JP2015095323A - Leakage current detection device for leakage circuit breaker - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage current detection device for a leakage circuit breaker that is improved to improve a detection function of a leakage current and reliability of operational characteristics.SOLUTION: The leakage current detection device for the leakage circuit breaker is packaged in a main body case, detects a leakage current of AC and DC components circulating in a main circuit and opens a main circuit contact in the case where the leakage current exceeds a predetermined threshold value. The leakage current detection device includes: an AC zero-phase-sequence current transformer in which a secondary coil is wound around a first core surrounding a main circuit conductor; a DC flux-gate type DC current transformer in which a secondary coil is wound around a second core surrounding the main circuit; and a signal processing circuit. A shield plate 8 is interposed between a first core 4a and a second core 5a, and the first and second cores 4a and 5a are then collectively accommodated in a common shield case 9. Further, the shield case 9 is accommodated in a resin case 11 via a shield plate 10, and the resin case 11 then includes output terminals 4d and 5d for the secondary coils wound around the first and second cores and a terminal 4e for a test coil.

Description

  The present invention relates to a leakage current detection device mounted on a leakage breaker.

  In recent years, with the diversification of the distribution system through the application of various renewable energy power generation systems, such as solar power generation, and inverter circuits, the leakage detection range has also been expanded for leakage breakers that ensure the safety of the distribution system. Improvement of reliability is an important issue.

    In addition, regarding the earth leakage breaker applied to the distribution system, in addition to the functions of Type AC (limited wave alternating current) and Type A (pulsating current leakage current) in the IEC standard, Type B (IEC 62423) for the purpose of protecting the DC leakage current. Has been enacted.

  On the other hand, the inventors, as a leakage current detecting device for a leakage breaker corresponding to Type B of the IEC standard, have a zero phase change for detecting an AC component in which a secondary winding is wound around a first core surrounding a main circuit conductor. A flux gate type DC current transformer for detecting a DC component in which a secondary winding is wound around a second core surrounding the main circuit, and a second current transformer corresponding to each of the AC and DC current transformers. A leakage current detecting device for a leakage breaker having a signal processing circuit for next output has been proposed (see Patent Document 1), and its circuit configuration (block diagram) is shown in FIG.

  In FIG. 4, 1 is a main circuit conductor, 2 is a main circuit contact interposed in the main circuit conductor 1, 3 is a tripping coil of the main circuit contact 2, and 4 is a secondary winding around an annular core 4 a surrounding the main circuit conductor 1. A zero-phase current transformer (ZCT) 5 for detecting an AC leakage current wound around a wire 4b, 5 is a flux gate type DC current transformer in which a secondary winding 5b is wound around an annular core 5a surrounding the main circuit conductor 1, Reference numeral 6 denotes a secondary output signal processing circuit for the zero-phase current transformer 4 and the flux gate type DC current transformer 5, and this signal processing circuit 6 is configured by combining the circuits shown in the figure. Although the main circuit in the illustrated example is a two-wire system (R, S phase), it can be similarly applied to a three-phase AC three-wire system.

  The function and operation of the leakage current detection device are described in detail in Patent Document 1, and a current transformer for detecting a leakage current, a zero-phase current transformer 4 for detecting an AC component, and a DC component as shown in the circuit of FIG. By separately setting the AC component and DC component leakage sensitivity current values separately from the flux gate type DC current transformer 5 for detection, for example, harmonic noise and harmonic leakage generated from the inverter circuit of the distribution line Suppressing the unnecessary operation of the earth leakage breaker under the influence of the current, it is possible to cope with a wide range of current from pure DC current to high frequency current, and to protect the electric circuit and the human body from the leakage of the distribution system.

JP 2013-38047 A (FIG. 8)

By the way, we designed the earth leakage circuit breaker with the current transformer that detects the leakage current divided into the zero-phase current transformer for AC component detection and the flux gate type DC current transformer for DC component detection as described above. In manufacturing, there are the following problems. That is,
(1) Since the earth leakage circuit breaker incorporates a current transformer for detecting earth leakage into the main body case of the same frame size as the circuit breaker for wiring, the storage space of the current transformer is limited, and AC component detection and DC component In order to incorporate two current transformers into the main body case separately for detection purposes, the current transformers must be compact and compact.

