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http://slidepdf.com/reader/full/00885695d1721a28ab9b0296909e 1/5

Comprehensive Energy-saving Potential Evaluationof Distribution Network Based on Analytical

Hierarchy Process(AHP)

ZHAO Zilan1,LIU Wenying1,XU Peng1

North of China Electric Power UniversityBeijing,China

[email protected], [email protected]

LIU Fuchao2,ZHOU Xichao2,WEN Zhiwei2

Gansu Electric Power Research InstituteLanzhou,Gansu,China

Abstract — Losses in distribution networks represent the single

largest consumption in any power system due to heavily loaded

conditions. It plays a role in loss minimization that working out

more effective measures to save energy. The application of Analytic

hierarchy process(AHP) in the analysis of energy-saving potential

for distribution network is proposed, which takes both devices

placement and parameters reconfiguration into consideration. The

proposed method of energy-saving potential could tap latent

potential of losses minimization and give optimism alternatives. The

losses in distribution networks reduce to a lower level after the

implement of measures and the instance as illustrated in this paper

proves the effectiveness of this method..

Keywords-distribution network; energy-saving measures;

energy-saving potential; electric energy loss

I. I NTRODUCTION

Nowadays, many problems exist in field of distributionnetwork in China, like unreasonable planning on transformersubstations and selection of cross-section of conductor, absenceof compensation apparatus, even some high-energy

transformers still in using. All these lead to a higher energyconsumption value[1]. Studies indicate that the electric energyloss cost in distribution network may be more than 50% of thatin the gird during the process of power system’soperation[2].Therefore, developing energy-saving potentialitiesin distribution network plays a significant role in reducingelectric energy loss of the grid[3].For this reason, the overallstudy of energy saving potentialities is turned into importantexploration in the area of electrical energy-saving.

So far, the research of distribution network energy-savingfocus on figuring out amount of energy-saving of some specificmeasures. Reference [4] evaluate the expected energy savingspace after application of new transformers. Reference [5]

takes CHANG AN, in DONG GUAN, for an instance andevaluates the energy-saving potentialities of five measures bytaking them in some typical distribution circuit. Then a methodof distribution network energy saving potential microscopicevaluation is proposed. Reference [6] analyzes the constructionof distribution network electric energy loss and givecorresponding strategies. Some quantitative analysis of eachkind of devices in distribution system has been done in[7],[8 ]and [9]. Reference [10] find out allocation optimum andeconomic operation of lines and transformers by means of

modeling. All the research above is about the calculation andanalysis of some specific measures in distribution network. Butit is merely that exploring the energy saving potentialities andcalculating amount of energy saving in distribution network atthe same time in most studies of this field. The paper analyzesthe potentialities of energy saving in distribution network

through the analytic hierarchy process and presentingcomprehensive evaluation of energy-saving measures in orderto provide technique foundation for developing comprehensiveenergy saving potentialities in distribution network.

II. THE E NERGY CONSUMPTION MECHANISM A NALYSIS

OF SINGLE ELEMENT I N DISTRIBUTION NETWORK

A.

Line

According to the Guide of calculation of grid energy loss,the line losses is

2 33 10 jf A I R T −

= × × ×

(1)

Where: R is the resistance of element,Ω

; T is running time,h;

f I is the current of element, A.

So, the electric energy loss of the line is proportional to the

line resistance R , and proportional to square of the operatingcurrent.

B.

Power Transformer

According to the Guide of calculation of grid energy loss,the no-load energy consumption of the transformer is

2

0 ( )avT

f

U A P T

U = × ×

(2)

Where: T A is the electric energy loss of transformer core,（kWh）;

0 P is the power of transformer no-load loss,( kW);

T is the running time of transformer, h; f

U is the transformer

tap voltage,(kV); avU is the average voltage, (kV).

The load energy consumption of the double windingtransformer is

Major science and technology project grants in GANSU Province,PROJECT ID: 1203GkDA009

978-1-4799-2522-3/13/$31.00 ©2013 IEEE

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2( ) jf

R k

N

I A P T

I = × × (3)

Where: R

A is the transformer load energy loss（kWh）; k P

is the power of transformer load loss,( kW); T is running time

of transformer, h; jf I is the operating current, A; N I is the

rated current, A.

The total amount of energy consumption of transformer is

T R A A A= + (4)

Therefore, the no-load energy consumption of thetransformer is proportional to the power of transformer no-loadloss, and proportional to square of the transformer operatingvoltage[11]; and the load energy consumption of the transformeris proportional to the power of transformer load loss, and proportional to square of the transformer operating current. Inaddition, the operating voltage and current of transformer arerelated to many factors such as the grid current operationmode[12].

How to develop the distribution network energy-saving potential from the integrated perspective, and at the same timeconsidering the equipment parameters and grid operation parameters on the influence of different elements energysaving, is the focus of this paper to consider.

