JP2711308B2 - Zero-phase current transformer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current transformer for detecting a zero-phase current and a load current simultaneously.

[0002]

2. Description of the Related Art Conventionally, the following method has been employed to detect a zero-phase current component and a phase current component. As shown in FIG. 14, a round zero-phase current transformer ZCT and 2
A circuit formed by combining the current transformers CT and connecting them as shown in FIG. 18 is used. As shown in FIG. 15, a track type zero-phase current transformer ZCT
And two current transformers CT are combined, and a circuit formed by connecting them as shown in FIG. 18 is used. As shown in FIG. 16, a circuit is formed by arranging three current transformers CT in a line and inserting a load resistor for extracting a phase current in the middle of an output for extracting a zero-phase current as shown in FIG. use. If there is not enough space to arrange the three current transformers CT in a line, only the center current transformer CT is mounted on the current transformers CT on both sides as shown in FIG. 17, and these are placed as shown in FIG. A circuit is used which is connected by inserting a load resistor for extracting the phase current in the middle of the output for extracting the zero-phase current.

As a current transformer CT application, for example, when a zero-phase current transformer is mounted on a pole switch, the residual current becomes large at the time of overload such as a short circuit, the relay operates, and the switch is turned off. . The switch normally detects the current by using the current transformer CT when there is no short-circuit current interrupting capability, and locks the switch mechanism even when the residual current is large when the current exceeding the interrupting capability flows, They are not opened and closed. Also, when it is desired to measure a load current value other than the zero-phase current value as accident information, the current transformer CT is used for purposes other than the purpose of locking the switching mechanism.
May be used.

[0004]

Among the above four conventional detection methods, the first and second detection methods have a space for attaching two current transformers CT to a zero-phase current transformer ZCT that detects only a zero-phase current. It is necessary, and the space for the switch covering the entire circuit must be increased accordingly. In addition, the detection method requires a space in the direction in which the switches are arranged in a line, and the detection method requires a space in the vertical direction. There is. The method using three current transformers CT as described above is convenient because the zero-phase current and the phase current can be detected, but the excitation current of the transformer flows in the primary current, and this excitation current Contains a large DC component, the three current transformers CT have a large reactance compared to the sum of the phase current detection resistance R and the winding resistance, so that the time constant reaches several seconds. Therefore, the DC component of the excitation current is 1
When the iron core reaches the saturation region, an output is generated as the residual current in the zero-phase load resistance _RL for a long time, and there is a problem that the relay malfunctions. SUMMARY OF THE INVENTION An object of the present invention is to provide a zero-phase current transformer with current detection which can solve the above-mentioned conventional problems and can greatly reduce the number of parts and cost.

[0005]

