CN102135561A - Measuring device and method for zero-sequence current of non-effectively neutral grounded system - Google Patents
Measuring device and method for zero-sequence current of non-effectively neutral grounded system Download PDFInfo
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Abstract
The invention relates to a measuring device and method for the zero-sequence current of a non-effectively neutral grounded system. In the invention, a measuring device and measuring method for a single-phase ground fault wire selection device of the non-effectively neutral grounded system is improved, and the sensibility and the accuracy for measuring the zero-sequence current are enhanced. The output of a zero-sequence current transformer is connected in series with a resistor R2 which is connected in parallel with a primary coil of a small-sized voltage transformer; the output of a secondary coil of the small-sized voltage transformer is connected in series with a resistor R3; one end of the resistor R3 is grounded, and the other end of the resistor R3 is connected with one input end of a computing circuit; the output of the computing circuit is connected with a proportional amplifier II and a proportional amplifier III; the proportional amplifier II and the proportional amplifier III are connected with a microcomputer system after being respectively connected with an A/D (Analog/Digital) conversion circuit; the microcomputer system is connected with a D/A (Digital/Analog) conversion circuit; the output of the D/A conversion circuit is connected with a proportional amplifier I; and the output of the proportional amplifier I is connected with the other input end of the computing circuit.
Description
Technical field
The present invention relates to field of relay protection in power, particularly a kind of system with non-effectively earthed neutral zero sequence current measurement device and method.
Background technology
During the electric system single phase ground fault of power transformer isolated neutral, do not have short-circuit loop, can not produce short-circuit current, relay protection of power system can trip, and electric system allows to continue operation a period of time.But single-phase earthing also is harmful to electric system.Therefore, during this system single phase ground fault, relay protection must be sent alerting signal, and the operator on duty makes respective handling by operation, at last faulty line is carried out interruption maintenance.For faulty line is carried out interruption maintenance, relay protection should be sent alerting signal and be pointed out faulty line.Relay protection judges whether single phase ground fault is easy to realize.But the capacity current during the isolated neutral system single phase ground fault is less, and it is just very difficult to judge which bar line failure.So far the performance factor of single-phase grounding selecting device is very low both at home and abroad.
Way commonly used is that the fault amount of utilizing electric system self to produce detected when singlephase earth fault took place.Group's amplitude ratio that each bar circuit zero sequence current amplitude size of comparison is arranged is than principle; Each other faciation comparison principle of bar circuit zero sequence current and phase difference of comparison is arranged; Group's width of cloth faciation comparison principle that both combinations are also arranged.Because the capacity current during the electric system generation singlephase earth fault of isolated neutral changes with the variation of the system architecture and the method for operation, sometimes very big, sometimes very little, add current transformer TA error, the influence of factors such as single-phase grounding selecting error in measure, under a lot of situations, be difficult to judge faulty line.
Be to solve the low problem of performance factor of single-phase grounding selecting device, application for a patent for invention number is that 931113091 patent of invention has proposed a kind of method of AC signal that adds.Application for a patent for invention number is that 2004100240158 patent of invention has proposed a kind of small grounding current system fault line selection method for single-phase-to-ground fault.These methods need the external signal power supply, use inconvenience, and device performance does not still meet the demands.
When singlephase earth fault took place, the principle that the fault amount of utilizing electric system self to produce detects was reliable, and subject matter is that measured zero-sequence current is very little, and the measurement device error is big, causes the performance factor of single-phase grounding selecting device very low.
Summary of the invention
Purpose of the present invention is exactly in order to address the above problem, a kind of system with non-effectively earthed neutral zero sequence current measurement device and method is provided, it improves sensitivity and the precision of measuring zero-sequence current by improving the measurement links and the measuring method of system with non-effectively earthed neutral single-phase earth fault line selection device.
