Parameter Optimization of SFCL With Wind-Turbine Generation System Based on Its Protective Coordination

Abstract

This paper describes a study to determine the optimal resistance of a superconducting fault current limiter (SFCL) connected to a wind-turbine generation system (WTGS) in series considering its protective coordination. The connection of the WTGS to the electric power grid may have serious effects on the stability and reliability of the overall system during a contingency due to the increase in fault currents. Moreover, it causes malfunction in the protective devices such as overcurrent relays (OCRs). To deal with this problem, the SFCL is applied to reduce the level of fault current increased by the connection of the WTGS. Then, to determine the optimal parameter of the SFCL, protective coordination between the existing multiple OCRs is considered based on the computation of fault current by the equivalent voltage source method.The effectiveness of the optimal resistance for the SFCL is evaluated by the time-domain simulation with the power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC) software. The results show that protective coordination is well maintained without changing the previous settings of existing OCRs by applying the SFCL with its optimal parameter. Therefore, the system can keep its suitable reliability even when the level of fault current is increased by connecting the WTGS to the power system. Index Terms-Equivalent voltage source method, overcurrent relay, protective coordination, short-circuit current, superconducting fault current limiter, wind-turbine generation system.

Optimal location and minimum number of superconducting fault current limiters for the protection of power grids

“…In fact, during the normal operation of the power system, i.e., before the occurrence of a fault (t < t f ), and after its full clearance and later recovery of superconducting properties (t ≥ t f c + t r ), the resistive impedance of the SFCL is nearly invisible to the load flow. Therefore, it is reasonable to assume that under these conditions the SFCL acts as a small resistance defined by R n = 10 −6 Ω [10,16]. Then, the fault pro-tection capabilities of the SFCL are captured by modelling the quenching properties of the superconducting material beyond the steady-state conditions [12], where the time-dependance comes into play either via a simplified exponential function for the resistance dynamics of the SFCL under fault conditions [9,17,18], or a temperature dependent E − J power law describing the flux-creep and flux-flow properties of the superconducting material [19,20].…”

Adaptive Protection Algorithm for Overcurrent Relay in Distribution System with DG

“…This problem becomes more serious if multiple DGs are connected to the system. In particular, the pre-determined coordination between the OCRs is affected by the increased fault current due to the connection of DGs and its reverse flow [1][2][3][4]. To solve this problem, a new adaptive protection algorithm is proposed utilizing the capabilities of the digital protection relay such as intelligent electronic device (IED).…”

“…The OCR transfers a trip signal when the fault current exceeds a pre-determined pick-up current, I pick-up . Its inverse-time current characteristic is expressed as (1) and (2), which present the dynamics of induction disk OCR [10].…”

“…If the fault occurs at the fault location, F3 on the adjacent feeder, its magnitude sensed by OCR-n also becomes larger since the fault current from DG flows reversely to the F3. Therefore, the OCR-n might function incorrectly unless its operating parameters are changed properly [2,4,12]. In summary, the increased fault current can have the undesirable effect on the operation of OCRs in the distribution system.…”

Applying superconductive fault current limiter to minimize the impacts of Distributed Generation on the distribution protection systems

“…Further the instantaneous voltage sag on the normal lines can be prevented. Reference [7] describes a study to determine the optimal resistance of a SFCL connected to a wind-turbine generation system in series considering its protective coordination. In [8], the protection coordination of the protective devices with a SFCL due to the DG introduction in a power distribution system was analyzed through short-circuit tests for the simulated power distribution system, which was comprised of the transformer, the DG, the distribution line and the load, protected by the protective devices and the SFCL.…”