With the development of renewable-energy-dominated power system, current differential protection, a key technology to ensure the safe operation of power systems, has attracted widespread attention regarding its reliability. However, the influence of noise interference in the process of information transmission is often ignored in the existing studies when discussing current differential protection, which may lead to the failure of protection action. Deeply analyzes the influence of complex noise disturbance composed of Gaussian white noise and impulse noise on the operation characteristics of current differential protection, based on the ρ-plane theory, and proposes a new sector criterion. Compared with the traditional circular criterion, the proposed sector criterion can provide a larger braking area, and has superior anti-misoperation and anti-braking performance under different signal-to-noise ratio, which can be proved by theoretical analysis and simulation experiments. The sector criterion reduces the mal-operation rate by about 50% compared to traditional criterion, and can ensure that both the mal-operation rate and the refusal operation rate are far less than 10-5, even under complex noise disturbances with a low signal-to-noise ratio (30dB). It provides a high-reliability solution for current differential protection in the distribution network, which has important theoretical and practical significance for ensuring the safe and stable operation of the new power system.