NEW DELHI, May 19 (Reuters) - A lack of transmission infrastructure is beginning to slow India's clean energy expansion, energy think tank Ember said, jeopardising the chances of the country achieving its aim of nearly doubling its non-fossil fuel powered electricity to 500 gigawatts by 2030.

Here are some details:

• The core of the problem is a growing mismatch between the pace of renewable energy being developed and the readiness of the transmission infrastructure, Ember said.

• One in four major transmission projects are already running a year or more behind schedule, the report said.

• As a result of the delay, 20 gigawatt (GW) of renewable energy capacity are likely to face connectivity delays of more than four months in fiscal year 2026-2027, Ember said.

• India rejected, or curtailed, about 300 gigawatt-hours (GWh) of green power from operational projects in January-March, the report said, citing a lack of infrastructure.

• The majority was rejected in India's northern region, accounting for 178 GWh, with the western region accounting for 122 GWh of power that was curtailed.

• Over the past five years, India has achieved only about 80% of its transmission build out targets on average, Ember said.