RU2680817C1 - Power transformer protection package - Google Patents

Abstract

FIELD: electrical engineering.SUBSTANCE: protection package of the power transformer using the de-shunting of the tripping coils contains matching intermediate transformers with a variable number of turns of the secondary winding, it has two arms of signal processing, respectively, from current transformers on the sides of high and low voltages. Current from the current transformers goes to the intermediate transformers, from where to the rectifier diode blocks, where the negative half-wave is separated therefrom. Then the positive half-waves arrive at the blocks of the operational amplifiers and comparators, at the outputs of which rectangular pulses are obtained, which arrive at the input of the node of the AND-NOT logic element. In the event of a short circuit within the differential protection zone, the impulses from the comparators go non-synchronously, thus, a positive signal is generated at the output of the AND-NOT logic gate, which is registered by the trigger node, which gives the microcontroller the command to immediately de-shunt the tripping electromagnets of the high-voltage switches that are tripped by the symistors. With through short-circuit currents, the overcurrent protection operates, which receives signals from intermediate transformers, and the negative half-wave is also separated. Positive half-waves fall on the blocks of operational amplifiers, where they are compared with the reference voltage, which is the setting of the current protection. If the current exceeds the current setting, then a positive signal is sent to the comparators, and from them to the microcontroller, which will give a signal to turn off the power transformer. To determine the time to shutdown (exposure), the real current is determined through filter-rectifier blocks connected to intermediate transformers, in which the alternating current is rectified, smoothed, and all frequencies apart from the power frequency are separated. Rectified voltage is fed to the input of the analog-digital converter of the microcontroller. Reference voltage is used as an independent time setting.EFFECT: technical result is increased reliability, enhanced functionality of the protection package of a power transformer.1 cl, 6 dwg

Description

The invention relates to the field of electrical engineering, in particular to complete relay protection devices for power transformers.

Known relay protection kits for power transformers based on relays, for example, DZT-11 or PCT-15 and using a circuit for unloading disconnecting coils using an intermediate relay of the RP 340 series [1].

However, such a set of relay protection [1] has a number of disadvantages, for example, when using electromagnetic type relays, which are triggered by phased transfer of a pulse from one relay to another to the disconnecting coil of switching equipment, which leads to an increase in the error of operation at each stage. The standard for unloading serial relays is limited to a maximum of 150 A. At currents higher, the tripping currents are being reviewed, the operating time is increased, and the protection is roughened. The next of the main disadvantages is the complexity of the mechanical parts, which leads to a decrease in reliability.

Known power transformer protection kits using electronic proximity chips of the microprocessor relay protection BMRZ [2], which are made on the basis of semiconductor elements and do not have moving parts.

The disadvantage of [2] is that the power transformer protection kits using electronic BMRZ contactless microcircuits do not contain elements for dismounting the disconnecting coils of the switching equipment, that is, they do not allow the use of short-circuit electrical energy to enable switching equipment to be switched off.

The closest to the essence of the claimed invention is a device for monitoring the state of insulation of the winding of electrical equipment [3], containing the first and second parametric converters, connected to the corresponding control objects by the input, the output of the first parametric converter is connected through a series-connected first voltage divider, the first resonant amplifier, the first pulse shaper, the first pulse shaper with the first input of the AND element, the output of the second parameter of the converter is connected through a second voltage divider, a second resonant amplifier, a second pulse shaper with a second input of the And element, the output of which is connected to the control input of the key element, the input of which is connected to the output of the differential-amplified block, the first input of which is connected to the first rectifier with a filter, a second rectifier with a filter, a clock counter, an executive unit, where, in order to increase the reliability of control, s inductance, third parametric converter, third voltage divider, first and second tunable filters, clock generator, sawtooth voltage generator, controlled voltage divider, digital-to-analog converter, converter of a sequence of clock pulses into an analog-to-digital converter code, switch, display unit, comparator, the reference voltage unit, while the input of the third parametric converter is connected to the terminal for connecting the neutral of the control object I and through inductance with the common bus of the device, and the output through the third voltage divider connected in series, the second tunable filter connected to the output of the first rectifier with the filter, the output of the first voltage divider connected through the first tuned filter, the second rectifier with the filter, controlled voltage divider with the second input of the differential amplifier block, the output of the clock generator is connected through a converter of the sequence of clock pulses with the control input of the switch and the input of the digital-to-analog converter, the output of which is connected to the control input of the controlled voltage divider, the control inputs of the first and second tunable filters are connected to the output of the sawtooth generator, the input of which is connected to the output of the clock counter, the input of which is connected to the output of the clock , the output of the key element is connected to the first input of the comparator and the input of the analog-to-digital converter, the output of which is connected to the input switch, whose output is connected to the input of the indication unit, the reference voltage output unit is connected to the second input of the comparator, whose output is connected to an input of the execution unit.

