CN110579650B - Distribution transformer platform district low-voltage side three-phase real load warning and severe unbalance alarm system - Google Patents
Distribution transformer platform district low-voltage side three-phase real load warning and severe unbalance alarm system Download PDFInfo
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Abstract
The invention discloses a low-voltage side three-phase real load warning and severe unbalance warning system of a distribution transformer area, which comprises a three-phase load severe unbalance warning circuit and comprises: the three-phase open-delta residual voltage sampling circuit comprises three sampling coils arranged on a three-phase line, and a three-phase open-delta residual voltage acquisition device, a bridge shaping circuit, a filter circuit, a voltage stabilizing circuit and an alarm circuit which are sequentially connected; the three-phase real load warning circuit is connected with the three sampling hollow coils and comprises an A/D conversion circuit, a micro control unit MCU, a D/f conversion circuit, a frequency division counter and an LCD three-phase load current real-time display device, wherein the MCU, the D/f conversion circuit, the frequency division counter and the LCD three-phase load current real-time display device are sequentially connected. The system can be directly hung on a three-phase line, not only can send out an alarm of three-phase load unbalance in time, but also can display the specific line current value of the three-phase load in real time, adjust the load in time and avoid the occurrence or the expansion of accidents.
Description
Technical Field
The invention relates to transformer operation protection and low-voltage distribution line operation protection, in particular to a three-phase real load warning and severe unbalance warning system on a low-voltage side of a distribution transformer area.
Background
A large number of three-phase four-wire connection modes exist in cities and countryside of China, and the distribution transformer is in a Yyn0 connection mode, so that a large number of single-phase user loads exist, and actually, unbalanced operation of three-phase loads is inevitable. When three-phase load is not balanced, the transformer is burnt and serious accidents of distribution lines are caused very possibly.
The existing methods for solving the problem of three-phase load imbalance are classified into two categories:
one is manual regulation, which transfers part of the load to one or two other phases when one phase of the three-phase load with a large current is sensed or detected. The problems with this approach are: firstly, the unbalanced state of the three-phase load cannot be found in time, so that the dangerous state cannot be relieved in time; and secondly, even if the three phases are found to be unbalanced, the three phases cannot be adjusted to be basically balanced, because only the three-phase load imbalance can be known in a mode of monitoring the current of the zero line, but which phase of load is too large or too small cannot be known, and therefore adjustment is blind. The only advantage of this method is that there is no additional equipment cost, other than the current clamp meter.
Another type is an automatic adjustment system. For 1 distribution transformer platform district, need 1 total control terminal at least, need 6 ~ 12 commutation switches moreover at least. This system not only needs to configure the automatic phase change switch and its control terminal equipment, but also needs communication system between the phase change switch and its control terminal. The problems with this approach are: the system has the advantages of high cost, high installation and maintenance cost and the unique advantage of being capable of automatically adjusting the load, and is easy to influence the normal operation of a line, interfere the normal work of the power consumption information acquisition system and cause power failure accidents of users.
Disclosure of Invention
The invention aims to solve the technical problem of providing a three-phase real load warning and severe unbalance warning system for a low-voltage side of a distribution transformer area aiming at the defects in the prior art.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the utility model provides a distribution transformer platform district low-voltage side three-phase real load warning and heavy unbalance alarm system, includes three-phase load heavy unbalance alarm circuit all the way, includes: the three-phase open triangular residual voltage sampling device comprises three sampling hollow coils arranged on a three-phase line, and a three-phase open triangular residual voltage sampling device, a bridge shaping circuit, a filter circuit, a voltage stabilizing circuit and an alarm circuit which are sequentially connected;
the three sampling hollow coils respectively collect three alternating current induction line currents i on three phase linesu、iv、iwThen, according to the electromagnetic induction principle, three AC induced electromotive forces e are excitedu、ev、ewAfter passing through the open triangular residual voltage acquisition device, the three alternating current induced electromotive forces generate three alternating current induced voltages uu、uv、uwAnd obtaining a differential AC voltage u at the opening of the open triangular coilo＝uu+uv+uw；
The bridge shaping circuit and the filter circuit are used for converting the difference alternating voltage uoInto a differential DC voltage U0；
The voltage stabilizing circuit is a three-end adjustable integrated voltage stabilizing circuit, and the voltage stabilizing circuit further comprises an alarm threshold value for adjusting the three-phase load unbalance degree and a potentiometer R for adjusting the sound and light intensity of the alarmp；
The three-phase real load warning circuit is connected with the three sampling hollow coils and comprises an A/D conversion circuit, a micro control unit MCU, a D/f conversion circuit, a frequency division counter and an LCD three-phase load current real-time display device, wherein the MCU, the D/f conversion circuit, the frequency division counter and the LCD three-phase load current real-time display device are sequentially connected.
