21-06-2012, 02:49 PM
Application of a Fault Current Limiter To Minimize Distributed Generation Impact on Coordinated Relay Protection
Application of a Fault Current Limiter To Minimize Distributed Generation.docx (Size: 21.26 KB / Downloads: 36)
Abstract
Radial power distribution systems, common in North America, typically use coordinated relay protection for fault protection. However, the rising interest in distributed generation (DG) poses a problem, as DG causes such systems
to lose their radial nature, disrupting the coordinated relayprotection.
The use of a fault current limiter (FCL) is proposed to limit the effect of the DG on the coordinated relay protection scheme in a radial system during a fault. This paper shows that the FCL enhances the stability of and limits the transient stresses
on the DG. Such a device is only recently more plausible with the ongoing developments of a new hybrid mechanical/electrical fault current limiter.
INTRODUCTION
THE majority of distribution systems in North America are operated in a radial configuration, predominant because of the simplicity of their operation and the economy of the overcurrent protection [1], [2]. Both of these advantages are due to the fact that in any branch of a radial system, power only flows in one direction.
In such distribution systems, the protection equipment needs only to sense current, with no need to detect direction [2]. Commonly used for protection are inverse time overcurrent
relays [3], set up for relay coordination [2], [4], [5].
The purpose of relay coordination is to provide a reliable and redundant protection scheme, while minimizing the disruption to customers [1].
Protection Problem Caused by Introduction of DG to Radial System
With the introduction of DG into a radial distribution system, the radial power flow nature is lost [10]. Depending on the loading conditions, it may not be possible to recoordinate the relays [4]. It is well known that protection devices in a multisource system need to be direction-sensitive [2], [3], and the relays must be coordinated for faults where the current may flow in either direction .
. Existing Proposed Solutions
Several ideas have been introduced as possible solutions to the problem of relay overcurrent protection in systems with DG, including microprocessor based reclosers [12] and adaptive protection [3]. While these solutions may technically work, they involve very high initial equipment costs: to replace.
New Approach - Fault Current Limiter
Most of the proposed solutions for the described problem involve modifying the existing protection scheme to accommodate the DG. Such solutions tend to be expensive to implement because of equipment costs, which reduces the benefit of adding DG.
An alternative approach would be to consider the idea to negate or, at the very least, minimize the contribution of the DG during a fault, while adding no adverse effects to the
network during normal steady state non-fault operation. Thus, a proposed solution is to implement a fault current limiter that .