Аnalysis of Domestic and Foreign Experience in Rationing the Reliability of Power Distribution Networks

The MAIN JOURNAL for POWER GRID SPECIALISTS in RUSSIA

power supply

Аnalysis of Domestic
and Foreign Experience
in Rationing the
Reliability of Power
Distribution Networks

The paper analyzes domestic and foreign experience and

compares the different countries approaches to rationing the

power distribution networks reliability. The main indicators

of power supply reliability in different countries with respect

to outages, approaches for planned values determination and

clustering of networks with similar characteristics are con-

sidered. Understanding the basic principles of power distribu-

tion network reliability regulation applied in foreign countries

allows specialists to identify best practices and adapt them

to domestic conditions.

Dmitry Gvozdev,

First Deputy General Director –
Chief Engineer, PJSC Rosseti
Moscow Region

Dmitry Gabdushev,

Leading specialist of the Power
System Modes Department,
PJSC Rosseti Moscow
Region

Rostislav Goenko,

Senior Laboratory Assistant of
the Department of Theoretical
Foundations of Electrical
Engineering, National
Research University “Moscow
Power Engineering Institute”

Daria Klimkina,

Assistant of the Department
of Theoretical Foundations
of Electrical Engineering,
National Research University
“Moscow Power Engineering
Institute”

Dmitry Buyankov,

Chief

Expert of the Power System
Modes Department, PJSC
Rosseti Moscow Region

Artem Vanin,

Associate

Professor of the Department
of Theoretical Foundations
of Electrical Engineering,
National Research University
“Moscow Power Engineering
Institute”, Ph.D.

istribution  networks  carry  out  the
transmission of electric power from
large  power  centers  (35-220  kV
substations  or  power  plants)  to

a large number of consumers. Ultimate con-
sumers have small load power and are dis-
tributed over a large area. In this regard,
power distribution networks have a complex
multidivisional structure and a hierarchical
design concept.

Regulatory authorities in diﬀ erent coun-

tries apply their own approaches to stan-
dardizing reliability and develop their own pri-
orities. Approaches for regulating distribution
network reliability, investigated in this paper,
include a comparison between jurisdictions
in Russia, the UK, Italy, the Netherlands and
the USA (California and New York states).

The analysis carried out in this article is

useful in developing the regulatory frame-
work. The results of the comparative analysis
can be used in the development of new regu-
latory documents. It will create more eﬀ ective
rules and standards for regulating the reliabil-
ity of distribution networks in Russia.

When analyzing the experience of reliabil-

ity standardization, comparison was carried
out according to the following criteria:

– power supply reliability indicators;

– accountable outages;

– determination of reliability indicators

planned values;

– clustering networks with similar charac-

teristics.

EP Shanghai 2023

Special issue, November 2023

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RELIABILITY INDICATORS

Reliability  of  power  supply  is  characterized  by  the
interruptions  in  power  supply  to  consumers,  its
frequency  and  duration.  A  large  number  of  diﬀ erent
indicators can be used to represent them numerically.
A  complete  list  of  indicators  is  given  in  the  IEEE  Std
1366-2012  standard  [1].  The  most  commonly  used
indicators are, as follows:

– SAIFI

(System Average Interruption Frequency In -

dex)

– an indicator of the average frequency of long-

term interruptions in the electric power transmission
to the delivery point or per consumer. It is deﬁ ned as
the ratio of all long-term power supply interruptions
during the billing period to the number of supply
points or consumers:

SAIFI =



(1)

– SAIDI

(System Average Interruption Duration In

dex)

– an indicator of the interruption average

duration  in  the  electric  power  transmission  to  the
delivery  point  or  per  consumer.  It  is  deﬁ ned  as
the  ratio  of  duration  of  all  long-term  power  supply
disruptions  during  the  billing  period  to  the  number
of supply points or consumers:

SAIDI =



(2)

– CAIDI

(Customer Average Interruption Duration

Index)

– an indicator of the average duration

of  power  supply  restoration.  It  is  deﬁ ned  as  the
ratio  of  total  duration  of  all  long-term  power
supply  disruptions  to  all  long-term  power  supply
disruptions for the billing period. Also equal to the
ratio of SAIDI to SAIFI:

СAIDI =



= SAIDI / SAIFI.

