SU412655A1 - DEVICE FOR AUTOMATIC SWITCHING OF RESERVE POWER SUPPLY NETWORKS WITH LOW CURRENT CURRENT TO EARTH - Google Patents

Description

one

The invention relates to the field of automation of electrical installations and power lines, in particular, to devices for automatically switching on backup power supply networks with a low earth fault current (ATS).

AVR devices are known in networks with low ground fault current, which contain equipment that ensures the main power supply is disconnected when this power supply disappears, and equipment that ensures the activation of the backup power supply source.

Such devices provide for switching consumers from the main to the backup power source regardless of the state of isolation of the power grid with respect to ground.

This circumstance in a number of cases leads to the fact that the failure to remove the isolation of a single phase of a three-phase network until the action of AVR transforms into a double circuit to earth at different points due to switching overvoltages arising at the moment of switching sources. If at the same time one of the ground fault points is located in the circuit that receives power from the backup source, then it is likely that the interrupt will be turned off and completely de-energized the consumers.

The proposed device is characterized in that in order to reduce the likelihood of a closure to ground at one point in a two-phase earth fault at different points and prevent switching off the backup power source, an ABP action blocking element is added to the zero-voltage relay connected to the backup source. and on the zero-sequence current relay connected at the input of the main power supply, the contacts of which are connected in series with the intermediate relay coil a deceleration dropout, contacts of which are included in the circuit breaker incorporating a backup power.

This achieves that the disconnection of the main power source and the activation of the backup power source occurs only if there is no ground fault at any point of the backup power network and in the network sections, the power of which is reserved for it.

The drawing schematically shows the proposed device. (Power supply from the main source is indicated by a continuous arrow, and from the backup source - the dotted one).

Starting device of the device AV.R (relay J)

connected to star-connected winding

voltage transformer 2. Closure

relay contacts / indicates the disappearance of the main power supply. Under the condition of normal voltage on the backup source, which is determined by the closed state of the contacts of the voltage relay 3 and closing the contacts of the relay 1, time relay 4 is turned on.

After the installation time has elapsed, the power off switch 5 of the main power supply turns off. The blocking contact 6 of this switch closes the circuit for switching on the switch 7 of the backup power supply.

If there is a zamykan on the ground in the network of the backup power supply, a relay is activated} on April 8, connected to the zero-sequence voltage via a voltage transformer 9 or the corresponding filter filter. Relay 8 opens the time relay circuit 4 and removes the device from operation. A voltage transformer 9 is installed on the backup power section, the circuit 1 of windings of which corresponds to the connection scheme of the windings of the voltage transformer 2.

If the mains supply comes from the main source (when the switch 5 is on) and on the section buses or on the connections extending from these buses, a ground fault occurs, the relay W operates (the indicator of this type of damage, for example, a relay connected to the current transformer zero sequences 11). The closure of the contacts of the relay 10 leads to the triggering of the relay 12 with deceleration and the disappearance of the core after interrupting the current in the coil circuit.

One of the contacts of the relay 12 opens the time relay circuit 4, the ATS is taken out of operation in the same way as when the relay 8 is triggered, i.e. when there is an earth fault in the backup power network.

When the relays 5 and 12 are triggered, in addition to the specified opening of the starting circuit of the ATS, the opening circuit of the switch 7 also opens, which prevents it from automatically turning on regardless of the reason for the switch 5 disconnecting in the main power supply circuit.

Since the interruption of the current in the main power supply circuit even when the remaining ms is closed and the ground leads to de-energization of the winding of the relay 12, to save

In case of blocking action from the indicated relay, the fact of its activation is memorized, which in the considered variant of the circuit is provided by self-holding of relay 12 along the circuit of one of the relay contacts

12 through the relay contact /, and the delay time for the relay to return 12. The delay time for the dropping of the relay cor 12 when the current in the coil is interrupted, this relay must exceed the possible time interval between the moment

the disappearance of the power supply and closing by the contact of the starting organ of the AVR device (relay /).

The specified time interval depends on the nature of the load and the principle of implementation

starting body.

Subject and purpose of and:

A device for automatically switching on the backup power supply of networks with a small current of the closing ground and containing equipment that ensures the disconnection of the main power source when this power supply is removed the ground at one point in the two-phase circuit and the earth at different points and preventing disconnection of the source of reserve power, an organ blocking action AB was additionally introduced P, made on voltage relay and zero sequence, connected to a backup source, and on current relay

and the zero sequence, included in the input of the main power source, the contacts of which are connected in series with the winding of the intermediate relay with deceleration to drop, the contacts of which are included in

backup power switch on circuit.