JPH0535389B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for transmitting alarm signals, particularly a method for transmitting insulation deterioration alarm signals, etc. of secondary electrical circuits detected in a power receiving room to a monitoring station located in a remote location. Regarding.

(Prior art) When commercial power is received by a power receiving transformer via a power transmission line and distributed to a grounded power line at one end of the secondary side,
In each power receiving room, early detection and repair of abnormalities in the electrical circuit is an important issue in order to ensure a stable supply of electric power, and each power receiving room is equipped with an electrical safety monitoring device to detect various abnormalities in the electrical circuit, such as insulation deterioration or power receiving transformer oil temperature. Efforts are being made to detect abnormalities such as ascent and transmit these warning signals to remote manned monitoring stations for early detection of abnormalities.

Conventionally, when transmitting this alarm signal, a separate transmission path is installed between the power receiving room and the manned monitoring station, and the signal is sent and received via this.

However, this method not only imposes a heavy economic burden, but also involves extremely dangerous installation of transmission lines when the power receiving room, for example, a cubicle, is installed at a high place, such as on the roof of a high-rise building. Conventionally, the following methods have been devised for this purpose.

This is done by applying an output signal from an AC signal oscillation circuit with a frequency different from the commercial power supply frequency to the electrical circuit via the grounding wire of the receiving transformer, which is used to measure the characteristics of the electrical circuit, and then transmitting an alarm signal. The application of the alternating current signal to the electric line is stopped continuously or intermittently for a predetermined period of time depending on the type of alarm to be sent, and at the same time, the alarm receiving station located on the electric line This is an alarm signal transmission method in which the type of alarm signal to be transmitted is identified by detecting the stoppage or intermittent time of the alternating current signal occurring between the electric line and the ground.

However, the above-mentioned conventional alarm signal transmission method has a drawback in that it is impossible to monitor the insulation state of the electrical circuit during that time period during which the application of the measurement signal to the electrical circuit is stopped.

(Object of the Invention) The present invention was made in order to eliminate the drawbacks of the conventional alarm signal transmission system as described above, and it is designed to continuously monitor the insulation of the electrical circuit even when transmitting the alarm signal. An object of the present invention is to provide a method for transmitting an alarm signal of an insulation detector.

(Summary of the Invention) In order to achieve this object, the alarm signal transmission method of the present invention stops the application of the measurement signal voltage V (volts) to the electric circuit, and instead transmits the alarm signal for a predetermined length of time according to the alarm signal to be sent. Continuously or continuously, the voltage applied to the electrical circuit of the measurement AC signal is lowered or increased to V ₁ [volt], and at the same time, the detected value of the leakage component of the measurement AC signal flowing back to the ground wire is set to V. /V multiplied by ₁ to monitor the required insulation, and at the alarm signal receiving point, identify the type of alarm signal sent by detecting the applied voltage of the measurement AC signal applied to the electrical circuit. Take measures to do so.

(Example) The present invention will be described in detail below based on an illustrated example.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, A is the power receiving room, and a transformer OT is installed on the connection line L _E connected to one of the secondary circuits of the power receiving transformer T, and the oscillator is connected through the transformer OT.
A low-frequency AC signal voltage with an output frequency of ₁ voltage V [volt] of the OSC is applied to the electric circuits L ₁ and L ₂ , and the leakage current flowing through the insulation resistance R _O and stray capacitance C _O between the electric circuit and the earth is calculated. A current transformer ZCT passing through the grounding wire L _E detects this, and the detected signal is transferred to a first amplifier AMP ₁ with a variable amplification degree, and a filter FIL ₁ whose output is tuned to the measurement AC signal f ₁ . 2nd through
The output is input to the amplifier AMP ₂ , and the output is synchronously detected by the synchronous detector MULT using the applied signal as a reference to obtain an output that is inversely proportional to the insulation resistance R _O of the electric circuit.From this, the insulation resistance value of the electric circuit is calculated. At the same time, a reduction filter is applied to remove the distorted waves in this signal.
Comparator compares this value with reference value REF ₁ via LPF
Compare with COMP ₁ . If low pass filter
If the LPF output is larger than the reference value, the control circuit CONT operates in response to the output of the comparator, and reduces the output voltage of the oscillator OSC to V ₁ (volts) for a certain period of time, for example.