For achieving the above object, the present invention adopts following technical scheme:
A kind of system with non-effectively earthed neutral zero sequence current measurement device, it comprises:
Small-sized voltage transformer (VT) TV, its first siding ring input voltage amount, secondary side resistance in series R3, resistance R 3 one end ground connection, an input end of other end concatenation operation circuit; The output terminal of computing circuit is connected with at least one proportional amplifier, and proportional amplifier then is connected with corresponding A/D analog to digital conversion circuit, and the A/D analog to digital conversion circuit is connected with microsystem;
Microsystem, its output terminal are by at least one D/A D/A converting circuit, and the D/A D/A converting circuit is connected with corresponding ratio amplifying circuit, and this ratio amplification circuit output end connects another input end of computing circuit.
The voltage of the first siding ring input of described small-sized voltage transformer (VT) TV is the voltage at resistance R 2 two ends, resistance R 2 is connected on the secondary side of primary system zero sequence current mutual inductor, resistance R 2 voltage dependent resistor (VDR) R1 in parallel, capacitor C 1, resistance R 2 are obtained and the proportional voltage of primary system zero-sequence current.
Described resistance R 3 shunt capacitance C2.
The output terminal of described computing circuit is connected with ratio amplifying circuit II, ratio amplifying circuit III respectively, and ratio amplifying circuit II, ratio amplifying circuit III are connected with A/D analog to digital conversion circuit II with corresponding A/D analog to digital conversion circuit I respectively.
Described D/A D/A converting circuit is connected with ratio amplifying circuit I, and ratio amplifying circuit I output is connected with another input end of computing circuit.
A kind of method of work that adopts system with non-effectively earthed neutral zero sequence current measurement device, its process is:
When electric system normally moves, system with non-effectively earthed neutral zero sequence current measurement device begins to put into operation, the voltage at resistance R 2 two ends that is connected on the output of zero sequence current mutual inductor is connected to the small-sized voltage transformer (VT) TV first siding ring of device, the both end voltage U1 that is connected on the resistance R 3 of small-sized voltage transformer (VT) TV second siding ring imports one of them input terminal of computing circuit, the output voltage of computing circuit obtains the U1 digital signal through proportional amplifier II and A/D analog to digital conversion circuit I, and the input microsystem;
Microsystem is handled the video digital signal Un that the back forms U1 to the U1 digital signal, microsystem is exported to the D/A D/A converting circuit to Un, output of D/A D/A converting circuit and the corresponding simulating signal of digital signal Un, this simulating signal is through another input terminal of proportional amplifier I input computing circuit, computing circuit carries out computing to the signal of two input ends, and it is zero that operation result makes computing circuit output voltage U 3;
If U3 does not reduce to zero, microsystem is proceeded to handle to the U1 digital signal, forms the new video digital signal Un of U1, and microsystem is exported to the D/A D/A converting circuit to new Un; So repeatedly, reach minimum value until U3; The one section periodic digital signal of Un when microsystem reaches minimum value to U3 deposits microsystem long storer storage time in as memory signal Um;
Microsystem is no longer got U1 voltage waveform digital signal from A/D analog to digital conversion circuit I after obtaining memory signal Um; But memory signal Um is exported to the D/A D/A converting circuit periodically; And get U1 voltage waveform digital signal from A/D analog to digital conversion circuit II;
Electric system generation singlephase earth fault, the U1 voltage waveform digital signal that microsystem is obtained from A/D analog to digital conversion circuit II be measurement device to transmission line of electricity the capacitive zero-sequence current.
The invention has the beneficial effects as follows: the capacitive zero-sequence current just obtains amplifying in first link of metering circuit; Various stable state undesired signals just obtain eliminating at device body foremost; Device body can amplify useful zero sequence current signal as far as possible, and fault line selection device is greatly improved to the measurement sensitivity and the precision of zero-sequence current, guarantees that fault line selection device makes correct selection.
