JPS61221523A - Apparatus for linking small-capacity generation system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to an interconnection device for a small-capacity power generation system.

B0 Summary of the Invention The present invention provides an interconnection device for a small-capacity power generation system configured to interconnect a small-capacity power generation device and a distribution system to supply power to a load. An overcurrent relay that operates faster than an overcurrent relay installed in the distribution system is installed on the electrical circuit connecting the circuit breaker for the grid, and when the overcurrent relay operates, the circuit breaker for interconnection is shut off, and the circuit breaker is cut off. an automatic reclosing relay that issues an official command to the circuit breaker when a vector difference between the distribution system voltage and the output voltage of the small capacity generator is less than or equal to a set value after a predetermined set time has elapsed since the circuit breaker was shut off; By installing a small-capacity power generation facility, it is possible to connect the small-capacity power generation equipment to the existing power distribution system without changing the equipment of the existing power distribution system, and even if a short-circuit accident occurs, it will not have a negative impact on the small-capacity power generation facility or the system. I decided not to give it to anyone.

C0 Conventional technology In recent years, the demand for electricity has been increasing, but the currently mainstream nuclear and thermal power generation systems are
There are restrictions in terms of sources, installation locations, etc. For this reason, fuel cell power generation systems are attracting attention because they can be distributed across power consumption areas, are non-polluting, and have high power generation efficiency. For distributed deployment, the most economical method for small-scale power generation systems is to connect to the load end of the existing distribution system.

Problems to be solved by the D0 invention However, since it is related to the protection method and control method of the existing power distribution system, it is difficult to use the parallel operation control method of the conventional power generation equipment and the power distribution system, or the protection control of the private power generation system. Manshiki could not be applied as is.

That is, for example, a conventional parallel operation system between large-scale power generation facilities has a configuration in which they are connected not by a power distribution system but by a nearly dedicated power transmission system.

In such a revolutionary parallel operation system, each power plant has equipment with the protective control functions necessary for parallel operation (synchronization detection, synchronization official, out-of-sync detection, etc.), and the power transmission system also has equipment to prevent out-of-synchronization. Protection control equipment is installed that can respond to frequency fluctuations, etc. However, when connecting a small-scale power generation system to an existing power distribution system, not only does the distribution system lack a synchronization confirmation function, but it also requires control devices specific to the power distribution system, such as automatic reclosing devices and fault section indicators. Because of this, it was not possible to apply the conventional interconnection method between power plants as is.

Here, in a system in which a power distribution system and a small-capacity power generation facility are interconnected, problems when short-circuit protection is provided by an overcurrent relay will be explained with reference to the circuit diagram shown in FIG. 4. In Figure 1g4, it is assumed that the primary side of the transformer T is connected to an AC power source (not shown).

The secondary side of transformer 4iT is connected to AC bus 1 via circuit breaker OBo.
It is connected to the. OB, % CBn are power distribution lines (hereinafter referred to as feeders) IF1 to Fn and the AC bus IIl! which are installed in parallel. These circuit breakers are respectively inserted in the electric circuits connecting the circuits 1 and 1. The AC output power of the AC power supply (not shown) is
Transformer T, circuit breaker CB, , AC mother Ill, circuit breaker O
It is supplied to a load (not shown) via B, ~OBn and feeders IF, -Fn. 2 is a small capacity power generation device,
For example, it is composed of a fuel cell power generation device and an inverter (not shown) that converts its DC output power to AC. The AC output power of this small capacity power generation device 2 is transmitted to the overcurrent relay 51.
The circuit breakers Ca, X and the feeder which are cut off during operation of ? , to a load (not shown). The overcurrent relay 51 is operated by the output current of the current transformer OT0 inserted in the electric line connecting the small-capacity power generation device 2 and the circuit breaker OB. The feeder FIEFn has a current transformer CT, % O'
l'n are provided respectively. Overcurrent relay 511Fl
-51yn is a current transformer OT.

The circuit breaker OB is operated by each output current of ~a'rn.

~cBn respectively. 7971-79Fn are re-closing relays for re-closing the circuit breakers OB and %ORn, respectively.

Using the device configured as described above, during parallel operation, feeder F, point A on top, and point B on current transformer al.

Feeder F′! If a short-circuit accident occurs at the above point 0 and point D on the electric line connecting the small-capacity power generator 2 and the circuit breaker OB, the following situation will occur.

