Abstract
The growth of penetration of Distributed Generators (DGs) is increasing the risk of unwanted islanded operation in Low Voltage (LV) distribution systems. In this scenario, the existing anti-islanding protection systems, installed at the DG premises and based on classical voltage and frequency relays, are no longer effective, especially in the cases of islands characterized by a close match between generation and load. In this paper, a new protection system for islanding detection in LV distribution systems is proposed. The classical voltage and frequency relays in the DG interface protections are enriched with an innovative Smart Islanding Detector, which adopts a new passive islanding detection method. The aim is to keep the advantages of the classical relays while overcoming the problem of their limited sensitivity in detecting balanced islands. In the paper, to define the requirements of the anti-islanding protection system, the events causing the islanded operation of the LV distribution systems are firstly identified and classified. Then, referring to proposed protection system, its architecture and operation are described and, eventually, its performance is analyzed and validated by experimental laboratory tests, carried out with a hardware-in-the-loop technique.
Highlights
In distribution systems, events caused by reconfiguration, maintenance or faults can leave all or part of a Low Voltage (LV) distribution network operating without the connection to the Medium Voltage (MV) distribution system and remaining energized as an autonomous entity by the Distributed Generators (DGs) connected to the isolated grid
Events caused by reconfiguration, maintenance or faults can leave all or part of a LV distribution network operating without the connection to the Medium Voltage (MV) distribution system and remaining energized as an autonomous entity by the Distributed Generators (DGs) connected to the isolated grid
This paper proposes a new protection system for islanding detection in LV distribution systems which enriches the classical voltage and frequency relays installed at the DG premises with an innovative Smart Islanding Detector (SmartID), recently proposed from the authors to guarantee a reliable detection of the balanced islands when the classical relays fail
Summary
Events caused by reconfiguration, maintenance or faults can leave all or part of a LV distribution network operating without the connection to the Medium Voltage (MV) distribution system and remaining energized as an autonomous entity by the Distributed Generators (DGs) connected to the isolated grid. The electrical equipment can be damaged by out-of-phase closure occurring when, after a fault, the unwanted island is reconnected to the utility network by automatic reclosing of MV breakers without any synchronizing action [3] For all these reasons, the adoption of an adequate protection system able to detect any islanding condition and disconnect the DGs from the isolated network is essential to ensure the safe and secure operation of LV distribution systems. Real-Time Digital Simulator (RTDS) [11] that allows interfacing the real-time distribution system simulation with an actual SmartID device
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