CN105699799A - Oil-immersed transformer overtemperature warning method under harmonic condition - Google Patents

Abstract

The present invention relates to an oil-immersed transformer overtemperature warning method under a harmonic condition. The method comprises a step of determining any harmonic current distribution and the transformer winding eddy current loss, transformer stray loss and transformer total load loss actual values of a same total current effective value, a step of determining the relation among a transformer load loss, a harmonic distortion rate and a load rate, a step of determining the relation among a transformer hottest point temperature rise, the harmonic distortion rate and the load rate, and a step of determining the threshold of a corresponding alert level. According to the method, through transforming the basic formula of the transformer harmonic loss, the relation among the harmonic loss, a harmonic current distortion rate and the load rate is obtained, thus according to the relation model between transformer temperature rise and loss, the temperature rise condition of a transformer after a certain time is derived, and the early warning of the transformer temperature rise is realized.

Description

A kind of oil-filled transformer excess temperature method for early warning under harmonic condition

Technical field:

The present invention relates to a kind of transformator excess temperature method for early warning, be more particularly to the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition。

Background technology:

Along with in electrical network nonlinear load application increasingly extensive, harmonic wave be present in send out, defeated, join the links with electricity consumption, for component devices transformator most important in power system, harmonic wave can make transformator produce added losses, heating is caused to increase, high oil temperature, directly result in Transformer Insulation Aging, service life reduces, and causes economic loss directly or indirectly to electric power enterprise。Power supply department in the urgent need to causing the too high calculating being correlated with of transformator temperature rise to harmonic wave, and carries out early warning, and the temperature rising state current to understand transformator in time makes harness of harmonic wave targetedly and the control measures that transformator temperature rise is too high。

Currently also have from the heating principle of transformator to analyze transformator temperature rise, but do not consider percent harmonic distortion and the impact on transformator temperature rise of load factor two aspect, quantitative analysis Shortcomings to the influence factor of transformator temperature rise and affecting laws thereof, have impact on the accuracy formulating utility power quality control index and analyze harmonic wave transformator is affected the reasonability of economy, and it is substantially free of and realizes transformator temperature rise early warning mechanism and method, the time dependent trend of transformator temperature rise cannot be presented intuitively, cannot for administering the objective and accurate foundation of the too high offer of transformator temperature rise。

Therefore, if the added losses that under different loads rate and percent harmonic distortion, transformator produces because of harmonic wave can be calculated, and then calculate the temperature rise of transformator, design the method for early warning of transformator, namely the temperature rise situation after can predicting transformator certain time, and counter-measure can be taked according to practical situation, for formulating specific aim measure to improve operational efficiency and the economy of electrical network, conscientiously ensure that the interests of each side such as power supply department and user have theoretical research value and realistic meaning further。

Summary of the invention:

It is an object of the invention to provide the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition, the method is analyze to grasp transformator loss under Harmonic Conditions and temperature rise situation provides the necessary technical means。

For achieving the above object, the present invention is by the following technical solutions: the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition, it is characterised in that: said method comprising the steps of:

(1) distribution of any harmonic current and the Transformer Winding eddy-current loss of same total current virtual value, stray loss of transformer and the famous value of transformator total load loss are determined；

(2) relation of transformer load loss, percent harmonic distortion and load factor is determined；

(3) relation of transformator temperature rise at the hottest point, percent harmonic distortion and load factor is determined；

(4) threshold value of corresponding warning level is determined。

Oil-filled transformer excess temperature method for early warning under a kind of harmonic condition provided by the invention, described step (1) determines Transformer Winding eddy-current loss, stray loss of transformer and the famous value of transformator total load loss by setting up the decomposition model of transformer loss。

Oil-filled transformer excess temperature method for early warning under a kind of harmonic condition provided by the invention, the loss of described transformator includes the total losses P of transformator_TOTAL, transformator load loss P_LL, transformator eddy-current loss P_ECStray loss P with transformator_OSL；And determine respectively through following formula:

P_TOTAL=P_NL+P_LL(1)