The disadvantage of [3] is the impossibility of detecting emergencies on a power transformer and taking measures to eliminate them or reduce harm.

The aim of the invention is to increase reliability, expand the functionality of the power transformer protection kit.

The goal is achieved in that the protection kit for the power transformer using disconnecting trip coils, containing matching intermediate transformers with a variable number of turns of the secondary winding, has two signal processing arms, respectively, from current transformers on the high and low voltage sides. The current from the current transformers goes to the intermediate transformers, from where to the rectifier diode blocks, where the negative half-wave is separated from them. Then the positive half-waves arrive at the blocks of operational amplifiers and comparators, at the outputs of which rectangular pulses are obtained, which are fed to the input of the AND-NOT logical element node. In the event of a short circuit within the differential protection zone, the pulses from the comparator blocks do not synchronously, thereby generating a positive signal at the output of the AND-NOT logic block, which is detected by the trigger unit, which instructs the microcontroller to immediately unscrew the disconnecting electromagnets of the high voltage switches, which shunted by triacs. With through short-circuit currents, the maximum current protection is activated, which receives signals from intermediate transformers, the negative half-wave is also separated. Positive half-waves fall on the blocks of operational amplifiers, where they are compared with the reference voltage - which is the current protection setting. If the current exceeds the set current, then a positive signal is sent to the comparators, and from them to the microcontroller, which will signal to turn off the power transformer. To determine the time to shutdown (exposure), the real current is determined through rectifier filter units connected to intermediate transformers in which the alternating current is rectified, smoothed, all frequencies except the industrial frequency are separated. The rectified voltage is fed to the input of the analog-to-digital converter of the microcontroller. As well as a reference voltage, which is used as an independent time setting.

The essence of the claimed invention is illustrated: FIG. 1 - Functional diagram of the transformer protection kit; FIG. 2 - Explanatory diagram and direction of currents in normal operation; FIG. 3 - An explanatory diagram and the direction of the currents in the action mode of differential protection; FIG. 4 - An explanatory diagram and the direction of the currents in the maximum current protection mode; FIG. 5 - Timing diagram of the circuit in normal mode; FIG. 6 - Timing diagram of the operation of the circuit in the action mode of differential protection.

Where: T - protected transformer; 1Q, 2Q - the first and second high-voltage switches; 1TA, 2TA - the first and second current transformers; 1EO, 2EO - the first and second disconnecting electromagnets of drives of high-voltage circuit breakers 1Q, 2Q; 1, 2, 3, 4 - triacs controlling shunting and bypass disconnecting electromagnets 1EO, 2EO; 5, 6 - intermediate transformers with a variable number of turns of the secondary winding; 7, 24, 25, 28 — a block with Schottky diodes and an output signal limiter; 8, 26 - blocks of operational amplifiers for differential protection; 9, 27 — comparator blocks for differential protection operation; 10, 20 - filter rectifier blocks of maximum current protection; 11, 21 - reference voltage source (setting for maximum current protection); 12 - node of the logic element "AND-NOT" for comparison in time of currents from current transformers 1TA and 2TA; 13 - trigger unit for determining the operation of differential protection; 14 - microcontroller to control the protection kit; 15 - triac control system (driver); 16 - protection operation alarm; 17 is a reference voltage source for a temporary setting of the maximum current protection; 18, 22 - blocks of operational amplifiers for maximum current protection; 19, 23 - comparator blocks for maximum current protection.

