A kind of phase-shifting transformer differential protection implementation methodTechnical field
The present invention relates to a kind of implementation method of phase-shifting transformer differential protection, belong to electrical engineering Protection Technology neckDomain.
Background technology
In industrial circles such as aluminium electroloysis, alkali electrolysis, salt electrolysis, chemical industry, largely using rectification phase shifting transformer.Phase shift transformationUtensil has three below function:1. realize the phase offset of first and second side line voltage with harmonic carcellation；2. conversion is neededSecondary side voltage；3. the electrical isolation between rectifier and power network is realized.
The special function of phase-shifting transformer determines its special electrical structure, different from common transformer, phase shift transformationDevice secondary winding generally has multigroup.According to the difference of Phase shift winding, phase-shifting transformer can be divided into high-pressure side phase shift and low pressure sideswayPhase.When for high-pressure side phase shift, high pressure winding generally uses the extension triangle mode of connection or the figure of eight mode of connection, such as Fig. 1 institutesShow.When for low-pressure side phase shift, low pressure winding generally uses the extension triangle mode of connection, as shown in Figure 2.
Phase-shifting transformer is that the phase difference between multiwinding transformer, winding is different, and such as 36 pulse wave rectifier phase shifts becomeLow-pressure side phase shift phase is respectively -20, -10,0,10,20,30.Transformer differential protection needs to enter each side joint the phase of electric currentCompensate, indifference stream during ensuring that transformer is normally run has poor stream during internal fault.Conventional power transformer is usually wholeThe hour number mode of connection, such as Y0, △ -11 wiring, Y, △ -1 wiring are only needed during differential current computing by Y- △ phase transitions, i.e. and IA '=IA-IB, or IA '=IA-IC, B, C phase are by that analogy.And phase difference is not whole hour number between each winding of phase-shifting transformer(30 °), thus current phase compensate can not be realized by simple addition and subtraction, differential current computing is more complicated, it is necessary to which it is poor to redesignFlow calculation methodologies.
At present, consider in terms of construction condition, cost of investment and technical difficulty, phase-shifting transformer is generally onlyQuick-break excessively stream and protection are configured, differential protection is not installed.Because phase-shifting transformer low-pressure side winding is more, internal no-load voltage ratio is moreBecome, cause its impedance to be difficult calculating, therefore set-point is adjusted and made troubles.In addition, quick-break excessively stream can not reflect inside transformerThe failure such as high resistance ground in turn-to-turn short circuit, area, therefore the sensitivity of protection is relatively low.
The content of the invention
The purpose of the present invention is the defect for overcoming prior art to exist, and improves the sensitivity of phase-shifting transformer protection and reliableProperty, the present invention proposes a kind of phase-shifting transformer differential protection implementation method, goes for any wiring group, random phase differenceTransformer.
The present invention is adopted the following technical scheme that：A kind of phase-shifting transformer differential protection implementation method, it is characterised in that specificComprise the following steps：
Step SS1 gathers each side winding current of transformer in real time；
Each winding current conversion of low-pressure side is arrived high-pressure side by step SS2, is transferred to step SS3；
Step SS3 flows according to the Current calculation difference after conversion；
Step SS4 differentiates whether difference current is more than action threshold, if difference current is more than threshold, differential protection action is cutExcept transformer.
Preferably, each side winding current described in the step SS1 includes high pressure winding current iha、ihb、ihc, low pressure 1~N winding currents ilja、iljb、iljc, wherein j=1,2 Λ n.
Preferably, the step SS2 specifically includes following steps：If high-pressure side winding rated voltage is UhN, high-pressure side aroundGroup CT no-load voltage ratios are CTh, it is U that low-pressure side volume winding, which determines voltage,lN, low-pressure side winding CT no-load voltage ratios are CTl, low-pressure side winding and high-pressure sideWinding phases difference isAccording to the fundamental characteristics of transformer, have
Wherein
Based on any one phasor can by two orthogonal phasor representations, if：
In formulaFor high-pressure side winding A phase current phasors,For low-pressure side winding A, B phase current phasor；Due toThree-phase current is symmetrical, therefore has：
Association type (1)~(3), can be solved：
Formula (2) gives the equivalent relation of high-pressure side winding and low-pressure side winding current, that is to say low-pressure side winding electricityThe computational methods of high-pressure side winding current are arrived in stream conversion, i.e.,：
i′lja=kj1ilja+kj2iljb
i′ljb=kj1iljb+kj2iljc
i′ljc=kj1iljc+kj2ilja (6)
Wherein, formula (6) is high-pressure side winding current and low-pressure side winding current relational expression.