(1) When a short-circuit accident occurs at point A, short-circuit current flows from both the small-capacity power generation device 2 and the power grid side.

Therefore, the overcurrent relay 51 shuts off the circuit breaker OB, and the overcurrent relay 51Fm shuts off the circuit breaker CB. There is no problem in this case.

(2) When a short-circuit accident occurs at point B and point 0, a short-circuit current flows from both the small-capacity power generation system #t2 and the power grid, as in the above-mentioned (1). At this time, overcurrent relay 5 on the grid side
When 1F* operates earlier than the overcurrent relay 51 on the small capacity power generator 2 side, the fault current disappears due to the interruption of the circuit breaker OB, and the load connected to the feeder F1 (not shown)
If is small, the overcurrent relay 51 will return to its normal state. For this reason, since the circuit breaker OB is not shut off, power supply from the small capacity power generation device 2 continues, and the power supply voltage on the power system side and the output voltage of the small capacity power generation device 2 become asynchronous.

In this state, when the re-closing relay 79F'* operates after a predetermined period of time and the circuit breaker OB is re-closed, an excessive current flows between the power system and the small-capacity power generation device 2.

For this reason, the small-capacity power generation device 2 and the power system will be adversely affected.

(3) Even if a short circuit accident occurs at point D, a short circuit current flows from the power system through circuit breaker CB and CIB, but at this time, if overcurrent relay 51P1 operates earlier than overcurrent relay 51, overcurrent relay 51 will return. For this reason, a problem similar to the above-mentioned item (2) arises.

The present invention has been made in view of the above points, and allows small-capacity power generation equipment to be connected to the existing power distribution system without changing the equipment of the existing power distribution system, and moreover, it is possible to prevent short-circuit accidents from occurring. The purpose of the present invention is to provide an interconnection device for a small-capacity power generation system that does not adversely affect small-capacity power generation equipment or the grid.

Means for Solving Problem E1 The present invention provides an interconnection device for a small-capacity power generation system configured to interconnect a small-capacity power generation device and a power distribution system to supply power to a load. A circuit breaker inserted in an electric line connecting a distribution line and a small-capacity power generator, a current detector inserted in an electric line connecting this breaker and the small-capacity power generator, and an operating time of a circuit breaker of the power distribution system. an overcurrent relay that is set faster than the operating time of an overcurrent relay provided in the circuit breaker, and responds to the output of the current detector to issue a shutdown command to the circuit breaker; and an automatic reclosing relay that issues a closing command to the circuit breaker when the vector difference between the distribution system voltage and the output voltage of the small-capacity power generation device is less than or equal to a set value after a set time has elapsed. .

70 Action If a short circuit accident occurs in a device configured as described above, the overcurrent relay on the small-capacity generator side will operate faster than the overcurrent relay on the distribution system side, so the circuit breaker will surely interrupt the trip. be done. Furthermore, after a predetermined set time has elapsed after the circuit breaker has been disconnected, the circuit breaker is reclosed on the condition that the vector difference between the distribution system voltage and the output voltage of the small capacity power generation device is less than or equal to the set value. Ru. For this reason, small-capacity power generation equipment does not remain disconnected from the power grid.
The operating rate of the power generation equipment improves.

G. Embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the same parts as in FIG. 4 are shown with the same reference numerals, and the explanation thereof will be omitted. A current detector, for example, a current transformer C, is installed in the electric line connecting the circuit breaker former worker and the small-capacity power generation device 2.
To is inserted.

An overcurrent relay 511 is connected to the secondary side of the current transformer CTo, which gives a disconnection command to the circuit breaker alumnus. The operating time of the overcurrent relay 51 installed on the feeder F1 side is as shown in the characteristic diagram of FIG.
Set it faster than the Fm operation time. 79, when the vector difference between the distribution system voltage and the output voltage of the small-capacity generator is equal to or less than a set value after a predetermined set time has elapsed since the breaker OB was disconnected, the circuit breaker OB is disconnected. This is an automatic reclosing relay that gives a closing command. This automatic reclosing circuit 1/79 includes, for example, a vector difference voltage check [111] which issues an output signal when the vector difference between the grid voltage and the voltage on the generator side is less than a predetermined set value, as shown in FIG. A timer 12 that issues an output signal after a predetermined set time has elapsed since the CB circuit breaker is shut off; and a closing command to the CB circuit breaker when the AND condition of the output signals of the vector difference voltage confirmation unit 11 and the timer 12 is satisfied. It is composed of an AND circuit 13. The set time of the timer 12 is determined by the re-closing relay 79F+ provided on the power distribution system side.
Set it to be larger than one cycle time of 79Fn.

