Advanced technology and excellent performance of new circuit breakers supply low-voltage parts of city network support.

Based on that the author was successfully established an active power optimizing dispatching mathematics model for city network and the concept of optimization dispatching was put forward.

Exploration of experience to realize city grid refom;

This paper gives the method of type selecting of 110 kV new transformer used in urban power network, the problems that should be noticed, working out and revising condition of relative standards both in domestic and international, as well as IEC standard and the new stipulation of short circuit ability for transformer in national standard.

Some technical problems of distribution line project design for retrofit of urban power grid are introduced.