(3)

– MAIFI

(Momentary Average Interruption Fre-

quen cy Index)

– an indicator of the average

frequency of short-term interruptions in the
electric power transmission to the delivery point
or per consumer. It is defined as the ratio of all
short-term power supply interruptions during the
billing period to the number of supply points or
consumers:

MAIFI =



(4)

The following notations are used in the given for-

mulas (1)-(4):

– number of disconnected consum-

ers during the

-th technological disruption;

– dura-

tion of power supply disruption to consumers during
the

-th technological disruption;

– the total num-

ber of consumers or delivery points in the network,
reliability indicators are determined for;

– number

of short-term power outages;

– number of discon-

nected consumers during the

-th short-term power

outage.

IEEE Std 1366-2012 [1] classiﬁ es power outages as

short-term if they last less than 5 minutes and as long-
term if they last for more than 5 minutes. The minimum
duration of a long-term power supply interruption,
established by regulations, may diﬀ er in diﬀ erent
countries.

The RUSSIAN FEDERATION

Power supply reliability indicators

The indicator of the average interruption fre-

quency while electric power transmission to the



SAIFI

delivery point and the indicator of the average

interruption duration while electric power transmis-
sion to the



SAIDI

delivery point, analogues SAIFI

and SAIDI, are used in Russia for reliability indica-
tors standardization.

Accountable outages

In accordance with the guidelines for calculating

the  reliability  level  [2],  interruptions  in  the  transmis-
sion  of  electric  power  to  consumers  as  a  result  of
technological  violations  at  the  facilities  of  the  grid
operator  are  considered  to  calculate  reliability  in-
dicators.  These  outages  must  last  longer  than  the
automatic  power  restoration  time.  The  exception  is
when  the  grid  operator  is  not  responsible  for  power
outages.

Planned outages are not taken into account in

the main reliability indicators. The termination of
power transmission to consumers during repair
work is characterized separately by



SAIDI,rep



SAIFI,rep

indicative parameters.

Determination
of reliability indicators planned values

When planning tariffs, long-term regulatory

para meters are established. These parameters for
calculating long-term prices (tariffs) are established
for a long-term regulatory period.

Long-term regulation period is a period of at

least  5  years.  Long-term  regulation  parameters
are  calculated  for  this  period.  The  long-term  reg-
ulation  period  is  divided  into  regulation  periods  of
12 months [3].

When forming planned values of reliability in-

dica tors for territorial grid organizations, the meth-
od of com paring analogues is used. This method
is based on comparing the performance indicators
of territorial network organizations that have com-
parable economic and (or) technical characteristics
and (or) operating conditions [2].

For the first year in the long-term regulation pe-

riod, the planned values of the



,SAIDI

and



,SAIFI

indi-

cators are determined based on:

– the minimum value of the reliability indicators

actual value for the previous year and actual
average values of the reliability indicators for the
three previous years;

– a one-time improvement of the reliability indicators

minimum value using the reliability indicators
im prove ment rate.
For the second and subsequent calculation periods

of the long-term regulation period, the planned values
of reliability level indicators are determined using the
following formulas:





,+1,SAIDI



,SAIDI

· (1 –

,SAIDI

(5)





,+1,SAIFI



,SAIFI

· (1 –

,SAIFI

(6)

where



,SAIDI



,SAIFI

– the planned values estab-

lished by the regulatory body for the reliability level
indicator for the estimated regulation period (

) for

territorial grid organizations (TGO);

,SAIDI

,SAIFI

–

improvement rate of the reliability level indicator for
the network organization of group

;

– TGO group

number for this reliability indicator. It is important to
note that the TGO clustering by



,SAIDI

and



,SAIFI

in-

dicators varies.

The procedure for calculating the planned values

of indicators is given in Order No. 1256 of the Ministry
of Energy of the Russian Federation dated November
29, 2016 [2].

