JPH07322509A - Station protective apparatus - Google Patents

Abstract

PURPOSE:To obtain a station protective apparatus in which the single operation state of a nonutility generation installation is detected surely on the side of the nonutility generation installation, in which a link with a commercial power system is cut off in the single operation state and which can protect the station of the generation installation. CONSTITUTION:A station protective apparatus 11 is provided with a criterion- value change means which applies an inspection signal to the criterion value of the terminal voltage of an automatic voltage adjusting device 32, with a state discrimination means 19 by which whether a nonutility generation installation 18 is a single operation or a linked operation is discriminated on the basis of a change in the terminal voltage of a synchronous generator 12 and a change in the reactive power when the inspection signal is applied and with a contact output means 27 which issues a command to cut off a connection with a link bus 16 when the single operation is discriminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-house protective device for a private power generation facility that operates in parallel with a commercial power system.

[0002]

2. Description of the Related Art In recent years, cogeneration and distributed power sources have been attracting attention as private power generation facilities from the standpoint of global environmental protection, due to the enhancement of efforts at various places concerned and the difficulty of location of large-scale power sources.

In order to complement these as power sources, it is necessary and indispensable to connect them to a commercial power system. Conventional power transmission and distribution systems have been constructed on the premise of one-way supply of electricity from business-use power plants to consumers, so the power from these private power generation facilities to Supply is not yet generalized.

As one of the reasons for this, it is stipulated that a transfer breaker be provided between the interconnection breaker of the commercial power system and the parallel breaker of the private power generation facility (Ministry of International Trade and Industry, Agency for Natural Resources and Energy). , Public Utility Division: "Grid interconnection technical requirement guideline"), it is practically difficult to obtain the transfer cutoff signal from the upper grid when connecting to the general power line, and the private power generation equipment is in the vicinity when the commercial power grid is stopped. There is a case where continuous operation with the load of, that is, so-called independent operation for a so-called commercial electric power system is performed, and there is no established measure for that case.

That is, in the event that the commercial power system is stopped due to an accident or some other reason, if the private power generation facility continues to operate with a partial load in the vicinity of the private power generation facility under the control of the power system side, private power generation Since the power system is partially alive with a part of the load that the facility is supplying power to, there is a danger to workers for restoration and it is not synchronized when the commercial power system side is restored. There is concern about danger such as input. Therefore, it is necessary to take measures to prevent such an independent operation of the private power generation equipment.

FIG. 3 shows an example of a system configuration in which such a commercial power system and a private power generation facility are operated in parallel for more specific description. The commercial power system 18 is connected via a grid breaker 17 to a grid bus 16 to which a grid-side load facility 35 is connected. On the other hand, private power generation equipment 11A,
The 11B includes synchronous generators 12A and 12B, respectively, and supplies electric power to the customer load facilities 36A and 36B owned by the respective generators. And these private power generation facilities 11
A and 11B are power receiving circuit breakers 14A and 14B and parallel circuit breaker 15
It is connected to the interconnection bus 16 via A and 15B so that the power can be purchased from the commercial power system 18 when the power is insufficient, and can be sold when the power is excessive.

When the commercial power system 18 has an accident and the grid breaker 17 is opened while the commercial power system 18 and the private power generation facilities 11A and 11B are operating in parallel, Since the system bus 16 is still connected to the private power generation equipment 11A, 11B, the private power generation equipment 11A, 11B remains in the system-side load equipment 35. That is, the private power generation facilities 11A and 11B are operated independently.

Such an independent operation of the private power generation equipment 11A, 11B entails danger to the operator for restoration because the interconnection bus 16 is in a live state. Also, load equipment on the grid side 35
The voltage, frequency and phase of the interconnection bus 16 will change from the values immediately before the accident depending on the magnitude of the. In such a case, the commercial power system 18 and private power generation equipment 11A, 11
B is an asynchronous operation state, so commercial power system
Asynchronous closing is performed when the interconnection breaker 17 is closed at the time of restoration of 18.

Therefore, the private power generation facility 11 as described above is used.
When the interconnection breaker 17 is opened to avoid the independent operation of A and 11B, the parallel breaker of the private power generation facilities 11A and 11B
15A and 15B are open.

