Electromagnetic loops are inevitable in the development of power systems. However

the system operates with great risks when there are weak electromagnetic loops in a power grid. Based on an examination of problems and countermeasures for operation and control of weak electromagnetic loops

three main characteristics of weak electromagnetic loops are summarized and four main problems are brought up. Then the four problems are studied respectively

and corresponding countermeasures are proposed. Several practical examples of weak electromagnetic loops are given. Simulation results show that the proposed countermeasures are effective and helpful to research on operation and control of weak electromagnetic loops.