JPS601806B2 - Momentary interruption detection method for signal transmission system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detecting adjacent disconnections among transmission failures that occur in a signal transmission system that transmits and receives signals by frequency modulating them.

As a useful method for signal transmission, a frequency modulation method as shown in FIG. 3 has been widely adopted.

To explain the outline of this system, in the figure, S is an information signal to be transmitted, and 11 is a frequency modulation means which outputs a frequency signal 11' corresponding to the signal S. 12 is carrier wave sending means; 11'
This is a so-called carrier means for collectively transmitting a large number of frequency signals including .

A, , A2 are transmitting and receiving antennas, respectively, through which signals are transmitted. Reference numeral 14 denotes a carrier wave receiving means, which performs a function corresponding to and opposite to that of the transmitting means 12.

Therefore, in this world, a frequency signal 15' corresponding to the signal 11' is obtained. 15 is a frequency demodulation means;
Derive signal 0.

In the signal transmission system configured in this way, if no transmission failure occurs in the communication path consisting of the frequency modulation means 11, the carrier means 12, 14, and A, , A2, the signal 0 becomes the signal S.
In addition, signal 15' corresponds to signal 11' and should have the same waveform.

That is, for example, as shown in FIG. 4, we will consider an apparatus that uses the center frequency of water Hz to frequency-modulate a signal with a frequency deviation width of ±lkHz by 60 degrees and transmits and receives the signal. Fourth
In the figure, S is the information signal to be transmitted and is 6 capes z. ei and fo are the input voltage and output frequency of the frequency modulation circuit 11. ei and fo are the input voltage and output frequency of the frequency modulation circuit 11. fi and eo are the input frequency and output voltage of the frequency demodulation circuit 15. In this way, an information signal 0, which is the same as S, is obtained. However, in reality, this relationship may no longer hold due to a transmission failure, so a means to detect the transmission failure and take countermeasures is required.

As this monitoring means, the systems shown in FIGS. 1 and 2 are conventionally known. In the former case, for example, as shown in Figure 1a, the original frequency band of the communication line is 1.0kHz to 3.0kHz.
z, the frequency band to be used is 1.0 to 2. For example, 2. Salvation is a noise or Fuji cutting detection point, 2. Pig cuts can be detected by sending out a pilot signal with a spherical ratio from the transmitting end and monitoring the level of this pilot signal at the receiving end. Conversely, noise can be detected by setting the pilot signal to "0", that is, no signal, at the transmitting end and monitoring the output level of the pilot frequency passing filter at the receiving end. In the latter method, the communication line 1 is, for example, CH, ~C
When receiving the three communication channels of H3, a separate channel C ratio is provided for detecting noise or instantaneous interruption. In FIG. 2, 14 is a carrier wave receiving means, 15-1 to 1
5-4 is a frequency demodulation means, and especially 15-4 is a noise or instantaneous interruption detector. The frequency signal of channel C is set to a constant value in the same way as the pilot frequency in FIG. 1 to detect noise and instantaneous interruptions. Although these methods are effective when used alone or in combination, they cannot be applied to fields that require high speed.

For example, in FIG. 1, the pilot frequency passing filter must have high filter selectivity in order to select only the pilot frequency, and therefore the filter time constant is large. This means that when using the output of the signal frequency pass filter in the subsequent stage, it is necessary to delay it until a confirmation signal is obtained from the pilot frequency pass filter that there is no noise or that the neighbor is insulated. It means. In the system shown in Figure 2, certain types of transmission failures are
Although noise was generated at the same time in H3 and CH4, countermeasures were taken to prevent this, but the inventors discovered that the noise actually occurs with a time difference of several milliseconds. In this case as well, it is necessary to provide a delay time corresponding to the noise variation time difference. and,
It has been found that not only is high-speed detection not possible, but transmission failures that are essentially undetectable occur.