[0010]

However, as described in a known document (OHM, '92 / 2, pp. 18 to 21 "Current state and future prospect of grid interconnection technology for distributed power sources"). ,
The fact that the interconnection breaker 17 has been opened indicates that the private power generation equipment 11A, 11
There is a problem with the means of transmitting to the B side.

That is, as shown in FIG. 4, in place of the interconnection circuit breaker 17 in FIG. 3, a transfer circuit breaker 38 having a circuit breaker information transmitter 37 so that it can transfer the opened information, From here parallel breaker in private power plant 15
The transfer cutoff method that transfers the release to the breaker switching information receiver 39 provided in A and 15B is the most reliable,
There is a problem in economics because the dedicated transfer line 40 is required.

[0012] Further, when the output currents of the synchronous generators 12A, 12B of the private power generation equipment 11A, 11B become overcurrent or the output voltage becomes excessive or insufficient, it is confirmed that the interconnection breaker 17 is opened. Although it is considered to detect it, it is pointed out that it is difficult to detect the islanding operation when the load is balanced.

In the future, in consideration of the increase in the amount of introduction as a power supply to the electric power system of the private power generation equipment, it is required to surely detect the islanding operation state of the private power generation equipment on the private power generation equipment side.

An object of the present invention is to reliably detect the islanding state of a private power generation facility on the private power generation facility side, and
The purpose of the present invention is to obtain an on-site protection device that can shut off the interconnection with the commercial power system and protect the inside of the power generation facility when operating independently.

[0015]

In the on-site protective device of the present invention, a commercial power system is connected to an interconnection busbar via an interconnection breaker, and a private power generation facility having a synchronous generator is connected via a parallel breaker. Terminal voltage of the automatic voltage regulator to control the terminal voltage of the synchronous generator and the reactive power in the in-house protection device of the private power generation equipment that is connected to the interconnection bus and operates the commercial power system and the private power generation equipment in parallel. The reference value changing means for applying the inspection signal to the reference value and the private power generation equipment to which the synchronous generator belongs based on the change of the terminal voltage and the reactive power of the synchronous generator when the inspection signal is applied operates independently. State determining means for determining whether or not it is an interconnected operation with a commercial power system, and an instruction for disconnecting the connection with the interconnecting bus when the state determining means determines that the private power generation facility is operating alone Characterized by comprising a contact output means out.

Further, the contact output means is characterized in that it outputs a command for cutting off the connection with the interconnection bus when the state determination means determines that the private power generation equipment is operating independently.

Further, it is characterized in that it is provided with a contact output means for outputting a command for switching the plant operation control mode of the private power generation equipment when the status judging means judges that the private power generation equipment is in the independent operation.

[0018]

The on-site protective device of the present invention applies the inspection signal from the private power generation equipment side by the reference value changing means, and based on this signal, the synchronous power generation is performed based on the change of the terminal voltage of the synchronous generator and the change of the reactive power. The machine is equipped with a discriminating means for discriminating whether it is an independent operation or an interconnection operation, and in the case of an islanding operation, the circuit breaker can be opened to disconnect the connection with the interconnection bus bar by the contact output means. It is possible to reliably cut off the interconnection between the commercial power system and the private power generation facility side.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram showing an embodiment in which the in-house protection device of the present invention is applied to private power generation equipment. The output of the synchronous generator 12 provided in the private power generation facility 11 is supplied to the consumer load 13 and is also connected to the interconnection bus 16 via the power receiving breaker 14 and the parallel breaker 15. This interconnection bus 16 is connected to the commercial power system 18 via the interconnection breaker 17, and in this way the private power generation facility 11 and the commercial power system 18 are connected.
Will be connected to.

