CN105048316A - Method for recovering transformer windings from warpage - Google Patents

Abstract

The invention discloses a method for recovering transformer windings from warpage. When a short-circuit force passes the inner winding in a transformer, a radial electromagnetic force generated by axial magnetic leakage generates a radial compression force, and the inner winding is compressed and deformed inwardly by the radial compression force, and distributed relatively uniformly. when the short circuit force passes an outer winding of the transformer, the radial electromagnetic force generated by axial magnetic leakage generates a radial tensile force, so that the outer winding is stretched and deformed outwardly. The radial compression force of a middle-voltage winding (or public winding) is changed into the radial tensile force by utilizing different short-circuit manners, and the windings can be recovered from warpage. The short circuit currents and action time are gradually adjusted to recover the middle-voltage winding (or public winding) from warpage; it is not required to dismount the transformer; maintenance is convenient, the cost is low and speed is high; and the method can be used to recover all middle-voltage windings of three-winding transformer or the common windings of autotransformer with a third winding from warpage.

Description

A kind of Transformer Winding buckling deformation restoration methods

Technical field

The present invention relates to transformer area of maintenance, especially relate to a kind of Transformer Winding buckling deformation restoration methods.

Background technology

China is building electrical network that is safe and reliable, economical and efficient, will form the national interconnected network be made up of four synchronised grids (" three China " electrical network, Northeast China Power Grid, Northwest Grid and south electric network) asynchronous connection.After the interconnected network of the whole nation, capacity of short circuit increases, and terminal short-circuit or near region short circuit will be larger to transformer harm.In addition, the new-energy grid-connecteds such as wind-powered electricity generation also have new demand to short circuit, and grid-connected point voltage falls requires short circuit crossing time 0.625s when being 20%; Nuclear power station main transformer also requires that the duration of short-circuit is 6s.No matter be power transformer, or wind power transformer or nuclear power transformer, they all require excellent anti-short circuit capability.

Transformer runs in electric power system, fought off by various short circuit and can not definitely avoid, particularly outlet or near region short circuit very harmful to power transformer.A large amount of case shows: 90% mechanical failure is caused by the radial buckling deformation of interior winding.Prove that perhaps the transformer damaged can continue to run for many years until turn-to-turn short circuit occurs.

" winding deformation of power transformer measuring and analysis " (" Guizhou power technology " o. 11th in 2006,17-18 page) disclose the method measured about deformation of transformer winding, but suitable restoration methods is not had for the winding be out of shape, existing reparation is returns factory's breakdown maintenance, maintenance cost is high, workload is large, and maintenance time is long.

Summary of the invention

The present invention mainly solves the technical problem of the suitable winding deformation restoration methods of shortage existing for prior art etc., provide a kind of easy to maintenance, cost is low, fireballing Transformer Winding buckling deformation restoration methods.

The present invention is directed to that above-mentioned technical problem mainly solved by following technical proposals: a kind of Transformer Winding buckling deformation restoration methods, be applicable to the middle pressure winding of three-winding transformer or carry the common winding of tertiary winding autotransformer, comprising the following steps:

Winding or common winding buckling deformation amount is pressed in A, measurement;

B, apply short circuit current in the windings, form radial tensile stress and middle pressure winding or common winding buckling deformation are recovered.

When short-circuit force is by winding in transformer, the radial electromagnetic force produced by axial leakage field can generate radial compression stress, and this power can make the inside compression of interior winding, and distributes more equably at interior winding; When short-circuit force is by the outer winding of transformer, the radial electromagnetic force produced by axial leakage field can generate radial tensile force, makes outer winding stretch out distortion.If utilize different short circuit manner to make the radial compression stress of winding become radial tensile force, then winding buckling deformation can recover.

As preferably, described steps A specifically comprises the following steps:

The current reactance Z of winding or common winding is pressed in A01, measurement ¹, calculating reactance variable quantity ε, computing formula is as follows:

ε＝(Z ¹-Z)/Z

In formula, Z is the initial reactance of middle pressure winding or common winding;

A02, judge ε size, if ε is less than 2%, then assert in transformer and press winding or common winding that buckling deformation does not occur, stop all subsequent steps; If ε is more than or equal to 2%, then enter steps A 03;

Press the deflection Δ X of winding or common winding in A03, calculating, computing formula is as follows:

ΔX＝ε×(m-n)

In formula, m is high pressure winding or the radial size of series connection winding, and n is middle pressure winding or the radial size of common winding.

