JPH08115833A - Capacitor-type instrument transformer - Google Patents

Abstract

PURPOSE: To provide a capacitor-type instrument transformer in which the capacitance ratio of the capacitance of a high-voltage-side capacitor to that of a low-voltage-side capacitor is made constant even when a temperature is changed by a method wherein ceramic capacitors in which the temperature characteristic of a capacitance is identical are used as the high-voltage-side capacitor and the low-voltage-side capacitor. CONSTITUTION: A polyvinyl alcohol-based organic binder is added to a dielectric- material powder, and this mixture is pressed and worked to be a cylindrical shape. Molded bodies are fired at 1200 deg.C in the air. Then, a sintered body 11 whose diameter is 14mm and whose thickness is 15mm is obtained as a sintered body for a high- voltage-side capacitor, and a sintered body 21 whose diameter is 53mm and whose thickness is 1mm is obtained as a sintered body for a low-voltage-side capacitor. Both faces of them are coated with silver electrodes 12, 22, the electrodes are fired, and external terminals 14, 24 are attached. Then, the high-voltage-side capacitor having a capacitance of 100pF and the low-voltage-side capacitor having a capacitance of 20000pF are formed. The temperature characteristic of the capacitances is hardly changed within a range of 20 to 60 deg.C. The change rate of the capacitances is 1% or lower when an AC voltage of 0.5kVrms/mm is applied. Consequently, the ratio of the capacitances can be kept nearly constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer for a capacitor type instrument used for detecting a voltage of an AC high voltage distribution line or the like.

[0002]

2. Description of the Related Art A transformer for a measuring instrument for detecting the voltage of an AC high voltage distribution line is built in or additionally installed in a circuit breaker, a disconnector, a switch or the like. Previously, a transformer for electromagnetic type (winding type) measuring instruments consisting of an iron core and primary and secondary windings was used. This method has been widely used because of its small error and good characteristics, but it has the drawback of being large and heavy. For this reason, in response to a demand for downsizing and weight reduction of the disconnecting switch and the switch, a capacitor type voltage detector has been used in place of this.

By the way, the schematic circuit configuration of the capacitor type transformer for transformer is as shown in FIG. 1, and utilizes the voltage division by the capacitor, and the detection voltage V is V = C1 / (C1 + C2) × Va (1) However, C1 is a high-voltage side capacitor, C2 is a low-voltage side capacitor, and Va is a distribution line voltage.

Conventionally, a high voltage side capacitor is a ceramic capacitor of several tens pF to 500 pF, and a low voltage side capacitor is 0.1 μF to 500 μF.
A 1 μF film capacitor is used, and the detection voltage is about 5/1000 to 25/10000 of the distribution line voltage.

As the high voltage side ceramic capacitor, a small size, high withstand voltage and low loss capacitor having a paraelectric ceramic based on strontium titanate as a dielectric is used.

[0006]

Conventionally, the voltage detection by the measuring instrument transformer has been aimed at the presence / absence of voltage, the phase confirmation of three phases, the zero phase voltage detection at the time of an accident, etc. It didn't matter. However, in recent years, there has been a need to use the voltage detected by the transformer for measuring instrument as one of the sensors for remote control of the switch, so it is necessary to minimize the error in the detected voltage. .

However, in the conventional strontium titanate-based ceramic capacitor, the temperature characteristic of the capacitance has a relatively large negative slope as shown in FIG. Since a film capacitor using terephthalate or the like as a dielectric has a positive inclination, it has a drawback that the error of the detection voltage shown in the formula (1) becomes large. For example, when a conventional strontium titanate-based ceramic capacitor having the temperature characteristics shown in FIG. 2 and a film capacitor are combined, the fluctuation of the measured voltage at −20 ° C. to + 60 ° C. with a reference temperature of 20 ° C. is about ± 6% Becomes

Therefore, an object of the present invention is to provide a capacitor type transformer for a meter, in which the fluctuation of the detected voltage due to temperature is small.

[0009]

In order to achieve the above-mentioned object, the capacitor type instrument transformer of the present invention uses a ceramic capacitor having the same temperature characteristic of capacitance as the high voltage side capacitor and the low voltage side capacitor, respectively. It is characterized by being used.

[0010]

In the capacitor type instrument transformer of the present invention, ceramic capacitors having the same temperature characteristics of electrostatic capacitance are used as the capacitors on the high voltage side and the low voltage side.
Therefore, even if the temperature changes, the capacitance ratio between the high-voltage side capacitor and the low-voltage side capacitor becomes almost constant, and the voltage division ratio of the input voltage by the capacitor hardly changes.