P_LL=P+P_EC+P_OSL(2)

$P_{\mathrm{EC}}=P_{\mathrm{EC}-R}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2---\left(3\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-R}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^{0.8}---\left(4\right)$

In formula: P_NLFor the open circuit loss of transformator, P is the resistance loss of transformator, I_RFor transformer current virtual value under rated condition, I_hIt is h subharmonic current virtual value, P_EC-REddy-current loss when being specified power frequency, P_OSL-RStray loss when being specified power frequency；H is overtone order, h_maxThe most high reps of harmonic wave for paying close attention to。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, winding eddy current loss and the stray loss of the distribution of described any harmonic current and unified total current virtual value are determined respectively through following formula:

$P_{\mathrm{EC}}=P_{\mathrm{EC}-O}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2---\left(5\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-O}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^{0.8}---\left(6\right)$

Wherein:

$I=\sqrt{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{I_h}^2}$

In formula: P_EC-OIt is power frequency but current effective value is eddy-current loss during I, P_OSL-OBeing power frequency but current effective value is stray loss during I, I is current effective value；

Described formula (5) and formula (6) be:

$P_{\mathrm{EC}}=P_{\mathrm{EC}-R}=\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2=P_{\mathrm{EC}-R}\×F_{\mathrm{HL}}\×{\left(\frac{I_1}{I_R}\right)}^2\×(1+{{\mathrm{THD}}_i}^2)---\left(7\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-R}=\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2=P_{\mathrm{OSL}-R}\×F_{\mathrm{HL}-\mathrm{STR}}\×{\left(\frac{I_1}{I_R}\right)}^2\×(1+{{\mathrm{THD}}_i}^2)---\left(8\right)$

Wherein: coefficient F_HLAnd F_HL-STRIt is respectively as follows:

$F_{\mathrm{HL}}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2{h}^2}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2}---\left(9\right)$

$F_{\mathrm{HL}-\mathrm{STR}}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^{0.8}}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2{h}^{0.8}}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2}---\left(10\right)$

In formula: I₁For first-harmonic virtual value, THD_iFor Harmonic Current Distortion rate, F_HLFor the harmonic loss coefficient of eddy-current loss, F_HL-STRHarmonic loss coefficient for other stray loss。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, the described transformator famous value of total load loss is determined by following formula:

$P_{\mathrm{LL}}=\underset{h=1}{\overset{h_{\max }}{\mathrm{\Σ}}}{I}_h^2{R}_{\mathrm{dc}}+P_{\mathrm{EC}}+P_{\mathrm{OSL}}={\left(\frac{I_1}{I_R}\right)}^2\×\left({{1+\mathrm{THD}}_i}^2\right)\×({I_R}^2{R}_{\mathrm{dc}}+P_{\mathrm{EC}-R}\×F_{\mathrm{HL}}+P_{\mathrm{OSL}-R}\×F_{\mathrm{HL}-\mathrm{STR}})---\left(11\right)$

In formula: R_dcD.C. resistance for transformator。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, the transformer load loss of described step (2) respectively with square proportional example of the quadratic sum load factor of described percent harmonic distortion。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, the top-oil temperature that transformator temperature rise at the hottest point is transformator relative ambient temperature of described step (3) rises the hottest point temperature rise of conductor sum of top-oil temperature degree relative to transformator。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, the top-oil temperature of described transformator relative ambient temperature rises the hottest point temperature rise of conductor of top-oil temperature degree relative to transformator and determines respectively through following formula:

${\mathrm{\θ}}_{\mathrm{TO}}={\mathrm{\θ}}_{\mathrm{TO}-R}\×{\left(\frac{P_{\mathrm{LL}}+P_{\mathrm{NL}}}{P_{\mathrm{LL}-R}+P_{\mathrm{NL}}}\right)}^{0.8}---\left(12\right)$

Wherein, θ_TOFor the top-oil temperature liter of relative ambient temperature, θ_TO-RFor the top-oil temperature liter of relative ambient temperature, P under rated condition_LL-RFor the load loss under rated condition；