Further, the discrimination control device 19 for discriminating whether the private power generation equipment 11 is in the independent operation state or the parallel operation state is connected to the customer load bus 21 by the closing command of the circuit breaker operating means 20. Turn on the circuit breaker 22
Change the reference value by connecting 23. The current change of each part due to the circuit input of the reactor 23, that is, the current change of the interconnection bus 16 side, the synchronous generator 12 side and the customer load bus 21 side, is taken by the respective current transformers 24S, 24G, 24L.
A current change value detecting means 25S, 25G, 25L detects the current from and the state determining means 26 determines whether the operation is an isolated operation or a parallel operation based on the change value. As a result, private power generation facilities 11
When it is determined that the
A command for switching the plant operation control mode of the private power generation facility 11, for example, the terminal voltage and current of the synchronous generator 12 are output to the instrument transformer while outputting an opening command of the power receiving breaker 14 via 27. 28 and current transformer 29
The terminal voltage of the synchronous generator 12 is controlled to be constant by adjusting the field current of the field winding 30 of the synchronous generator 12 by the exciter 31. When operating, the terminal voltage of the synchronous generator 12 is determined by the voltage on the commercial power system 18 side separately from the set reference value, and therefore the power of the synchronous generator 12 is set by the automatic voltage regulator (AVR) 32. It is general to add an interconnection auxiliary control means 33 such as a method of keeping the rate constant or a method of keeping the reactive power constant, and the contact 34 is output as a command for releasing this.

Here, the closing command output from the circuit breaker operating means 20 is used for confirmation when the operator wants to confirm the operating state of the private power generation equipment 11 or for closing the circuit breaker 22 at a constant cycle. It will be opened after a certain period of time.

While the private power generation equipment 11 in the embodiment configured as described above is operating in parallel with the commercial power system 18, the reactor 23 is turned on by the circuit breaker operating means 20 of the discrimination control device 19. Consumer load bus 21
The relationship between the voltage and the current of each phase is as shown in FIG.

That is, the vector value of each phase current before the reactor 23 is turned on is The vector value of each phase current after turning on Then, the current after turning on is expressed by the following equation, ignoring the attenuation of the transient DC component.

[0024]

[Equation 1] here, Is the instantaneous DC value at the moment of making (zero time change) corresponding to the current change vector when the reactor 23 is turned on, which is the transient DC component. these Depends on the phase when the reactor 23 is turned on. Changes. However, since each phase is never zero, the maximum phase is extracted, And As can be seen from the vector in FIG. 2, the change amount of the AC component of the fundamental wave has a problem of detection accuracy due to the relation of the vector. Therefore, the method of detecting the DC component is adopted as described above, and the current of each part is set to the current transformer 29S for an instrument. , 29G, 29L and through the current change value detecting means 25S, 25G, 25L, that is, an analog filter for detecting the direct current component, or a digital filter that is arithmetically calculated from the maximum and minimum values of the instantaneous AC value. Thus, the DC components ΔIS, ΔIG, and ΔIL of each part of the private power generation equipment 11 at a certain time are detected and input to the state determination means 26.

When the private power generation equipment 11 is operating in parallel with the commercial power system 18, the synchronous generator of the private power generation equipment 11
Since the capacity of the commercial power system 18 is much larger than the capacity of 12, the relationship of the DC component is as follows.

[0026]

[Equation 2] On the other hand, in the isolated operation state in which the interconnection breaker 17 is opened, the following relationship is established when only the private power generation equipment 11 is operating.

[0027]

[Formula 3] ΔIS = 0, ΔIL = ΔIG Further, even in the above-mentioned single operation state, the private power generation equipment 11 is
Consider a case where a plurality of units are operating as in FIG.
In this case, if the capacity ratio of the other synchronous generators operating a plurality of units to the synchronous generator 12 is α and the operating number n, the following relationship is established.

[0028]

[Formula 4] ΔIS = Σ {n · αΔIG}, ΔIL = ΔIS + ΔIG Therefore, when three other units are operating with the same capacity,
When α = 1 and n = 3, ΔIS = 3 · ΔIG, ΔIL =
4 · ΔIG.

For such a case, it is considered that the number of operating other synchronous generators can be confirmed in advance by telephone or the like and input as a judgment condition to make the judgment surely and easily. In the state determination means 26,
ΔIS, ΔIG, and ΔI, which are the current change values of each part of 15
From the value of L, it is determined whether the operation is parallel operation or single operation based on the above relationship.

