JP2751009B2 - Grid connection protection device - Google Patents

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 the event 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 connection system as shown in FIG. 4 is used by a high-voltage customer to connect a private power generation facility such as a cogeneration system (hereinafter referred to as a private power generation facility) to a grid.

That is, in the system interconnection system shown in FIG. 4, 1a is a private power generation facility, 2 is a system bus, 3 is a distribution substation, 4 is a transformer, 5 is a receiving line sending circuit breaker, and 6 is a transfer receiving device. It is. The transfer receiving device 6 receives a signal from the substation 3 at the time of a system failure in the case of a reverse power flow, and uses a private power generation facility customer power receiving point circuit breaker 14a of the private power generation facility 1a in the premises.
Is to cancel. 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 generator 11a
And a circuit breaker 13a for connecting the generator 11a to the local system
And a circuit breaker 14 for connecting the system bus 2 and the premises system 10
a, a private load 15a, and a private load circuit breaker 16a, and furthermore, an undervoltage relay 21 as a protection device.
a, a frequency reduction relay 22a, an overvoltage relay 23a, an overcurrent relay 24a, a directional ground fault relay 25a, a reverse power relay 26a, and a generator abnormality detection relay 27a. Reference numeral 1b denotes a customer provided with a private power generation facility having the same configuration as the private power generation facility 1a, and 1c denotes a power receiving facility (a circuit breaker 14c and a private load 15) having no private power generation facility.
A customer with only c).

[0004] In the system for interconnecting private power generation facilities configured as described above, it is necessary to immediately disconnect the private power generation facilities 1a and 1b from the power system when the following abnormalities occur. (1) In the event of an accident on the premises of the customer who installed Cogene

[0005] As a method of detecting the state of an accident 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, an overcurrent relay 24a, a directional ground fault relay 25a, a generator abnormality detection relay 27a, a reverse power relay 26a, a frequency reduction relay 22a, and the like are used to detect an abnormality at the time of an accident in the private power generation equipment or system. Then, the circuit breaker 14a is opened and disconnected from the system. On the other hand, when there is a reverse power flow, when the private power generation equipment and the load are almost balanced in the customer premises and there is little supply and demand of the system and power, the above-described relays and the like require the solution of the substation circuit breaker 5 when the system is abnormal. Column detection is difficult. For this reason, 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 of the present invention is to provide an in-house private power generation system in a distribution system interconnection without providing an expensive transfer shut-off device when there is a reverse power flow. An object of the present invention is to provide a system interconnection protection device capable of detecting a generator alone operation at the time of a system side accident in a facility.

[0007]

To achieve the above object, according to the solution to ## system interconnection protection device according to claim 1 of the present invention, generator
Private power supply with automatic voltage regulator to control output voltage
In a system interconnection system in which power equipment is connected to a distribution system with a reverse power flow via a private power generation facility customer receiving point breaker , the generator terminal voltage in the private power generation equipment is constantly monitored.
When the terminal voltage of the generator fluctuates slightly,
Generating a large signal Flip were then outputted to the automatic voltage regulator
A function generator acting to increase or decrease the output voltage of the machine ;
The terminal voltage of the generator becomes overvoltage or undervoltage.
And a protection relay for sensing the ever, the power distribution mains
The terminal voltage of the generator becomes an overvoltage or undervoltage, and detects the power failure of the power distribution system side by the state protection relay senses, the private power generation equipment demand by the action of but the function generator power outage The home power receiving point circuit breaker is released .

According to a second aspect of the present invention, in the system interconnection protection device according to the first aspect, the reactive power of the generator is detected.
An automatic voltage adjusting device for providing a reactive power adjusting device for outputting a signal corresponding to the reactive power amount , and adding the output of the function generator and the output of the reactive power adjusting device to control the terminal voltage of the generator. And a voltage correction signal .

[0009] Claim 3 of the present invention, in the system interconnection protection device according to claim 1, to detect the power factor of the generator Teso
A power factor adjusting device that outputs a signal corresponding to the power factor amount of
An output of the function generator and an output of the power factor adjusting device are added to generate a voltage correction signal of an automatic voltage adjusting device for controlling a terminal 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, a cross current compensator is provided in the automatic voltage regulator.

[0011]

The system interconnection protection device of the present invention focuses on the fact that the generator terminal voltage is governed by the system voltage during system interconnection, but is governed by the generator's automatic voltage regulator during isolated operation. In the isolated operation due to the characteristics of the function of the voltage command of the function generator, it works to increase the minute fluctuation of the generator terminal voltage, and shifts to the level that the protection relay senses, A power outage of the system can be detected.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a system interconnection protection device for a private power generation system according to an embodiment of the present invention (corresponding to claim 1). The configuration different from the conventional system interconnection system of FIG. A point that a function generator 17a for a voltage command is added to the automatic voltage regulator 12a in the private power generation facility 1a, and that the transfer cutoff device 6 and the reverse power relay 26a are eliminated.
Other configurations are the same as those of the conventional system interconnection system, and therefore, the same portions are denoted by the same reference characters and description thereof will be omitted.

