JPH0548140Y2 - - Google Patents

Description

[Detailed explanation of the invention] "Industrial application field" This indicator does not display even if lightning surges penetrate, and only when AC electrical equipment or systems have a fault such as a ground fault or short circuit. The present invention relates to a device for displaying.

"Conventional technology" Conventionally, fault current is transformed into an appropriate current value,
This is rectified to charge a capacitor, and a liquid crystal display element (hereinafter abbreviated as LCD) is connected in parallel to this capacitor.
The display continued for a certain period of time even after the fault current stopped flowing.

``Problem that the invention aims to solve'' When a surge voltage enters an electrical device that has a built-in earth arrester, the surge current flows through the earth arrester to the grounding wire, as if the electrical equipment had malfunctioned.
The surge current may cause a malfunction indicator to operate and display an indication. As a result, it was not possible to determine whether the electrical equipment was malfunctioning or normal.

``Means for solving the problem'' As shown in the principle explanatory diagram in Figure 1, the fault current i
is transformed into an appropriate current value, and a resistor 10 of an appropriate value provided before or after the rectifier 6 limits the current and lengthens the time constant. The capacitor 7 is charged with the rectified current of an appropriate magnitude and the current duration, and the LCD 8 connected in parallel to the capacitor 7 continues to display the display for a certain period of time even after the fault current i stops flowing. be.

"Effect" Since the fault current i is generally removed in a short time,
A circuit with a short time constant is formed to rectify this short-term fault current, charge the capacitor 7 to a certain value, and connect the LCD 8 in parallel to the capacitor 7.
LCD8 can be displayed for several hours.

A surge current of several tens of microseconds will prevent the capacitor 7 from reaching the required charging voltage, and in the case of a fault current i such as a ground fault or short circuit, the energization time will be several hundred milliseconds, which is longer than a surge current, so the fault current i will be small. You can also get the required charging voltage.

"Example" The embodiment shown in FIG. 2 will be explained.

Here, n represents the nth unit.

A transformer 2-n having a plurality of earth protectors 12-n is housed in a metal case 1-n and connected to the AC system 11.

The transformer 2-n is grounded by a grounding wire 3-n.

A current transformer 4-n is connected to the grounding line 3-n, and a resistor 10-n is connected in series with a capacitor 7-n before or after a rectifier 6-n. Further, an LCD 8-n is connected in parallel to the capacitor 7-n, and a bidirectional earth arrester 5-n is connected in parallel to the current transformer 4-n. Bidirectional earth arrester 5
The characteristics of -n are selected to protect the circuit components from overvoltage and to charge the capacitor 7-n to a sufficiently high voltage above the operating threshold of the LCD 8-n.
Push button switch 9 connected in parallel with LCD 8-n
-n is for forcibly returning the display on the LCD 8-n.

4-n to 10-n are collectively referred to as a failure indicator A-n.

If the high voltage winding 2'-1 of the transformer 2-1 is grounded to the metal case 1-1, the fault current will flow through the grounding wire 3'-1.
1, and a fault indicator A-1 is displayed on the metal case 1-1.
If installed, the secondary current i' of the current transformer 4-1 due to the fault current i is rectified by the rectifier 6-1, and the capacitor 7-1 is charged in a short time. Even after the fault current i disappears, due to the voltage of the capacitor 7-1,
The LCD 8-1 can be displayed for quite a long time (one hour or more), and it can be easily determined that the transformer 2-1 is out of order.

The capacitor 7-1 connects the LCD 8- to the LCD 8-1 through the LCD 8-1.
When the voltage drops below the operating threshold of 1, the display disappears naturally. If you want to forcefully return the display before that, push the push button switch 9-1.

On the other hand, when a surge voltage due to lightning enters the high voltage winding 2'-1 of the transformer 2-1, the surge current flows through the earth arrester 12-1, to the grounding wire 3-1, and to the metal case 1-1. If the fault indicator A-1 is installed, the secondary current i' of the current transformer 4-1 due to the surge current is rectified by the rectifier 6-1 in the same way as the fault current i, and the capacitor 7-1 is charged. , rectifier 6-1
The surge current is suppressed by an appropriate resistor 10-1 placed before or after the , and the charging time is several tens of microseconds, so the capacitor 7-1 cannot be charged to the required voltage and the fault indicator is displayed. It is not possible. Therefore, the fault indicator can be displayed only when a fault current is flowing through transformer 2-1.

``Effects of the invention'' This invention has made it possible to reliably determine whether electrical equipment is malfunctioning or normal. Furthermore, the display does not require an internal power source and is constructed from a purely electrical circuit, providing high reliability.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of this invention, and FIG. 2 is an explanatory diagram of an embodiment. In the figure, i is a fault current, 7 is a capacitor, 8 is a liquid crystal display element (LCD), and 10 is a resistor.

Claims (1)

[Claim for Utility Model Registration] A current transformer is attached to the grounding wire of an electrical device that is connected to an AC system and has at least an earth arrester, and a resistor and a capacitor are connected in series to the secondary side of this current transformer. A liquid crystal display element is connected in parallel to this electricity storage device, and the resistor is configured such that when a surge current from the lightning arrester flows through the grounding line, the electricity storage device becomes lower than an operating threshold value of the liquid crystal display element. When the battery is charged to a small voltage and a ground fault or short-circuit current flows through the grounding wire, the capacitor is set to be charged to a voltage equal to or higher than the operating threshold of the liquid crystal display element. Features a fault indicator for electrical equipment.