SU1381654A1 - Automatic switch for a.c.mains - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to devices that switch the responsible consumers of electric power systems (EPS) from the main network to the backup network when the voltage deviates from the set values, and can be used in autonomous EPS (for example, shipboard). The aim of the invention is to improve reliability. The device controls the presence of the voltage of the main and backup networks in the zone of allowable values for a predetermined time, and for the main network there is a difference between the zone of allowable values for slow changes in the EES mode and the zone for rapid changes. The device operates with the priority of the main network in relation to the backup network and connects the consumer to the main network if the voltage is within the specified limits for a specified time. When the voltage of the main network leaves the zone of permissible values for a time longer than the specified one, and if there is voltage within the specified limits of the backup network, the device switches the consumer from the main network to the backup network. The voltage of each phase is monitored by a channel consisting of a voltage transformer, a filter filter and a two-level comparator. Voltage monitoring in the primary and backup networks is carried out by comparators using AND, OR, NOT elements. 1 il. with s (L 00 and SP 4

Description

The invention relates to electrical engineering, in particular, to devices that switch the responsible consumers of electric power systems (EPS) from the main network to the backup network when the voltage deviates from the measured values, and can be used in autonomous EPS, for example, in ships.

The purpose of the invention is to increase reliability.

The drawing shows a functional diagram of an automatic AC switch.

The device consists of six single-phase transformers 1-6, connected respectively to the main and backup networks. The outputs of transformers 1-6 are connected to the inputs of six corresponding full-wave rectifiers 7-12. The outputs of rectifiers 7-9 are connected to the inputs of two-level mains of the main network. The outputs of rectifiers 10-12 are connected to the inputs of the corresponding group of two-level comparators 19-21 of the backup network voltage. The outputs of the latter are connected to the three-input circuit of AND 22. The first 23 and second 2A three-input OR circuits are connected to the outputs of the two-level comparators 13, 15, 17 and 14, 16, 18 voltages, respectively. The outputs of circuits 23 and 24 are connected through relays 25 and

26 time with one of the inputs first

27 and the second 28 And circuits, the second inputs of which are connected via the second time relay 29 to the output of the three input circuit And 22. The outputs of the first circuit And 27 and the second circuit And 28 are connected to the inputs of the third circuit OR 30. The output of the latter is connected to one of the inputs of the executive relay 31, the other input of which is connected via the first time relay 32 and the inverter 33 to the output of the first three-input circuit OR 23. The time relays 25, 26, 29 and 32 have adjustable time settings.

The device works as follows.

The controlled voltage of the main and backup networks is fed to the inputs of single-phase transformers 1–3 and 4–6 voltages, the output voltages of which are fed to rectifiers 7–9 and 10–12. Stampers 7–12 are equipped with a low-frequency filter that provides smoothing of the pulsating voltage. Smoothed voltage from rectifier 7-12 is fed to the inputs of two-level comparators

with a voltage of primary 13-18 and backup 19-21 networks.

In the normal operation of the device, the implanting relay 31 provides through a switching contactor

0 connection of consumers to the main network (priority of the main network). At the same time, the voltage in the main network is within acceptable limits, and at the outputs of two-level commuters

5 13-18 voltage signal is present, corresponding to O. The same signal is also present at the inputs of the three-input circuits OR 23 and 24. Time relay 25 and 26 is not triggered, and the relay

0 32 times triggered by a logical 1 signal from inverter 33.

At the input of the And 27 and 28 circuits and at their outputs there is also a signal corresponding, therefore, to

5, the first input of the executive relay 31. There is no control signal through the third circuit OR 30. The second input of the executive relay 31 receives a signal 1 from the first relay 32

0 time after a specified time lag, confirming the connection of consumers to the main network or changing the state of the switching contactor, ensuring the transfer of consumers from the backup network to the main network, if the latter were connected to the backup network according to the conditions of work in the EPS.

With slow mode changes

- | EES device works as follows.

