JP2640628B2 - 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 the private power generation facility customer's power receiving point circuit breaker 16a of the private power generation facility 1a in the premises.
Is to cancel. The private power generation equipment 1a includes a generator 11a, an automatic voltage regulator 12a that controls the voltage of the generator 11a, and an engine 1 that drives the generator 11a.
3a and governor 1 for adjusting rotation speed of engine 13a
4a and a circuit breaker 15 for connecting the generator 11a to the local system
a, a circuit breaker 1 for connecting the system bus 2 and the premises system 10
6a, a local load 17a, and a local load circuit breaker 18a, and 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 above-described private power generation facility 1a, and 1c denotes a power receiving facility (a circuit breaker 16c and a local load 1) having no private power generation facility.
It is a customer equipped only with 7c).

[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

As a method of detecting the state of an accident at the time of these accidents, it is usually detected by a protection device as shown in FIG. That is, when there is no reverse power flow, the overcurrent relay 24
a, directional ground fault relay 25a, generator fault detection relay 2
7a, a reverse power relay 26a, a frequency reduction relay 22a, etc., detects an abnormality at the time of an accident of the private power generation equipment or system,
The circuit breaker 16a 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]

In order to achieve the above object, a system interconnection protection device according to a first aspect of the present invention interconnects a private power generation facility by a rotary generator to a distribution system with a reverse power flow. In a system interconnection system, a function generator that detects a frequency of the generator and outputs a large output signal with respect to a minute change in frequency, and a speed control that controls the frequency of the generator with an output of the function generator And a protection relay for detecting an abnormality in the frequency of the generator, and in the event of a power failure on the system side, the frequency of the generator is shifted to a level detected by the protection relay according to the function characteristics of the function generator. And detecting a power failure on the side.

According to a second aspect of the present invention, in the system interconnection protection device according to the first aspect, an active power adjusting device for detecting active power of the generator and outputting a signal corresponding to the detection signal is provided. An output of the function generator and an output of the active power adjusting device are added to form a command signal for the governor for controlling the frequency of the generator.

[0009]

In the system interconnection protection device of the present invention, the generator frequency is governed by the system frequency during system interconnection, but is governed by the governor of the engine connected to the generator during single operation. It is made by paying attention to the fact that when the isolated operation is performed by the characteristic of the function of the frequency command of the function generator, it works to increase the minute fluctuation of the generator frequency,
Will shift to the level that the protection relay senses,
A power outage of the system can be detected.

[0010]

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. The point that the frequency detector 30a and the function generator 31a for the frequency command are added to the governor 14a in the private power generation equipment 1a, the point that the transfer cutoff device 6 is eliminated, and the reverse power relay 26a because of the reverse power flow, The other point is that the frequency increasing relay 28a is replaced, and the other configuration is the same as that of the conventional system interconnection system. Therefore, the same portions are denoted by the same reference numerals and description thereof is omitted.

Thus, the frequency detector 30a of this embodiment
Detects the generator frequency from the generator terminal voltage, the function generator 31a generates a special function for the frequency detected value by the frequency detector 30a, and the governor 14a conventionally has a fixed value for adjusting to a constant speed. The configuration is such that the output of the function generator 31a is used instead of the frequency (rotation speed) command which is a value.

Next, the operation of this embodiment will be described.
First, in FIG. 2 showing the function of the function generator 31a and its function, a curve a (frequency command function) is represented by a function generator 31a.
Is an example of a function of the graph, and shows a relationship between a detection frequency and a frequency command. The dotted line b indicates the relationship (identical) between the generator frequency and the detected frequency.

Now, it is assumed that the point at which the vertical axis and the horizontal axis intersect is regarded as the rated frequency, and the system is connected to the system and operated at the rated frequency, so that there is little supply and demand of the system and electric power. Even if the system is disconnected in this state, the frequency fluctuation is very small and cannot be detected by a conventional frequency lowering relay or frequency raising relay. When the function generator is used, even if the frequency slightly rises and fluctuates from the rated frequency, the function a (the command value is larger than the detected value up to the point d) increases the frequency fluctuation, Shift toward point d. d
Since the point is a point at which the generator frequency and the frequency command are balanced, the frequency is settled here, and the frequency rises to a level that can be detected by the relay, and the power failure on the system side is known. Therefore, the power receiving point breaker 16a can be disconnected. When the frequency is slightly lowered, the frequency shifts to the point c and can be detected by the frequency reduction relay.

By the way, this function a during system interconnection is
Considering the effect of the above, when the frequency of the system fluctuates for some reason and the detection frequency fluctuates, the governor tries to change the generator frequency by the function a. Since the generator frequency is dominant, the generator frequency remains at the system frequency. Then, the frequency does not exceed the detection level of the frequency lowering relay or the frequency raising relay, and the operation is continued. At this time, active power may flow more than necessary in the direction from the generator to the grid 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 may be 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 an active power adjusting device (hereinafter referred to as APR) 32a with the system interconnection protection system configuration of the private power generation facility shown in FIG. 1 to output the output of the APR 32a and the function generator 31a. The value obtained by adding the output by the adder 33a is used as a command value of the governor.

By using the command value of the governor, FIG.
Is corrected to prevent unnecessary power flow of the active power with the system side. Here, APR32a
The response speed of the frequency command function a in FIG. 2 is set to be lower than the frequency shift speed by the frequency command function a in FIG.
Is not suppressed, the isolated operation can be detected even with the configuration of the present embodiment.

[0017]

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 Frequency fluctuation to the level sensed by the frequency lowering relay and the frequency raising relay, without providing an expensive transfer breaker between the receiving line sending circuit breaker and the private power generation equipment customer receiving point circuit 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: internal system bus, 11a: AC generator, 12a: Automatic voltage regulator, 13a: engine, 1
4a: governor, 15a, 16c, 18a: breaker, 16
a: Private power generation facility customer receiving point circuit breaker, 17a, 17c
... in-plant load, 21a ... under-voltage relay, 22a ... frequency-lowering relay, 23a ... over-voltage relay, 24a ... over-current relay, 25a ... directional ground fault relay, 26a ... reverse power relay, 27a ... ... frequency rising relay, 30a ... frequency detector, 31a ... function generator, 32a ... active power adjusting device, 33a ... adder.

Claims (2)

(57) [Claims] In a system interconnection system for interconnecting a private power generation facility with a rotary generator to a distribution system with a reverse power flow, a frequency of the generator is detected, and a small fluctuation of the frequency is detected.
A function generator that outputs a large output signal to the generator, a governor that controls the frequency of the generator based on the output of the function generator, and a protection relay that senses an abnormality in the frequency of the generator. A power failure on the system side by detecting a power failure on the system side by shifting the frequency of the generator to a level detected by the protection relay according to the function characteristics of the function generator at the time of a power failure on the power supply side. 2. The system interconnection protection device according to claim 1, wherein the active power of the generator is detected, and the active power of the generator is detected.
Active power regulator provided for outputting a Flip signal, the command signal of the speed governor to control the frequency of the addition to <br/> the generator the output of the active power regulator and an output of the function generator A grid interconnection protection device characterized by the following.