Along with the development and perfection of Chinese power market and the new technology

the power grid planning

especially the transmission system planning

is facing new problems and challenges. For the above situation

this paper proposes a hybrid criterion planning model for medium-term and long-term multi-scenario transmission system planning based on the deterministic criterion and the probabilistic criterion under the electricity market. The model combines the constraints and parameters of both deterministic and probabilistic criterions

including flexible constraints

investment cost

power supply

demand bids

time cost

probability of contingencies

value of customer reliability(VCR)

loss of load expectation(LOLE)

and expected energy not served(EENS). Meanwhile

a number of scenarios are defined to simulate the load level of the power system. The transmission system planning problem is transformed into a mixed-integer linear programming problem to seek the optimal planning scheme by using the DC-power flow equations and the commercial solver CPLEX. Through the comparison between the proposed model and the conventional planning models

test results of actual cases of study in the power grid show the flexibility

the effectiveness and the economy of the model proposed. This work is supported by State Grid Corporation of China(No.XT71-14-038).