CN104502813A - Converter transformer symmetrical pressurization partial discharge test circuit - Google Patents

Abstract

The invention discloses a converter transformer symmetrical pressurization partial discharge test circuit. The circuit comprises a frequency conversion power source, an excitation transformer T1 and an excitation transformer T2 which are of the same structure, a first voltage divider, a second voltage divider, a first compensation reactor branch and a second compensation reactor branch. The high-voltage tail ends of the high-voltage windings of the excitation transformer T1 and the excitation transformer T2, after respectively passing through an ammeter A1 and an ammeter A2, are grounded, and the high-voltage winding output end of the excitation transformer T1 and the high-voltage winding output end of the excitation transformer T2 are respectively connected with the two ends of a valve side winding of a converter transformer; and the first compensation reactor branch comprises a fixed compensation reactor L1 and an adjustable reactor L3 which are connected in series, and the second compensation reactor branch comprises a fixed compensation reactor L2 and an adjustable reactor L4 which are connected in series. According to the invention, through the adjustable reactors, it is ensured that the imbalance of the voltage at the two ends of the valve side winding of the converter transformer and the circulation phenomenon generated when reactive power at the two ends are not consistent when the converter transformer is subjected to a symmetrical pressurization partial discharge test are prevented.

Description

Symmetrical pressurized partial discharge test circuit for converter transformers

technical field

The invention relates to the technical field of converter transformers, in particular to a test circuit for long-duration induced voltage band partial discharge measurement tests during on-site handover tests of converter transformers.

Background technique

At present, due to the restriction of the voltage level of the excitation transformer in the field partial discharge test of the converter transformer, the pressure is generally applied from the end with a lower voltage level, that is, the valve side. Due to the relatively small transformer ratio of the delta-connected converter, in order to ensure that the voltage level of the test device is reasonable and the valve side does not exceed the AC withstand value, the field test adopts a symmetrical pressurization method on the valve side. Please refer to shown in Fig. 1, it comprises a kind of converter transformer symmetrical pressurized partial discharge test circuit, and it comprises variable frequency power supply 1, excitation transformer T1 and excitation transformer T2 with the same structure, and the first voltage divider, the second voltage divider device, the first compensating reactor branch, and the second compensating reactor branch; among them, the frequency conversion power supply 1 provides input power for the excitation transformer T1 and the excitation transformer T2, and the positive and negative output terminals of the frequency conversion power supply 1 are the same as the two excitation transformer T1 The connection mode of the input terminal of the first low-voltage winding is opposite to that of the positive and negative output terminals of the variable frequency power supply 1 and the input terminals of the two low-voltage windings of the excitation transformer T2; The output end of the high-voltage winding of the high-voltage winding is connected to one end of the valve-side winding of the converter transformer 2 through the first connecting line through the bushing 21 on the valve side of the converter transformer; the high-voltage tail end of the high-voltage winding of the excitation transformer T2 is grounded after passing through the ammeter A2, and the excitation transformer T2 The output end of the high-voltage winding is connected to the other end of the valve-side winding of the converter transformer 2 through the second connecting line through the converter valve-side bushing 22; one end of the first voltage divider and the first compensating reactor branch are both grounded, The other ends are connected to the first connection line; one end of the second voltage divider and the second compensation reactor branch are both grounded, and the other ends are connected to the second connection line; one end of the grid side winding of the converter transformer 2 is grounded , the other end is connected to a partial discharge tester; wherein, the first compensation reactor branch and the second compensation reactor branch are fixed compensation reactor L1 and fixed compensation reactor L2 respectively. Due to the difference in the inlet capacitance at both ends of the converter valve side, the fixed compensation reactance cannot meet the requirement that both ends of the converter valve side be in a fully compensated state at the same time. This will lead to a capacity rise effect at the end of the large capacitance, resulting in unequal voltages at both ends, and sometimes a large difference, which affects the safety of the test. In addition, if one end is capacitive and the other end is inductive, a circulating current will be formed between the excitation transformer and the variable frequency power supply, which will cause damage to the excitation transformer and the variable frequency power supply.

Contents of the invention

In order to overcome the problem that the existing symmetrical pressurization cannot solve the problem of double-terminal voltage and reactive power imbalance, the present invention provides a test method, which can not only solve the problem of capacity rise effect that may occur, but also solve the problem that the two-terminal cannot be simultaneously Circulation problems when fully compensated.