As preferably, described step B specifically comprises the following steps:

The current maximum short circuit current that can bear of B01, calculating transformer, the initial value of setting short-circuit current value is 60% of maximum short circuit current, and short circuit initial value action time is 0.125s;

B02, action time short circuit current is applied to winding according to short-circuit current value and short circuit;

B03, stopping apply short circuit current, and measure winding reactance again, calculating reactance rate of change after suspending 15min, as reactance has returned to initial reactance, then stop subsequent step, whole flow process terminates; If reactance does not return to initial reactance, then enter step B04;

B04, calculating reactance rate of change, if reactance change rate is more than or equal to 0.2%, then return step B02; If reactance change rate is less than 0.2%, then enter step B05;

B05, judge the size of current short-circuit current value, if short-circuit current value is less than 90% of the current maximum short circuit current that can bear of transformer, then increase short-circuit current value and enter step B02, each increase is 10% of maximum short circuit current; If short-circuit current value is more than or equal to 90% of maximum short circuit current, then enter step B06;

B06, increase short circuit action time enter step B02, each increase is 0.125 second.

By suitably adjusting short circuit current size and action time can obtain good maintenance effect.

The substantial effect that the present invention brings is, press winding (or common winding) not need to return factory's breakdown maintenance in the certain buckling deformation of generation, maintenance cost is low, and workload is little, and maintenance time is short.To the low pressure winding that certain buckling deformation occurs, the present invention is also inapplicable.

Accompanying drawing explanation

Fig. 1 presses winding buckling deformation schematic diagram in one of the present invention;

Fig. 2 presses winding buckling deformation and reactance change curve in one of the present invention;

In figure: 1, high pressure winding, 2, middle pressure winding, 3, low pressure winding, 4, unshakable in one's determination.

Embodiment

Below by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is described in further detail.

Embodiment: for three-winding transformer SSZ11-50000/110, partial parameters is as follows:

1. rated capacity: 50000/50000/50000kVA;

2. rated voltage and range of regulation: 110 ± 8 × 1.25%/37/10.5kV;

3. rated current: 262.4/780.2/2749.3A;

4. connection set: YNyn0d11;

5. short-circuit impedance: middle pressure-low pressure 6.77%, high pressure-middle pressure 10.32%, high pressure-low pressure 24.47%.

High pressure-middle pressure short-circuit impedance is less than high pressure-low pressure short-circuit impedance, under transformer runs on high pressure-middle press strip part, in after standing repeatedly short circuit, pressure winding produces inside buckling deformation because of radial compression stress, causes winding that very important deformation occurs after distortion accumulation.

Transformer device structure as shown in Figure 1, comprises unshakable in one's determination 4 and the low pressure winding 3 of arranging from inside to outside, middle pressure winding 2 and high pressure winding 1.

Winding buckling deformation causes coil diameter and main empty path size to change (reduction).Detect winding and occur that bulk deformation effective method is the reactance change of winding deformation.Before the recovery adopting Transformer Winding buckling deformation, first to measure buckling deformation amount.

The formula of winding leakage reactance meets:

Z _L＝ω·μ ₀·ρ·W ²·D·δ/H

In formula, ω-angular frequency;

μ ₀-magnetic permeability;

ρ-Luo Shi coefficient;

W-umber of turn;

D-winding average diameter [mm];

δ-main empty path decreasing value;

H-reactance height.

Winding leakage reactance rate of change:

${\mathrm{\ΔZ}}_L\≅\frac{\mathrm{\Δ}X}{(m-n)}$

In formula, the winding size of (m-n)-given;

The change of Δ X-winding mean radius, can just can bear different winding.

For three-winding transformer or the autotransformer being with the tertiary winding, the warpage caused by short circuit current can find in common winding or the 3rd (low pressure) winding.

Press (or public) winding warpage in Fig. 1, then have:

ε _MV-LV≈G _MV-LV(△x)，ε _HV-MV≈-G _HV-MV(△x)，ε _HV-LV≈0，ε _MV-LV/ε _HV-MV≈const

Middle pressure (or public) winding warpage, MV-LV and HV-MV reactance change has contrary sign, ε _hV-LVclose to zero-sum ε _mV-LV/ε _hV-MVratio is the size that definite value determines measure error.

Said method both may be used for single-phase short circuit impedance experiments, also may be used for three-phase shortcircuit impedance experiments.

Double winding or three-winding transformer:

${\mathrm{\ϵ}}_A=(X_A^1-X_A)/X_A\≈G_A\left({\mathrm{\Δx}}_A\right)$

${\mathrm{\ϵ}}_B=(X_B^1-X_B)/X_B\≈G_B\left({\mathrm{\Δx}}_B\right)$

${\mathrm{\ϵ}}_C=(X_C^1-X_C)/X_C\≈G_C\left({\mathrm{\Δx}}_C\right)$

Reactance relatively changes and is divided into practical distortion and measure error two parts:

ε _A＝ε _dA+ε _eA，ε _B＝ε _dB+ε _eB，ε _C＝ε _dC+ε _eC

Suppose in formula that measure error is less than 2%, then have:

1) without buckling deformation

Reactance change is only caused by measure error, therefore:

ε _dA＝ε _dB＝ε _dC＝0，|ε _eA|＝ε _A<2％，|ε _eB|＝ε _B<2％，|ε _eC|＝ε _C<2％

2) all three-phases have buckling deformation:

ε _A>2％，ε _B>2％，ε _C>2％

3) one has buckling deformation mutually, is assumed to be A phase, then:

ε _A>2％，ε _B<2％，ε _C<2％

4) inaccurate measurement, then a phase, two-phase or three-phase ε are negative value.

