Residence permit , while traveling in China

Hi
I am in PRC with Z visa , my work permit is issued from shanghai , but i travel for my work and will be staying in another city for one month. Do I have to go to police station and register myself , will it cancel my residency that I have in Shanghai , how does it work ?
when i go back to shanghai do i have to go to the police station and register again?
Regards
Shahz