By doing this, insulation resistance R _O and stray capacitance C _O
Even if does not change, the voltage of filter LIL ₁ output is
Since the voltage drops to V ₁ /V, the synchronous detector output also drops in proportion to this, making it impossible to properly monitor insulation while the oscillator OSC output voltage is dropping. Further, while the control circuit CONT lowers the output voltage of the oscillator OSC, the gain of the amplifier AMP ₁ is adjusted as described above so as to amplify the output voltage of the filter FIL ₁ by ₁ times V/V.
Controlled by CONT signal.

On the other hand, in Figure B, such as an office located near the electric lines _L1 and _L2 and monitoring abnormalities in the electric lines, for example, the installed electric line on the side where the grounding wire L _E is installed, that is, the neutral wire L After detecting the voltage generated between ₂ and the grounding point E ₃ of the newly installed type 3 grounding wire through the high input impedance amplifier AMP ₃ , the commercial frequency component is removed and only the signal component of frequency ₁ is generated. The voltage drop time or intermittent pattern of the AC signal flowing in the electric circuit is detected by detecting it in _the rectifier circuit DET through the wave generator FIL ₂ , which extracts it, and then comparing it with the reference voltage REF ₂ in the comparator COMP 2, and detects an alarm. Input to circuit ALD. This alarm detection circuit
In ALD, after identifying which of various predetermined alarm signals the falling time of the AC signal voltage applied to the electrical circuit or its intermittent pattern is, an alarm is displayed accordingly. A brief explanation of the reception and reception of signals during this time is as follows.

That is, FIG. 2 is a time chart explaining one embodiment of the signal processing method related to the alarm signal transmission method of the present invention.

Now, let us consider the case where an alarm signal is generated and transmitted for T time from time t ₁ to t ₂ as shown in FIG.
By controlling the output voltage V of the oscillator OSC that supplies the alternating current signal to the electrical circuit in which the abnormality has been detected as shown in b of the same figure, the alarm signal rises at t ₁ for an hour T ₁ as shown in c of the same figure. And at the end of the alarm signal t ₂ , it is lowered to V ₁ for T ₂ hours. On the other hand, in order to receive this signal, the detected AC signal voltage may be detected, for example, the rising edge of the waveform may be detected, and an alarm signal as shown in FIG. Further, the alarm signal can also be transmitted to a central processing device or the like via a telephone line.

Next, when there are two types of signals to be transmitted, for example, when transmitting two types of warning signals and abnormal signals, the signal processing method is to use unique time lengths (4 types ), the oscillator output voltage may be reduced by V ₁ as described above, or each may be assigned a unique sign and steps may be taken to intermittent the fall of the oscillator output in accordance with the sign.

In the insulation detector constructed and operated as described above, as is clear from the above explanation, the application of the measurement AC signal to the electric circuit is not stopped when transmitting the alarm signal, so the insulation detector does not stop normally during the transmission of the alarm signal. Insulation monitoring can be performed, and it is also possible to transmit not only insulation monitoring results but also other alarm signals such as an abnormal rise in oil temperature of a power receiving transformer without affecting insulation monitoring.

In addition, in the above-mentioned embodiment, when determining the drop point of the oscillator output voltage, if it is performed at the timing such as the zero crossing point of the output waveform, the low pass filter FIL ₁
This is more desirable because it can prevent transient noise such as clicks in the output. In addition, if necessary, the control circuit will take measures such that the insulation monitoring results are not used for a certain period of time after the gain of amplifier AMP ₁ is changed.
By using CONT, it is also possible to remove the effects of short-term transient noise.

It is also obvious that the gain of amplifier AMP ₂ can be changed instead of changing the gain of amplifier AMP ₁ , but it is also possible to change the gain of the low-pass filter LPF output with an amplifier (not shown). be. However, it is obvious that it is necessary to take into account the influence of the time constant of the system from FIL to LPF when deciding. Furthermore, although the above example shows the case where the applied voltage is lowered to V ₁ , it is unnecessary to explain that even if the applied voltage is increased to V ₁ , the object of the present invention can be achieved by the same procedure.

