Complex of technical solutions for protection and selective signaling of single-phase earth faults in 6-10 kV distribution cable networks

Abstract

Single-phase earth faults are the predominant type of damage in distribution 6-10 kV cable networks, and are often the root cause of power failures to consumers, accompanied by significant economic damage. Therefore, reliability for about 50% of consumers of industrial and urban power supply systems depends on the technical perfection of protection against earth faults. The currently used approach to the design of protection and signaling of earth faults, based on the application of the existing concept of selectivity of considered protection, does not always ensure the achievement of the main goal – increasing the reliability of power supply to consumers. To improve the reliability of power supply, new technical solutions are needed that provide not only selective detection of the damaged connection for all types of single-phase earth faults, but also the recognition of the most dangerous for the network and the protected connection faults types for automatic selection the most effective protection action (signal or shutdown). Within the framework of the existing approach, the design of protection against earth faults with the specified properties is possible only on the basis different methods of its implementation in networks with different neutral grounding modes, which is associated with the complication of protection circuit, its design and exploitation. A new approach has been proposed that provides universal technical solutions for protection and signaling of earth faults for 6–10 kV cable networks with various neutral grounding modes. To implement the proposed approach, universal adaptive current protection and universal admittance protection based on the control of the capacitance of zero sequence loop of the protected connection have been developed.

An Analysis of the Statistics of Technological Disruptions in a Medium Voltage Cable Distribution Network

“…Технологические отключения, возникающие при авариях в распределительных сетях напряже-нием 6-10 кВ, представляют собой распространенное явление. Так, согласно [16] отключения в сетях данного напряжения составляют до 70 % всех сбоев электроснабжения потребителей, которые возникают в результате ОЗЗ и межфазных КЗ. В качестве основных причин, способствующих возникновению подобных аварийных, выделяют:…”