Washington Real Estate Investment Trust announced yesterday an increased dividend rate despite flat earnings in the first nine months of 1978.

For the third quater, WRIT profits dipped to $569.487 from $580.698 in the same period a year earlier, with per share earnings of 38 cents in both periods.

Nine-month operating profits were up slightly to $1.79 million ($1.18) from $1.75 million ($1.17). Not included in the nine-month period during 1977 is a gain of $1.6 million from a property exchange which resulted in overall net income of $3.3 million ($2.24 a share).

WRIT boosted its quarterly payout rate meanwhile to 47 cents a share from 45 cents starting with a Dec. 29 distribution to stockholders of record Dec. 5. It was the ninth consecutive year of dividened increases.

President B. Franklin Kata also said the trust is actively seeking new, prime real estate investments WRIT recently mortgaged its 1901 PennsylvaniaAVE. NW. building for $4.5 million and has available investment funds with no short-terms bank debts.

AT WRIT's Shirley-Glebe distribution center, where the Veterams Administration is vacating 80,000 square feet. Kahn said the space has been subdivided and 75,000 square feet leased at a rental increase of some $25,000 a year more than VA was paying. Rental increases there will be pegged to consumer price index changes and WRIT is spending about $60,000 for subdivision and renovation, a one-time expenditure.Total assets of WRIT on Sept. 30 were $44.6 million compared with $41.9 million a year ago.