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{\left(\frac{P_{\mathrm{LL}}\left(\mathrm{pu}\right)}{P_{\mathrm{LL}-R}\left(\mathrm{pu}\right)}\right)}^{0.8}---\left(13\right)$

Wherein: θ_gFor the hottest point temperature rise of conductor of relative top-oil temperature degree, θ_g-RFor the hottest point temperature rise of conductor of top-oil temperature degree relative under rated condition, P_LL(pu) for load loss perunit value, P_LL-R(pu) for load loss perunit value under rated condition；

To all turn ratios more than 4:1, and at least one winding has the maximum transformator from cooling current capacity more than 1000A, then formula (13) is:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{(\frac{1+2.8\×F_{\mathrm{HL}}\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}{1+2.8\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}\×I{\left(\mathrm{pu}\right)}^2)}^{0.8}---\left(14\right)$

To other transformator, it is:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{(\frac{1+2.4\×F_{\mathrm{HL}}\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}{1+2.4\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}\×I{\left(\mathrm{pu}\right)}^2)}^{0.8}---\left(15\right)$

Wherein: the perunit value that I (pu) is transformer current, P_EC-R(pu) for eddy-current loss perunit value under rated condition。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, the temperature rise of described transformator is forward proportionate relationship with percent harmonic distortion and load factor respectively。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, using the temperature rise at the hottest point of transformator as the index of transformator early warning under harmonic condition, according to transformator temperature rise KB limit limits value the most under all kinds of load conditions of regulation in " power transformer operating standard ", two temperature gap scopes of zero degree Yu KB limit are divided into several warning level, it is determined that the threshold value of the corresponding warning level of described step (4)。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, based on the Monitoring Data that electric energy quality monitoring system provides, by calculating corresponding transformator harmonic loss and temperature rise at the hottest point, threshold value in conjunction with described warning level carries out at least one hour transformator temperature rise at the hottest point, and carries out early warning。

Oil-filled transformer excess temperature method for early warning under another preferred a kind of harmonic condition provided by the invention, by the Historical Monitoring data of described electric energy quality monitoring system and transformer load prediction data, the temperature rise at the hottest point of transformator after calculating at least one hour, the threshold value in conjunction with described warning level carries out transformator temperature rise at the hottest point early warning。

With immediate prior art ratio, the present invention provides technical scheme to have following excellent effect

1, the harmonic loss of transformator is expressed as the expression formula relevant with Harmonic Current Distortion rate and load factor by the method for the present invention, can intuitive analysis percent harmonic distortion and the load factor impact on transformator temperature rise, and then and realize the early warning of transformator temperature rise；

2, the method for the present invention is simple, it is only necessary to the Monitoring Data of electric energy quality monitoring system and transformer load data can achieve the quick and accurate early warning of transformator excess temperature；

3, the method for present invention temperature rise early warning occasion of transformator under harmonic condition has significantly high using value and marketing prospect；

4, the method for the present invention is for predicting transformator temperature rise in certain time, grasps transformator loss under Harmonic Conditions and temperature rise situation provides the necessary technical means for analyzing；

5, the method for the present invention avoids Transformer Insulation Aging, and minimizing in service life and electric power enterprise cause the generation of economic loss directly or indirectly；

6, the method for the present invention can take counter-measure according to the practical situation that transformator heats up, formulate specific aim measure to improve operational efficiency and the economy of electrical network, conscientiously ensure that the interests of each side such as power supply department and user have theoretical research value and realistic meaning further。

Accompanying drawing explanation

Fig. 1 is the decomposition model figure of the transformer loss of the present invention；

Fig. 2 is the transformer load loss graph of a relation with percent harmonic distortion and load factor of the present invention；

Fig. 3 is the transformator temperature rise at the hottest point graph of a relation with percent harmonic distortion and load factor of the present invention；

Fig. 4 is the transformator temperature rise early warning plane drawing of the present invention。

Detailed description of the invention

Below in conjunction with embodiment, the invention will be described in further detail。

