Scheme for testing transformer-reactor equipment

Abstract

This utility model relates to electrical engineering, specifically testing equipment, and can be used for testing high-voltage insulation of transformers (power, regulating, traction, etc.), autotransformers, and shunt reactors of transformer-reactor equipment. The circuit for testing transformer-reactor equipment comprises a frequency converter, the phase outputs of which are connected to the primary windings of three step-up transformers connected at the output in a star formation, a reactive power compensation system based on a bank of static capacitors, a phase switch, measuring capacitors, and neutral switches.The step-up transformers are equipped with series-mounted tap-switching devices for the windings without excitation, each with a different control step; a bank of static capacitors is connected in a star configuration with a rigidly fixed neutral and is connected directly to the outputs of the step-up transformers; harmonic filters with the ability to bypass their inductive parts are connected in parallel to the outputs of the step-up transformers; measuring capacitors are installed on both sides of the test object, and their outputs are connected via an OR logic element to the control input of the frequency converter, providing voltage feedback directly at the point of voltage application to the test object. The technical result of the claimed utility model is to increase the operational efficiency and reliability of high-voltage insulation testing of transformer-reactor equipment. 3 clauses, 2 figs.

Description

[0001] The utility model relates to electrical engineering, in particular to testing equipment, and can be used for testing high-voltage insulation of transformers (power, regulating, traction, etc.), autotransformers, shunt reactors of transformer-reactor equipment.

[0002] A device is known for testing transformer-reactor equipment (see Russian Federation Patent No. 119544, IPC H02M 5 / 00, 08 / 20 / 2012), containing a static frequency converter, the output of which is connected to the primary windings of three single-phase transformers, and the input is connected to the output of the control unit, while the ends of the secondary windings of the single-phase transformers are connected together to a common point.

[0003] However, this solution has the following drawbacks: there is no neutral busbar for testing transformers when connected with neutral Yn; there is no capacitor to compensate for reactive power, which increases the load on the static frequency converter; and there is no provision for connecting test voltage feedback to the static frequency converter. All these factors reduce the efficiency and accuracy of the installation.

[0004] The closest device to the claimed one is a transformer testing rig (RU Patent 2665749, IPC G01R 31 / 02, September 4, 2018). The device contains an adjustable frequency and voltage converter, the phase outputs of which are connected to three single-phase transformers connected in a star connection. The transformer outputs are connected to a phase switch, the terminals of which are connected to a switch in the three-phase capacitor bank circuit.

[0005] The disadvantage of such a device is that disconnecting the neutral of the capacitor bank when operating on an asymmetric three-phase load (due to non-ideal symmetry of the tested transformer, or due to phase breakdown of the tested transformer) can lead to a redistribution of voltage between the capacitors and, as a result, cause their breakdown.

[0006] In addition, both devices use unregulated single-phase transformers, which reduces the dynamic range and results in the proportion of parasitic harmonics exceeding the test voltage when operating in the lower third of the operating voltage range.

[0007] Also, both devices do not have the ability to work with voltage feedback from the test object, and the regulation of test voltages occurs due to voltage feedback from the output of a static frequency converter, taking into account the set transformation ratio, thereby losses in the step-up transformer, busbars and compensating batteries do not make it possible to accurately maintain the specified test voltage in automatic mode.

[0008] The technical result of the utility model is to increase the operational efficiency and reliability of high-voltage insulation tests of transformer-reactor equipment.

[0009] The technical result is achieved by creating a circuit for testing transformer-reactor equipment, containing a frequency converter, the phase outputs of which are connected to the primary windings of three step-up transformers connected at the output in a star, a reactive power compensation system based on a battery of static capacitors, a phase switch, measuring capacitors and neutral switches.

[0010] In this case, the step-up transformers are equipped with series-installed devices for switching the taps of the windings without excitation with different control steps, the battery of static capacitors is connected in a star configuration with a rigidly fixed neutral and connected directly to the outputs of the step-up transformers, high-harmonic filters are connected in parallel to the outputs of the step-up transformers with the possibility of shunting their inductive part, measuring capacitors are installed on both sides of the test object, and their outputs are connected via an OR logical element to the control input of the frequency converter, providing voltage feedback directly at the point of application of voltage to the test object.

[0011] By equipping the step-up transformers (2) with series-installed tap-switching devices with different steps, a wide dynamic range of test voltage regulation is ensured, the proportion of parasitic harmonics is reduced, especially in the lower third of the operating range of the static frequency converter, which improves the accuracy and reliability of tests.

[0012] By connecting the static capacitor bank (3) in a star with a rigidly fixed neutral and connecting it directly to the outputs of the step-up transformers, voltage redistribution is eliminated under an asymmetric load or phase breakdown, breakdown of capacitors is prevented, and the reliability of the reactive power compensation system is increased.

