Winnie Mandela, wife of imprisoned black nationalist leader Nelson Mandela, was arrested again today as she returned defiantly for the second time in a week to her home town of Johannesburg, an area she is not allowed to enter under a new restriction order.

Mandela has filed a court application challenging the validity of the new government order, and her lawyers were negotiating with the authorities that she should not be rearrested before the case is heard Jan. 7, when police stopped her car as it crossed the city boundary, pulled her from it and took her away.

She is spending tonight in a police cell in the nearby town of Krugersdorp, where she was detained eight days ago after her first return to her home in Johannesburg's black ghetto of Soweto.

Mandela is due to appear in court Tuesday. Her lawyers said if she were released on bail she was likely to return immediately to her home and be arrested yet again.

Each time she is arrested she is charged anew with breaking her restriction orders, which carry a penalty of three years' imprisonment. But Mandela, whose husband has been in prison for 23 years and who has herself been detained and imprisoned many times, seems undeterred.

There were dramatic scenes during her arrest today, as there were when police forcibly evicted her after issuing the new restriction order Dec. 21 and then arrested her when she returned the next day.

Mandela was returning from several days in Cape Town, where she had visited her husband over Christmas in Pollsmoor Prison, and police set up a roadblock on the highway from the Johannesburg airport to stop her as she crossed the city boundary.

There were angry exchanges as a policewoman reached into the automobile and tried to pull Mandela's 2-year-old grandchild, Zodwa, from her arms, and then a policeman tried to drag Mandela herself from the car. While television cameras filmed the roadside struggle, Mandela was finally bundled into a police car and driven away.

Mandela, who has become a symbol of resistance to many blacks, began her latest campaign when her house in the small country town of Brandfort, to which she was banished eight years ago, was destroyed in a gasoline bomb attack in mid-August.

She quit the small town 250 miles south of Johannesburg in defiance of the banishment order and moved into her family home in Soweto.

The authorities seemed reluctant to act against her under the circumstances, and particularly in the face of increasing local and international pressures for them to release her husband and begin negotiating with his outlawed opposition party, the African National Congress.

But after four months, during which Mandela also ignored gagging orders and addressed several press conferences as well as a black political rally in a Pretoria ghetto, the attitude of the authorities changed in the wake of several African National Congress guerrilla attacks that caused white civilian deaths.

On Dec. 21 police served Mandela with a new restriction order that seemed designed to finesse the awkward situation the authorities were facing. It removed many of the old restrictions on her, including the banishment to Brandfort, stating in effect that she could live anywhere in the country except in the Johannesburg area, where her home is.

Given that as a black person Mandela may not live in a designated white area, her rights of residence in black areas are severely limited, and the housing shortage for blacks is so acute that families are accommodated only after years on a waiting list, Mandela contends the new restriction order in effect means she must move back to Brandfort.

That she refuses to do, arguing that it would set her up for another assassination attempt. She notes that the attackers who bombed her house have not been caught.

Police today announced the release of 45 political activists detained without charges in Cape Town in October, when the government extended the state of emergency to that region.

But the released persons, members of the United Democratic Front, have been placed under restriction orders that will effectively prevent them from taking part in any political activities.

The restrictions confine them to the districts where they live and prevent them from preparing material for publication, taking part in United Democratic Front activities or criticizing the government "in any way."

The rules will remain in force until the emergency is lifted.