Power Quality Control
Ing. Jan Šefránek
Energetický regulační úřad [Energy Regulatory Office / Czech Republic]
Jan.Sefranek@eru.cz
Špindlerův Mlýn, 17. – 18. 4. 2013
Power supply quality
The quality of power supply and services has been defined by the Regulation of ERÚ No.
540/2005 Sb., on power supply quality and related services in power industry, as amended,
which stipulates:
•Required power supply quality and additional services related to regulatory activities in
power industry (standards),
•Amount of compensation for non-observance of prescribed standards,
•Terms for determination of financial compensation,
•Procedures for proving the compliance of power quality and services [with standards]
Claiming of compensation:
Compensation for non-observance of standards should be claimed by customer within 60
calendar days:
•for
non-observance of the guaranteed standard of distribution at that DSO to which
respective customer is connected,
•for non-observance of the guaranteed standard of supply at that supplier which supplies
power to customer in accordance with respective contract.
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Power supply quality
Standards define the level of quality which must be attained in each individual case.
Standards can be divided into two main groups:
a) Standards for power transmission or distribution
•The first part contains the information related to the continuity of power supply in grids, i.e.
the data influenced by fault events or planned events in operated distribution grids.
•The second part contains standards related to the commercial quality which characterises
the ability of power distributor or producer to respond to applicable requirements of end
customers; such quality is not directly related to the physical operation of systems.
b) Standards for power supply
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Evaluation of continuity level
The Regulation of ERÚ as mentioned above represents also the basis for monitoring and
evaluation of Power Transmission / Distribution System Continuity Level.
Power transmission indices:
Average power transmission interruption duration – in the evaluated year),
Energy Not Supplied (ENS).
Power distribution indices:
System Average Interruption Frequency Index (SAIFI = Average number of interruptions
that a customer would experience - in the evaluated period),
System Average Interruption Duration Index (SAIDI = Average outage duration for each
customer served - in the evaluated period),
Customer Average Interruption Duration Index (CAIDI = Sum of all customer interruption
durations divided by Total number of customer interruptions - in the evaluated period)
CAIDI = SAIDI / SAIFI
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Evaluation of power transmission continuity
Indices of continuity in 2012:
Number of power transmission interruptions in 2012 [-]
1
Total power transmission interruption duration in 2012 [min]
4
Average power transmission interruption duration in 2012 [min]
4
Energy Not Supplied in 2012 [MWh]
4,5
Development of indices:
Average power transmission interruption duration (min)
Energy Not Supplied (MWh)
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Evaluation of power distribution continuity
It is hardly possible to compare DSOs in a simple way; it is always important to take their
profiles in consideration.
Profiles of DSOs in the Czech Republic :
Company profiles
ČEZ Distribuce
E.ON Distribuce
PREdistribuce
Total
Czech Republic
Number of
customers
[-]
Length of
cable
lines [km]
Length of
overhead
lines [km]
LV
3 519 281
50 677
47 962
43 332
HV
14 393
9 777
40 131
293
VHV
296
13
9 707
231
LV
1 480 810
22 902
16 838
18 301
HV
8 339
3 533
18 630
109
VHV
41
6
2 391
6
LV
747 566
7 756
80
4 008
HV
1 942
3 746
117
288
VHV
5
58
144
0
LV
5 747 657
81 335
64 880
65 641
HV
24 674
17 056
58 878
690
VHV
342
77
12 242
237
Voltage
levels
Number of
transformers
[-]
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Evaluation of power distribution continuity
Profiles of distribution companies:
Total length of lines (km)
Proportion of cable lines (%)
Cable lines
Overhead lines
Cable lines
Overhead lines
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Evaluation of power distribution continuity
Indices of continuity in 2011:
Index*
SAIFI [interruptions/yr]
ČEZ Distribuce
E.ON Distribuce
PREdistribuce
Česká republika
2,88
2,00
0,65
2,36
SAIDI [min/yr]
296,70
314,40
46,79
268,82
CAIDI [min]
103,15
157,26
72,13
113,87
System indices which include all sorts of interruption according to Appendix No. 4 to the Regulation No. 540/2005 Sb.
Development of indices of continuity:
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Evaluation of power distribution continuity
Structure of power distribution continuity indices at LV (nn) level in 2011:
Scheduled interruptions
Non-scheduled interruptions :
Pink: Fault-related interruptions
under normal weather
conditions:
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Comparison of power quality level in EU
 Comparison of power supply quality is quite difficult and often misleading. It is always
necessary to take in consideration specific aspects in respective countries, such as the
character of grids, mode of grid operation (proportion of cable lines, length of cable
outlets, age of grids, etc.), geographic and natural conditions and also historical
experience with quality monitoring and purpose of power quality control in respective
countries.
 Power supply continuity can be evaluated using indices which may not be identical in
respective countries.
 The most often used indices, also in the Czech Republic, are SAIFI and SAIDI which are
related to the number of customers affected by long-term power distribution
interruptions.
 However, even the methods for calculation of indices are not unified and this aspect
should be taken in consideration when comparing actual values – it is important which
categories of interruption are involved in relevant indices (see e.g. the differences in
Austria, Germany, etc.).
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Comparison of power quality level in EU
•
Dominant impact on continuity indices has the proportion of cable lines, namely at the
HV level.
Proportion of cable lines at the LV (NN) and HV (VN) levels
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Comparison of power quality level in EU
• Index SAIFI – non-scheduled interruptions without extraordinary events
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Comparison of power quality level in EU
• Index SAIDI – non-scheduled interruptions without extraordinary events.
13
Comparison of power quality level in EU
• Index SAIFI – scheduled interruptions
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Comparison of power quality level in EU
• Index SAIDI – scheduled interruptions
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Motivational quality control
• The Regulation on power quality and related standards is aimed at the protection of the
most vulnerable customers, namely through the limits which define the level of quality
which is to be achieved in each individual case.
• On the other hand, the goal of Motivational quality control is to influence the power
quality in the whole system; in this particular case in a distribution system.

