CN105447630A - Main transformer displacement strategy making method based on major emergency defect rate - Google Patents

Abstract

The invention discloses a main transformer displacement strategy making method based on the major emergency defect rate. The method includes acquiring the key attribute data of all main transformers as the research object; calculating the major emergency defect rate of each main transformer in each operating year, performing regression analysis on the major emergency defect rate and the operating years of each main transformer, establishing a regression model of the major emergency defect rate and the operating years, and determining the model parameters by means of a least square theory; establishing a target function and a constrained condition based on the main transformer damaged degree reduction degree/displacement cost maximization principle; and obtaining the main transformer displacement strategy through the adoption of an implicit enumeration method to solve the target function. The method guarantees the main transformer risk in an acceptable range, acquires the high fund utilization efficiency, and effectively assists power grid enterprises to develop investment decisions through the establishment of the predicted model of the main transformer major emergency defect rate and based on the optimal manner of equipment damaged reduction degree cost ratio.

Description

A kind of main-transformer Replacement Strategy formulating method based on major emergency ratio of defects

Technical field

The present invention relates to a kind of main-transformer Replacement Strategy formulating method, particularly a kind of main-transformer Replacement Strategy formulating method based on major emergency ratio of defects.

Background technology

Along with the propelling that electric network informationization is built, electrical network production run process creates mass data, these data contain many with safety in production and equipment control etc. the closely-related rule and characteristic in field, technological means is utilized to excavate these data analysis, therefrom obtain useful data, auxiliary enterprises can hold the internal characteristics of electrical network production run, grasp management rule, refine business model, Added Management decision-making, developing management innovation, thus the management lean level of enterprise, Promoting Enterprise way to manage by extensive style to intensive style, become more meticulous transformation.

In power grid asset life cycle management, equipment O&M is the link that wherein time is the longest.In this course, create a large amount of production data such as defect record, accident event record, test figure, online monitoring data, these data are not only significant to production safety management itself, also retired aid decision making that each stage works and the later evaluation such as to scrap in preconsolidation stress, design, construction and later stage had to important references and are worth.

Existing equipment Replacement Strategy formulating method major part only considers the degradation of equipment, and does not consider the impact of equipment displacement on electrical network overall risk, meanwhile, considers also less to the fund utilization ratio of entirety.

Summary of the invention

The object of the present invention is to provide a kind of obtain higher fund utilization ratio, reduction equipment displacement on electrical network overall risk impact the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects, can power grid enterprises be effectively assisted to carry out investment in technological upgrading decision-making, help lend some impetus to asset life cycle management horizontal coordination, the management lean level of enterprise.

Above-mentioned purpose of the present invention realizes by the following technical solutions: a kind of main-transformer Replacement Strategy formulating method based on major emergency ratio of defects, is characterized in that comprising the following steps:

Step S101, obtains the determinant attribute data of the whole main-transformers as research object;

Step S102, calculates the major emergency ratio of defects of each main-transformer at the time limit that respectively puts into operation:

Step S103, the large urgent ratio of defects heavy to each main-transformer carries out regretional analysis with the time limit that puts into operation, and sets up major emergency and lacks limit rate and the regression model of the time limit that puts into operation, adopt principle of least square method Confirming model parameter;

Step S104, according to " main-transformer damage degree reduces degree/displacement expense " maximization principle, sets up objective function and constraint condition;

Step S105, adopts implicit enumeration method to solve objective function, obtains main-transformer Replacement Strategy.

" main-transformer damage degree reduces degree/displacement expense " of the present invention maximization principle refers to and namely uses identical displacement expense, and the degree that the main-transformer extent of damage can reduce is maximum, and the fund utilization ratio of explanation is the highest.

The present invention is by setting up main transformer major emergency ratio of defects forecast model, and according to equipment impaired reduction degree cost than optimum mode, in guarantee main transformer risk within the acceptable range, obtain higher fund utilization ratio, thus effectively auxiliary power grid enterprises carry out investment in technological upgrading decision-making.The present invention takes full advantage of the quantized data that main transformer accumulates in O&M process, support the retired of assets full life management process by equipment O&M process data and scrap link, help lend some impetus to asset life cycle management horizontal coordination, the management lean level of enterprise.

As one embodiment of the present invention, in described step S101, described determinant attribute data comprise electric pressure, put into operation time and historic defects record.

