Download Risk-Based Resource Allocation for Distribution System Maintenance

distribution systems as defined in the IEEE Guide for Electric Power Distribution
Reliability Indices (IEEE 1366-2003):
1. System Average Interruption Frequency Index (SAIFI):
The system average interruption frequency index (SAIFI) indicates how often the
average customer experiences a sustained interruption over a predefined period of time
for a given area in the system:
SAIFI =
Total number of customers interrupted
Total number of customers served
(A.1)
For a fixed number of customers, the only way to improve SAIFI is to reduce the number
of sustained interruptions.
2. System Average Interruption Duration Index (SAIDI):
System average interruption duration index (SAIDI) indicates the total duration of
interruption for the average customer during a predefined period of time, commonly
measured in customer minutes or customer hours of interruption:
SAIDI =
Total duration of all customer interruptions
Total number of customers served
(A.2)
SAIDI can be improved by reducing the number of interruptions or the duration of the
interruptions.
3. Customer Average Interruption Duration Index (CAIDI):
The customer average interruption duration index (CAIDI) represents the average
time taken to restore service to the customers:
CAIDI =
Total duration of all customer interruptions
Total number of customers interrupted
(A.3)
CAIDI can be improved by reducing the length of interruptions by faster crew response
time and repair times.
4. Average Service Availability Index (ASAI):
The average service availability index (ASAI) represents the fraction of time that a
customer has received power during the defined reporting period. Higher ASAI values
reflect higher levels of reliability [31]:
ASAI =
Customer hours service availability
Customer hours service demand
80
(A.4)