JPS60216274A - Insulation monitoring apparatus - Google Patents

Abstract

PURPOSE:To make it possible to certainly transmit an alarm signal over a long distance, by using the monitor signal applied to the earth wire of a transformer under earthing construction of the second kind by an insulation detection apparatus. CONSTITUTION:An oscillation part 8 oscillating frequency different from power source frequency applies a monitor signal to an earth wire 4 by an injection transformer 6 and CT5 detects the current flowing to the earth wire 4 and applies the output thereof to a judge part 7. This judge part 7 separates only the monitor signal from the output of a current transformer 5 and ampliies the same while the amplified signal receives the phase comparison with oscillation voltage from the oscillation part 8 and, when the current having the same phase as oscillation voltage reaches a definite value, an alarm signal is outputted to a modulation part 9. Further, the modulation part stops the oscillation of the oscillation part 8 on the basis of the output thereof. A receiving part 12 receives the monitor signal coming from an electric circuit 2 and generates an alarm when this monitor signal is one receiving modulation in the modulation part 9.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrical circuit insulation monitoring device. Conventionally, as a method of monitoring the insulation condition of the low-voltage circuit on the secondary side of a transformer that transforms high-voltage electricity into low-voltage electricity, a low-frequency voltage (different from the power frequency) ( A monitoring signal) is applied, and this voltage causes a current to flow through the impedance between the low-voltage line connected to the transformer and the ground, and this current flows to the grounding wire of the transformer's type 2 grounding work, so this current is detected from the ground wire using an OT (current transformer) or the like, a signal is extracted through a filter, etc., and the change in ground impedance of the electric circuit is determined by monitoring this value.

Furthermore, by comparing the phase of the monitoring signal and the monitoring signal detected by the OT with the current, and extracting the voltage component of the current that is in phase with the monitoring signal, the interference between the electrical circuit and the ground is detected. During the dance, people were also judged on their resistance.

These devices (insulation detection devices) that monitor the impedance between the electrical circuit and the ground are generally placed near the transformer, and the operation of the insulation detection device is determined by the person monitoring the location of the transformer. If the device is permanently stationed in a location (office, etc.) that is different from the power receiving room (power receiving room), install a separate signal wire for transmitting the signal output from the insulation detection device between the power receiving room and the office, etc. It needed to be placed.

For this reason, when new signal wires were installed in an already completed building, the wiring work required a lot of time and money. To compensate for this, the conventional method of transmitting signals between the power receiving room and offices, etc. is to superimpose a high-frequency electrical signal modulated with the signal to be transmitted on the power wiring for the lights, and separate this high-frequency signal. A method of transmitting the necessary signal by receiving and demodulating it at a location (light line speed method)
was there.

However, since the conventional method described above uses power wiring for electric lights, the signal transmission may not be sufficient depending on changes in the electric light load, and the length of the electric power wiring for electric lights, the load, etc. are kept constant. It has the disadvantage that it cannot be put to practical use unless it is constrained to the following conditions.

The present invention has been made in order to eliminate the drawbacks of the conventional insulation monitoring device, and is aimed at the transmission of signals between the power receiving room where the insulation detection device is installed and the office where the person monitoring it is located. For this purpose, power wiring is used, and as a means of signal transmission, the insulation detection device uses the monitoring signal added to the grounding wire of the transformer's type 2 grounding work, so by using this device, , there is no need for construction work for the arrangement of signal wires, and the equipment that sends out signals on the power receiving room side can be installed at low cost because it uses an insulation detection device.Furthermore, monitoring signals can be transmitted widely to every corner of the electrical circuit. It is an object of the present invention to provide an insulation monitoring device which is emitted at a low frequency with low internal resistance due to the need for monitoring, has small attenuation, and is capable of sufficiently reliably transmitting a signal over a relatively long distance. .

The present invention will be described in detail below based on illustrated embodiments.

FIG. 1 is a block diagram showing one embodiment of the present invention. In this figure, reference numeral 1 indicates the low-voltage side winding of a transformer that transforms high-voltage electricity into low-voltage electricity, and in the case of this embodiment, it indicates a single-phase three-wire electric circuit. 2 and 3 indicate two of the low-voltage electrical lines connected to the transformer, and the electrical line 2 is subjected to type 2 grounding work with the ground wire 4 at the transformer.

