Customer Metrics: Stepping outside the System Box

The most commonly measured reliability indices by electric utilities are the System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI). These IEEE Distribution Reliability Indices (Standard 1366) are used to track utility performance, and they are often used to benchmark against utilities.

Benchmarking has its place, but how SAIDI and SAIFI is measured across utilities can differ while adhering to the IEEE 1366 standard. How is that possible? Some utilities are unable to measure or estimate the number of customers interrupted by outages at all levels of the distribution grid.

For example, Utility A has a circuit with 3,000 customers and a fault occurs on a lateral with 700 customers which takes 180 minutes to restore. Given the utility does not have the capability to measure or estimate the customer count on the lateral, this fault is not included in the SAIDI and SAIFI measurement. In the same scenario, Utility B with the capability to measure customer count along the feeder included the fault in its measurement.

When it comes to reliability indices with a focus on the customer, most utilities will use the Customer Average Interruption Duration Index (CAIDI), which is related to SAIDI and SAIFI. In essence, we have a customer index based on system calculations. Do these indices help us to understand our individual customers’ outage experience?

Given this digital era, our customer’s needs, wants and demands have significantly changed over the years. An outage today has a greater impact than years ago. Therefore, consideration must be given to using customer centric indices.

For example, the IEEE 1366 metric – Customers Experiencing Multiple Interruptions (CEMIn). This metric indicates the ratio of individual customers experiencing more than n sustained interruptions to the total number of customers served. The number behind this metric represents an actual customer and their individual outage experience compared to the index associated with SAIDI and SAIFI. To achieve this metric, utilities must be able to measure or estimate the number of customers along all levels of the distribution grid.

These customer metrics in no way replaces our systems indices which have served us well and from which several successful improvement strategies have been built, but it could be considered as an additional metric that: (1) sensitizes us to each customer’s outage experience and (2) helps us to refine our improvement strategies.

Learn more about the Writer

This article was submitted to CARILEC, by Nneka C. Archer.  Nneka holds a Bachelor of Science in Electrical and Computer Engineering, a Masters Business Administration and a Doctorate Business Administration. She has 21 years of experience working at Barbados Light & Power in different areas of Transmission and Distribution. She currently holds the position of Engineering Manager, T &D Assets.