This is a so-called adjacent disconnection, and the frequency signal 15' is normally a sine wave as shown in the top row of FIG.
As shown at the top of the figure, the magnitude of the frequency signal 15' becomes approximately 0 level. It has been discovered that the cause of pig cutting is a drop in the electric field strength in the micro line due to rainy weather, and experience has shown that there are cases in which the pilot frequency in Figure 1 or the monitoring channel C in Figure 2 is not affected at the same time. It was done. In the end, the only way to detect such instantaneous interruptions without affecting other frequencies or channels is to monitor the frequency signal itself. As for monitoring the frequency signal itself, it is known that a signal with a period shorter than the period T at the upper limit frequency of the used frequency band or a signal with a period longer than the period T2 at the lower limit frequency is detected and treated as noise. However, since the time To of the instantaneous interruption is between T and T2, it cannot be distinguished from the regular frequency signal. This instantaneous interruption occurs in the frequency demodulating means 1
It has a great influence on the output of 5. This will be explained in detail. First, a specific example of the frequency demodulation means 15 is shown. This is a frequency modulation protection relay layer (hereinafter referred to as FM relay).
As is well known from Japanese Patent Publication No. 43-2982, which is the principle patent of This can be achieved by discharging the capacitor for the remaining time until the next change. Of course, other well-known general techniques for frequency-to-voltage conversion can be used, but in any case, the integral characteristics of a capacitor or the like are utilized. To make it easier to imagine, if we assume that a constant frequency signal is being sent out, the repeated charging and discharging of the capacitor results in an analog output with a constant average value (0 (V) in Figure 4) at its terminal. is obtained. According to this method, when the frequency is higher than 2 (K side), the duty (integration period/discharge control) increases and the analog value increases, and conversely, when the frequency decreases, the duty decreases and the analog value increases. becomes smaller. During the first stage of magic, there is no change point in the rectangular signal, and during this period, the discharge continues unilaterally and the output decreases. The specific effects of a drop in output due to a momentary power outage will be explained using the FM relay as an example. The FM relay transmits and receives detected currents at each terminal of the power transmission line to each other by frequency modulation, calculates the difference current, and uses this to determine whether to trip the sheath breaker. Here, for example, in the case of a 50Hz power transmission system, the time (approximately 3.3 milliseconds) corresponding to 60 (degrees)
When the difference current is obtained, the breaker is tripped, so
Depending on the duration of the instantaneous interruption, there is a risk that the chopper or cutter may be erroneously or disconnected. Furthermore, even if the instantaneous interruption is short-lived, if the interruption continues, the output of the frequency demodulation means 15 will shift, leading to the failure of the sheath breaker. In other words, the analog value that has decreased due to the Fuji disconnection will rise to 0 (V) by the subsequent re-reception of the 2 (kHz) signal, but if there is a momentary interruption again before it reaches 0 (V), the analog value will increase again. Output decreases. As described above, it is clear that when the momentary interruption period is shorter than the charging time constant of the capacitor, the analog output continues to decrease, leading to malfunction. The effects of instantaneous interruptions also occur in devices other than FM relays, and this is a problem that requires some kind of countermeasure. In view of the above, an object of the present invention is to provide a method for detecting instantaneous interruptions in a signal transmission system that can reliably detect instantaneous interruptions at high speed.

In the present invention, the received frequency signal 15' itself is monitored.

Then, by squaring this and extracting only the alternating current component, and monitoring the time, pig cut detection is performed. An embodiment of the present invention will be described in detail with reference to FIG. In FIG. 5, reference numeral 15' denotes the frequency signal received through the transmission line after being frequency modulated by the information signal S as explained in FIG. 3, that is, the output of the carrier wave receiving means 14.

20 is a transformer for insulation, 15 is a frequency demodulation circuit, and based on this output signal, for example, a relay (not shown) is operated.

30 is a multiplier for multiplying the frequency of the frequency signal to n times the frequency, and as shown in FIG.
, filter 303, and squaring circuit 302 are arranged in cascade.

It is a four-way waveform converter, and a rectangular waveform proportional to n times the frequency of the input frequency signal 15' is obtained as its output.

50 and 60 are timers for measuring the time width of n-fold rectangular wave output "1" and no output "0". This is a time width measuring circuit which outputs an output after a certain period of time after the level of the signal becomes "0", and includes, for example, an integrating circuit 1 and a bell detecting circuit LD as shown in the figure.

70 is an OR circuit for taking the OR of the outputs of 50 and 60; for example, this output signal is used to lock the operation of the above-mentioned relay.

In the device of the present invention described above, the physical meaning of squaring the frequency signal 15' is to make the difference between the mixed frequency signal and the momentary interruption extremely sharp, so that they can be easily distinguished.