I1, I2 - currents from the first and second current transformers 1TA, 2TA, respectively.

"A" is the signal at the output of the comparator unit 9;

"B" is the signal at the output of the comparator unit 27;

"In" - the signal at the output of the node of the logical element "AND NOT" 12.

The principle of operation of the claimed invention.

Normal mode In the absence of short circuits and normal currents flowing (Fig. 2), currents from current transformers 1TA and 2TA are supplied to the right and left shoulders of the transformer protection circuit.

Let us consider separately the paths of differential and maximum current protection:

Differential protection:

The currents from the winding of the intermediate transformer 5 and 6 fall on the rectifier blocks 7 and 25, the positive half-wave falls on the blocks of operational amplifiers 8 and 26, where they are amplified and then go to the inputs of the comparators 9 and 27. The square-shaped signals received at the outputs 9 and 27, in time corresponding to the positive half-waves, are fed to the input of the AND-NOT logical element block 12. Since the currents from the current transformers 1TA and 2TA are normally directed in the same direction, the rectangular pulses will go synchronously (Fig. 5 “A” and “b”). Accordingly, the output of the block of the logical element "AND" NOT 12 will be a logical "0". That is, the presence of a logical “0” will not trigger trigger 13, which means that there will also be a logical “0” at its output. Since at the output of the trigger unit 13 there will be no signal to turn on the differential protection (Fig. 5 “c”), the microcontroller 14 will not give a command to unmount the trip coils, trip coils 1EO 2EO will remain de-energized in this mode and, as a result, high-voltage switches will remain included.

Overcurrent Protection:

In this mode (Fig. 4), the currents from the second windings of the intermediate transformers 5 and 6 are fed to rectifier blocks with diodes 24 and 28, from where the positive half-waves are fed to the inputs of the blocks of operational amplifiers 18 and 22. In operational amplifiers, the incoming signals are compared with the reference voltage the preset maximum current protection from the voltage reference 11 and 21. Since in normal mode the currents passing through the protected transformer T, and, accordingly, the currents from current transformers 1TA and 2TA are less than avka overcurrent, the output of the operational amplifiers 18 and blocks 22 and for the following two blocks of comparators 19 and 23 will be out signal, i.e. a logical "0". Accordingly, the absence of signals about the excess of the maximum current from the comparator units 19 and 23 will not allow the command to unscrew the disconnecting coils by the microcontroller 14. The switching equipment of the high-voltage switches 1Q, 2Q will not be disconnected.

The mode of operation of differential protection. If a short circuit occurs at the point of differential protection between the current transformers 1TA and 2TA (figure 3), the currents change direction to the opposite direction, that is, the place of the short circuit receives power from both the high voltage side and the low voltage side. The incoming, while the secondary currents from the current transformers 1TA and 2TA are supplied to the left and right shoulders of the transformer protection device.

Differential protection:

As in normal mode, the currents from the winding of the intermediate transformer fall on the rectifier blocks 7 and 25, the positive half-wave falls on the blocks of operational amplifiers 8 and 26, where it is amplified and gets on the inputs of the comparator blocks 9 and 27. The resulting square-shaped signals in time corresponding to the positive half-waves, are fed to the input of the AND-NOT logic element 12. Since in this mode the currents from current transformers 1TA and 2TA will have different directions, the resulting rectangular pulses will go not syn chronically (Fig. 6 "a", "b"). Accordingly, nonsynchronous signals supplied to the input of the node of the logical element "AND NOT" 12, in this mode, will cause the appearance of a logical "1" at its output (Fig. 6 "c"). The presence of a logical “1” at the input of the trigger unit 13 will cause its output to switch from low to high, thereby outputting the microcontroller 14 will signal to the control system of the triacs 15 to immediately turn off the switching devices 1Q and 2Q: first, the triacs 2, 4, and then, with some delay, the triacs 1, 3 will close.

