Seeking its third base rate increase in four years, Potomac Electric Power Co. won approval from Maryland regulators Friday for a $28 million increase in distribution rates and a $24 million surcharge to accelerate the hardening of feeder lines.

Pepco had asked the Maryland Public Service Commission for almost $61 million in additional distribution rates and an increase in its return on equity (ROE) to 10.25%. The commission accepted a staff recommendation for an ROE of 9.36%, a slight boost from the current 9.31%. The changes will add $2.41 monthly to the average residential bill, effective July 12, 2013.

Pepco also requested a $192 million Grid Resiliency Charge, including $17 million for accelerated vegetation management; $151 million to move portions of six feeders underground and $24 million to accelerate the hardening of 24 feeders that are prone to outages during major storms.

The commission approved only the work on the 24 feeders, saying it needed more information on the undergrounding proposal. The commission said the company’s plan for accelerating vegetation management in 2014 “has no impact on the amount of tree trimming required for subsequent years and provides no cost savings in the future.”