CN101207273B - Method for inhibiting voltage transformer noise caused by DC magnetic biasing - Google Patents
Method for inhibiting voltage transformer noise caused by DC magnetic biasing Download PDFInfo
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- CN101207273B CN101207273B CN2007101704416A CN200710170441A CN101207273B CN 101207273 B CN101207273 B CN 101207273B CN 2007101704416 A CN2007101704416 A CN 2007101704416A CN 200710170441 A CN200710170441 A CN 200710170441A CN 101207273 B CN101207273 B CN 101207273B
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Abstract
The invention relates to a method of restricting the direct current magnetic bias to generate the noise of the transformer, which belongs to the emergency protection circuit device field. The invention comprises a stopping direct unit and a primary system fault protection unit, the invention is characterized in that two electrolytic capacitances with polarities are connected in series in an inverted polarity way, and a diode is in parallel connected at the both ends of each electrolytic capacitance in a reverted polarity way, so as to form a stopping direct unit; at least more than two diodes are connected in series in sequence in an identical direction way, so as to form an unidirectional overvoltage protection circuit, and two unidirectional overvoltage protection circuits are connected in parallel in a reverse direction way, so as to form a complete primary system fault protective unit. The continuity of the grounding circuit is guaranteed during the changing process of the grounding current at the whole central point from small to large, the complex controlling circuit and the thyristor element are avoided, no risk of the stopping direct component is guaranteed by a built-in auto bypass, the structure parameter of the prior electric network is not changed, and simultaneously, the direct current component can be completely partitioned during the normal operation.
Description
Technical field
The invention belongs to emergency protective circuit device field, relate in particular to a kind of emergency protective circuit device that is used to suppress the transformer neutral point direct current.
Background technology
Along with the construction of China's electrical network, increasing DC power transmission line (also being called high voltage direct current transmission) puts into operation, has played very positive effect in regional interconnection of power system.
When DC transmission system one pole the earth operation (also being called asymmetric operation), the face of land can produce DC voltage difference, and same result also may be caused (as dc electrolysis etc.) by DC earthing in the industrial production.
Because the DC potential difference of the earth, when the transformer of transmission line two ends all adopts the mode of neutral ground, the earth direct current differential pressure produces D.C. magnetic biasing by neutral ground to transformer, produce magnetic biasing after the AC transformer neutral point stack DC component, cause magnetic saturation, in AC system, produce harmonic wave, vibration, noise, had a strong impact on the safe and stable operation of AC system.The tangible consequence of wherein bringing is that transformer noise increases greatly, and through measuring, the mean value of transformer noise is greater than 75 decibels, when serious even up to 90 decibels.
Because transformer is generally very near from the residential block in the urban distribution network now, the increase greatly of transformer noise often causes very big social concern, produces many adverse effects.
Simultaneously, the existence of D.C. magnetic biasing phenomenon also makes the loss of transformer self obviously increase, and is unfavorable for efficiency of transmission energy-saving and cost-reducing and the raising transmission line.
Domestic have research to the DC source that produces in the 220KV transformer neutral point ground connection operational mode more, carried out many theory analysises and on-the-spot actual measurement.Because 220KV transformer station span is longer relatively, relatively large at the direct current epd that then long distance produces, therefore constitute DC loop easily.The potential difference maximum that shows 220KV transformer station neutral ground two ends according to more domestic test report data can reach between 40V～50V, and maximum direct current can reach about 30A.
In order effectively to reduce direct current, some local employings mode such as series resistor or electric capacity in the neutral ground loop solves the transformer bias that direct current causes both at home and abroad;
2 units of the subordinate of Quebec, CAN power office, electric power research institute IREQ and TransEnergie company played joint research and development in 1993 and suppress the neutral point direct current current device, and it is used for limiting HVDC (High Voltage Direct Current) transmission system flows into AC network when adopting the earth echo plex mode direct current.Its operation principle is to insert little capacitive reactance at transformer neutral point, when the system failure with its bypass.
Domestic have " the principle emulation of transformer DC magnetic bias " to study, and analyzes imperial certainly mechanism that transformer bears the external forced direct current, and having illustrated direct current one pole earth current is the source of D.C. magnetic biasing, has proposed to alleviate some operation measures of transformer vibration.
