Norfolk & Western Railway yesterday reported a 10 per cent increase in third-quarter profits, despite a wildcat strike by coal mine workers in the period. Virginia Electric & Power Co. also reported higher profits, but earnings fell at A. H. Robins Co., the pharmaceutical firm based in Richmond.

Third-quarter profits of Roanoke-based N&W, one of the country's largest coal haulers, increased to $21.8 million (70 cents a share) from $19.9 million (64 cents) in the same period last year. Revenues rose 5 per cent to $309 million.

President John P. Fishwick warned, however, that N&W's results for the current quarter would suffer if the Uniteds Mine Workers go on strike when a current contract expires Dec. 6.

Because of depressed earnings earlier in the year, when N&W operations were hit first by cold weather and then flooding, nine-month profits were down. N&W earned $77.4 million ($2.48) in the first three quarters, off some 9 per cent from $84.9 million ($2.72) in the 1976 period. Revenues rose 4 per cent to $935 million.

N&W owns Dereco, Inc., which in turn owns the Delaware & Hudson Railway. For the recent quarter, Dereco lost $2.5 million compared with a loss of $1.2 million last year; nine-month losses for Dereco totaled $5.9 million vs. a loss of $3.6 million in the 1976 period.

Whether or not there is a coal strike, N&W expects lower profits in the fourth quarter compared with the record $46.6 million ($1.49 a share) in the 1976 period. Fishwick said yesterday.

On other matters, Fishwick revealed:

N&W does not expect freight trafic to rise substantially in 1978 although he does expect an "appreciable" increase in coal shipments.

The rail firm is spending about $1 million to "winterize" a coal-loading facility at Norfolk. New equipment there will break apart lumps of coal to prevent a repetition of the situation last winter, when coal froze in hoppers and made it difficult for unloading at ocean piers.

Virginia Electric & Power Co.'s third-quarter profits rose to $61 million (67 cents a share) from $53 million (62 cents) in the 1976 period, where there were fewer common shares outstanding. Revenues rose to $387 million from $302 million.

For a 12-month period ended Sept. 30. Vepco profits totaled $186 million ($1.93 a share) compared with $155 million ($1.69), and revenues increased to $1.3 billion from $1.1 billion.

Vepco chairman John McGurn said that the higher profits in the recent quarter reflected increased use of air conditioning in a warmer-than-normal summer. During the first nine months of 1977, Vepco customers consumed 9.7 per cent more electricity than in the like 1976 period.

A. H. Robins Co. earnings declined despite higher sales in the recent quarter. Net income fell to $6.3 million (24 cents a share) from $7.2 million (28 cents) in the 1976 period as sales rose to $74 million from $68 million.

Nine-month earnings also declined to $20 million (76 cents) vs. $24 million (93 cents) as sales increased to $223 million from $209 million.

President William L. Zimmer III said the lower profits reflected higher operating expenses combined with only a marginal gain in sales. Robins said no provision has been made for any liability the firm may incur because of lawsuits that result from use of the Dalkon Shield, an interuterine birth control device no longer manufactured.

"The ultimate outcome of the lawsuits cannot presently be determined," Robins said.

New Virginia Bancorp., which owns Northern Virginia Bank of Springfield, said its net for the nine months was $989,688 (88 cents a share) compared with $884,654 (79 cents) last year. Total assets increased by 13.5 per cent to $136 million, total deposits grew by 13.4 per cent to $125 million and total loans rose by 23 per cent to $75 million.