Embodiment 1:

As Figure 1-4, the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition that the invention of this example provides, said method comprising the steps of:

Fig. 1 is the decomposition model of transformer loss；The each several part loss calculation of transformator is as follows:

P_TOTAL=P_NL+P_LL(1)

P_LL=P+P_EC+P_OSL(2)

$P_{\mathrm{EC}}=P_{\mathrm{EC}-R}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2---\left(3\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-R}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^{0.8}---\left(4\right)$

In formula: P_TOTALFor the total losses of transformator, P_NLFor the open circuit loss of transformator, P_LLFor the load loss of transformator, P is the resistance loss of transformator, P_ECIt is the eddy-current loss of transformator, P_OSL-RIt is the stray loss of transformator, I_RFor transformer current virtual value under rated condition, I_hIt is h subharmonic current virtual value, P_EC-REddy-current loss when being specified power frequency, P_OSL-RStray loss when being specified power frequency；H is overtone order, h_maxThe most high reps of harmonic wave for paying close attention to。

Can obtain having the distribution of any harmonic current, and total current virtual value is that winding eddy current loss during I, stray loss are respectively as follows:

$P_{\mathrm{EC}}=P_{\mathrm{EC}-O}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2---\left(5\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-O}\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^{0.8}---\left(6\right)$

Wherein:

$I=\sqrt{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{I_h}^2}$

In formula: P_EC-OIt is power frequency but current effective value is eddy-current loss during I, P_OSL-OBeing power frequency but current effective value is stray loss during I, I is current effective value；

Formula (5) and formula (6) can be rewritten as respectively:

$P_{\mathrm{EC}}=P_{\mathrm{EC}-R}=\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2=P_{\mathrm{EC}-R}\×F_{\mathrm{HL}}\×{\left(\frac{I_1}{I_R}\right)}^2\×(1+{{\mathrm{THD}}_i}^2)---\left(7\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-R}=\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2=P_{\mathrm{OSL}-R}\×F_{\mathrm{HL}-\mathrm{STR}}\×{\left(\frac{I_1}{I_R}\right)}^2\×(1+{{\mathrm{THD}}_i}^2)---\left(8\right)$

Wherein: coefficient F_HLAnd F_HL-STRIt is respectively as follows:

$F_{\mathrm{HL}}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2{h}^2}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2}---\left(9\right)$

$F_{\mathrm{HL}-\mathrm{STR}}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^{0.8}}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2}=\frac{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2{h}^{0.8}}{\underset{h=1}{\overset{{h=h}_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2}---\left(10\right)$

In formula: I₁For first-harmonic virtual value, THD_iFor Harmonic Current Distortion rate, F_HLFor the harmonic loss coefficient of eddy-current loss, F_HL-STRHarmonic loss coefficient for other stray loss；

By above (7), (8) two formulas it can be seen that under harmonic condition the eddy-current loss of transformator and stray loss with all with square proportional example of the load factor of Harmonic Current Distortion rate and transformator。

According to above-mentioned analysis, there is the distribution of any harmonic wave, and total current virtual value to be the transformator famous value of total load loss during I be:

$P_{\mathrm{LL}}=\underset{h=1}{\overset{h_{\max }}{\mathrm{\Σ}}}{I}_h^2{R}_{\mathrm{dc}}+P_{\mathrm{EC}}+P_{\mathrm{OSL}}={\left(\frac{I_1}{I_R}\right)}^2\×\left({{1+\mathrm{THD}}_i}^2\right)\×({I_R}^2{R}_{\mathrm{dc}}+P_{\mathrm{EC}-R}\×F_{\mathrm{HL}}+P_{\mathrm{OSL}-R}\×F_{\mathrm{HL}-\mathrm{STR}})---\left(11\right)$

In formula: R_dcD.C. resistance for transformator；

By formula (11) namely may know that transformer load loss and percent harmonic distortion under harmonic condition and load factor square proportional example。Both loss relations with transformer load can from accompanying drawing 2。