When it is determined to be the isolated operation, a signal for opening the power receiving breaker 14 is output through the contact output means 27 to prevent the isolated operation. In addition, the auxiliary active power and reactive power control modes required when the private power generation facility 11 operates in parallel with the commercial power system 18 are released via the contact 34. For example, the automatic power factor control (APFR) or the automatic reactive power control (AQR) is canceled as the reactive power control.

As described above, in this embodiment, the input / output competition is within the range of various quantities that have been conventionally used in private power generation equipment, and is not a special one. It is possible to accurately determine the operating state based only on the fact that active power is not consumed unlike resistors and the like, and the magnitude of these changes. In addition, by shutting off the interconnection with the commercial power system during the islanding operation, the inside of the private power generation facility can be protected.

As described above, according to the present invention, the private power generation equipment side determines whether it is the independent operation or the parallel operation with the commercial power system, and when the independent operation is performed, the grid connection with the commercial power is cut off for private use. The inside of the power generation facility can be protected.

[0033]

As described above, according to the present invention, a reactor or a carrier wave transmission device, a neutral point grounding open circuit, a power factor or a reactive power is connected to a customer load bus of a private power generation facility operating in parallel with a commercial power system. Since the voltage change amount detecting means is provided and the individual operation of the private power generation equipment is determined by detecting each change amount, the simple configuration is based on only the own place information and without the consumption of active power. It is possible to provide an in-plant protection device that can accurately determine an isolated operation state and prevent this.

[Brief description of drawings]

FIG. 1 is a block configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a voltage and current vector diagram showing a detection target of the current change value detection means of the present invention.

FIG. 3 is a system diagram in which a private power generation facility is connected to a commercial power system.

FIG. 4 is a conceptual system diagram when a transfer blocking method is applied.

[Explanation of symbols] 11 ... Private power generation equipment, 12 ... Synchronous generator, 13 ... Customer load, 14 ... Power receiving circuit breaker, 15 ... Parallel circuit breaker, 16 ... Interconnection busbar,
17 ... Interconnection circuit breaker, 18 ... Commercial power system, 19 ... Discrimination control device, 20 ... Circuit breaker operating means, 21 ... Consumer load busbar, 22 ... Circuit breaker, 23 ... Reactor, 24, 29 ... Current transformer for instrument 25, ... Current change value detecting means, 26 ... State determining means, 27 ... Contact output means, 28 ... Instrument transformer, 30 ... Field winding, 31 ... Excitation device,
32 ... Automatic voltage adjusting device, 33 ... Interconnection auxiliary control means, 34 ... Contact point, 35 ... Grid load equipment, 36 ... Customer load equipment, 37 ... Circuit breaker information transmitter, 38 ... Transfer breaker, 39 ... Breaker Instrument information receiver, 40 ... Transfer line.

Claims (3)

[Claims] 1. A commercial power system is connected to an interconnection busbar via an interconnection circuit breaker, and a private power generation facility having a synchronous generator is connected to the interconnection busbar via a parallel circuit breaker, and the commercial power system is connected. In the in-house protection device in the private power generation equipment that performs parallel operation with the private power generation equipment, an inspection signal for the reference value of the terminal voltage of the automatic voltage regulator for controlling the terminal voltage and reactive power of the synchronous generator. And a reference value changing means for applying the inspection signal, and a private power generation facility to which the synchronous generator belongs based on a change in the terminal voltage of the synchronous generator and a change in the reactive power when the inspection signal is applied is operated independently or in the commercial state. A state determining means for determining whether it is an interconnected operation with the electric power system, and for disconnecting the connection with the interconnecting bus when the state determining means determines that the private power generation equipment is operating independently. An on-site protection device comprising contact output means for issuing a command. 2. The contact output means outputs a command for cutting off the connection with the interconnection bus when the state determination means determines that the private power generation facility is in an isolated operation. The in-house protection device according to claim 1. 3. The contact output means for outputting a command to switch the plant operation control mode of the private power generation equipment when the status determination means determines that the private power generation equipment is operating independently. The in-house protection device according to claim 1.