Concluding from practical application gets up to have following three kinds of modes to solve DC component:
1) at transformer neutral point dress small resistor, with the size of restriction direct current.
2) series capacitor on transformer neutral point, blocking-up direct current, failure condition are used the thyristor bypass down.
3) inject the DC potential that the counter current method is offset transformer neutral point at the transformer periphery, to reduce neutral point direct current.
The said method solution cuts both ways, and first method simply should be gone, but not thorough, effect is relevant with epd, if epd is bigger, earth resistance is subjected to system's restriction to be had in the time of should not increasing, and effect is just poor.Second method is a kind of method that suppresses more completely, but because the use in the controls such as triggering of thyristor protection loop has brought decline and some uncertain factors of reliability.Feasible on the third theoretical method, the practical application more complicated is difficult to accomplish ideal state, moreover the direct current that injects has brought other problem again.
Summary of the invention
Technical problem to be solved by this invention provides a kind of method that suppresses voltage transformer noise caused by DC magnetic biasing, it is in the ascending change procedure of whole centre-point earth electric current, guaranteed the continuity of grounded circuit every the reliable nonlinear characteristic of straight assembly, complicated control loop and thyristor components and parts have been avoided, built-in auto by pass guarantees every perfectly safe every straight assembly directly, do not change the network system structural parameters, when normal operation, DC component thoroughly can be cut off again simultaneously.
Technical scheme of the present invention is: a kind of method that suppresses voltage transformer noise caused by DC magnetic biasing is provided; be included in be provided with between transformer neutral point and the earth electrode in parallel every straight unit and primary system error protection unit; it is characterized in that: with two electrochemical capacitor reversed polarity serial connections that polarity is arranged; two ends at each electrochemical capacitor; in the reversed polarity mode and connect a diode; in protection electric capacity; eliminate because two effects that the equal whole total capacitance that capacitances in series caused of capacitance reduces by half; utilize the nonlinear resistance property of diode, constitute one complete have communication channel every straight unit.
Simultaneously; with the series connection successively in the same way of plural at least diode, utilize the reverse breakdown characteristics of diode, constitute a unidirectional overvoltage protection loop; with two unidirectional overvoltage protection loop reverse parallel connections, constitute a complete primary system error protection unit.
Above-mentioned is the capacitive characteristic every straight unit under nominal situation, be the capacitance-resistance characteristic when neutral point current increases, and breaking down at primary system is resistance characteristic when causing current surge, and ignores state along with its resistance value of increase of fault current sharply drops to.
Above-mentioned primary system error protection unit automatic short-circuit under the extreme case of reverse breakdown directly will be every straight unit short circuit excision, makes the direct ground connection of transformer neutral point.
Concrete; comprise first electrochemical capacitor, second electrochemical capacitor, the first protection diode and the second protection diode every straight unit; wherein; first and second electrochemical capacitor reversed polarity serial connection; positive and negative electrode two ends at first and second electrochemical capacitors; respectively with the reversed polarity mode and connect first and second the protection diodes, electrochemical capacitor after the serial connection and corresponding protection diode thereof are connected between transformer neutral point and the earth electrode.
Primary system error protection unit comprises the first and second unidirectional overvoltage protection loops of two reverse parallel connections; The positive pole of the 1st diode in the described first unidirectional overvoltage protection loop is connected with transformer neutral point, and the negative pole of n diode is connected with earth electrode; The negative pole of the 1st diode in the described second unidirectional overvoltage protection loop is connected with transformer neutral point, and the positive pole of n diode is connected with earth electrode.
Further, between described transformer neutral point and earth electrode, also a by-pass switch can be set, be used for described out of service, with the neutral-point solid ground of transformer every straight unit and/or primary system error protection unit.
Stating between any one unidirectional overvoltage protection loop and the earth electrode, an overcurrent actuation coil is set, the output signal of overcurrent actuation coil is used to start the closed ON Action of described by-pass switch.