Description of drawings
Fig. 1 represents a kind of system with non-effectively earthed neutral zero sequence current measurement device logic diagram;
Wherein, 1. microsystem, 2. ratio amplifying circuit I, 3. ratio amplifying circuit II, 4. ratio amplifying circuit III, 5. D/A D/A converting circuit, 6. A/D analog to digital conversion circuit I, 7. A/D analog to digital conversion circuit II, 8. computing circuit.
Embodiment
The present invention will be further described below in conjunction with accompanying drawing.
A kind of system with non-effectively earthed neutral zero sequence current measurement device as shown in Figure 1.Resistance R 2 of output terminal series connection of zero sequence current mutual inductor is to obtain and the proportional voltage of zero-sequence current.The zero sequence current mutual inductor of fault line selection device in the past output be the zero-sequence current that has reduced according to the zero sequence current mutual inductor no-load voltage ratio, the capacitive zero-sequence current is original just very little in the primary system, through current transformer ratio, it is littler that Current Transformer Secondary is surveyed zero-sequence current.Current Transformer Secondary side zero-sequence current is given another small current mutual inductor of fault line selection device then, and zero-sequence current is through another small current mutual inductor ratio of fault line selection device, and small current mutual inductor secondary side zero-sequence current reduces again.Resistance of small current mutual inductor secondary side series connection, to obtain and the proportional voltage of zero-sequence current, this residual voltage is less.Very little zero-sequence current is easy to be disturbed by the small current mutual inductor exciting current of the exciting current of zero sequence current mutual inductor and fault line selection device in conversion, zero-sequence current information even buried by the exciting current of two current transformers.
The present invention is in resistance R 2 of output series connection of the zero sequence current mutual inductor of primary system, and very little zero-sequence current can obtain bigger residual voltage value, and the capacitive zero-sequence current just obtains amplifying in first link of metering circuit.The bigger residual voltage value in resistance R 2 two ends is not easy disturbed in transmission course, can do not buried by the small current mutual inductor exciting current of the exciting current of zero sequence current mutual inductor and fault line selection device, therefore, device is greatly improved to the measurement sensitivity and the precision of zero-sequence current.
No matter the transmission line of electricity of power transformer isolated neutral is normal operation, phase fault still takes place, all there is not zero-sequence current.Zero sequence current mutual inductor secondary side open circuit high voltage can not occur, and particularly the primary side three-phase conducting wire passes the cable zero sequence current mutual inductor of annular core, and the secondary side open circuit high voltage can not occur.If the zero sequence current mutual inductor (as shown in Figure 1) of threephase current transformer TAa, TAb, the addition of TAc secondary side, because the imbalance of threephase current transformer sum of errors environment will have uneven zero-sequence current; Zero sequence current mutual inductor secondary side open circuit will produce very big superpotential.In order to reduce the influence of uneven zero-sequence current, resistance R 2 of zero sequence current mutual inductor output series connection; And when uneven zero-sequence current was big, resistance R 2 got the small value; Uneven zero-sequence current hour, resistance R 2 is got big value; Neither produce superpotential, can obtain big residual voltage value again.In order to prevent that high frequency interference from producing superpotential at resistance R 2 two ends, resistance R 2 voltage dependent resistor (VDR) R1 in parallel, voltage are during less than setting, and voltage dependent resistor (VDR) R1 is very big; Voltage is during greater than setting, and voltage dependent resistor (VDR) R1 is very little, and superpotential is by voltage dependent resistor (VDR) R1 discharge, protection secondary circuit equipment.Resistance R 2 capacitor C 1 in parallel, small-sized voltage transformer (VT) TV secondary coil capacitor C 2 in parallel, capacitor C 1, C2 are anti-interference capacitor; Reduce of the influence of transient state impulse disturbances to the measurement device circuit.