Overcurrent protection in this mode will not matter if differential protection is activated.

The operating mode of the maximum current protection. When a short circuit occurs at a point outside the differential protection, that is, outside the zone between current transformers 1TA and 2TA

The currents from the second windings of the intermediate transformers 5 and 6 are fed to rectifier blocks 24 and 28, from where the positive half-waves are fed to the inputs of the blocks of operational amplifiers 18 and 22. In operational amplifiers, the incoming signals are compared with the reference voltage of the specified maximum current protection setting 11 and 21 from sources reference voltage 11 and 21. Since in this mode the currents passing through the protected transformer T, and accordingly the currents from current transformers 1TA and 2TA, are greater than the maximum current setting shields, then at the output of the blocks of operational amplifiers 18 and 22, as well as beyond them of the next blocks of the comparators 19 and 23, there will be a logical “1”. Once at the inputs BX1 and BX2 of the microcontroller 14, they start a command with driver 15 to unscrew the disconnecting coils 1EO and 2EO (first triacs 2, 4 will open, and then, with some delay, triacs 1, 3 will be closed) taking into account the exposure time from element 17 ( its output is connected to an analog-to-digital converter 3 of the microcontroller 14).

To correct the response time, the value of the real current flowing through the transformer is necessary. To this end, signals from intermediate current transformers 5 and 6 are fed to filter rectifiers 10 and 20, where all harmonics are filtered, except for the industrial frequency, rectified and fed to the inputs of analog-to-digital converters ADC1 and ADC2 of the microcontroller 14. The protection is signaled by an audio signal from the unit alarm 16.

Used sources:

1. Relay series RP 340

2. Power transformer protection kits using electronic contactless microchips of the BMRZ microprocessor relay protection unit as part of the relay protection cabinet of station protection SHE1113, NPP EKRA catalog, 2017.

3. SU 1793396 A1 - Patent for the invention "Device for monitoring the state of insulation of the winding of electrical equipment", M.B. Inoyatov, I.M. Beremzhatov, Akhmetshin R.S. 09/10/1990;

Claims (1)

A protection kit for a power transformer with unloading of trip coils, including a trip coil connected in series through a shunt triac to the primary winding of an additional intermediate transformer, and this circuit is closed to the terminals of the protection current transformer, while the shunt triac is connected in parallel with the trip coil circuit with a shunt triac, characterized in that the said circuit from the secondary winding of the current transformer forms the shoulders of the protection kit, for double winding of the power transformer, respectively, forms two protection arms connected to the secondary windings of the mentioned additional intermediate transformer, each of the arms consists of the first and second rectifier units, including filters and zener diodes, respectively connected to the terminals of the first and second secondary windings of the additional intermediate transformer, the conclusions the first and second rectifier blocks are connected to the inputs of the first and second operational amplifiers, and to the second input of the second operation the output amplifier unit is connected to the output of the reference voltage unit, the outputs of the first and second operational amplifiers are connected to the inputs of the first and second comparators, while the output of the first comparator is connected to one of the inputs of the AND-NOT block, and the output of the second comparator is connected to the input of the microcontroller, respectively, the output the “AND-NOT” block is connected to the trigger input, while the voltage driver block is connected by the input to the output of the second secondary winding of the mentioned additional intermediate transformer, and the output is to analog the front-end converter of the microcontroller, and accordingly to the other analog-to-digital converter of the microcontroller, also the reference voltage block of the maximum current protection is connected, the output of the microcontroller is connected to the trigger reset input, and the trigger output is connected to the input of the microcontroller, the signaling unit and the control unit of the aforementioned are connected to the microcontroller outputs triacs.

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