JPS596572B2 - 3 phase capacitor switchgear - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a three-phase capacitor switching device that opens and closes a three-phase capacitor using a thyristor switch configured by an anti-parallel connection of a thyristor and a diode.

FIG. 1 shows a conventional three-phase capacitor switchgear.

In the figure, three-phase capacitors 3a, 3b, and 3c are connected to the secondary side of the △/man transformer 1 via a series reactor 2, and three-phase capacitors 3, 4, and 5 are connected in series for switching. thyristor switches 6, T, and 8 are connected. Thyristor switches 6, T, 8 are thyristors 6a, 7a,
It consists of Ba and diodes 6b, Tb, and 8b connected in antiparallel. In addition, the series reactor 2 is generally of a three-phase iron core structure, and is approximately 6% of the KVA capacity of the capacitors 3, 4, and 5 to prevent resonance with the impedance on the power supply side.
capacity is used. Thyristor switch 6
, T, and 8 are off, capacitors 3, 4, and 5 are charged to the peak value of the power supply voltage through diodes 6b, Tb, and 8b, and their polarities are as shown in FIG. When capacitors 3, 4, and 5 are turned on, the thyristors are fired in a phase in which the voltage across thyristor switches 6, 7, and 8 becomes o to prevent inrush current, and thyristor switches 6, T, and 8 are turned on. That's what I do. For this reason,
As shown in FIG. 2, the thyristors 6a, Ta, of each phase are synchronized with the negative peak phase of the power supply voltage;
Make Ba conductive and turn on thyristor switches 6, 7, and 8.
I try to do that. Therefore, as is clear from Fig. 2, the capacitors 3, 4, and 5 are not turned on at the same time, but the period from when the first phase capacitor 3 is turned on until the other capacitors 4 and 5 are turned on is As a result, 2/3 cycles are required. During this 2/3 cycle period, the three-phase unbalanced state occurs, and the zero-sequence current returns to the transformer neutral point through the neutral wire. In this case, the neutral wire current flows for 2/3 cycle period as shown in Figure 2h, so if the capacitor is frequently connected and closed, the neutral wire current cannot be ignored, so a relatively thick conductor is used. It has the disadvantage of requiring In addition, series reactors are generally of a three-phase iron core structure, but since zero-sequence current flows when the capacitor is opened and closed, the magnetic flux cannot be canceled between the three phases.
When used in a three-phase balanced state, a phenomenon occurs in which the specific vane tag resistance decreases, and there is also a risk that resonance with the impedance on the power supply side may occur. This invention was made in order to eliminate the above-mentioned drawbacks, and by making the thyristor switch of one of the three phases have the opposite polarity to that of the other thyristor switches, it is possible to shorten the capacitor closing time and The object of the present invention is to provide a three-phase capacitor switching device that can improve responsiveness when compensating for reactive power.

The figures will be explained below.

As shown in FIG. 3, 1fC, 1 is a transformer, which is configured to be Δ/in. 2 is a reactor connected in series with the secondary side of the transformer 1, and may be substituted by the impedance of the winding of the transformer 1.

3 to 5 are capacitors connected to the secondary side of the transformer 1 via the reactor 2, and 6 to 8 are connected to the secondary side of the transformer 1 via the reactor 2 and each of the capacitors 3 to 5. thyristors 6a, 7a, 8a and Da Hayabusa. iode 6b
, 7b, and 8b are connected in antiparallel.

Note that the W-phase thyristor 8a and the diode 8b
The polarity of each of the U-phase and phase thyristors 6a and 7a is
The polarity of the diodes 6b and 7b is opposite to that of the diodes 6b and 7b. Next, the operation will be explained.

Figure 3
At F time, each of the capacitors 3 to 5 is charged to the polarity shown. As a result, as shown in FIG. 4, the voltage of the W-phase thyristor switch 8 is in the opposite direction to that of the U-phase and V-phase thyristor switches 6, 7, and the voltage of the U-phase and V-phase capacitors 3, 4 is turned on at the negative peak phase of the power supply voltage, whereas the W-phase capacitor 5 is turned on at the positive peak phase of the source voltage. It becomes.

