Reliability assessment

Reliability assessment module

General

This add-on module is designed to aid distribution engineers in assessing the reliability of electric distribution networks. The program computes a set of predictive reliability indices for the overall system and their corresponding protection zones such as MAIFI, SAIFI, SAIDI, CAIDI, ASAI, ENS (Energy Not Supplied), AENS and LEI. It also computes customer point indices, such as the frequency of interruption, the duration, etc., for each customer. The module can calibrate the predictive model based on historical data. This functionality helps to adjust the failure rates and repair time for the overhead lines and cables in order to match the simulated model with historical indices.

With it you can also display all historical failure data on the diagram and colour-code it based on the number of outages, the causes, the type of failures, etc.

Reliability system data

In addition to the equipment data already modelled in Eaton's CYME software (ratings, impedances), the outage data for the different components are to be specified as follows:

• Failure rate (sustained and momentary)
• Repair time
• Switching/isolation time
  
• Stuck probability (on protective and switching devices)

The outage data can be computed and calibrated (adjusted) using historical data and can be modified graphically in various ways to reflect, for example, the impact of a tree-trimming campaign by defining environmental factors that affect failure rates and repair times at specific locations.

Calculation of the reliability indices

Using either historical data or user-defined failure data, the program can compute the different system and load point indices, taking into consideration the re-closing scheme (fuse saving or fuse clearing) and the re-closer settings (single-phase trip, three-phase trip, individual phase lock-out, all phases lock-out, etc.).

Restoration may be enabled by using the pre-contingency load flow. The automation of some switching devices will impact the restoration time.

Indices are automatically calculated at the feeder level, zone level (start of a protected zone) and customer level.

The network one-line diagram can be colour-coded, based on any of the computed indices as a reference.

This allows the visual identification of areas where the number of interruptions or the outage time exceeds the predefined standard limits.

It also features a mode to compare the results of two studies and present the differences graphically. This allows the user to evaluate the improvement in reliability due to the installation or relocation of equipment, effect of tree trimming, etc. as compared to the base case.

What-if scenarios