When electric system normally moved, system with non-effectively earthed neutral zero sequence current measurement device began to put into operation, and at this moment transmitting loop does not have zero-sequence current, and resistance R 2 two ends are uneven residual voltage.The voltage at resistance R 2 two ends is connected to the small-sized voltage transformer (VT) TV primary winding of device through cable, small-sized voltage transformer (VT) TV secondary coil resistance in series R3, the both end voltage U1 input ratio of resistance R 3 adds (subtracting) computing circuit 8, the output voltage U 3 that ratio adds (subtracting) computing circuit 8 obtains the U1 digital signal through proportional amplifier II3 and A/D analog to digital conversion circuit I6, and input microsystem 1; The voltage signal of microsystem 1 control A/D analog to digital conversion circuit I6 Comparative Examples amplifier II3 output is sampled and analog to digital conversion, and the U1 simulating signal becomes the storer that deposits microsystem 1 behind the digital quantity in.
1 pair of U1 digital signal of microsystem is handled, form the video digital signal Un of U1, then the Un digital signal is exported to D/A D/A converting circuit 5, D/A D/A converting circuit 5 is converted to simulating signal to the Un digital signal, this analog output signal is through proportional amplifier I2 output U2 voltage signal (for example: the U2 waveform voltage signal is opposite with the U1 voltage waveform), and input adds (subtracting) computing circuit 8, (for example: addition), making U3 is zero through adding 8 computings of (subtracting) computing circuit for U2 voltage and U1 voltage.As seen, the target that 1 pair of U1 digital signal of microsystem is handled the video digital signal Un that forms U1 is that to make U3 be zero, or as far as possible little.1 pair of U1 digital signal of microsystem is handled the fairly simple disposal route of the video digital signal Un that forms U1, is to the U1 negate; Be the negate of U1 positive voltage ripple, as Un negative voltage ripple; The negate of U1 negative voltage ripple is as Un positive voltage ripple.Another easily disposal route be, 1 of microsystem is handled the power frequency sinusoidal signal in the U1 digital signal, the target that forms the video digital signal Un of U1 is that to make the power frequency sinusoidal signal among the U3 be zero, or as far as possible little.Non-power frequency sinusoidal signal in the U1 digital signal is handled by other analog filters or digital filter.Microsystem 1 makes U3 more little, and needed disposal route is complicated more.So the performance index of device need be weighed processing with the processing complexity.
If U3 does not reduce to zero, 1 pair of U1 digital signal of microsystem is proceeded to handle, and forms the new video digital signal Un of U1, and microsystem 1 is exported to D/A D/A converting circuit 5 to new Un; So repeatedly, reach minimum value until U3; The one section periodic digital signal of Un when microsystem 1 reaches minimum value to U3 deposits microsystem long storer storage time in as memory voltage signal Um;
Electric system generation singlephase earth fault, the U1 voltage waveform signal that obtains from the A/D analog to digital conversion circuit II7 that is connected with proportional amplifier III4 be measurement device to transmission line of electricity capacitive zero-sequence current waveform; Microsystem 1 is obtained the zero-sequence current of all transmission lines of electricity that are connected with bus, judges faulty line in view of the above.
When electric system normally moved, the U1 voltage waveform signal that the A/D analog to digital conversion circuit II7 that connects from proportional amplifier III4 obtains was very little, is the stable state undesired signal.During electric system generation singlephase earth fault, transmission line of electricity has zero-sequence current; The A/D analog to digital conversion circuit II7 that connects from proportional amplifier III4 can obtain zero-sequence current information.If it is less to obtain zero-sequence current information from A/D analog to digital conversion circuit II7, the enlargement factor that can strengthen proportional amplifier III4 improves the measurement sensitivity and the precision of device.Because the stable state undesired signal is reduced, the enlargement factor of proportional amplifier III4 can be bigger.Thereby improve measurement sensitivity and the precision of device to zero-sequence current.
The stable state undesired signal may change along with the change of power system operation mode, memory voltage signal Um in the microsystem 1 can upgrade automatically according to the Fixed Time Interval of design, the zero-sequence current situation of change adaptive updates that measures before also can taking place according to the electric system single-line to ground fault.Before taking place, the electric system single-line to ground fault makes the interference minimum of stable state undesired signal to device; Device can obtain big as far as possible zero sequence current measurement sensitivity and precision so that the back takes place the electric system single-line to ground fault.
