A critical review of the state‐of‐art schemes for under voltage load shedding

Abstract

Summary A blackout is usually the result of increasing load beyond the transmission capacity of the power system. One of the main reasons for power blackouts is voltage collapse. To avoid this problem, the proper corrective measures called load shedding is required. In critical and extreme emergencies, under voltage load shedding (UVLS) is performed as a final remedy to avoid a larger scale voltage collapse. Therefore, UVLS is considered state of the art to achieve voltage stability. This review summarizes and updates the important aspects of UVLS; it also provides principle understanding of UVLS, which are critical in planning such defense schemes. Moreover, this article provides a discussion on recent state‐of‐art UVLS schemes applied in various power industries. Additionally, the pros and cons of the conventional and computational intelligence techniques are discussed. It is envisioned that this work will serve as one‐stop information for power system engineers, designers, and researches.

An adaptive decentralized under voltage load shedding in distribution networks

“…Several UVLS techniques exist. Conventional UVLS schemes are the most widely used in electric utilities 5,6 . This technique can lead to insufficient or excessive load shedding and does not differentiate between loads or buses by their priorities.…”

“…A centralized scheme has undervoltage relays installed at key system locations within an area, and the tripping signals are transmitted from a control center, to shed appropriate load amount at various locations 7 . These arrangements are known as special protection scheme , 5,7 and wide area protection scheme. On the other hand, in the decentralized schemes the UVLS relays operates at the selected location when voltage drops below a threshold value without the need of a centralized decision making 5‐8 …”

A validation approach for short‐circuit currents calculation in large‐scale power systems

“…[15][16][17] In this regard, the improvement of adequacy of SCC calculations is an extremely important task, particularly as, according to the statistic, short circuit (SC) is one of the most frequent and dangerous accidents in EPS, which can cause blackouts. 18,19 The rest of the paper is organized as follows. The problem of numerical simulation of large-scale power systems is discussed in Section 2.…”

Enhancing the reliability of six‐phase transmission line protection using power quality informatics with real‐time validation

“…Another challenge with regard to providing protection for nonlinear loads concerns distinguishing between dynamic encroachment events such as sudden load switching from symmetrical fault conditions. The similar current and voltage following encroachment events and symmetrical faults cause conventional overcurrent and distance relays to maloperate during sudden change in loading conditions, by either failing to trip for a fault or tripping under healthy condition …”

“…The similar current and voltage following encroachment events and symmetrical faults cause conventional overcurrent and distance relays to maloperate during sudden change in loading conditions, by either failing to trip for a fault or tripping under healthy condition. 17,18 Motivated by the effectiveness of the six-phase system in meeting enhanced power demand, the present works aims at development of a reliable protection scheme for a six-phase system, which can operate satisfactorily under varying linear/nonlinear loading and different power system contingencies. A novel scheme based on the online estimation of power quality informatics has been proposed in this paper.…”