[0013] Parallel connection of high harmonic filters (4) with the ability to shunt their inductive part allows connecting the filters only during tests requiring partial discharge measurements and shunting them under heavy loads, which reduces costs and increases operational flexibility.

[0014] Installing measuring capacitors (5, 9) on both sides of the test object makes it possible to monitor the voltage directly on the high and low voltage side, which improves the accuracy of maintaining the test voltage.

[0015] The feedback switch (10), implemented on the logical element "OR", connecting the outputs of the measuring capacitors with the control input of the frequency converter (1), allows you to organize voltage feedback directly at the test object with the ability to select the control point (high voltage side, low voltage side or converter output), which compensates for losses in transformers, buses and capacitors, automatically maintaining the specified test voltage with high accuracy.

[0016] The utility model is illustrated by drawings which show:

[0017] Fig. 1 - functional electrical diagram of the installation;

[0018] Fig. 2 - structural diagram of the feedback organization.

[0019] The figures indicate the following positions:

[0020] 1 - frequency converter,

[0021] 2 - step-up transformers with tap changers,

[0022] 3 - battery of static capacitors of the reactive power compensation system,

[0023] 4 - High harmonic filters,

[0024] 5 - measuring capacitors,

[0025] 6 - phase switch,

[0026] 7 - test object,

[0027] 8 - connecting the neutral to the test object,

[0028] 9 - measuring capacitors,

[0029] 10 - feedback switch.

[0030] The circuit for testing transformer-reactor equipment contains a frequency converter 1, step-up transformers 2 with devices for switching the taps of windings under load [two series-installed devices for switching the taps of windings without excitation (hereinafter - DST) with different control steps], a bank of static capacitors 3, connected in a star with a rigidly fixed neutral and connected directly to the outputs of transformers (2), high-harmonic filters 4 with the possibility of shunting the inductive part, measuring capacitors 5 and 9, a phase switch 6, switches 8 and an “OR” logical element 10 in the feedback circuit, the output of which is connected to the control input of the frequency converter 1. Switches (8) are used to connect the neutral of the test object.

[0031] The installation works as follows.

[0032] Converter 1 generates voltages of a specified amplitude and frequency at three outputs. Amplitude is adjustable from 1% to 100% of the nominal value, and frequency is adjustable from 45 to 200 Hz. Voltage from the outputs of converter 1 is fed to step-up transformers 2.

[0033] Two step-up transformers with different control steps are installed in series in the step-up transformers 2.

[0034] The first PBB is designed for coarse adjustment, while the second is for fine adjustment. This configuration allows for changes in the transformation ratio within specified limits and provides adjustment of the maximum output voltage of the high-voltage winding in 2.5 kV increments, ensuring a wide test voltage range.

[0035] The outputs of step-up transformers 2 are connected to a bank of static capacitors 3, which is part of the reactive power compensation system. Bank of static capacitors 3 is connected in a star configuration with a rigidly fixed neutral.

[0036] The capacity of static capacitor bank 3 is selected based on the parameters of the test object to maximize compensation of its reactive component. The design of static capacitor bank 3 may vary depending on the type of devices being tested, but this does not affect the essence of the solution. Converter 1 provides operation in a range from fully active to fully reactive power.

[0037] High-harmonic filters type 4 are standard LC filters, known from radio engineering, designed for the bandwidth required for applied-voltage testing with partial discharge measurement. They are intended to be connected only during applied-voltage testing with partial discharge measurement, so their nominal parameters are designed exclusively for this type of load, significantly reducing the cost of the filtering device. For higher test loads, high-harmonic filters type 4 can be shunted to bypass the inductive component.

[0038] Phase switch 6 allows testing of objects in both three-phase and single-phase modes. When phase switch 6 is closed (single-phase mode), the device outputs the total power of the three phases and the full power of the static capacitor bank 3. The return conductor (neutral) is designed for the total power of the three phases.

[0039] Sensing capacitors 5 and 9 are installed on both sides of the test object. These allow voltage measurements to be made directly on the high- and low-voltage sides, thereby adjusting the mode of converter 1 at the point where voltage is applied to the test object. Measuring capacitors 5 and 9 are standard capacitors used as capacitive voltage dividers. For example, if the test object is a transformer, various testing methods require monitoring the voltage on either the high-voltage side or the low-voltage side. Using the provided circuit allows for monitoring the voltage and its harmonic content at the desired point in the circuit, as well as compensating for the shape and amplitude of the voltage at the output of converter 1, taking into account the gain and losses in the circuit. To ensure compatibility with common test circuits, the ability to control the output of frequency converter 1 is retained.Connecting the neutral to the test object using switches 8 is carried out if the test object has windings with neutral terminals.

