CN104459578A - Residual magnetism estimation method for Yyn0-type three-phase combined transformer non-fault tripping - Google Patents
Residual magnetism estimation method for Yyn0-type three-phase combined transformer non-fault tripping Download PDFInfo
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Abstract
The invention discloses a residual magnetism estimation method for Yyn0-type three-phase combined transformer non-fault tripping. The method includes the steps of firstly, sampling the voltage and current waveform of a Yyn0-type three-phase combined transformer through a signal collecting device by means of a mutual inductor to obtain the voltage and current instantaneous value, obtaining plural forms of all electrical quantities through the Fourier algorithm, and then obtaining the power factor angle and the iron core steady-state flux peak; secondly, determining the primary open phase and the primary open phase drop-out voltage phase angle according to the sampled three-phase current waveform; thirdly, estimating the three-phase iron core residual magnetism according to the voltage change situation of a winding in the opening process and the relation between the voltage change situation and the iron core flux. By means of the method, only the three-phase voltage and current waveform needs to be sampled when the Yyn0-type three-phase combined transformer runs, the power factor angle and the iron core steady-state flux peak during steady-state running can be obtained through data processing, then the iron core residual magnetism can be estimated according to the power factor angle and the iron core steady-state flux peak, related parameters are easy to obtain, and the residual magnetism estimation method can be conveniently used for actual engineering estimation.
Description
Technical field
The invention belongs to transformer remanent magnetism method of estimation technical field, be specifically related to the remanent magnetism method of estimation of a kind of Yyn0 type three-phase group formula transformer non-faulting tripping operation.
Background technology
Yyn0 type three-phase group formula transformer is made up of three single transformers, and iron core builds up primarily of siliconized plate, the star-like connection of former vice-side winding and secondary neutral ground.Because each phase magnetic flux closes along respective magnetic circuit, therefore its magnetic circuit system has nothing to do each other, and in supply frequency and umber of turn one timing, each phase iron core magnetic flux determines (ignoring coil resistance and leakage flux) by winding impressed voltage.
Because siliconized plate belongs to ferromagnetic material, there is hysteresis, after transformer separating brake, external magnetic field is cancelled, and ferromagnetics still can keep original part magnetic, and make transformer fe in-core leave part magnetic flux, this magnetic flux is called iron core remanent magnetism.Therefore can be similar to and to think after transformer separating brake that remanent magnetism over time and not obvious, remanent magnetism is approximately equal to separating brake moment iron core magnetic flux.Former limit three-phase current equal and opposite in direction when Yyn0 type three-phase group formula transformer normally runs in three-phase symmetrical system, phase place mutual deviation 120 °, due to the nature disjunction when current over-zero of each phase isolating switch, therefore three-phase separating brake moment non-synchronous, this process will cause the change of winding impressed voltage, and then affects iron core remanent magnetism.And when transformer during no-load closing, because core material excitation property has nonlinear characteristic, affect by iron core remanent magnetism and breaker closing phase angle, the saturated of iron core may be caused, transformer is caused to produce very large exciting current in the side of voltage jump, maximum 6 ~ 8 times of reaching rated current of its numerical value, this electric current is just called the excitation surge current of transformer.Due to excitation surge current amplitude very greatly and only flow through transformer side, by causing Differential Protection of Transformer to produce very large difference stream, causing differential protection misoperation trip, making putting into operation time and again unsuccessfully of transformer; The excitation surge current that numerical value is very large also can cause transformer and isolating switch because of electric power excessive and impaired; Excitation surge current also may bring out transformer that other transformer station contiguous etc. running and produce " sympathetic inrush " and mistrip, causes large-area power-cuts; A large amount of harmonic waves wherein also can cause serious pollution to the electrical network quality of power supply.
Phase selection technology be a kind of novel electric power apparatus proposed along with the development of switching technique close means, it suppresses the principle of excitation surge current to be select suitable switching-on phase according to the remanent magnetism in separating brake back core, control isolating switch dynamic/static contact to carry out switch in the designated phase angle moment of system voltage or current waveform and close, what when making combined floodgate, remanent magnetism and magnetic bias can be similar to cancels out each other, thus avoid the supersaturation of transformer core magnetic flux, fundamentally reach the object weakening excitation surge current.