The micro control unit MCU is mainly used for executing logic management and control, and data signal operation and processing; the treatment process comprises the following steps:
three voltage signals u output by three acquisition hollow coilsu、uv、uwWith the line current i on the measured three-phase lineu、iv、iwRespectively linearly corresponding to three voltage signals uu、uv、uwPerforming numerical conversion (linear transformation) to obtain line current i on the measured three-phase lineu、iv、iwThe current value of (a);
calculating formula i according to zero line currentn＝iu+iv+iwReal-time calculation of zero line current inThe phases of the highest load phase, the middle load phase and the lowest load phase and the corresponding current values thereof are distinguished in real time through the current values of the three induction lines, and the zero line and the current values thereof are distinguished; simultaneously, carrying out signal marking on the currents of the highest load phase and the zero line;
and sending the current data I to a D/f conversion circuit.
According to the scheme, the sampling coil is an open-close type Rogowski coil.
According to the scheme, the open triangle residual voltage acquisition device comprises three induction coils with the same polarity end in sequence.
According to the scheme, the shaping circuit comprises a full-wave bridge shaping circuit consisting of 4 shaping diodes D1, D2, D3 and D4.
According to the scheme, the voltage stabilizing circuit is a three-terminal adjustable CW78M (LM317) integrated voltage stabilizing circuit.
According to the scheme, the adjustable integrated voltage stabilizing circuit comprises an adjustable potentiometer RP。
According to the scheme, the alarm circuit comprises a microswitch S and an intelligent audible and visual alarm RL。
It should be noted that: the MCU micro control unit outputs a digital signal, the digital signal outputs a frequency signal after passing through the D/f converter, the frequency signal is subjected to frequency division processing and counting by the frequency division counter and then is transmitted to the LCD display, the LCD display is driven to display, and the data marked by the signal is subjected to highlighting processing including thickening/highlighting/flickering.
The invention has the following beneficial effects:
1. non-magnetic wire carcass complianceDesigned open-close type Rogowski hollow acquisition (without ferromagnetic material) coil RU and RV、RWAnd an ultra-long induction voltage information transmission cable LU、LV、LWIs suitable for any narrow place and long-distance hanging.
2. A three-phase open type triangular residual voltage acquisition device delta U is used for skillfully acquiring a required signal driving difference value direct current voltage Uo of a subsequent circuit.
3. The debugging is not needed in the operation, before leaving a factory, the acousto-optic alarm threshold is debugged and verified by regulating the three-terminal (output voltage/alarm threshold) adjustable integrator CW78M (LM317) and the potentiometer Rp in the voltage stabilizing circuit thereof according to the regulations;
and 4, the signal acquired by the Rogowski acquisition coil is the line current of a three-phase line, and the output induced electromotive force or induced voltage overcomes the technical obstacles of inconvenient acquisition and processing and the like caused by the current output of a current transformer.
5. Only if the unbalanced degree of the three-phase load exceeds a specified value, namely the heavy unbalance is reported to the police through the audible and visual alarm RL, related personnel can be reminded to transfer the load according to the displayed load current value, and even the device can be turned off through the switch S, so that the audible and visual interference is avoided.
6. The alarm device is not required to be installed, namely, the alarm device can be used after being hung, the placing position or the placing space is not limited, and the installation wiring and the operation and maintenance cost are avoided;
7. and the unbalanced state of the three-phase load is immediately and visually found, the highest load phase, the middle load, the lowest load and the zero line current in the three phases are simultaneously and visually displayed in real time, and key values of the highest load, the zero line current and the like are highlighted.
8. The system can call historical data, is convenient for researching the load change trend and meets the power demand side management.
9. The system works independently, does not affect the work of any equipment or system on a line, and further does not cause power failure accidents.
