CN112067878A - Capacitance current on-line measuring method and device for secondary side bias capacitor of grounding transformer - Google Patents
Capacitance current on-line measuring method and device for secondary side bias capacitor of grounding transformer Download PDFInfo
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- CN112067878A CN112067878A CN202010911645.6A CN202010911645A CN112067878A CN 112067878 A CN112067878 A CN 112067878A CN 202010911645 A CN202010911645 A CN 202010911645A CN 112067878 A CN112067878 A CN 112067878A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/003—Measuring mean values of current or voltage during a given time interval
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
Abstract
The invention provides a capacitance current online measurement method and device of a secondary side bias capacitor of a grounding transformer, which relate to the technical field of fault processing of a power system. The invention can artificially change the asymmetry of the system, control and improve the voltage and the current of the neutral point, overcome the problem that the traditional method cannot accurately measure the single-phase grounding capacitance and the current of the power system with the neutral point grounded through the arc suppression coil because the voltage and the current of the neutral point are too low when the symmetry of the system is good, improve the online measurement speed and the online measurement precision of the arc suppression coil grounding system of the power grid, further reduce the probability of faults of the medium-voltage power grid due to bus grounding and be beneficial to the stable and reliable operation of the power system.
Description
Technical Field
The invention relates to the technical field of fault processing of power systems, in particular to a capacitance current online measurement method and device of a secondary side bias capacitor of a grounding transformer.
Background
In a 6-66KV power system, when the system capacitance current is greater than 10A, the neutral point is typically required to be grounded through the arc suppression coil. Whether the pre-tuning arc suppression coil or the random tuning arc suppression coil is adopted, in order to accurately compensate the capacitance current of the system, the capacitance current of the system must be accurately measured on line.
The current methods for measuring the capacitance current of the power system include: two-step calculation, displacement curve, injection signal, etc.
In the two-gear calculation method, in order to ensure the calculation accuracy, the system is required to have a certain asymmetry degree, namely the neutral point voltage of the system is required to be greater than a certain limit value, and the gear needs to be adjusted during measurement, so that the time is long. The method is widely applied to automatic arc suppression coil compensation devices, basically has the conditions of large measurement error and inaccurate compensation, and particularly has the problems of good symmetry and low neutral point voltage generally for a 10KV cable system.
The displacement curve method finds the compensation point by continuously adjusting the gear and searching the resonance point, is simple and intuitive, has more adjustment times although the compensation is accurate, and has the problems of tone modulation or tone rejection and the like caused by the poor control of the upper limit and the lower limit of a start-up threshold.
The signal injection method is characterized in that a non-power frequency signal is injected into a system, the response of the non-power frequency signal is sampled, the capacitance current of the system is calculated, core elements such as a power amplifier and the like are easy to damage due to the fact that the injected signal is weak, the non-power frequency signal is poor in frequency adaptability, measurement is limited, the situation that numerical values are inaccurate sometimes caused, interference is caused to the system, the reliability of an injection device is not suitable for long-term online operation, and the like, and the signal injection method is not widely accepted and adopted.
The accurate online measurement of the capacitance current of the system is a precondition that the automatic arc suppression coil compensation system can play a role correctly, and the existing method for measuring the capacitance current of the system still has various problems, so that a method capable of accurately measuring the capacitance current of the system online under various working conditions is urgently needed to eliminate the phenomenon that a large amount of compensation is inaccurate and even electric power accidents are caused in the automatic tuning arc suppression coil in the electric power system.
Disclosure of Invention
The invention aims to provide a capacitance current online measurement method and device of a secondary side bias capacitor of a grounding transformer, which can artificially change the asymmetry of a system, control and improve the voltage and current of a neutral point, overcome the problem that the traditional method can not accurately measure the single-phase grounding capacitance current of a power system with the neutral point grounded through an arc suppression coil when the symmetry of the system is good, improve the online measurement speed and precision of a power grid arc suppression coil grounding system, further reduce the probability of faults of a medium-voltage power grid due to bus grounding, are favorable for the stable and reliable operation of the power system, and solve the problems in the background technology.
