SU1462445A1 - Device for protecting against single-phase ground failures - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to relay protection devices. The purpose of the invention is to increase the convenience of operation. When a leak occurs on the earth, at the output of the threshold element 14, a signal is generated that arrives at one of the inputs of the AND 24 circuit. When it appears at the corresponding: counter of the logical distributor 23 The scientific research institute is transformed into a logical 1, which is fed to another input of the AND 24 circuit. Since its first input is;

Description

one

This invention relates to devices for centralized indication or protection against single-phase earth faults in networks with insulated and compensated neutral,

The aim of the invention is to improve the usability.

Figure 1 shows the functional diagram of the device; figure 2 - current transformer zero sequence; FIG. 3 is a circuit diagram of a voltage converter;

The proposed device for protection against single-phase earth faults contains the number of connections. zero current transformers 1, each of which contains in its window a pipe 2 made of a ferromagnet, provided with a continuous short-circuited coil of highly electrically conductive material, such as copper, enclosing the pipe 2, through which the phase conductors A, B, C, erection are passed primary winding. Each trans4) ormator 1 has two secondary windings 3, 4 with an equal number of turns (FIG. 2). The output of each transformer 1 is functionally connected to a current-to-voltage converter 5 (Fig. 3), which contains a measuring resistor 6, capacitors 7, and 8, resistors 9 and 10, a negative feedback resistor P, and resistor 6 is the output of converter 5i, its first output is connected to the common bus, and the second is connected to the first output of the secondary winding 4 and through the resistor 9 to the non-inverting input of the operational amplifier 12, parallel to the same winding

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4 connects a capacitor 8 and a resistor 10. The first output of the secondary winding 3 is connected to the common bus, and its second output through the capacitor 7 is connected to the inverting input of the operational amplifier 12, the output of which is connected to the input of the push-pull emitter repeater 13, and the output of the repeater 13 is connected the second winding pin: 4 and through the negative feedback resistor 11 - with the inverting input of the operational amplifier 12. The output of the converter 5 of each connection is connected to the input of its threshold element 14, the output of which is It is connected with the signal generation unit of the damage, which, in its turn, is connected to the control unit by a communication link. The communication line is made up of the trunk of the two conductors 15 and 1.6, each of the N electrical connections has its own number, and their blocks of forming the damage signal are connected to the communication line parallel to each other. The control unit consists of a generator 17 clock pulses, and its output is connected via a normally open key 18 to the conductor 13 of the communication line and to the counting input of the N + 1 bit distributor 19 pulses, the N + 1 pin of which is connected to the control input of the key 18,. and the remaining N pins are with the synchronization inputs of D-flip-flops 20, the outputs of each of which are connected through an amplifier 21 to their actuator 22, such as an incandescent lamp. The unit for forming the signal of damage of each connection is made in the form of an N-bit counter- distributor 23, the output of which is connected to

one of the inputs of the AND 24 circuit with an open collector, the second input of the circuit 24 is connected to the output of the threshold element 14, and its output to the wiring g 16 of the communication line connected to the information inputs of the D-flip-flops | 20 control unit, the conductor of 15 clock pulses of the communication line is connected in each block of forming the damage signal with the counting input of the distributor 23, with the input of the time maker 25 time intervals and with one of the inputs of the other circuit I 26, the second input of which 15 is connected to the output of the imaging unit 25 time intervals in, and the output - to the input Reset counter-distributor 23.

The distributor 19 pulses of the control unit 20 and the counter-distributor .- 23 of the damage signal generation unit consist of a counter and a decoder.

The key 18 is a 2I-NOT logic circuit, one input of which is connected to the generator 17 clock pulses, and the second to the N + 1 pin of the distributor 19. The driver 25 time intervals of the damage signal generator block 30 consists of connected inverters, one-shot a and a differentiating chain. In the proposed scheme, the control unit for the length of, will reduce: 35 - ni. element base and higher reliability and selectivity used the principle of recording from the information input of each of the D-flip-flops 20

l 19 and in the conductor 15 of the communication line, since the inputs of the key 18 (scheme 2I-NOT). there are two 1, and the output is O, which corresponds to the open state of the key 18, and at the output of the key 18, the sequence of pulses goes in the inverted form de. A sequence of pulses from the conductor 15 of the communication line is fed to the counting inputs of the distributor counters 23 of each connection, where 1 pulses are counted during the transition from 1 to O, and on the outputs of the decoders, the counting signals appear sequentially O. In the absence of a ground fault from the output of the AND 24 circuit with an open collector of each connection, state 16 constantly informs the information inputs of all D-flip-flops 20 even when the previous pulse transitions from the decoder At the control unit 19, the zero-to-one control unit per clock input, state 1 at the non-inverting output of each D-flip-flop 20, while the inverting outputs are always O-flip-flop 20, there will always be an O state. Therefore , in the absence of a closure, the control signal from each D flip-flop 20 to the actuators 22 is missing,