When the voltage deviates in the main network (either in one of the phases or in three phases), the two-level comparators 13, 15, 17 of the voltage and the signal 1 from their outputs run through the three-input circuit OR 23, starts the time relay 25 and zeroes relay 32 time. At the same time, the executive relay 31 does not change its state until the control signal is received at its first input;

After a predetermined time, if the voltage parameters of the main network 5 do not return to the permissible limits, signal 1 from the output of the time relay 25 arrives at the first input of the circuit 27. 27. A similar signal from the relay 29 comes to its second input

five

five

time, if the backup network voltage parameters in each phase correspond to the permissible. In this case, the two-level comparators 19-21 of the backup network produce a signal 1, inverse with respect to the output signals of the two-level comparators of the main network, and through the three-input circuit And

22 trigger time relay 29. If in one of the phases of the backup network the voltage does not meet the specified limits, then the output of the corresponding voltage comparator is a signal O and the time relay 29 does not start. The time laps of relays 25 and 29 were chosen the same, corresponding to the standard time lag for slow changes in the EPS,

From the output of the circuit AND 27, the signal 1 through the third circuit OR 30 comes to the first input of the executive relay 31, which acts on the switching contactor and switches consumers from the main network to the backup network. When the voltage of the main network is restored, the comparators 13, 15 and 17 change The state of the output to the reverse, which leads to time zeroing of the relay 25 and the start of time relay 32, the time delay of which is set longer than the maximum transient time in the EPS. This eliminates the reverse transfer of load from the backup network to the main at the moments of transient processes in the system.

After the specified time has elapsed, in the absence of a transient in the main network, the second input of the executive relay 31 receives a signal 1, which changes the state of the contactor, which corresponds to switching consumers from the backup network to the main one.

Fast dynamic processes in an EPS (operational and emergency) are characterized by length-like dips and voltage surges, as well as various durations of these processes. Moreover, the voltage deviations in emergency modes can be commensurate with the voltage deviations of both networks for operational modes. Transferring the load from one network to another during operation deteriorates the quality of electricity. To ensure reliable operation of the device and eliminate over

ten

15

25

thirty

-2о 3816544

Switching on consumers in fast dynamic processes, the device analyzes the voltage deviations and their durations in each phase of both networks. Switching of consumers from one network to another occurs only when voltage parameters in networks are acceptable under the operating conditions of the responsible consumers, and only after the end of the dynamic mode in the EPS.

When fast dynamic processes in the EES device operates as follows.

In case of pulsed, intermittent load in operational or emergency modes of EPS operation in the main network, the voltage control is determined by two-level voltage comparator 1A, 16, 18 and the second three-input circuit 1W 24. The voltage deviation in the main network is the setting of any of the specified voltage comparators the start of the time relay 26, the state of the elements AND 28, OR 30 and the executive relay 31, respectively, when the voltage parameters in the backup network, i.e. in the presence of

1 at the second input of the circuit And 28. I

Exposure time relay time 26

tuned to the highest possible time of fast operating mode in an EPS. The settings of the voltage comparators 14, 16, 18 are selected at the level of the maximum permissible voltage deviations in these operating modes of the EPS.

40 If, during the time lag of the time relay 26, the voltage parameters of the OS are returned to the allowable area, then the time relay 26 is zeroed out and the consumers are transferred from the main network to

45 backup does not occur. Reverse transfer of consumers from the backup network to the main network occurs as

slow mode changes

EES.

50

Claims (1)

Invention Formula Automatic AC switch containing three 55 main transformers, three transformer stand-by1CH network, executive relay, first and second time relay, inverter, connected via the first time relay to one From the inputs of the executive relay and the three-input circuit I, characterized in that, in order to increase reliability, it is additionally equipped with six two-wavelength connectors, each of which is connected to one of the transformers, sixth two-level voltage comparator connected in pairs by its own inputs with outputs of connectors connected to transformers of the main network, three two-level voltage comparators connected by their inputs with outputs of rectifiers connected to transformers of a backup network, two rehvhodovymi OR circuits, the first of which is connected to the outputs of the three comparators of two-level voltages of different phases /} VS /} Sun main network, and the second with three other, third and fourth time relays connected to the outputs of the corresponding three-input OR circuits, two two-input AND circuits, the first inputs of which are connected to the outputs of the third and fourth time relays, and a third OR circuit, and the inputs of the latter are connected to the outputs of the two-input circuits I, and its output is connected with another input of the executive relay, the second inputs of the two-input circuits I are connected via a second time relay to output of the three-input circuit And inputs which are connected to the outputs of the three two-level voltage comparator of the backup network, and the input of the inverter is connected to the output of the first three-input circuit OR.