As one embodiment of the present invention, in described step S102, adopt following formulae discovery major emergency ratio of defects:

$DR\left(t\right)=\frac{{\Σ}_{i=y_0}^{y_{\max }}{D}_t\left(i\right)}{{\Σ}_{i=y_0}^{y_{\max }}{S}_t\left(i\right)\×(y_{\max }-y_0+1)}$ Formula (1)

In formula: DR (t) is the major emergency ratio of defects of the main-transformer of the time limit t that puts into operation, y ₀, y _maxbe respectively the initial time of statistical shortcomings and terminate the time, D _ti () to be put into operation the defects count of time limit t for time i, S _ti () to be put into operation the number of devices of time limit t for time i, i is the time.

As one embodiment of the present invention, in described step S103, regression model is:

$y=\hat{b}{e}^{\widehat{ax}}$ Formula (2)

In formula, represent the growth rate of major emergency ratio of defects with the time limit that puts into operation, represent main transformer put into operation First Year (x=0) time overall fault rate, e is natural logarithm;

Adopt principle of least square method Confirming model parameter, that is:

$\min {\Σ}_{i=1}^n{(y_i-\hat{b}{e}^{\hat{a}{x}_i})}^2$ Formula (3)

In formula: x _i, y _ifor observed reading, i is observation number.

As one embodiment of the present invention, in described step S104, set up objective function and constraint condition comprises the following steps:

S104-1 sets different electric pressure major emergency ratio of defects weight, note electric pressure U _kmain transformer major emergency ratio of defects be ω (U _k);

It is N that S104-2 sets evaluation cycle, namely solve main-transformer after current year the 1st, 2 ... Replacement Strategy during N, the standard of judgement is because input situation replaced by main-transformer between the reduction degree of N+1 major emergency ratio of defects and evaluation cycle N;

S104-3 adds up all main-transformers the 1st, 2 ... the time limit t that puts into operation during N, the main transformer quantity of each electric pressure is respectively: C={ C ₁..., C _k... C _k, the categorical measure of electric pressure is K, the average price of each electric pressure main transformer: f={ f ₁..., f _k..., f _k;

S104-4 remembers that the set of main-transformer Z is { z (n, k, i) }, z (n, k, i,) be that the year of putting into operation of this main-transformer is limited to t (n, k at i-th main-transformer of 1 year kth electric pressure, i), whether this main-transformer is replaced and is designated as event E (n, k, i), if change this main-transformer, then E (n, k, i)=1; If do not change this main-transformer, then E (n, k, i)=0;

S104-5 is according to the ratio of following formulae discovery " main-transformer damage degree reduces degree/displacement expense ":

$\frac{\mathrm{\Δ}DR}{F}=\frac{{\Σ}_{n=1}^{N+1}{\Σ}_{k=1}^K{\Σ}_{i=1}^{C_k}(a_k{e}^{b_{k}t(N+1,k,i)}-a_k{e}^{b_k(N-n)})\×\mathrm{\ω}\left(U_K\right)\×E(n,k,i)}{{\Σ}_{n=1}^{N+1}{\Σ}_{k=1}^K{\Σ}_{i=1}^{C_k}{f}_k\×E(n,k,i)}$

S104-6 sets up objective function and constraint condition is as follows:

$\max u=max\frac{\mathrm{\Δ}DR}{F}$ Formula (4)

formula (5)

In formula, the ratio that u represents " main-transformer damage degree reduces degree/displacement expense ", n is year number, k is the sequence number of electric pressure sequence, and i is main-transformer sequence sequence number, and Δ DR represents that main-transformer damage degree reduces degree, F represents main transformer displacement expense, t (n, k, i) is the time limit that puts into operation at i-th main-transformer of 1 year kth electric pressure, E (n, k, i) represent whether i-th main-transformer of 1 year kth electric pressure replaces, as displacement, then E (n, k, i)=1, otherwise be designated as 0; a _kfor electric pressure is U _kmain-transformer major emergency ratio of defects main transformer put into operation First Year time overall fault rate, b _krepresent the growth rate of major emergency ratio of defects with the time limit that puts into operation, ω (U _k) for electric pressure be U _kmain transformer major emergency ratio of defects.

