SU650148A1 - Arrangement for overload protection of parallel-connected transformers with voltage regulators under load with aid of circulating current - Google Patents

Description

from the measuring transducers, and two pairs of I logic elements, in which the first inputs of the first pair are connected to the output of one of the specified current relays, the second pair to the output of another current relay, the second input of one of the logic elements And each pair is connected to the first output the mentioned three-position relay, and the second input of the other with the second output of the three-position relay, the outputs of the first pair are connected to the blocking inputs of voltage regulators under the load of transformers, and the outputs of the second pair are connected to the discharge inputs p Rumble torus voltage under load of one of the transformers, the received master. In addition, between the output of the second current relay and the common input of the second pair of logic elements, AND is additionally introduced the logical element OR, to the second input of which one of the outputs of the voltage regulator under load is connected.

The drawing shows a functional diagram of a device for protection against unloading by equalizing current together with control circuits for two devices of two parallel operating three-winding step-down transformers with voltage regulators under load.

The given general case of parallel operation of transformers 1 and 2 to high voltage 3 and medium voltage 4 can allow to use position mismatch both for regulated compensation of the charging power of the power supply line 5 and for providing optimum voltage, for example, consumers 6 and 7, separately operating low voltage windings. The control of the switches of the RII transformers 1 and 2 is carried out through the drive mechanisms, respectively, of the servomotors 8, 9 (shown in dotted lines in the drawing).

The inputs of the servomotor 8 include the outputs of the reversing starters 10, I, and the inputs of the servomotor 9 include the actuators 12 and 13. The reversing starters 10, 11 and 12, 13 are the output elements 14 and 15 of the control circuit of the transformer on-load tap-changers. The output of the equalizing current sensor 16 is connected to the input of a three-position relay 17, which has two outputs, one of which, direct, corresponds to one direction of the equalizing current, and the other, opposite. The balancing current limiter 18 is connected to the measuring transducers 19 and 20 of the load current of the transformers and contains two current relays 21 and 22 and two pairs of logic elements AND 23, 24 and 25, 26. The outputs of the first pair of logic elements AND are connected to the blocking inputs of the on-load tap-changer of both transformers . The figure shows as an example their connection to the logical elements BANKS 27-30. The outputs of the second pair are connected to the discharge inputs of one transformer. The figure shows their connection to the starters 12 and 13. An OR 31 logic element is connected between the output of current relay 22 and the inputs of elements 25 and 26. The second input of the OR 31 logic element is connected to one of the outputs of voltage regulator 32 under load.

The pickup value of the three-position relay 17 is determined by the magnitude of the equalizing current with a minimum mismatch of the positions of the PIN. The setting of the operation of the current relay 21, designed to detune from the auto-oscillations of the on-load tap-changer, corresponds to the load of at least one of the transformers less than the nominal one by equalizing current with the minimum mismatch of the on-load tap-changer. Tripping setting

The second current relay 22 corresponds to the rated load of the transformers.

When regulating the compensation of the charge power of a long power line or ensuring the optimum voltage of consumers by mismatching the transformation ratios after the occurrence of the balancing current, a three-position relay 17 is triggered. However, when transformers 1 and 2 are not fully loaded, the reversing starters 12 or 13 do not act to reduce the balancing current, since there are no signals at the output of elements 25 or 26. With an increase in the load, at least one of the transformers reaches

the operation of the first relay 21, depending on the direction of the surge current, triggers the logic element AND 23 or 24, to the other input of which the corresponding output of the three-position relay is already fed,

and through the elements BANKS 27, 30 or 28, 29 prohibits the on-load tap-changer from adjusting both transformers to increase the surge current in this direction. The regulation to reduce the circulating current is maintained.

When the load reaches at least one transformer of the nominal value, the second relay of limiter 25 is triggered and, depending on the direction of the surge current through AND 25 or 26, turns on one of the reversing starters 13 or 12 of the servo motor 9 of the transformer 2 on-load tap-changer;

When compensating for the charging power of the power line, the on-load tap-changer is controlled from one of the outputs of the voltage regulator 32 under load to reduce compensation. Using a logical element

OR 31, a reduction in the transformation coefficient mismatch is achieved without overshoot to increase it.

The device can be used for parallel operation of transformers with

three and more, one of which

the equalization is accepted by the master, and the rest by the slaves. This control system contains an alignment circuit that is made in the form of a multipath star, each beam of which contains a sensor of reactive current or the position of the transformation ratio generator and an impedance connected in series with it, which is an equalization current sensor.

The protection device of each transformer with RIN contains a three-pointer relay connected to the equalizing current sensor of the corresponding beam of the equalization circuit, two pairs of elements AND, each of which is connected to one of two opposite outputs of the three-relay relay, two elements of the control device RiN.

At the same time, a limiter containing two relays with a common input and controlling the load of all transformers, the first relay through one of the elements of the first pair and the corresponding element 3AiiP T will block the control of all transformers with on-load tap-changer to increase the surge current, and the second relay through one of the elements of the second plank is to allow the effect of three-position relays of slave transformers to reduce the surge current.

Using transformer overload protection devices to regulate the transmission power charge compensation and ensure optimum customer voltage by mismatching the transformation ratios will allow automating the control of transformer load and expanding the use of control tools that reduce notii and reduce the voltage supplied to the equipment, and also to improve the quality of consumer voltage, for substations without personnel on duty.

Claims (2)

1. A device for protection against overloading by equalizing current of two parallel-open transformers with voltage peaks under load, containing an equalizing-current sensor and, connected to its output, a three-pozvtsionny relay, which, in order to expand its functionality, additionally introduced measuring transformer load current transformers and a surge current limiter containing two current relays connected inputs to each of the measuring preoperators, and two pairs of logic elements AND, in which the first inputs of the first pair are connected to the output of one of the current relays, the second pair - to the output of another current relay, the second input of one of the logic elements And each bunk is connected to the first the output of the aforementioned three-room relay, and the second input of the other with the second output of the three-position relay, the outputs of the first pair are connected to the blocking inputs of voltage regulators under the load of transformers, and the outputs of the second pair are connected to load inputs of voltage regulator under load one of the transformers. 2. The device according to claim 1, characterized in that the output of the second current relay and the common input of the second pair of logic elements AND are additionally introduced an logical OR element, to the second input of which one of the outputs of the voltage regulator is connected under load. Sources of information taken into account in the examination 1. US Patent N ° 2968737, cl. 307-51, i960. 2. US patent N ° 2913591, cl. 307-51, 1959.