In order to achieve the above-mentioned object, the present invention covers a track-type iron core with a protective case, winds a winding around the protective case, and surrounds the winding around the winding. A shield is formed, and three windings are electrically wound around the shield including the iron core, and a current detection element such as a load resistance for current detection and an auxiliary CT is connected in the middle of the winding. A zero-phase current transformer, wherein a load resistance is connected between both ends of a winding 4 uniformly wound around a protection case covered with a track-type iron core , or
The iron around the protective case covered with a truck-shaped iron core
When viewed from the center line that divides the major axis of the core into two,
The same number of turns and the same winding direction
Winding the windings 7 and 8 in opposite directions
Zero-phase current transformers connected in parallel via burden resistors, or
The iron around the protective case covered with a truck-shaped iron core
When viewed from the center line that divides the long diameter side of the core into two,
Are windings with the same number of turns and opposite winding directions
Windings 10 and 11 are wound, and the interval between the windings 10 and 11
, The windings 12, 1 which are half the number of turns of the windings 10, 11
3 and windings 12 and 13 are connected in a straightforward manner.
And the windings 10 and 11 are connected in parallel with each other.
And a zero-phase
In the current transformer, the part facing both sides of the protective case
Track-type shield or torch that also serves as the current detection core
Cover with a rack-type shield with a flange, and
The same shield on the insulating tape wound around
Of which are arcuate parts on both sides when viewed from the center line that divides the major diameter side into two
In minutes, the number of windings is the same, and the winding directions are opposite to each other.
Windings 23 and 24 are wound, and the distance between the windings 23 and 24
The winding 2 has half of the number of turns of the windings 23 and 24
5 and 26 are wound, and these windings 25 and 26 are connected in series.
Then, one end of this series-connected winding and each of the windings 23 and 24
One end of each is connected, and the other of the series-connected windings is
Connect current detection elements such as load resistance for current detection and auxiliary CT.
Connected to each winding of this current detection element
It is intended to have a feature that connects the end portions to each other.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 11. In FIG. 1, reference numeral 1 denotes a track-type iron core, 2 denotes a protective case which covers the inner diameter part to the outer diameter part of the iron core 1, 2a Is the gap between the iron core 1 and the protective case 2,
Reference numeral 3 denotes a winding wound around the protective case 2, which includes, for example, a winding 4 uniformly wound around one circumference of the protective case 2 as shown in FIG. 3 or one half-peripheral portion and the other half-periphery portion of the periphery of the protective case 2 as viewed from the center line 6 that divides the major diameter side into two, as shown in FIG. The windings 7 and 8 are wound so that the winding directions are the same and the winding directions are opposite to each other, and the windings 3b formed by connecting them in parallel via the load resistance 9 are used. Alternatively, as shown in FIG. 4, the number of turns is the same and the winding directions are opposite to each other in the arc-shaped portions around the protection case 2 when viewed from the center line that bisects the long diameter side. Between the wound windings 10 and 11 and between the windings 10 and 11 The windings 12, 13 are wound around the portion with half the number of turns of each of the windings 10, 11, and the windings 12, 13 are connected in series. The windings 10 and 11 are connected in parallel,
The winding 3c formed by connecting the load resistor 14 between the connection points may be used. Reference numerals 15 and 15 denote track-type shields provided around portions of the winding 3 opposite to both side surfaces of the protective case 2 and also serve as current detecting iron cores. As shown in FIG. 7, a track-shaped shield 16 may be used. Alternatively, as shown in FIG. 7, a track-type shield 16 and an inner edge of a long-diameter portion of the shield 16 may be disposed at equal intervals from the center line to both sides. In some cases, a flanged shield 18 formed by integrally molding a protruding tooth-shaped flange 17 is used,
Alternatively, as shown in FIG.
In some cases, a flanged shield 20 formed by integrally forming a flange 19 for connecting a portion at equal intervals from the center line to both sides at the inner edge of the long diameter portion into a window frame shape is integrally formed. 21 is a track type shield 15 as shown in FIG.
The insulating tape wrapped around 15 is shown in FIG.
As shown in FIG. 9, a winding wound around the insulating tape 21 so as to pass between the track-type shields 15 and 15 includes a track-type shield 16 as shown in FIG. 9 or FIG. Brim shield 18,
Alternatively, windings 23 and 24 wound around the arcuate portions on both sides of the flanged shield 20 so that the winding directions are the same and the winding directions are opposite to each other; Windings 25, 26 wound with half the number of turns of the windings 23, 24;
6 are connected in series, and a winding of this series connection and a winding 23,
24, one end of which is connected to the other, and the other end of which is a load resistor R for current detection (or an auxiliary CT or other current detection element).
22a or 22b or 22c connected via
Use A winding is wound around each of the above shields.
Because it is not tight, the gap between the shield and the iron core does not separate,
The effect can be maintained. Reference numeral 27 denotes an exterior tape that covers the periphery of the winding 22.

[0006] Of the zero-phase current transformers having the above-described configuration, those using a core having a toothed flange 17 have a current element detection characteristic and a residual current at that time of 3%.
When a phase-balanced current and a single-phase current are passed, and the single-phase current is applied, the arrangement of the single-phase primary conductor with respect to the iron core is symmetrically tested, rightward, and leftward. When the same experiment was performed using the iron core having the window frame-shaped flange 19, the results shown in Table 2 in FIG. 13 were obtained.

[0007] Thus, the normal current element is used for overcurrent locking or short-circuit current detection, but the output error with respect to the overcurrent corresponds to the phase of the primary conductor, regardless of the phase in which the overcurrent occurs. The load output is about ± 10% in the case of the toothed collar 17 and is within ± 2% in the case of the window frame-shaped collar 19 without being largely affected by the currents of the other phases. Thus, it can be used sufficiently as a signal error.

