JPS5944923A - Leakage detector - 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 an earth leakage detection device, and particularly to a device for preventing disconnection of a power transformer due to a high surge voltage such as a lightning surge that enters an electric circuit when the device is in use.

Conventionally, the leakage of this type of leakage breaker was 4g, and the detection device 1
Yf is #+Xi Ti for lightning surge voltage of several thousand volts.
In order to maintain the reliability of the detection device, a discharge element such as a varistor is provided on the seventh side of the power transformer as shown in FIG.

However, in recent years, as force control using thyristors has been adopted, extremely high 4-noge voltage often enters the electrical circuit at all times, causing the varistor to operate constantly and thermally destroy it, causing Secondary disasters related to short circuit accidents are increasing. In Figure 1, l is the power supply side terminal connected to the AC power supply, and C is the load side terminal connected to the load, and the electric line 3 that connects the power source and the load (in the figure, the electric line is a three-phase example,
71,. 711,. 7111) has a switching part (accurately, depending on the electrical circuit, ρ 4+1, 1
Ill+) and overcurrent string removal element! f (left 1,
! A zero-phase current transformer 6 is inserted into the electric line 3 via the line 3111). This zero-phase current transformer 6 detects the current leakage current flowing through the electric line 3, and the output signal detected by the zero-phase current transformer B is connected to a leakage detection circuit section consisting of an electronic circuit. When the current leakage current exceeds a set value, the current leakage detection circuit section 7 operates, outputs an output signal as an exception to the current leakage current, and applies the signal to the coil g to open the switching section da.

wo is a power source 1 lance that supplies power to the earth leakage detection circuit section 7, and the primary winding of the power transformer is connected to either end phase of the electric line 3, in the figure, electric lines 31, . Power supply voltage is introduced from 7111.

Thus, when an 8-current state occurs, the zero-phase current transformer 6 detects this and inputs it as an output signal to the earth leakage detection circuit section 7. When the current leakage current reaches a set value or more, the earth leakage detection circuit section 7 is output by the power from the power supply transducer, and the number is leakage 1
The voltage is applied to the tripping coil to trip the switchgear G, which opens the circuit and cuts off the supply from the power source to the load.

Figure 2 also shows the primary power transformer? ! A varistor // is inserted in parallel with the gland, and when a very high surge voltage enters the electrical circuit, this varistor // works to shunt the voltage and reduce the voltage applied to the primary winding of the power transformer 9. If the varistor is destroyed, the electric line Jl.
, , 7111 will be short-circuited, causing a secondary disaster. It has also been proposed to insert a capacitor in place of the varistor, but in this case as well, the surge voltage is bypassed from the transformer's next winding, but the dielectric breakdown of the capacitor is avoided. If this happens, it will become open and the capacitor will lose its function.

As a result of various studies taking into consideration the drawbacks of the conventional device iH'i, the present invention has been developed to provide protection against disconnection caused by lightning impulses in series with the primary side of the power transformer. By connecting a resistor for A phase current transformer, an M41L detection circuit that detects earth leakage using the output pj of this current transformer, a power transformer whose input terminal is connected to the electric path and supplies power to the earth leakage detection circuit, and its primary It is equipped with a series resistor that is inserted between the winding and the power transformer to prevent disconnection of the radio wave transformer due to excessive surge, and when high voltage due to lightning surge is applied to the power transformer, the resistor and the power transformer are connected. By dividing the voltage, the lightning surge voltage applied to the power transformer is attenuated and lowered. Even if the resistor is destroyed, the circuit on the next winding side is disconnected, completely preventing disconnection of the power transformer.

FIG. 1 shows an embodiment of the device according to the present invention, ff1J path i1. i
The corresponding parts in Figure 2 are indicated by the same reference numerals.The parallel connection of the varistor// in Figure 2 is stopped and the resistor 10 is connected to the line 3 (31 and ?+1 in the figure) and the /next winding of the power transformer. For convenience of explanation, the other parts are assumed to be the same as in Figure 1.

In addition, the power transformer normally used is one that steps down and supplies the voltage to the earth leakage detection circuit (<1s) of the electronic circuit, and a small transformer with many primary windings and several VA of 3% is used.Therefore, This type of lance has a very large static capacitance (hl) between the primary windings and between each layer, and exhibits low impedance for steep surges of several microseconds, such as lightning surges, and voltage distribution. is known to concentrate at the inlet of the winding of a transformer, causing dielectric breakdown and disconnection.
Windings near the terminals may melt due to the TI'++ current.

In the present invention, by connecting a small resistor of several tens to hundreds of ohms in series with the second/secondary winding of the power supply transducer, the rise of the voltage applied to the capacitance between the first and second input windings is delayed, and -Reduces the voltage applied to the secondary winding and limits the charging current.-Even if this lightning surge suppression resistor breaks, it acts as a fuse and prevents voltage from being applied to the primary winding of the transformer. This eliminates disconnection accidents in the power transformer. In this case, a resistance of several tens to hundreds of ohms1
Even if I enter 0, this (?- Yoruden)

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an earth leakage detection device showing an embodiment of the present invention, and FIG. 8I is a circuit configuration diagram of a conventional earth leakage detection device. In the figure, B is the zero-phase current transformer, 7 is the leakage 1 (1, detection circuit section, g
is the supplementary tripping coil, D is the power transformer, and 10 is the lightning surge suppression resistor. Patent applicant Terasaki Electric Industry Co., Ltd. Representative
Figure 1 Figure 2 107-

Claims (1)

[Claims] A zero-phase current transformer is inserted in the electric line connecting the power source and the load, and a leakage detection circuit section that detects leakage by the output signal of this current transformer, and 'The above-mentioned power transformer that supplies power to the Ijl detection circuit section, and a series resistor inserted between its/next winding and the electric circuit,
It is designed to prevent transformer θ) disconnection due to excessive surge! 1"'I'fK'< Earth leakage detection device.