Clustering networks with similar
characteristics

Basic values of reliability indicators are estab-

lished for TGO groups that have characteristics and
(or) operating conditions comparable to each other
based on the method of comparing analogues. Vari-
ous clusterings are used for



,SAIDI

and



,SAIFI

indi-

cators. TGO clustering signs and basic values of
reliability indicators for groups are given in Order of
the Ministry of Energy of the Russian Federation No.
976 dated October 18, 2017 [4]. The main clustering
criteria are as follows: length of power transmission
lines, cable lines proportion, number of switching de-
vices, average summer temperature (more than 20°C
/ less than 20°C), load density, number of transmis-
sion points.

GREAT BRITAIN

Power supply reliability indicators

The main reliability indicators are CI and CML.

These  indicators  have  the  same  meaning  as  SAIFI
and  SAIDI.  CI  –  number  of  outages  per  year  per
100  consumers  (100×SAIFI);  CML  –  average  dura-
tion of power outage per year per consumer (SAIDI).

Accountable outages

When regulating reliability, both emergency and

planned outages are taken into account. In this
case, planned outages are taken into account with
a weighting coefficient of 0.5.

When determining the CI indicator, outages due

to violations in adjacent systems are not taken into
account. When calculating the CML indicator, 10%
of outages due to violations in adjacent systems are
taken into account.

When calculating reliability indicators, outages

lasting more than 3 minutes are taken into account.
Outages lasting less than 3 minutes are recorded by
an indicator.

When calculating reliability indicators, outages

caused by abnormal external conditions are not taken
into account. If the daily CI is 8 times higher than the
average daily value for 10 years, then such a day is
classified as a day with abnormal external conditions.
Also, outages due to accidents that disrupted the
power supply to more than 25.000 consumers are not
taken into account.

Determination
of reliability indicators planned values

Target indicators are determined for a long-term

regulatory period (at least 5 years) [7].

For the first year of the long-term regulation

period, CI and CML are determined as the minimum
value of:

– average company CI/CML performance for the

last 3 years;

– he company's CI/CML targets for the last year of

the previous long-term regulatory period.
For the last year of the long-term regulation period,

CI and CML are determined as the minimum value of
the following indicators:

– baseline targets calculated by the regulatory

authority;

– the company's CI/CML targets for the last year of

the previous long-term regulatory period.
If the targets for the first and the last year are

different, then the CI/CML targets for the interim
years change in equal increments each year.

When calculating basic targets, the power

distribution network is divided into groups, targets
are determined for subsystems, and then these
indicators are combined to obtain the entire company
target.

Actual reliability indicators of the power dis-

tribution  network  are  calculated  as  a  basis  for
determining the basic target indicators. The methods
for setting targets differ for each subgroup. In some
cases,  targets  are  based  on  the  performance  of
individual  systems,  and  in  others  on  the  average
performance of all systems in a subgroup. Indicators
are determined based on four years observation to
reduce  the  effect  of  random  deviations.  A  longer
interval  is  not  used.  Otherwise,  the  increase  in
reliability indicators over recent years would not be
taken into account.

Low voltage (LV) networks (up to 1 kV)

At the low voltage level, grid companies have

little  ability  to  influence  the  reliability  of  the  power
supply,  so  the  baseline  CI  and  CML  are  set  to  the
current  values  for  each  company.  For  companies
with  low  reliability  scores,  a  target  CML  of  75%  of
the national average has been set.

Medium voltage (MV) networks (1 to 20 kV)

For medium voltage networks, targets are set

based on the following factors:

– average number of power supply disruptions per

1 km of power network;

– average number of consumers disconnected due

to one technological violation, in relation to the
number of the feeder consumers;

– average and first quartile values of the CI/CML

(CAIDI) indicator.
The baseline targets for medium voltage networks

are based on the average performance of all network
companies in one subgroup.

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EP Shanghai 2023

Special issue, November 2023

High voltage (EHV) networks (from 20 to 132 kV)

Power networks of this voltage class experience

quite a few outages in one year and their performance
can  vary  greatly  from  year  to  year.  In  this  regard,
targets  for  this  subgroup  are  calculated  based  on
the  average  performance  of  each  company  over  the
past  10  years.  Once  targets  have  been  determined
for each subgroup, they are combined and targets are
set for each individual company.