III. COMPREHENSIVE E NERGY-SAVING POTENTIAL

EVALUATION OF DISTRIBUTION NETWORK BASED O N

A NALYTICAL HIERARCHY PROCESS(AHP)

A. Existing Energy-saving Measures of Distribution Network

1) Energy-saving measures of wire:The main energy-saving measures of wire are to replace the

energy dissipation wire and choose wires according toeconomic current density[13].

2) Energy-saving measures of transformer:The main energy-saving measures of transformer are to

replace the high energy dissipation transformers and distributetransformers reasonably[14].

3) Energy-saving measures of reactive power

compensation equipment:The main energy-saving measures of reactive power

compensation equipment are to reasonably distribute reactive power compensation equipment and increase the power factorand so on[15].

Therefore, changing the transmission elements are the mainenergy-saving measures for the distribution network. But dueto funding constraints and other limitations, operatorssometimes can’t change the grid planning measures likereplacing distribution network elements to reduce the energyconsumption in practice. In this case, they can significantlyreduce the energy loss in operation by means of adjusting the parameters settings, and optimizing grid operation mode

B. Energy-saving Potential Analysis Calculation of Distribution Network Based on AHP

1) Model and Process of AHP:AHP is the multi-objective approach combined with

qualitative and quantitative analysis, it can effectively analyzethe no-sequence relation of the target system levels, and itmakes the analysis process hierarchical and quantification. TheAHP model can be divided into three level:

a)

Highest level(Target level): the goal to achieve;

b) Middle level(Criterion level): the constraint objectsand evaluation criterions to achieve the goal;

c) Lowest level(Scheme level): the measures and schemeto achieve the goal;

The process of AHP as follows:

a) Set up the AHP model ;

b) Construct judgment matrix that is calculating the

index weight,and analysis the influence degree to energy

index,also it gets the energy-saving potential under the

different energy-saving measures.

c)

Consistency check, that is to determine evaluationindex have overall consistency;

d) Calculate the single scheduling matrix;

e) Calculate the all scheduling index weight and judge

the best measure and scheme of achieving the goal .

In this paper, choosing the comprehensive energy-saving potential as the target level, different energy-saving measuresas the scheme level, and the energy-saving index as thecriterion level. According to this, the paper established theenergy-saving potential evaluation of AHP model at first.

Figure 1. Energy-saving potential evaluation of AHP model.

As the Fig.1, we should construct the judgment matrix.Each element compared with others in the same level, theimportance to the higher level of different element can

represent through numeric, usually use 1, 2,……9 and their

reciprocal.Forming the judgment matrix A by considering the

influence of the criterion level to the target level:

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A B1 B2

B1 1 1

B2 1 1

Where the energy-saving index matrix B1 of replacing thehigh energy dissipation element is:

B1 C1 C2 C3 C4

C1 1 3 5 3

C2 0.3 1 7 3

C3 0.2 0.14 1 0.2

C4 0.3 0.3 5 1

Energy-saving index matrix B2 of optimizing grid operation parameters is:

B2 C1 C2 C3 C4

C1 1 1 0.14 2

C2 1 1 0.14 2

C3 7 7 1 5

C4 0.5 0.5 0.2 1

The index weight of each matrix as follows:

After normalized the weight vector for A matrix is

A=（0.5, 0.5）；

After normalized the weight vector for B1 matrix is

B1=（0.5, 0.3, 0.05, 0.15）；

After normalized the weight vector for B2 matrix is

B2=（0.1, 0.1, 0.72, 0.08）；

Therefore, the single scheduling matrix B of the scheme

level to the criterion level is:

0.5 0.3 0.05 0.15

0.1 0.1 0.72 0.08 B

⎡ ⎤= ⎢ ⎥

⎣ ⎦

So, the all scheduling index weight W which the

energy-saving measures of scheme level to the comprehensiveenergy-saving potential of target level is:

1 2 3 4( )

=

W A B ξ ξ ξ ξ = =i ，，，

（ 0. 3, 0. 2, 0. 385, 0. 115）

The results indicated that the load economic operation hasthe most energy-saving potential. In addition, the wireenergy-saving measure and the transformer energy-savingmeasure can save the more electric energy, and the reactive power compensation equipment has the least energy-saving potential. So we should advocate for adjusting the gridoperation parameters at first in the practice. Second, we can

replace the distribution network elements to reduce the electricenergy loss into consideration.

C. The energy-saving optimization strategy based on

energy-saving potential evaluation

From the analysis of above, we can get the conclusion thatthe electric energy loss of the distribution network elements are produced by the equipment parameters and grid operation parameters, and the energy-saving potential of grid systemeconomic operation is more than replacing the high energydissipation element. According to this trait, we can get theenergy-saving optimization strategy of distribution networkwhich combined the existing element energy-saving measures:

Figure2. The flow chart of energy-saving optimization strategy indistribution network.