A partial discharge test circuit for symmetrical pressurization of a converter transformer, which includes a variable frequency power supply, an excitation transformer T1 and an excitation transformer T2 with the same structure, a first voltage divider, a second voltage divider, a first compensation reactor branch, The second compensation reactor branch circuit; wherein, the variable frequency power supply provides input power for the excitation transformer T1 and the excitation transformer T2, and the positive and negative output terminals of the variable frequency power supply are connected with the two low-voltage winding input terminals of the excitation transformer T1 and the positive and negative terminals of the variable frequency power supply The connection mode of the negative output terminal is opposite to that of the input terminals of the two low-voltage windings of the excitation transformer T2; the high-voltage tail end of the high-voltage winding of the excitation transformer T1 is grounded after passing through the ammeter A1, and the output terminal of the high-voltage winding of the excitation transformer T1 passes through the first connecting line through the first The valve-side bushing of the converter transformer is connected to one end of the valve-side winding of the converter transformer; the high-voltage tail end of the high-voltage winding of the excitation transformer T2 is grounded after passing through the ammeter A2, and the output end of the high-voltage winding of the excitation transformer T2 passes through the second connection line through the second The bushing on the converter valve side is connected to the other end of the valve side winding of the converter transformer; one end of the first voltage divider and the first compensating reactor branch are both grounded, and the other ends are connected to the first connection line; One end of the second voltage divider and the second compensation reactor branch are both grounded, and the other end is connected to the second connection line; one end of the grid side winding of the converter transformer is grounded, and the other end is connected to a partial discharge tester ; The first compensation reactor branch includes a fixed compensation reactor L1 and an adjustable reactor L3 connected in series, and the second compensation reactor branch includes a fixed compensation reactor L2 and an adjustable reactor L4 connected in series.

The first voltage divider includes a high voltage dividing capacitor C1 and a low voltage dividing capacitor C2 connected in series, and the second voltage divider includes a high voltage dividing capacitor C3 and a low voltage dividing capacitor C4 connected in series.

The two ends of the low voltage dividing capacitor C2 and the low voltage dividing capacitor C4 are connected in parallel with a voltmeter V1 and a voltmeter V3 respectively.

A voltmeter V2 is connected in parallel between the two low-voltage winding input ends of the excitation transformer T1, and a voltmeter V4 is connected in parallel between the two low-voltage winding input ends of the excitation transformer T2.

The reactance values of the fixed compensation reactor L1 and the fixed compensation reactor L3 are 10H, and the adjustable reactor L2 and the adjustable reactor L4 are continuously adjustable reactors of 5-10H.

In the present invention, a continuous adjustable reactance of 5-10H is connected in series to the branch circuit of the compensating reactor at the high voltage end, which is connected in series with the fixed compensating reactor, and the compensating reactance values at both ends can be adjusted so that each end can assume a fully compensated state. During the test, adjust the output frequency of the variable frequency power supply at a lower voltage so that the variable frequency power supply outputs the minimum current (the current value output by the variable frequency power supply can be monitored through the control terminal of the frequency conversion cabinet, or can be obtained by measuring the ammeter). At this time, the output current of the variable frequency power supply is basically It is the active current. At this frequency, one end of the valve side winding of the converter transformer forms an undercompensation, that is, a capacitive current, and the other end of the valve side winding of the converter transformer forms an overcompensation, that is, an inductive current. At this time, adjust the valve side winding of the converter transformer The adjustable reactance value at both ends is specifically to reduce the adjustable reactance value at the capacitive current end and increase the adjustable reactance value at the inductive current end. When the high-voltage tail-to-ground current of the two excitation transformers is minimized, full compensation is achieved. The method of judging the valve side winding of the converter transformer is obtained by calculation. During field operation, the judgment is made by measuring the input current of the excitation transformer T1 and the excitation transformer T2. If the reactance value of the compensation reactor branch is increased, the corresponding If the input current of the excitation transformer becomes smaller, one end of the valve side winding of the converter transformer corresponding to the connection of the excitation transformer will be inductive; on the contrary, if the reactance value of the compensating reactor branch is reduced, the corresponding input current of the excitation transformer will become smaller, then One end of the valve side winding of the converter transformer correspondingly connected to the excitation transformer is capacitive. When fully compensated, the actual transformation ratio of the high and low voltage side of the excitation transformer is equal to the rated transformation ratio of the wiring.