As one embodiment of the present invention, in described step S105, adopt implicit enumeration method to solve objective function and specifically comprise the following steps:

Step S105-1 first sounds out and solves, and when all main-transformers all meet constraint condition in displacement that year reaching maximum major emergency ratio of defects requirement maxdr, therefore is a solution, can obtains u ';

Step S105-2 using u ' as newly-increased constraint condition:

If desired value u < is u ', the solution of desired value u < u ' is not used in inspection and whether meets constraint condition and can reject;

If desired value u > is u ', using this desired value as new constraint condition, former newly-increased constraint condition is abolished;

Step S105-3 repeats step S105-2, updates filtercondition;

Step S105-4 enumerates all possible solution, obtains the optimal case of main-transformer Replacement Strategy.

Compared with prior art, the present invention has following significant effect:

The present invention by setting up main transformer major emergency ratio of defects forecast model, and according to equipment impaired reduction degree cost than optimum mode, in guarantee main transformer risk within the acceptable range, obtains higher fund utilization ratio.Thus effectively auxiliary power grid enterprises carry out investment in technological upgrading decision-making.The present invention takes full advantage of the quantized data that main transformer accumulates in O&M process, support the retired of assets full life management process by equipment O&M process data and scrap link, help lend some impetus to asset life cycle management horizontal coordination, the management lean level of enterprise.

Accompanying drawing explanation

Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.

Fig. 1 is schematic flow sheet of the present invention;

Fig. 2 is that difference of the present invention puts into operation the time limit each electric pressure main-transformer statistical conditions;

Fig. 3 is 220kV main-transformer major emergency ratio of defects of the present invention and the time limit fitting result that puts into operation;

Fig. 4 is the present invention's different technological transformation strategy credit requirement contrast table.

Embodiment

As shown in figures 1-4, be a kind of main-transformer Replacement Strategy formulating method based on major emergency ratio of defects of the present invention, comprise the following steps:

Step S101, obtain the determinant attribute data as whole main-transformers of research object, in the present embodiment, research object is the main-transformer Replacement Strategy of certain For Provincial Power Grid Corporation, therefore, collected data comprise the equipment account of the whole main-transformer data of certain For Provincial Power Grid Corporation, concrete determinant attribute data comprise the device id of main-transformer, put into operation the time, electric pressure, capacity, the historical defect data of price and 2007 ~ 2014 years, concrete attribute comprises the main-transformer ID that defect occurs, defect describes, the disfigurement discovery time, Level.

Step S102, according to the main transformer equipment account collected, the distribution situation of the main transformer electric pressure of this grid company as shown in Figure 2.The initial time of statistical shortcomings is 2007, terminating the time is 2014, calculate the time limit that respectively puts into operation major emergency ratio of defects (due to number of devices after the time limit 20 years of putting into operation very little, do not possess statistical significance, therefore the major emergency ratio of defects after the time limit 20 years of putting into operation wouldn't be calculated);

Adopt following formula, calculate the major emergency ratio of defects of each main-transformer at the time limit that respectively puts into operation:

$DR\left(t\right)=\frac{{\&Sigma;}_{i=y_0}^{y_{\max }}{D}_t\left(i\right)}{{\&Sigma;}_{i=y_0}^{y_{\max }}{S}_t\left(i\right)\&times;(y_{\max }-y_0+1)}$ Formula (1)

In formula: DR (t) is the major emergency ratio of defects of the main-transformer of the time limit t that puts into operation, y ₀, y _maxbe respectively the initial time of statistical shortcomings and terminate the time, D _ti () to be put into operation the defects count of time limit t for time i, S _ti () to be put into operation the number of devices of time limit t for time i, i is the time.

Step S103, the large urgent ratio of defects heavy to each main-transformer carries out regretional analysis with the time limit that puts into operation, set up major emergency and lack limit rate and the regression model of the time limit that puts into operation, as shown in Figure 3, through over-fitting, 220kV main-transformer major emergency ratio of defects with the regression model of the time limit that puts into operation is: y=0.020401e ^0.072x(in earlier stage when calculating major emergency ratio of defects, unit is item/(100 year) to this example, here needs to be further converted to item/(platform year)).Wherein, R ²=0.839, fitting degree is better.According to preceding method, other electric pressure major emergency ratio of defects of matching with the regression model of the time limit that puts into operation is respectively:

$y=\hat{b}{e}^{\widehat{ax}}$ Formula (2)

In formula, represent the growth rate of major emergency ratio of defects with the time limit that puts into operation, represent main transformer put into operation First Year (x=0) time overall fault rate, e is natural logarithm;

Adopt principle of least square method Confirming model parameter, that is:

$\min {\&Sigma;}_{i=1}^n{(y_i-\hat{b}{e}^{\hat{a}{x}_i})}^2$ Formula (3)

In formula: x _i, y _ifor observed reading, i is observation number.R is judged by examination ²with the numerical values recited of residual RMSE, determine the consistent degree between regression model and real data.