In this regard, the conventional general zero-phase current transformer has a structure in which a core wound with a secondary winding is combined with a shield plate and accommodated in a core case (hollow cylindrical resin case). When the two current transformers 4 and 5 (see FIG. 4) for detecting the AC component and the DC component, which have independent structures as described above, are juxtaposed and mounted in the case, the space occupied by both current transformers is reduced. It becomes large and it becomes difficult to incorporate it into an earth leakage breaker having a predetermined frame size.
(2) In addition, the zero-phase current transformer 4 for AC component detection has a commercial frequency specification, whereas the flux gate type DC current transformer 5 for DC component detection uses a secondary winding as an excitation coil. Since the core is excited by passing a pulsed excitation current higher than the commercial frequency, if the two current transformers are placed close together, such as an alternating current zero-phase current transformer and a direct current flux Magnetic field interference occurs with the gate type DC current transformer, and the balance characteristics and leakage detection accuracy of each current transformer are reduced. For this reason, the leakage breaker is unnecessarily operated and reliability is lowered.

  The present invention has been made in view of the above points. The object of the present invention is to solve the above-mentioned problems, to make the current transformer assembly for detecting a leakage current compact, and also to change the AC component detection / DC component detection. To provide a leakage current detecting device for an earth leakage breaker improved so as to improve the reliability of an AC component and a DC component leakage current detection function and operating characteristics by effectively suppressing magnetic field interference between flowers. is there.

In order to achieve the above object, according to the present invention, the leakage current of AC and DC components that are mounted on the main body case of the circuit breaker and flow through the main circuit conductor is detected, and the leakage current exceeds a predetermined threshold value. As a leakage current detection device for an earth leakage breaker that outputs a trip signal to the trip coil of the breaker to open the main circuit contact, a secondary winding is wound around the first core surrounding the main circuit conductor. A zero-phase current transformer for detecting a rotated AC component, a flux gate type DC current transformer for detecting a DC component in which a secondary winding is wound around a second core surrounding a main circuit, and a signal processing circuit thereof In
A shield plate is interposed between the first core and the second core, and the first core and the second core are collectively accommodated in a common shield case (Claim 1). .

  In the above configuration, the shield case incorporating the first and second cores is accommodated in a hollow cylindrical resin case via a shield plate, and the resin core is wound around the first core around the outer peripheral edge portion. An output terminal of the rotated secondary winding, a terminal of the test winding, and an output terminal of the secondary winding wound around the second core are provided.

  The first core and the second core wound with the secondary winding are integrated into a common shield case, and this core assembly is further integrated into a resin case having a secondary output terminal and a test terminal. According to the housed configuration, the outer shape of the current transformer assembly composed of the two components of the zero-phase current transformer for detecting the AC component and the flux gate type DC current transformer for detecting the DC component is reduced in size and the leakage is interrupted. This can be mounted on the main body case of the vessel, and as a result, a significant space saving can be achieved as compared with the conventional case where two separate current transformers are juxtaposed.

  Further, in addition to the common shield case described above, a shield plate is interposed between the first core and the second core, and shields shared by the first and second cores are provided at both ends of the shield case. By arranging the plate, the AC component can be suppressed by suppressing the magnetic interference between the zero-phase current transformer for detecting the AC component and the flux gate type DC current transformer for detecting the DC component, and the external magnetic field interference. , DC current leakage current detection function, and leakage breaker reliability can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram of a current transformer for detecting a leakage current according to an embodiment of the present invention, in which (a) is a perspective external view of the current transformer, (b) is an XX cross-sectional view of (a), c) is a partially enlarged view of (b). FIG. 2 is an exploded perspective view of FIG. 1. It is a bird's-eye view which shows the internal structure of the earth-leakage circuit breaker carrying the current transformer of FIG. It is a circuit block diagram of the earth-leakage circuit breaker currently disclosed by patent document 1. FIG.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on the examples shown in FIGS. In the drawings of the embodiments, the same members corresponding to those in FIG.
First, in FIGS. 1A to 1C and FIG. 2, a first core 4a corresponding to a zero-phase current transformer (ZCT) 4 (see FIG. 4) for detecting an AC component of a leakage current, and a DC The second core 5a corresponding to the flux gate type DC current transformer for component detection is, for example, an annular core in which plates of permalloy and nanocrystalline soft magnetic material are laminated and the outer periphery is covered with core cases 4c and 5c. The first core 4a and the second core 5a are integrally overlapped with a shield plate 8 (for example, a silicon steel plate) sandwiched between them as shown in the figure, and then an annular shield case 9 having a halved structure. (Steel drawn products).

