Method for measuring low-voltage direct current resistance of three-phase transformer bank

Abstract

The invention provides a method for measuring low-voltage direct-current resistance of a three-phase transformer bank, and belongs to the technical field of transformer measurement. The invention provides a method for measuring low-voltage direct-current resistance of a three-phase transformer bank. The method comprises the following steps of: connecting all phases of windings on a high-voltage side together; connecting the high-voltage side three-phase winding with the low-voltage side three-phase winding; direct current is introduced into the high-voltage side three-phase winding; measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured and the current of the corresponding high-voltage side winding or the corresponding low-voltage side winding; and calculating the direct current resistance of the to-be-measured phase according to the measured voltage and current. The three-phase transformer bank low-voltage direct-current resistance measuring method provided by the invention has the advantages that during measurement, direct current is introduced into the high-voltage side three-phase windings, so that the current in the three high-voltage side windings forms a loop, the number of excitation ampere turns of the three-phase iron core columns is increased, the three iron core columns are magnetically saturated, the inductance of coils is reduced, and the measurement accuracy is improved. And the test time is shortened.

Description

Technical Field

[0001] The invention belongs to the technical field of transformer measurement, and in particular relates to a method for measuring low-voltage direct resistance of a three-phase transformer group. Background Art

[0002] There are clear regulations on DC resistance measurement in transformer testing technology. Generally, a stable DC current is passed through the winding and the voltage at the beginning and end of the winding is measured. However, for some triangular low-voltage windings with large capacity and few turns, especially five-column products with side columns on the iron core, the test stabilization time is very long.

[0003] Due to the special structure of the three-phase transformer group, it has three independent iron cores, and there is no magnetic circuit connection between the three cores; and the DC resistance of the low-voltage triangle-connected winding is related to the phase resistance of the three-phase winding. Therefore, according to the original method, when one-phase high-voltage magnetic assist is used, only one-phase iron core column magnetic circuit is saturated, and the other two-phase iron core columns are not saturated. The excitation ampere-turns of the other two-phase iron core columns have not increased, and the low-voltage resistance value has not reached the final stable state, and the test time is very long. Summary of the invention

[0004] The purpose of the present invention is to provide a method for measuring low-voltage direct resistance of a three-phase transformer group, aiming to solve the above problems.

[0005] To achieve the above object, the technical solution adopted by the present invention is: to provide a method for measuring the low-voltage direct resistance of a three-phase transformer group, comprising the following steps:

[0006] Connect the phase windings on the high voltage side together;

[0007] Connect the three-phase winding on the high-voltage side with the three-phase winding on the low-voltage side;

[0008] Passing direct current into the three-wire winding on the high-voltage side;

[0009] Measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured and the current of the corresponding high-voltage side winding or the corresponding low-voltage side winding;

[0010] Calculate the DC resistance of the phase to be measured based on the measured voltage and current.

[0011] In a possible implementation, connecting the phase windings on the high voltage side together includes:

[0012] The high-voltage side winding of the phase to be tested is used as the input end of the high-voltage side three-phase winding, the output ends of the remaining high-voltage side windings are connected, and the output ends of the remaining high-voltage side windings are used as the output end of the high-voltage side three-phase winding.

[0013] In a possible implementation, connecting the high-voltage side three-phase winding with the low-voltage side three-phase winding includes:

[0014] Using the corresponding low-voltage side winding to be tested as a low-voltage side input terminal;

[0015] The output end of the three-phase winding on the high-voltage side is connected to the input end on the low-voltage side.

[0016] In a possible implementation, the direct current is passed through the three-phase windings on the high-voltage side, including:

[0017] A direct current is input to the input end of the high-voltage side three-phase winding, and the direct current flows out from the output end of the high-voltage side three-phase winding and enters the low-voltage side three-phase winding.

[0018] In one possible implementation, if the phases to be tested are phase A and phase a, the high-voltage side phase A is used as the input end of the high-voltage side winding, and the output ends of phases B and C on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase a on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase c is used as the output end of the low-voltage side winding.

