Distribution Reliability Assessment

Distribution Reliability Assessment

Distribution Reliability Assessment

Distribution system reliability assessment deals with the availability and quality of power supply at each customer service entrance.
Distribution Reliability Assessment

Analysis of customer failure statistics show that, compared to other portions of electrical power systems, distribution system failures contribute as much as 90% towards the unavailability of supply to a load. These statistics show how important the reliability evaluation of distribution systems can be.

In order to evaluate the severity or significance of a system outage, using the three basic indices mentioned above, two expanded sets of indices listed below must also be calculated. The two expanded sets of indices include the number and average load of customers connected at each load point in the system and the customer interruption cost.

Distribution Reliability Assessment Features

  • System reliability
  • Customer oriented indices
  • Energy (cost) indices
  • Sensitivity analysis
  • Single & double contingency
Distribution Reliability Assessment Plots

Distribution Reliability Assessment Capabilities

  • Model reliability characteristics of each component
  • Implement user-defined parameters & settings
  • Calculate bus and load point reliability indices
  • Calculate system reliability indices
  • Calculate reliability energy (cost) indices
  • Rank element contributions to energy (cost) indices
  • Calculate effect of simultaneous faults
  • Select types of components for plotting
  • Availability & quality of power assessment
  • Long-term planning & redundancy
  • Single & double contingency studies
  • Multiple phase configurations
  • Unbalanced system reliability calculation
Distribution Reliability Assessment Analysis


  • Graphical display of reliability results
  • Load point/bus reliability indices
  • System reliability indices
  • EENS & ECOST sensitivity analysis
Distribution Reliability Assessment Reporting

Customer Oriented Indices

  • System Average Interruption
  • Frequency Index - SAIFI
  • System Average Interruption
  • Duration Index - SAIDI
  • Customer Average Interruption
  • Duration Index - CAIDI
  • System Customer Total Average Interruption Duration Index - CTAIDI
  • Average Load Interrupted per Connected Load Served - ALII
  • Average Customer Curtailment Index - ACCI
  • Average Service Availability Index - ASAI
  • Average Service Unavailability Index - ASUI
  • Sector interruption cost estimates: Customer Damage Function - CDF
  • Momentary Average Interruption Frequency Index - MAIFI
  • Momentary Average Interruption Duration Index - MAIDI

Energy (Cost) Indices

  • Expected Energy Not Supplied - EENS sensitivity analysis
  • Expected Interruption Cost - ECOST sensitivity analysis
  • Element contributions to the EENS & their rankings
  • Element contributions to the ECOST & their rankings
  • Order of most contributing components to EENS & ECOST
  • Interrupted Energy Assessment Rate - IEAR
  • Interruption cost library
  • Component parameter library

System Reliability Indices

  • Average failure rate - l
  • Average outage duration - r
  • Annual outage duration - U
Electical System Reliablity Assessment SoftwareDistribution RA - Sensitivity Analysis
The indices EENS, ECOST, and IEAR can be those specifically for each load point or for the overall system. All of these indices can be used to evaluate the reliability of an existing distribution system and to provide useful planning information regarding improvements to existing systems and the design of new distribution systems.

Moreover, in order to analyze the sensitivity of a reliability index EENS or ECOST with respect to failure rate of different elements, element contributions to that index and their rankings can be used. The rankings can be for a load point or the overall system.

All of the indices and rankings given above can be evaluated using the ETAP Reliability Analysis module. This module provides you with the best tool to efficiently model various power system elements and devices to include their effects on the distribution system reliability, such as fault isolation and load restoration through the operation of switching devices. 

This module is suitable for reliability analysis of large-scale systems of general configurations. By using this module, you can assess the distribution system reliability, and the merits of various reinforcement schemes that are available to the planner can be quantitatively evaluated to ensure that limited capital resources are used to achieve the greatest possible improvement in system reliability.



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