10. The invention has simple design principle, abandons complex comparison circuit, amplifying circuit, modulation-demodulation circuit, complex communication system and expensive remote control mode, only needs one alarm in one transformer area, is safe and stable and has low cost.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a schematic structural diagram of an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, a distribution transformer platform district low-voltage side three-phase real load warning and heavy unbalance alarm system, including three-phase load heavy unbalance alarm circuit all the way, includes: the three-phase open triangular residual voltage sampling device comprises three sampling hollow coils arranged on a three-phase line, and a three-phase open triangular residual voltage sampling device, a bridge shaping circuit, a filter circuit, a voltage stabilizing circuit and an alarm circuit which are sequentially connected;
three sampling hollow coils which are hung on a three-phase line are open-close type flexibly-processed coreless Rogowski hollow coils, and the other ends of the three sampling hollow coils are connected with a three-phase open triangular residual voltage acquisition device through an ultra-long voltage signal transmission cable;
the three sampling hollow coils respectively collect three alternating current induction line currents i on three phase linesu、iv、iwThen, according to the electromagnetic induction principle, three AC induced electromotive forces e are excitedu、ev、ewAfter passing through the open triangular residual voltage acquisition device, the three alternating current induced electromotive forces generate three alternating current induced voltages uu、uv、uwAnd obtaining a differential AC voltage u at the opening of the open triangular coilo＝uu+uv+uw；
Bridge shaping circuit and filter circuit for converting the difference AC voltage uoInto a differential DC voltage U0；
The voltage stabilizing circuit is a CW78 with three-terminal adjustableThe M (LM317) integrated voltage stabilizing circuit also comprises an alarm threshold value for adjusting the three-phase load unbalance degree and a potentiometer R for adjusting the sound and light intensity of an alarmp；
The three-phase real load warning circuit is connected with the three sampling coils and comprises an A/D conversion circuit, a micro control unit MCU (microprogrammed control unit), a D/f conversion circuit, a frequency division counter and an LCD (liquid crystal display) three-phase load current real-time display device which are sequentially connected, wherein the MCU, the D/f conversion circuit, the frequency division counter and the LCD three-phase load current real-time display device are used for internal logic control and data processing of the warning circuit; the frequency division counter comprises a frequency divider and a counter; the display device is a 12864 serial mode liquid crystal display with alternate display of three-phase line current and memory function.
And the micro control unit MCU is mainly used for executing logic management and control, and data signal operation and processing.
The MCU processing procedure is as follows:
three voltage signals u output by three acquisition hollow coilsu、uv、uwWith the line current i on the measured three-phase lineu、iv、iwRespectively linearly corresponding to three voltage signals uu、uv、uwPerforming numerical conversion (linear transformation) to obtain line current i on the measured three-phase lineu、iv、iwThe current value of (a);
calculating formula i according to zero line currentn＝iu+iv+iwReal-time calculation of zero line current inThe phases of the highest load phase, the middle load phase and the lowest load phase and the corresponding current values thereof are distinguished in real time through the current values of the three induction lines, and the zero line and the current values thereof are distinguished; simultaneously, carrying out signal marking on the currents of the highest load phase and the zero line;
and sending the current data I to a D/f conversion circuit.
The MCU micro control unit outputs a digital signal, the digital signal outputs a frequency signal after passing through the D/f converter, the frequency signal is subjected to frequency division processing and counting by the frequency division counter and then is transmitted to the LCD display, the LCD display is driven to display, and the data marked by the signal is subjected to highlighting processing including thickening/highlighting/flickering.
It will be understood that modifications and variations can be made by persons skilled in the art in light of the above teachings and all such modifications and variations are intended to be included within the scope of the invention as defined in the appended claims.
Claims (10)
1. The utility model provides a distribution transformer platform district low-voltage side three-phase real load warning and heavy unbalance alarm system which characterized in that, includes three-phase load heavy unbalance alarm circuit all the way, includes: the three-phase open triangular residual voltage sampling device comprises three sampling hollow coils arranged on a three-phase line, and a three-phase open triangular residual voltage sampling device, a bridge shaping circuit, a filter circuit, a voltage stabilizing circuit and an alarm circuit which are sequentially connected;
the three sampling hollow coils are used for respectively collecting three alternating current induction line currents i on three phase linesu、iv、iwThen, according to the electromagnetic induction principle, three AC induced electromotive forces e are excitedu、ev、ewAnd generates three AC induction voltages uu、uv、uw；
The open-delta residual voltage acquisition device is used for generating three alternating-current induced voltages u according to three alternating-current induced electromotive forcesu、uv、uwObtaining a differential AC voltage u at the opening of the open triangular coiloWherein u iso＝uu+uv+uw；
The bridge shaping circuit and the filter circuit are used for converting the difference alternating voltage uoInto a differential DC voltage U0；
The voltage stabilizing circuit is a three-end adjustable integrated voltage stabilizing circuit, and the voltage stabilizing circuit further comprises an alarm threshold value for adjusting the three-phase load unbalance degree and a potentiometer R for adjusting the sound and light intensity of the alarmp；
The system also comprises a three-phase real load warning circuit, wherein the three-phase real load warning circuit is connected with the three sampling hollow coils and comprises an A/D conversion circuit, a micro control unit MCU (microprogrammed control unit), a D/f conversion circuit, a frequency division counter and an LCD (liquid crystal display) three-phase load current real-time display device which are sequentially connected, and the MCU, the D/f conversion circuit, the frequency division counter and the LCD are used for logic control and data processing in the warning circuit.