Reference numeral 8 denotes a oscillator section that oscillates at a frequency different from the power supply frequency, and an injection transformer 6 applies a monitoring signal to the ground line 4. In this embodiment, a frequency of 25 Hz and a voltage of 2.5 VC (effective value) is applied to the ground wire.

5 is a GT (current transformer) for detecting the current flowing through the grounding wire 4, and the current detected by GT 5 is separated and amplified only the monitoring signal in the judgment section 7, and the oscillation voltage and phase of 8 are determined. When the current in phase with the oscillation voltage reaches a certain value, an alarm signal is sent to the output terminal 13 of the judgment section 7 @9
is a conversion section which stops the oscillation of 8 when the 11 signal is output to the judgment section output 13. 9 stops the oscillation of 8 when a signal different from 13 needs to be transmitted. In this embodiment, the device consisting of @5 to 9.13, which can have the function of dividing and intermittent at time intervals and sending out signals other than 13, is referred to as an insulation detection device. Note that the increase in the impedance of 4 due to the connection of 5 and 6 should not affect the grounding resistance of the required second camphor earth grounding work. (In the case of the embodiment, the number is 1 or less.) 10 is a capacitor connected to one line of the electrical circuit where the insulation detection device is installed, and 11 is a grounding wire that is grounded to the earth.

The monitoring signal coming on the electric line 2 is received as a voltage between it via 10 and 11, and the receiving section 12 separates and amplifies the monitoring signal, and this monitoring signal is the signal modulated by 9. ◎ 10 is a device that generates an alarm when the electrical circuit is connected to the ground by 12. Also, the monitoring signal current flowing through 10 to 12 to 11 is an insulation detection device. Keep it small enough so that it does not affect the current you are trying to detect.

In addition, 12 is a monitoring signal emitted from an insulation detector installed in the power receiving room, which generates an alarm when the monitoring signal applied to 2 cannot be detected, in order to issue an alarm in the safe direction. is frequency 25”z+voltage 2.
In the case of 5V, the attenuation is very small, and tests were conducted in many locations in which receivers made up of 10 to 12 receivers were attached to the ends of electrical circuits, and all of them detected and operated accurately.

Therefore, by using this device, it is possible to send the alarm signal of the insulation detection device to the receiving device of another remote office connected to the same transformer circuit with sufficient reliability by using the ground side circuit of the power wiring. can.

In the insulation detection device, since 5 to 8 are technologies that have already been used, it can be manufactured cheaply by just adding 9, and the receiving part also detects, separates, and amplifies low frequency signals, so it is easy to compare. Matoyasu 11tll K 111 Since it can be made,
The insulation detection device of the present invention and the low Ii it emits! d
Insulation monitoring devices used in combination with receivers to detect wave signals are practical and widely available.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1... Low voltage side winding of the transformer, 2 and 3... Low voltage electrical circuit connected to the transformer, 4... Ground wire, 5... OT
(current transformer), 6... injection transformer, 7... judgment section,
8... Oscillator section, 9-. Variable 1i14@, 10-... Capacitor, 11... Ground wire, 12... Receiving section, 13.
...Alarm signal output.

Claims (1)

[Claims] A low-frequency AC voltage that is different from the same wave number as the power supply of the transformer is applied to the ground wire of the second type grounding work of the transformer that converts high voltage electricity into low voltage electricity, and this voltage is used to perform the second type grounding work. The function detects the current flowing between the ground and the low-voltage line connected to the transformer, which flows back into the ground wire, and determines the insulation state of the line, and when the insulation status of the line changes,
A device (insulation detection device) that has the function of stopping the application of the AC voltage of a low frequency different from the power supply frequency to the grounding wire of type 2 grounding work, or of intermittent application of the voltage at certain predetermined time intervals. And, it is installed separately from this and detects the voltage of low frequency called f#J electromotive wave frequency between the line of the low voltage electric line and the ground, and when this voltage disappears,
Alternatively, an insulation monitoring device comprising: a device (notification device) that issues a 41F alarm when this voltage coincides with the interruption of the voltage applied by the insulation detection device.