[0019] In a possible implementation, measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured includes:

[0020] The voltage between the first and tail ends of the A-phase winding on the high-voltage side and the voltage between the a-phase and c-phase output ends on the low-voltage side are measured.

[0021] In one possible implementation, if the phases to be tested are phase B and phase b, the high-voltage side phase B is used as the input end of the high-voltage side winding, and the output ends of phase A and phase C on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase b on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase a is used as the output end of the low-voltage side winding.

[0022] In a possible implementation, measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured includes:

[0023] The voltage between the first and tail ends of the B-phase winding on the high-voltage side and the voltage between the b-phase and a-phase output ends on the low-voltage side are measured.

[0024] In one possible implementation, if the phases to be tested are phase C and phase c, the high-voltage side phase C is used as the input end of the high-voltage side winding, and the output ends of phase A and phase B on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase c on the low-voltage side is used as the input end of the low-voltage side winding, and the phase b on the low-voltage side is used as the output end of the low-voltage side winding.

[0025] In a possible implementation, measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured includes:

[0026] The voltage between the first and tail ends of the C-phase winding on the high-voltage side and the voltage between the c-phase and b-phase output ends on the low-voltage side are measured.

[0027] The beneficial effect of the low-voltage direct resistance measurement method of the three-phase transformer group provided by the present invention is that: compared with the prior art, when measuring, direct current is passed through the three-phase windings on the high-voltage side, so that the currents in the three high-voltage side windings form a loop, the excitation ampere-turns of the three-phase iron core columns are increased, and the three iron core columns are magnetically saturated, so as to reduce the inductance of the coil, thereby shortening the test time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 A schematic diagram of the main steps of the method for measuring low-voltage direct resistance of a three-phase transformer group provided by an embodiment of the present invention;

[0030] Figure 2 A schematic diagram of the main steps of connecting a high-voltage side three-phase winding with a low-voltage side three-phase winding provided by an embodiment of the present invention;

[0031] Figure 3 This is the wiring diagram when the phase to be tested is the A phase on the high voltage side;

[0032] Figure 4 This is the wiring diagram when the phase to be tested is the high voltage side phase B;

[0033] Figure 5 This is the wiring diagram when the phase to be tested is the C phase on the high voltage side;

[0034] Figure 6 This is a wiring diagram for single-phase magnetic auxiliary method testing in the prior art. DETAILED DESCRIPTION

[0035] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] There are clear regulations on DC resistance measurement in transformer test technology. Generally, a stable DC current is passed through the winding to measure the voltage at the beginning and end of the winding. However, for some triangular low-voltage windings with large capacity and few turns, especially five-column products with side columns on the core, the test stabilization time is very long. Later, the high-voltage corresponding winding and the measured low-voltage winding were often connected in series to keep the excitation direction of the current in the two windings to the core the same, increase the excitation ampere-turns, saturate the core to reduce the inductance of the coil, and shorten the test time. Wiring diagram Figure 6 shown.

[0037] The existing test method is not suitable for the DC resistance test of the low-voltage triangle-connected winding of a three-phase transformer group. The three cores of the three-phase transformer group are independent of each other, and the low-voltage winding is connected in a triangle. The measured low-voltage line resistance is related to the three phase resistances. Therefore, when the high-voltage one phase and the low-voltage are connected in series, the excitation ampere-turns of the other two phase cores are not increased, so the test time is very long.

[0038] Due to the special structure of the three-phase transformer group, it has three independent iron cores, and there is no magnetic circuit connection between the three cores; and the DC resistance of the low-voltage triangle-connected winding is related to the phase resistance of the three-phase winding. Therefore, according to the original method, when one-phase high-voltage magnetic assist is used, only one-phase iron core column magnetic circuit is saturated, and the other two-phase iron core columns are not saturated. The excitation ampere-turns of the other two-phase iron core columns have not increased, and the low-voltage resistance value has not reached the final stable state, and the test time is still very long.

