Power-system protection

About: Power-system protection is a research topic. Over the lifetime, 6353 publications have been published within this topic receiving 117961 citations.

TCSC impact on communication-aided distance-protection schemes and its mitigation

Abstract: The paper analyses the impact of the thyristor-controlled series capacitor (TCSC) on the performance of conventional communication-aided distance-protection schemes and proposes new schemes for its mitigation. The associated TCSC control actions introduce rapid changes that create certain problems in the primary-system parameters such as line impedances and load currents, causing the apparent impedance seen by the distance relay to be affected during the fault period; hence the positive-sequence impedance measured by the traditional stand-alone distance relays is no longer an indicator of the distance to a fault. It is shown that communication-aided distance-protection schemes that perform successfully in lines with fixed series capacitors have problems in lines with TCSC. This impact is observed not only on the relays of the compensated line with TCSC, but also on the relays of adjacent lines. Mitigation of this problem is proposed by using new communication-aided schemes. The proposed schemes use the information available at the substation to inhibit relay malfunctions. The performance of the techniques is studied for different TCSC locations in the transmission line. Real-time digital simulation and commercial relays are used to perform the analysis. The results indicate the effectiveness of the proposed methods to be applied in the power systems equipped with TCSC.

Impact of Inverter-Based Resources on Negative Sequence Quantities-Based Protection Elements

Abstract: Inverter-Based Resources (IBRs), including Wind turbine generators (WTGs), exhibit substantially different negative-sequence fault current characteristics compared to synchronous generators (SGs). These differences may cause misoperation of customary negative-sequence-based protective elements set under the assumption of a conventional SG dominated power system. The amplitude of the negative-sequence fault current of a WTG is smaller than that of an SG. This may lead to misoperation of the negative-sequence overcurrent elements 50Q/51Q. Moreover, the angular relation of the negative-sequence current and voltage is different under WTGs, which may result in the misoperation of directional negative-sequence overcurrent element 67Q. This paper first studies the key differences between the WTGs and SG by comparing their equivalent negative-sequence impedances with SG's. Then, simulation case studies are presented showing the misoperation of 50Q and 67Q due to wind generation and the corresponding impact on communication-assisted protection and fault identification scheme (FID). The impact on directional element is also experimentally validated in a hardware-in-the-loop real-time simulation set up using a physical relay. Finally, the paper studies the impact of various factors such as WTG type (Type-III/Type-IV) and Type-IV WTG control scheme (coupled/decoupled sequence) to determine the key features that need to be considered in practical protection studies. The objective is to show potential protection misoperation issues, identify the cause, and propose potential solutions.

Impact studies of distributed generation on power quality and protection setup of an existing distribution network

Abstract: The increasing amount of distributed generation (DG) in distribution networks (DNs) is giving rise to power quality and protection coordination problems. Issues like voltage regulation, flicker, harmonics and loss of coordination between circuit breaker and fuse need to be addressed for integration of DG into DN. This paper discusses these issues with a special emphasis on protection coordination problems. A typical DN with DG is modeled and simulation results for impact of DG on protection system coordination are presented and discussed here. Some solutions are proposed to cope with these problems.

Monitoring of Power System Topology in Real-Time

Abstract: Power system topology is defined by the connectivity among power system components such as generators, power transformers, transmission lines, loads, etc. The knowledge about topology is important for correct execution of many monitoring, control and protection actions. This paper introduces an approach that assures accurate determination of the topology in real-time. To be able to justify why this approach is important, the paper gives a background of the topology determination problem and discusses the impact on various application functions. An implementation of the proposed approach consisting of hardware and software modules is outlined. Examples of the functional improvements due to the increased accuracy of topology determination at both the substation and system-wide level are presented at the end.

Network impacts of high penetration of photovoltaic solar power systems

Abstract: The impacts of PV power plants are associated with voltage profiles, electrical losses, power factor, capacity planning, power quality, system operations and protection. Currently utility-scale solar PV plants have nominal capacities that are compatible with distribution substation MVA ratings e.g., between 1 MVA and 10 MVA, plans are to develop transmission interconnected PV plants in the 50 – 100 MW power range. These distribution network impacts are discussed and mitigation solutions are provided. A case study of a feeder fully loaded with PV power plants will be discussed.