As the scale and complexity of power system continue to increase, traditional line loss analysis methods have gradually revealed limitations such as high computational complexity and insufficient accuracy, hindering their effective application in practice. Therefore, this paper proposes a line loss analysis and optimization method tailored for novel power systems. A line loss outer approximation model is employed, which initially estimates line losses through an inertial approximation, with convergence of the line losses observed within at least two iterations. The application algorithm of this model in DC optimal power flow and security-constrained economic dispatching is analyzed to enhance power grid security and stability. Experiments conducted on novel power systems validate that the proposed line loss outer approximation model exhibits significant rapid convergence characteristics. The results indicate that, compared to traditional line loss methods, the proposed model achieves a computation speed 16 times faster when addressing large-scale test cases, with an absolute error of less than 0.08%, substantially reducing iteration time and computational costs while maintaining accuracy, thus providing an effective tool for the optimal scheduling of novel power systems.