The target for planned outages is deﬁ ned as

a three-year moving average with a two-year lag using
the following expression:

Planned target

year



(Planned Perf

year

–4

+ Planned Perf

year

–3

+ Planned Perf

year

–2

) / 3.

The maximum permissible duration of a consumer

outage is 12 hours.

Grid companies may not be interested in improving

the reliability of power supply to consumers in areas
where  outages  aﬀ ect  a  small  number  of  consumers
[5].  This  usually  applies  to  sparsely  populated  rural
areas.  In  order  to  stimulate  increased  reliability  of
power  supply  to  these  consumers,  the  regulatory
body introduces the concept of a consumer with low
reliability.

Low reliability customers are those who experience

an average of at least four outages per year over
a three-year period (i.e. 12 or more outages in three
years) [6].

In the UK, a fund has been created to improve

the power supply reliability of consumers with low
reliability. Grid companies receive compensation for
investments in improving power supply reliability of
consumers with low reliability from this fund.

Clustering networks with similar
characteristics

Distribution networks are divided into voltage

groups: LV (up to 1 kV), HV (1 to 20 kV), EHV (20 to
132 kV) and 132 kV. Medium voltage (MV) networks
are then divided into subgroups based on the follow-
ing  criteria:  percentage  of  overhead  lines,  length  of
lines,  number  of  connected  consumers.  Target  indi-
cators are calculated separately for each group, and
then  combined  into  a  common  indicator  for  the  grid
company.

ITALY

Power supply reliability indicators

Targets are set for SAIDI and SAIFI indicators.

Accountable outages

To calculate SAIDI and SAIFI, power supply

interruptions  lasting  from  3  minutes  to  8  hours  are
taken into account. Outages not related to disruptions
in  the  power  distribution  network  or  caused  by
abnormal  weather  conditions  are  not  taken  into
account when calculating reliability indicators.

MAIFI is used as an indicative value reflecting

the frequency of outages lasting from 1 second to
3 minutes.

Determination
of reliability indicators planned values

Long-term targets are set for all power distribution

networks. The long-term regulation period is 4 years.
The basic values of target indicators are set as
a certain percentile of the indicators for the previous
long-term regulation period.

The baseline SAIDI target for rural and suburban

networks is deﬁ ned as the 10% percentile, for urban
networks – as the 30% percentile of SAIDI values for the
previous long-term regulatory period. SAIFI's baseline
targets correspond to the 20 and 30% percentiles.

At the beginning of the long-term regulatory pe ri-

od, each distribution company sets its own reliability
targets for each year. These indicators are determined
based on data for the network company for the previous
two years and basic target indicators.

To distribute target indicators by years, the im-

prove ment rate coeﬃ cient is used. It is calculated as
follows:

– for SAIDI to achieve the baseline target within

8 years, but not less than 2%;

– for SAIFI to achieve the baseline target within

12 years, but not more than 6%.
Feeders with reliability scores 1.5 times worse

than the baseline targets are classified as low
performing power networks. First of all, network
companies are en couraged to improve the reliability
of such networks [8].

Clustering networks with similar
characteristics

Networks are combined into three groups

depending on load density: rural, suburban and urban.

NETHERLANDS

Power supply reliability indicators

The reliability of power transmission is cha rac-

terized by the SAIFI and CAIDI indicators. Reported
reliability indicators are calculated for outages
only. The values obtained for planned outages are
indicative.

Accountable outages

When calculating reliability indicators, almost all

violations  are  taken  into  account,  including  those
that the distribution company can’t directly influence,
for  example,  cable  damage  during  excavation  work
by  a  third  party.  Only  exceptional  events,  such  as
terrorist  attacks,  are  considered  as  force  majeure
events,  when  outages  are  not  taken  into  account  in
reliability indicators.

Determination
of reliability indicators planned values

Planned reliability indicators are not explicitly

established. The Netherlands uses a ranking system
for network companies based on a general indicator
of reliability and quality of services provided. The
size of the permissible established tariff depends on
the rating of the network company.

Based on the SAIFI and CAIDI indicators, da-

mage from unreliable power supply is determined.
It is taken into account when calculating the general
indicator.