[0011]

EXAMPLES Examples of the capacitor measuring transformer of the present invention will be described below. First, high-voltage side and low-voltage side capacitors were manufactured using a strontium titanate-based dielectric material having a dielectric constant of 1100. That is, a polyvinyl alcohol-based organic binder was added to the above-mentioned dielectric material powder and then press-molded into a columnar shape or a disk shape. After that, these molded bodies are fired at 1200 ° C. in the atmosphere to have a diameter of 14 mm and a thickness of 1 for a high-voltage side capacitor.
A 5 mm sintered body with a diameter of 5 for the low voltage side capacitor
A sintered body having a thickness of 3 mm and a thickness of 1 mm was obtained. Then, silver electrodes are applied to both surfaces of these sintered bodies by screen printing,
While baking, an external terminal was attached to this silver electrode with a conductive paste, and an insulating coating was performed with a liquid epoxy resin to obtain the high voltage side capacitor shown in FIG. 3 and the low voltage side capacitor shown in FIG.

In FIGS. 3 and 4, 11 and 21 are sintered bodies, 12 and 22 are silver electrodes, 13 and 23 are conductive adhesives, 14 and 24 are external terminals, and 15 and 25 are insulating sheaths. .

The capacitance of the obtained capacitor is
100pF for high voltage side, 20000pF for low voltage side
Met. For both the high voltage side and the low voltage side, the temperature characteristics of the capacitance are as shown in FIG. 2, the dielectric loss is 1% or less, and the electrostatic capacitance when an AC voltage of 0.5 kVrms / mm is applied. The rate of change in capacitance (electrostatic capacity-AC voltage characteristic) was 1% or less, and the AC breakdown voltage was 4 kV / mm or more.

Next, using the high-voltage side and low-voltage side ceramic capacitors thus obtained, the detection voltage of the circuit configuration shown in FIG. 1 (however, three low-voltage side capacitors are connected in parallel) is distributed. Assembling a transformer for a capacitor-type meter that has a line voltage of 17/10, 000, and a voltage of 6600V. The voltage of the AC high voltage distribution line was detected.

As a result, the temperature of this transformer is changed from -20 to 6
The detected voltage hardly fluctuated when it was changed in the range of 0 ° C. That is, by using the transformer for capacitor type instrument of the present invention, the fluctuation of the detected voltage, which was about ± 6% in the past, could be suppressed to almost zero.

In the above embodiment, a ceramic capacitor made of a strontium titanate-based material is used as the dielectric, but the present invention is not limited to this. That is, other AC ceramic capacitors can be used as appropriate.

Further, in the above embodiment, the shape of the ceramic capacitor is cylindrical or disc-shaped, but the present invention is not limited to this. That is, as the shape, a prismatic shape, a cylindrical penetrating shape, a disc penetrating shape, or the like can be appropriately used according to the installation space.

Further, the electrode material of the ceramic capacitor may be copper, nickel, etc. in addition to silver, and the forming method thereof may be plating, vapor deposition, sputtering, etc. other than the application of the paste. Furthermore, for terminal attachment, solder can be used in addition to the conductive paste,
As the exterior material, a powdered epoxy resin, a phenol resin, or the like can be appropriately used in addition to the liquid epoxy resin.

Further, in the above embodiment, 6600
V. The case of the voltage detection transformer of the AC distribution line is shown.
22000V. AC, 66000V. It can be applied to distribution lines with different voltages such as AC by selecting the rated voltage and capacity of the capacitor to be used.

[0020]

As is apparent from the above description, by using ceramic capacitors having the same temperature characteristic of capacitance as the high-voltage side capacitor and the low-voltage side capacitor, there is almost no fluctuation in the detected voltage due to temperature. It is possible to obtain a transformer for a capacitor type instrument.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram of a capacitor-type meter transformer.

FIG. 2 is a graph showing a temperature characteristic of capacitance of a capacitor.

FIG. 3 is a sectional view of a high voltage side ceramic capacitor.

FIG. 4 is a cross-sectional view of a low voltage side ceramic capacitor.

[Explanation of symbols]

 Va Distribution line voltage V Detection voltage C1 High voltage side capacitor C2 Low voltage side capacitor

Claims (1)

[Claims] 1. A capacitor-type transformer for a capacitor, wherein ceramic capacitors having the same temperature characteristics of capacitance are used as the high-voltage side capacitor and the low-voltage side capacitor, respectively.