To ensure that each distributor 23 is reset to its original state, at the end of the count, equal to the number of connections, on r - ° hl: r-: yr

the current pulse from the decoder decoder 19 translation of the O. one . For To ensure this, a zero bit is enabled in the decoder of the distributor 19 pulses, while this bit is not activated in the counter of the distributor 23.

l 25 through the inverter is fed a sequence of pulses from the conductor 15 of the communication line and the back edge of each pulse the single vibrator is transferred to an unstable state with

1 at the output to the state O. The start time of the one-shot is chosen not less than 75% of the sum of the duration and the period of the following clock pulses. As a result, a sequence of short pulses with a high voltage level is supplied from the output of the differentiating chain of generator 25 to one of the inputs of circuit 26 and, at the same time, there is also a high voltage level at the other input of circuit 26 circuitry and 26 is formed by 1 and reset the score

The proposed device for protection against single-phase earth faults works in the following way.

If there is no leakage to the ground in any of the connections due to ze: damage to the insulation, the generator 17, so the clock pulses form at its output a sequence of pulses with a fineness of one. The sequence of these pulses is applied to the counting input.

g y 15 20 - 25 30 35 -

l 19 and in the conductor 15 of the communication line, since the inputs of the key 18 (scheme 2I-NOT). there are two 1, and the output is O, which corresponds to the open state of the key 18, and at the output of the key 18, the sequence of pulses goes in the inverted form de. A sequence of pulses from the conductor 15 of the communication line is fed to the counting inputs of the distributor counters 23 of each connection, where 1 pulses are counted during the transition from 1 to O, and on the outputs of the decoders, the counting signals appear sequentially O. In the absence of a ground fault from the output of the AND 24 circuit with an open collector of each connection, state 16 constantly informs the information inputs of all D-flip-flops 20 even when the previous pulse transitions from the decoder At the control unit 19, the zero-to-one control unit per clock input, state 1 at the non-inverting output of each D-flip-flop 20, while the inverting outputs are always O-flip-flop 20, there will always be an O state. Therefore , in the absence of a closure, the control signal from each D flip-flop 20 to the actuators 22 is missing,

To ensure that each distributor 23 is reset to its original state, at the end of the counting, equal to the number of connections, to the “g- ° hl: g-: yy g

 g- ° hl: g-: yy g

L 25 through the inverter is fed a sequence of pulses from the conductor 15 of the communication line and the back edge of each pulse of the one-vibrator is transferred to an unstable state with

1 at the output to the state O. The start time of the one-shot is chosen not less than 75% of the sum of the duration and the period of the following clock pulses. As a result, a sequence of short pulses with a high voltage level is supplied from the output of the differentiating chain of generator 25 to one of the inputs of circuit 26 and, at the same time, there is also a high voltage level at the other input of circuit 26 The circuits AND 26 are generated 1 and the distribution counter 23 is not reset during the counting period. At the end of the counting equal to N connections, N + 1 impulse of the distributor 19 of the control unit to one of the inputs of the switch 18 is applied the level O, and the switch 18 switches to the closed state, corresponding to the level 1 to the output- which lasts a time equal to the sum of the long periods of two periods of a clock pulse. This elongated pulse is fed through the inverter to the starting input of the one-shot driver 25,

Depending on the geometrical dimensions and magnetic properties of the material of the cores of transformers 1, the current of their primary winding is balanced by a compensating current flowing in the secondary winding 4, the difference of these currents induces a mismatch emf in the secondary winding 3, which is amplified by an operational amplifier 12, a two-stroke emitter follower 13 and creates a compensation current in the secondary winding 4. Therefore, the change in current in

which is consumed for the duration of the 15 primary winding, raises the proportions of this pulse. Since during this restart time the one-shot doesn’t occur, level O is fed to the input of circuit 26, while level-1 is fed to its other input. Level.On the output of circuit AND 26, the distributor 23 is reset to its initial state N + l pulse-from the distributor decoder 19. The same pulse returns to the initial state and distributor 19. Then the counting of pulses is repeated, as is indicated by the processes indicated in the device.

An international change in the current in the secondary winding 4. The current flowing through the secondary winding 4 and the measuring resistor 6 causes a drop on it

20 voltage proportional to the current in the primary winding and coinciding with it in phase. Thus, the conversion accuracy is ensured precisely by the fact that the output voltage is removed from the measuring resistor 6. When large currents pass through the primary winding, the required value of the compensation current in the secondary winding 4 is provided by a push pull

With the appearance of an electric emitter follower 13. connection, for example, an emitter, a leakage. Monitoring the health of a transformer-to-earth point zero sequence 1 is achieved as follows.