In order to achieve the purpose, the invention is realized by the following technical scheme: grounding becomes capacitance current on-line measuring device of secondary side offset capacitance, including measurement and control device and Z type grounding transformer, still include solid state switch and offset capacitance, solid state switch and offset capacitance all are provided with threely, three solid state switch's output is connected with three offset capacitance's input respectively, and is three offset capacitance's output all grounds, Z type grounding transformer's secondary side is connected with three solid state switch.
Furthermore, the Z-type grounding transformer comprises a first coil, a second coil, a third coil, a fourth coil, a fifth coil, a sixth coil and a seventh coil, the Z-type grounding transformer is connected with an arc suppression coil, the input ends of the first coil, the second coil and the third coil are respectively connected with the UA end, the UB end and the UC end of the measurement and control device, the output end of the first coil is connected with the input end of the fourth coil, the output end of the second coil is connected with the input end of the fifth coil, the output end of the third coil is connected with the input end of the sixth coil, the output end of the seventh coil is grounded, the output ends of the fourth coil, the fifth coil and the sixth coil are all connected with the input end of the arc suppression coil, the output end of the arc suppression coil is grounded, the arc suppression coil is connected in parallel with the eighth coil, and the eighth coil is connected with the UO end of the measurement and control device, and the output end of the arc suppression coil is connected with a ninth coil in series, and the ninth coil 4 is connected with the AO end of the measurement and control device.
Furthermore, the first coil, the second coil and the third coil are correspondingly provided with three equivalent capacitors to the ground, and the three equivalent capacitors to the ground are a capacitor CA, a capacitor CB and a capacitor CC in sequence.
Further, the bias capacitor is a non-polar capacitor.
Further, the solid-state switch is a silicon controlled rectifier or an IGBT.
The method for measuring the capacitance current of the secondary side bias capacitor of the grounding transformer on line comprises the following steps:
and S1, three bias capacitors are connected between the three phases a, b and c of the secondary output of the Z-type grounding transformer and the ground through solid-state switches.
And S2, putting three bias capacitors in turn through a measurement and control device, and simultaneously measuring the voltage and the current of a neutral point and the bus voltage A, B, C to the ground.
And S3, calculating the system capacitance current value according to a formula derived theoretically, and taking the average value of the system capacitance current value.
Further, according to the operation step in S1, the configuration of three bias capacitors is 1-3% of the maximum compensation capacity of the system.
The invention provides a capacitance current on-line measuring method and device of a grounding transformer secondary side bias capacitor. The method has the following beneficial effects:
(1) the method can artificially change the asymmetry of the system, control and improve the voltage and the current of the neutral point, overcome the problem that the traditional method cannot accurately measure the single-phase grounding capacitance and the current of the power system with the neutral point grounded through the arc suppression coil because the voltage and the current of the neutral point are too low when the symmetry of the system is good, and improve the online measurement speed and the online measurement precision of the power grid arc suppression coil grounding system.
(2) The invention does not change the parameters of the arc suppression coil during measurement and does not influence the normal operation of the system. The method is an ideal measuring method suitable for various working conditions, is very beneficial to normal, reliable and stable operation of a power system, and reduces the probability of generating faults.
Drawings
FIG. 1 is a schematic diagram of a capacitance current on-line measuring device of a grounding transformer secondary side bias capacitor according to the present invention;
fig. 2 is a flowchart of the capacitance current on-line measurement method of the grounding transformer secondary side bias capacitor of the invention.
In the figure: 1. a measurement and control device; 2. a first coil; 3. a second coil; 4. a third coil; 5. a fifth coil; 6. a fifth coil; 7. a sixth coil; 8. an arc suppression coil; 9. a seventh coil; 10. a solid state switch; 11. a bias capacitor; 12. an eighth coil; 13. and a ninth coil.