Step S104, according to " main-transformer damage degree reduces degree/displacement expense " maximization principle, sets up objective function and constraint condition:

In the implementation case, the setting of different electric pressure major emergency ratio of defects weight is determined according to the ratio of main transformer capacity average, and concrete outcome is as follows:

Electric pressure	500kV	220kV	110kV	35kV
					Quantity (platform)	224	563	2565	414
Total volume (MVA)	62656	103089.5	117226.5	2210.29
					Average size (MVA/ platform)	279.714	183.107	45.702	5.339
Grid loss coefficient	52.39	34.296	8.56	1

(table 1)

The price following (the relative value data of the main-transformer price of different electric pressure are only provided) of each electric pressure main transformer:

Electric pressure	500kV	220kV	110kV	35kV
					Relative price	20.066	15.182	4.733	1.0

(table 2)

Set up objective function and constraint condition is as follows:

S104-1 sets different electric pressure major emergency ratio of defects weight, note electric pressure U _kmain transformer major emergency ratio of defects be ω (U _k);

It is N that S104-2 sets evaluation cycle, namely solve main-transformer after current year the 1st, 2 ... Replacement Strategy during N, the standard of judgement is because input situation replaced by main-transformer between the reduction degree of N+1 major emergency ratio of defects and evaluation cycle N;

S104-3 adds up all main-transformers the 1st, 2 ... the time limit t that puts into operation during N, the main transformer quantity of each electric pressure is respectively: C={ C ₁..., C _k... C _k, the categorical measure of electric pressure is K, the average price of each electric pressure main transformer: f={ f ₁..., f _k..., f _k;

S104-4 remembers that the set of main-transformer Z is { z (n, k, i) }, z (n, k, i) is i-th main-transformer 1 year kth electric pressure, this main-transformer be limited to t (n, k, i) year of putting into operation, whether this main-transformer replaces is designated as event E (n, k, i), if change this main-transformer, then E (n, k, i)=1; If do not change this main-transformer, then E (n, k, i)=0;

S104-5 is according to the ratio of following formulae discovery " main-transformer damage degree reduces degree/displacement expense ":

$\frac{\mathrm{\&Delta;}DR}{F}=\frac{{\&Sigma;}_{n=1}^{N+1}{\&Sigma;}_{k=1}^K{\&Sigma;}_{i=1}^{C_k}(a_k{e}^{b_{k}t(N+1,k,i)}-a_k{e}^{b_k(N-n)})\&times;\mathrm{\&omega;}\left(U_K\right)\&times;E(n,k,i)}{{\&Sigma;}_{n=1}^{N+1}{\&Sigma;}_{k=1}^K{\&Sigma;}_{i=1}^{C_k}{f}_k\&times;E(n,k,i)}$

S104-6 sets up objective function and constraint condition is as follows:

Objective function: $\max u=max\frac{\mathrm{\&Delta;}DR}{F}$ Formula (4)

Constraint condition: formula (5)

In formula, the ratio that u represents " main-transformer damage degree reduces degree/displacement expense ", n is year number, k is the sequence number of electric pressure sequence, and i is main-transformer sequence sequence number, and Δ DR represents that main-transformer damage degree reduces degree, F represents main transformer displacement expense, t (n, k, i) is the time limit that puts into operation at i-th main-transformer of 1 year kth electric pressure, E (n, k, i) represent whether i-th main-transformer of 1 year kth electric pressure replaces, as displacement, then E (n, k, i)=1, otherwise be designated as 0; a _kfor electric pressure is U _kmain-transformer major emergency ratio of defects main transformer put into operation First Year time overall fault rate, b _krepresent the growth rate of major emergency ratio of defects with the time limit that puts into operation, ω (U _k) for electric pressure be U _kmain transformer major emergency ratio of defects.