As mentioned above, there is a relationship between the instantaneous interruption time To and the period T, , T2 of the upper and lower limit frequencies of the frequency band used, so that the frequency signal and the instantaneous interruption are expressed in terms of time. They cannot be distinguished from each other based on the difference in length. but,
If we treat the frequency signal as a sine wave AC signal and the instantaneous interruption as a DC signal, and perform square processing, the sine wave AC signal becomes a signal with twice the frequency. For example, the square value of a sine wave of i cosmwt (where, is the angular velocity and t is the time) is expressed as the following equation: a sine wave AC signal (1/order o
It is a composite value of t) of s2 and 1/2 of the DC component. i2ni(
Sin's t)2 = Kyojuyo.

15' and 301 in FIG. 6 of S2 show the waveforms of i and i2, where i is inverted to positive or negative, but i2 does not take a negative value.

The filter 303 in FIG. 8 removes 1/2 of the DC component and extracts only 1/2 of the AC component, t. The square value of the output of filter 303 is expressed as 302. In this way, if it is a sine wave alternating current amount, a sine wave alternating current amount with an angular velocity of 2n can be obtained by squaring. However, it is the number of times of n' square processing. On the other hand, the waveform of the instantaneous interruption period, which is the DC amount, remains the DC amount no matter how many times it is squared. In FIG. 7, the square value i2 of the instantaneous interruption period of signal i is zero. However, although the magnitude of the instantaneous interruption period of the further square value i4 of i2 is a DC constant value, it becomes a different value depending on the phase in which the instantaneous interruption occurs. The example in FIG. 7 shows that a momentary interruption has occurred at the zero point of the frequency signal i, and i4 is the maximum positive value. In this way, the sine wave becomes a higher harmonic signal due to the squaring process, while the direct current remains unchanged, and the relative difference in time length between the two becomes noticeable. Fig. 11 is a diagram showing that a relative difference in time length occurs, and shows the frequency signal i and its square value i2 when frequency modulated in the range of 1 (k output) with 2 (kHz) as the center frequency. It shows the relationship between the period and the instantaneous interruption time circle.

First, the period of signal i is from 1 (s) to 0.33 (s)
, and since the adjacent time To also falls within this range, a clear distinction cannot be made. In addition, 1 (k criticism) or less, 3 (k
Since a sine wave of Hz) or higher can be detected by another means, i is assumed to be 1 (k out) to 3 (k out) here. On the other hand, the frequency of 2 is 2 (k generation) to 6
(kHz), and its period is 0.167 (skin s) to 0
．． 5 (desk s). Furthermore, i4'ma4 (kHz) ~ 12
(kHz), 0.083 (desk s) to 0.25 (skin s). During these squaring processes, the instantaneous interruption period To remains fixed, so when squaring processes are performed twice, it becomes 0.25 (m
If a signal with a length longer than s) is detected, this can be considered as an adjacent cut. In this example, squaring twice is effective for instantaneous interruption detection, but the frequency band used is limited.
Needless to say, processing may be required once or three or more times depending on the momentary interruption time. According to the present invention, not only is it easier to distinguish by increasing the relative time difference, but in principle, the higher the number of times of squaring processing, the faster detection can be achieved.

If i8 is determined by squaring p, its frequency is 8(k
Hz) to 24 (kHz), and the period is 0.042 (m
s) to 0.125 (ms). In this case 0.12
It is only necessary to detect the presence of a signal of 5 (skin s) or more, and it is clear that the speed can be faster than in the cases of i2 and i4 due to the shorter confirmation time. Note that although this diagram focuses on the period, the actual confirmation time may be shorter.
In the case of i4, 0.25 (ms) is the time required for one wave, and considering that the sign is reversed every half cycle, 0.12
It will take about 5 (desk) + Q. From the above, in the present invention, four waveform conversion circuits having appropriate slice levels are introduced to convert the square value into a rectangular wave.

The positive and negative waves of this rectangular wave are measured by timers 50 and 60, respectively, and when the timers produce outputs, it is determined that there is a pig cut. As is clear from comparing Figures 6 and 7,
As long as the frequency signal is received correctly, the timer will not produce an output, but if a momentary interruption occurs, the waveform with the DC component biased to one side will continue for a long time depending on the momentary interruption period, so waveform conversion is necessary. Correspondingly, the circuit 40 also has a "1" or zero period for a long time, and the timer 50 or 60 produces an output. This instantaneous power failure detection output is used in FM relays to block relay output, but in other fields, it is used for various purposes, such as abnormality display and information retransmission requests. In principle, the time required for detection according to the present invention can be reduced by increasing the multiple n of the transmitter 30 and by reducing the time of the timers 50 and 60.