To oil-filled transformer, the calculating of top-oil temperature liter can be carried out according to following formula:

${\mathrm{\θ}}_{\mathrm{TO}}={\mathrm{\θ}}_{\mathrm{TO}-R}\×{\left(\frac{P_{\mathrm{LL}}+P_{\mathrm{NL}}}{P_{\mathrm{LL}-R}+P_{\mathrm{NL}}}\right)}^{0.8}---\left(12\right)$

Wherein: θ_TOFor the top-oil temperature liter of relative ambient temperature, θ_TO-RFor the top-oil temperature liter of relative ambient temperature, P under rated condition_LL-RFor the load loss under rated condition；

Winding hottest point temperature rise of conductor is likewise proportional to 0.8 power of load loss, and available formula (13) calculates:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{\left(\frac{P_{\mathrm{LL}}\left(\mathrm{pu}\right)}{P_{\mathrm{LL}-R}\left(\mathrm{pu}\right)}\right)}^{0.8}---\left(13\right)$

Wherein: θ_gFor the hottest point temperature rise of conductor of relative top-oil temperature degree, θ_g-RFor the hottest point temperature rise of conductor of top-oil temperature degree relative under rated condition, P_LL(pu) for load loss perunit value, P_LL-R(pu) for load loss perunit value under rated condition；

Then to all turn ratios more than 4:1, and at least one winding has the maximum transformator from cooling current capacity more than 1000A, and formula (13) will be rewritten as:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{(\frac{1+2.8\×F_{\mathrm{HL}}\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}{1+2.8\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}\×I{\left(\mathrm{pu}\right)}^2)}^{0.8}---\left(14\right)$

To other transformator, it is:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{(\frac{1+2.4\×F_{\mathrm{HL}}\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}{1+2.4\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}\×I{\left(\mathrm{pu}\right)}^2)}^{0.8}---\left(15\right)$

Wherein: the perunit value that I (pu) is transformer current, P_EC-R(pu) for eddy-current loss perunit value under rated condition；

And the temperature rise at the hottest point of transformator versus environmental is:

θ_h=θ_TO+θ_g(16)

In formula: θ_hTemperature rise at the hottest point for versus environmental；

By above formula it can be seen that the temperature rise of transformator is relevant with the loss of transformator, transformer loss and percent harmonic distortion and load factor be forward ratio it can be seen that the temperature rise of transformator is basic and percent harmonic distortion and load factor are also forward proportionate relationship。Fig. 3 gives the relation of certain transformator temperature rise at the hottest point and percent harmonic distortion and load factor。

Fig. 4 is transformator temperature rise early warning schematic diagram, namely using the temperature rise at the hottest point of transformator as the specific targets of transformator early warning under harmonic condition, according to transformator temperature rise KB limit limits value the most under all kinds of load conditions of regulation in " power transformer operating standard ", two temperature gap scopes of this zero degree Yu KB limit are divided into several warning level, it is determined that go out the threshold value of corresponding warning level。

Based on the Monitoring Data that electric energy quality monitoring system provides, by calculating corresponding transformator harmonic loss, and then calculate temperature rise at the hottest point, carry out transformator temperature rise at the hottest point in certain time in conjunction with threshold value, and carry out early warning；In conjunction with Historical Monitoring data and the transformer load prediction data of electric energy quality monitoring system, after calculating the long period (such as 1h-24h) temperature rise at the hottest point of transformator, in conjunction with threshold value carry out long-time in transformator temperature rise at the hottest point early warning。

Finally should be noted that: above example is only in order to illustrate that technical scheme is not intended to limit; although those of ordinary skill in the field with reference to above-described embodiment it is understood that still the specific embodiment of the present invention can be modified or equivalent replace; these are without departing from any amendment of spirit and scope of the invention or equivalent replace, within the claims of the present invention all awaited the reply in application。

Claims (12)

1. the oil-filled transformer excess temperature method for early warning under a harmonic condition, it is characterised in that: said method comprising the steps of:

