Bosed on the actual operation of the transformer in a power plant,this paper analyzes and evaluates the economic performance,total operating costs(TOC)and investment payback period of upgraded S7 and SJ transformers by using total operating costs of transformer and provide reliable basis for the transformer economic operation and create more economic benefits for the enterprise.

Discusses the relative electric power consumption for the single and double pipe system using frequency control of the pumps, provides their values calculated for 18 cities in China and a formula to estimate the static payback period for actual systems and an example.

The problem of fixing the tolling year of the toll road is a hot topic recently after toll-by-weight,the expressions of tolling year at present tolling system and its disadvantage when fixing the tolling year after toll-by-load are introduced.

by HPLC, and to study the content of triptolide in different harvesting years and different parts of Tripterygium wilfordii.

Some special problems in payback period of investment;

Calculates the payback period of investment of three kinds of fuel for one-pipe series loop heat-ing system renovated by using thermostatic radiator valve,summarizes that the renovated system of using thermostatic radiator valve not only saves energy,but also may rapidly recover initial investment when oil or natural gas is used as fuel.