Patent Description:
Safety inspections of cubicle-type high-voltage power receiving and transforming equipment and switchboards are required by the Electricity Business Act as legal inspections, and these legal inspections are carried out about once a year. In addition, the business operator conducts a self-inspection of the load of the motor, etc., beyond the switchboard according to its own management standards, and this self-inspection is carried out once a week to once a month.

However, there are a wide variety of management targets in self-inspection, and the reality is that the number is too large to actually handle. Therefore, an insulation resistance monitoring device that automates self-inspection has been developed.

For example, in Patent Document <NUM>, an insulation resistance monitoring device is disclosed. In this insulation resistance monitoring device, the voltage obtained by dividing the voltage by the insulation resistance of the motor and the reference resistance is input to the control unit, the insulation resistance value corresponding to the input voltage is calculated by the calculation unit, and the insulation resistance value of the motor is measured.

However, even when an insulation resistance monitoring device as in Patent Document <NUM> is installed, it is necessary to manually measure the insulation resistance to be measured using a mega tester for legal inspection. Also, in the self-inspection, it may be necessary to measure the insulation resistance for each measurement target in order to investigate the cause.

By the way, in the insulation resistance monitoring device as in Patent Document <NUM>, a semiconductor switch such as an FET, etc., is used as a switch for opening and closing a conduction path between the measurement target and the power supply that applies a voltage to the measurement target. Such a switch has a low resistance value of <NUM> MΩ or less in the off state of the power supply.

Therefore, even if the power of the insulation resistance monitoring device is turned off, if the insulation resistance is measured manually using the mega tester, the current due to the megger voltage of the mega tester will leak to the insulation resistance monitoring device side.

In order to prevent such a situation, it was necessary to remove the insulation resistance monitoring device from the measurement target every time the measurement was performed using the mega tester, which was complicated.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an insulation resistance monitoring device capable of measuring insulation resistance using a mega tester without removing the insulation resistance monitoring device.

To solve the problem, the present invention provides an insulation resistance monitoring device according to claim <NUM>.

According to the present invention, it is possible to provide an insulation resistance monitoring device that enables measurement of insulation resistance using a mega tester without removing the insulation resistance monitoring device.

<FIG> is a diagram showing a schematic configuration of an insulation resistance monitoring device <NUM> according to the present embodiment. As shown in <FIG>, the insulation resistance monitoring device <NUM> includes a current detecting unit <NUM>, a voltage generating unit <NUM>, and a switch <NUM>.

The current detecting unit <NUM> is composed of an operational amplifier or the like, and is connected between the power supply line and the ground line of the motor <NUM> as an object to be measured. The current detecting unit <NUM> detects the current flowing through the insulation resistance of the motor <NUM>. The output part of the current detection unit <NUM> is provided with a control unit (not shown). The control unit performs an output indicating an abnormality if an insulation resistance value calculated based on the current detected by the current detecting unit <NUM> is outside the normal value range.

The voltage generating unit <NUM> is connected between the power supply line and the ground line of the motor <NUM>, and generates a voltage of DC500V or the like when the insulation resistance is measured by the insulation resistance monitoring device <NUM>. The voltage generated by the voltage generating unit <NUM> is supplied to the motor <NUM> via the power supply line. Further, when the insulation resistance is not measured by the insulation resistance monitoring device <NUM>, the voltage by the voltage generating unit <NUM> becomes 0V.

The switch <NUM> is a switch that opens and closes the connection path between the power supply line or ground line of the motor <NUM> and the voltage generating unit <NUM>. In the present embodiment, the switch <NUM> is, for example, a mechanical switch, and the off resistance when the connection path between the power supply line or the ground line of the motor <NUM> and the voltage generating unit <NUM> is opened is <NUM> MΩ. This is because the insulation resistance of the motor <NUM> is about <NUM> MΩ. The resistance of the switch <NUM> can be changed according to the measurement target, and may be <NUM> MΩ or more, preferably <NUM> MΩ or more.

