SU1494095A1 - Current protection device for three-phase electrical installation - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to relay protection, and can be used to remotely control the current of high-voltage power lines and protect these lines from phase-to-phase short circuits. The purpose of the invention is to increase reliability by simplifying the device. This is achieved by introducing between analog-to-discrete converters 4-6 and communication channel 7 of a signal switch 9, including D-triggers 11-13, an OR 14 element and a pulse distributor for three positions 10. 5 Il.

Description

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The invention relates to electrical engineering, in particular, to relay protection, and can be used for remote control of high-current power transmission lines and protection of these lines against phase-to-phase short circuits.

The purpose of the invention 1) is reliability by simplifying the device.

FIG. 1 shows a functional diagram of a device for current protection of an electrical installation in FIG. 2-A; time}; 1, diagrams at the outputs of the section 1) of the blocks and elements J in FIG. 5 an example of the implementation of the device.

The device for current protection 1 s three-phase electrical installation consists of measuring transducers 1-3, anti-discrete npeoOpasoi ;; - telephones 4-6, communication channel 7, output relay relay 8 and switching of 9 signals, made in the D form - 10 pulse distributor to three positions, D-flip-flops 11-13, the OR 1 element (.

Each of the analog-to-digital converters 4-6 may be jii-. more fully, for example, in the form of a polar indicator 15 with a USB 16 and a multivibrator 17, an integrator 18, a time-pulse converter 19 with a 20 cp block, a 21 reference voltage block, and 22 intervals, the element OR 24 and - (riggor 25.

The distributor 10 pulses on three positions can be made in the form of a binary-decimal counter 26 (for example, a counter type K15IE2) and inverter 27. At the same time, both counting inputs of counter 26 are combined and connected to the output of the element OR 14, R R-inputs of counter 26 zeroed & Rj inputs are connected to the third output of the binary-decimal counter 26, first 11 the output of the counter 26 is connected via inverter 27 to the D- input of the trigger 11, the second output of the counter 26 is connected to the U input of the trigger 12, and the fourth output of the counter 26 to the B- INC DU trigger 13.

The operation of the device is considered for the case of three-phase current protection, when the duration of a single-pulse phase signal does not exceed 2/3 of the half-period, i.e. 6.66 ms

40954

(Fig. 2), and this duration of the heating system, i.e. more than 6.66 cm (Fig. 3), as well as for the case of two-phase short-circuiting, if the pulses of the phase signals are in antiphase, and their durations exceed 1/2 of the half-period (Fig. 4).

Voltage from the primary outputs

10 transducers 1-3 are integrated into analog-to-discrete transducers 4-6 and converted to discrete single-pulse signals of duration L I, Oj, o j., (Fig. 2a-b,

15 of FIG. In-FIG. 4a, b), which carry information about the complex effective value of the primary current, and the durations vary within the finite limits, so that the current is lower than the lower limit, pa corresponds to the post-duration signal duration T (Fig. 4B). single pulse signal matches the expression

: g t 1n (1/1, „) + TO, (1)

where T is a constant coefficient depending on the parameters of the analog-discrete converter; 30 I - the effective value of the current.

When plotting time diagrams in FIG. 2 ab, fig. 4a, b, it is taken into account that the analog-discrete converter generates an output single-pulse signal of duration C j in such a way that with the help of the generator 22 stable time intervals (Fig. 5) its trailing edge is shifted relative to the transition time 40 through zero; e1I1Y from the output of the measuring transducer to W.adan-} 1st time, for example, 9 ms.

In the absence of a short circuit, i.e. in the normal mode, there are no voltages Uj at the output j, for example, the measuring transducer 1, the pulses of the output of the comparison block 20 do not appear and the initial flips of the 25 5Q flip-flop are performed using signals (with a duration of 8 ms) produced by the driver 23 stable time intervals. The resetting of the trigger 25 to the initial state is made, as before, by signals from the generator of 22 stable time intervals. As a result, in the absence of voltage. the output of the trigger 25, there are signals, the duration of which corresponds to TD (in this case 1 MS, fig.A and)

Further, signals from analog-to-discrete converters 4-6, passed through the signal switch 9, are transmitted in a certain sequence via communication channel 7 to the output relay unit 8.