[0039] In order to shorten the measurement time, an embodiment of the present invention provides a method for measuring low-voltage direct resistance of a three-phase transformer group.

[0040] Please refer to Figures 1 to 5 Now, a specific implementation method of the low-voltage direct resistance measurement method of the three-phase transformer group provided by the present invention is described.

[0041] Reference Figure 1 , a method for measuring low voltage direct resistance of a three-phase transformer group includes the following steps:

[0042] S1. Connect the phase windings on the high voltage side together.

[0043] S2. Connect the three-phase winding on the high-voltage side to the three-phase winding on the low-voltage side.

[0044] S3. DC current is passed through the three-wire windings on the high-voltage side.

[0045] S4. Measure the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured and the current of the corresponding high-voltage side winding or the corresponding low-voltage side winding.

[0046] S5. Calculate the DC resistance of the phase to be measured based on the measured voltage and current.

[0047] Compared with the prior art, the method for measuring low-voltage direct resistance of a three-phase transformer group provided by the present invention has the following characteristics: during measurement, direct current is passed through the three-phase windings on the high-voltage side, so that the currents in the three high-voltage side windings form a loop, the excitation ampere-turns of the three-phase iron core columns are increased, and the three-phase iron core columns are all magnetically saturated, so as to reduce the inductance of the coil, thereby shortening the test time.

[0048] Further, step S1. connecting the phase windings on the high voltage side together specifically includes:

[0049] The high-voltage side winding of the phase to be tested is used as the input end of the high-voltage side three-phase winding, the output ends of the remaining high-voltage side windings are connected, and the output ends of the remaining high-voltage side windings are used as the output end of the high-voltage side three-phase winding.

[0050] Reference Figure 2 , further, step S2. connecting the high-voltage side three-phase winding with the low-voltage side three-phase winding, comprising the following steps:

[0051] S21. Use the corresponding low-voltage side winding to be tested as the low-voltage side input terminal.

[0052] S22. Connect the output end of the three-phase winding on the high-voltage side to the input end on the low-voltage side.

[0053] Furthermore, direct current is passed through the three-wire winding on the high-voltage side, including:

[0054] A direct current is input to the input end of the three-phase winding on the high-voltage side, and the direct current flows out from the output end of the three-phase winding on the high-voltage side and enters the three-phase winding on the low-voltage side.

[0055] Reference Figure 3 Further, if the phases to be measured are phase A and phase a, the high-voltage side phase A is used as the input end of the high-voltage side winding, and the output ends of phases B and C on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase a on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase c is used as the output end of the low-voltage side winding.

[0056] Further, measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured includes:

[0057] Measure the voltage at the beginning and end of the A-phase winding on the high-voltage side and the voltage between the a and c-phase output terminals on the low-voltage side.

[0058] Reference Figure 4 Further, if the phases to be measured are phase B and phase b, the high-voltage side phase B is used as the input end of the high-voltage side winding, and the output ends of phase A and phase C on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase b on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase a is used as the output end of the low-voltage side winding.

[0059] Further, measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured includes:

[0060] Measure the voltage at the beginning and end of the B-phase winding on the high-voltage side and the voltage between the b- and a-phase output terminals on the low-voltage side.

[0061] Reference Figure 5 Further, if the phases to be tested are phase C and phase c, the high-voltage side phase C is used as the input end of the high-voltage side winding, and the output ends of phase A and phase B on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase c on the low-voltage side is used as the input end of the low-voltage side winding, and the phase b on the low-voltage side is used as the output end of the low-voltage side winding.

[0062] Further, measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured includes:

[0063] Measure the voltage at the beginning and end of the C-phase winding on the high-voltage side and the voltage between the c-phase and b-phase output terminals on the low-voltage side.