Step S105, adopts implicit enumeration method to solve above-mentioned objective function, obtains main-transformer Replacement Strategy, specifically comprise the following steps:

Step S105-1 first sounds out and solves, and easily finds out, when all main-transformers all meet constraint condition in displacement that year reaching maximum major emergency ratio of defects requirement maxdr, therefore is a solution, can obtains u ';

Step S105-2 is using u ' as newly-increased constraint condition (desired value lower bound), and because objective function is maximizing, therefore when asking optimum solution, the solution of desired value u < u ' need not be checked and whether meets constraint condition and can reject;

Step S105-3 when desired value u > u ' time, using this desired value as new constraint condition, former newly-increased constraint condition is abolished;

Step S105-4 repeats step S105-2, S105-3, updates filtercondition;

Step S105-5 enumerates all possible solution, obtains the optimal case of main-transformer Replacement Strategy.

As shown in the table, following table is the main-transformer quantity of this For Provincial Power Grid Corporation 2015 ~ 2027 displacement:

Time

2015

2016

2017

2018

2019

2020

2021

2022

2023

2024

2025

2026

2027

500kV	0	0	0	3	4	1	0	3	3	9	3	11	13
														220kV	3	2	3	0	8	19	13	11	9	8	20	15	24
110kV	0	0	8	1	4	22	38	35	29	30	23	94	29
														35kV	5	0	0	0	3	2	2	0	3	2	0	3	7

(table 3)

Fig. 4 adopts other technological transformation strategy to compare with employing credit requirement of the present invention in the present embodiment.By relatively finding out, according to equipment deterioration reduction degree cost than optimum mode, in guarantee main-transformer risk within the acceptable range, higher utilization ratio can be realized.Utilize this method to formulate main-transformer Replacement Strategy, efficiently utilize the historical data of equipment O&M process, and taken into account risk and benefit balance.Realize asset life cycle management decision optimization in the mode of quantum chemical method, help lend some impetus to asset life cycle management horizontal coordination, the management lean level of enterprise.

Embodiments of the present invention are not limited thereto; according to foregoing of the present invention; according to ordinary technical knowledge and the customary means of this area; do not departing under the present invention's above-mentioned basic fundamental thought prerequisite; the present invention can also make the amendment of other various ways, replacement or change, all drops within rights protection scope of the present invention.

Claims (7)

1., based on a main-transformer Replacement Strategy formulating method for major emergency ratio of defects, it is characterized in that comprising the following steps:

Step S101, obtains the determinant attribute data of the whole main-transformers as research object;

Step S102, calculates the major emergency ratio of defects of each main-transformer at the time limit that respectively puts into operation:

Step S103, the large urgent ratio of defects heavy to each main-transformer carries out regretional analysis with the time limit that puts into operation, and sets up major emergency and lacks limit rate and the regression model of the time limit that puts into operation, adopt principle of least square method Confirming model parameter;

Step S104, according to " main-transformer damage degree reduces degree/displacement expense " maximization principle, sets up objective function and constraint condition;

Step S105, adopts implicit enumeration method to solve objective function, obtains main-transformer Replacement Strategy.

2. the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects according to claim 1, is characterized in that: in described step S101, and described determinant attribute data comprise electric pressure, put into operation time and historic defects record.

3. the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects according to claim 2, is characterized in that: in described step S102, adopts following formulae discovery major emergency ratio of defects:

$DR\left(t\right)=\frac{{\&Sigma;}_{i=y_0}^{y_{\max }}{D}_t\left(i\right)}{{\&Sigma;}_{i=y_0}^{y_{\max }}{S}_t\left(i\right)\&times;\left(y_{\max }-y_0+1\right)}$ Formula (1)

In formula: DR (t) is the major emergency ratio of defects of the main-transformer of the time limit t that puts into operation, y ₀, y _maxbe respectively the initial time of statistical shortcomings and terminate the time, D _ti () to be put into operation the defects count of time limit t for time i, S _ti () to be put into operation the number of devices of time limit t for time i, i is the time.

4. the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects according to claim 3, it is characterized in that: in described step S103, regression model is:

$y=\hat{b}{e}^{\widehat{ax}}$ Formula (2)

In formula, represent the growth rate of major emergency ratio of defects with the time limit that puts into operation, represent main transformer put into operation First Year (x=0) time overall fault rate, e is natural logarithm;

Adopt principle of least square method Confirming model parameter, that is:

$min{\&Sigma;}_{i=1}^n{\left(y_i-\hat{b}{e}^{\hat{a}{x}_i}\right)}^2$ Formula (3)

In formula: x _i, y _ifor observed reading, i is observation number.