(1) distribution of any harmonic current and the Transformer Winding eddy-current loss of same total current virtual value, stray loss of transformer and the famous value of transformator total load loss are determined；

(2) relation of transformer load loss, percent harmonic distortion and load factor is determined；

(3) relation of transformator temperature rise at the hottest point, percent harmonic distortion and load factor is determined；

(4) threshold value of corresponding warning level is determined。

2. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 1, it is characterised in that: described step (1) determines Transformer Winding eddy-current loss, stray loss of transformer and the famous value of transformator total load loss by setting up the decomposition model of transformer loss。

3. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 2, it is characterised in that: the loss of described transformator includes the total losses P of transformator_TOTAL, transformator load loss P_LL, transformator eddy-current loss P_ECStray loss P with transformator_OSL；And determine respectively through following formula:

P_TOTAL=P_NL+P_LL(1)

P_LL=P+P_EC+P_OSL(2)

$P_{\mathrm{EC}}=P_{\mathrm{EC}-R}\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2---\left(3\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-R}\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^{0.8}---\left(4\right)$

In formula: P_NLFor the open circuit loss of transformator, P is the resistance loss of transformator, I_RFor transformer current virtual value under rated condition, I_hIt is h subharmonic current virtual value, P_EC-REddy-current loss when being specified power frequency, P_OSL-RStray loss when being specified power frequency；H is overtone order, h_maxThe most high reps of harmonic wave for paying close attention to。

4. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 3, it is characterised in that: winding eddy current loss and the stray loss of the distribution of described any harmonic current and unified total current virtual value are determined respectively through following formula:

$P_{\mathrm{EC}}=P_{\mathrm{EC}-O}\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2---\left(5\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-O}\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2---\left(6\right)$

Wherein:

$I=\sqrt{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{I_h}^2}$

In formula: P_EC-OIt is power frequency but current effective value is eddy-current loss during I, P_OSL-OBeing power frequency but current effective value is stray loss during I, I is current effective value；

Described formula (5) and formula (6) be:

$P_{\mathrm{EC}}=P_{\mathrm{EC}-R}\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2=P_{\mathrm{EC}-R}\×F_{\mathrm{HL}}\×{\left(\frac{I_1}{I_R}\right)}^2\×\left({1+{\mathrm{THD}}_i}^2\right)---\left(7\right)$

$P_{\mathrm{OSL}}=P_{\mathrm{OSL}-R}\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_R}\right)}^2{h}^2=P_{\mathrm{OSL}-R}\×F_{\mathrm{HL}-\mathrm{STR}}\×{\left(\frac{I_1}{I_R}\right)}^2\×\left({1+{\mathrm{THD}}_i}^2\right)---\left(8\right)$

Wherein: coefficient F_HLAnd F_HL-STRIt is respectively as follows:

$F_{\mathrm{HL}}=\frac{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^2}{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2}=\frac{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2{h}^2}{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2}---\left(9\right)$

$F_{\mathrm{HL}-\mathrm{STR}}=\frac{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2{h}^{0.8}}{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I}\right)}^2}=\frac{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2{h}^{0.8}}{\underset{h=1}{\overset{h=h_{\max }}{\mathrm{\Σ}}}{\left(\frac{I_h}{I_1}\right)}^2}---\left(10\right)$

In formula: I₁For first-harmonic virtual value, THD_iFor Harmonic Current Distortion rate, F_HLFor the harmonic loss coefficient of eddy-current loss, F_HL-STRHarmonic loss coefficient for other stray loss。

5. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 4, it is characterised in that: the described transformator famous value of total load loss is determined by following formula:

$P_{\mathrm{LL}}=\underset{h=1}{\overset{h_{\max }}{\mathrm{\Σ}}}{I}_h^2{R}_{\mathrm{dc}}+P_{\mathrm{EC}}+P_{\mathrm{OSL}}={\left(\frac{I_1}{I_R}\right)}^2\×(1+{{\mathrm{THD}}_i}^2)\×({I_R}^2{R}_{\mathrm{dc}}+P_{\mathrm{EC}-R}\×F_{\mathrm{HL}}+P_{\mathrm{OSL}-R}\×F_{\mathrm{HL}-\mathrm{STR}})---\left(11\right)$

