JPS58157337A - Automatic changeover grounding system - 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 In contrast to the currently commonly used grounding method that involves grounding work in the second building of a low-voltage power distribution system, the present invention provides a grounding method by interposing a semiconductor circuit in the grounding wire. When an abnormal high voltage starts to enter the low voltage side due to high and low voltage mixing in the ungrounded system, the system automatically switches to the grounding system using the second building grounding wire in response to this. This method has the advantage of being extremely simple and easy to prevent accidents such as electric shocks and electrical fires due to m*, since it can always be made equivalent to an ungrounded system. Although accidents involving high and low voltages are infrequent, when abnormal high voltages such as this occur intrude into the low voltage side,
In response to this, it was made into a grounding system and was able to function as a type 2 grounding wire.By combining these advantages and functions, the main purpose is to rationally ensure safety. .

Currently, according to laws and regulations, safety measures against high and low voltage cross-contact accidents on low-voltage power lines are to be carried out through grounding work in the second building. Regarding accident prevention, earth leakage circuit breakers will be installed and metal outer boxes of electrical equipment will be grounded in Building 3 in coordination with grounding work in Building 2.

However, because there are generally few people who use electricity who are familiar with it, the true meaning of electricity is not understood, and it is often used in a flawed manner that violates laws and regulations. Accidents such as electric shocks and electrical fires are occurring one after another.

In addition, there are some electrical equipment (medical equipment, etc.) that do not want to be used as a grounding system, and for these, although it is relatively expensive, it is necessary to install a cross-contact prevention board inside the equipment. Some systems are operated as ungrounded systems by using installed transformers.

In this way, an ungrounded system (of course, one with a device that can detect and handle ground faults) is desired at all times, but a grounded system is required in the event of an abnormality such as high or low pressure mixture, so both of these needs to be satisfied. The automatic switching grounding method that allows this will be explained using an example of actual application based on confirmation of the operation of semiconductor circuits.

Application example 1 (in the case of a three-phase three-wire electric circuit) As shown in Figure 1, the automatic switching semiconductor circuit (1) according to the present invention is inserted into the grounding wire connected to the second grounding pole. By connecting to the voltage detection point (H) of the detection transformer (E), suppose that in the field of the transformer C that transforms from the high voltage line (A) to the low voltage line (-), as shown in (2). The insulation between the tube and the low voltage is broken, causing cross contact, and the pressure is divided between each of them in the mutual relationship between the impedance (2) and the impedance (3), and the shared voltage of (3),
When the voltage reaches a predetermined value within the range that ensures safety on the (b) side, the semiconductor (4) becomes conductive in response to that voltage, and at the same time, the semiconductor (5) becomes conductive. By operating in this state, it suddenly changes to conduction and puts both ends of (1) in a low impedance state.

As a result, the ground fault current accompanied by cross-contact is not restricted and passes through the primary side of (e), forming a circuit equivalent to the second grounding wire.

Furthermore, since the high-voltage side electrical circuit is not grounded, the current due to this one-wire ground fault is only affected by the ground capacitance (g), and is extremely small compared to the ground fault current in the grounded system. ,(
Since the current flowing through 5) is not very large, the semiconductor used therein is not expensive either.

Also, this (1) may be inserted directly into the second building grounding wire without going through (e), but by using (e), the zero-sequence voltage due to leakage on the (e)) side can be reduced. Device to detect! (
Since it can be installed in January as well, rational insulation management will be possible.

Application example 2 (single-phase three-wire circuit) As shown in Figure 2, (1) is divided into two equal parts of the normal shared voltage between one winding on the secondary side of (c). By connecting both ends of the neutral wire side of the impedance body, if a high voltage starts to be applied to the end due to a mixture of high and low voltages, such as in the vicinity of a transformer. , in the same manner as in Application Example 1, (1) becomes conductive, lowering the impedance at both ends and achieving the intended purpose.

Note that the ground fault detection device (su) added to this can detect electrical leakage by determining the following voltages.

When normal (the voltage between RO1 and RO2 is 200■, the voltage between 01 and ◎dark, and the voltage between 02 and 00 are both 100■), the terminal voltage of (F) is 50V, but When a leakage occurs on the mouth 1 side, the voltage changes from 50 to 100■. When a leakage occurs on the mouth 2 side, the voltage changes from 50 to 1oov.
When a leakage occurs on the side, the switch is shifted from 50 to O■.

(Support) Common to Application Examples 1 and 2, when the degree of current leakage on the extension side progresses to a certain value or more, if you want to automatically exclude the current leakage point from the circuit, C) and (3)
By appropriately selecting the shared voltage, etc., it is possible to shift the point at which the initial conduction occurs in (1) to the lower voltage direction. The intended purpose can be achieved through the earth leakage breaker, etc.

As described above, by using the automatic switching grounding method with a simple configuration and low cost, the grounding system using the second type grounding wire can be
Since it is always equivalent to a non-grounded system, the following effects occur.

(1) In a typical system with low capacitance to ground, if a human body touches one live wire, or if one wire is shorted to ground due to natural deterioration or damage to the insulation, this can result in electric shock. No more worries about death or electrical fires.

(2) For metal outer boxes of low-voltage electrical equipment,
There is no need to perform ridge grounding work.

(3) The negative impact on other workpieces due to induction by leakage current will be drastically reduced.

[Brief explanation of drawings]

FIG. 1 shows application example 1. Figure 2 shows application example 2゜(1),
Automatic switching semiconductor circuit, (2) is the impedance on the high voltage sharing side (3) is the impedance on the low voltage sharing side (single wave side), (4) is the control semiconductor (single wave side), and (5) is , Main circuit semiconductor (single wave side) (A) is the high voltage side electric circuit (B), low voltage side electric circuit (C) is for the three-phase transformer in Figure 1, and the single voltage transformer in Figure 2). Figure 1 shows the transformer for detecting ground voltage. Figure 2 shows the partial voltage impedance for detecting ground voltage. (f) is the connection point at both ends of (1), and (g) is the ground capacitance. (G) is the contact m pole (su) due to the 2nd fi1 grounding work.
Figure 1 shows the ground fault voltage detection device for three-phase and Figure 2 shows the ground fault voltage detection device for single circuit. Patent applicant: Hajime Fukunaga / H

Claims (1)

[Claims] A semiconductor circuit is interposed in the type 2 grounding wire of the low-voltage circuit, and it is normally kept in a non-conducting state, equivalent to a non-grounded system, and abnormal high voltage begins to be applied to the low-voltage side due to high and low voltage mixing, etc. In this case, an automatic control circuit that operates in accordance with the instantaneous value of the voltage makes the semiconductor circuit conductive at a predetermined starting value and changes the grounding thread to the second building grounding wire. Grounding type