Compared with the prior art, advantage of the present invention is:
1. in electric capacity two ends reversed polarity and connect diode, utilize the characteristic of diode nonlinear area, operational mode and failure condition have been taken into account, rationally be provided with breakover point, neither influence has the system parameters of protective relaying device now, can not change the various operating modes of original primary system again, also reach the goal of the invention that reduces transformer noise;
2. with two polarity electrochemical capacitor reversed polarity serial connection is arranged, again and connect the composition mode of pair of diodes, the Capacity Ratio tradition connection of electric capacity is doubled, and the volume that exchanges big electric capacity can be significantly reduced, and also can ensure the safety in operation of electrochemical capacitor simultaneously;
3. utilize the series circuit of a plurality of device for high-power power electronic diodes to constitute the primary system faulty channel, circuit structure is succinct, has avoided complicated control loop and thyristor components and parts, can reduce its manufacturing/use cost and maintenance workload greatly;
4. the pressure drop of diode series connection is greater than face of land voltage difference, so will have only very little leakage current to flow through under the normal condition, element does not almost have caloric value, compole is short under failure condition because during short circuit current, and electric current is subjected to the restriction of transformer short-circuit impedance and the effect of by-pass switch, so need not diode is carried out radiating treatment, also help dwindling the volume of whole device;
5. this device is not owing to there is control loop, and circuit structure is simple, the maintenance issues that do not exist in service.Selected components and parts are power electronic device commonly used, stable performance, and the reliability height is not even if certain components and parts generation problem in service can produce serious consequence yet.
Description of drawings
Fig. 1 is an equivalent electric circuit topological diagram of the present invention;
Fig. 2 is the electrical block diagram of the present invention every straight unit.
Embodiment
The present invention will be further described below in conjunction with accompanying drawing.
Among Fig. 1; present invention resides in be provided with between transformer neutral point O (or O ') and the earth electrode Q (or Q ') in parallel every straight unit 1 (or 1 ') and primary system error protection unit 2 (or 2 '); its innovation and creation point is; with two electrochemical capacitor reversed polarity serial connections that polarity is arranged; two ends at each electrochemical capacitor; in the reversed polarity mode and connect a diode (concrete connected mode see Fig. 2); the capacity that capacitances in series such as elimination causes in the protection electric capacity effect that reduces by half; utilize the nonlinear resistance property of diode, constitute one complete have good communication channel every straight unit 1 (or 1 ').
In other words; it comprises first electrochemical capacitor, second electrochemical capacitor, the first protection diode and the second protection diode every straight unit; its first and second electrochemical capacitors reversed polarity serial connection; positive and negative electrode two ends at first and second electrochemical capacitors; respectively with the reversed polarity mode and connect first and second the protection diodes; electrochemical capacitor after the serial connection and corresponding protection diode thereof are connected between transformer neutral point and the earth electrode, constitute one complete every straight unit.
Be the capacitive characteristic every straight unit under nominal situation, be the capacitance-resistance characteristic when neutral point current increases, breaking down at primary system is resistance characteristic when causing current surge, and can ignore state along with its resistance value of increase of fault current sharply drops to.
In addition; second innovation and creation point of the present invention is; with the series connection successively in the same way of plural at least diode; utilize the reverse breakdown characteristics of diode; constitute unidirectional overvoltage protection loop 2-1, a 2-2 (or 2-1 ', 2-2 '); with two unidirectional overvoltage protection loop reverse parallel connections, constitute a complete primary system error protection unit 2 (or 2 ').
As seen from the figure; its primary system error protection unit comprises the first unidirectional overvoltage protection loop 2-1 (or 2-1 ') and the second unidirectional overvoltage protection loop 2-2 (or 2-2 ') of two reverse parallel connections; each unidirectional overvoltage protection loop comprises n (n 〉=2) diode; each diode is series connection successively in the same way; behind the first and second unidirectional overvoltage protection loop reverse parallel connections; be connected between transformer neutral point and the earth electrode, constitute a complete primary system error protection unit 2 (or 2 ').
The positive pole of the 1st diode in the first unidirectional overvoltage protection loop is connected with transformer neutral point, and the negative pole of n diode is connected with earth electrode; The negative pole of the 1st diode in the second unidirectional overvoltage protection loop is connected with transformer neutral point, and the positive pole of n diode is connected with earth electrode.
