RU2566395C1 - Device for testing high-voltage equipment to short-circuit current resistivity - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: invention is referred to the area of electric engineering, in particular, to devices for electrodynamic test by short-circuit current (K3) of high-voltage power transformers. Essence of the invention: the device comprises bank of capacitors (1) coupled to output of the first voltage converter (4), inductance coil (2) coupled through switch (3) to bank of capacitors (1), booster transformer (5), which secondary winding is connected between output of coil (2) and output of the device intended for connection of the tested equipment. Primary winding of transformer (5) is coupled to output of the second voltage converter (6), which data input is coupled to sensors (7) of output current and output voltage. Converter (6) is designed to generate at secondary winding of the booster transformer of voltage compensating active losses of the installation and tested equipment in compliance with vector expression:

, where $${\overline{e}}_k$$

is compensating voltage; U₀ is rated test voltage; U_n is current value of output voltage; $${\overline{i}}_n$$

is output current; k_u, k_i are control factors of converter (6) for voltage and current respectively.

EFFECT: improved stability of test voltage and reduced power requirements.

2 cl, 4 dwg

Description

Technical field

The invention relates to the field of electric power and, in particular, to devices for electrodynamic testing by short-circuit currents (SC) of high-voltage power transformers of high power (more than 80 MVA), reactors, circuit breakers, and other high-voltage electrical equipment. The objective of such tests conducted at specialized test benches is to determine the electromechanical resistance of equipment in sudden short circuit modes in order to improve its technical characteristics and design solutions.

State of the art

Electrodynamic tests are carried out in accordance with current standards. For example, tests of power transformers are carried out in accordance with [GOST 20243-74. Power transformers. Test methods for short circuit resistance], which regulates the rated level of short-circuit shock current depending on the rated power of the transformer and the normalized duration (0.2 s) of the test short-circuit.

The power that is briefly consumed from the network during short-circuit resistance tests depends on the rated power of the transformer under test and exceeds it by a factor of ten. So, for example, for testing a transformer of the type ТДЦ 250000/220 with a capacity of 250 MVA and a rated voltage of 220 kV in accordance with the requirements of GOST, the power of the power system is ≈ 15600 MVA.

Providing this power is the main problem in electrodynamic testing of high power transformers for short-circuit resistance. At the same time, the problem is not only the generation of the required power by the power system, but also the adaptation of the power system, its generating and other electrical equipment to impulse disturbances arising from a series of such tests.

Known devices for electrodynamic testing of power transformers powered by autonomous sources of three-phase current [SU 1394172, SU 1608595] and powered by a power system [RU 2041472, RU 2505600].

Known devices do not allow electrodynamic tests of high-power power transformers (more than 80 MVA), since during such tests the load surges on the power system can reach several thousand MVA.

The use of an oscillatory LC circuit to obtain a test voltage of the industrial frequency of the oscillating circuit with preliminary energy storage in it does not make it possible to ensure the stability of the test voltage required by GOST for a given short circuit time (0.2 s) due to damping of oscillations due to active losses in the oscillatory circuit and equipment under test (e.g. transformer).

Disclosure of invention

The technical result of the invention is to increase the stability of the test voltage and reduce the required power supply.

The subject of the invention is a device for testing high-voltage electrical equipment for resistance to short circuit currents, comprising a capacitor bank connected to the output of the first voltage converter, an inductor connected via a switch to a storage capacitor, a voltage boost transformer whose secondary winding is connected between the output of the inductor and the output of the device designed to connect the equipment under test, and the primary winding is connected to the output one of the second voltage converter, the information input of which is connected to the sensors of the output current and output voltage of the device, while the second voltage converter is configured to form a voltage boosting transformer on the secondary winding, which compensates for the active losses of the installation and the equipment under test.

This allows you to get the above technical result.

