the transfer breaker 6 is abolished by installing the harmonic generator in the, and providing the impedance detection circuit 31a.
Since the reverse power flow is present, the reverse power relay 26a is eliminated. Therefore, the same components as those of the conventional system interconnection system are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 1, the impedance detection circuit 31a of the private power generation equipment 1a is connected to a point A on the local system bus. Reference numeral 32a is a current detecting current transformer for measuring the current on the power receiving side, and is configured to output a cutoff command to the internal power receiving circuit breaker 14a by the output of the impedance detection circuit 31a.

As for the generation of higher harmonics inside the generator 11a, it is not possible that a normal sinusoidal waveform does not contain any higher harmonics. Paying attention to the fact that the content ratio of higher harmonics of each order can be changed by changing the value or changing the pitch of the winding on the stator side, for example, as shown in FIG. If the gap is kept constant, the result is shown in Fig. 2 (b).
A trapezoidal distorted waveform is obtained, and a generator having a harmonic generation mechanism can be configured by emphasizing higher harmonics than a normal sinusoidal waveform. Of course, at this time, the waveform deviation rate of the generator output waveform including harmonics is 10%.
Must be within

FIG. 3 shows the impedance detection circuit 31a.
In the figure, 311 is a transformer for detecting harmonic voltage, 312 is a first filter circuit for detecting only the harmonic voltage component of the transformer 311, and 313 is a voltage of the output of the current transformer. Is a second filter circuit that detects the harmonic component of the voltage by converting Reference numerals 314 and 315 denote a DC voltage conversion circuit for converting the harmonic components of the voltage and current into a DC voltage, 316 is an impedance calculation circuit for calculating the impedance of the harmonic component from the voltage component and the current component, and 317 is the calculation circuit 316. Is an output circuit for operating the output relay when the output level is compared with the impedance value set by the setting device 318 in advance and exceeds the set value.

By the way, as shown in FIG. 4, the impedance on the power receiving point side seen from the point A in FIG. 1 is a parallel connection of the generator and load of another consumer and the impedance of the system.
Here, 13b, 14b and 16b are circuit breakers of the consumer 1b,
Reference numeral 14c is a circuit breaker for the customer 1c, and generally, the customer's premises impedance Xbc (XGb, XLb, X
Lc parallel impedance) and system impedance XB
Then, there is a relationship of XB << Xbc.

The operation of the embodiment thus constructed will be described below. In the system interconnection system of the private power generation equipment according to the present embodiment of FIG. 1, the in-house private power generation equipment 1a and the in-house private power generation equipment 1b of other customers are supplied with electric power from the commercial grid side, or Reverse power operation is performed, in which surplus power is sent from the power generation equipment to the commercial grid side. In the latter case of reverse power flow operation, the impedance detection circuit 3 in FIG. 3 detects the harmonic voltage and harmonic current from point A to the power receiving side.
The impedance is calculated by inputting into 1a, but this value is naturally less than or equal to a preset value. However, if the circuit breaker 5 on the system side is opened for some reason in this state, the impedance of the power receiving point seen from point A is only the generators and loads of other consumers, and the impedance detection circuit 31a in FIG. 3 detects the impedance. The value changes, and the power failure on the grid side is known. Therefore, the power receiving point breaker 14a can be quickly disconnected. In addition, it does not particularly relate to the presence or absence of the harmonic generation mechanism in the private power generation equipment 1b of other customers.

In addition to the above harmonic generating mechanism, a method of superimposing the slot ripple on the fundamental wave without applying skew may be considered. The ripple frequency fs in this case is determined by the following equation. Here, ns: number of slots, N: number of rotations (rpm) fs = ns × N ÷ 60

[0016]

As described above, according to the present invention, in the grid interconnection system with reverse power flow in which the private power generation equipment is interconnected to the distribution grid, the signal from the distribution substation is not received at the time of power grid interruption. Even if a power generation failure is detected by installing a harmonics generation mechanism inside the generator and constantly monitoring the harmonics impedance on the grid side, it is possible to detect a power failure in the power grid. It is possible to quickly disconnect the power receiving point breaker without providing an expensive transfer breaker with the breaker.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram including the shape of a magnetic pole and harmonics.

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 system 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 receiving device, 10 ... In-house system busbar, 11a ... AC generator, 12a ... Automatic voltage adjusting device, 13a, 13b, 14
c, 16a, 16b ... Circuit breaker, 14a, 14b ... Private power generation facility customer receiving point circuit breaker, 15a, 15c ... Local load, 21a ... Undervoltage relay, 22a ... Frequency drop relay, 23a ... Overvoltage relay, 24a ... Over Current relay, 2
5a ... Direction grounding relay, 26a ... Reverse power relay, 27a
... a generator abnormality detection relay, 31a ... an impedance detection circuit, 32a ... a current transformer.

[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 grid interconnection system in which private power generation equipment is connected to a high-voltage distribution system with reverse power flow, harmonic generation is performed by injecting harmonics into a local system busbar provided inside the generator of the private power generation equipment. An apparatus, a current transformer that detects a harmonic current on the power receiving side, and an impedance calculation circuit that calculates the impedance on the power receiving side by the output of the current transformer,
A system interconnection protection device characterized in that a system power failure is detected by a change in impedance obtained from the impedance calculation circuit.