The distributor 10 pulses into three positions, each of the outputs of which has a single signal level during the absence of two other pulses (Fig. 2-4d, d, e), cyclically count the input pulses to three. Considering that the initial position of the binary-decimal counter 26 is equal to 0000, with the help of an inverter 27, the distributor 10 pulses per three polgeni is in position 100. In this case, the D-flip-flop 11 is prepared for clearing. When the input pulse arrives at the binary-decimal counter 26 it is set to position 1100. Inverter 27 sets the distributor 10 pulses to three positions to position 010. In this case, the D-flip-flop 12 prepares for triggering. The next input pulse of the binary-decimal counter 26 flips it to position 1001. Using the inverter 27, the outputs of the distributor 10 pulses at three positions are set to position 001. At this time, the D-flip-flop 13 triggers.

Thus, depending on the duration of the single-pulse phase signals C y, cjg, ic, the outputs of the flip-flops 11, 12 and 13 appear corresponding signals of the same duration 1 time per period (fig.2j, h, u) or 1 time 4 periods (fig.Zzh, s, and).

For the case of a 2-phase short circuit (Fig. 4g. 3), the signals at the output of the flip-flops appear 1 time in 2 periods. In this case, a pulse with a duration of Tr (Fig. 4i) passes in the missed period, indicating a small value or absence of current in this phase (Fig. Av).

FIG. 2 shows time diagrams of signals in a three-phase mode, when the phase signal duration does not exceed 2/3 of the half period (6.66 ms. In this case, all three phase signals are formed at the output of the element OR 14 over one period

Q p 5

0

five

0

five

0

(Fig. 2k) and the delay of the information is obtained the same as in the case of using for each phase a separate single-phase analog-discrete converter.

If the duration of the phase signals exceeds 2/3 of the half-period (Fig. 3), then the subsequent signal (for example, phase B) enters the communication channel 7 and to the input of the distributor 10 pulses only after 1 and 1/3 of the period after the start of the previous signal ( Phase A, Fig. SC), and the new phase A signal arrives only 4 times after the previous phase A signal. But since in the three-phase mode all three currents are the same, then when evaluating the information lag, the shift between the leading edges of two adjacent signals should be taken into account in channel 7 communication. The shift is I and 1/3 of the period, i.e. somewhat larger than that of a single-phase analog-to-discrete converter. Therefore, it is desirable to use such analog-to-digital converters for which the maximum signal duration does not exceed 6.66 ms. Thus, the principle of temporal compression of signal transmission is implemented in the signal switch.

From the output of the signal switch 9, the pulses pass through the communication channel 7 and arrive at the output relay block 8. The last 8 triggers if the duration of the Ct single phase impulse signals (, Cjj, cj exceeds the preset setpoint and a protection occurs ( 2-4l).

This protection device has a simpler solution, since it has only one communication channel and an output relay unit instead of three for a three-phase system.

Claims (1)

Invention Formula A device for current protection of a three-phase electrical installation, containing measuring transducers, the inputs of which are intended to be connected to the corresponding phases of the protected electrical installation, and the outputs are connected to the inputs of the corresponding analog-discrete transducers, a communication drop, the output of which is connected to the input of the output relay unit, the output of which is the output of the device, which is due to the fact that, in order to increase reliability by simplifying the device, a signal switch is additionally introduced into it, made in the form of three V-triggers of the pulse distributor on three positions of the OR element, while the R and C inputs of each D flip-flop are combined and connected to the output according to The D-input is connected to the corresponding output of the pulse distributor at three positions, the outputs of the D-flip-flops are connected to the inputs of the OR element, whose input is connected to the input of the pulse distributor at three positions and the inputs of the communication channel.