JPS5917602B2 - How do I get started? - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic inspection system for a differential current carrying protection relay device.

For multi-terminal protection of ultra-super high voltage systems, there is a frequency modulation differential current carrier protection relay system.

This converts the current value at each terminal within the protection zone into a frequency modulated signal, transmits and receives this signal to each other using a microwave line, reproduces the current at each end, and based on Kirchhoff's first law, the sum of the current vectors Σi If =o, it is determined that there is no internal accident, and if Σi\0, it is determined that it is an internal accident.The major feature is that even in the case of an internal accident that involves a spill, it has excellent selectivity between internal and external accidents.

Of course, this method requires high-speed operation because it is used for ultra-high voltage, but it also requires high precision for modulation, demodulation, waveform conversion, signal delay, etc., so it is mostly made of semiconductors. , implementation of automatic inspection was rejected due to the need to improve reliability.

Things to be aware of when performing automatic inspection using this relay method are as follows:
Since the modulation and demodulation characteristics play such an important role that they influence the relay characteristics, consideration must be given so that a wide range of inspections including this part can be carried out.

Generally, in differential power type automatic inspection, it is sufficient to reverse or set the current vector at either the own end or the opposite end.

However, even if the signal at the other end is inverted, the signal at the other end is a frequency modulation signal, so in order to inspect the demodulator as well, a modulator exclusively for inspection is prepared for vector inversion, and the current at the other end is 180%. It is necessary to perform frequency modulation with a predetermined inspection current whose phase is shifted, and to switch the output of this modulator with the signal at the other end during inspection to mark the demodulator.

When inverting the self-end signal, it is best to invert the self-end CT secondary current current for wide range inspection.

On the other hand, the former requires the addition of a switching circuit and a modulator for inspection, which poses problems in terms of reliability and economy.

In the latter case, the inverted signal is also transmitted to the other end as a frequency modulated signal, which is equivalent to an internal fault at the other end, and a trip command is issued.

Therefore, this method has the disadvantage that it is necessary to issue a lock signal to the other end in advance using a dedicated information transmission route, and to proceed with the inspection while releasing the lock after the inspection.

It may be possible to perform self-end current reversal just before the differential determination section, but this cannot be adopted as it would not require extensive inspection.

An object of the present invention is to overcome the drawbacks of the prior art shown above (i.e., to easily and reliably perform automatic inspection of a differential current carrying protective relay device including the demodulator, and to be able to perform the automatic inspection at each end independently). It provides a method.

In the present invention, if the area conversion pulse train generated in the demodulation process of the frequency modulation signal is inverted, the phase of the demodulated waveform will also be 18
Focusing on the 0° change, we added a simple reversal command section to the demodulation circuit section of the own end or the other end, and with an external command for automatic inspection,
A major feature is that by performing a reversal, it is possible to simulate an internal accident without causing trouble to the other party.

The present invention will be explained in detail below based on one embodiment of the present invention.

FIG. 1 is a block diagram of one end of a frequency modulation relay implementing an automatic inspection system according to the present invention, and for simplicity of explanation, only one phase of the relay is shown.

The instantaneous value of the system current from the current transformer CT is obtained by using a known current-voltage converter 1, a known voltage-frequency converter 2 that converts voltage into frequency, and the output is set to a predetermined magnitude and the load fluctuation is Known buffer amplifier 3 for preventing
, known resistance attenuator group 4 for adjusting transmission and reception levels
, is connected to a microwave carrier terminal equipment (abbreviated as carrier end in FIG. 1) 6 via a communication transformer group 5 for impedance matching and insulation with the communication equipment, and is connected to the microwave carrier terminal equipment (abbreviated as carrier end in FIG. 1), A proportional frequency modulated signal is transmitted to the other two terminals of the three-terminal system via output cable 7.8.

Frequency modulated signals from the other end are connected to cables 9 and 1, respectively.
0 through the corresponding isolation transformer 5 and resistance attenuator 4,
It enters the relay determination unit 14 via a known delay circuit 11 and a frequency-voltage converter 12, 13 which demodulates the frequency modulated signal back to the original voltage signal.

The frequency modulated signal at one end is processed by a known delay circuit 15 that compensates for the transmission delay from the other two terminals, and a frequency-voltage converter 16 with the same characteristics as 12 and 13 that demodulates the delayed frequency modulated signal at the end. The relay determination unit 14 is entered through the relay determination unit 14.

In step 14, based on the demodulated signal of each terminal, a vector operation to obtain the operating force necessary for relay operation and a scalar sum operation to obtain the suppressing force are performed, and if the operating force exceeds the suppressing force, it is determined that it is an internal accident. It is designed to make a judgment and issue a trip command.