Detailed Description
The invention will be further illustrated with reference to the following examples and drawings:
referring to fig. 1-2, the capacitance current on-line measuring device of the grounding transformer secondary side bias capacitor comprises a measuring and controlling device 1 and a Z-type grounding transformer, and further comprises three solid state switches 10 and three bias capacitors 11, wherein the three solid state switches 10 and the three bias capacitors 11 are respectively provided, the output ends of the three solid state switches 10 are respectively connected with the input ends of the three bias capacitors 11, the output ends of the three bias capacitors 11 are all grounded, the secondary side of the Z-type grounding transformer is connected with the three solid state switches 10, the arranged bias capacitors 11 can amplify, collect and calculate bias signals, the bias capacitors 11 are effectively controlled through the solid state switches 10 so as to realize the measurement of capacitance current, when in measurement, the asymmetry degree of the system can be manually changed, the control improves the neutral point voltage current, and overcomes the traditional method caused by the low neutral point voltage current when the symmetry degree of the system is good, the problem that the single-phase grounding capacitance current of a power system with a neutral point grounded through the arc suppression coil 8 cannot be accurately measured is solved, and the online measurement speed and accuracy of the power grid arc suppression coil 8 grounding system are improved.
Specifically, the Z-type grounding transformer includes a first coil 2, a second coil 3, a third coil 4, a fourth coil 5, a fifth coil 6, a sixth coil 7 and a seventh coil 9, the Z-type grounding transformer is connected with an arc suppression coil 8, input ends of the first coil 2, the second coil 3 and the third coil 4 are respectively connected with UA end, UB end and UC end of the measurement and control device 1, an output end of the first coil 2 is connected with an input end of the fourth coil 5, an output end of the second coil 3 is connected with an input end of the fifth coil 6, an output end of the third coil 4 is connected with an input end of the sixth coil 7, an output end of the seventh coil 9 is grounded, output ends of the fourth coil 5, the fifth coil 6 and the sixth coil 7 are all connected with an input end of the arc suppression coil 8, an output end of the arc suppression coil 8 is grounded, the arc suppression coil 8 is connected in parallel with an eighth coil 12, and the eighth coil 12 is connected with a UO end of the measurement and control device 1, the output end of the arc suppression coil 8 is connected with a ninth coil 13 in series, the ninth coil 13 is connected with the AO end of the measurement and control device 1, and the measurement and control device 1 is connected with the Z-shaped grounding transformer through a system PT.
Specifically, the bus system to which the input ends of the first coil 2, the second coil 3 and the third coil 4 are respectively connected has three equivalent capacitors to ground, and the three equivalent capacitors to ground are a capacitor CA, a capacitor CB and a capacitor CC in sequence.
Specifically, the bias capacitor 11 is a non-polar capacitor, and plays a role in amplifying, collecting and calculating a bias signal.
Specifically, the solid-state switch 10 is a thyristor or an IGBT, and has an effect of effectively and rapidly controlling the bias capacitor.
The method for measuring the capacitance current of the secondary side bias capacitor of the grounding transformer on line comprises the following steps:
step one, three bias capacitors 11 are connected between a three-phase a, a three-phase b and a three-phase c output by a Z-type grounding transformer and the ground through a solid-state switch 10, the three bias capacitors 11 are configured to be 1-3% of the maximum compensation capacity of a system, step two, the three bias capacitors 11 are put into a measurement and control device 1 in turn, the neutral point voltage and the current are measured at the same time, and A, B, C bus voltage to the ground is measured, step three, the system capacitor current value is calculated according to a formula deduced by theory, the average value of the system capacitor current value is taken, the system capacitor current can be calculated by switching one capacitor according to the theory, the three-phase measurement is taken to reduce the measurement error, the three-phase measurement is carried out to reduce the measurement error, the system capacitor current can
In order to make the three phases of the system to be grounded,
is a neutral point to ground voltage and,
is a neutral point to ground current. CA、CB、CCBeing three-phase capacitance to ground, 3C0＝CA+CB+CC，
ΔCA、ΔCB、ΔCCThe capacitance values are biased for each phase. When adding the bias capacitance value deltaC at aAThe formula of the measurement calculation basis is as follows:
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept of the present invention, and these changes and modifications are all within the scope of the present invention.
