RU2220470C1 - Frequency relay - Google Patents

Abstract

FIELD: electrical engineering; checking commercial frequency for deviation from rated value. SUBSTANCE: relay that functions as overfrequency and underfrequency relay at a time has isolating transformer, frequency filter, frequency-dependent component, three comparators, two pulse shapers, AND gate, pulse counter, nonrecursive filter, final element, delay circuit, and clock generator. EFFECT: enlarged functional capabilities. 1 cl, 3 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.

 The closest in technical essence to the claimed is a device containing a series-connected isolation transformer, a frequency filter, the first phase-shifting frequency-dependent element, the first threshold block, the element BAN, pulse expander, amplifier and actuator, the second phase-shifting frequency-dependent element, the input of which connected to the output of the frequency filter, and the output through a key connected to the second input of the first threshold block, a voltage divider connected in series, turn is connected to output frequency filter, the 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.

 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, in addition, a second comparator, as well as an actuator, are introduced a pulse shaper whose input is connected to the output of the first comparator, and the output is to the first input of the AND element, the output of which is connected to the counting input of the pulse counter s, the output of which is connected to the information input of a non-recursive filter, the output of which is connected to the input of the third comparator, the output of which is connected to the input of the actuating element, the delay element, the output of which is connected to the input of the zero pulse counter, the second pulse shaper, the input of which is connected to the output the second comparator, and the output with the second input of the And element, with the input of the delay element and with the clock input of the non-recursive filter, one-shot connected in series, the output of which is connected with the installation inputs of the counter and non-recursive filter, and a clock pulse generator, the output of which is connected to the third input of the And element, while the input of 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 is a non-recursive filter, FIG. 3 is a timing diagram explaining their operation.

 The frequency relay (Fig. 1) contains a series-connected isolation transformer 1, a frequency filter 2, a phase-shifting frequency-dependent element 3, a first comparator 4, a first pulse shaper 5, an And 6 element, a pulse counter 7, a non-recursive filter 8, a third comparator 9 and an actuation element 10, a delay element 11, the output of which is connected to the zero input of the pulse counter 7, the second comparator 12 is connected in series, the input of the second is connected to the output of the frequency filter 2 and the second pulse shaper 13, you the stroke of which is connected to the second input of the And 6 element, to the input of the delay element 11 and to the clock input of the non-recursive filter 8, one-shot 14 connected in series, the output of which is connected to the installation inputs of the pulse counter 7 and the non-recursive filter 8, and a clock pulse generator (GTI) 15 the output of which is connected to the third input of the element And 6.

 The non-recursive filter 8 (Fig. 2) contains sequentially connected cells of the shift register 16-1 ... 16-k, the outputs of which through the corresponding multipliers 17-1 ... 17-k by 1 / k, where k is the number of cells the shift register, connected to the input of the adder 18, 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 constructive implementation of the phase-shifting frequency-dependent 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 phase-shifting frequency-dependent element 3 by the 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, which is fed to the start-up input of the GTI 15 and to the installation inputs to the initial non-recursive state filter 8 and pulse counter 7. The initial state of the non-recursive filter 8 and pulse counter 7 corresponds to the pulse duration, expressed in the number of pulses of the GTI 15, corresponding to the time interval, is proportional nomu largest allowable frequency shift of the input voltage with respect 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 the phase-shifting frequency-dependent element 3. Depending on the deviation of the frequency of the first harmonic of the input signal from the nominal, the phase-shifting frequency-dependent 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 as much as possible in time and therefore, through the And 6 element, a relatively large number of pulses will arrive at the counting input of the counter 7 during their duration. The calculated number at the trailing edge of the pulse of the second shaper 13 is transferred from the counter 7 to the non-recursive filter 8, where it is averaged to exclude the influence of random failures (interference), after which (due to the small delay in the time the signal is overwritten from the counter 7 to the non-recursive filter 8 in the delay element 11 ) counter 7 is reset and thereby becomes ready for the next counting of pulses of the GTI 15, passed through the element And 6. If the frequency shift of the input voltage exceeds the permissible value, then the pulse coincidence time at the outputs the first 5 and second 13 shapers becomes insignificant, and the signal at the output of the non-recursive filter 8 becomes extremely small, which 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.

 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.

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, in addition, a second comparator, and also an actuating element, characterized in that the first short-pulse shaper is introduced by the signal difference, the input of which is connected to the output of the first comparator, and the output - with the first input of AND element, the output of which is connected to the counting input of the imp LSS, the output of which is connected to the information input of a non-recursive filter, the output of which is connected to the input of the third comparator, the output of which is connected to the input of the actuating element, the delay element, the output of which is connected to the input of the zero pulse counter, the second driver of the short pulse by the signal difference, the input which is connected to the output of the second comparator, and the output to the second input of the AND element, to the input of the delay element and to the clock input of the non-recursive filter, the same series connected a brother, the output of which is connected to the installation inputs of a pulse counter and a non-recursive filter, and a clock pulse generator, the output of which is connected to the third input of the And element, while the input of the second comparator is connected to the output of the frequency filter.

Images