Protection coordination of over current relays in distribution system with DG and superconducting fault current limiter

Abstract

This paper proposes the use of Superconducting fault current limiter (SFCL), in conjunction with directional over current relays (OCRs) to solve the protection coordination problem in distribution systems equipped with distributed Generator (DG). The SFCL size and optimal directional OCR settings are determined in the grid connected mode. The proposed approach is tested on the IEEE 34 node distribution system in which 26 OCRs are placed. On the occurrence of fault, level of fault current changes which in turn changes the operating time of various OCRs. Therefore, it is important to calculate and suggest method of the relay setting in order to minimize the operating time of relays and also to avoid the mal-operation. SFCL reduces the magnitude of short circuit current on the occurrence of fault and ultimately retains the coordination among various directional over current relays.

Method to resolve false trip of non‐directional overcurrent relays in radial networks equipped with distributed generators

“…Constraints which should be observed in the optimisation process are: In (9), relay x indicates a relay which should operate for a time equal to the CTI later than relay y for an SC in the PZ y . Furthermore, SSP i (the set of selection pairs) includes all relay numbers x and y that have been chosen for the coordination of relays in the intended network…”

“…Electromechanical relays have more delay compared to digital ones and therefore different CTIs. Hence, if the relay x in (9) is an electromechanical relay, (9) should have a different CTI compared to the case where relay x is the digital ones.…”

“…The optimisation algorithm must detect and select the proper characteristic type. In this case, constraint (13) should be added to the optimisation constraints (9) and (10) relay type(i) ∈ Standard Characteristics (13) Non-standard characteristic: In this case, the variables K and α are not constant and could change within a given range, to optimise the result. From Table 2, it can be seen that the minimum and maximum values of K are 0.05 and 120, and the minimum and maximum values of α are 0.02 and 2.…”

“…The authors in [6] have prevented the IBDGs injected current increasing during a fault by applying a multi-loop control strategy, and so prevented the false trip occurrence. In [7,8], fault current limiter (FCL) has been employed to limit the SC current injected from DGs and also publish protection constraints; and in [9] a superconducting FCL is used for preventing the false trip occurrence.…”

µPMU-based smart adaptive protection scheme for microgrids

“…However, power electronic interface used with RESs limits the fault current within 1.2-1.3 rated current [6]. The conventional overcurrent protection system does not recognize the fault during islanded operation mode since it lies on the long-time tripping of overcurrent relay characteristics curve [7]. For a better protection, the system needs to be smart and carries out online system protection with fast tracking online measurement.…”