Claims (7)
1. The capacitance current on-line measuring device of the secondary side bias capacitor of the grounding transformer comprises a measuring and controlling device (1) and a Z-shaped grounding transformer, and is characterized in that: the transformer is characterized by further comprising three solid-state switches (10) and three bias capacitors (11), wherein the three solid-state switches (10) and the three bias capacitors (11) are arranged, the output ends of the three solid-state switches (10) are respectively connected with the input ends of the three bias capacitors (11), the output ends of the three bias capacitors (11) are all grounded, and the secondary side of the Z-shaped grounding transformer is connected with the three solid-state switches (10).
2. The on-line capacitance current measuring device of the secondary side bias capacitor of the grounding transformer as claimed in claim 1, wherein: the Z-type grounding transformer comprises a first coil (2), a second coil (3), a third coil (4), a fourth coil (5), a fifth coil (6), a sixth coil (7) and a seventh coil (9), the Z-type grounding transformer is connected with an arc suppression coil (8), the input ends of the first coil (2), the second coil (3) and the third coil (4) are respectively connected with UA ends, UB ends and UC ends of the measurement and control device (1), the output end of the first coil (2) is connected with the input end of the fourth coil (5), the output end of the second coil (3) is connected with the input end of the fifth coil (6), the output end of the third coil (4) is connected with the input end of the sixth coil (7), the output end of the seventh coil (9) is grounded, and the output ends of the fourth coil (5), the fifth coil (6) and the sixth coil (7) are connected with the input end of the arc suppression coil (8), the output of arc suppression coil (8) ground connection, arc suppression coil (8) parallel connection has eighth coil (12), and eighth coil (12) are connected with the UO end of measurement and control device (1), the output of arc suppression coil (8) is established ties and is had ninth coil (13), and the AO end of ninth coil (13) and measurement and control device (1) is connected.
3. The on-line capacitance current measuring device of the secondary side bias capacitor of the grounding transformer as claimed in claim 2, wherein: the first coil (2), the second coil (3) and the third coil (4) are correspondingly provided with three equivalent capacitors to the ground, and the three equivalent capacitors to the ground are a capacitor CA, a capacitor CB and a capacitor CC in sequence.
4. The on-line capacitance current measuring device of the secondary side bias capacitor of the grounding transformer as claimed in claim 1, wherein: the bias capacitor (11) is a non-polar capacitor.
5. The on-line capacitance current measuring device of the secondary side bias capacitor of the grounding transformer as claimed in claim 1, wherein: the solid-state switch (10) is a silicon controlled rectifier or an IGBT.
6. The method for measuring the capacitance current of the secondary side bias capacitor of the grounding transformer on line is characterized in that the device for measuring the capacitance current of the secondary side bias capacitor of the grounding transformer on line according to any one of claims 1 to 5 is used, and comprises the following steps:
s1, three bias capacitors (11) are connected between the a, b and c three phases of the secondary output of the Z-type grounding transformer and the ground through solid-state switches (10);
s2, putting three bias capacitors (11) in turn through the measurement and control device (1), and simultaneously measuring neutral point voltage and current and A, B, C bus voltage to the ground;
and S3, calculating the system capacitance current value according to a formula derived theoretically, and taking the average value of the system capacitance current value.
7. The capacitance current on-line measurement method of the secondary side bias capacitor of the grounding transformer as recited in claim 6, characterized in that the configuration of three bias capacitors (11) is 1-3% of the maximum compensation capacity of the system according to the operation step in S1.
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| CN114785365A (en) * | 2022-03-11 | 2022-07-22 | 复旦大学 | Capacitor-assisted three-coil transformer circuit |
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| CN113067318B (en) * | 2021-04-01 | 2022-05-31 | 河北旭辉电气股份有限公司 | Pre-adjusting phase-control arc extinction control method |
| CN114785365A (en) * | 2022-03-11 | 2022-07-22 | 复旦大学 | Capacitor-assisted three-coil transformer circuit |
| CN114785365B (en) * | 2022-03-11 | 2024-03-08 | 复旦大学 | Capacitor-assisted three-coil transformer circuit |
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