In formula: R_dcD.C. resistance for transformator。

6. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition stated such as claim 1-5 institute any one, it is characterised in that: the transformer load loss of described step (2) respectively with square proportional example of the quadratic sum load factor of described percent harmonic distortion。

7. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 1, it is characterised in that: the top-oil temperature that transformator temperature rise at the hottest point is transformator relative ambient temperature of described step (3) rises the hottest point temperature rise of conductor sum of top-oil temperature degree relative to transformator。

8. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 7, it is characterised in that: the top-oil temperature of described transformator relative ambient temperature rises the hottest point temperature rise of conductor of top-oil temperature degree relative to transformator and determines respectively through following formula:

${\mathrm{\θ}}_{\mathrm{TO}}={\mathrm{\θ}}_{\mathrm{TO}-R}\×{\left(\frac{P_{\mathrm{LL}}+P_{\mathrm{NL}}}{P_{\mathrm{LL}-R}+P_{\mathrm{NL}}}\right)}^{0.8}---\left(12\right)$

Wherein, θ_TOFor the top-oil temperature liter of relative ambient temperature, θ_TO-RFor the top-oil temperature liter of relative ambient temperature, P under rated condition_LL-RFor the load loss under rated condition；

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{\left(\frac{P_{\mathrm{LL}}\left(\mathrm{pu}\right)}{P_{\mathrm{LL}-R}\left(\mathrm{pu}\right)}\right)}^{0.8}---\left(13\right)$

Wherein: θ_gFor the hottest point temperature rise of conductor of relative top-oil temperature degree, θ_g-RFor the hottest point temperature rise of conductor of top-oil temperature degree relative under rated condition, P_LL(pu) for load loss perunit value, P_LL-R(pu) for load loss perunit value under rated condition；

To all turn ratios more than 4:1, and at least one winding has the maximum transformator from cooling current capacity more than 1000A, then formula (13) is:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{(\frac{1+2.8\×F_{\mathrm{HL}}\×F_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}{1+2.8\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}\×I{\left(\mathrm{pu}\right)}^2)}^{0.8}---\left(14\right)$

To other transformator, it is:

${\mathrm{\θ}}_g={\mathrm{\θ}}_{g-R}\×{(\frac{1+2.4\×F_{\mathrm{HL}}\×F_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}{1+2.4\×P_{\mathrm{EC}-R}\left(\mathrm{pu}\right)}\×I{\left(\mathrm{pu}\right)}^2)}^{0.8}---\left(15\right)$

Wherein: the perunit value that I (pu) is transformer current, P_EC-R(pu) for eddy-current loss perunit value under rated condition。

9. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 8, it is characterised in that: the temperature rise of described transformator is forward proportionate relationship with percent harmonic distortion and load factor respectively。

10. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as described in claim 1 or 7, it is characterized in that: using the temperature rise at the hottest point of transformator as the index of transformator early warning under harmonic condition, according to transformator temperature rise KB limit limits value the most under all kinds of load conditions of regulation in " power transformer operating standard ", two temperature gap scopes of zero degree Yu KB limit are divided into several warning level, it is determined that the threshold value of the corresponding warning level of described step (4)。

11. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as claimed in claim 10, it is characterized in that: based on the Monitoring Data that electric energy quality monitoring system provides, by calculating corresponding transformator harmonic loss and temperature rise at the hottest point, threshold value in conjunction with described warning level carries out at least one hour transformator temperature rise at the hottest point, and carries out early warning。

12. the oil-filled transformer excess temperature method for early warning under a kind of harmonic condition as described in claim 10 or 11, it is characterized in that: by the Historical Monitoring data of described electric energy quality monitoring system and transformer load prediction data, the temperature rise at the hottest point of transformator after calculating at least one hour, the threshold value in conjunction with described warning level carries out transformator temperature rise at the hottest point early warning。