SU1472996A1 - Device for protection of generator against loss of excitation - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection and emergency control. The purpose of the invention is to increase the selectivity and speed by eliminating false positives at low active loads and the response time as a function of the active load of a synchronous machine. The device contains current transducers 1 and voltage 2 of the stator of the generator, a remote measuring body 3, the additional output of which is connected to the R - inputs of the first 4, second 5 and third 6 triggers, first 7 and second 8 binary counters, first 9, second 10 and third 11 logical elements And, a stable frequency generator 12, connected to the HE element 13, a decoder 14 with a power sensor 15, a differential amplifier 16 with a setting block 17 connected to it, an analog-to-digital converter 18, the output of which is connected binary number comparator 19, and the executive unit 20. The power sensor, receiving information about the stator current and voltage of the generator, together with the setpoint unit and the differential amplifier generates a signal inversely proportional to the active power of the generator. An analog signal converted to a binary code by an analog-to-digital converter is compared on a binary number comparator with a code generated at the output of a binary counter that is proportional to the residence time of the end of the resistance vector in the region of the response characteristics. 2 Il.

Description

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The invention relates to relay protection and automation of power systems, and specifically to devices for detecting an excitation current.

The aim of the invention is to improve the selectivity and speed of the device.

FIG. I shows the scheme of the proposed device; in fig. 2

tripping characteristics.

The device contains a converter of current I and converter 2 of the stator voltage of the generator, a remote measuring unit 3 with the main and additional response characteristics, respectively, with the main and auxiliary outputs, the first 4, second 5 and third 6 triggers, first 7 and second 8 binary counters first 9, second 10, third 1I logic elements And, generator of stable frequency pulses 12, logical element NOT 13, decoder 4, power sensor 5, differential amplifier 16, setpoint setting 17, analog-digital Converter 18, comparator 19 binary numbers, the Executive unit 20.

FIG. 2 shows: the main 2 and additional 22 response characteristics, the resistivity locus 23 in the excitation loss mode with a high active load of the generator, the resistivity locus 24 in the asynchronous running mode with excitation at a small resistive load, the resistivity locus 25 in the mode of extra short circuit,

The device works as follows.

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0, 40

In normal or emergency modes of the generator, when the end of the resistance vector is outside the response characteristics at the R-inputs of binary counters 7 and 8, trigger-5, 4-6, and the input of the logic element HE 13, a positive potential is maintained from the additional output of the block 3. At the main output of block 3, a zero potential is maintained.

When the excitation is lost, the resistance at the generator leads changes in such a way that the end of the resistance vector moves to the fourth quadrant (curve 23) to the response characteristics (21 and 22). When the hodograph crosses the additional response characteristic (22), an additional potential appears at the additional output of block 3, as well as at the R inputs of the flip-flops 4-6 (which does not change their state) and the R inputs of the binary counters 7 and 8, and at the input of the logical element NOT 13. When a zero potential appears at the input of the logical element NOT 13, a signal of a logical unit appears at its output, which is fed to the first input of the second logical element AND

Y. Since the first trigger 4 is in the state of a logical zero, then its inverse output contains a signal of a logical unit, which is fed to the second input of the logic element AND JO. Thus, at zero potential at the additional output of block 3, the C input of the binary counter 8 through the element 10 begins to receive pulses from the generator 12 pulses of a stable frequency. Binary counter 8 operates until the resistance hodograph (23) crosses the main response characteristics (21). At the same time, the main output of block 3 is up to logical unit, the first trigger 4 goes to the state of logical unit, and its inverse output appears zero potential, which is fed to the second input of the element And 10 causes the appearance of a zero potential at its output. At the output of the decoder 14, a logical one appears - a unit when the condition

k / f t

at,

where tB is the time setting for triggering; k (is the number of pulse generator g;

12, who came to the C-whead dual counter 8; f is the pulse frequency.

The signal of the logical unit, having entered the S input of the third trigger 65, translates it1 into the state of the logical unit, which results in the appearance of a positive potential at the third input of the first element 9. The signal of the logical unit doesn’t direct output of the first trigger 4, due to a logical unit at the main output of block 3, is fed to the second input of the third

element 11, the output of which begins to pass the pulses of the generator 12 pulses of a stable frequency, arriving at the C input of the binary counter 7, the outputs of which are connected to the inputs for the first binary number of the comparator 19 double number numbers.

At the output of the power sensor 15 there is a constant signal proportional to the active power of the generator. Taking into account that the maximum active power of the generator should correspond to the minimum setting of the response time, and the minimum power to the maximum setting, the signal Urg is supplied to the ventilation input of the differential amplifier 16, which performs the U4 conversion U-Upr, where U is the positive voltage generated by block 17 setpoint and incoming to the inverting input of the differential amplifier 16. The smaller U fr, the greater the UA and vice versa - a large level

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0

5 5

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5 5

The null of the output signal of the wake sensor 15 corresponds to a small level U. Then the signal U is fed to an analog-to-digital converter 18, where it is converted into a code with which the 19 binary numbers on the comparator compare the combination of zeros and ones at the output of the binary counter 7, A 19 binary digit comparator appears as a logical unit when the condition is met, where kt is the number of pulses in the binary code; t the grottodiahs in the binary bitch from the gene ,. 1t p 1 imputis; B, is the binary code at the output of the analog-to-digital converter 18, is inversely proportional to the generator resistive load and directly proportional to the response time setting.