In the transmission method of the above embodiment, the alarm signal is unilaterally transmitted from point A to point B, and it is not possible to respond at point B as to whether it has been correctly received. This will be even more convenient if the following method is added. That is, the output of the amplifier AMP ₂ is applied to the input terminal of the separately provided detection circuit, and the applied signal for measurement is shifted in phase by 90° via a 90° phase shifter (not shown), which is separately provided. It is possible to configure a detector that obtains a value proportional to the stray capacitance to ground C _O by applying it to the other input terminal of the synchronous detection circuit and detecting the leakage current component, that is, the reactive component, which is 90 degrees ahead of the applied signal for measurement. can. Therefore, transmission is performed from point A to point B, and if reception is possible at point B, the signal is transmitted at point B for a certain period of time between the grounding cable shown in Figure 1 and the third type grounding, that is, the amplifier AMP ₃ .
A capacitor C is applied between the two inputs of . As a result, the detector of the stray capacitance to the ground increases by the value of the applied capacitor (C + C _O ), and by knowing C at point A, it is possible to transmit data at point B at point A. You can know that the signal is being received correctly. If the transmission time of the alarm signal from point A is fixed depending on the type of signal as shown in Figure 2, then the capacitor application time from point B should be made proportional to this time length. Alternatively, if you select and use a capacitance value proportional to the time length, you can check at point A what type of signal was determined to be received at point B, and if it corresponds to the one sent at point A. If not, you can take steps such as retransmitting it at point A, or you can force the insulation to deteriorate by applying a resistor instead of a capacitor, and then send the confirmation signal back to point A with a change in insulation resistance. .

Further, the voltage applied by the capacitor may be encoded and applied. Furthermore, when detecting the voltage applied to the capacitor at point B, it is also possible to detect an increase in the leakage current component of frequency ₁ , determine that this has also been applied, and use this as a confirmation signal.

In the above embodiments, the case of a single-phase two-wire system was explained, but it is equally applicable to a single-phase three-wire circuit or a three-phase three-wire circuit in which one end of the secondary side is grounded. is clear.

Furthermore, when applying an AC signal voltage, instead of cutting the ground wire L _E and applying the voltage to it as shown in the example, connect the oscillator to a ring type transformer with the ground wire L _E passing through it, or ground the oscillation transformer. The wire may also be passed through it.

(Effects of the Invention) As explained above, the present invention allows alarm signals detected in the power receiving room to be sent to the alarm display panel or transmitter by using the existing electric circuit without installing a new signal cable. Not only can alarm signals be reliably transmitted to manned offices, but insulation can also be monitored continuously during alarm signal transmission, making it extremely simple and economically reliable to transmit alarm signals, etc. Effective.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
FIG. 2 is a time chart showing the signal processing method. T...Power receiving transformer, _L1 , _L2 ...Electric circuit, Z...
...load, L _E ...ground wire, ZCT ...zero-phase current transformer,
OT...transformer, OSC...oscillator, AMP ₁ ,
AMP ₂ and AMP ₃ ...amplifier, DET...rectifier,
COMP ₁ , COMP ₂ ... Comparator, REF ₁ , REF ₂ ...
Reference voltage, CONT...control section, FIL ₁ , FIL ₂ ...
Filter, ALD...Alarm detection circuit, MULT
... Synchronous detection circuit, R _O ... Insulation resistance, C _O ... Stray capacitance to ground, LPF ... Low pass filter (or integrator).

Claims (1)

[Claims] 1. A measuring AC signal voltage V [volt] having a frequency _f1 different from the commercial power supply frequency is connected to the electrical circuit via the grounding wire.
is applied, and among the leakage current of the measurement AC signal that returns to the grounding wire, the in-phase component with the measurement AC signal is detected, and the magnitude is compared with one or more predetermined reference values. In an insulation detector that generates one or more insulation deterioration alarm signals depending on the insulation deterioration alarm signal, the measurement AC signal is continuously or intermittently transmitted for a predetermined length of time depending on the type of the insulation deterioration alarm signal. While changing the voltage applied to the measurement AC signal by lowering or increasing the voltage to V ₁ [volts] and configuring the detection value of the in-phase component of the measurement AC signal to be ₁ times V/V during this period. In addition, at the point where the various alarm signals are received, the type of alarm sent out by detecting a change in the voltage value of the measurement AC signal applied to the electric circuit. A method for transmitting an alarm signal for an insulation detector, characterized in that the alarm signal is transmitted by an insulation detector. 2 While changing the voltage value of the measurement AC signal applied to the electric circuit, the in-phase component detection value is changed to V/
The insulation detector alarm signal transmission method according to claim ₁ , wherein the means for increasing V by 1 controls the gain of an amplifier in a circuit that derives the leakage current that returns to the grounding line. . 3 While changing the voltage value of the measurement AC signal applied to the electric circuit, the in-phase component detection value is changed to V/V.
2. The alarm signal transmission method for an insulation detector according to claim ₁ , wherein the means for multiplying V _{by 1} multiplies the detected in-phase component detection value by V/V by 1.