Next, the operation of the apparatus configured as described above will be described.

(1) When a short circuit accident occurs at point B and point 0, overcurrent relay 51 operates faster than overcurrent relay 51F+, and circuit breaker CB is shut off. After that, if there is a short-circuit accident at point B, the cutoff 10Bo is cut off and the feeder? , is not reclosed. Further, in the case of a zero-point short circuit accident, the feeder F returns to its normal state after the circuit breaker OB is cut off by the overcurrent relay 511'*. And on the feeder h side, the reclosing relay 79? , by circuit breaker OB,
An attempt is made to reclose the circuit. If the re-closing is successful, the operating conditions for the automatic re-closing relay 79 are established after one period of the re-closing relay 79F1 has elapsed. For this reason, the circuit breaker alumnus is turned on again and the normal state is restored.

(2) Even if a short circuit accident occurs at point D, the overcurrent relay 5
11 operates earlier than the overcurrent relay 51F1 and the circuit breaker CB is cut off, so the feeder F is not affected at all. In this case, on the small-capacity power generation device 2 side, the inverter (not shown) is stopped by a control device (not shown), and then the ground fault is removed. In this way, the output of the small-capacity power generation device 2 becomes non-voltage, so the operating conditions for the automatic re-closing relay 791 are not satisfied, and the circuit breaker CB is not re-closed.

(2) Effects of the Invention As described above, according to the present invention, the following effects can be obtained. Namely.

(1) A small-capacity power generation device and an existing power distribution system can be interconnected without changing the equipment of the existing power distribution system.

(2) When a short-circuit accident occurs on an AC bus of a power distribution system or a distribution line to which a small-capacity power generation device is connected, the interconnection circuit breaker can be reliably shut off. Moreover, the circuit breaker is reclosed only after it is confirmed that the vector difference between the grid voltage and the output voltage of the small-capacity generator is less than the set value. does not flow. Therefore, there is no adverse effect on the electric power system or the equipment of the small-capacity power generation device.

(3) When a short circuit occurs on a distribution line connected to a small-capacity power generation device or on an AC bus on the grid side, the interconnection circuit breaker will not be reclosed, so there will be no negative impact on the grid or small-capacity power generation device.

(4) If a short-circuit accident occurs on a distribution line other than the distribution line interconnected with the small-capacity power generation equipment, the interconnection circuit breaker will be shut off, but it will automatically shut off after the distribution line has been reclosed. The recloser relay closes the interconnection circuit breaker again.

For this reason, the small capacity power generation device will not remain disconnected. Furthermore, since the power is automatically re-energized, there is no need for a troublesome manual re-energizing operation, and the operating rate of the small-capacity power generation device is improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a relay operating time characteristic diagram for explaining the present invention in detail, FIG. 3 is a block diagram showing the main parts of the present invention, and FIG. FIG. 4 is a circuit diagram showing an example of a conventional interconnection device for a small-capacity power generation system. OT0~OTn...Current transformer, 2...Small capacity power generator, OB engineer, OB0~OBn...Breaker, 511...
・Overcurrent relay, 79 works...Automatic reclosing relay, ? ,
~Fn...Feeder. Figure 2: VtMF Sakiru, Kametsu, Kame Figure 3: F''J:+77 Figure

Claims (1)

[Claims] In a interconnection device for a small-capacity power generation system configured to interconnect a small-capacity power generation device and a distribution system to supply power to a load, the power generation device is inserted into an electric line connecting the distribution line of the distribution system and the small-capacity power generation device. a current detector inserted in an electric line connecting the circuit breaker and the small-capacity power generating device; and an overcurrent relay that responds to the output of the current detector and gives a cutoff command to the circuit breaker, and an overcurrent relay that responds to the output of the current detector and issues a cutoff command to the circuit breaker, and a relay that controls the voltage of the distribution system after a predetermined set time elapses after the circuit breaker is cut off 1. An interconnection device for a small capacity power generation system, comprising: an automatic reclosing relay that gives a closing command to the circuit breaker when a vector difference between the output voltage and the output voltage of the small capacity power generation device is less than a set value.