JPS6258230B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects the ground insulation resistance value of a low-voltage electric path of power line equipment and generates an insulation monitoring signal, such as a normal signal, which is set in stages based on the ground insulation resistance value or the ground insulation resistance value. , relates to a signal transmission method for transmitting caution signals, warning signals, etc. to a power line monitoring device.

As a detector for detecting the ground insulation resistance value of a low-voltage circuit of power line equipment, for example, an AC superimposed insulation detector indicated by symbol 8 in FIG. 1 is known. That is, after generating an AC signal with an oscillator 81 and amplifying the AC signal with an amplifier 82, a transformer (so-called CT)
6, the AC signal is injected into the grounding wire 5 of the bank (low-voltage line) to be monitored for insulation, and on the other hand, the AC signal injected into the grounding wire 5
The alternating current flowing through is detected by the transformer 7, amplified by the amplifier 83, and then synchronously rectified in the synchronous rectifier circuit 84 in synchronization with the phase of the alternating current signal from the oscillator 81. The level of the signal is detected by a level detection circuit 85 to obtain the ground insulation resistance value.

This AC superimposition type insulation detector 8 performs synchronous rectification so that the injected AC signal is transferred to the ground wire 5, the total stray capacitance to the ground (hereinafter referred to as stray capacitance) 3, the total insulation resistance to the ground (hereinafter referred to as insulation resistance). ) 4 to the ground, only the current component that passes through the insulation resistor 4 can be detected. ), it is possible to detect insulation resistance unaffected by stray capacitance.

When transmitting ground insulation resistance value data or insulation monitoring signals of power line equipment to the power line monitoring device 9 using the AC superimposed insulation detector 8 described above, conventionally the insulation detector 8 as shown in FIG. A data transmission line 10 is laid between the power line monitoring device 9 and the power line monitoring device 9. Especially when the grounding point of the power line equipment and the power line monitoring device 9 are located far apart, there are many banks whose ground insulation resistance must be monitored. In some cases, transmission line 1
0 is not easy to install, and the installation cost is also high.

In order to solve the above conventional problems, the present invention aims to provide an insulation state signal transmission method that does not require a data transmission line unique to a power line monitoring system.

For this purpose, in the present invention, the AC signal itself is transmitted by modulating the AC signal injected into the ground wire from the AC superimposed insulation detector with the information to be transmitted, that is, ground insulation resistance value data, insulation monitoring signal, etc. The power line on the ground side of the power line equipment is used as a data transmission line.

Embodiments of the present invention will be described below with reference to FIG.

In Figure 2, 1 is the power receiving transformer of the power line equipment, 2 is the low voltage line, 3 is the total stray capacitance to the ground of the low voltage line 2 (hereinafter referred to as stray capacitance), and 4 is the low voltage line 2's total stray capacitance to the ground. Indicates the total insulation resistance to ground (hereinafter referred to as insulation resistance), 5 is the grounding wire of the low-voltage line 2, 6 and 7 are transformers (so-called CT), 8 is an AC superimposition type insulation detector, 9 is the power line This is a monitoring device (only the receiving function part is shown).

In addition, in the insulation detector 8, 81 is the grounding wire 5.
82 and 83 are amplifiers; 84 is an oscillator 8;
The transformer 7 is synchronized with the phase of the AC signal generated in step 1.
85 is a level detection circuit that detects the level of the signal from the synchronous rectification circuit 84. In the power line monitoring device 9, 91 is an input circuit that performs impedance matching, etc.; is an amplifier, and 93 is a demodulation circuit that demodulates the AC signal injected from the insulation detector 8.

The configuration of the embodiment of the present invention differs from the conventional configuration (shown in FIG. 1) in the following two points. That is, firstly, the oscillator 81 of the insulation detector 8 is a modulated oscillator, and the output signal of the level detection circuit 85 is input to the oscillator 81, and secondly, the input line of the power line monitoring device 9 is insulated. The resistor 4 is connected to the ground power line 2a of the same bank as the low voltage line 2 to be detected.

The AC signal generated by the oscillator 81 is sent to the amplifier 82.
After being amplified, the signal is injected into the grounding line 5 via the transformer 6. As a result, an alternating current proportional to the combined impedance of the stray capacitance 3 and the insulation resistance 4 of the low-voltage line 2 flows through the grounding line 5 . This alternating current is detected by the transformer 7, amplified by the amplifier 83, and then sent to the synchronous rectifier circuit 84 to generate the oscillator 81.
The AC signal is rectified in synchronization with the phase of the AC signal generated by the AC signal. The phase of the current flowing through the insulation resistor 4 is in phase with the phase of the AC signal, and the phase of the current flowing through the stray capacitance 3 lags behind the phase of the AC signal and is not in phase with the AC signal. The obtained signal represents only the component flowing through the insulation resistor 4 of the alternating current flowing through the grounding wire 5. That is, the output signal level of the synchronous rectifier circuit 84 is proportional to the insulation resistance 4 of the power line (low voltage circuit) 2.

