JPH0888937A - Protecting equipment of interconnected system - Google Patents

Abstract

PURPOSE: To detect a single operation of a generator at the time of an accident on the system side by detecting a power failure on the system side by shifting a terminal voltage of the generator to a level to be sensed by a protective relay, by function characteristics of a function generator, at the time of the power failure on the system side. CONSTITUTION: A function generator 17a for voltage command is added to an automatic voltage regulating device 12a in nonutility power generating installation 1a, while a transfer interrupting device and a reverse power relay are disused. In the case when a system is put off parallel and a voltage changes so as to rise slightly above a rated voltage, the change of the voltage is increased by the operation of a function (a) (a command value is larger than a detected value up to a point (d)) and the voltage is shifted to the point (d). Since a detected voltage and the voltage command are balanced at the point (d), a level which can be sensed by an overvoltage relay 23a is reached and a power failure on the system side is known. Accordingly, a receiving point breaker 14a can be cut off. In the case when the voltage lowers slightly; besides, the voltage is shifted to a point (c) and this can be sensed by an undervoltage relay 21a.

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 Generally, a grid interconnection system as shown in FIG. 4 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 shown in FIG. 4, 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 feeding breaker, and 6 is a transfer receiving device. Is. This transfer receiving device 6 receives a signal from the substation 3 at the time of a system fault in the case of reverse power flow, and generates power from the private power generation facility 1a on the premises of the customer's own power generation facility.
Is to be released. The private power generation facility 1a includes a generator 11a driven by an engine (not shown),
Automatic voltage regulator 12a for controlling the voltage of the generator 11a
And a circuit breaker 13a for connecting the generator 11a to the premises system
And a circuit breaker 14 connecting the system bus 2 and the premises system 10
a, a premises load 15a, and a premises load circuit breaker 16a, and an undervoltage relay 21 as a protection device.
a, a frequency lowering relay 22a, 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, and 1c is a power receiving facility without a private power generation facility (circuit breaker 14c and premises load 15).
It is a customer with only c).

In the system 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 when the following abnormality occurs. (1) In the case of an accident on the premises of a customer installing cogenes (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 system interconnection protection device as shown in FIG. That is, when there is no reverse power flow, the overcurrent relay 24a, the direction ground fault relay 25a, the generator abnormality detection relay 27a, the reverse power relay 26a, the frequency reduction relay 22a, etc. are used to detect an abnormality in the power generation facility or the grid. Then, the circuit breaker 14a is opened to disconnect from the system. On the other hand, in the case of reverse power flow, when there is almost no demand and supply of power to the grid and the private power generation equipment in the customer premises, there is almost no supply and demand of power to the grid. Row detection is difficult. Therefore, a transfer blocking device 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, the grid interconnection protection device of claim 1 of the present invention interconnects a private power generation facility using a rotary generator to a distribution system with reverse power flow. In a system interconnection system, a function generator that generates a function for the generator terminal voltage, an automatic voltage regulator that controls the voltage of the generator by the output of the function generator, and an abnormality in the terminal voltage of the generator And a protection relay for detecting a power failure on the system side by detecting the power failure on the system side by shifting the terminal voltage of the generator to a level detected by the protection relay according to the function characteristic of the function generator during a power failure on the system side. And

According to a second aspect of the present invention, in the grid interconnection protection device according to the first aspect, the function generator, a reactive power adjusting device for controlling a generator reactive power, an output of the function generator and the It is characterized in that an adder for adding outputs of the reactive power adjusting device and an output of the adder are used as voltage commands of the automatic voltage adjusting device for controlling the voltage of the generator.

According to a third aspect of the present invention, in the system interconnection protection device according to the first aspect, the function generator, the power factor adjusting device for controlling the power factor of the generator, the output of the function generator and the It is characterized in that an adder for adding outputs of the power factor adjusting device and an output of the adder are used as voltage commands of the automatic voltage adjusting device for controlling the voltage of the generator.

According to a fourth aspect of the present invention, in the system interconnection protection device according to the first to third aspects, the automatic voltage regulator is provided with a cross current compensator.

[0011]

In the system interconnection protection device of the present invention, it is noted that the generator terminal voltage is controlled by the system voltage during system interconnection, but is controlled by the automatic voltage regulator of the generator during islanding. When it is operated independently due to the characteristics of the function of the voltage command of the function generator, it works to increase the minute fluctuations of the generator terminal voltage, and the protection relay shifts to a level that it can sense. It is possible to detect a power outage.

[0012]

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 (corresponding to claim 1) of the present invention. The configuration different from the conventional system interconnection system of FIG. The point is that the function generator 17a for the voltage command is added to the automatic voltage regulator 12a in the private power generation equipment 1a, and the point that the transfer breaker 6 and the reverse power relay 26a are abolished.
Since other configurations are the same as those of the conventional system interconnection system, the same parts are denoted by the same reference numerals and the description thereof will be omitted.

Next, the operation of this embodiment will be described.
First, in FIG. 2 showing the function of the function generator 17a and its function, the curve a (voltage command function) is an example of the function of the function generator 17a, and shows the relationship between the generator terminal voltage and the voltage command. . The dotted line b indicates the relationship (identical) of the detected voltage with respect to the generator terminal voltage.

