SU1210178A1 - Device for protection of generator against excitation loss - Google Patents

Description

I.

The invention relates to relay protection and automation of power systems, namely, devices for detecting arousal loss.

The purpose of the invention is to increase the reliability and fast operation of the device.

Figure 1 shows the scheme of the Proposed device; on Lig.2 - the device response characteristics; FIG. 3 shows timing diagrams explaining the operation of the device.

The device circuit contains a primary current converter 1 including a current transformer 2 and a current-to-voltage converter 3, a primary voltage converter 4, including a voltage transformer 5 and. voltage converter 6 to voltage, bandpass filters 7 and 8, block 9 of formation of compared values, including phase-return unit 10, performed on an operational amplifier (op-amp), and adder 11 at the op-amp, detector converters 12 and 13, amplifier - the driver 14, the main and additional blocks 15 and 16 of the comparison, each of which contains a comparator 17 at the OS, an element 18 of time at the OS, a reacting element 19 at the OS, a logic element AND 20, a pulse generator 21, a counter 22 pulses, including a binary counter 23 and the logical element And 24 ,. Executive unit 25.

Figure 2 shows the response characteristics of the measuring organ — the main curve 26 and an additional 27, the zone 28 of the probable value of the generator resistance with the loss of excitation taking into account the slip, the generator diagram 29 of the generator resistance with the loss of the excitation, the sensor curve 30 of the asynchronous course of the excited generator hodograph 31 resistance at external short circuit of the generator operating with under-excitation and minimum active load

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Timing diagrams, as shown below, the operation of the device (Fig. 3) are constructed for the excitation loss mode, which corresponds to the locus 29 (Fig. 2). The ordinate on the time diagrams shows the output signals (U-, -Utz) of the corresponding blocks of the device.

c - 5

0

0

0

five

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The device works as follows.

Signals proportional to the current and voltage of the generator, from the outputs of the primary converters 1 and 4, pass through the band-pass filters 7 and 8 to the inputs of the block 9 to form comparable values, the outputs of which form voltages

U, (t) U, sin (); Ui (tl - U,.,

where, t1 and amplitudes of signals,

f- their phase difference. Next, the signals arrive at the inputs of the detector converters 12 and 13, controlled by the amplifier-shaper 14, and the voltages are formed at their outputs:

u, UbU;, (LJt + 4), jn (s miJi); . si nts mcJt).

The control of the detector transducers is necessary to implement the amplitude-phase principle of comparing two electrical quantities, which allows to obtain an elliptical response characteristic of the device.

Each of the comparators of the main 15 and additional 16 comparison units switches at the time when the voltages at the inverting and non-inverting inputs of the op-amp are equal. The dividers at the inputs of the comparators allow changing the switching time and thereby setting the dimensions of the main 26 and additional 27 response characteristics, the angle of maximum sensitivity of which is determined by the phase-turning unit 10 at the op-amp. The time constants — C, the chains of the time elements of the main 15 and an additional 16 comparison units determine the forms, respectively, of the main 26 and additional

27 characteristics srabatshan.

When the excitation is lost, the resistance at the generator leads changes and the resistance transducer 29 begins to move into the fourth quadrant of the complex plane to the zone.

28% of the generator resistance when the excitation is lost, taking into account the slip. At time t (fig. 3), the resistance locus 29 intersects the additional 27 response characteristic, while

The reactive element of the additional comparison unit 16 is switched off and a potential enabling account appears at the input of the installation in O of the binary counter 23.

At time t, when hodograph 29 intersects the main response characteristic 26, the reacting element 19 is switched to the OU of the main comparison unit 15, and the pulses from the pulse generator 21 start to pass to the output of the logic element And 20, which arrive at the binary counter 23 counting input. the pulse counter 22 and the input of the execution unit 2, a trigger signal appears when the -conditioning

,

where tg, is the time setting for triggering,

K - the number of pulses of the generator 21, passed to the input of the counter for time t,

 - frequency pulses.

With a partial loss of excitation or with a full in case of an excitation winding closure to the valves, the field of loss of excitation expands and the radius of the hodograph resistance exceeds the size of the area covered by the main response characteristic, which leads to the hodograph exit from the main trigger characteristic tj until the condition K / ft. is met. The responsive element 19 at the OS of the main comparison block 15 returns to the initial state, thus suspending the operation of the binary counter 23, but the counter is not updated. l is because polar plot resistance does not exceed the additional characteristic actuation and -Themes

most fixes how long the hodograph of the resistance was in the main characteristic. When the resistance hodograph is next hit, the main response characteristic at time moment 1c binary counter 23 begins to count not from zero, but from the value at which it was stopped. At the instant ts, the condition is fulfilled, and a response signal appears at the output of the device. Thus, the estimation of the residence time of the resistance hodograph within the main response characteristic I is carried out.

When the resistance hodograph leaves the additional response characteristic, the reacting element of the additional comparison unit 16 will return to the initial state and reset the pulse counter.

With an asynchronous course of an excited generator or with a short circuit, the residence time of the hodograph in the main response characteristic is much less than with a loss of excitation, and the pulse counter 22 does not have time to generate a response signal supplied to the executive unit 25, thereby eliminating the false operation of the device.

Thus, the introduction into the device of the generator generator from the loss of excitation of an additional comparison unit, a pulse counter, a pulse generator, a logic element, and an amplifier-forger, making the detector transducers controllable and connecting these elements in the proposed way allows to increase speed and reliability.

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Fig.Z

Claims (1)

DEVICE PROTECTION DEVICE FOR THE GENERATOR, containing an executive unit, Two detector transducers connected to the inputs of the main comparison unit with their outputs, the input of the first detector transducer connected through the phase-shifting unit and the first bandpass filter to the primary current transducer connected to the terminals of the generator stator windings, and the input of the second is connected to the output of the adder, one input of which is connected to the output of the phase-shifting unit, and the other through the second band-pass filter to a primary voltage converter, also connected to the terminals of the stator winding, characterized in that, in order to increase reliability and speed, an additional comparison unit, a pulse counter, a pulse generator, an I gate and an amplifier-shaper are introduced into it, and. the detector transducers are made controllable, 'the output of the amplifier-former being connected to the control inputs of the detector transducers, its input to the output of the adder, and the pulse counter output connected to the executive unit by the input of the setting 0 to the output of the additional comparison unit connected to the outputs of the detector transducers, and a counting input - to the output of the AND gate, the inputs of which are connected to the output of the main comparison unit and the pulse generator. SU-1210178