The delay compensators 11 and 15 set a compensation value in accordance with M7 for the terminal with the largest transmission delay.

Reference numeral 17 indicates a control command terminal for inverting the waveform of the local wave number voltage converter 16 during automatic inspection.

Details of the frequency voltage converters 12, 13, 16 for each terminal are shown in FIG.

18 is a known Schmitt circuit, 19 is a known monostable multivib break, and 20 is a known low-pass filter.

The frequency modulation signal shown in Figure 2-1 is generated by the Schmitt circuit 18.
As a result, the signal is turned on when the signal is above the L level, and turned off when it is below the LLL/bell level, resulting in a rectangular wave shown in 11.

In the monostable multivibrator 19, the rising and falling edges of this rectangular wave are l-triggered, and a pulse train of a constant width is created as shown in FIG. 2 111.

Reference numeral 20 denotes a gate circuit, and the inverting or non-inverting output is made to enter the low-pass filter 21 according to an external command 17.

To briefly explain this filter, it can be thought of as a type of integration circuit that discharges at the mark portion of a pulse input and charges at the space portion.

Therefore, when applying a time-series pulse signal in which the ratio of the mark part to the space part changes as shown in FIG. Become.

Figure 2 1■ shows only this long-term component extracted.
By using a filter that also removes short-term components,
It is clear that the original current signal can be reproduced.

It is already well known that voltage frequency converters work in this manner.

Here, assuming that the charging time constant and the discharging time constant of the low-pass filter 21 are equal, if the proportion of time occupied by the space is larger, the output of the filter 21 increases, and the time occupied by the mark increases. If the ratio is larger, the output of the filter 21 decreases.

Therefore, when the external command 17 for inspection is given and the output of the monostable multi-bi break 19 is reversed, the ratio of the mark part to the space part is reversed, and the filter output obtained at this time is the inverted version of the original filter output. Become.

This can be understood from the fact that while the filter output for a non-inverted pulse train tends to increase, the filter output for an inverted pulse train tends to decrease.

In this way, a simulated signal of an internal accident is obtained.

FIG. 3 shows details of the gate control section 20.

In the figure, 46 and 47 are AND gates, 48 and 52 are imparks, and 49 is an or gate, and the output of the monostable multi-by-break 19 is connected to the terminal 50 (hereinafter referred to as A).

), an inspection command signal to terminal 17 (hereinafter referred to as B).

) is added. Here, if we logically express the output of each part in pool algebra using input signals A and B, the output of 48 is 100, the output of 52 is X, the output of 41 is A-B, and the output of 46 is A・B151 The output of is A-B+A-B.

Normally, the inspection command signal B is set to 0'', so the final output is A, and the input to the terminal 50 becomes the output to the terminal 51 as it is.

During inspection, the signal B becomes "1" and the inverted output A of the input A is obtained at the terminal 51.

Since this embodiment is configured as described above, no special additional circuit such as a power source for inspection is required.

By simply adding a simple gate circuit to the self-end frequency voltage converter, it is possible to automatically inspect a wide range of areas including the modulation/demodulation section without affecting the other end.

Although this embodiment has been described with reference to the case where the frequency voltage converter at the own end performs inversion, it goes without saying that the same result can be obtained even if the frequency voltage converter 12, 13 at the opposite end is inverted.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the concept of an embodiment of the present invention;
The figure is a block and waveform diagram showing an example of the frequency-voltage converter of the present invention and its operation, and FIG. 3 is an example of a gate circuit that can be employed in the present invention. 18... Schmitt circuit, 19... Monostable multivibrake, 20... Gate circuit, 21... Low pass filter, 10...
Monostable multi-output terminal, 11...Low-pass filter input terminal.

Claims (1)

[Claims] 1 A differential current carrying protection relay device that frequency-modulates the current signal from each end and transmits the frequency-modulated signal to each other via a transmission line to determine whether protection is necessary, and for demodulating the frequency-modulated signal from each end. a first means for converting a frequency modulated signal into a rectangular wave, a second means for applying a pulse with a constant width at the rising or falling point of the rectangular wave of the means, and a mark part and a space part of the pulse train of the means. Equipped with a low-pass filter that extracts a signal according to the ratio, the demodulated waveform of the low-pass filter output is inverted by inverting the phase of the pulse train output from the second means during automatic inspection of the differential current carrying protective relay device. An automatic inspection method for a transportation protection relay device that simulates an internal accident by reversing the phase.