This energy-saving optimization strategy of distribution

network can reduce the electric energy loss by optimizing gridoperation parameters at first. When the amount of electricitysaving can’t reach the goal, we should consider to replace thehigh energy dissipation element. It’s more practical for thestrategy to take equipment cost as a constraint condition at thesame time.

IV. EXAMPLE VERIFICATION

We took the low and medium voltage level distributionnetwork in Gansu province as the analysis object,and thenselected 7 bus and 2 transformer from this region. The sample proportion is about 15%, and it almost covers the feature parameter range in this region.The example verification wason the basis of the most large load days in current year,and it

analyzed standard target of achieving the two 0.3%energy-saving index through the PSASP simulation.Theenergy-saving technology simulation results are as follows.

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TABLE I. REPLACING THE HIGH ENERGY DISSIPATION WIRES

Wire

name

Original wire

models

New wire

modelsLength/km

Network loss

rate/%

L1 LYJ-185 LYJ-240 1.55 3.54

L2 LYJ-195 LYJ-240 1.15 3.96

L3 LYJ-120 LYJ-210 0.65 3.04

L4 LYJ-120 LYJ-210 0.4 3.27

TABLE II. REPLACING THE HIGH ENERGY DISSIPATION TRANSFORMERS

Transformer

name

Original

transform

models

New transform

models

Network loss

rate/%

Lanzhou B1 S7 S13 4.55Taoshucun B1 S9 S13 4.56

Dingxi B1 S9 S11 4.54

TABLE III. THE REACTIVE POWER COMPENSATION EQUIPMENT

nameCompensation

point

Compensation

position

Compensation

capacity

Network

loss

rate/%

1 Lanzhou B1 10kV pole 300kvar 5.31

2 Taoshucun B1 10kV pole 3 *350kvar 5.03

3 Dingxi B1 10kV pole 3 *200kvar 4.93

TABLE IV. THE LOAD ECONOMIC OPERATION

The load economic operationNetwork loss rate/%

2.96

So, we can get results from the energy-saving technologysimulation that the load economic has the most energy-saving

potential, and the wire energy-saving measure、the transformerenergy-saving measure can save the more electric energy, thereactive power compensation equipment has the leastenergy-saving potential.

TABLE V. THE ELECTRIC E NERGY SAVING PROPORTION OF THE

DIFFERENT E NERGY-SAVING MEASURES WHEN ACHIEVING THE I NDEX I N

2012

Energy-saving measures

Electric

energy

saving

proportion

Replacing

the high

energy

dissipation

element

Line reconstruction 33%

Transformer reconstruction 29%

Installation of reactive power

compensation equipment16%

Optimizing

grid

operation

parameters

Adjusting the operating

voltage reasonable10%

Economic operation of the

load11%

Harmonic elimination 1%

In this case, the amount of electric energy saving reached

the 0.3014% of the electricity sales and the 0.3005% of themost electricity load in the last year.

If the Gansu province applied the energy-savingoptimization strategy of distribution network which putforward from this paper, optimized grid operation parameters atfirst and then replaced the high energy dissipation element, wecan trough the simulation get the electric energy saving proportion of the different energy-saving measures when

achieving the two 0.3% energy-saving index in this strategy, asthe Table VI shows.

TABLE VI. THE ELECTRIC E NERGY SAVING PROPORTION OF THE

DIFFERENT E NERGY-SAVING MEASURES WHEN ACHIEVING THE I NDEX I NTHE STRATEGY

Energy-saving measures

Electric

energy

saving

proportion Replacing

the high

energy

dissipation

element

Line reconstruction 19%

Transformer reconstruction 15%

Installation of reactive power

compensation equipment12%

Optimizing

grid

operation

parameters

Adjusting the operating

voltage reasonable23%

Economic operation of the

load25%

Harmonic elimination 6%

From the Table VI we can see that the amount of electricenergy saving reached 0.3032% of the electricity sales and0.3017% of the most electricity load under the energy-savingoptimization strategy of distribution network. Therefore, theamount of electric energy saving can be significantly increased

by the comprehensive energy-saving potential evaluation andthe energy-saving measures optimization.

V. CONCLUSION

• The electric energy loss of distribution network iscaused by two reasons, one is produced by theequipment parameters and the other is produced bygrid operation parameters as the load non-economicoperation. The existing energy-saving measures ofdistribution network in our country is about the singleelement’s energy-saving measures in addition withcumulating the all amount of the electricenergy-saving. It need to analyze the comprehensiveamount of energy-saving.

• This paper focuses on the whole distribution network,and using the AHP to analyze comprehensiveenergy-saving potential of distribution network, andthe comprehensive energy-saving potential ofvarious measures were simultaneously considered fromtwo angles of optimizing the power operation parameters and replacing the equipment

• This paper proposes a new energy-saving optimizationstrategy based on the energy-saving potentialevaluation of distribution network, which combines theactual grid operation and calculating the electricenergy-saving potential evaluation in process. It is proved to increase the amount of electricity saving ofdistribution network significantly by the exampleverification at last.

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