The generalized indicator is calculated for a 3-year

regulation  period.  The  calculation  uses  the  SAIFI
and  CAIDI  indicators  of  network  companies  for  the
previous  regulatory  period,  as  well  as  the  average
SAIFI and CAIDI values for all network companies for
the same period.

According to Dutch law, network companies must

pay compensation to all customers for interruptions
that last more than 4 hours.

Clustering networks
with similar characteristics

All distribution networks in the Netherlands have

similar characteristics and operate under similar
conditions, so no additional clustering is applied. Av-
erage values of reliability indicators are determined
for all power distribution networks in the country.

USA. NEW YORK

In the United States, power distribution companies
are regulated at the state level.

Power supply reliability indicators

SAIFI and CAIDI are the main reliability indicators.

Network companies submit annual reports containing
accident rate analysis in their operating areas,
reliability improvement projects and analysis of the
worst-performing electricity feeders state.

Accounted outages

The outages frequency and duration are

standardized for normal operating conditions. In this
case, outages under abnormal external influences
are not taken into account. Moreover, the indicators
are also calculated taking into account all outages
used as indicative ones.

Abnormal external events are considered to

be those where power supply to at least 10% of
consumers in the operating area is disrupted and/or
the outage duration exceeds 24 hours.

Determination
of reliability indicators planned values

Two mechanisms are used to regulate the

reliability of power distribution networks: baseline
targets setting and tariff regulation [9].

The regulating authority collects detailed informa-

tion on technological disturbances in all networks ev-
ery month and it determines annual reliability indica-
tors  for  each  operating  area.  On  the  basis  of  actual
data on the electric power system reliability, baseline
reliability  targets  are  established  for  each  operating
area. These indicators correspond to the acceptable
minimum  level  of  reliability  and  they  are  used  to  as-
sess the actual level of electric power system reliabil-
ity; however, they are not used to determine penalties
or bonuses for network companies.

Tariff regulation is applied in relation to reliabil-

ity targets established for the network company as
a whole.

Clustering networks
with similar characteristics

Reliability indicators are determined for operating

areas. Operating areas correspond to the territorial
division and they include network sections with simi-
lar parameters.

USA. CALIFORNIA

Power supply reliability indicators

Network companies submit an annual reliability

report, that includes:

– SAIDI, SAIFI and MAIFI both at the level of the

entire network company and at the most detailed
level possible;

– information on the worst-performing electricity

feeders;

– external events and activities that have had an

impact on reliability;

– information on the current state of the equipment,

maintenance and repair activities.

Accounted outages

Reliability indicators are determined without

taking into account outages caused by abnormal
external events. According to IEEE Std 1366-2012 [1]
the "2.5 beta" method is used to determine abnormal
events.

Determination
of reliability indicators planned values

The maximum duration of power supply interruption

for an individual consumer is 24 hours.

Prior to 2006, the Reliability Incentive Mechanism

(RIM) was in force. It was aimed at tariff incentives to
achieve annual reliability targets. In the Brattle Group
report  [9]  there  is  note  that  the  key  disadvantage
of  this  approach  is  the  short-term  measures
incentivization.  The  incentivization  effect  could
come  out  in  the  next  year.  Long-term  investments
are  supported  to  a  much  lesser  extent  under  this
approach.  In  2006,  the  Reliability  Investment
Incentive  Mechanism  (RIIM)  was  adopted.  It  was
aimed  at  long-term  effectiveness.    Defined  level
of  investment  in  the  distribution  network  reliability
growth  was  established,  especially  in  terms  of
network  modernization,  preventive  maintenance
and equipment replacement. If a network company
fails  to  ensure  the  required  level  of  investment
in  reliability  growth,  the  accepted  tariff  level  is
reduced.

The regulating authority continues to collect de-

tailed  annual  reports  on  the  electric  power  system
reliability  despite  the  lack  of  specific  reliability  tar-
gets. The standard in force until 2006 set reliability
targets  for  network  companies.  The  SAIDI  targets
ranged  from  52  to  157  minutes  per  year,  SAIFI  –
from 0.9 to 1.24 failures per year.

