To satisfy the requirements of accurate operational risk assessment of integrated transmission and distribution networks (I-T&D)

an integrated operational risk assessment (I-ORA) algorithm is proposed. Specific cases demonstrate that an I-ORA is necessary because it provides accurate handling of the coupling between transmission and distribution networks

accurate analysis of power supply mode (PSM) changes of important users and helps to improve security and stability of power grid operations. Two key technical requirements in the I-ORA algorithm are realized

i.e.

integrated topology analysis and integrated power flow calculation. Under a certain contingency

integrated topology analysis is used to assess the risks of substation power cuts

network split and PSM changes of important users

while the integrated power flow calculation

based on the self-adaptive Levenburg-Marquard method and Newton method

can be implemented to assess risks of heavy load/overload and voltage deviation. In addition

the graphics processing unit is used to parallelly process some computation-intensive steps. Numerical experiments show that the proposed I-ORA algorithm can realize accurate assessment for the entire I-T&D. In addition

the efficiency and convergence are satisfying

indicating the proposed I-ORA algorithm can significantly benefit real practice in the coordination operation of I-T&D in the future.