In practice, there is a possibility that the instantaneous interruption detection circuit itself malfunctions, so in order to reduce the confusion caused by unnecessary instantaneous interruption detection, it is not only meaningful to shorten the detection time; Each of them may be determined to such an extent that instantaneous interruption can be detected immediately before the relay malfunctions using the derived signals. In summary, according to the present invention, it is possible to directly monitor the frequency signal itself, and furthermore, the pig cutting detection can be completed before the response of the device that uses this frequency signal, thereby ensuring that unnecessary confusion caused by pig cutting in the device is avoided. It can be prevented.

Next, FIG. 8 is a diagram showing an example of the multiplier 30 in the embodiment described above.

The frequency signal is applied to input terminals X and Y of a multiplier 301, where a square operation is performed. From this calculation output, only the AC component is derived via C and R forming the filter 303 for the DC component, and is added to the input terminals x and Y of the multiplier 302. The results of this calculation are output as waveforms as shown in FIGS. 6 and 7. FIG. 9 is a diagram showing another example of the multiplier circuit according to the present invention. In the figure, the input signal is rectified by Rec, amplified by AMP, and inputted to a resonant circuit Res that tunes to the n-times frequency in order to obtain a frequency n times proportional to the input signal frequency in order to increase the pig cutting detection speed. The output is used to obtain similar results. However, in this case, since a resonant circuit is required to obtain n-fold harmonics, it is not necessarily advantageous for frequency modulation FM systems with large frequency deviations. In addition, in the previous embodiment shown in FIG. 5, the output i4 of the multiplier 302 was applied to four waveform conversion circuits as shown in the waveform in FIG. 7, and the time length was monitored. As shown in Fig. 10, the multiplier output signal is subjected to a flat bath with C' and R' of the smoothing circuit to derive the DC component, and the magnitude of this output signal can be detected as an appropriate value. Disconnection can be detected. This first
In the case of the embodiment shown in Figure 0, 30 is explained using the waveform diagram in Figure 7.
When the output of 2 changes alternately, the DC 〇 is R' and C'
During the period when adjacent disconnection occurs, the DC output becomes as shown in FIG. 7 (maximum value in this example). The level detection function shown in Fig. 10 is equivalent to the circuit consisting of 40, 50, and 60 shown in Fig. 5, and for example, the level detection function sets a threshold value of level ○1Q' and a threshold value of ○'-Q. , respectively, and if the output length is monitored, a momentary interruption can be detected. Also, although not shown, since the output frequency of the multiplier 30 in FIG. That is clear.

In this case, in the above-mentioned embodiment, the linear range required for demodulation is four times the 4K to 1 level, but the difference between the demodulated carrier signal and the low-pass filter for removing ripples becomes large, resulting in large ripple attenuation. Therefore, demodulation can be performed with a good S/N ratio. Furthermore, since the cutoff frequency of the low-pass filter can be increased, there is also the advantage that the time required for demodulation can be shortened.

[Brief explanation of the drawing]

1, 2, and 3 are diagrams for explaining conventional noise detection methods, FIG. 4 is a diagram for explaining an example of FM modulation related to the present invention, and FIG. 5 is a diagram for explaining an example of FM modulation related to the present invention. 6 and 7 are waveform diagrams illustrating the operation of the present invention; FIGS. 8, 9, and 10 are diagrams supplementing the explanation of the embodiment of the present invention; FIG. 11 is a diagram illustrating the effects of the present invention. 14... Carrier wave receiving means, 20... Insulation transformer, 15... FM demodulation circuit, 30... Multiplier,
40... Waveform conversion circuit, 50, 60...
・Timer, 70...OR circuit. ．． Multi ′ Cause 2 Mycelia 3 Diagram 4 Diagram 5 Multi 3 Box 8 Diagram Multi 7 Younger brother wo diagram Fin diagram Multi ′′ diagram

Claims (1)

[Claims] 1. In a signal transmission system, a means for converting a frequency modulation signal corresponding to an information signal derived from a carrier wave into a frequency that is n times higher, and a waveform conversion circuit for rectangulating the signal obtained through the converting means at a predetermined level. , and a timer that outputs when the rectangular output of the waveform conversion circuit continues for a predetermined time or more.