JPH0113407Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a capacitor device in which a plurality of case-shaped unit capacitors are assembled on one pedestal and connected in a double star shape to form a capacitor bank.

[Technical background of the invention and its problems]

Power capacitors are widely used to improve the power factor of power transmission and distribution lines, adjust voltage, etc., but multiple relatively small-capacity case-type capacitors are assembled and connected together as a unit capacitor to achieve a predetermined capacitance. There is a capacitor bank configured as follows.

In this capacitor bank, in order to protect the bank, the unit capacitors in the bank are connected in a double star shape, and a current transformer is inserted between the neutral points to detect failures in the unit capacitors.

Conventionally, as shown in Figure 1, in a capacitor bank in which case-type unit capacitors are assembled and connected in a double star shape, two
A plurality of unit capacitors 1 equipped with the bushings 5a and 5b are assembled on one pedestal 3, and two
They are connected in a double star shape. and a current transformer 2 between the neutral point
was connected to perform protection detection. When using a capacitor bank with such a configuration on a power transmission line in a directly grounded system, in the unlikely event that a ground fault occurs inside the case 1a of the unit capacitor 1, the discharge type connected to each unit capacitor 1 Since the fuse 4 does not limit the flow of a large ground fault current, there is a risk that the case 1a of the unit capacitor 1 will be destroyed. Therefore, the pedestal 3 is supported by insulating support insulators 7, and the case 1a of the unit capacitor 1 is insulated from the ground to prevent a ground fault in the system even if a ground fault occurs inside the case 1a. was. In such a capacitor bank, of the two bushings of the unit capacitor 1, the bushing 5a connected to the line side is always applied with a voltage equivalent to the phase voltage, and therefore requires a predetermined high withstand voltage value. However, almost no voltage is always applied to the bushing 5b connected to the neutral point side,
Further, even in the event of a failure, only a small voltage is applied, and the withstand voltage is gentler than that of the bushing 5a on the line side. Nevertheless, since bushings of the same rating are used, excessive insulation is required, resulting in high costs.

[Purpose of invention]

The object of the present invention is to eliminate the above-mentioned conventional drawbacks, and to obtain an inexpensive capacitor device that can completely protect a unit capacitor even when used in a direct grounding system.

[Summary of the idea]

In order to achieve the above object, the present invention provides a capacitor device in which a plurality of unit capacitors are assembled on one stand and connected in a double star shape.
By making the withstand voltage value of the bushing connected to the neutral point side of each unit capacitor smaller than the withstand voltage value of the bushing connected to the line side, excessive insulation of the bushing on the neutral point side is suppressed. It is characterized by

[Example of idea]

An embodiment of the present invention will be described below with reference to the drawings. Fig. 2 shows a capacitor device according to the present invention, in which a plurality of unit capacitors 1 are assembled on a single pedestal 3, and the bushing 5a of each unit capacitor 1 is on the line side, the bushing 5c is on the neutral point side, and a double star is constructed. A current transformer 2 for protecting the capacitor bank is connected between the neutral points. 6 is a bank protection relay.

In such a capacitor bank, the bushing 5a connected to the line side of the unit capacitor 1 is always applied with phase voltage, but the bushing 5b connected to the neutral point side is connected between the neutral points of the double star-shaped connection. Since it is connected, almost no voltage is applied,
Even if the unit capacitor 1 fails, the terminal voltage of the current transformer 2 is only applied, and the insulation of the bushing insulator is sufficient as long as it has the effect of insulating between the terminals of the current transformer 2. Therefore, a small bushing 5c having a lower withstand voltage value than the line-side bushing 5a shown in FIG. 2 can sufficiently achieve its function.

In this way, by making the neutral point side bushing 5c of the unit capacitor 1 a small bushing with a low withstand voltage value, the mount 3 becomes lightweight, and the unit capacitor can be manufactured at low cost.

Furthermore, as shown in Fig. 3, the unit capacitor of the present invention is applied only to one side of the double star connection, and the other unit capacitor is connected to the bushing 5a.
A similar effect can be obtained even if a unit capacitor 1b is used in which only one terminal is attached and the other terminal is set to the case potential at the connection part 8.

[Effect of idea]

As described above, according to the present invention, in a device in which a plurality of unit capacitors are assembled on one stand and connected in a double star shape, the withstand voltage value of the bushing connected to the neutral point side of each unit capacitor is determined. Since the withstand voltage value is made smaller than the withstand voltage value of the bushing connected to the line side, even when used directly in a grounding system, the unit capacitor can be completely protected and an inexpensive capacitor device can be obtained.

[Brief explanation of the drawing]

Figure 1 is a front view showing a conventional capacitor device.
Figure 2 is a front view of the capacitor device according to the present invention;
FIG. 3 is a front view showing another embodiment of the present invention. 1...Unit capacitor, 1a...Case,
2... Current transformer, 3... Frame, 4... Discharge type fuse, 5a, 5b, 5c... Bushing, 6... Protective relay, 7... Support insulator.

Claims (1)

[Scope of utility model registration request] In a capacitor device in which a plurality of unit capacitors are installed on one stand and connected in a double star shape, the withstand voltage value of the bushing connected to the neutral point side of each unit capacitor is the same as that of the bushing connected to the line side. A capacitor device characterized by having a lower withstand voltage value.