SU379910A1 - METHOD OF MEASURING THE TIME OF OPERATION OF THE RELAY TO REDUCE THE FREQUENCY - Google Patents

Description

The proposed method relates to instrumentation technology and is intended for use in power protection devices for emergency operation.

Measurement traces are known based on comparing the response times of the test and reference relays.

The peculiarity of the proposed method is that after each measurement cycle, the counter is reset at the time point of the meter reaches the set value, the pulse count is transferred to the continuous count of the reference pulses until the relay under test triggers.

This allows for improved measurement accuracy.

The proposed cut-off is illustrated in FIG. I, av.

A voltage is applied to the relay under test, the shape of which is shown in FIG. ,but. The positive half-waves of this voltage are the number-pulse modulation of high-frequency pulses, the result of which is the receipt of bursts of pulses (Fig. 1.6).

These bursts of pulses are counted using a high-speed counter, and at the end of each batch of pulses the counter is reset to zero if the relay in question fails to operate (Fig. 1 corresponds to the case when such a reset is performed after the first and second pern relay).

The frequency of operation (the setpoint of the monitored relay) is known in advance, therefore, the number of high-frequency pulses corresponding to this frequency is known in advance. The pulse counts are preadjusted in such a way that when they count the number of pulses,

corresponding to the frequency of operation, a signal appeared at the output of the counter. This policy prevents the counter from being reset to zero after the end of the high-frequency impulse

modulator, and the transition due to unmodulated high-frequency pulse. Pulse counting is stopped when the relay in question is triggered. The graphs in FIG. 1 are compiled with reference to the case when in the third period the frequency supplied to the relay is sufficiently sufficient for it to operate, counting from the time ti to the time tz counts the specified number of pulses. Therefore, since time / 2 reset

counter reading does not occur n the counter continues to read non-modulated pulses. At the time point / s, the time relay in question is triggered and the counting of the modulated impulses stops (the counter is stopped).

The response time / cp of the relay being investigated is determined by the formula

tcp PT,

where n is the number of pulses registered by the counter;

T - the duration of the period of high-frequency pulses.

The error of the proposed method is due to the discrete nature of the time measurement / EP. It can be reduced to the desired value by increasing the pulse frequency.

FIG. 2 shows a block diagram of the device, with the aid of which the proposed method is carried out.

The input of the investigated relay 1 in the device is connected to the output of the low-frequency generator 2. The frequency of this generator during the measurement process gradually decreases. The input of the low-frequency generator is also connected via diode 3 to a number-pulse modulator 4, the input of the modulator to the generator output 5 high-frequency pulses, and the output of the modulator to the first input of the switch 6. The high-frequency pulses from the other input of the switch and the output of the switch is with the counting input of pulse counter 7. The output of the low-frequency generator 2 is also connected via diode 8 and key 9 to the reset input of pulse counter 7. The output signal of the counter is fed to switch 6 and key 9 for control or their work.

The circuit shown in FIG. 2, works in the following way.

Next, relay 1 from the low-frequency generator is supplied with alternating voltage, the frequency of which gradually decreases, and high-frequency pulses from generator 5, whose frequency is constant, are supplied to the number-pulse modulator 4. In the case of positive half-waves of alternating voltage, a number-pulse modulator transmits high-frequency pulses, through switch 6 they pass to the counting input of counter 7 and the counter registers them. At the end of the pulse train, i.e. when the half-wave of the mixed voltage is negative, it enters through diode 8 and the closed key 9 to the reset input of counter 7 and the counter resets its readings to zero. This takes place when the frequency of the generator 2 does not reach the frequency of operation of the relay under study /. If the frequency of generator 2 reaches the frequency of the relay, then at the end of the first half period of this frequency

the counter records a predetermined number of pulses and a signal appears on its output. This signal switches the switch to the right position (according to the scheme in Fig. 2), and unmodulated pulses begin to flow to the counter directly from the output of the high-frequency generator 5. In addition, the output signal of the counter acts on the key and turns it off. This prevents the counter from resetting. Further counter

continues to count the high-frequency pulses until the relay under study is activated, after which its contacts stop the counter. In the counter readings, the relay response times are calculated by

previously given formula.

To simplify FIG. 2, adjustment elements are not shown. These elements include a speed regulator for reducing the frequency of the low-frequency oscillator and the device, allowing it to change the number of pulses, starting with which a signal appears at the output of the counter. Both of these devices are part of a low frequency generator circuit and, accordingly, a pulse counter.

Subject invention

The method of measuring the time of operation of the relay is frequency computation, based on transforming the period of the frequency under investigation into the number of pulses and counting the number of reference pulses, characterized in that, in order to improve the accuracy, after each measurement cycle, the output t is reset at the time when the meter readings reach the set value, the counting is transferred to the continuous counting of the reference pulses until the moment the relay under test is triggered.