[0008]

Since the present invention is configured as described above,
When used in a case such as an air switch, it can be used in comparison with the conventional combination of using one zero-phase current transformer and two current transformers, or using three current transformers. Since the space for accommodating the current transformer can be greatly reduced, the case can be significantly reduced in size and weight, and the number of parts and cost of the zero-phase current transformer can be significantly reduced. In addition, there is an advantage that the residual current hardly changes in the current characteristics, and the maximum current value can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which a core and a shield are applied to an iron core of a trunk type zero-phase current transformer.

FIG. 2 is a diagram illustrating an example of a winding wound around a protective case.

FIG. 3 is a diagram illustrating another example of a winding wound around a protective case.

FIG. 4 is a diagram illustrating still another example of a winding wound around a protective case.

FIG. 5 is a front view of a truck-type shield.

FIG. 6 is a side view of FIG. 5;

FIG. 7 is a front view showing an example of a track type shield with a brim.

FIG. 8 is a front view showing another example of a track type shield with a brim.

FIG. 9 is a diagram illustrating an example of a winding when the track-type shield of FIG. 5 is used.

FIG. 10 is a diagram showing an example of a winding when the track type shield with a flange of FIG. 7 is used.

FIG. 11 is a view showing an example of a winding when the track type shield with a flange of FIG. 8 is used.

FIG. 12 is a table showing an example of an experimental example of the zero-phase current transformer according to the present invention.

FIG. 13 is a table showing another example of an experimental example of the zero-phase current transformer according to the present invention.

FIG. 14 is a diagram showing an example in which a zero-phase current transformer ZCT and a current transformer CT are mounted on a primary conductor.

FIG. 15 is a diagram showing another example in which a zero-phase current transformer ZCT and a current transformer CT are mounted on a primary conductor.

FIG. 16 is a diagram showing still another example in which a zero-phase current transformer ZCT and a current transformer CT are mounted on a primary conductor.

FIG. 17 is a diagram showing still another example in which a zero-phase current transformer ZCT and a current transformer CT are mounted on a primary conductor.

FIG. 18 is an equivalent circuit diagram of the mounting example of FIGS. 12 and 13;

FIG. 19 is an equivalent circuit diagram of the mounting example of FIGS. 14 and 15;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Track core, 2 ... Protective case, 3 ... Winding, 15
... track-type shield, 22 ... winding.

Claims (1)

(57) [Claims] 1. A truck type iron core is covered with a protective case,
A winding is wound around the protective case, a shield is provided around the winding, and three windings are electrically wound around the shield including the iron core. -Phase current transformer with current detecting elements such as load resistance and auxiliary CT connected, and a track-type iron core
Of the winding 4 uniformly wound around the protection case covered with
A zero-phase current transformer with a load resistor connected between
Around the protective case covered with the
One half circumference and the other as viewed from the center line that divides the major axis into two
And the winding direction is the same
Wind the windings 7 and 8 in opposite directions and bear these windings 7 and 8
Zero-phase current transformers or transformers connected in parallel via resistors
Around the protective case covered with the
As seen from the center line that divides the major axis into two,
Windings 1 with the same number of turns and opposite winding directions
0, 11 are wound around the interval between the windings 10, 11.
Are windings 12 and 13 which are half the number of windings of windings 10 and 11
And windings 12 and 13 are connected in series.
The windings connected in series and the windings 10 and 11 are connected in parallel with each other
And a zero-phase change by connecting a load resistance between the parallel connection points.
In the flow device, the part facing both sides of the protective case
A track-type shield or torch that doubles as a current detection core.
Cover with a rack-type shield with a flange, and
The same shield on the insulating tape wound around
Of which are arcuate parts on both sides when viewed from the center line that divides the major diameter side into two
Minutes, the number of ticketing is the same, and the winding directions are
Windings 23 and 24 are wound, and the distance between the windings 23 and 24
The winding 2 has half of the number of turns of the windings 23 and 24
5 and 26 are wound, and these windings 25 and 26 are connected in series.
Then, one end of this series-connected winding and each of the windings 23 and 24
One end of each is connected, and the other of the series-connected windings is
Connect current detection elements such as load resistance for current detection and auxiliary CT.
Connected to each winding of this current detection element
A zero-phase-sequence current transformer, characterized in that its ends are connected to each other .