A kind of system with non-effectively earthed neutral zero sequence current measurement device logic diagram that Fig. 1 represents is only measured a transmission line of electricity zero-sequence current; One cover system with non-effectively earthed neutral fault line selection device need be measured many transmission line of electricity zero-sequence currents, so, need the measurement mechanism that many covers Fig. 1 represents be made up, can realize the failure line selection task.
System with non-effectively earthed neutral zero sequence current measurement device and method of the present invention can manufacture and design with prior art, can realize fully.Broad prospect of application is arranged.
Claims (6)
1. system with non-effectively earthed neutral zero sequence current measurement device is characterized in that it comprises:
Small-sized voltage transformer (VT) TV, its first siding ring input voltage amount, secondary side resistance in series R3, resistance R 3 one end ground connection, an input end of other end concatenation operation circuit; The output terminal of computing circuit is connected with at least one proportional amplifier, and proportional amplifier then is connected with corresponding A/D analog to digital conversion circuit, and the A/D analog to digital conversion circuit is connected with microsystem;
Microsystem, its output terminal are by at least one D/A D/A converting circuit, and the D/A D/A converting circuit is connected with corresponding ratio amplifying circuit, and this ratio amplification circuit output end connects another input end of computing circuit.
2. system with non-effectively earthed neutral zero sequence current measurement device as claimed in claim 1, it is characterized in that, the voltage of the first siding ring input of described small-sized voltage transformer (VT) TV is the voltage at resistance R 2 two ends, resistance R 2 is connected on the secondary side of primary system zero sequence current mutual inductor, resistance R 2 voltage dependent resistor (VDR) R1 in parallel, capacitor C 1, resistance R 2 are obtained and the proportional voltage of primary system zero-sequence current.
3. system with non-effectively earthed neutral zero sequence current measurement device as claimed in claim 1 is characterized in that, described resistance R 3 shunt capacitance C2.
4. system with non-effectively earthed neutral zero sequence current measurement device as claimed in claim 1, it is characterized in that, the output terminal of described computing circuit is connected with ratio amplifying circuit II, ratio amplifying circuit III respectively, and ratio amplifying circuit II, ratio amplifying circuit III are connected with A/D analog to digital conversion circuit II with corresponding A/D analog to digital conversion circuit I respectively.
5. system with non-effectively earthed neutral zero sequence current measurement device as claimed in claim 1 is characterized in that, described D/A D/A converting circuit is connected with ratio amplifying circuit I, and ratio amplifying circuit I output is connected with another input end of computing circuit.
6. method of work that adopts the described system with non-effectively earthed neutral zero sequence current measurement of claim 1 device is characterized in that its process is:
When electric system normally moves, system with non-effectively earthed neutral zero sequence current measurement device begins to put into operation, the voltage at resistance R 2 two ends that is connected on the output of zero sequence current mutual inductor is connected to the small-sized voltage transformer (VT) TV first siding ring of device, the both end voltage U1 that is connected on the resistance R 3 of small-sized voltage transformer (VT) TV second siding ring imports one of them input terminal of computing circuit, the output voltage of computing circuit obtains the U1 digital signal through proportional amplifier II and A/D analog to digital conversion circuit I, and the input microsystem;
Microsystem is handled the video digital signal Un that the back forms U1 to the U1 digital signal, microsystem is exported to the D/A D/A converting circuit to Un, output of D/A D/A converting circuit and the corresponding simulating signal of digital signal Un, this simulating signal is through another input terminal of proportional amplifier I input computing circuit, computing circuit carries out computing to the signal of two input ends, and operation result makes that to add (subtracting) computing circuit output voltage U 3 be zero;
If U3 does not reduce to zero, microsystem is proceeded to handle to the U1 digital signal, forms the new video digital signal Un of U1, and microsystem is exported to the D/A D/A converting circuit to new Un; So repeatedly, reach minimum value until U3; The one section periodic digital signal of Un when microsystem reaches minimum value to U3 deposits microsystem long storer storage time in as memory signal Um;
Microsystem is no longer got U1 voltage waveform digital signal from A/D analog to digital conversion circuit I after obtaining memory signal Um; But memory signal Um is exported to the D/A D/A converting circuit periodically; And get U1 voltage waveform digital signal from A/D analog to digital conversion circuit II;
Electric system generation singlephase earth fault, the U1 voltage waveform digital signal that microsystem is obtained from A/D analog to digital conversion circuit II be measurement device to transmission line of electricity the capacitive zero-sequence current.
