City employes walked picket lines yesterday in strikes that not only left Cleveland with almost no police but which also saw Louisville with sharply reduced fire protection and Philadelphia without the services of nearly 20,000 nonuniformed workers.

The Louisville and Philadelphia disputes erupted yesterday and stemmed from arguments over wages and other conventional contract issues unlike the Cleveland police strike.

Officials of public employe unions said the strike activity this year is at about the same, perhaps somewhat lower level thatit was last summer, although they acknowledge that public employe bargaining is getting more attention in light of property tax revolts in California and other states.They noted that midsummer is a peak period for municipal labor disputes and said they detect no national trend toward more strikes by government employes. Most recent strikes, they said, were triggered by local conditions and issues.

Strikers in Louisville, a city of 400,000, were defying a court order. Nearly all of the city's 600 fire fighters walked off the jobs early yesterday, a day after the Kentucky Labor Relations Board found the city guilty of unfair labor practices in its negotiations with the fire fighters. A spokesman for the mayor said about seven of the 23 firehouses in the city were manned - with management personnel. "The city is protected," he said.

Stephan Phelps, executive assistant to Mayor William Stansbury, said earlier: "We have National Guard troops standing by if the firemen ignore the temporary restraining order."

The firefighters have not made their demands public. They now have an annual starting salary of $11,085 for a 56-hour week. The city's latest offer would give a fifth-year firefighter an increase of $1,200 a year.

Like the Louisville walkout, the Philadelphia strike involved a contract dispute. Some 19,600 blue-collar, clerical and professional city employes struck while their union negotiators pondered a tenative contract settlement announced late Thursday night.

The immediate impact of the strike was mixed.The Art Museum and courts were closed, but Philadelphia International Airport was operating normally. Ninety guards failed to report for the midnight shift at Holmesburg Prison, the House of Correction and police took over the jobs.

The basic issues were money and threatened layoffs of city workers. The unions want a 9 percent pay raise to match the hike recently awarded city police by an arbitrator.