Line Differential Protection Scheme Modelling for Underground 420 kV Cable Systems

Based on the analysis of a specific relay model and an HVAC （high voltage alternating current） cable system, a detailed approach to EMTDC/PSCAD modelling of protective relays is presented. Such approach allows to create complex and accurate relay models derived from the original algorithms. Relay models can be applied with various systems, allowing to obtain the most optimal configuration of the protective relaying. The present paper describes modelling methodology on the basis of Siemens SIPROTEC 4 7SD522/610. Relay model was verified experimentally with its real equivalent by both EMTP-simulated and real world generated current signals connected to the relay.

DCD-4型差动保护误动作分析

广东省长龙水电站主变的DCD-4型差动保护装置,原整定计算时,忽视了变压器高、低压两侧二次电流不相等带来的问题,故多次因线路受雷击而误动。针对此问题,引用BCH-2型差动继电器平衡绕组整定计算的方法来整定DCD-4差动继电器的平衡绕组匝数,将变压器高、低压两侧二次电流不相等产生的不平衡电流,通过平衡绕组来达到平衡,从而消除了造成继电器误动的原因。