2. The distribution transformer area low-voltage side three-phase real load warning and severe unbalance alarm system according to claim 1, wherein the Micro Control Unit (MCU) is mainly used for executing logic management and control, data signal operation and processing; the treatment process comprises the following steps:
three voltage signals u output by three acquisition hollow coilsu、uv、uwWith the line current i on the measured three-phase lineu、iv、iwRespectively linearly corresponding to three voltage signals uu、uv、uwCarrying out numerical linear transformation to obtain the line current i on the measured three-phase lineu、iv、iwThe current value of (a);
calculating formula i according to zero line currentn＝iu+iv+iwReal-time calculation of zero line current inThe phases of the highest load phase, the middle load phase and the lowest load phase and the corresponding current values thereof are distinguished in real time through the current values of the three induction lines, and the zero line and the current values thereof are distinguished; simultaneously, carrying out signal marking on the currents of the highest load phase and the zero line;
and sending the current data I to a D/f conversion circuit.
3. The distribution transformer area low-voltage side three-phase real load warning and severe unbalance alarm system according to claim 1, wherein the sampling hollow coil is an open-close type rogowski coil.
4. The distribution transformer area low-voltage side three-phase real load warning and severe unbalance alarm system according to claim 1, wherein the open triangle residual voltage collecting device comprises three induction coils with like polarity ends connected in series.
5. The distribution transformer bay low-voltage side three-phase real load warning and heavy unbalance alarm system as claimed in claim 1, wherein the shaping circuit comprises a full-wave bridge shaping circuit consisting of 4 shaping diodes D1, D2, D3 and D4.
6. The distribution transformer platform area low-voltage side three-phase real load warning and severe unbalance alarming system as claimed in claim 1, wherein the voltage stabilizing circuit is a three-terminal adjustable CW78M (LM317) integrated voltage stabilizing circuit.
7. The distribution transformer area low-voltage side three-phase real load warning and severe unbalance alarm system as claimed in claim 1, wherein the adjustable integrated voltage-stabilizing circuit comprises an adjustable potentiometer RP。
8. The distribution transformer area low-voltage side three-phase real load warning and severe unbalance alarm system as claimed in claim 1, wherein the alarm circuit comprises a microswitch S and an intelligent audible and visual alarm RL。
9. The distribution transformer area low-voltage side three-phase real load warning and severe unbalance alarm system as claimed in claim 1, wherein the frequency division counter is used for performing frequency division processing and counting on the frequency signal output after the D/f converter.
10. The low-voltage side three-phase real load warning and severe unbalance alarm system of the distribution transformer area according to claim 1, wherein the LCD three-phase load current real-time display device is used for displaying the calculation result of the frequency division counter and highlighting/flickering the data containing the signal mark.
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1023658A (en) * | 1996-07-02 | 1998-01-23 | Nichicon Corp | Fault-detecting device for three-phase capacitor |
| CN102435869A (en) * | 2011-08-26 | 2012-05-02 | 东北大学 | Experimental device for automatic regulation and compensation of three-phase unbalanced load and control method thereof |
| CN105137207A (en) * | 2015-09-25 | 2015-12-09 | 国网山东省电力公司济南供电公司 | Three-phase power supply load unbalancing alarming device |
| CN206461372U (en) * | 2017-02-21 | 2017-09-01 | 浙江亿德科技有限公司 | Power distribution station three-phase load unbalance automatic regulating system |
| CN207968067U (en) * | 2018-04-12 | 2018-10-12 | 江苏佳源科技有限公司 | A kind of CT for fault detector power supply is for electric installation |
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- 2019-07-19 CN CN201910657330.0A patent/CN110579650B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH1023658A (en) * | 1996-07-02 | 1998-01-23 | Nichicon Corp | Fault-detecting device for three-phase capacitor |
| CN102435869A (en) * | 2011-08-26 | 2012-05-02 | 东北大学 | Experimental device for automatic regulation and compensation of three-phase unbalanced load and control method thereof |
| CN105137207A (en) * | 2015-09-25 | 2015-12-09 | 国网山东省电力公司济南供电公司 | Three-phase power supply load unbalancing alarming device |
| CN206461372U (en) * | 2017-02-21 | 2017-09-01 | 浙江亿德科技有限公司 | Power distribution station three-phase load unbalance automatic regulating system |
| CN207968067U (en) * | 2018-04-12 | 2018-10-12 | 江苏佳源科技有限公司 | A kind of CT for fault detector power supply is for electric installation |
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