In a career spanning more than 30 years, John Pettigrew has seen big changes in the electricity industry. He started out in 1991, working to introduce natural gas-fired power plants to the grid, gradually replacing polluting coal plants. .

Now, once again, he is managing a tectonic shift to an electrified economy that runs on renewable energy like wind and solar power. But these sources of power generation are far trickier to manage than their coal and gas predecessors.

“Effectively, what we’re doing is reconfiguring the whole network,” said Mr. Pettigrew, chief executive of National Grid, which owns and operates the high-voltage electricity grid in England and Wales.

Mr. Pettigrew was emerging from a tunnel nearly 20 miles long that National Grid has bored deep underground at a cost of about 1 billion pounds (about $1.3 billion). The shaft, which workers ride through on bicycles, will carry new cables to feed the power-hungry

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