The beneficial effect of the present invention is that it can ensure that the circulating current phenomenon caused by the unbalanced voltage at both ends of the valve side winding of the converter transformer and the inconsistency of the reactive power at both ends will not occur during the symmetrical pressurized partial discharge test of the converter transformer, and can ensure the smoothness of the test. The method is effective and practical without damaging the converter and test equipment.

Description of drawings

Fig. 1 is a schematic circuit diagram of an existing converter transformer symmetrical pressurized partial discharge test circuit.

Fig. 2 is a schematic circuit diagram of a symmetrical pressurized partial discharge test circuit of a converter transformer of the present invention.

Detailed ways

In order to better understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example

Please refer to Fig. 2, a partial discharge test circuit for symmetrical pressurization of a converter transformer, which includes a variable frequency power supply 1, an excitation transformer T1 and an excitation transformer T2 with the same structure, and a first voltage divider, a second voltage divider, The first compensating reactor branch and the second compensating reactor branch; among them, the two low-voltage winding input terminals of the excitation transformer T1 are marked as b1 terminal and x1 terminal respectively, and its high-voltage winding includes high-voltage tail X1 terminal and high-voltage output terminal B1 , the two low-voltage winding input ends corresponding to the excitation transformer T2 are marked as b2 and x2 respectively, and its high-voltage winding includes a high-voltage tail X2 and a high-voltage output B2. The converter transformer 2 includes valve-side windings and grid-side windings, wherein the two ends of the valve-side windings are provided with converter valve-side bushings 21 (marked as converter valve side 3.1 bushings) and converter valve-side bushings. Pipe 22 (marked as converter valve side 3.2 bushing). One end of the grid-side winding of the converter transformer 2 is grounded, and the other end (the position of the 1.1 bushing on the converter grid side) is suspended in the air after being equipped with a voltage equalizing ring of an appropriate size, and the end screen is connected to a partial discharge tester.

Variable frequency power supply 1 provides input power for excitation transformer T1 and excitation transformer T2, and the positive and negative output terminals of variable frequency power supply 1 are connected to the input terminals of the two low-voltage windings of excitation transformer T1, and the positive and negative output terminals of variable frequency power supply 1 are connected to excitation transformer T2 The connection mode of the two low-voltage winding input ends of the inverter is reversed. For example, when terminal a1 and terminal x1 are respectively connected to the positive and negative output terminals of the variable frequency power supply 1, then terminal x2 and terminal b2 are respectively connected to the positive and negative output terminals of the variable frequency power supply 1. A voltmeter V2 is connected in parallel between the b1 terminal and the x1 terminal, and a voltmeter V4 is connected in parallel between the b2 terminal and the x2 terminal.

The X1 end of the high-voltage tail is connected to the ground and connected to the ammeter A1 in series. The high-voltage output B1 end is connected to one end of the valve side winding of the converter transformer 2 through the first connecting line through the bushing 21 on the valve side of the converter transformer; the X2 end of the high-voltage tail is connected to the ground and connected in series. The ammeter A2 is connected, and the high-voltage output B2 terminal is connected to the other end of the valve-side winding of the converter transformer 2 through the second connection line through the converter valve-side bushing 22 .

One end of the first voltage divider and the first compensating reactor branch are both grounded, and the other end is connected to the first connection line; one end of the second voltage divider and the second compensating reactor branch are both grounded, and the other end is connected Connected to the second connection line; wherein, the first voltage divider includes a high voltage voltage dividing capacitor C1 and a low voltage voltage dividing capacitor C2 connected in series, and the second voltage divider includes a high voltage voltage dividing capacitor C3 and a low voltage voltage dividing capacitor C4 connected in series. The high voltage dividing capacitor C1 and the high voltage dividing capacitor C3 have the same capacitance, and the low voltage dividing capacitor C2 and the low voltage dividing capacitor C4 have the same capacitance. The two ends of the low-voltage voltage dividing capacitor C2 and the low-voltage voltage dividing capacitor C4 are respectively connected in parallel with a voltmeter V1 and a voltmeter V3. One of the purposes of setting the four voltmeters is to monitor the voltage value of each position of the test circuit. Another purpose It is to verify whether the actual transformation ratio of the high and low voltage side of the excitation transformer is equal to the rated transformation ratio of the wiring. If they are equal, both ends of the valve side of the converter transformer are in a fully compensated state at the same time.