As the switch <NUM>, for example, a reed relay can be used in addition to the mechanical switch.

A voltage of about 200V to 480V is applied to the motor <NUM> from the three-phase power supply <NUM>. An earth leakage breaker <NUM> is provided between the three-phase power supply <NUM> and the motor <NUM>. The three-phase power supply <NUM> is connected to the output of a switchboard (not shown). The switchboard is connected to a cubicle-type high-voltage power receiving / transforming facility (not shown). From the electric power company, for example, a voltage of 6600V is supplied to the cubicle type high voltage power receiving / transforming equipment, and the voltage supplied to the cubicle type high voltage power receiving / transforming equipment is stepped down to a low voltage of about 200V to 480V by the switchboard provided on each floor, for example.

<FIG> shows an example of a reed relay 30A. The reed relay 30A includes a reed switch <NUM>. The reed switch <NUM> is a switch in which contacts are sealed in a glass tube or the like, and is held in the electrostatic shield pipe <NUM> by bushings 32a and 32b made of a highly insulating material. The electrostatic shield pipe <NUM> is installed in the tubular hollow portion of the coil bobbin <NUM>, and overhangs 38a and 38b are provided at the open end of the hollow portion. The coil bobbin <NUM> and the electrostatic shield pipe <NUM> are in contact with each other only by the overhangs 38a and 38b, and a gap <NUM> is formed between the inner surface of the hollow portion of the coil bobbin <NUM> and the electrostatic shield pipe <NUM>.

In <FIG>, overhangs 38a and 38b are provided at both ends of the hollow portion of the coil bobbin <NUM>, but the overhangs 38a and 38b may be arranged inside the hollow portion, and the number of overhangs can be <NUM> or more.

On the back surface of the coil bobbin <NUM>, the resin <NUM> is filled after winding the coil <NUM>, and the magnetic shield case <NUM> is covered so as to cover the coil <NUM>.

In the reed relay 30A as described above, as an example, a highly insulated reed switch having an insulation resistance of <NUM><NUM>Ω or more is used as the reed switch <NUM>.

Further, the reed switch <NUM> may be configured so that the contacts do not oxidize by sealing an inert gas in a glass tube or the like.

Specific examples of the reed relay 30A include SL-<NUM> of Sanei Kogyo Co. , S8-1204VU of Cynergy3, and <NUM>-<NUM>-<NUM> of Coto Technology.

In the insulation resistance monitoring device <NUM> of the present embodiment as described above, when the insulation resistance of the motor <NUM> is measured by the mega tester <NUM>, the connection path is opened by the switch <NUM>. Then, as shown in <FIG>, the probe 200a of the mega-tester <NUM> is brought into contact with the ground line of the motor <NUM>, the probe 200b is brought into contact with the power supply line of the motor <NUM>, and then a megger voltage of about <NUM> V is applied. As a result, a current flows from the power supply line of the motor <NUM> to the ground line in the direction indicated by the arrow A, and the insulation resistance of the motor <NUM> can be measured.

In this way, even when a megger voltage of about <NUM> V is applied to the motor <NUM> by the megger tester <NUM>, since the off resistance of the switch <NUM> is <NUM> MΩ when the switch <NUM> opens the connection path between the power supply line or the ground line of the motor <NUM> and the voltage generating unit <NUM>, the current due to the megger voltage does not leak to the insulation resistance monitoring device <NUM> side.

As a result, according to the present embodiment, it is possible to measure the insulation resistance of the motor <NUM> using a mega tester without removing the insulation resistance monitoring device <NUM> from the motor <NUM>.

Next, a comparative example compared with the insulation resistance monitoring device <NUM> of the present embodiment will be described. <FIG> is a diagram showing an insulation resistance monitoring device <NUM> of the comparative example. The insulation resistance monitoring device <NUM> of the comparative example is different from the insulation resistance monitoring device <NUM> of the present embodiment in that the switch <NUM> is composed of a semiconductor switch such as an FET.

