SU1725314A1 - Device for direct lateral protection of two parallel lines - Google Patents

Abstract

SUMMARY OF THE INVENTION: Performing a unit for detecting the magnitude and direction of a difference in line currents in the form of a three-rod transformer, load and control resistors, diodes, a polarized relay, and a phase-rotation circuit increases the sensitivity of the device. 1 il.

Description

The invention relates to electrical engineering, to devices for selective protection of parallel lines.

The devices for balanced protection of parallel lines are known, which contain elements for controlling the current of each line and devices for their comparison for the selective action of protection in case of short circuits on one of the parallel lines.

Balanced protection does not provide action at substations without a power source, therefore they have limited application.

Also known are devices for directional protection of parallel lines comprising measuring transformers, a relay controlling the magnitude and direction of the current difference with output disconnecting circuits of switches of parallel lines.

Directional transverse protection reveals a damaged line based on a comparison of the direction of the currents in the

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lines regardless of the availability of power sources at the substation.

The disadvantages of this device are the presence of a dead zone from close three-phase short circuits and the need for a significant deeper protection when it is turned on on parallel lines of different lengths.

The closest to the present invention is a device for differential protection of two parallel power lines, containing line current sensors, the outputs of which are connected to the inputs of the unit for detecting the magnitude and direction of the line current difference, and the actuator acting on the switches, taking into account the selected ratio of compared currents through the intermediate elements of their amplification.

Differential protection on hermetic-waves in a magnetic field of phase conductors of parallel lines has a high

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with

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sensitivity and the ability to equalize balanced currents to protect parallel lines of different lengths.

The disadvantage of this device is the lack of the required sensitivity of the protection at the substation without power sources and the need to use amplifiers of the compared line currents, which reduces the reliability of the protection as a whole.

The purpose of the invention is to increase the sensitivity and protection of parallel lines,

The drawing shows a scheme for the inclusion of directional transverse protection of parallel lines.

On parallel lines x 1 and 2, the transformers 3 and k are connected, to which the primary windings 5. and 6 of the three-core transformer 7 are connected, on the extreme rods of which are also installed the secondary windings 8 and 9 with the same number of turns. The secondary winding 10 is installed on the middle rod and connected to the output circuit of the phase-turning circuit 11 from the voltage transformer 12 to the load resistor 13, to which the windings 8 and 9 are connected in series regulating resistor 1A-with separate circuits of differently connected diodes 15 and 16 windings 17 and 18 of a polarized relay, contacts 19 and 20 of which are included in the opening circuit of switches 21 and 22 lines 1 and 2. The number of turns of the primary windings 5 and 6 of transformer 7 is proportional to the resistance of parallel lines 1 and 2, respectively .

The device works as follows.

When the load flows or external short circuits, the currents in parallel lines 1 and 2 are distributed inversely, in proportion to their resistances, and have the same direction in transformers 3 and 4 currents that feed the primary windings 5 and 6 of transformer 7. By choosing the number of turns windings 5 and 6 are proportional to the resistances of lines 1 and 2, their amperages are of the same magnitude even at different lengths or resistances of the lines, therefore the resulting voltage from the secondary windings 8 and 9 have a zero value with the exception of

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the operation of the polarized relay in any direction.

With a short circuit on line 1, the current in its circuit exceeds the amount of current in line 2, in which it flows either in the same direction as in line 1, or in the opposite direction. In both cases, the difference in primary currents is sufficiently large, from which the algebraic sum of the secondary voltages of windings 8 and 9 causes the currents to circulate in the windings 17 or 18 of the polarized relay through diodes 15 or 16 and a common regulating resistor 13, to which also voltage from the phase-shifting circuit: 11 transformer 12 voltage is common-: local with voltage of winding 10 from algebraic sum of magnetic fluxes from currents of windings 5 and 6 when powered from transformers 3 and k current,

The phase shifting circuit 11 has a shift angle equal to the resistance angle of the lines to be protected, so the voltage at its output either coincides with the voltage from the secondary windings of the transformer 7 or is in opposite phase. Since the opposite-polarity windings 1 and 18 of the polarized relay are connected through oppositely directed diodes 15 and 16, therefore, the current passes only through that winding in which the supply voltage from the transformer 7 does not coincide: it gives the reference voltage across the resistor 1 3 from the circuits voltage substation. For the winding with the coincidence of the voltages from the transformer 7 and from the transformer 12, taking into account its shift in the circuit 11 on the load resistor 13, the locking is supported by the reference voltage; diode 15 or 16, so the circuit operates depending on the direction of the current difference with respect to j voltage on the substation buses. Support-; Voltage without voltage from the difference of currents does not trigger the polarized relay due to the same magnitude of currents in its opposite polarity windings 17 and f8.

On condition that the currents exceed the line 1, the contacts 19 of the polarized relay in the trip circuit of the switch 21 are closed; and in the reverse direction of the currents, contacts 20 are closed in the trip circuit of the breaker 22. The adjusting resistor 14

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setting of the desired protection setting is provided; Unloaded from the unbalance current of the load of one of the lines or through the short circuit current with their alignment by the corresponding turns of the primary windings 5 and 6 of the transformer 7.

The secondary winding 10 of the transformer 7 feeds the reference voltage on the load resistor 13 from the sum of the currents of the line 1 and 2, the choice of the direction of the voltage vector from the sum of the currents from the substation towards the line coincides with the secondary voltage vector from the voltage transformer 11 . With a near three-phase short-circuit voltage, the voltage on the transformer is absent, therefore the voltage from the secondary winding 10, caused by the sum of the currents of lines 1 and 2, is used as the reference. In the absence of power sources at the substation, the protection directivity is provided by the total current from the residual voltage of the electric motor connected to the substation. gateli. For high-speed transverse protection, at the first moment of occurrence of a short-circuit, the residual level of the yarn is retained in order to be able to ensure the directionality of the protection even with a close three-phase short circuit at the substation tires. As a result, on the basis of the specified principle of cross-directional protection, it is necessary to ensure high sensitivity of protection for any kind of short-circuit in any place of parallel lines in different modes.

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max their nutrition and even if there is a possible difference in their length.

Claims (1)

Formula of .bethen and A device for directional transverse protection of two parallel lines, containing sensors for current lines, the outputs of which are connected to the inputs of the unit for detecting the magnitude and direction of the difference between the currents of the lines, and an actuator, which, in order to increase the sensitivity, The unit for detecting the magnitude and direction of the difference in the current of the lines is made in the form of a three-core transformer, load and control resistors, diodes, a polarized relay and a phase-turning circuit, with the extreme rods of the three-rod The transformer is arranged with .1 equally directed primary windings, the conclusions of which are the inputs of the unit for detecting the magnitude and direction of the difference in the current of the lines; - the lining resistors to the integrated parallel across the diode connected to the windings of the polarized relay, parallel to the load resistor through the winding located on the middle rod, connected to the outputs of the phase rotation circuit, the input of which is intended for connection to the voltage transformer of the supply busbars. /