 Protective relays work in concert with sensing and control devices to accomplish their function. Under normal power system operation, a protective relay remains idle and serves no active function. But when fault or undesirable condition arrives Relay must be operated and function correctly.  A Power System consists of various electrical components like Generator, transformers, transmission l...

The authors propose a concept for protection relay systems for operation within a Smart Grid and describe the results of a prototype development. This paper introduces each of the system characteristics that should be considered for protection operation within Smart Grid, and the evaluation methods that were applied under both normal and faulted conditions. The results of a field trial in the 6...

Energization of a transformer results in sudden flow of current which is an effect of core magnetization. This current will be dominated by the presence of second harmonic, which in turn is used to segregate fault and inrush current, thus guaranteeing proper operation of the relay. This additional security in the relay sometimes obstructs or delays differential protection in a specific scenario...

To avoid undesirable disconnection of healthy wind generators (WGs) or a wind power plant, a WG protection relay should discriminate among faults, so that it can operate instantaneously for WG, connected feeder or connection bus faults, it can operate after a delay for inter-tie or grid faults, and it can avoid operating for parallel WG or adjacent feeder faults. A WG protection relay based on ...

With the evolution of Process Bus (IEC 61850-9-2), there is a need to assess the performance of protection schemes using process bus against those where traditional copper wires are implemented. Differential protection is the fundamental and most commonly used protection for transformers, motors and generators. In this paper a power system is modelled in SimPowerSystems and is executed in real-...

Microgrids comprise low voltage distribution systems with distributed energy resources (DER) and controllable loads which can operate connected to the medium voltage grid or islanded in a controlled coordinated way. This concept aims to move from “connect and forget” philosophy towards an integration of DER. Microgrids are expected to provide environmental and economic benefits for endcustomers...

Most studies in relay coordination have focused solely on coordination of overcurrent relays while distance relays are used as the main protection of transmission lines. Since, simultaneous coordination of these two types of relays can provide a better protection, in this paper, a new approach is proposed for simultaneous coordination of distance and directional overcurrent relays (D&DOCRs). Al...

Deregulation, increased loads, and limited resources/rights-of-way available for the building of new transmission lines are routinely pushing modern power transmission networks to operating limits. New generations of microprocessor relays provide design opportunities that help stressed transmission networks meet protection requirements. To verify that increasingly complex microprocessor relays ...

This paper presents big-M (penalty) method for optimum time coordination of overcurrent (OC) relays. The method is based on the simplex algorithm which is used to find optimum solution of linear programming problem (LPP). The method introduces artificial variables in the objective function to get an initial basic feasible solution (IBFS). Artificial variables are removed using iterative process...