In order to prevent the capacity rise effect during the test due to the difference in the inlet capacitance at both ends of the valve side winding of the converter, which will affect the safety of the test, and also prevent the circulating current between the variable frequency power supply 1 and the excitation transformer T1 or excitation transformer T2, which will cause damage to the device , in a preferred embodiment of the present invention, the first compensation reactor branch is matched by a series fixed compensation reactor L1 and an adjustable reactor L3, and the second compensation reactor branch is composed of a series series fixed compensation reactor L2 and an adjustable Adjust the reactor L4 to match.

For a delta-connected converter transformer, the inlet capacitance value at both ends of the valve side winding is about 50nF, the reactance value of fixed compensating reactor L1 and fixed compensating reactor L3 is 10H, and the adjustable reactor L2 and adjustable reactance The reactor L4 is a continuously adjustable reactor of 5-10H, and the frequency during the test is about 150Hz. The combined use of fixed reactance and adjustable reactance can make both ends of the converter valve side winding fully compensated at the same time. When fully compensated, the voltage at both ends of the converter valve side winding is equal, and the reactive power at both ends is due to different compensation methods. If they are not equal, the high-voltage tail currents of the two excitation transformers T1 and T2 (measured by the ammeter A1 and the ammeter A2) both reach the minimum and are pure active currents. There will be no circulating current between the variable frequency power supply and the two excitation transformers.

It should be understood that the application of the present invention is not limited to the above examples, and those skilled in the art can make improvements or transformations according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (5)

1. a converter power transformer symmetry pressurization partial discharge test circuit, it comprises variable-frequency power sources (1), structure identical exciting transformer T1 and exciting transformer T2 and the first voltage divider, the second voltage divider, the first compensation reactor branch road, the second compensation reactor branch road; Wherein, variable-frequency power sources (1) provides input power for exciting transformer T1 and exciting transformer T2, and the positive-negative output end of variable-frequency power sources (1) is contrary with the connected mode of two low pressure winding input ends of exciting transformer T2 with the positive-negative output end of variable-frequency power sources (1) with the connected mode of two low pressure winding input ends of exciting transformer T1; High pressure tail end ground connection after reometer A1 of the high pressure winding of exciting transformer T1, the high pressure winding output terminal of exciting transformer T1 is connected to one end of converter power transformer (2) valve side winding through the first converter transformer valve side sleeve (21) by the first connecting line; High pressure tail end ground connection after reometer A2 of the high pressure winding of exciting transformer T2, the high pressure winding output terminal of exciting transformer T2 is connected to the other end of converter power transformer (2) valve side winding through the second converter transformer valve side sleeve (22) by the second connecting line; The equal ground connection in one end of described first voltage divider and the first compensation reactor branch road, the other end is all connected on the first connecting line; The equal ground connection in one end of described second voltage divider and the second compensation reactor branch road, the other end is all connected on the second connecting line; Source side winding one end ground connection of described converter power transformer (2), the other end connects instrument for measuring partial discharge; It is characterized in that, the first compensation reactor branch road comprises fixed compensation reactor L1 and the REgulatable reactor L3 of series connection, and described second compensation reactor branch road comprises fixed compensation reactor L2 and the REgulatable reactor L4 of series connection.

2. converter power transformer symmetry pressurization partial discharge test circuit according to claim 1, it is characterized in that, described first voltage divider comprises high pressure derided capacitors C1 and the low pressure derided capacitors C2 of series connection, and described second voltage divider comprises high pressure derided capacitors C3 and the low pressure derided capacitors C4 of series connection.

3. converter power transformer according to claim 2 symmetry pressurization partial discharge test circuit, is characterized in that, the two ends of described low pressure derided capacitors C2 and low pressure derided capacitors C4 respectively and meet a voltage table V1 and voltage table V3.

4. the converter power transformer symmetry pressurization partial discharge test circuit according to any one of claim 1-3, it is characterized in that, meet a voltage table V2 between two low pressure winding input ends of described exciting transformer T1, meet a voltage table V4 between two low pressure winding input ends of described exciting transformer T2.

5. the converter power transformer symmetry pressurization partial discharge test circuit according to any one of claim 1-3, it is characterized in that, the reactance value of described fixed compensation reactor L1 and fixed compensation reactor L3 is 10H, and REgulatable reactor L2 and REgulatable reactor L4 is the continuous adjustable reactor of 5-10H.