In the insulation resistance monitoring device <NUM> of the comparative example, when the insulation resistance of the motor <NUM> is measured by the mega tester <NUM>, the connection path is opened by the switch <NUM>. Then, as shown in <FIG>, the probe 200a of the megger tester <NUM> is brought into contact with the ground line of the motor <NUM>, the probe 200b is brought into contact with the power supply line of the motor <NUM>, and then a megger voltage of about <NUM> V is applied. As a result, a current flows from the power supply line of the motor <NUM> to the ground line in the direction indicated by the arrow A, and the insulation resistance of the motor <NUM> can be measured.

When a megger voltage of about <NUM> V is applied to the motor <NUM> by the megger tester <NUM> in this way, since the switch <NUM> in the insulation resistance monitoring device <NUM> of the comparative example is a semiconductor switch, the off resistance when the connection path between the power supply line or the ground line of the motor <NUM> and the voltage generating unit <NUM> is opened is about <NUM> MΩ. Therefore, when the probes 200a and 200b of the mega tester <NUM> are brought into contact with the power supply line and the ground line of the motor <NUM> as described above, the current due to the megger voltage leaks to the insulation resistance monitoring device <NUM> side as shown by the arrow B in <FIG>.

Therefore, if the insulation resistance monitoring device <NUM> of the comparative example is used, it is necessary to remove the insulation resistance monitoring device <NUM> from the motor <NUM> when measuring the insulation resistance using the mega tester <NUM>.

As described above, as is clear from the comparison between the insulation resistance monitoring device <NUM> of the present embodiment and the insulation resistance monitoring device <NUM> of the comparative example, according to the insulation resistance monitoring device <NUM> of the present embodiment, The insulation resistance can be measured by the mega tester <NUM> without removing the insulation resistance monitoring device <NUM> from the motor <NUM>.

The above embodiment is an example, and various modifications can be made without departing from the scope of the present invention as defined by the appended claims.

In the above-described embodiment, an example in which the measurement target of the insulation resistance is the motor <NUM> has been described, but the present invention is not limited to such an example. Various loads other than the motor <NUM> can be measured.

Claim 1:
An insulation resistance monitoring device (<NUM>) for monitoring an insulation resistance of an object (<NUM>) to be measured, a normal value of the insulation resistance being about <NUM> MΩ, the object being connected to a ground through a ground line and driven by a voltage of about <NUM> to <NUM> VAC applied through a power supply line, wherein the insulation resistance monitoring device (<NUM>) comprises:
a current detecting unit (<NUM>) that is configured to be connected between the power supply line and the ground line of the object (<NUM>) to be measured and configured to detect a current flowing through the insulation resistance of the object (<NUM>) to be measured;
a voltage generating unit (<NUM>) that is configured to be connected between the power supply line and the ground line of the object (<NUM>) to be measured and configured to generate a voltage of about 500VDC to supply the voltage to the object through the power supply line; and
a switch (<NUM>) configured to open and close a connection path between the power supply line or the ground line of the object (<NUM>) to be measured and the voltage generating unit (<NUM>),
the device being further configured to have the insulation resistance of the object (<NUM>) measurable by a mega tester (<NUM>) connected between the power supply line and the ground line,
wherein, when the connection path is closed by the switch (<NUM>) in a state where a power supply through the power supply line to the object (<NUM>) is stopped, and the voltage generating unit (<NUM>) generates a voltage of about 500VDC to supply the voltage to the object (<NUM>) through the power supply line, the current detecting unit (<NUM>) is configured to perform an output indicating an abnormality if the insulation resistance value calculated based on a current detected by the current detecting unit (<NUM>) is outside a range of the normal value,
wherein, when the insulation resistance of the object (<NUM>) is measured by a mega tester (<NUM>) connected between the power supply line and the ground line for legal inspection, the connection path is opened by the switch (<NUM>) in a state where a power supply through the power supply line to the object (<NUM>) is stopped,
wherein the switch (<NUM>) has an off resistance of <NUM> MΩ or more when the connection path is opened.