The aim is to reduce the number and time of power distribution interruptions. This
relates especially to the category of scheduled interruptions which are not restricted by
legislation, even if they represent the most frequent subject of customer complaints.

Another goal is the gradual unification of power supply quality throughout the Czech
Republic, as the Czech customers pay now comparable power distribution fees for
different power quality. The last but not least goal of the Regulation is the achievement
of better results in the process of comparing power quality levels with other EU
countries.

The combination of these two mechanisms should ensure the gradual improvement of
power supply quality for all customers in the Czech Republic.
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Motivational quality control

In 2012, ERÚ as the Regulator determined the quality indices and respective
parameters (the values of such indices) for 2013 for the area of power distribution.

This results from the Report of ERÚ on the methodology of regulation for the Third
regulation period which introduces the concept of Motivational quality control with its
main goal which is to set the required level of quality for provided services in relation to
their prices.

Any bonus or penalty shall be related to the amount of profit determined by ERÚ for
respective period (year) of regulation.

Required values of indices SAIFI and SAIDI for 2013 have been determined on the basis
of available data from previous periods, such values include further reduction by
approx. 5 % (depending on respective company and indices).

Such Indices are specifically whole-system continuity indices as defined by the
Regulation No. 540/2005 Sb., without taking in consideration those events which
happened without any influence of respective Distribution System Operator.
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Motivational quality control
Detailed definitions of respective indices:
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Motivational quality control
Diagram of motivational quality control:
Standard value
of
Standardní
hodnota
quality
index
ukazatele kvality
Bonus
STQ
ΔPVmax
gradient ofpřímky
line
CKCK– –směrnice
Achieved level
of
Dosažená
úroveň
quality
index
ukazatele kvality
Lower
Nižšíquality
kvalita
DUQmin DUQ
Vyšší
kvalita
Higher
quality
DHNP
Neutral zone
Neutrální
pásmo
HHNP
DUQmax
ΔPVt
ΔPVmin
Penalty
Penále
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Performance/Quality index rating for 2013
Setting of required values of indices SAIFI and SAIDI for 2013:
 The values of parameters for the regulation period [year] 2013 have been set on the
basis of detailed evaluation of available data of ERÚ according to the capabilities of
individual Distribution System Operators.
 This relates in particular to the whole-system continuity indices SAIFI and SAIDI as
defined by the Regulation No. 540/2005 Sb., without taking in consideration those events
which happened without any influence of respective Distribution System Operator.
 The events which will not be included in the required values of indices for 2013 are in
particular the following interruptions:
 faulty interruptions caused by any fault with the origin in the equipment or operation of any
transmission or distribution system operator under unfavourable weather conditions (16),
 faulty interruptions caused by any interference or action of a third person (12),
 forced interruptions (15),
 extraordinary interruptions (14),
 interruptions caused by events from outside (out of TS or DS) or events in power generation
units (13).
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Performance/Quality index rating for 2013
Values required for 2013 and tentatively also for the next period(s):
ČEZ Distribuce - SAIFI:
required value 2,36
tolerance zone
±5%
max. bonus/penalty ± 15 %
(Value of interannual decrease)
6%
21
Performance/Quality index rating for 2013
ČEZ Distribuce - SAIDI: required value 262,70
tolerance zone
±5%
max. bonus/penalty
± 15 %
(Value of interannual decrease)
5%
22
Performance/Quality index rating for 2013
E.ON Distribuce - SAIFI: required value 1,57
tolerance zone
±5%
max. bonus/penalty ± 15 %
(Value of interannual decrease)
4%
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Performance/Quality index rating for 2013
E.ON Distribuce - SAIDI: required value 275,36
tolerance zone
±5%
max. bonus/penalty
± 15 %
(Value of interannual decrease)
6%
24
Performance/Quality index rating for 2013
PREdistribuce - SAIFI: required value 0,44
tolerance zone
±5%
max. bonus/penalty ± 15 %
(Value of interannual decrease)
5%
25
Performance/Quality index rating for 2013
PREdistribuce - SAIDI: required value 37,37
tolerance zone
±5%
max. bonus/penalty ± 15 %
(Value of interannual decrease)
5%
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Performance/Quality index rating for the period until 2020
 A principal and necessary step for the functioning of Motivational quality control in
practice is the definition of required goals of the Regulator (ERÚ), i.e. the
determination of attainable level of power supply quality in a short-term horizon.
 It is essential for this step to elaborate a study which would determine the relation
between potential measures for [desirable] decrease of values of respective indices
(SAIFI, SAIDI) and expenses of individual Distribution System Operators.
 Based on conclusions of such study, it would be possible to revise the set of required
tentative parameters (values) of indices SAIFI and SAIDI in the period until 2020.
 To get a longer time series of such parameters, it would be possible to use the averaging
of values of such indices within e.g. three-year cycles to eliminate their possible
oscillation in individual years.
 A working group of representatives of ERÚ and DSOs was created in 2012 to deal with
these issues.
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Thank you for your attention...
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