Incidentally, due to the imbalance between the non-ground side power lines 2b and 2c of the low-voltage power line 2, an unbalanced current due to the received power also flows in the grounding line 5, but this unbalanced current is filtered by the filter function provided by the amplifier 83. Most of it is removed, and the remaining components are also excluded from the signal obtained by the synchronous rectification because they are not in phase with the AC signal generated by the oscillator 81.

The output signal from the synchronous rectifier circuit 84 is input to a level detection circuit 85 and its level is detected. The configuration of the level detection circuit 85 differs depending on the form of information required by the power line monitoring device 9. That is,
When the power line monitoring device 9 requires ground insulation resistance value data of the low voltage line 2, the level detection circuit 85 is configured to output a signal with a level proportional to the output signal of the synchronous rectification circuit 84, and the power line monitoring device 9 When the device 9 requires an insulation monitoring signal (signal indicating that the ground insulation resistance value has reached a set level) of the low-voltage line 2, the level detection circuit is provided with a level comparison circuit and the like, and the synchronous rectifier circuit 84 It is configured to output a signal that changes stepwise each time the output signal reaches a plurality of set levels (for example, set for a caution state, an alarm state, etc. of the ground insulation resistance value).

The signal output from the level detection circuit 85 is input to the oscillator 81, and the AC signal generated by the oscillator 81 is modulated by the signal. The modulation method here may be AM modulation, FM modulation, or the like. Furthermore, when an insulation monitoring signal is required, the frequency of the AC signal may be shifted by a different value for each type of insulation monitoring signal, and shifting this frequency is also a type of modulation method. .

Needless to say, the output signal from the level detection circuit 85 is a signal to be transmitted to the power line monitoring device 9, and the alternating current signal from the oscillator 81 modulated by this signal is to be transmitted as a signal for measuring ground insulation resistance. The signal contains both signals. That is, the alternating current signal from the oscillator 81 is transmitted as follows: oscillator 81 → amplifier 82 → transformer 6 → ground wire 5 → transformer 7 → amplifier 8
3 → synchronous rectifier circuit 84 → level detection circuit 85 → oscillator 81", and as is well known, when the modulation method is AM modulation method, the level of the above AC signal converges to the level corresponding to the insulation resistance 4. , when the modulation method is the FM modulation method, the frequency of the AC signal converges to the frequency corresponding to the insulation resistance 4. In this way, the above-mentioned signal to be transmitted is sent to the ground side power line 2a of the low-voltage power line 2 (provided that the bank is the same as the bank to which the AC signal injection ground line 5 belongs), and the AC A signal is a transmission carrier for data or information to be transmitted;
Further, the ground side power line 2a is a transmission medium for data or information to be transmitted.

The input of the power line monitoring device 9 is the ground side power line 2.
a, and the oscillator 81 of the insulation detector 8
The modulated AC signal output from the power line monitoring device 9 is inputted to the power line monitoring device 9 via the ground side power line 2a, passed through the input circuit 91, amplified by the amplifier 92, and demodulated by the demodulation circuit 93. The demodulation method of the demodulation circuit 93 is a method that matches the AC signal modulation method of the insulation detector 8. For example, if the latter is an AM modulation method, the former is an AM demodulation method.

The signal obtained by demodulating the modulated AC signal in the demodulation circuit 93 as described above is the ground insulation resistance value data or the insulation monitoring signal, and this signal is processed appropriately in the power line monitoring device 9. is,
For example, printout of ground insulation resistance value data,
Actions such as issuing an alarm are taken.

As explained above, in the present invention, since the information to be transmitted is included in the AC signal injected from the insulation detector to the ground line, the information is received on the ground side power line of the bank where insulation detection is to be performed. Because ground insulation information can be transmitted simply by connecting the input of the power line monitoring device, there is no need to lay a data transmission line between the insulation detector and the power line monitoring device.
The effects of the present invention are extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, and FIG. 2 is a block diagram showing an embodiment of the present invention. Main symbols, 2...Low voltage line, 5...Grounding wire, 8...Insulation detector, 9...Power line monitoring device, 81...Oscillator,
84...Synchronous rectification circuit, 85...Level detection circuit, 9
3... Demodulation circuit.

Claims (1)

[Scope of Claims] 1. An alternating current signal is injected into the grounding wire of the power line, and the alternating current flowing through the grounding wire is synchronously rectified using the AC signal injected into the grounding wire. In an insulation state signal transmission method that generates an insulation state signal indicating the insulation state and transmits this insulation state signal to a power line monitoring device,
The AC signal is modulated by the insulation state signal and injected into the ground line, and the AC signal modulated by the insulation state signal is inputted from the ground line to the power line monitoring device, thereby receiving the insulation state signal. An insulation state signal transmission method for transmitting to the power line monitoring device. 2. The insulation state signal transmission method according to claim 1, wherein the insulation state signal is a signal indicating a ground insulation resistance value. 3. The insulation state signal transmission method according to claim 1, wherein the insulation state signal is an insulation monitoring signal set in stages based on the ground insulation resistance value.