JPH043260Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a ground failure display device for an AC electric fence.

Although it is specified that the ground resistance of AC electric fencing equipment should be 100Ω or less, it is actually difficult for general users to obtain a ground resistance of 100Ω or less. For this reason, many electric fences have poor grounding, which not only reduces their effectiveness, but also causes a large voltage drop of 1,000 to 3,000 V in the ground resistance, often resulting in dielectric breakdown of the primary power transformer. Therefore, if the ground is defective, a ground defect indicator is required to warn of the ground defect.

FIG. 1 shows a ground failure indicator installed on imported products made in the United States.

Resistors 8 and 9 are 100KΩ, and the neon tube 6 indicates a grounding failure, but in the case of a megger test, it shows a value of 50KΩ to 100KΩ, which can be confused with poor insulation of the distribution line, and also indicates that the earthing resistance is 100Ω or less. There was a drawback that the light would turn on even if the light was on.

Figure 2 shows a protection device against ground failure that was used by a domestic manufacturer for some tests. Barista 11, 12
In addition to absorbing surges during lightning strikes, the output voltage applied to the ground terminal 5 and the primary power supply circuit will not exceed the varistor voltage of the varistor 12 even if the earth resistor 2 is used. Also, impedance 8 and 9
0.01μF and impedance 10 as 0.015μF.
1MΩ parallel circuit, neon tube 6 and parallel impedance 7 are 0.047μF and resistance 33KΩ parallel circuit,
Also, the varistor 11 has a varistor voltage of 220V,
If a varistor voltage of 620V is used as the varistor 12, the megger test will show several tens of MΩ, and when the earth resistance is less than 100Ω, the indicator light 6 will not light up, and when it is more than 300Ω, it will show a value of several tens of MΩ. It blinks, so you can tell whether the ground resistance is appropriate depending on the scale of the fence circuit.

Also, Appended Table 8 of the Ministerial Ordinance on Electrical Appliances and Materials, 1. Common matters, 2.
It was thought that there would be no problem because the current flowing through the 1KΩ resistor, which is regulated by the structure, was less than 1mA, but since the impedance is connected to the primary circuit and secondary output circuit, the transformer is an isolation transformer. The circuit shown in Fig. 2 cannot be used because the opinion was expressed that it would violate the regulations that state that it is legal. Naturally, the circuit shown in FIG. 1 cannot be used either.

FIG. 3 shows a ground fault indicator for an electric fence that has the same effect as the one shown in FIG. 2 based on the above process and does not violate the ministerial ordinance.

In Fig. 3, AC power is supplied from 1, and the shock voltage generation mechanism 2 of the electric fence generates a high shock voltage in the secondary winding of the output transformer 3, which is then passed through the output terminal 4 and the ground terminal 5. Applied to the fence line.
The impact voltage applied to the fence wire flows through the ground capacitance (a) and the earth resistance (b) of the fence wire, causing a voltage drop across the earth resistance (b).

If the grounding is defective and the voltage drop (b) is large, this voltage drop will also flow to the series circuit of the varistors 12 and 13, causing a voltage drop in the varistor 13 as a matter of course. This voltage drop flows through the impedance 10 to the neon indicator light 6, and the neon indicator light blinks in accordance with the period of the shock voltage to warn of a ground failure.

Ballistas are used not only to indicate ground failures, but also to absorb surges during lightning strikes.
Varistors 11 and 13 were selected as 220D with a varistor voltage of 220V for AC100V, and varistor 12 was selected as 360D with a varistor voltage of 360V to completely block AC100V and pass the voltage drop due to ground failure. Also, impedance 10 is 630V0.047μF.
1.5MΩ parallel circuit as impedance 7
Using a parallel circuit of 630V0.01μF and 33KΩ, as a result, when the ground capacitance of the fence line is in the range of 0.005μF to 0.033μF, when the earth resistance is 100Ω, it will not light up at all, and when it is 300Ω, it will be bright enough. I adjusted it to make it shine.

As detailed above, by using two varistors connected in series, surges caused by lightning can be absorbed without any problems, and the output transformer's primary and secondary are electrically disconnected. This can indicate a ground failure.

In a 500V megger test using a prototype, the insulation resistance between the primary and ground was 5MΩ.

[Brief explanation of drawings]

FIG. 1 shows an example of an imported product made in the United States. FIG. 2 shows an example of a domestically produced electric fence equipped with a surge absorbing varistor, which has been used on some trials in the past. FIG. 3 shows an embodiment of an earth failure indicating device which also serves as a surge absorbing varistor of the present invention. 1...Primary AC power supply, 2...Impact voltage generation mechanism of electric fence, 3...Output transformer, 4...Output terminal, 5...Earth terminal, 6...Neon indicator light, 7
... Parallel circuit of C and R, 10 ... Parallel circuit of C and R, 11, 13 ... Varistor (varistor voltage
220V) 220D, 12... Varistor (varistor voltage
360V) 360D, A... Ground capacitance of the fence line, B... Earth resistance.

Claims (1)

[Scope of utility model registration request] Using AC voltage as the primary power source, the charge stored in the charging/discharging capacitor is repeated approximately once every second and discharged to the primary winding of the output transformer, creating a high voltage shock to the secondary winding. In an electric fencing device that generates voltage, varistors 12 and 13 are connected in series between the AC primary input circuit and the ground terminal, and impedance 10 and neon indicator light 6 are connected in series and in parallel with 13. A ground failure display device in an electric fencing device formed by connecting impedance 7.