A United Nations transition team arrived in Namibia (South West Africa) yesterday to set in motion a United Nations operation to oversee elections and the transition of Namibia to an independent state after almost 60 years as a territory under South African rule.

The 50-member U.N. team, headed by Finnish diplomat Martti Ahtisaari, was welcomed at the airport in Windhoek, the capital, by 10,000 demonstrators from the various political groups in the territory, including the militant Soutwest African Peoples' Organization (SWAPO), which has been waging a low-level guerrilla war against South African forces in the vast, semidesert territory for the past 12 years.

The large crowd is seen as an indication of lively interest in the U.N. operation and an awakening of political awareness in Namibia where, for the past 60 years, only the 100,000 whites in a population of 850,000 have had the right to vote. Although there has been violence in recent months between suporters of SWAPO and another major political party,the Democratic Turnhalle Alliance, there were no incidents at yesterday's demonstration, which was described as having a "festive" atmosphere.

The U.N. arrival is a major diplomatic victory for the five Western powers, the United States, France, Britain, Canada and West Germany, that worked out the independence plan accepted by both South Africa and SWAPO and then adopted by the United Nation on July 27. It is also a hopeful sign that negotiated solutions to the conflicts in Southern Africa can succeed in halting the escalating fighting switch its potential for superpower involvement, in this troubled area of the world.

Ahtisaari's immediate task is to become acquainted with conditions in Namibia, where voter registration is already under way. The U.N. team will remain for about three weeks and then report back to U.N. headquarters on how to implement the Western plan.

Under the Western proposals. South Africa's estimated 20,000 troops are to be reduced to a force of 1,500 men. A 5,000-man U.N. peackeeping force will move in to enforce a cease-fire between South African and SWAPO forces. A civilian task force will oversee the elections for a constituent assembly that will draw up a constitution. The country is scheduled to become independent Dec. 31.

While it is unlikely that South Africa or SWAPO, having come this far, will do anything to jeopardize the Western plan at this stage, there will be some problems.

In the first place, although the proposals stipulate that South Africa and the United Nations are to administer the proposals jointly, there is no agreed upon mechanism for resolving disputes between the two.

Second, there will also be difficulty in overcoming the distrust between South Africa and SWAPO.

Finally, there is weather. If the country is to become independent by the end of the year, elections must be held in September before the rainy season, which makes travel extremely difficult.