The formation of a second voltage converter, compensating for active losses, can be performed on the principles of automatic regulation in various ways. The development of the invention characterizes a particular case and consists in the fact that the second voltage Converter is configured to form a compensating voltage in accordance with the vector expression:

- компенсирующее напряжение;Where $${\overline{e}}_k$$

- compensating voltage;

U ₀ is the nominal value of the test voltage;

U _n is the current value of the output voltage;

- выходной ток; $${\overline{i}}_n$$

- output current;

k _u , k _i are the coefficients of regulation of the second converter for voltage and current, respectively.

Brief Description of the Drawings

In FIG. 1 shows a General diagram of the device.

In FIG. 2 and 3 show possible structural diagrams of the component parts of the device (voltage converters).

In FIG. 4 shows the results of computer simulations of tests of a powerful transformer for short-circuit resistance carried out using the proposed device.

The implementation of the invention in view of its development

The device of FIG. 1 contains a capacitor bank (KB) 1, an inductor 2 with taps of various levels of high voltage 110-750 kV, a switch 3, a first voltage converter 4, a boost transformer 5, a second voltage converter 6, an output current and voltage sensor 7 (conventionally shown one combined sensor). Battery 1 is connected to the output of converter 4. Coil 2 is connected through switch 3 to battery 1. The secondary winding of transformer 5 is connected between the output of coil 2 and the output of the device, designed to connect the equipment under test.

The primary winding of the transformer 5 is connected to the output of the Converter 6, the information input of which is connected to the sensors 7.

In FIG. 1 also shows the elements of the test bench: a power transformer 8, from the windings of which, in a particular case, can be powered by converters 4 and 6, an operator console 9, a key 10 that connects the output of the device to the tested transformer 11 (in addition to the claimed device, devices can be placed on the test bench for other types of electrical equipment tests using elements 8-10).

The block diagram of the converter 4 shown in FIG. 2, comprises a rectifier-inverter 12 and a rectifier-inverter 13 with a control unit 14 and a smoothing inductor 15.

In FIG. 3 shows a block diagram of a converter 6 with controls. The converter 6 is made according to the voltage inverter circuit with pulse-width (PWM) control and a single-phase output, to which the primary winding of the transformer 5 is connected. The converter 6 contains an uncontrolled rectifier 16, a filter capacitor 17 and an inverter 18 on fully controlled semiconductor elements IGBT, or IGCT. In addition, the inverter 6 includes control elements of the inverter 18: a voltage regulator 19 with a gain k _u , a current regulator 20 with a gain k _i , a multiplier 21, an adder 22, and a PWM modulator 23.

The device operates as follows.

In the initial state, the device is connected to the network through a transformer 8, the primary winding of the transformer 11 through the secondary winding of the boost transformer 5 is connected to the required voltage class soldering of the inductor 2. Key 10 and switch 3 are open. The secondary winding of the transformer under test 11 is shorted. The control panel 9 of the test bench on the instructions of the operator (or under the control of the program) generates the commands "Charge KB" - "Excitation circuit" - "Short circuit" - "Blanking circuit".

By the command "Charge KB" from the remote control 9, the first converter 4 is turned on in the charge mode of the capacitor bank 1 to a predetermined voltage level.

By the command “Excitation of the circuit”, the converter 4 leaves the charge mode (the control pulses of the converter keys are removed), the switch 3 closes, and an oscillatory circuit with an oscillation frequency close to the industrial frequency of 50 Hz is formed from the battery 1 and coil 2.

By the command “Short circuit”, a series of opening pulses with a duration of 0.2 s each is supplied to the key 10. The sensor 7 of the output current and voltage gives the Converter 6 signals corresponding to the values of current and voltage at the output of the device.

в соответствии с векторным выражением (1).The Converter 6, controlled by the current and voltage of the sensor 7, generates a compensation voltage on the secondary winding of the transformer 5 $${\overline{e}}_k$$

in accordance with the vector expression (1).

