JPH0218570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a three-phase load switch capable of detecting zero-phase voltage.

The conventional one is shown in Figs. 1 and 2,
A ring-shaped metal electrode 8 or an electrode 8 made of a metal layer deposited on the insulating member 6 is arranged around the insulating member 6 that insulates the conductor 4 on the power transmission system side, and the electrodes 8 of each phase are connected. It is used as a detection terminal 14. The capacitance between each electrode 8 and each conductor 4 is used to detect a zero-sequence voltage resulting from an imbalance in each relative ground voltage.

In such a configuration, the capacitance between the conductor 4 to which a high voltage is applied and the electrode 8 is very small, about 100 PF. Therefore, it is affected by manufacturing errors of conductors, insulating members, electrodes, etc., and variations in relative permittivity of insulating members. Therefore, depending on the magnitude of each error, a residual zero-sequence voltage (error voltage) may occur even though the relative ground voltages are balanced. Furthermore, if the insulating member is used in a poor atmosphere and becomes dirty or has condensation, the outer circumferential surface of the insulating member becomes conductive, which causes the potential on the electrode to fluctuate due to leakage resistance.

This invention was made in view of the above, and the first
A first electrode facing the conductor via an insulating member is sealed with a second insulating member, a pair of electrodes are arranged at a predetermined distance from each end of the second electrode, and the second electrode is grounded. By configuring this, a three-phase load switch is provided that can accurately detect zero-phase voltage even when used in a bad atmosphere.

The figures will be explained below. In Figures 3 to 5, 1 is a container, 2 is a fixed contact placed in the container 1, 3 is a movable contact placed in the container 1 and makes contact with and separates from the fixed contact 2, and 4 is connected to the fixed contact 2. The conductor is led out to the outside of the container 1. 5 is a conductor connected to the movable contact 3 and led out to the outside of the container 1. 6 is an insulating member surrounding the conductor 4;
It is fixed to container 1. An insulating member 7 surrounds the conductor 5 and is fixed to the container 1. 8 is an insulating member 7 facing the conductor 5 and having a predetermined length (A).
9 and 10 are a pair of ground electrodes arranged on the outer periphery of the insulating member 7 at a predetermined distance from the detection electrode 8; A grounding wire that grounds the grounding electrodes 9 and 10, 12 an insulating tube placed over the outer periphery of the detection electrode 8, 13 a sealing agent packed between the insulating tube 12 and the insulating member 7, and 14 detecting each phase. A detection terminal connected between electrodes 8, 15 is a zero-phase voltage detector equipped with a voltage dividing capacitor 15a,
It is connected to the detection terminal 14.

In the above configuration, a zero-sequence voltage consisting of a vector sum of ground voltages of each phase is input to the zero-sequence voltage detector 15 via the detection terminal 14, and leakage current from the conductor 5 charged to a high voltage is transmitted to the ground electrode 9. , 10, the zero-sequence voltage can be detected with high accuracy.

In the embodiment of FIG. 3, if the container 1 is grounded, the ground electrode 10 may be omitted.

In addition, since the first electrode 8 is made of a tape-shaped metal foil, the conductor 5 and the insulating member 7 are not easily connected to each other due to the influence of errors in the sizing method when manufacturing the conductor 5 and the insulating member 7, and variations in the dielectric constant of the insulating member 7. In order to prevent an error voltage from appearing on the first electrode 8 due to the difference in capacitance between the three phases and the first electrode 8,
By adjusting the winding width A on the metal foil insulating member 7 of the first electrode 8 under the condition of constant voltage application in advance so that the detection voltage of each of the three phases is constant, it is possible to Even if the capacitance is small and the absolute value of the detected voltage is very small, it is possible to provide a three-phase zero-phase voltage detector with high accuracy and small residual error output.

Further, in the above embodiment, the detection electrode 8 was described as facing the conductor 5 connected to the movable contact 3, but it may be configured so as to face the conductor 4 connected to the fixed contact 2.

According to this invention, the first electrode is arranged via the conductor connected to the first contact and the first insulating member, and the second electrode is arranged at a predetermined distance from each end of the first electrode. By connecting the first electrodes of each phase and sealing each first electrode with a second insulating member, the influence of leakage current can be removed, and the first electrode can be grounded. By forming the tape-shaped metal foil and winding it while adjusting the voltage detection sensitivity to a predetermined value, it is possible to detect zero-sequence voltage with high accuracy.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional three-phase load switch, FIG. 2 is a sectional view taken along the - line in FIG. 1, and FIG. 3 is a partially cutaway plan view of an embodiment of the present invention.
4 is a sectional view showing the main part of FIG. 3, and FIG. 5 is a sectional view showing the main part of FIG. 4. In the figure, 2
is a fixed contact, 3 is a movable contact, 5 is a conductor, 7 is an insulating member, 8 is a detection electrode, 9 and 10 are ground electrodes, 12
is an insulating tube, and 13 is a sealant. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A first contact and a second contact are configured to be connectable and detachable for each of the three phases, and a conductor connected to the first contact is surrounded by a first insulating member. A first electrode of a predetermined length facing the conductor is tightly attached to the outer periphery of the first insulating member, and the first electrode of each phase is connected to the first electrode of a predetermined length.
A device for detecting a zero-sequence voltage consisting of a vector sum of charging potentials of each phase by connecting the electrodes of the first electrode, the outer periphery of the first electrode is surrounded and sealed with a second insulating member, and the first electrode is sealed. A three-phase load switch, characterized in that a pair of second electrodes are disposed at predetermined distances from each end of the electrodes, surrounding the outer periphery of the first insulating member, and closely contacting and grounding the second electrodes. 2. The three-phase load switch according to claim 1, wherein the first electrode is formed of a tape-shaped member whose length is adjustable and faces the conductor.