5. the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects according to claim 4, is characterized in that: in described step S104, sets up objective function and constraint condition comprises the following steps:

S104-1 sets different electric pressure major emergency ratio of defects weight, note electric pressure U _kmain transformer major emergency ratio of defects be ω (U _k);

It is N that S104-2 sets evaluation cycle, namely solve main-transformer after current year the 1st, 2 ... Replacement Strategy during N, the standard of judgement is because input situation replaced by main-transformer between the reduction degree of N+1 major emergency ratio of defects and evaluation cycle N;

S104-3 adds up all main-transformers the 1st, 2 ... the time limit t that puts into operation during N, the main transformer quantity of each electric pressure is respectively: C={C ₁..., C _k... C _k, the categorical measure of electric pressure is K, the average price of each electric pressure main transformer: f={f ₁..., f _k, f _k;

S104-4 remembers that the set of main-transformer Z is { z (n, k, i) }, z (n, k, i) is i-th main-transformer 1 year kth electric pressure, this main-transformer be limited to t (n, k, i) year of putting into operation, whether this main-transformer replaces is designated as event E (n, k, i), if change this main-transformer, then E (n, k, i)=1; If do not change this main-transformer, then E (n, k, i)=0;

S104-5 is according to the ratio of following formulae discovery " main-transformer damage degree reduces degree/displacement expense ":

$\frac{\mathrm{\&Delta;}DR}{F}=\frac{{\&Sigma;}_{n=1}^{N+1}{\&Sigma;}_{k=1}^K{\&Sigma;}_{i=1}^{C_k}\left(a_k{e}^{b_{k}t\left(N+1,k,i\right)}-a_k{e}^{b_k\left(N-n\right)}\right)\&times;\mathrm{\&omega;}\left(U_K\right)\&times;E\left(n,k,i\right)}{{\&Sigma;}_{n=1}^{N+1}{\&Sigma;}_{k=1}^K{\&Sigma;}_{i=1}^{C_k}{f}_k\&times;E\left(n,k,i\right)}$

S104-6 sets up objective function and constraint condition is as follows:

Objective function: $\max u=max\frac{\mathrm{\&Delta;}DR}{F}$ Formula (4)

Constraint condition: formula (5)

In formula, the ratio that u represents " main-transformer damage degree reduces degree/displacement expense ", n is year number, k is the sequence number of electric pressure sequence, and i is main-transformer sequence sequence number, and Δ DR represents that main-transformer damage degree reduces degree, F represents main transformer displacement expense, t (n, k, i) is the time limit that puts into operation at i-th main-transformer of 1 year kth electric pressure, E (n, k, i) represent whether i-th main-transformer of 1 year kth electric pressure replaces, as displacement, then E (n, k, i)=1, otherwise be designated as 0; a _kfor electric pressure is U _kmain-transformer major emergency ratio of defects main transformer put into operation First Year time overall fault rate, b _krepresent the growth rate of major emergency ratio of defects with the time limit that puts into operation, ω (U _k) for electric pressure be U _kmain transformer major emergency ratio of defects.

6. the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects according to claim 5, is characterized in that: in described step S104, and the major emergency ratio of defects of different electric pressure adopts the ratio of capacity average to determine.

7. the main-transformer Replacement Strategy formulating method based on major emergency ratio of defects according to claim 6, is characterized in that: in described step S105, adopts implicit enumeration method to solve objective function and specifically comprises the following steps:

Step S105-1 first sounds out and solves, and when all main-transformers all meet constraint condition in displacement that year reaching maximum major emergency ratio of defects requirement maxdr, therefore is a solution, can obtains u ';

Step S105-2 using u ' as newly-increased constraint condition:

If desired value u < is u ', the solution of desired value u < u ' is not used in inspection and whether meets constraint condition and can reject;

If desired value u > is u ', using this desired value as new constraint condition, former newly-increased constraint condition is abolished;

Step S105-3 repeats step S105-2, updates filtercondition;

Step S105-4 enumerates all possible solution, obtains the optimal case of main-transformer Replacement Strategy.