Chunjie Li

Huiru Zhao

Tianyou Li

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 C I R E D 21st  International Conference on Electr ic ity Dis tr ibution  Frankfurt, 6-9 June 2011 
 
Paper 0596 
 
 
Paper No  0596  1/4 
STUDY ON THE ECONOMIC LOSS AND ITS EVALUATION METHODS OF SHORT 
INTERRUPTION 
 
 
Tianyou LI                                                         Huiru ZHAO                                                Chunjie  Li 
Fujian Electric Power Company           North China Electric Power University       North China Electric Power University 
ltyxm@163.net                                          huiruzhao@163.com                                   Lichunjie518@sohu.com 
Dachang OU                                                                Liwen Fu  
North China Electric Power University                            North China Electric Power University 
oudachang123@163.com                                                     fuliwen88@163.com 
 
ABSTRACT 
Short interruption means that the outage lasts less than 3 
minutes. With social development and digital high-tech 
equipments widely applied, the economic losses caused by 
short interruption are serious and lead to significant 
social influences. Thus, it is necessary to make research 
on the losses caused by short interruption. In order to 
show the features and serious social impacts of short 
interruption, based on the concept and loss structure of 
short interruption ， the quantify method of short 
interruption losses and evaluation index were proposed. 
According to losses and occurring frequencies of short 
interruption, the danger of short interruption was 
analyzed. 
1. INTRODUCTION 
By the NO.DL/T836 document, published in 2010. -- 
“Reliability Evaluation Regulations of Power Supply in 
Power System”, short interruption is an interruption 
whose time duration is within 3 minutes. According to the 
power quality investigation made by Leonardo Energy, 
there were 15 billion pounds losses that occurred in 
industry every year, among them, 60% were caused by 
Voltage sag or Short Interruption
 [1]
. 
Thus, this study is helpful to understand short interruption 
features and learn the serious made by short 
interruption .The frequencies of short interruption is 
higher, the losses of users is larger
 [2]
. Meanwhile, owning 
to the interruptible load price and high reliability price 
depending on users’ losses , study on the losses of short 
interruption could make a contribution to decision-making 
of these kinds of prices and to city grid improving. 
Short interruption was common phenomenon in city grid, 
but studies on it were only appeared in few literatures. 
Contrary, there were many studies and achievements on 
general interruption. Reviewing these studies, the 
estimation methods of interruption losses can be divided 
into direct one and indirect one. Direct estimation 
methods contain four types: (1) Build ing losses function 
by questionnaire survey
 [3,4]
; (2) Estimating  losses by 
IEAR index
[5]
; (3) Building losses function by simulation 
curve
[6]
; (4) Calculat ing losses by neural network and 
fuzzy logic model
[7- 9]
. Also, ind irect estimation method 
includes three measures: (1) Calculating losses by the 
quantity of power generation
 [10.11]
; (2) Estimating losses 
by mult iplying average electricity price
 [12 .13]
; (3) 
Estimating  losses by input-output
 [14]
. Generally, IEAR 
and ICPE were taken as the evaluation index of 
interruption losses
 [15]
. 
These methods and achievements could provide important 
references for short interruption study. In this paper, short 
interruption losses function of power users will be built by 
questionnaire survey. Meanwhile, whether the IEAR, 
ICPE can  be used to evaluate short interruption will be 
discussed. 
2. SENSITIVE USERS AND SHORT 
INTERRUPTION INFLUENCES 
The losses caused by power interruption depended on 
features of users' devices. For example, programmable 
controller and frequency conversion speeder will be 
damaged by power interruption of several frequencies or 
voltage sag; production line of integrated circuit chip, 
computer system of bank and stock centre will be broken 
seriously by power interruption or voltage sag, which time 
duration was over one frequency current. Actually, these 
sensitive instruments were widely applied in various 
 C I R E D 21st  International Conference on Electr ic ity Dis tr ibution  Frankfurt, 6-9 June 2011 
 