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103308766A (en) * | 2013-05-15 | 2013-09-18 | 湖南大学 | Harmonic analysis method based on Kaiser self-convolution window dual-spectrum line interpolation FFT (Fast Fourier Transform) and device thereof |
| CN103323647A (en) * | 2013-06-07 | 2013-09-25 | 国家电网公司 | Device and method for monitoring classified insulation electromagnetic type PT primary side current |
| CN103560514A (en) * | 2013-09-23 | 2014-02-05 | 株洲变流技术国家工程研究中心有限公司 | Reactive power compensation and harmonic treatment system |
| CN104111370A (en) * | 2014-06-30 | 2014-10-22 | 陕西和硕电气有限公司 | Method for measuring zero-sequence current in three-phase ungrounded system |
| CN106093709A (en) * | 2016-08-15 | 2016-11-09 | 国网山东省电力公司潍坊供电公司 | A kind of Single-phase Earth-fault Selection in Distribution Systems differential based on broad sense and localization method |
| CN108693430A (en) * | 2018-04-13 | 2018-10-23 | 苏州工业园区海沃科技有限公司 | A kind of segmented distribution network capacitance current test measuring circuit and its measurement method |
| CN110058071A (en) * | 2019-04-30 | 2019-07-26 | 上海固缘电力科技有限公司 | Zero sequence current sensor circuit topology and switch pole |
| CN116500328A (en) * | 2023-06-06 | 2023-07-28 | 无锡市锡山湖光电器有限公司 | High-precision three-phase current sensor |
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Cited By (10)
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| CN103308766A (en) * | 2013-05-15 | 2013-09-18 | 湖南大学 | Harmonic analysis method based on Kaiser self-convolution window dual-spectrum line interpolation FFT (Fast Fourier Transform) and device thereof |
| CN103323647A (en) * | 2013-06-07 | 2013-09-25 | 国家电网公司 | Device and method for monitoring classified insulation electromagnetic type PT primary side current |
| CN103560514A (en) * | 2013-09-23 | 2014-02-05 | 株洲变流技术国家工程研究中心有限公司 | Reactive power compensation and harmonic treatment system |
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| CN106093709A (en) * | 2016-08-15 | 2016-11-09 | 国网山东省电力公司潍坊供电公司 | A kind of Single-phase Earth-fault Selection in Distribution Systems differential based on broad sense and localization method |
| CN106093709B (en) * | 2016-08-15 | 2019-04-09 | 国网山东省电力公司潍坊供电公司 | A kind of Single-phase Earth-fault Selection in Distribution Systems and localization method differential based on broad sense |
| CN108693430A (en) * | 2018-04-13 | 2018-10-23 | 苏州工业园区海沃科技有限公司 | A kind of segmented distribution network capacitance current test measuring circuit and its measurement method |
| CN108693430B (en) * | 2018-04-13 | 2023-09-15 | 苏州工业园区海沃科技有限公司 | Sectional distribution network capacitance current measuring circuit and measuring method thereof |
| CN110058071A (en) * | 2019-04-30 | 2019-07-26 | 上海固缘电力科技有限公司 | Zero sequence current sensor circuit topology and switch pole |
| CN116500328A (en) * | 2023-06-06 | 2023-07-28 | 无锡市锡山湖光电器有限公司 | High-precision three-phase current sensor |
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