RU2220472C1 - Frequency relay - Google Patents

Abstract

FIELD: electrical engineering. SUBSTANCE: relay designed to check for commercial frequency deviation from rated value and to perform both overfrequency and underfrequency relay functions at a time has isolating transformer, frequency filter, frequency-dependent component, four comparators, two pulse shapers, two AND gates, two pulse counters, two nonrecursive filters, final element, delay circuit, monostable multivibrator, and clock generator. EFFECT: enlarged functional capabilities. 1 cl, 6 dwg

Description

 The invention relates to electrical engineering and can be used as a frequency relay.

 A device is known that contains a series-connected clock pulse generator, a binary pulse counter, a decoder, a pulse shaper and an actuator made in the form of a transistor [1].

 The disadvantage of this device is the relatively narrow functionality that does not allow its use as a frequency relay.

 Closest to the technical nature of the claimed is a device containing a series-connected isolation transformer, a frequency filter, a first frequency-dependent element, a first threshold block, an element BAN, a pulse expander, an amplifier and an actuating element, a second frequency-dependent element, the input of which is connected to the output of the frequency filter, and the output through the key is connected to the second input of the first threshold block, a voltage divider connected in series, the input of which is connected to the output a frequency filter, a second threshold unit and differentiating element, the output of which is connected to the second input of the differentiating element and the trigger element having an input connected to the output isolation transformer and an output - is connected to the second input of the pulse expander [2].

 The disadvantage of the closest technical solution is the relatively narrow functionality, since it can simultaneously operate either as a frequency lowering relay or as a frequency increasing relay. In addition, in the known device there are no means for signaling the direction of the frequency shift from the nominal value.

 The required technical result is to expand the functionality by ensuring the simultaneous performance of the functions of the relay increase and decrease frequency.

 This technical result is achieved in that in a device containing a series-connected isolation transformer, the input of which is an input for connecting a controlled voltage, a frequency filter, a frequency-dependent phase-shifting element and a first comparator, a second comparator, as well as an actuating element, the first pulse shaper is introduced by a leading edge, the input of which is connected to the output of the first comparator, and the output - to the first input of the first element And, the first counter is connected in series ik pulses, the counting input of which is connected to the output of the first element And, the first non-recursive filter and the third comparator, the output of which is connected to the input of the actuating element, the second element And connected in series, the first and second inputs of which are connected respectively to the output of the second comparator and to the output of the first driver pulses, a second pulse counter, a second non-recursive filter and a fourth comparator, a delay element, the output of which is connected to the installation input to zero of the first and second pulse counters xs, a second pulse shaper on a rising edge, the input of which is connected to the output of the second comparator, and the output - to the second input of the first AND element, with the input of the delay element and with the clock inputs of the first and second non-recursive filters, one-shot connected in series, the output of which is connected to the installation the inputs of the first and second pulse counters and the first and second non-recursive filters, and a clock generator, the output of which is connected to the third inputs of the first and second elements And, while the input the second comparator is connected to the output of the frequency filter.

 In FIG. 1 is an electrical block diagram of a frequency relay; FIG. 2 - non-recursive filter, figure 3 - timing diagrams explaining their operation.

 The frequency relay (Fig. 1) contains a series-connected isolation transformer 1, a frequency filter 2, a frequency-dependent phase-shifting element 3, a first comparator 4, a first pulse shaper 5, a first And 6 element, a first pulse counter 7, a first non-recursive filter 8, and a third a comparator 9 and an actuator 10, a delay element 11, the output of which is connected to the zero input of the first pulse counter 7, connected in series to the second comparator 12, the input of which is connected to the output of the frequency filter 2, and the second the th pulse shaper 13, the output of which is connected to the second input of the first element And 6, with the input of the delay element 11 and with the clock input of the first non-recursive filter 8, serially connected single-vibrator 14, the output of which is connected to the installation inputs of the first counter 7 pulses and the first non-recursive filter 8 and a clock generator 15 (GTI), the output of which is connected to the third input of the first element And 6, the second element And 16 connected in series, the first, second and third inputs of which are connected to the outputs, with Responsibly, the second comparator 12, the first 5 pulse shaper and the clock generator 15, the second pulse counter 17, the installation input and installation input of which are connected to the outputs, respectively, of the one-shot 14 and the delay element 11, the second non-recursive filter 18, the installation and clock the inputs of which are connected to the outputs, respectively, of a single-shot 14 and a second pulse shaper 13, and a fourth comparator 19.

 The non-recursive filter 8 (Fig. 2) contains series-connected cells 20-1 ... 20-k of the shift register, the outputs of which through the corresponding multipliers 21-1 ... 21-k by 1 / k, where k is the number of cells the shift register, connected to the corresponding inputs of the adder 22, the output of which forms an estimate of the average value of the received samples on a moving over time current averaging interval.

 The actuating element 10 can be made in the form of a relay with corresponding contacts, the winding of which is directly or through an amplifier connected to the output of the third comparator 9. The first 5 and second 13 pulse shapers generate a pulse from the signal difference at the output of the corresponding first 4 or second 12 comparators from the logic level zero per logical unit level. The pulse durations correspond to a time interval proportional to the value of the allowable frequency shift relative to the nominal value. Isolation transformer 1, frequency filter 2 can have the same design as in the prototype, and an example of the design of the frequency-dependent phase-shifting element 3 is given in [2, p. 52, Fig. 1.14]. The first 4 and second 12 comparators are analog, and the third comparator 9 is digital. The remaining blocks are standard elements of electrical engineering. The power circuit, in addition to the power circuit of the single-shot 14, is omitted as non-essential.