Paper 0596 
 
 
Paper No  0596  2/4 
industries, such as, auto-mobile manufacture, bank, IT, 
rubber, plastic, text ile, metallu rgy, chemical fibre, 
pharmaceutical, electronic industries etc. Meanwhile, 
some public utilities, government and military agencies, 
for example, hospital, international conference and key 
lab, were also sensitive to short interruption
 [16]
. Thus, 
these power users, who will suffer large economic, 
political and social losses in short interruption, were 
called  sensitive users. And sensitive users were divided 
into four groups in this paper; they were industry, 
business, government and public. By taking investigation 
on users, the structure of short interruption losses was 
showed in Table1. 
Tab.1 Structure of different users’ short interruption losses 
Type Short interruption losses 
Direct losses Indirect losses 
Industry Product line interrupted 
Production discarded 
Product equipment broken  
Cost of equipment maintenance 
Compensation for dangerous  byproducts 
Damage on enterprise reputation 
Business Instruments broken 
Business operation disturbed 
Important data lost 
Service quality low 
Enterprise reputation lost 
Compensation for customers  
Government  Devices damaged 
Government affairs interrupted 
Key literature and data lost 
Work efficiency low 
Government reputation damaged  
Cost of stable society 
Public  Equipment broken  
Losses on public activ ities  
Losses on social normal income 
Cost of reality measures 
Compensation for customers  
Institution reputation damaged 
 
3. SHORT INTERRUPTION LOSSES 
FUNC TION OF SENSITIVE USERS 
3.1 Building function  
Drawing on the experiences of questionnaires estimation  
method, we will develop the users’ losses functions for 
different sensitive users by statistics of questionnaire. In  
order to establish the functions , three messages were 
required, i.e . users’ electric load, interruption and users’ 
expense, among them, electric informat ion can get from 
power company; expense data should be estimated by 
function. The specific method was showed as follows: 
(1)Classify sensitive users and design questionnaires of 
different sensitive users 
(2)Take investigation on users’ short interruption losses by 
questionnaires 
Assuming that short interruption occurred in peak load, 
and users’ losses  increased in direct ratio with users' 
power load. The value of short interruption losses for 
different users in different units, 0.05s, 3s、30s、1 min、
2 min、3min, can get  from the user’s reports   o r estimate 
by statistics. Then, each Customer Damage Function in  
different units can be gotten as follows: 
max
)(
)(
P
tCOST
tCDF 
                    (1) 
In function（1） , CDF (t) is each user's losses in peak 
load, Yuan/kW; COST (t) is each user's losses in different  
units, Yuan; Pmax is each user’s peak load, kW. 
(3)According to formula (1), Sector Customer Damage 
Function could be built as follows: 
i
n
x
x
i
n
tCDF
tSCDF
i

 1
)(
)(
               (2) 
In function（2）, it  shows the relationship between sector 
users 'losses and short interruption time duration. SCDF(t) i 
meant i sector users’ losses in peak load, Yuan/kW; ni  
meant numbers of i sector users. 
(4)Depending on SCDF, each kinds of users’load rate 
per year and power consuming proportion, composite 
customer damage function is built, it shows the 
relationship about composite customers’ losses  in different  
units of outage.  




m
i i
ii
L
tSCDFC
tCCDF
1
)(
)(
        (3) 
 C I R E D 21st  International Conference on Electr ic ity Dis tr ibution  Frankfurt, 6-9 June 2011 
 
