RU2638299C2 - Device for protection of windings of one-phase transformer from damages - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: device for protection of windings of one-phase transformer from damages contains a measuring converter in the form of an inductance coil, which is installed at equal distance from each of the transformer core rods, so that its longitudinal axis is parallel to the rods of this core, and a responsive body. Optionally the damage display unit is introduced, and the responsive body has two threshold elements, the first of which during the turn-to-turn short circuit generates a cutoff signal, and the second threshold element with a time delay of the signal generates a winding offset signal. At the same time, signals from the threshold elements are sent to the indication unit, which informs the personnel about the nature of the damage of the transformer windings. The use of the device allows to reduce the damage due to the timely disconnection of the transformer from the network in the event of turn-to-turn short circuits and displacement of winding turns, that lead to the occurrence of a turn-to-turn short circuits.

EFFECT: expansion of the functional capabilities of the protection due to the possibility of preventing the occurrence of turn-to-turn short circuits due to the destruction of insulation under the influence of vibration in the place of contact of the displaced turns.

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Description

The invention relates to the electric power industry and is intended for the relay protection of a single-phase transformer against windings and windings displacement.

Closest to the proposed technical solution is a device for protecting the windings of a single-phase transformer from damage, containing a measuring transducer in the form of an inductor, which is placed at an equal distance from each of the rods of the transformer core, so that its longitudinal axis is parallel to the rods of this core, and the reacting organ [ RF patent No. 2549354, publ. 04/27/2015].

However, the reacting organ of this device has only one threshold element with a fixed threshold of operation. That does not allow to identify the displacements of the transformer windings that occur under the influence of electromagnetic forces on the windings at short-circuit currents behind the transformer. As a result, further operation of the transformer quickly enough leads to a short circuit due to the destruction of insulation due to vibration at the point of contact of the shifted turns.

The objective of the invention is to expand the functionality of the protection due to the possibility of preventing the occurrence of a winding due to destruction of the insulation under the influence of vibration at the point of contact of the shifted turns.

The problem is solved due to the fact that an additional fault indication unit has been introduced, and the reacting body has two threshold elements, the first of which, when the circuit is closed, generates a shutdown signal, and the second threshold element with a time delay generates a signal about the offset of the windings, while signals from the threshold elements are fed to the display unit, which informs personnel about the nature of the damage to the transformer windings.

The operation of the device for protecting a single-phase transformer from damage to the windings is based on measuring the difference in the magnetic fluxes of scattering from two absolutely identical windings of a single-phase transformer located on the left and right rods of the transformer core. For this, a measuring transducer in the form of an inductor is placed between them at an equal distance. As a result, in any normal mode of operation of the transformer, the electromotive force induced in it by the magnetic fields of the scattering of these windings will be zero. If, as a result of a short circuit behind the transformer of one of the windings, a displacement of the coils occurs, then an electromotive force will appear in the measuring transducer, which depends on the number and magnitude of the displacement of the closed coils. Due to the fact that after the displacement of the windings of the windings, a short circuit due to friction at the point of contact does not occur immediately, but for some time it becomes possible to reduce the response threshold of the reacting element, and it will be detached from the inrush of the magnetization current or short circuit behind the transformer using Transformer damage signal delay.

Comparison with the prototype shows that the claimed technical solution differs in the number and execution of functional elements. These functional elements are known. However, such their number and performance exhibits new properties in the claimed technical solution, which leads to the expansion of the protection functionality due to the possibility of preventing the occurrence of a short circuit due to the destruction of insulation at the contact point of the transformers displaced during operation.

In FIG. 1 shows a block diagram of a device for protecting a single-phase transformer from damage to the windings, and in FIG. Figure 2 shows the mutual arrangement of the structural elements of the transformer and the measuring transducer, as well as an example of the displacement of the high-voltage winding after a short circuit behind the transformer and the location of the closed turns. In FIG. 3 and FIG. 4 shows the connection diagram of the measuring transducer and threshold elements, as well as the contact implementation of the reacting organ and the display unit.

The measuring transducer 1 in the form of an inductor is located at an equal distance from the same windings 2 and 3 located on different rods of the core of the transformer 4. Thus, if the transformer is not damaged, the same currents will flow through the same number of turns in the windings 2 and 3, and the electromotive force E _un induced in the measuring transducer 1 will be equal to zero. But due to the inaccurate manufacture of windings 2 and 3, as well as the inaccurate installation of the measuring transducer E _{un, it} will be equal to the electromotive force of unbalance E _{un, nb} , which in arbitrary mode is proportional to the currents in windings 2 and 3. It should be added that closed 5 and shifted turns 6 in the winding 2 of the damaged transformer in FIG. 2 are painted in black and gray, respectively.