[0064] It can be seen from the wiring diagram of the new test method that DC current is passed through the three-phase high-voltage windings, so that the currents in the three high-voltage windings form a loop, and the excitation ampere-turns of the three core columns are increased, so that the three core columns are saturated to reduce the inductance of the coil and shorten the test time.

[0065] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring low voltage direct resistance of a three-phase transformer group, characterized in that: The following steps are involved: Connect the phase windings on the high voltage side together; Connect the three-phase winding on the high-voltage side with the three-phase winding on the low-voltage side; Passing direct current into the three-wire winding on the high-voltage side; Measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be measured and the current of the corresponding high-voltage side winding or the corresponding low-voltage side winding; Calculate the DC resistance of the phase to be measured based on the measured voltage and current.

2. The method for measuring low voltage direct resistance of a three-phase transformer group according to claim 1, characterized in that: Connect the high voltage side phase windings together, including: The corresponding high-voltage side winding to be tested is used as the input end of the high-voltage side three-phase winding, the output ends of the remaining high-voltage side windings are connected, and the output ends of the remaining high-voltage side windings are used as the output end of the high-voltage side three-phase winding.

3. The method for measuring low voltage direct resistance of a three-phase transformer group as claimed in claim 2, characterized in that: Connect the high-voltage side three-phase winding with the low-voltage side three-phase winding, including: Using the corresponding low-voltage side winding to be tested as a low-voltage side input terminal; The output end of the three-phase winding on the high-voltage side is connected to the input end on the low-voltage side.

4. The method for measuring low voltage direct resistance of a three-phase transformer group as claimed in claim 2, characterized in that: A direct current is supplied to each of the three-phase windings on the high-voltage side, including: A direct current is input into the input end of the corresponding high-voltage side winding to be tested, and the direct current flows out from the output ends of the remaining windings on the high-voltage side and enters the corresponding phase winding on the low-voltage side.

5. The method for measuring low voltage direct resistance of a three-phase transformer group as claimed in claim 3, characterized in that: If the phases to be tested are phase A and phase a, the high-voltage side phase A is used as the input end of the high-voltage side winding, the output ends of phases B and C on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase a on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase c is used as the output end of the low-voltage side winding.

6. The method for measuring low voltage direct resistance of a three-phase transformer group according to claim 5, characterized in that: Measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be tested, including: The voltage between the first and tail ends of the A-phase winding on the high-voltage side and the voltage between the a-phase and c-phase output ends on the low-voltage side are measured.

7. The method for measuring low voltage direct resistance of a three-phase transformer group as claimed in claim 3, characterized in that: If the phases to be tested are phase B and phase b, the high-voltage side phase B is used as the input end of the high-voltage side winding, and the output ends of phase A and phase C on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase b on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase a is used as the output end of the low-voltage side winding.

8. The method for measuring low voltage direct resistance of a three-phase transformer group according to claim 7, characterized in that: Measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be tested, including: The voltage between the first and tail ends of the B-phase winding on the high-voltage side and the voltage between the b-phase and a-phase output ends on the low-voltage side are measured.

9. The method for measuring low voltage direct resistance of a three-phase transformer group as claimed in claim 3, characterized in that: If the phases to be tested are phase C and phase c, the high-voltage side phase C is used as the input end of the high-voltage side winding, the output ends of phase A and phase B on the high-voltage side are connected together and used as the output end of the high-voltage side three-phase winding; the output end of phase c on the low-voltage side is used as the input end of the low-voltage side winding, and the low-voltage side phase b is used as the output end of the low-voltage side winding.

10. The method for measuring low voltage direct resistance of a three-phase transformer group according to claim 9, characterized in that: Measuring the voltage of the corresponding high-voltage side winding and the corresponding low-voltage side winding to be tested, including: The voltage between the first and tail ends of the C-phase winding on the high-voltage side and the voltage between the c-phase and b-phase output ends on the low-voltage side are measured.

Images