JPH0528747Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Field of Industrial Application) The present invention relates to a multiple feedthrough current transformer, and particularly relates to improving the characteristics of a current transformer with a tertiary winding.

(Prior Art) Current transformers are broadly classified into wound type and feedthrough type based on their structure, and the feedthrough type, which uses the system bus as a primary circuit, is often used for large load current circuits. In addition, they are broadly divided into those for meters and those for protective relays, and due to the subdivision of applications, multiple current transformers, which incorporate multiple current transformers in the same phase, have come into widespread use. Ground fault detection in large load current circuits is performed primarily by a three-phase triangular connection method using a tertiary winding attached to an instrument current transformer to ensure detection sensitivity. FIG. 2 shows an example of a double feed-through current transformer having a conventional structure.

The current transformer 1 with a tertiary winding for measuring instruments and the current transformer 2 for protection are each formed by winding secondary windings 5 and 6 on iron cores 3 and 4 via an insulator (not shown). Further, in the current transformer 1, a tertiary winding 7 is wound through an insulator (not shown). These current transformer elements are integrally molded with a casting material 10 such as resin, except for a window 9 passing through the system bus bar 8 and a secondary terminal (not shown).

In some cases, the current transformer 1 is constructed by first winding a tertiary winding, and then winding a secondary winding thereon with an insulator interposed therebetween.

(Problem to be solved by the invention) In such a conventional structure, the tertiary current transformer 1 is affected by the magnetic field from the adjacent other phase bus and the return bus of the own phase while carrying a large load current. A harmful apparent ground fault zero-sequence current was induced in the winding 7, causing the ground fault relay to operate unnecessarily.

SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a multiple through-type current transformer which overcomes the above-mentioned drawbacks of the conventional technique and can supply a highly reliable zero-phase current to a relay.

[Structure of the device] (Means and effects for solving the problems) The present invention is characterized in that one or more protective current transformers without a tertiary winding are arranged on the outer circumferential side of a current transformer with a tertiary winding. , this protective current transformer has a damping effect against harmful magnetic fields from the other phase bus and the self-phase return bus, thereby reducing the induction of harmful current into the tertiary winding. .

(Embodiment) FIG. 1 is an embodiment of the present invention, illustrating the case of a double feed-through current transformer.

A current transformer 1 with a tertiary winding for meter use and a current transformer 2 without a tertiary winding for protection each have an iron core 3.
Secondary windings 5 and 6 are wound around and 4 through an insulator (not shown), and in the current transformer 1, a tertiary winding 7 is wound through an insulator (not shown). Here, the current transformer 2 is arranged concentrically on the outer peripheral side of the current transformer 1, and the iron core 4 surrounds the current transformer 1. These current transformers 1 and 2 are integrally molded using a casting material 10 such as resin, except for a window 9 through which the system bus bar 8 passes and a secondary terminal (not shown).

In addition, as a configuration of the current transformer 1, a tertiary winding 7 is attached to the iron core 3.
, and then the secondary winding 5 may be wound thereon with an insulator interposed therebetween.

With this configuration, most of the magnetic field created by the current flowing in the adjacent other-phase bus and own-phase return bus is shunted to the four iron core circuits of the protective current transformer 2 placed on the outer circumference, and It becomes difficult to exert an inductive effect on the three iron core circuits of the current transformer 1 with a tertiary winding for measuring instruments, which are arranged so as to be surrounded by the sides. Therefore, it is possible to reduce the residual tertiary current that is affected by the bus bar arrangement, that is, the apparent ground fault zero-sequence current, prevent unnecessary operation of the ground fault relay, and furthermore, it is possible to select the setting value of the relay operation to the optimum level. etc., can improve the reliability of grid protection.

In addition, the current transformer 1 with a tertiary winding for instruments requires a relatively large core cross-sectional area in order to satisfy the tertiary winding characteristics, but when compared with the conventional one assuming the same dimensions for the system bus through window 9, the present invention The average magnetic path length of the iron core circuit of the current transformer 1 with a tertiary winding can be reduced, contributing to improving the characteristics of the tertiary winding or reducing the cross-sectional area of the iron core, and thus making it possible to reduce the size and weight.

Furthermore, the rated primary current of the protective current transformer 2 is often selected to be larger than the load current value due to the need for protection coordination, but in the present invention, the inner diameter of the iron core 4 of the protective current transformer 2 is selected to be larger. Therefore, the number of windings that can be wound per layer of the secondary winding increases, and the number of layers of the secondary winding with large rated primary current specifications can be reduced, contributing to miniaturization.

In addition, since the length of the current transformers 1 and 2 in the penetrating direction of the system bus 8 is reduced, the area of the low voltage circuit portion such as the secondary winding circuit of the current transformer facing the system bus 8 can be reduced. The withstand voltage characteristics of the entire current transformer can be improved. Although the above embodiment describes a case in which two current transformers are combined, it can be similarly applied to a case in which three or more current transformers are combined. It is also possible to configure a plurality of sets of flow vessels 1 and 2 arranged side by side in the axial direction.

[Effects of the invention] As explained above, according to the invention, by arranging a current transformer without a tertiary winding on the outer circumferential side of a current transformer with a tertiary winding, It is possible to provide a Taju through-type current transformer that not only can prevent unnecessary operation of a ground fault relay and improve the reliability of system protection, but also can be made smaller and lighter.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a multiple feedthrough current transformer according to the present invention, and FIG. 2 is a sectional view showing a conventional multiple feedthrough current transformer. 1... Current transformer with tertiary winding for instrument, 2... Current transformer for protection, 3, 4... Iron core, 5, 6... Secondary winding, 7... Tertiary winding, 8... System Bus bar, 9...through window, 10...casting material.

Claims (1)

[Scope of utility model registration request] A current transformer with a tertiary winding, in which a secondary winding and a tertiary winding are wound on an iron core, and a current transformer, in which a secondary winding is wound on an iron core, and no tertiary winding, are combined. 2, wherein a current transformer without a tertiary winding is disposed concentrically on the outer circumferential side of the current transformer with a tertiary winding.