Paper 0596 
 
 
Paper No  0596  3/4 
In function（3） , m means the numbers of user 'type, Ci 
means i user’ power consuming proportion; Li means i 
user’ load rate. 
This paper made a numerical study based on X city, A  
coast city in Southern China .The related losses functions 
(2), (3) were built by statistics. The losses results were 
showed in table 2. 
Tab.2 Short interruption losses function of X city 
Time 
duration 
(s) 
SCDF(t) of 
Industry 
（yuan/kw）  
CCDF(t) 
（yuan/kw）  
0.05s  1.17 1.24 
3s 4.28 4.25 
30s  10.89 13.85 
60s  20.02 31.01 
120s 28.79 45.39 
180s 35.27 52.54 
3.2 Analysis on short interruption losses 
In order to study the growth states of losses in different  
units of outage, the serious of short interruption losses in 
industry was showed. Dealing with related statistics, 
losses distribution and simulat ion curve can be seen in 
figure1, SCDF represented unit losses of industry users, 
yuan/kW; t represented time duration of short interruption. 
Fig.1 Short interruption distribution and simulation curve 
SCDF(t) of industry users can be gotten as follows: 
4156.098994.18)( ttSCDF          (5) 
Function (5) derivation, 
5814.08922.7)(  ttSCDF          (6) 
From function (6), the value was always bigger than 0, it  
meant that the losses of short interruption would become 
more serious with the t ime continuing. Because of (6) was 
decreasing function, marg inal interruption losses of 
industry were decreased. In other word, the addition of 
short interruption cost will g radually reduce with the 
duration time increasing. In figure1, the point of 60s was 
demarcat ion. When the time duration was less than 60s, 
the losses grew faster; growth became slowing down when  
it was more than 60s. Therefore , if short interruption can  
be stopped in 60s, large losses can be avoided effectively. 
 Losses in unit time, called LSCDF, as follows: 
5814.0*98994.18
)(
)(  t
t
tSCDF
tLSCDF     (7) 
From function (7), it showed that losses in unit time were 
smaller, when total losses of industry user were bigger. It  
could be concluded that frequent short interruption will 
bring larger losses to industry sensitive users
[2]
. 
4. EVALUATION OF SHORT INTERRUPTION 
4.1 Evaluation Index 
The severity of short interruption main ly appears in high-
frequency and high losses, they can be taken as evaluation  
index of short interruption. Frequency of short interruption, 
IEAR and ICPE can be used to evaluate the severity of 
short interruption, the functions were as follows: 
(8) 
 
  (9) 
Among that, ∑ COST meant total losses of society 
interruption, yuan; ∑ LEP meant total power quantity 
losses of society interruption, kWh; N meant the happen 
times of society interruption, ci. 
4.2 Empirical analysis 
According to related statistics, we taken an evaluat ion on 
short interruption of X city. Compared short interruption 
with general interruption by related indexes, such as IEAR, 
ICPE and so on, the severity of short interruption and 
general interruption could be seen in table3.  
 
 
COST
IEAR
LEP



COST
ICPE
N


 C I R E D 21st International Conference on Electr ic ity Dis tr ibution  Frankfurt, 6-9 June 2011 
 
Paper 0596 
 
 
Paper No  0596  4/4 
Tab. 3 Evaluation index between short interruption and general interruption 
Type 
Times
（ci）  
Total  
 time 
duration
（min）  
Total power 
quantity losses
（kWh）  
Total 
interruption 
losses 
（yuan） 
IEAR 
(yuan/kW） 
ICPE 
（yuan/ci） 
General 
interruption 
73 1972 79783.88 12452542.21 156.08 170582.77 
Short 
interruption 
50 9.3185 1308 2537419.66 1939.92 50748.39 
Proportion 
of Short 
interruption 
0.41 0.0047 0.016 0.169 / / 
 
From tab.3, there were several rates about short 
interruption VS general interruption. For instance, rate of 
times was 41%,rate of time duration was 0.47%, rate of 
power quantity losses was 1.6%, rate of interruption 
losses was16.9% .Among them, IEAR of short 
interruptionwas12.4 times bigger than general 
interruption, reach  1939 yuan/kWh. Thus, the losses of 
short interruption were very  serious. And also, it can be 
seen that these evaluation indexes are available  to remark 
severity of short interruption. IEAR was more effective 
than ICPE in evaluated on short interruption.  
5. CONCLUSIONS 
In this paper, we summarized the various sensitive users’ 
economic losses structure of short interruption and 
estimated short interruption losses of X city. Based on the 
related analysis, features of short interruption were found, 
namely that “high-frequency, high-losses, fast-happen" 
Compared with general interruption, the severity of short 
interruption was appeared. Meanwhile, by contrast with 
ICPE, it was known that IEAR was useful to evaluation 
of short interruption. 
 
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STUDY ON THE ECONOMIC LOSS AND ITS EVALUATION METHODS OF SHORT INTERRUPTION

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STUDY ON THE ECONOMIC LOSS AND ITS EVALUATION METHODS OF SHORT INTERRUPTION

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