The signal of the logical unit on the de comparator 19 binary numbers and converts the second trigger 5 to the state of the logical unit, which results in the appearance of a positive potential at the second input of the first element AND 9.

The trigger signal arrives at the input of the execution unit 20 if there is a positive potential at the first input of the first element I 9, which corresponds to the logical unit of the main output of the block 3, i.e. the end of the resistance vector is inside the main response characteristic (2 i) „

When the end of the resistance vector comes out of the main characteristic (dotted part of curve 23) until the condition -j is fulfilled, the ground potential of the output of block 3 is zero, the state of the first flip-flop k does not change and the binary counter 7 is continued receive pulses from the generator 12 pulses of a stable frequency. Thus, it is possible to fulfill the condition. And at that moment, when the end of the resistance vector is outside the limits of the main response characteristic (21), the second trigger 5 switches to the state of the logical unit, which is present at the second input of the first element AND 9. When the end of the vector appears for the second time, the main response characteristic ( 21) at the main output

block 3, a logical unit appears, and a trigger is received at the first input of the first element 9 and the input of the execution unit 20.

When asynchronous running with excitation in the mode of small active loads, the end of the resistance vector of the main and additional response characteristics can cross up to 24) However, in this case, the value of B2 is increased (back proc ORTSNON & YIG. .-- pch-d) l wAgE does not perform-. h i-chdz kz camy lt time, in t-s, the end of the resistance vector is inside the main characteristic. lh at time

„D, and the end of the resistance vector is. You are outside the main halfergenics and s subsequently goes

 - If the additional character is used, then the device will also be activated, because when the resistance vector of the output vector is out of the dos-section. J-RT-ZD response

-e an additional output of block 3 is a wiffet logical unit, zeroed the counters and 8 and installed it in l. wecKoro zero triggers 4-6 loops, changing the set-point time for triggering t 91 (directly proportional to VT) allows you to reliably select, for example, such a mode as asynchronous with excitation.

In the case of an external asymmetrical short circuit, the end of the resistance vector may be inside the main response characteristic (2). The hodograph of the resistance appears as curve 25. The detuning from this mode is carried out on the basis that the resistance changes very quickly during the short circuit. almost jump. When crossing, the end of the resistance vector of the additional response characteristic (22) at the additional output of block 3 appears to be zero potential and the binary counter 8 goes into operation. As it was written off, it stops when the hodograph crosses the main response curve (21) . If the time 9 during which the end of the resistance vector was between the additional and basic response characteristics is greater than or equal to t & 1, a positive pulse appears at the output of the decoder 14, which translates the state of the logical unit trigger 6, and at the third input of the first element And 9, a positive potential appears, which is a resolving factor for the further operation of the circuit. If time

during which the end of the resistance vector was between the auxiliary and the main response characteristics less than tfe (, for example, external asymmetrical short zazhany, a pulse at the output of the decoder 14 does not appear, the trigger 6 remains in the zero state, on the third

3 input element of the first element: And p / there is a play l9, which excludes the monitoring unit 20, even if the condition k 4 is met

5 go to the state of the logical trigger unit 5 of the logical unit of the main output of the block 3.

Thus, the introduction of a power sensor, a differential amplifier and a setpoint setting unit, an analog-digital converter, a comparator. d2ok1Shsh numbers and their connection as it was indicated allows to increase the speed and selectivity

5 devices.

Claims (1)

Invention Formula Generator protection device against 0 excitation loss, containing a remote measuring unit with main and additional outputs, the inputs of which are connected respectively to the outputs of the current and voltage transformers of the generator stator, while the additional output is connected to the R inputs of the first, second and third triggers, first and second binary counters , and the main output Q to the S input of the first trigger and the first input of the first element I, the output of which is connected to the executive unit, the second input to the forward output of the second trigger, the third input to Пр, the direct output of the third trigger, the S input of which is connected to the output of the decoder via the inputs of the second binary counter connected to the outputs, the input of which is connected to the output of the second element And, the first input of which through the logical element is NOT connected to the additional output of the remote measuring unit, the second input to the inverse output of the first trigger, a. the third input to the output of the stable frequency pulse generator and the first input of the third logic element I, the second input of which is connected to the direct output of the first trigger, and the output to the C input of the first binary counter, characterized in that, in order to increase the selectivity and speed , a power sensor, a differential amplifier, a task unit are additionally introduced into it. setpoints, analog-to-digital converter and binary number comparator, the power sensor is connected to the inputs of current transformers and generator stator voltage, the output to the inverting input of a differential amplifier, the non-inverting input of which is connected to the setpoint setting unit, and the output to the input of analog a digital converter, a binary number comparator is connected to the outputs of the first binary counter by the inputs for the first binary number, the inputs of the second binary number to the outputs of the analog-to-digital the converter, and the output - to the S-input of the second trigger.