[0040] Transformers have various winding connection configurations. Some models require a neutral connection, while others do not. Switches 8 allow you to select the desired configuration.

[0041] The feedback circuit for compensation is assembled on the “OR” element 10 (see Fig. 2), which is a schematic designation that, in essence, implies manual or automatic switching of the test mode depending on the test program and test circuit.

[0042] The operator selects the point at which the voltage needs to be monitored and adjusted, or switches to the mode of maintaining the output of frequency converter 1. The PBB devices include an automated control unit, information about the position of the winding taps from which is transmitted via the data bus to frequency converter 1 (FC).

[0043] The transfer coefficients of step-up transformers 2, taking into account the tap switching positions and the current division coefficients of measuring capacitors 5 and 9, are automatically transmitted to frequency converter 1.

[0044] Implementation example.

[0045] High-voltage insulation tests can be carried out for power transformers, regulating transformers, impact transformers, generator (block) transformers, electric furnace transformers, autotransformers, traction transformers for railway substations and railway transport, shunt reactors, controlled shunt reactors with on-load tap-changers, with magnetization, with valve and thyristor control.

[0046] The test setup includes a 3 MVA step-up transformer (1) with an output frequency band from 45 to 200 Hz. Step-up transformers (2) OMI-1000 / 220 are equipped with two series-connected step-up transformers (PBVs). The first PBV has 5 taps and is designed for coarse regulation of the output voltage, while the second PBV has 10 taps and is designed for fine adjustment of the output voltage. Different tap switching modes make it possible to regulate the maximum output voltage of the HV winding in 2.5 kV increments. The static capacitor bank (3) has a maximum operating voltage (phase) of 108 kV, and a power per phase of 115.872 MVAr. High-frequency harmonic filters (4) with a rated phase voltage of 110 kV are connected to measure partial discharges in transformers and autotransformers.Measuring capacitors 5 have a rated voltage (phase) of 110 kV, the capacitance is 100 pF, measuring capacitors 9 have a rated voltage (phase) of 600 kV, the capacitance is 20 pF.

[0047] Test object 1. The test object is a three-phase transformer TDC 250000 / 500, with a high-voltage winding voltage of 525 kV and a low-voltage winding voltage of 20 kV. The transformer has a star-to-neutral connection for the high-voltage winding and a delta connection for the low-voltage winding. Tests are performed with switches 6 open, switches 8 open for the low-voltage winding and closed for the high-voltage winding. The voltage on the high-voltage winding is measured using measuring capacitors 9.

[0048] Calculated values ​​of the circuit parameters during the heating test: the static capacitor bank is configured for a rated voltage (phase) of 18 kV, power per phase of 7.705 MVAr, battery phase current of 1265 A, total phase current of 1269 A, the involved power of the power supply system taking into account losses in transformers, filters, busbars per phase of 80 kVA.

[0049] Test object 2. The test object is the ROMBS-100000 / 110 reactor, rated voltage 121 / √3 kV, power 100 MVA. Tests are performed with switches 6 closed, switches 8 closed. Voltage measurements are made using measuring capacitors 5.

[0050] Calculated values ​​of the circuit parameters during the heating test: the static capacitor bank is configured for a rated voltage (phase) of 108 kV, power per phase of 37.73 MVAr, phase current of the capacitor bank is 539 A, total phase current is 540 A, the involved power of the frequency converter, taking into account losses in transformers, filters, and busbars per phase is 90 kVA.

Claims

1. A circuit for testing transformer-reactor equipment, comprising a frequency converter, the phase outputs of which are connected to the primary windings of three step-up transformers connected at the output in a star, a reactive power compensation system based on a bank of static capacitors, a phase switch, measuring capacitors and neutral switches, characterized in that the step-up transformers are equipped with series-installed devices for switching the taps of the windings without excitation with different control steps, the bank of static capacitors is connected in a star configuration with a rigidly fixed neutral and is connected directly to the outputs of the step-up transformers, high-harmonic filters with the possibility of shunting their inductive part are connected in parallel to the outputs of the step-up transformers, the measuring capacitors are installed on both sides of the test object,and their outputs are connected via an OR logical element to the control input of the frequency converter, providing voltage feedback directly at the point of application of voltage to the test object.

2. The circuit according to paragraph 1, characterized in that the frequency converter is designed with an output frequency range from 45 to 200 Hz.

3. The circuit according to paragraph 1, characterized in that two devices for switching taps of windings without excitation (PBB) are installed in series in the step-up transformers, wherein the first PBB is intended for coarse regulation, and the second PBB for fine adjustment, with the possibility of regulating the maximum output voltage of the high-voltage winding in increments of 2.5 kV.

4. The circuit according to paragraph 1, characterized in that the higher harmonic filters are made in the form of LC filters tuned to the passband frequencies.

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