суммируется с напряжением $${\overline{U}}_k$$

, снимаемым с катушки 2. Векторная сумма напряжений $${\overline{U}}_k+{\overline{e}}_k$$

поступает на первичную обмотку испытуемого трансформатора 11. При этом обеспечивается стабилизация выходного напряжения устройства с автоматической компенсацией активных потерь за счет положительной обратной связи по выходному току, глубина которой зависит от разности напряжений U₀-U_n.Voltage $${\overline{e}}_k$$

sums up with voltage $${\overline{U}}_k$$

removed from coil 2. Vector sum of stresses $${\overline{U}}_k+{\overline{e}}_k$$

arrives at the primary winding of the transformer under test 11. This ensures stabilization of the output voltage of the device with automatic compensation of active losses due to positive feedback on the output current, the depth of which depends on the voltage difference U ₀ -U _n .

After 0.2 s, by the command “Quenching of the circuit”, the key 10 is opened, and the converter 4 is transferred to the inverter mode for recovery of the unspent energy of the oscillatory circuit into the network.

The converter 4 (Fig. 2) is controlled in the charge and discharge modes with energy recovery of the oscillatory circuit by block 14 according to the commands from the remote control 10. In the charge mode of the capacitor bank 1, the rectifier 12 operates in a controlled rectifier mode, and in the bridge rectifier 13, the triggering pulses are given only highlighted in FIG. 2 thyristors of opposite shoulders. In the mode of quenching the oscillatory circuit with energy recovery into the network, the rectifier 12 is transferred to the inverter mode, and the rectifier 13 to the rectifier mode.

по выражению (1) формируется из постоянного напряжения, полученного на выходе выпрямителя 16 с помощью инвертора 18, управляемого элементами 19-23. Соответствующим выбором коэффициентов k_u. и k_i может быть реализована требуемая точность поддержания напряжения в режиме КЗ.In the Converter 6 (Fig. 3) the compensation voltage $${\overline{e}}_k$$

by the expression (1) is formed from a constant voltage obtained at the output of the rectifier 16 using an inverter 18, controlled by elements 19-23. The corresponding choice of coefficients k _u. and k _i , the required accuracy of voltage maintenance in the short circuit mode can be realized.

In this case, only active power is introduced into the test circuit by the converter 6, compensating for losses in the transformer 11 and the oscillating circuit. This power is 20-50 times less than the reactive power of the load (tested transformer in short circuit mode), provided by the oscillatory circuit.

In FIG. 2 shows the waveform of computer simulation of tests using the proposed device for resistance to short circuit power transformer type TDC 400000/220 kV. Designations on the waveform:

U _n is the voltage at the transformer under test (volts);

I _n - primary current of the tested transformer (amperes);

U _k - voltage on the oscillatory circuit (volts).

As can be seen from the waveform, the voltage U _n on the primary winding of the transformer under test during the short-circuit experiments is maintained stable and equal to the nominal value (voltage amplitude value ≈200 kV).

When testing such a transformer from a network or an autonomous source using known devices, a power pulse of ≈1350 MBА would be required, while to ensure the stability of the test voltage for 0.2 s, the power at the connection point of the device should be at least 20,000 MVA, which is practically possible only during testing, for example, directly on the territory of Konakovskaya TPP.

Claims (2)

1. A device for testing high-voltage electrical equipment for resistance to short circuit currents, comprising a capacitor bank connected to the output of the first voltage converter, an inductor connected via a switch to a storage capacitor, a boost-up transformer whose secondary winding is connected between the output of the inductor and the output of the device, designed to connect the equipment under test, and the primary winding is connected to the output of the second converter conjugation, an information input of which is connected with sensors output current and output voltage devices, the second voltage converter configured to generate on a secondary winding of the booster transformer voltage compensating ohmic losses and installation of the test equipment. 2. The device according to p. 1, in which the second voltage Converter is configured to form a compensating voltage in accordance with the vector expression:

,
Where $${\overline{e}}_k$$

- compensating voltage;
U ₀ is the nominal value of the test voltage;
U _n is the current value of the output voltage;
$${\overline{i}}_n$$

- output current;
k _u , k _i are the coefficients of regulation of the second converter for voltage and current, respectively.

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