Mohamed Elsamahy

Impact of Superconducting Fault Current Limiters on the Coordination Between Generator Distance Phase Backup Protection and Generator Capability Curves

In this paper, investigations are carried out to explore the impact of superconducting fault current limiters installed in the transmission system on the coordination between the generator distance phase backup protection (function 21) and the generator capability curve. The results of these investigations have shown that both the resistive and inductive type superconducting fault current limiters have an adverse effect on this coordination. Such an impact varies according to the fault type, the fault location, and the generator loading. The dynamic simulations of a test benchmark have been conducted by using the PSCAD/EMTDC software.

Impact of midpoint STATCOM on the coordination between generator distance phase backup protection and generator capability curves

In this paper, investigations are carried out to explore the impact of a midpoint STATCOM on the coordination between the generator distance phase backup protection (function 21) and the generator capability curve. The results of these investigations have shown that the midpoint STATCOM has an adverse effect on such coordination. Such an impact varies according to the fault type, the fault location and the generator loading. The dynamic simulations of a test benchmark have been conducted using the PSCAD/EMTDC software.

A Novel Reclosing Scheme for Mitigation of Distributed Generation Effects on Overcurrent Protection

This paper proposes a novel scheme to mitigate distributed generation (DG) effects on existing fuse-recloser protection infrastructure in radial distribution networks. The proposed scheme employs a control unit, variable load bank, and dedicated recloser at the point of common coupling (PCC). It detects the increase in the DG terminal current producing a tipping signal when it exceeds a preset value. The proposed scheme also receives a fault detection signal from the head-end recloser via a fast communication channel. Upon verifying both signals, the scheme disconnects the DG unit from the system. Simultaneously, it connects a transfer impedance at the PCC to operate the DG unit at its prefault load-sharing condition. This allows the DG unit to continue supply to the transfer impedance at the prefault load-sharing condition, that is, maintain operation at the prefault level with no need for immediate shut down. Furthermore, it also allows the DG to maintain its speed and frequency at the prefault levels which, in turn, allows faster reconnection of the DG unit to the system after successful reclosing. For the case of unsuccessful reclosing or the case where the fault is not cleared within the set utility time set frame, the proposed scheme shuts the DG source down. The transfer impedance is selected from a variable load bank and is a function of the prefault load-sharing condition; therefore, a sensitivity survey was performed during the investigations of this paper to cover all possible system operating conditions and its corresponding transfer impedances. In the context of this paper, multiple in-depth time-domain simulations are conducted to ascertain the efficiency of the proposed scheme in mitigating the impact of DG sources on existing overcurrent protection infrastructure. Time-domain simulations have been conducted using a typical distribution network in the EMTP-RV software environment for validation purposes.

Fault impedance effects on distributed generation influences in overcurrent protection

This paper investigates the effect of varying fault impedances in the context of Distributed Generation (DG) influences on distribution overcurrent protection infrastructure (specifically fuse-recloser protection). The assessment includes an investigation into a DG source integration evaluation method to determine the effects of varying fault impedances. The assessment and evaluation techniques used are demonstrated through time-domain simulations in the EMTP-RV software environment on a typical distribution network.

Impact of Generator Distance Phase Backup Protection on Generator Overexcitation Thermal Capability during System Disturbances

In this paper investigations are carried out to explore the generalization of the adverse impact of the existing setting of the generator distance phase backup protection (Relay (21)) according to the existing standards on generator over excitation thermal capability during system disturbances. These investigations are conducted in two stages, the first includes a SMIB system incorporating a midpoint STATCOM in order to increasing its power transfer capability. The second includes a multi-generator power plant configuration. Both stages have included the performance of Relay (21), during two common system disturbances, namely a system fault and a sudden application of a large system load while the generator over excitation limiter (OEL) is in service. The results of this paper have generalized the restricting impact of the current setting of Relay (21) on the over excitation thermal capability of the generator during system disturbances. Moreover, results also have proven that in-depth stability studies are of high paramount for selecting Relay (21) setting which will allow the generator to ful fill adequate level of voltage stability during system disturbances.

Impact of phase-imbalanced series capacitive compensation on the transient recovery voltage

This paper explores the impact of phase-imbalanced series capacitive compensation schemes on the Transient Recovery and Rate of Rise of Recovery voltages of high-voltage circuit breakers in series capacitive compensation transmission systems. The paper presents a comparison between the TRV and RRRV levels in both phase-imbalanced and symmetrical series capacitive compensations for different fault types and locations. Time-domain simulation studies were performed using the EMTP-RV.