Universal Centralized Protection against Single-Phase Earth Faults in Cable Networks with Voltage of 6–10 kV

Selective protection against single-phase earth faults in 6- to 10-kV distribution cable networks can be implemented using both individual (per connection) and centralized devices covering all connections of the protected facility. The advantages of centralized devices are reduction of specific (per one connection) costs for implementing protection and simplification of its operation and design. Known technical solutions for centralized devices for protection against this type of damage do not always ensure their universality (the possibility of application under various neutral grounding modes of 6- to 10-kV cable networks) and high technical excellence (selectivity and stability of operation). In this regard, the development of universal centralized protection against single-phase earth faults that would ensure high technical excellence under all considered types of earth faults in 6- to 10-kV cable networks with various neutral grounding modes is relevant. To study the selectivity and stability of the developed principles of implementation and algorithms of centralized protection against single-phase ground faults, a complex “cable network–protection device” simulation model implemented in SimPowerSystems and Simulink was used. The configuration and parameters of the cable network model were selected taking into account the main features of 6-10 kV distribution cable networks of industrial and urban power-supply systems. Results: A universal centralized protection against all types of single-phase ground faults in 6- to 10-kV cable networks with different neutral grounding modes was developed. The results of functional tests on the simulation model are presented, confirming the efficiency of the developed algorithms for the functioning of the centralized protection for all considered types of ground faults, both in uncompensated and compensated 6- to 10-kV cable networks. The proposed technical solution implements a multifunctional multiparameter centralized protection against single-phase earth faults, possessing such properties as universality, selectivity and high stability of operation for all types of earth faults, recognition of types of single-phase earth faults, and continuity of operation for the stable and most dangerous arc intermittent earth faults.