The existing multiple traditional counting model about remanent magnetism or magnetic field comprises Product model, Preisach model, Stoner-Wohlfarth model, but above Model Calculating Method all relates to the parameter that part is not directly measured, and utilize the requirement of software emulation transformer remanent magnetism to compare accurate simulation to system works behavior, model buildings is comparatively complicated, therefore practicality is all little in the concrete estimation of transformer core remanent magnetism.
Summary of the invention
In order to solve above-mentioned prior art Problems existing, the invention provides the remanent magnetism method of estimation of a kind of Yyn0 type three-phase group formula transformer non-faulting tripping operation, the method only need be sampled Yyn0 type three-phase group formula transformer three-phase voltage current waveform when running, by the power-factor angle under data processing acquisition steady-state operation and iron core stable state magnetic flux peak value, iron core remanent magnetism can be estimated accordingly, correlation parameter easily obtains, in can estimating for Practical Project easily.
In order to achieve the above object, the present invention adopts following technical scheme:
The remanent magnetism method of estimation of Yyn0 type three-phase group formula transformer non-faulting tripping operation, comprises the steps:
When step 1:Yyn0 type three-phase group formula transformer runs, signal pickup assembly is sampled by the voltage current waveform of mutual inductor to Yyn0 type three-phase group formula transformer, obtains electric current and voltage instantaneous value;
Step 2: obtain Yyn0 type three-phase group formula transformer stable state three-phase voltage, electric current plural form by fourier algorithm, obtains power-factor angle
and iron core stable state magnetic flux peak value φ
m, described iron core stable state magnetic flux peak value
wherein: U
mrepresent phase voltage amplitude, N represents umber of turn, and ω is system angle frequency;
Step 3: the three-phase current waveform of acquisition of sampling according to step 1, determines the first mutually disconnected and first phase drop-out voltage phase angle that breaks
or
described head breaks the phase referring to mutually and first disconnect, namely when first the electric current of certain phase is reduced to zero and remain unchanged, then and disconnected phase headed by this phase;
Step 4: estimation tri-phase iron core remanent magnetism
Suppose that first breaking is A phase mutually, and first disconnected phase voltage phase angle is δ, known according to formula (7), A phase cut-offs moment tri-phase iron core magnetic flux φ
a, φ
b, φ
cshown in (8);
A phase disconnects rear three-phase windings voltage u
a'X, u
bY, u
cZshown in (9), three-phase current i
a, i
b, i
cshown in (10), according to the law of electromagnetic induction, the three-phase produced by this voltage responds to magnetic flux φ in advance
ay, φ
by, φ
cyfor formula (11);
According to continuity of magnetic flux theorem, A phase disconnects moment magnetic flux and cannot suddenly change, and leads to φ by producing such as formula the three-phase magnetic bias shown in (12)
ap, φ
bp, φ
cpto offset the pre-induction magnetic flux in this moment;
Therefore after A phase disconnects, tri-phase iron core magnetic flux is (8), (11), (12) formula sum, and abbreviation is such as formula shown in (13);
According to formula (10), B, C phase will the electric current simultaneously zero passage nature disjunction when delayed A phase 90 ° of electrical angles; Bring ω t=δ+90 ° into formula (13), tri-phase iron core remanent magnetism φ can be obtained
ar, φ
br, φ
crfor formula (14);
Because three-phase system has symmetry, therefore disconnected phase time headed by B, C phase, first mutually disconnected and another two-phase flux change rule is identical with above-mentioned situation, can obtain first disconnected phase remanent magnetism expression formula accordingly, shown in (15);
φ
sd＝φ
msin(δ-90°) (15)
During normal operation, the phase remanent magnetism of the advanced first disconnected phase 120 ° of voltage-phase is formula (16);
Normal when running the voltage-phase delayed head phase remanent magnetism of 120 ° mutually that breaks be formula (17);
Compared to the prior art comparatively, the present invention possesses following advantage:
1, correlation parameter easily obtains.Namely all parameters of this remanent magnetism method of estimation are all by directly measuring or indirect calculation acquisition.