Be illustrated in figure 2 the buckling deformation of middle pressure winding and reactance change curve chart.

Quantification can be carried out to distortion according to Fig. 2:

The slight plastic deformation that △ X≤5mm-causes due to temperature and short-circuit force;

5mm≤△ X≤10mm-is obviously out of shape;

△ X>10mm-gross distortion.

The relative change of leakage reactance can obtain according to short-circuit impedance measured data, and the method may be used for the deflection verifying and evaluate fault winding.Inapplicable for gross distortion this patent, in fact may to there is turn-to-turn insulation and lost efficacy in transformer.

Short circuit recovery process is as follows:

The current maximum short circuit current that can bear of B01, calculating transformer, the initial value of setting short-circuit current value is 60% of maximum short circuit current, and short circuit initial value action time is 0.125s;

B02, fixing short circuit current and action time are applied to winding;

B03, stopping apply short circuit current, and measure winding reactance again, calculating reactance rate of change after suspending 15min, as reactance has returned to initial reactance, then stop subsequent step, whole flow process terminates; If reactance does not return to initial reactance, then enter step B04;

B04, calculating reactance rate of change, if reactance change rate is more than or equal to 0.2%, then return step B02; If reactance change rate is less than 0.2%, then enter step B05;

B05, judge the size of current short-circuit current value, if short-circuit current value is less than 90% of the current maximum short circuit current that can bear of transformer, then increase short-circuit current value and enter step B02, each increase is 10% of maximum short circuit current; If short-circuit current value is more than or equal to 90% of maximum short circuit current, then enter step B06;

B06, increase short circuit action time enter step B02, each increase is 0.125 second.

Specific embodiment described herein is only to the explanation for example of the present invention's spirit.Those skilled in the art can make various amendment or supplement or adopt similar mode to substitute to described specific embodiment, but can't depart from spirit of the present invention or surmount the scope that appended claims defines.

Although more employ the term such as winding, short circuit herein, do not get rid of the possibility using other term.These terms are used to be only used to describe and explain essence of the present invention more easily; The restriction that they are construed to any one additional is all contrary with spirit of the present invention.

Claims (3)

1. a Transformer Winding buckling deformation restoration methods, is applicable to the middle pressure winding of three-winding transformer or carries the common winding of tertiary winding autotransformer, it is characterized in that, comprise the following steps:

Winding or common winding buckling deformation amount is pressed in A, measurement;

B, apply short circuit current in the windings, form radial tensile stress and middle pressure winding or common winding buckling deformation are recovered.

2. a kind of Transformer Winding buckling deformation restoration methods according to claim 1, it is characterized in that, described steps A specifically comprises the following steps:

The current reactance Z of winding or common winding is pressed in A01, measurement ¹, calculating reactance variable quantity ε, computing formula is as follows:

ε＝(Z ¹-Z)/Z

In formula, Z is the initial reactance of middle pressure winding or common winding;

A02, judge ε size, if ε is less than 2%, then assert in transformer and press winding or common winding that buckling deformation does not occur, stop all subsequent steps; If ε is more than or equal to 2%, then enter steps A 03;

Press the deflection Δ X of winding or common winding in A03, calculating, computing formula is as follows:

ΔX＝ε×(m-n)

In formula, m is high pressure winding or the radial size of series connection winding, and n is middle pressure winding or the radial size of common winding.

3. a kind of Transformer Winding buckling deformation restoration methods according to claim 1 and 2, it is characterized in that, described step B specifically comprises the following steps:

The current maximum short circuit current that can bear of B01, calculating transformer, the initial value of setting short-circuit current value is 60% of maximum short circuit current, and short circuit initial value action time is 0.125s;

B02, action time short circuit current is applied to winding according to short-circuit current value and short circuit;

B03, stopping apply short circuit current, and measure winding reactance again, calculating reactance rate of change after suspending 15min, as reactance has returned to initial reactance, then stop subsequent step, whole flow process terminates; If reactance does not return to initial reactance, then enter step B04;

B04, calculating reactance rate of change, if reactance change rate is more than or equal to 0.2%, then return step B02; If reactance change rate is less than 0.2%, then enter step B05;

B05, judge the size of current short-circuit current value, if short-circuit current value is less than 90% of the current maximum short circuit current that can bear of transformer, then increase short-circuit current value and enter step B02, each increase is 10% of maximum short circuit current; If short-circuit current value is more than or equal to 90% of maximum short circuit current, then enter step B06;

B06, increase short circuit action time enter step B02, each increase is 0.125 second.