JPS6260406A - Gas insulated current transformer - 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] [Technical Field of the Invention] The present invention relates to a gas-insulated current transformer that is directly connected to electrical equipment such as a sealed gas-insulated switchgear, and particularly to a gas-insulated current transformer that protects the primary coil outlet from abnormal voltage. This invention relates to an improvement in the outlet section with a surge protection structure for the purpose of protecting against surges.

[Technical background of the invention and its problems 1 As is well known, when electrical equipment is installed on-site, closed-type gas-insulated switchgear has been widely adopted in recent years due to the compactness and downsizing of the switchyard due to the advanced use of land and disaster prevention. This is becoming more and more common. As a current transformer directly connected to such a gas-insulated switchgear, a feed-through current transformer is generally employed in which the main circuit conductor of the system is directly used as the primary coil.

However, this feed-through current transformer often fails to provide desired characteristics when the current transformation ratio is low or when it is used for power trading. For this reason, in such cases, winding type gas insulated current transformers in which the high voltage primary conductor has a number of turns of several turns have come to be used. Generally, in this type of gas insulated current transformer, the number of turns of the primary coil is several turns as described above, and the potential difference between the primary coil and the output terminal is about several volts. Therefore, a small insulation distance between the coils of the primary coil and between the output terminals is sufficient. However, since such a gas-insulated current transformer is connected in series to the internal bus bar of the gas-insulated switchgear, it may cause sudden surges in the event of a surge voltage due to disconnection or a ground fault inside the gas-insulated switchgear. Surge current enters the primary terminals of the current transformer. When such a steep surge current enters, an abnormally high reflected voltage is applied to the primary coil. This is because the surge impedance of the current transformer is high, and most of the surge impedance is the internal inductance of the current transformer. If abnormal voltage occurs in a gas-insulated current transformer due to such surges, there is a risk of breakdown of the insulation between the primary coils and creepage breakdown between the outlet terminals supported by the insulating spacer, and even damage to the current transformer itself. There is a risk that this may lead to internal short-circuit accidents, etc. In order to protect the current transformer from abnormal voltages caused by these surges, it is necessary to reinforce the insulation between the coils and increase the creepage distance of the output terminals, but this has the disadvantage of increasing the size. be.

[Object of the Invention] In view of the above points, the present invention provides a highly reliable gas-insulated current transformer that protects equipment from abnormal voltages caused by surges, prevents insulation breakdown and internal short-circuit accidents, and is highly reliable. The purpose is

[Summary of the Invention] In order to achieve the above object, the present invention provides a gas insulated switchgear by providing a non-linear resistance element made of a metal oxide in an insulating spacer part that supports the primary coil output terminal part of a gas insulated current transformer. The current transformer is characterized by absorbing abnormal voltage caused by surges from the current transformer and preventing abnormal voltage from entering inside the current transformer.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In Figures 1 and 2, a secondary coil 2 is wound around the outer periphery of an annular iron core 1, and a primary coil 3 formed into a ring by winding one or more conductors multiple times is arranged at the interlinking part. Both ends of the primary coil 3 are electrically connected to two output terminals 5 and 6 attached to an insulating spacer 4 made of epoxy resin or the like. Output terminals 5 and 6 are formed by arranging outlet terminals 6 made of a solid conductor concentrically with a necessary insulation distance in the outlet terminal 5 made of a hollow conductor, and connecting these to an insulating spacer 4. It is attached integrally by casting etc. Further, a cylindrical non-linear resistance element 7 made of metal oxide or the like is interposed in the space between the output terminals 5 and 6, and is also integrally attached to the insulating spacer 4 by casting. Each insulating spacer 4 has a gasket 8 on both sides.
a.

The iron core 1, secondary coil 2, and primary coil 3 are connected via 8b.
Tank 9 of the current transformer that stores etc. and grounding case 1 on the bus bar side
0, and an insulating spacer 4
The space formed by the tank 9 and the tank 9 is filled with an insulating gas 11 such as SFs at a predetermined pressure. When such a gas insulated current transformer is directly connected to a gas insulated switchgear, a bus bar 12.13 housed in the grounding case 10 is electrically connected to the outlet terminal 5.6. Further, the outlet bushing 14 of the secondary coil 2 is airtightly attached to the tank 9 of the current transformer, and the current converted by the secondary coil 2 is drawn out.

In the gas insulated current transformer configured in this manner, the non-linear resistance element 7 generates only a potential difference of about several volts between the outlet terminals 5 and 6 under normal operating conditions.
It functions effectively as an insulator between 6 and 6. Furthermore, when an abnormal voltage occurs due to a ground fault in a gas-insulated switchgear or a surge current in a disconnector, the nonlinear resistance element 7 has good response characteristics and no delay in discharge time, and quickly absorbs the abnormal voltage. This provides insulation between the output terminals 5 and 6 and absorbs steep surge voltages before they enter the current transformer, thereby preventing surges from entering the primary coil 3.

As a result, a small creepage distance between the outlet terminals 5 and 6 of the insulating spacer 4 is sufficient, and the insulating spacer 4 can also be reduced to the minimum necessary size.

Effects of the Invention 1 As described above, according to the present invention, two lead terminals connected to both ends of the primary winding are integrally cast into an insulating spacer, and a metal oxide is formed between the lead terminals. A non-linear resistance element is provided, and this non-linear resistance element is integrally cast into an insulating spacer, which protects the equipment from abnormal voltage caused by surges, prevents insulation breakdown and internal short-circuit accidents, and improves reliability due to its small size. It is possible to obtain a gas-insulated current transformer with high performance.

[Brief explanation of drawings]

FIG. 1 is a plan view showing one embodiment of the present invention, and the second factor is also a longitudinal sectional front view. DESCRIPTION OF SYMBOLS 1...Iron core, 2...Secondary coil, 3...Primary coil, 4...Insulating spacer, 5.6...Output terminal, 7
...Non-linear resistance element, 8a, 9b...Gasket, 9...Tank, 1o...Grounding case, 11...
Insulating gas, 12゜13...bus bar, 14...outlet bushing. Applicant's agent Patent attorney Suzue Takehiko gt diagram 2nd ti! iI

Claims (1)

[Claims] An iron core around which a secondary coil is wound and a primary coil interlinked with this iron core are housed in a tank filled with insulating gas, and both ends of the primary coil are integrated with an insulating spacer that airtightly closes the tank. In a gas insulated current transformer connected to two casted outlet terminals, a nonlinear resistance element made of metal oxide is provided between the two outlet terminals, and this nonlinear resistance element is connected to the two outlet terminals. A gas insulated current transformer characterized by being integrally cast with an insulating spacer.