2., compared to software emulation Yyn0 type three-phase group formula transformer remanent magnetism, without the need to building complicated system model, the convenient engineering that is used for is estimated.
Accompanying drawing explanation
Fig. 1 is voltage-current relationship figure.
Fig. 2 is Yyn0 type three-phase group formula transformer Connecting groups schematic diagram.
Fig. 3 is realistic model equivalent circuit diagram.
Fig. 4 is for estimating magnetic flux and emulation flux waveforms comparison diagram.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail:
When transformer runs, signal pickup assembly carries out sampling by the voltage current waveform of mutual inductor to Yyn0 type three-phase group formula transformer and obtains electric current and voltage instantaneous value, obtains stable state three-phase voltage plural form by fourier algorithm
, and electric current plural form
, such as formula (1), (2).Wherein U
mrepresent phase voltage amplitude, α represents A phase voltage phase angle, I
mrepresent line current amplitude, β represents A phase current phase angle, and power-factor angle is each phase voltage and current phase angle difference, therefore
If A phase voltage phase angle α=0 °, stable state three-phase voltage time-domain expression u can be obtained by (1), (2)
a(t), u
b(t), u
c(t), and electric current time-domain expression i
a(t), i
b(t), i
c(t), such as formula (3), (4).
Wherein ω is system angle frequency.
Because transformer primary side is Y connection, therefore during normal operation, each phase winding voltage is phase voltage, shown in (5).
According to Faraday's electromagnetic induction law,
Wherein u represents winding voltage, and φ represents iron core magnetic flux, and N represents umber of turn.
Then tri-phase iron core magnetic flux φ
a, φ
b, φ
ccan be expressed as
Wherein iron core stable state magnetic flux peak value is
In Fig. 1, u represents former limit phase voltage, and i represents phase current, and because isolating switch during separating brake will the nature disjunction when current over-zero, therefore first disconnected phase voltage phase angle is
or
Suppose that first breaking is A phase mutually, and
in time, cut-offs, known according to formula (7), and A phase cut-offs moment tri-phase iron core magnetic flux such as formula shown in (8).Cut-off rear electric parameters to analyze with symmetrical component method.For Yyn0 type group formula three-phase transformer, as shown in Figure 2, its former limit does not have zero-sequence current path, therefore can think that positive sequence impedance is approximately equal to negative sequence impedance in sequence net, zero sequence impedance is infinitely great, A phase can be obtained accordingly and cut-off rear three-phase windings voltage, electric current, shown in (9), (10).
According to the law of electromagnetic induction, the three-phase being cut-off the generation of rear three-phase windings voltage by A phase responds to magnetic flux φ in advance
ay, φ
by, φ
cyfor formula (11);
According to continuity of magnetic flux theorem, this moment magnetic flux cannot suddenly change, and passes to the pre-induction magnetic flux of offsetting this moment by producing such as formula the magnetic bias shown in (12).
Therefore after A phase disconnects, tri-phase iron core magnetic flux is (8), (11), (12) formula sum, and abbreviation is such as formula shown in (13).
According to formula (10), B, C phase will the electric current zero passage nature disjunction simultaneously when delayed A phase 90 ° of electrical angles.Bring ω t=δ+90 ° into formula (13), can obtain tri-phase iron core remanent magnetism is
Because three-phase system has symmetry, therefore disconnected phase time headed by B, C phase, first mutually disconnected and another two-phase flux change rule is identical with above-mentioned situation, can obtain first disconnected phase remanent magnetism expression formula accordingly, shown in (15).