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EP Shanghai 2023

Special issue, November 2023

RESULTS FROM THE ANALYSIS OF

DOMESTIC AND FOREIGN EXPERIENCE

IN RELIABILITY RATIONING

Established on legislative level, the minimum duration
of power outages level varies across countries:

– over the time of automatic power restoration

(Russia);

– 3 minutes (Great Britain, Italy);

– 5 minutes (USA, California).

Formal criteria for excluding power outages under

abnormal  external  conditions  are  defined  in  Great
Britain,  Italy,  the  USA  (New  York,  California).  In  the
Netherlands power outages under abnormal external
conditions  are  taking  into  consideration.  In  Russia,
a  grid  operator  is  always  responsible  for  power
outages  while  formal  criteria  for  determining  such
power outages are not formalized by regulations.

Scheduled power outages in the calculation of main

reliability indicators in Russia are accounted separately
by indicative ﬁ gures



SAIDI,rep



SAIFI,rep

. In the UK, plan-

ned outages are taken into account in the calculation
of  basic  reliability  indicators  with  a  weighting  factor
of  0.5.  In  Italy,  the  Netherlands,  the  USA  (New  York,
California)  planned  power  outages  are  not  taken  into
account in the calculation of main reliability indicators.
The main reliability indicators in the reviewed countries
are SAIFI and SAIDI or their analogs.

Planned reliability indicators for power distribution

networks  are  set  separately  for  each  grid  operator.  At
the same time, as a rule, the methodology for calculating
these  standards  is  established  at  the  legislative  level.
In  Russia,  the  target  values  are  reference  values
adjusted  to  the  current  year  taking  into  account  the

rate of improvement. Reference values for each group
are determined as average values within the group for
the  previous  three  years.  In  the  UK,  target  values  are
determined in a diﬀ erent way for various groups based on
retrospective data. Then they are combined into a single
indicator for the grid operator. In Italy, target values are
set as a certain percentile of the values for the previous
long-term regulatory period. In the Netherlands and the
United  States  (California),  targets  are  not  deﬁ ned  and
grid operators are ranked by actual values. In the USA
(New York), the planned reliability indicators correspond
to  the  minimum  acceptable  level  of  power  network
reliability while tariﬀ  regulation is based on the planned
reliability indicators for grid operators. For the countries
considered, the plan indicators are set for each type of
power network separately based on retrospective data
for the previous 3-5 years.

The reliability of different power distribution

networks  can  vary  quite  significant.  Many  countries
divide  power  networks  into  types  depending  on
operated  territory,  climatic  conditions,  load  density
and other factors.

Target values set in Russia are in line with those

in other countries. The scatter of SAIDI and SAIFI
target values for different groups of power networks
depending on operated territory, climatic conditions,
load density and other factors for the aforementioned
countries is shown in Figure 1. For Moscow and the
Moscow Region, these indicators are characterized
by very high reliability of the distribution networks.

In general, the regulatory framework for reliability

rationing in Russia is in line with global trends and
regulatory approaches.

Fig. 1 – Scatter of reliability indicators SAIDI, SAIFI planned values. Source: [5–11]

Planned values SAIDI, min/year

Planned values SAIFI, 1/year

200.0

180.0

160.0

140.0

120.0

100.0

80.0

60.0

40.0

20.0

0.0

2.5

1.5

0.5

Moscow

Russia (Rosseti Group)

Great Britain

Italy

Netherlands

. New

ork

. New

ork

. California

Australia

480; 964

4; 7.4

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REFERENCES
1. IEEE Std 1366-2012 (Revision of IEEE Std 1366-

2003). IEEE Guide for Electric Power Distribution
Reliability Indices. URL: https://standards.ieee. org/
ieee/1366/4602/.

2. Order of the Ministry of Energy of the Russian Federation

No. 1256 dated November 29, 2016 "On Approval of the
Methodological Guidelines for Calculating the Reliability
Level and Quality of Supplied Goods and Services for the
Organization for Management of the Uniﬁ ed National (All-
Russian) Power Grid and Territorial Grid Organizations".
URL: https:// base.garant.ru/71578114/.