 In FIG. Figure 3 shows the signals at the output of the frequency filter 2 (Fig. 3, a), at the output of the second comparator 12 (Fig. 3, b) and at the output of the first comparator 4 in case of frequency changes at which the phase of the signal is delayed (Fig. 3, c ) and ahead (Fig. 3, d) after passing the frequency-dependent element 3 input signal (Fig. 3, a). The shaded parts correspond to the duration and temporary position of the pulses generated by the first 5 and second 13 pulse shapers.

 The frequency relay operates as follows.

 The frequency relay is turned on at a time when the frequency of the input voltage corresponds to the rated one, by supplying power to all its elements, including the input of a single-shot 14, which generates a single pulse that goes to the start input of the GTI 15 and to the installation inputs in the initial state of the first 8 and the second 18 non-recursive filters and the first 7 and second 17 pulse counters. The initial state of the first 8 and second 18 non-recursive filters and the first 7 and second 17 pulse counters corresponds to the pulse duration, expressed in the number of GTI pulses 15, corresponding to a time interval proportional to the magnitude of the allowable frequency shift of the input voltage relative to its nominal value.

 The input voltage is supplied to the input of the isolation transformer 1, from which the frequency filter 2 eliminates the higher harmonics (Fig. 3, a). Therefore, at the output of the first second comparator 12 with a zero threshold level, a sequence of rectangular pulses is formed (Fig. 3, b), the duration of which is equal to half the period of the input voltage equal to or close to the nominal frequency. At the same time, the output signal of the frequency filter 2 is fed to the input of a frequency-dependent phase-shifting element 3. Depending on the deviation of the frequency of the first harmonic of the input signal from the nominal, the frequency-dependent phase-shifting element 3 produces a phase shift of the signal in the positive or negative direction, therefore, at the output of the first a comparator 4 with a zero threshold level, a pulse sequence is formed (Fig. 3, c, d), which differs from the pulse sequence at the output of the second comparator 12 pulses on the time axis in the direction of delay or phase advance relative to the input voltage pulses (Fig.3, b).

 The first 5 and second 13 pulse shapers generate a short pulse according to the signal difference at the output of the corresponding first 4 or second 12 comparators from the logical zero level to the logical unit level. The durations of short pulses correspond to a time interval proportional to the magnitude of the allowable frequency shift relative to the nominal value. In the absence of a shift in the frequency of the input voltage from the nominal value, both pulses will coincide in time as much as possible, and therefore, through the first element And 6, a relatively large number of pulses will arrive at the counting input of the first counter 7 during their duration. The calculated number on the leading edge of the pulse of the second shaper 13 is transferred from the first counter 7 to the first non-recursive filter 8, where it is averaged to exclude the influence of random failures (interference), after which (due to the small delay on the transient time in the non-recursive filter in the delay element 11) the first the counter 7 is reset to zero on the leading edge of the pulse of the second shaper 13 and thereby becomes ready for the next counting of the pulses GTI 15, passed through the first element And 6. If the frequency shift of the input voltage Ia exceeds the permissible value, while the coincidence pulse at the outputs of the first 5 and second formers 13 becomes insignificant and the signal at the output of the first FIR filter 8 becomes extremely small. This leads to a change in the signal at the output of the third comparator 9 from the logic zero level to the logic unit level and to the actuation of the actuator 10.

 In addition, through the second element And 16 to the input of the second counter 17 receives the pulses of the GTI 15 in the time interval of the coincidence of the pulse from the output of the second comparator 12 and the first driver 5. It is easy to see that when the phase delay of the signal at the output of the first driver 5 (Fig.3, c) relative to the phase of the signal at the output of the second comparator 12 (Fig. 3, b), the number of these pulses remains practically unchanged, therefore, at the output “greater” than the fourth comparator 19, a signal of a logical unit is observed, by which one can judge the direction of the frequency shift liruemogo voltage relative to the nominal frequency. If the phase is advanced (FIG. 3, d), then the signal of the logical unit is observed at the output “less” of the fourth comparator 19.

 Thus, thanks to the introduction of new blocks and connections, the functionality of the frequency relay is expanded, since it allows you to simultaneously respond to unacceptable deviations of the frequency of the input signal both upward and downward. At the same time, the device also generates a signal of the direction of the frequency shift relative to the nominal value.

Sources of information
1. Electrical reference book, in 4 volumes, t.2. Electrical products and devices. Under the general editorship of V.G. Gerasimov et al. - M.: Publishing House MPEI, 1998, p.390, Fig. 35.10.

 2. V.A. Andreev. Relay protection and automation of power supply systems. - M.: Higher School, 1991, p.122, Fig.3.29 (prototype).

Claims (1)

A frequency relay containing a series-connected isolation transformer, the input of which is an input for connecting a controlled voltage, a frequency filter, a frequency-dependent phase-shifting element and a first comparator, a second comparator, and an actuator, characterized in that the first short-pulse shaper is introduced along the leading edge whose input is connected to the output of the first comparator, and the output to the first input of the first AND element, the first pulse counter is connected in series, the input of which is connected to the output of the first element And, the first non-recursive filter and the third comparator, the output of which is connected to the input of the actuating element, the second element And, the first and second inputs of which are connected respectively to the output of the second comparator and to the output of the first short-pulse shaper a leading edge, a second pulse counter, a second non-recursive filter and a fourth comparator, a delay element whose output is connected to the zero inputs of the first and second counts pulse counters, the second driver of a short pulse on the leading edge, the input of which is connected to the output of the second comparator, and the output - to the second input of the first element And, with the input of the delay element and with the clock inputs of the first and second non-recursive filters, one-shot connected in series, the output of which is connected with the installation inputs of the first and second pulse counters and the first and second non-recursive filters, and a clock pulse generator, the output of which is connected to the third inputs of the first and second ele ENTOV And, the input of the second comparator connected to the output of the frequency filter.

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