The automatic short-circuit under the extreme case of reverse breakdown of primary system error protection unit directly will be every straight unit short circuit excision, makes the direct ground connection of transformer neutral point.
Between described transformer neutral point and earth electrode, a by-pass switch 4 (or 4 ') also can be set, be used for making it out of service, with the neutral-point solid ground of transformer with every straight unit and/or the excision of primary system error protection unit.
Further, in order to obtain better effect, also can be in unidirectional overvoltage protection loop, a certain road (among the figure be example with 2-2) serial connection one overcurrent actuation coil, the output signal of overcurrent actuation coil is used to start the closed ON Action of described by-pass switch.Be example with the second unidirectional overvoltage protection loop 2-2 among the figure, between the positive pole and earth electrode of n the diode in the described second unidirectional overvoltage protection loop, be provided with overcurrent actuation coil 2-3 (or 2-3 ').
Adopt technique scheme, in the ascending change procedure of whole centre-point earth electric current, guaranteed the continuity of grounded circuit every the reliable nonlinear characteristic of straight assembly, complicated control loop and thyristor components and parts have been avoided, built-in auto by pass guarantees every perfectly safe every straight assembly directly, do not change the structural parameters of existing network system, when normal operation, DC component thoroughly can be cut off again simultaneously.
During real work:
1. the earth direct current I
ZProduce voltage drop (peak of testing this voltage according to reality can reach between 40V～50V) above the electric resistance of soil Z between two transformer centre-point earth;
2. centre-point earth two terminal voltages at resistance Z constitute the loop by transformer centre-point earth line and overhead wire, make transformer produce magnetic bias;
3. grounded circuit series connection electric power heavy-duty diode, utilize the nonlinear resistance principle of diode, with the reasonable constituent components that cooperates of capacitor, little electric current passes through electric capacity, big electric current constitutes the good result that extremely simple isolated DC electric current guarantees communication channel by diode; Simultaneously, because heavy-duty diode bears the advantage of big current work characteristic in short-term, the component element long period reliability of operation is high.
In case short circuit current is by neutral ground, in short-term, pass through diode circuit, (4～10mS) directly just with neutral-point solid ground, even if grounding shunt neutral point short circuit current is all by diode circuit, to device also not influence for the intrinsic closing time of process by-pass switch.
Among Fig. 2; with two electrochemical capacitor C1 and C2 reversed polarity serial connections that polarity is arranged; two ends at each electrochemical capacitor; in the reversed polarity mode and meet a diode D1 and D2; utilize the nonlinear resistance property of diode; in protection electric capacity, eliminate because the effects that the whole total capacitance that capacitances in series caused that two capacitances equate reduces by half, constituted one complete have good communication channel every straight unit.
As seen from the figure, the positive and negative electrode of first and second electrochemical capacitors respectively with first and second the protection diodes negative, positive extremely corresponding connection.
Because the nonlinear resistance property of diode, under nominal situation, be the capacitive characteristic every straight unit, when increasing, neutral point current is the capacitance-resistance characteristic, breaking down at primary system is resistance characteristic when causing current surge, and can ignore state along with its resistance value of increase of fault current sharply drops to.
To sum up, this device does not generate heat owing in service, the electric capacity miniaturization, and whole volume is very little, is no more than 1 cube volume, can be placed near the transformer nearby, so long as the transformer noise that D.C. magnetic biasing causes all can use this this method to carry out the elimination of noise.
Be noted that enumerating of above-mentioned execution mode, only be to understand technical scheme of the present invention better, and should do not regard qualification as technical solution of the present invention in order to help.
Those of ordinary skill in the art; after understanding and having grasped innovation intention of the present invention and mentality of designing; need not through creative work; fully can be on the basis of technique scheme of the present invention; derive various that be equal to or have the deformation program of identical function, and these deformation programs also should belong to the scope that the present invention asks for protection.
The present invention can be widely used in electric power system power transmission and transformation field.
