The Under-frequency Load Shedding (UFLS) scheme has been used by utility companies around the world to mitigate frequency drop caused by simultaneous or cascading tripping of transmission lines and/or generators in a power system. In the effort to devise an optimal load shedding scheme, it is imperative that investigations are done on the many factors that may affect the response of the scheme ...

In this paper, Swarm Evolutionary Programming (SEP) method incorporating modified System Frequency Response (SFR) model is proposed to solve the optimal Under-frequency Load Shedding (UFLS) scheme design problem. The objective function of this problem is to minimize transient frequency and steady-state frequency deviation from nominal and total quantum of load shedding. The constrained optimiza...

This paper proposes a new adaptive underfrequency load shedding scheme (UFLS) to avoid frequency instability in electrical power system during abnormal wide area disturbances. The developed is based on online monitoring of the distance relay zone 3 decisions some tie lines using (WAMS) and SCADA/EMS systems, check rapidly reliably uncontrolled islanding conditions and, permit an automatic actio...

Large frequency deviations after islanding are exceedingly critical in small receiving-end power systems. The under-frequency load shedding (UFLS) scheme is an efficient protection step for preventing system black outs. It is very important to get an exact model to design the UFLS schemes. In this paper, an optimization model to achieve the system frequency response (SFR) model either from the ...

The frequency of power system is very sensitive to load changing when operating in islanded mode. This may causes overloading or loss of generation cases. Under-Frequency Load Shedding (UFLS) Scheme is commonly applied to stabilize the frequency during these cases. Conventional UFLS scheme operates successfully in interconnected grid system and may not work well when applied to DG based system ...

UNLABELLED The aim of the study was to determine the occurrence of UFLs and the dynamics of their development, as well as to evaluate the histopathology and relationship with regressive stromal changes. 3750 uterine specimens were reviewed during the period between 1984 and 2003. In the examined series of 3750 uteruses removed due to tumors or prolapse, 50 cases with four types of changes were ...

Represented by wind turbines and ultra high-voltage DC (UHVDC), the power-electronic interfaced power sources participate in fast frequency control, which has a significant impact on system frequency. However, conventional under-frequency load shedding (UFLS) scheme doesn’t take into account above, resulting unreasonable after large loss of generation. To this end, article proposes an adaptive ...

In order to analyse the possibilities of improving grid stability on island systems by local demand response mechanisms, a multi-agent simulation model is presented. To support the primary reserve, an under-frequency load shedding (UFLS) using refrigerator loads is modelled. The model represents the system at multiple scales, by recreating each refrigerator individually, and coupling the whole ...