The winding of the induction converter 1 is connected to the inputs of the first 7 and second 8 threshold elements, which can be made in the form of relays with windings 9 and 10, as well as contacts 11 and 12. The response threshold of these relays is set using resistors 13 and 14. The response threshold of the first threshold the element is selected so that its relay does not operate from the electromotive force E _{un, pe1} that occurs when the inrush currents of the magnetization occur during the inclusion of the transformer in the network and overcurrents during a three-phase circuit behind the transformer. The threshold of operation of the second threshold element must be such that its relay does not operate from the electromotive force E _{un, pe2} arising in any operating conditions, except for the mode of turning on the transformer in the network and with a three-phase circuit behind the transformer. The signal delay time t _per in block 22 must exceed the time of the transient process that occurs when the transformer is connected to the network and with a three-phase circuit behind the transformer.

The signal from the first 7 threshold element about the presence of closed 5 turns in the winding 2 is generated using an intermediate relay with a winding 15 and contacts 16, 17. Using pin 16, the intermediate relay is held in operation, and using pin 17, a signal is sent to LED 18 display unit 19. The intermediate relay is reset to its initial position using button 20. The current in LED 18 is limited by resistor 21.

The signal from the second 8 threshold element about the presence of displaced turns 6 in the winding 2 is generated using the signal delay unit 22, made in the form of a time relay with a winding 23 and contact 24, as well as an intermediate relay with a winding 25 and contact 26. This intermediate relay is held in the triggered state by the contact 26, and using the contact 27 it sends a signal to the LED 28 of the display unit 19. This intermediate relay is reset to its initial position using the button 29. The current in the LED 28 is limited by the resistor 30.

In an arbitrary operational mode of operation of an undamaged single-phase transformer, the electromotive force of the measuring transducer 1 is less than the electromotive force E _{un, pe1} . Therefore, the first threshold element 7 does not work. Contacts 11 of the relay with winding 9 remain open and the formation of a signal about the presence of closed turns 5 does not occur.

The relay with winding 10 of the second threshold element 8 in these modes is activated only when the inrush magnetization currents or overcurrents with a three-phase circuit behind the transformer. At the same time, its contacts 12 start a time relay with a winding 23 and its contacts 24 closes only after a time t _per . Since the transition process is less than t _per , the contacts 24 of the relay with the winding 23 remain open and the formation of a signal about the presence of a displacement of the turns 6 of it occurs.

When closed _{loops occur} , the electromotive force at the output of the measuring transducer increases sharply and if its value exceeds the threshold E E _{, pe1} , then the relay with winding 9 will trip, its contacts 11 will close. This causes the intermediate relay with winding 15 to trip and the contacts 16 and 17 to close. In this case, the contacts 16 keep the relay activated even after the contacts 11 are disconnected when the transformer is disconnected from the mains, and contact 17 generates a signal to turn off the transformer and into the indication unit 19. LED 18 begins to glow, indicating a “coil short” fault.

When the turns are displaced, for example, in winding 2, the electromotive force at the output of the measuring transducer also increases, and if its value exceeds the threshold E E _{, pe2} , then the relay with winding 10 will operate, its contacts 12 will close and cause the time relay with winding 23 to trip. However, its contacts 24 is closed only after time t _per . That makes it possible to rebuild the device for protection against operation in the mode of turning on the transformer in the network. The closure of the contacts 24 causes the intermediate relay with the winding 25 to close and the contacts 26 and 27 are closed. At the same time, the contacts 26 keeps the relay activated even after the contacts 24 are opened when the transformer is disconnected from the mains, and the contact 27 includes, for example, an audio signal and a signal for the unit Indications 19. LED 28 lights up, indicating a “coil displacement” damage.

The technical and economic efficiency of the present invention consists in reducing damage due to timely disconnection of the transformer from the network in the event of coil faults and displacements of the coil windings, which lead to the occurrence of coil faults.

Claims (1)

A device for protecting windings of a single-phase transformer from damage, containing a measuring transducer in the form of an inductor, which is placed at an equal distance from each of the rods of the core of the transformer, so that its longitudinal axis is parallel to the rods of this core, and a reacting organ, characterized in that the unit is additionally introduced damage indication, and the reacting organ has two threshold elements, the first of which forms a trip signal when the circuit is closed, and the second threshold electric ment with signal time delay produces a signal on displacement of the windings at the same time the signals from threshold elements are provided to a display which informs personnel of the nature of damage to the transformer windings.

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