In the transformer core, a magnetic flux is created and, accordingly, the EMF in the secondary windings 3 and A is proportional to this current, since the total current flowing through the phase conductors of the network in the short coil of copper pipe 2 passes through-Z. The shorter circuit of the magnetic circuit does not include non-balances due to asymmetry of the phase conductors. The reduction in the errors of transformer 1 is achieved by the fact that the short-circuited turn of copper ensures demagnetization of the ferromagnetic pipe 2, maintaining its high magnetic permeability (preventing penetration) and shielding properties. The pipe 2 shields the core from the fields caused by the asymmetry of the arrangement of the phase conductors of the network relative to the central axis of symmetry of the core and the uneven placement of the turns of the secondary windings 3 and 4 around the perimeter of the core.

To ensure that the signal formation blocks are damaged outside

An international change in the current in the secondary winding 4. The current flowing through the secondary winding 4 and the measuring resistor 6 causes a drop on it

voltage proportional to the current in the primary winding and coinciding with it in phase. Thus, the conversion accuracy is ensured precisely by the fact that the output voltage is removed from the measuring resistor 6. When large currents pass through the primary winding, the required amount of compensation current in the secondary winding 4 is provided by a push pull

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When any of the windings of transformer 1 is broken or short-circuited, negative AC feedback formed by secondary windings 3 and 4 is disturbed, resulting in a positive feedback loop formed by capacitor 8 and resistors 9, IO, which is sufficient for self-excitation of operational amplifier 12 In this case, the converter 5 begins to operate as a generator of high-frequency oscillations. The appearance at the output of the converter 5 high-frequency signal indicates damage to the transformer 1,

When a single-phase ground-to-ground connection appears, the voltage from the measuring resistor 6 of the converter 5 is fed to the input of the threshold element 14, and when the voltage of the specified value is offset from the natural leakage current), the output of the 14 V element produces a signal ( I). arriving at one of the inputs of the circuit And 24 with an open collector. Taking into account the specific

7

The implementation of the signal generation unit of the damage circuit And the 24 s open collector consists of an inverter and an NAND circuit. When appearing on the meter terminal of the distributor counter 23, the latter is converted by the inverter into 1, which is fed to another input of the NAND circuit. Since at its first input there is 1 from element 14, at the output of the And 24 circuit, an O is generated, which is fed through the conductor 16 of the communication line to the D-inputs of all the flip-flops 20. This will be recorded at the non-inverting output of the fifth D-flip-flop only 20, since at the moment of the fifth counting the recording from the trailing edge of the preceding pulse arriving at the synchronization input from the distributor 9 of the distributor 9, the remaining D-flip-flops 20 do not record information from the D-inputs, because at this moment in time inputs missing sync pulses from the decoder 19 of the distributor.

Thus, at the non-inverting output of the fifth D-flip-flop 20, O is recorded, and at its inverting output, which is connected to its executive body 22 via the amplifier 21, 1. In this case, the fifth-flashing actuator 22 is activated, which is signal to control the isolation of the fifth addition. The actuator 22 may be an incandescent lamp (indication), a switch excitation winding (deviation

connection) and the control unit pr .. Reset distribution counters.

Claims (1)

water pump (fire extinguishing). In the emergency mode, the reset of the distributor 23 and the distributor 19 to the initial state is carried out in the same way as described above. Formula of the Invention A device for protection against single-phase short circuits to earth, containing 40 45 the outputs of which are connected to the first input of the second elements And, the second inputs of which are connected to the output of the threshold elements, and the outputs of which are connected to the first conductor of the communication line, the input of the threshold elements is connected to the output of the current-voltage converters. 0 five 445 eight according to the number N of connections, the transformers of the zero-sequence current with current-voltage converters connected at their outputs, the first elements AND, amplifiers and executive elements common to all connections are the serially connected clock and shunt generator and the key, pulse distributor, that, in order to increase the convenience of operation, the distribution counters, the second, were introduced into the Negro by the number N of connections; AND elements, time interval formers, D-triggers, threshold elements, as well as a trunk line, are made on two conductors, the output of the clock generator is connected to the counting input of the pulse distributor, the N + 1th output of which is connected to the control the key input, and the remaining outputs - with the synchronization inputs of the D-flip-flops of the respective connections, the information inputs of the D-flip-flops are connected to the first conductor of the communication line, the outputs of each of which are connected via the corresponding amplifiers Spruce to the executive bodies, the second conductor of the communication line is connected to the counting input of the distributor counters, to the input of the time interval formers and the first input of the first And elements, whose 1 second inputs are connected to the outputs of the corresponding time interval Formers, the output of the first And elements connected to the inputs 0 five 0 .. Reset the distribution counters. 40 45 the outputs of which are connected to the first input of the second elements And, the second inputs of which are connected to the output of the threshold elements, and the outputs of which are connected to the first conductor of the communication line, the input of the threshold elements connected to the output of the current-voltage converters. Layer of u 7 HI10 -t-in Fi.Z Output