  The shield case 9 that collectively accommodates the first core 4a, the second core 5a, and the shield plate 8 interposed therebetween is shared by the current transformers 4 and 5 at both end faces thereof. The current transformer assembly 7 is configured by stacking the shield plate 10 (silicon steel plate) and housing it in the resin case 11. Here, the resin case 11 has a hollow cylindrical structure in which a fitting hole for the main circuit conductor 1 (see FIG. 4) is formed at the center thereof. Reference numeral 11 a denotes a case cover for the resin case 11.

  Further, the resin case 11 is pulled out from the secondary winding 4b (see FIG. 4) and the test winding (not shown) of the zero-phase current transformer wound around the first core 4a at the peripheral portion. A secondary output terminal 4d, a test winding terminal 4e, and a secondary output terminal 5d drawn from the secondary winding 5 (see FIG. 4) wound around the second core 5a are provided.

  According to the current transformer assembly 7 configured as described above, a current transformer assembly comprising two units of a zero-phase current transformer 4 for AC component detection and a flux gate type DC current transformer 5 for DC component detection. 7 can be made compact and compact and mounted in the main case of the earth leakage breaker as described later.

  Further, since the shield plate 8 is interposed between the first core 4a and the second core 5a collectively accommodated in the shield case 9, the zero-phase current transformer 4 for detecting the AC component and the DC component are provided. Magnetic interference with the fluxgate DC current transformer 5 for detection is effectively prevented, and the shield plate 10 is shared by the first core 4a and the second core 5a at both ends of the shield case 9. Therefore, the leakage current detection accuracy of the AC and DC components flowing in the main circuit can be improved, thereby preventing unnecessary operation of the leakage breaker and improving the reliability of the leakage protection operation.

  Next, FIG. 3 shows the internal structure of the leakage breaker equipped with the current transformer assembly 7 shown in FIG. In FIG. 3, 12 is a main body case (molded resin case) of the earth leakage breaker, 13 is a main circuit terminal, 14 is a contact opening / closing mechanism for opening / closing the main circuit contact 2 of FIG. 4, 15 is an operation handle, and 16 is the main handle. A coil unit of the tripping coil 3 (see FIG. 4) of the circuit contact 2 and 17 is a circuit unit of the signal processing circuit 6 (see FIG. 4). The current transformer assembly 7 shown in FIG. The main circuit conductor 1 (see FIG. 4) of each phase provided inside the housing is enclosed and disposed in a space in the case between the contact switching mechanism 14 and the main circuit terminal 13.

1 main circuit conductor 2 main circuit contact 3 trip coil 4 zero phase current transformer 4a first core (annular core of zero phase current transformer)
4b Secondary winding 4c Core case 4d Secondary output terminal 4e Terminal of test winding 5 Flux gate type DC current transformer 5a Second core (annular core of DC current transformer)
5b Secondary winding 5c Core case 5d Secondary output terminal 6 Signal processing circuit 7 Current transformer assembly 8, 10 Shield plate 9 Shield case 11 Current transformer resin case 12 Earth leakage circuit breaker body case

Claims (2)

Detects AC and DC leakage currents that flow through the main circuit conductor mounted on the circuit breaker case and outputs a trip signal to the tripping coil when the leakage current exceeds a specified threshold. A leakage current detecting device for an earth leakage breaker that opens the main circuit contact, and a zero-phase current transformer for detecting an AC component in which a secondary winding is wound around a first core surrounding the main circuit conductor; In what comprises a flux gate type DC current transformer for detecting a DC component in which a secondary winding is wound around a second core surrounding a main circuit conductor, and a signal processing circuit of each current transformer,
An earth leakage circuit breaker characterized in that a shield plate is interposed between the first core and the second core, and the first core and the second core are collectively assembled in a common shield case. Leakage current detection device.   The current detection device according to claim 1, wherein a shield case incorporating the first and second cores is accommodated in a hollow cylindrical resin case via a shield plate, and the outer peripheral edge of the resin case An earth leakage interrupter comprising: an output terminal of a secondary winding wound around a first core; a terminal of a test winding; and an output terminal of a secondary winding wound around a second core Leakage current detection device.