3. Resolution of the Government of the Russian Federation

No.  1178  dated  December  29,  2011  (as  amended  on
February  17,  2022,  rev.  March  29,  2022)  "On  pricing  in
the ﬁ eld of regulated prices (tariﬀ s) in the electric power
industry"  (with  "Fundamentals  of  pricing  in  the  ﬁ eld  of
regulated  prices  (tariﬀ s)  in  the  electric  power  industry",
"Rules of state regulation (revision, application) of prices
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4. Order of the Ministry of Energy of the Russian Federation

No. 976 dated October 28, 2017 "On Approval of Basic
Values  of  Reliability  Indicators,  Values  of  Coeﬃ cients
of Permissible Deviations of Actual Values of Reliability
Indicators  from  Target  Values  and  Maximum  Dynamics
of  Improvement  of  Planned  Reliability  Indicators  for
Groups of Territorial Grid Organizations with Comparable
Economic  and  Technical  Characteristics  and  (or)
Operating  Conditions  with  Application  of  the  Method  of
Comparing  Analogues".  URL:  https://www.garant.ru/
products/ipo/prime/doc/ 71709300/.

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price control. Reliability and Safety. URL: https://
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Business, Energy & Industrial Strategy, UK Government,
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value for money services for consumers. URL: https://
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velopment of Moscow No. 466-TP dated November 28,
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In accordance with the current Russian legislation,

all power engineering entities should strive to reduce the
number of electrical equipment outages and improve
the reliability of power supply to consumers.

Improving reliability requires an increase in the

volume  of  investments  in  electric  power  facilities
because  the  creation  of  margin  power  and  reserve
schemes is essential. After all, it leads to an increase in
tariﬀ s. In this regard, it is advisable to achieve an optimal
reliability level with relation to both power consumers
and  electric  power  industry  entities.  The  optimal
reliability level from the viewpoint of power consumers
is determined by the balance between the number and
duration of electric power supply interruptions that do
not create discomfort for consumers and do not aﬀ ect
the level of tariﬀ s that consumers are willing to pay. The
optimal  reliability  level  for  power  engineering  entities
is determined by the balance between investments in
improving the level of reliability and compensation for
unreliable power supply.

Currently, there is a signiﬁ cant drawback in the

Russian  regulatory  framework  concerning  the  issues
of establishing target values of reliability indicators. The
current  methodology  [2]  provides  an  annual  decrease
in  reliability  indicators  (improvement  of  reliability  level)
by at least 1.5% while the unreduced reliability level is
not determined. In fact, this level should be maintained
without requirements for improvement.

It is worth mentioning that the means of objective

control  in  20  kV  and  below  distribution  networks  are
rather  poorly  developed.  As  a  result,  observability
absence  of  these  networks  takes  place.  The  need  to
provide regular and, as a rule, unjustiﬁ ed accident rate
reduction leads to systematic corruption of accident rate
data in order to meet the established reliability indicators.

As a result, the true picture of the current accident

rate situation and especially the causes of accidents is
very often corrupted. Timely measures to correct the
situation and ensure the required reliability level for
consumers seems not possible.

Taking into account the aforementioned data and

the analysis performed, it is necessary to establish both
reliability dynamic indicators and targets to be provided
by grid companies. The calculation of these indicators
should include objective parameters of the grid company
functioning.

CONCLUSIONS

The paper analyzes domestic and foreign experience in
rationing the reliability of distribution networks in Russia,
Great Britain, Italy, the Netherlands and the United States
(California  and  New  York).  According  to  the  results  of
the  analysis,  the  regulatory  framework  for  reliability
rationing  in  Russia  correspondes  to  global  trends  and
approaches  to  reliability  regulation  in  other  countries.
Moscow and the Moscow Region are characterized by
very  high  reliability  relative  to  the  target  indicators  in
other countries. The issue requiring further elaboration
is  the  deﬁ nition  of  reliability  indicators  target  values
in  the  conditions  of  current  operation  and  selection  of
criteria for their assessment.

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The paper analyzes domestic and foreign experience and compares the different countries approaches to rationing the power distribution networks reliability. The main indicators of power supply reliability in different countries with respect to outages, approaches for planned values determination and clustering of networks with similar characteristics are considered. Understanding the basic principles of power distribution network reliability regulation applied in foreign countries allows specialists to identify best practices and adapt them to domestic conditions.

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