Preferably, the step SS3 specifically includes following steps：Formula (6) is equally applicable to the conversion of sampled value, after conversionBoth phases are consistent, and then directly carry out differential current computing, i.e.,：
ida=iha+i′la
idb=ihb+i′lc (7)
idc=ihc+i′la
Formula (7) is that phase shift angle isTwo-winding transformer differential current computing formula, being generalized to low-pressure side has nIndividual winding, and each arbitrary phase-shifting transformer of winding phase shift angle, then differential current computing formula be：
Wherein, iha、ihb、ihcFor high pressure winding current, ilja、iljb、iljcFor low pressure 1~n windings
Electric current, j=1,2 Λ n.
The beneficial effect that the present invention is reached：The present invention is applicable not only to conventional power transformer, and suitable for it is many aroundGroup, any wiring group, the phase-shifting transformer of random phase difference, with extremely strong versatility, solve current phase-shifting transformer(including rectifier transformer) because of poor stream is difficult to that calculating the present situation of differential protection can not be realized.
Brief description of the drawings
When Fig. 1 is high-pressure side phase shift, high pressure winding uses the signal of the extension triangle mode of connection or the figure of eight mode of connectionFigure.
When Fig. 2 is low-pressure side phase shift, low pressure winding generally uses the extension triangle mode of connection.
Fig. 3 is a kind of flow chart of the implementation method of phase-shifting transformer differential protection of the present invention.
Embodiment
The invention will be further described below in conjunction with the accompanying drawings.Following examples are only used for clearly illustrating the present inventionTechnical scheme, and can not be limited the scope of the invention with this.
Fig. 3 is a kind of flow chart of the implementation method of phase-shifting transformer differential protection of the present invention, and the present invention is using as followsTechnical scheme：A kind of phase-shifting transformer differential protection implementation method, it is characterised in that specifically include following steps：
Step SS1 gathers each side winding current of transformer in real time；Each side winding current described in the step SS1 includes heightPress winding current iha、ihb、ihc, low pressure 1~n winding currents ilja、iljb、 iljc, wherein j=1,2 Λ n；
Each winding current conversion of low-pressure side is arrived high-pressure side by step SS2, is transferred to step SS3；The step SS2 is specifically includedFollowing steps：If high-pressure side winding rated voltage is UhN, high-pressure side winding CT no-load voltage ratios are CTh, low-pressure side volume winding determines voltage and isUlN, low-pressure side winding CT no-load voltage ratios are CTl, low-pressure side winding is with high-pressure side winding phases differenceAccording to the substantially special of transformerProperty, have
Wherein
Based on any one phasor can by two orthogonal phasor representations, if：
In formulaFor high-pressure side winding A phase current phasors,For low-pressure side winding A, B phase current phasor；Due toThree-phase current is symmetrical, therefore has：
Association type (1)~(3), can be solved：
Formula (2) gives the equivalent relation of high-pressure side winding and low-pressure side winding current, that is to say low-pressure side winding electricityThe computational methods of high-pressure side winding current are arrived in stream conversion, i.e.,：
i′lja=kj1ilja+kj2iljb
i′ljb=kj1iljb+kj2iljc
i′ljc=kj1iljc+kj2ilja (6)
Wherein, formula (6) is high-pressure side winding current and low-pressure side winding current relational expression.
Step SS3 flows according to the Current calculation difference after conversion；The step SS3 specifically includes following steps：Formula (6) is sameSample is applied to the conversion of sampled value, and both phases are consistent after conversion, and then directly carry out differential current computing, i.e.,：
ida=iha+i′la
idb=ihb+i′lc (7)
idc=ihc+i′la
Formula (7) is that phase shift angle isTwo-winding transformer differential current computing formula, being generalized to low-pressure side has nIndividual winding, and each arbitrary phase-shifting transformer of winding phase shift angle, then differential current computing formula be：
Wherein, iha、ihb、ihcFor high pressure winding current, ilja、iljb、iljcFor low pressure 1~n windings
Electric current, j=1,2 Λ n.
Step SS4 differentiates whether difference current is more than action threshold, if difference current is more than threshold, differential protection action is cutExcept transformer.
Described above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the artFor member, without departing from the technical principles of the invention, some improvement and deformation can also be made, these improve and deformedAlso it should be regarded as protection scope of the present invention.