Now, assume that the point where the vertical axis and the horizontal axis intersect is the rated voltage, and that the system is operating at the rated voltage in cooperation with the system, and there is almost no supply and demand of the system and electric power. Even if the system is disconnected in this state, the voltage fluctuation is very small and cannot be detected by the conventional overvoltage relay or undervoltage relay. If a function generator is used, even if the voltage rises slightly above the rated voltage, the function a (the command value is larger than the detected value up to point d) increases the voltage fluctuation,
Shift toward point d. Since the point d is a point where the detected voltage and the voltage command are balanced, the voltage settles down at this point and becomes a level that the overvoltage relay can detect, and the power failure on the system side is known. Therefore, the receiving point breaker 14
a can be separated. When the voltage drops slightly, it shifts to point c and can be detected by the undervoltage relay.

By the way, this function a during grid interconnection
Considering the effect of, when the detected voltage fluctuates for some reason, the automatic voltage regulator tries to change the generator terminal voltage by the function a, but during the grid connection, the generator terminal voltage becomes Since it is controlled, the generator terminal voltage remains the detected voltage value. At this time, reactive power may flow more than necessary from the generator side to the system side or in the opposite direction. When such an operation is a problem, the system interconnection protection system for the private power generation equipment in FIG. 3 is used.

FIG. 3 is a block diagram of another embodiment (corresponding to claim 2) of the present invention. As shown in the figure, in the present embodiment, the reactive power regulating device (hereinafter referred to as AQR) 18a is combined with the system interconnection protection system configuration of the private power generation facility shown in FIG. 1, and the output of the AQR 18a and the function generator 17a are combined. The sum of the outputs is used as the command value for the automatic voltage regulator.

By using the command value of this automatic voltage regulator, the voltage command function a of FIG. 2 is corrected to prevent unnecessary reactive power flow with the system side. However, in the isolated operation, there is no reactive power flow with the grid side, so the AQR 18a does not suppress the function of the voltage command function a in FIG. 2, and the configuration of this embodiment can also detect the isolated operation. . The AQR 18a also exhibits the same effect in the power factor adjusting device (APFR).

[0018]

As described above, according to the present invention,
In a system with reverse power flow in which the private power generation equipment is connected to the distribution system, even if there is almost no grid disconnection when there is almost no supply and demand of the grid and the private power generation equipment on the customer premises, the load is almost balanced. By shifting such voltage fluctuations to a level detected by an overvoltage relay or an undervoltage relay, without providing an expensive transfer breaker between the incoming wire feed breaker and the private power generation customer demand point breaker,
The receiving point breaker can be quickly disconnected.

[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 characteristic diagram of a function included in the function generator of FIG.

FIG. 3 is a configuration diagram of a system interconnection protection system for a private power generation facility that is another embodiment of the present invention.

FIG. 4 is a block diagram of a conventional system interconnection protection system for private power generation equipment.

[Explanation of symbols]

1a, 1b ... In-house power generation equipment, 2 ... System bus, 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, 14c, 16
a: circuit breaker, 14a ... private power generation facility customer receiving point circuit breaker, 15a, 15c ... premises load, 17a ... function generator,
18a ... Reactive power adjusting device, 19a ... Adder, 21a ...
Undervoltage relay, 22a ... Frequency drop relay, 23a ...
Overvoltage relay, 24a ... Overcurrent relay, 25a ... Direction ground fault relay, 26a ... Reverse power relay, 27a ... Generator abnormality detection relay.

[Procedure amendment]

[Submission date] July 20, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

In order to achieve the above object, the system interconnection protection device according to claim 1 of the present invention connects a private power generation facility using a rotary generator to a distribution system with reverse power flow. In a system interconnection system, a function generator that detects the generator terminal voltage and outputs a large signal with respect to a minute fluctuation of the terminal voltage, and an automatic voltage that controls the generator voltage by the output of the function generator An adjusting device and a protection relay for detecting an abnormality in the terminal voltage of the generator are provided, and the terminal voltage of the generator is shifted to a level sensed by the protection relay according to the functional characteristics of the function generator during a power failure on the system side. This is characterized by detecting a power failure on the system side.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

According to a second aspect of the present invention, in the grid interconnection protection device according to the first aspect, a reactive power adjusting device for detecting the reactive power of the generator and outputting a signal corresponding to the detected signal is provided. It is characterized in that an output of the function generator and an output of the reactive power adjusting device are added to obtain a voltage command of the automatic voltage adjusting device for controlling the voltage of the generator.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

According to a third aspect of the present invention, in the grid interconnection protection device according to the first aspect, a power factor adjusting device for detecting the power factor of the generator and outputting a signal according to the detection signal is provided. It is characterized in that the output of the function generator and the output of the power factor adjusting device are added to obtain a voltage command of the automatic voltage adjusting device for controlling the voltage of the generator.

Claims (4)

[Claims] 1. A function generator that generates a function with respect to the generator terminal voltage in a grid interconnection system that interconnects a private power generation facility using a rotary generator with a distribution system with reverse power flow, and a function generator of the function generator. An automatic voltage regulator that controls the voltage of the generator by the output, and a protection relay that senses an abnormality in the terminal voltage of the generator are provided, and during a power failure on the system side, the function characteristic of the function generator causes the generator A grid interconnection protection device that detects a power failure on the grid side by shifting the terminal voltage to a level that the protection relay detects. 2. The grid interconnection protection device according to claim 1, wherein the function generator, a reactive power adjusting device for controlling generator reactive power, an output of the function generator and an output of the reactive power adjusting device. And an output of the adder as a voltage command of the automatic voltage regulator for controlling the voltage of the generator. 3. The system interconnection protection device according to claim 1, wherein the function generator, a power factor adjusting device for controlling a generator power factor, an output of the function generator and an output of the power factor adjusting device. And an output of the adder as a voltage command of the automatic voltage regulator for controlling the voltage of the generator. 4. The system interconnection protection device according to claim 1, wherein the automatic voltage regulator is provided with a cross current compensator.