Claims (7)
1. method that suppresses voltage transformer noise caused by DC magnetic biasing is included in and is provided with in parallelly every straight unit and primary system error protection unit between transformer neutral point and the earth electrode, it is characterized in that:
With two electrochemical capacitor reversed polarity serial connections that polarity is arranged, two ends at each electrochemical capacitor, in the reversed polarity mode and connect a diode, in protection electric capacity, eliminate because two effects that the equal whole total capacitance that capacitances in series caused of capacitance reduces by half, utilize the nonlinear resistance property of diode, constitute one complete have communication channel every straight unit;
With the series connection successively in the same way of plural at least diode, utilize the reverse breakdown characteristics of diode, constitute a unidirectional overvoltage protection loop, with two unidirectional overvoltage protection loop reverse parallel connections, constitute a complete primary system error protection unit.
2. according to the method for the described inhibition voltage transformer noise caused by DC magnetic biasing of claim 1, it is characterized in that describedly under nominal situation, being the capacitive characteristic every straight unit, when increasing, neutral point current is the capacitance-resistance characteristic, breaking down at primary system is resistance characteristic when causing current surge, and can ignore state along with its resistance value of increase of fault current sharply drops to.
3. according to the method for the described inhibition voltage transformer noise caused by DC magnetic biasing of claim 1; it is characterized in that the automatic short-circuit under the extreme case of reverse breakdown of described primary system error protection unit; directly will be every straight unit short circuit excision, make the direct ground connection of transformer neutral point.
4. according to the method for the described inhibition voltage transformer noise caused by DC magnetic biasing of claim 1; it is characterized in that describedly comprising first electrochemical capacitor, second electrochemical capacitor, the first protection diode and the second protection diode every straight unit; wherein; first and second electrochemical capacitor reversed polarity serial connection; positive and negative electrode two ends at first and second electrochemical capacitors; respectively with the reversed polarity mode and connect first and second the protection diodes; electrochemical capacitor after the serial connection and corresponding protection diode thereof are connected between transformer neutral point and the earth electrode.
5. according to the method for the described inhibition voltage transformer noise caused by DC magnetic biasing of claim 1, it is characterized in that described primary system error protection unit comprises the first and second unidirectional overvoltage protection loops of two reverse parallel connections; The positive pole of the 1st diode in the described first unidirectional overvoltage protection loop is connected with transformer neutral point, and the negative pole of n diode is connected with earth electrode; The negative pole of the 1st diode in the described second unidirectional overvoltage protection loop is connected with transformer neutral point, and the positive pole of n diode is connected with earth electrode.
6. according to the method for the described inhibition voltage transformer noise caused by DC magnetic biasing of claim 1; it is characterized in that between described transformer neutral point and earth electrode; one by-pass switch is set; be used for described out of service, with the neutral-point solid ground of transformer every straight unit and/or primary system error protection unit.
7. according to the method for the described inhibition voltage transformer noise caused by DC magnetic biasing of claim 6; it is characterized in that between described any one unidirectional overvoltage protection loop and earth electrode; one overcurrent actuation coil is set, and the output signal of overcurrent actuation coil is used to start the closed ON Action of described by-pass switch.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2007101704416A CN101207273B (en) | 2007-11-15 | 2007-11-15 | Method for inhibiting voltage transformer noise caused by DC magnetic biasing |
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| CN2007101704416A CN101207273B (en) | 2007-11-15 | 2007-11-15 | Method for inhibiting voltage transformer noise caused by DC magnetic biasing |
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| CN101207273A CN101207273A (en) | 2008-06-25 |
| CN101207273B true CN101207273B (en) | 2011-04-20 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US8878396B2 (en) * | 2010-07-20 | 2014-11-04 | Emprimus, Llc | Continuous uninterruptable AC grounding system for power system protection |
| CN102832607A (en) * | 2011-06-15 | 2012-12-19 | 西门子公司 | Quick bypass device |
| CN104374990B (en) * | 2014-12-02 | 2017-11-28 | 国家电网公司 | A kind of system and method for carrying out ground potential difference monitoring |
| CN105826848B (en) * | 2016-04-25 | 2018-03-27 | 国核电力规划设计研究院 | Power station grounded screen |
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