A 56-year-old construction worker was burned yesterday when a 13,000-volt high tension electrical line at 1722 I St. NW exploded during an excavation period.

D.C. police said the man, identified as Charles E. Wright of 2130 Newport Pl. NW. was injured shortly before noon while working with a jackhammer in a pit near the exposed wires. He was transported to Georgetown University Hospital where he was admitted with burns to his face and eyes.

According to coworkers, Wright, an employe of the B. Frank Joy Co., Inc. of Bladenburg, was preparing to resume work with the jackhammer when the high tension line exploded, shooting out flames and sending a column of smoke about 50 feet into the air.

But a Potomac Electric Power Co. spokeswoman said the firm believes "that the employe's jackhammer made contact with the line," triggering the explosion.

'The spokeswoman said that the Joy Co. is building a manhole at the site for Pepco, which she described as "very routine" work.

Because the electrical line feeds into the power company's I Street substation, she said most businesses in that area would have experienced " a slight voltage variation," resulting, for instance, in a brief dimming of lights.