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

Now, it is assumed that the point at which the vertical axis and the horizontal axis intersect is regarded as the rated voltage, and the system is connected to the system and operated at the rated voltage, so that 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. When the function generator is used, even if the voltage slightly rises and fluctuates from the rated voltage, the function a (the command value is larger than the detection value up to the point d) increases the voltage fluctuation,
Shift toward point d. The point d is a point at which the detection voltage and the voltage command are balanced, so that the voltage settles at this point and reaches a level that can be detected by the overvoltage relay, so that a power failure on the system side is known. Therefore, the receiving point circuit breaker 14
a can be separated. When the voltage drops slightly, the voltage shifts to the point c and can be detected by the undervoltage relay.

By the way, this function a during system interconnection is
Considering the effect of the above, if the detected voltage fluctuates for some reason, the automatic voltage regulator attempts to change the generator terminal voltage by the function a. Since it is controlled, the generator terminal voltage remains at the detected voltage value. At this time, the 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 facility 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, the present embodiment combines the configuration of the system interconnection protection system of the private power generation facility shown in FIG. 1 with a reactive power adjusting device (hereinafter referred to as AQR) 18a, and the output of the AQR 18a and the function generator 17a The sum of the outputs is used as a command value of the automatic voltage regulator.

By using the command value of the automatic voltage regulator, the voltage command function a shown in FIG. 2 is corrected to prevent an unnecessary power flow of the reactive power with the system. However, in the case of the islanding operation, the flow of the reactive power with the system side disappears, so that the operation of the voltage command function a in FIG. 2 is not suppressed by the AQR 18a, and the islanding operation can be detected even in the configuration of the present embodiment. . The AQR 18a also exerts a similar effect in a power factor adjusting device (APFR).

[0018]

As described above, according to the present invention,
In a system with reverse power flow where the private power generation equipment is connected to the distribution system, even if there is almost no balance between the private power generation equipment and the load on the customer premises and there is little supply and demand of the grid and power, there is a small By shifting the voltage fluctuations to the level sensed by the overvoltage relay or the undervoltage relay, without providing an expensive transfer breaker between the receiving line sending circuit breaker and the private power generation facility customer receiving point breaker,
The receiving point circuit breaker can be quickly disconnected.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram of a function of the function generator of FIG. 1;

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

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

[Explanation of symbols]

1a, 1b: Private power generation facilities, 2: System bus, 3: Distribution substation, 4: Transformer, 5: Receiving line sending circuit breaker, 6 ...
Transfer receiving device, 10: premises system bus, 11a: AC generator, 12a: Automatic voltage regulator, 13a, 14c, 16
a: Circuit breaker, 14a: Private power generation facility customer power receiving point circuit breaker, 15a, 15c: Local load, 17a: Function generator,
18a ... reactive power adjusting device, 19a ... adder, 21a ...
Under-voltage relay, 22a ... Frequency lowering relay, 23a ...
Overvoltage relay, 24a: overcurrent relay, 25a: directional ground fault relay, 26a: reverse power relay, 27a: relay for detecting generator abnormality.

Claims (4)

(57) [Claims] An automatic voltage regulator for controlling an output voltage of a generator
Private power generation equipment equipped with
In a system interconnection system in which there is a reverse power flow to the distribution system via a power point breaker, the terminal voltage of the generator in the private power generation equipment is constantly monitored, and the terminal voltage of the generator is slightly changed.
Then, a large signal corresponding to the amount of the fluctuation is generated by the automatic voltage adjustment.
Output to the regulator to increase or decrease the output voltage of the generator.
A function generator for use, the terminal voltage of the generator overvoltage Oh
Rui and a protection relay which senses that it has become undervoltage, the action of the function generator to the power distribution system side is a power failure
Terminal voltage of the generator due to overvoltage or undervoltage
It becomes, before by the state protection relay senses
Detects a power outage on the power distribution system side, and
A system interconnection protection device characterized by releasing a power receiving point circuit breaker . 2. The system interconnection protection device according to claim 1, further comprising: a reactive power adjusting device that detects a reactive power of the generator and outputs a signal corresponding to the reactive power amount . A system interconnection protection device, wherein an output and an output of the reactive power adjusting device are added to generate a voltage correction signal of an automatic voltage adjusting device for controlling a terminal voltage of the generator. 3. The system interconnection protection device according to claim 1, further comprising: a power factor adjusting device that detects a power factor of the generator and outputs a signal corresponding to the power factor amount . end of the generator by adding the outputs of said power factor adjusting device
A system interconnection protection device, which is used as a voltage correction signal for an automatic voltage regulator that controls a slave voltage. 4. The system interconnection protection device according to claim 1, wherein a cross current compensator is provided in the automatic voltage regulator.