φ
sd＝φ
msin(δ-90°) (15)
During normal operation, the phase remanent magnetism of the advanced first disconnected phase 120 ° of voltage-phase is
Normal when running the voltage-phase delayed head phase remanent magnetism of 120 ° mutually that breaks be
Embodiment
Build realistic model as shown in Figure 3, in figure: X
lrepresent line impedance, TV represents voltage transformer (VT), and TA represents current transformer, and QK represents three-phase breaker.Carry out sub-switching operation to three-phase breaker QK, signal pickup assembly gathers three-phase voltage current waveform by TA and TV.In this emulation, power-factor angle
iron core stable state magnetic flux peak value φ
m=47.83wb*N, first breaking is B phase mutually, first disconnected phase angle
each phase separating brake moment as shown in Figure 4.Utilize formula (15), (16) tri-phase iron core magnetic flux and in (17) matching separating brake process, compare with emulation magnetic flux, as can be seen from the figure: in separating brake process, estimate that magnetic flux can Curve fitting simulation magnetic flux preferably, when after the equal separating brake of three-phase, estimate that between magnetic flux and emulation magnetic flux, error is very little, this method can effectively estimate tri-phase iron core remanent magnetism as seen.
Below by reference to the accompanying drawings the specific embodiment of the present invention is described; but these explanations can not be understood to limit scope of the present invention; protection scope of the present invention is limited by the claims of enclosing, and any change on the claims in the present invention basis is all protection scope of the present invention.
Claims (1)
- The remanent magnetism method of estimation of 1.Yyn0 type three-phase group formula transformer non-faulting tripping operation, is characterized in that: comprise the steps:When step 1:Yyn0 type three-phase group formula transformer runs, signal pickup assembly is sampled by the voltage current waveform of mutual inductor to Yyn0 type three-phase group formula transformer, obtains electric current and voltage instantaneous value;Step 2: obtain Yyn0 type three-phase group formula transformer stable state three-phase voltage, electric current plural form by fourier algorithm, obtains power-factor angle and iron core stable state magnetic flux peak value φ m, described iron core stable state magnetic flux peak value wherein: U mrepresent phase voltage amplitude, N represents umber of turn, and ω is system angle frequency;Step 3: the three-phase current waveform of acquisition of sampling according to step 1, determines the first mutually disconnected and first phase drop-out voltage phase angle that breaks or described head breaks the phase referring to mutually and first disconnect, namely when first the electric current of certain phase is reduced to zero and remain unchanged, then and disconnected phase headed by this phase;Step 4: estimation tri-phase iron core remanent magnetismSuppose that first breaking is A phase mutually, and first disconnected phase voltage phase angle is δ, known according to formula (7), A phase cut-offs moment tri-phase iron core magnetic flux φ a, φ b, φ cshown in (8);A phase disconnects rear three-phase windings voltage u a'X, u bY, u cZshown in (9), three-phase current i a, i b, i cshown in (10), according to the law of electromagnetic induction, the three-phase produced by this voltage responds to magnetic flux φ in advance ay, φ by, φ cyfor formula (11);According to continuity of magnetic flux theorem, A phase disconnects moment magnetic flux and cannot suddenly change, and leads to φ by producing such as formula the three-phase magnetic bias shown in (12) ap, φ bp, φ cpto offset the pre-induction magnetic flux in this moment;Therefore after A phase disconnects, tri-phase iron core magnetic flux is (8), (11), (12) formula sum, and abbreviation is such as formula shown in (13);According to formula (10), B, C phase will the electric current simultaneously zero passage nature disjunction when delayed A phase 90 ° of electrical angles; Bring ω t=δ+90 ° into formula (13), tri-phase iron core remanent magnetism φ can be obtained ar, φ br, φ crfor formula (14);Because three-phase system has symmetry, therefore disconnected phase time headed by B, C phase, first mutually disconnected and another two-phase flux change rule is identical with above-mentioned situation, can obtain first disconnected phase remanent magnetism expression formula accordingly, shown in (15);φ sd＝φ msin(δ-90°) (15)During normal operation, the phase remanent magnetism of the advanced first disconnected phase 120 ° of voltage-phase is formula (16);Normal when running the voltage-phase delayed head phase remanent magnetism of 120 ° mutually that breaks be formula (17);
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Cited By (2)
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| CN107482600A (en) * | 2017-07-18 | 2017-12-15 | 西安交通大学 | Yyn0 type three-phase group formulas transformer drops excitation surge current suppressing method |
| CN109038491A (en) * | 2018-07-05 | 2018-12-18 | 内蒙古电力(集团)有限责任公司内蒙古电力科学研究院分公司 | A kind of large-scale power transformer excitation surge current suppressing method |
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