Concept for Distribution System Planning

Rationale - Since distribution utilities (DUs) are regulated with their operational power quality (PQ) and system reliability, which accounts for System Average Interruption Frequency Index (SAIFI) and System Average Interruption Duration Index (SAIDI), it may be considered to utilize the historical data for DU planning in the context of probabilistic evaluation.

Concept Methodology-

1. Gather PQ and DU system reliability data for a certain time range, maybe five years.
2. Establish level of PQ, SAIFI and SAIDI to be utilized for planning purposes by applying 95% probability acceptance.
2. Identify planning alternatives to solve problems of PQ and system reliability.
3. Compute and simulate levels of PQ, SAIFI and SAIDI per planning alternative.
3.1. This may utilize DU system reliability software/spreadsheet and PQ program simulation.
4. Compute relative system unreliability cost and cost incurred for poor PQ for each planning alternative.
4.1. System Unreliability Cost = SAIDI x Cost of electricity (P/kWH)
4.2. Poor PQ Cost = Energy Losses (due to Poor PQ) x Cost of electricity (P/kWH)
5. Compute total cost of each alternative.
5.1. Total Cost = Invesment Cost + Operational Cost + System Unreliability Cost + Poor PQ Cost
6. Two Methods for Planning Altenratives Comparison
6.1. Compare Total Costs of Planning Alternatives.
6.2. Benefit/Cost (B/C) Method, where [(Base Reliability + Base PQ) - (Alternative Reliability + Alternative PQ)]/ Total Cost of Alternative
7. Choosing appropriate planning alternative.
7.1. Choose planning alternative with Lowest Total Cost.
7.2. Choose planning alternative with Highest B/C.