JPS5875422A - Device for protecting 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 The present invention relates to a protection device for a current transformer used, for example, in a switchboard.

Conventionally, this type of device did not have any special features, and it detected abnormalities such as insulation breakdown in current transformers. The conventional circuit is shown in Figure 1. (1) is the primary conductor, (2) is the current transformer inserted into this primary conductor (1), and (3) is this current transformer (2).
), (41 is a load such as a coil connected to this secondary circuit (3). Also, IAI represents an arbitrary point in the secondary circuit (3).

Next, the flow of current to the load will be explained.

A current corresponding to the primary conductor (1) is supplied to the secondary side of the current transformer (2). Then, the current transformer (21 secondary circuits (3
) is normal, the current transformer (2) is caused by the secondary current of the current transformer 12) and the load f41 connected to the secondary circuit (3).
A certain number 1 is induced on the secondary side of . If the secondary circuit (3) of the current transformer 12) opens for some reason during such normal operation, for example, at an arbitrary point in the secondary circuit 12), there was no means to detect this in the past. .

Conventional circuits were configured as described above, so when the secondary circuit of the AC converter opens, high heel pressure is induced in the current transformer, which not only causes accidents such as dielectric breakdown and burnout of the current transformer. This has the disadvantage that it may even cause the switchboard to burn out or cause a fire.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and by providing a non-linear resistance element that suppresses voltage rise in the secondary circuit of a current transformer and an open circuit detection sensor that responds to the non-linear resistance element. It is an object of the present invention to provide a protection device for a current transformer that can detect an open circuit in a secondary circuit of a current transformer.

An embodiment of the present invention will be described below with reference to the drawings. spear 2
In the figure, (5) is the secondary circuit (3) of the current transformer (2).
) is a non-linear resistance element (hereinafter referred to as a varistor) such as a varistor connected in parallel to the load (41), which suppresses high voltage when it is induced in the secondary circuit (3). (6) is an open circuit detection sensor (hereinafter referred to as a current detection device) such as a current detection device connected in series to the varistor (5), and when the varistor 15) is in the energized state. When this happens, it operates accordingly and detects whether the secondary circuit (3) is open. Note that the other configurations are the same as those of the prior art and will not be described here.

In this invention, during normal operation, the load (4) is connected to the secondary circuit 13) of the current transformer 12) as explained in the conventional circuit.
1 induces a low constant voltage on the secondary side of the current transformer (2), so the varistor (5) does not operate.
Therefore, the current detection device (6) also does not operate. In such a state, if the secondary circuit (31) of the current transformer (2) is opened at the IA1 point for some reason, the impedance of the secondary circuit (3) becomes infinite, and the current flows to the negative conductor (1). All of the magnetic current becomes an exciting current. Therefore, the iron core (not shown) is excessively excited, and a high voltage is induced until the iron core is saturated. This induced high voltage causes the varistor (
5) becomes energized, the resistance value decreases, four currents flow, and the current detection device (6) detects this current, indicating that the secondary circuit (3) of the current transformer (2) has opened. Detect.

In addition, this detection signal can be used to automatically generate an alarm (1) or automatically trip the breaker (not shown) of the feeder to which the secondary conductor (2) for the current transformer (2) belongs. It's okay.

Although the above embodiment shows a circuit using one current transformer, it is also possible to use two or more current transformers, a current transformer with a wire connection, a tertiary winding, or the like. Further, in the above embodiment, the case where the non-linear resistance element is a varistor has been described, but the non-linear resistance element may be a Zener diode.

Furthermore, in the above embodiment, the case where the open circuit detection sensor is a current detection device has been explained, but the open circuit detection sensor may also be an electric signal meter, a thermometer, a resistance meter, etc. Open circuits may be detected by any method, such as heat transfer through contact or space, or comparison of resistance values.

As described above, according to the present invention, when the secondary circuit of a current transformer is opened, the voltage rise is suppressed by the nonlinear resistance element,
Since an open circuit detection sensor that responds to this is provided, it is possible to prevent dielectric breakdown or burnout of the current transformer.

[Brief explanation of drawings]

Figure 1 is a circuit configuration diagram of a conventional current transformer, and Figure 2 is a circuit configuration diagram showing a protection device for a current transformer according to an embodiment of the present invention. In the figure, (2) is a current transformer, (3) is a secondary circuit, and (4) is a secondary circuit.
1 is a load, (5) is a non-linear resistance element, and (6) is an open circuit detection sensor. In Figure 1, the same reference numerals indicate the same parts, and the same reference numerals indicate corresponding parts. Agent Makoto Kuzuno - Figure 1 Figure 2

Claims (1)

[Claims] A non-linear resistance element that is connected in parallel to a load inserted into the secondary circuit of the current transformer and suppresses a voltage rise in the secondary circuit of the current transformer when the secondary circuit of the current transformer is opened. A current transformer protection device equipped with an open circuit detection sensor that operates according to the magnetic pressure suppression of a linear resistance element.