In this case, the order in which the capacitors 3, 4, and 5 are connected is the U phase -
The order is W phase - V phase, and as shown in FIG. 4, the period from when capacitor 3 of the first phase is turned on to when capacitors 3 to 5 of all three phases are turned on is 1/3 cycle.
It can be shortened to 1/2 of the conventional method. Furthermore, the current flowing through the neutral wire is for a 1/3 cycle period as shown in FIG. FIG. 5 shows a two-bank three-phase capacitor switchgear.

△/3-phase capacitors 3, 4, 5 and thyristor switch 6, via series reactor 2 on the secondary side of transformer 1
7 and 8 are connected. Further, three-phase capacitors 9, 10, 11 and thyristor switches 12, 13, 14 are connected via a series reactor 8. Of these, the configuration of the first capacitor bag 15 connected via the series reactor 2 is the same as that of the first specific example of the present invention.
Thyristor switches 12, 1 of the second capacitor bags 1, 6 connected via the other series reactor 8
The polarities of capacitors 3 and 14 are opposite to that of the first capacitor bag 15. For this reason, each capacitor 3 to 5 when each thyristor switch is 6 to 8, 12 to 140FF,
The charging polarities of 9 to 11 are as shown in the figure. In this case, the order in which the capacitors are connected is as shown in Figure 6.
The capacitor bag 15 uses the negative peak phase of the U-phase voltage as the closing phase of the first phase capacitor 3, and then the U-phase-W
The phase-V phase is turned on in the order of 1/3 cycle period. or,
In the second capacitor bag 16, the positive peak phase of the U-phase voltage is used as the closing phase of the first phase capacitor 9, and then,
The U-phase, W-phase, and V-phase are turned on in the order of 1/3 cycle period. As is clear from this, since the first capacitor bank 15 and the second capacitor bag 16 have a difference in the closing phase of 18(5), the first capacitor bank 15
and the second capacitor bank 16 as a pair, the peak phase of either the positive side or the negative side of the U-phase voltage after the capacitor closing command is input, whichever comes first [whichever reaches the closing phase] It is now possible to input the capacitor from the capacitor bank, and the capacitor can be opened and closed twice per cycle, improving responsiveness. In addition, in the above embodiment, the U phase-W
Although the case has been described in which the capacitors are turned on during a 1/3 cycle period in the order of phase-V phase, the order of turning on can be arbitrarily selected by changing the polarity of the thyristor switch of each phase.

According to this invention, by setting the thyristor switch of one phase among the three phases to have the opposite polarity to the other thyristor switches, the time for turning on the capacitor can be shortened, and the period of the three-phase unbalanced state can be shortened. The period during which the inductance of the reactor decreases can be shortened, and the risk of resonance can be reduced.

In addition, when compensating reactive power for a three-phase fluctuating load,
Responsiveness during compensation can be improved. Furthermore, the effective value of the current flowing through the neutral wire is almost 1 compared to the conventional one, so the conductor size of the neutral wire can be reduced.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram showing a conventional three-phase capacitor switchgear.
Figure 2 is an explanatory diagram showing the waveforms at each part of Figure 1;
FIG. 4 is an explanatory diagram showing waveforms of each part of FIG. 3, FIG. 5 is a configuration diagram showing another embodiment of the invention, and FIG. FIG. 5 is an explanatory diagram showing waveforms of each part in FIG. 5;

Claims (1)

[Claims] 1. A thyristor switch consisting of an anti-parallel connection of a thyristor and a diode is connected to each phase on the secondary side of a three-phase transformer via a reactor and a capacitor, in which one of the three phases A three-phase capacitor switching device characterized in that the polarity of the thyristor and the diode of the thyristor switch connected to one phase is opposite to the polarity of the other thyristor switch. 2. The three-phase capacitor switchgear according to claim 1, wherein the reactor is replaced by the impedance of a winding of a three-phase transformer. 3 A thyristor switch consisting of an anti-parallel connection of a thyristor and a diode is connected to each phase of the secondary side of a three-phase transformer via a reactor and a capacitor, and the switch is connected to one of the three phases. A first one in which the polarity of the thyristor and the diode of the thyristor switch is opposite to the polarity of the other thyristor switch.
and a second capacitor bank having the thyristors and diodes that correspond to the thyristors and diodes of the first bank and are connected in opposite polarity to the first bank. A three-phase capacitor switching device comprising: