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.

Overcurrent Protection in DC Zonal Shipboard Power Systems using Solid State Protection Devices

Abstract: In this paper, potential solutions to address the protection challenges in DC Shipboard Power Systems (SPSs) have been investigated. Two different options have been considered. The first option involves the use of Solid-State Circuit Breakers (SSCBs) for fault current limiting and interruption. Simulations on a prototype DC SPS have been performed to assess the performance of a SSCB. It is shown that the SSCB can interrupt the fault current very fast, within 20 milliseconds. The second option considered involves the use of Voltage Source Converter (VSC) themselves to act like crowbars. The simulations on the prototype system have been performed to assess the feasibility and effectiveness of this approach. It is shown that this is an effective method provided that VSC switches are properly chosen for it.

Investigation of ground-fault protection devices for photovoltaic power system applications

Abstract: Photovoltaic (PV) power systems, like other electrical systems, may be subject to unexpected ground faults. Installed PV systems always have invisible elements other than those indicated by their electrical schematics. Stray inductance, capacitance and resistance are distributed throughout the system. Leakage currents associated with the PV modules, the interconnected array, wires, surge protection devices and conduit add up and can become large enough to look like a ground-fault. PV systems are frequently connected to other sources of power or energy storage such as batteries, standby generators, and the utility grid. This complex arrangement of distributed power and energy sources, distributed impedance and proximity to other sources of power requires sensing of ground faults and proper reaction by the ground-fault protection devices. The different DC grounding requirements (country to country) often add more confusion to the situation. This paper discusses the ground-fault issues associated with both the DC and AC side of PV systems and presents test results and operational impacts of backfeeding commercially available AC ground-fault protection devices under various modes of operation. Further, the measured effects of backfeeding the tripped ground-fault devices for periods of time comparable to anti-islanding allowances for utility interconnection of PV inverters in the United States are reported.

Contingency analysis of power system by using voltage and active power performance index

Abstract: Now a days power system protection is an important task for an operating engineer, which can be done by doing online security assessment. Contingency analysis is one of the best methods to forecast the condition of power system if any unwanted event occured in the power system. To do contingency analysis first the operator has to know the parameters like voltage, power and voltage angle at each and every bus by doing load flow analysis on the system. Newton Raphson method is the best load flow method as it gives accurate results in less time. In this paper all line outage contingencies in a standard 6 bus and 5 bus power system has been done in MATLAB environment. For each line outage contingency, load flow analysis has been done on the system and the active power and voltage performance indices have been calculated. These two performance indices will give the idea about the change in active power flow through the lines and voltages at the buses for a particular line outage. Summation of these two indices will give the performance index value through which ranking of severity will be given to the lines. And from the load flow results comparison has been done between low rank and high rank line outage contingencies. This contingency analysis helps the operational engineer to know which line outage is dangerous to the system and what prior action is to be taken to minimize the effect of that particular line outage.

Quality-of-Service Considerations in Utility Communication Networks

Abstract: This paper discusses the impact that communication will have on the electric power grid in the future. Recent efforts, such as UCA 2.0 and IEC 61850, are establishing a standard way for electric power substations, intelligent electronic devices, and other apparatus to communicate over data networks. These efforts pave the way to a future where protection and control of the electric power grid will migrate towards a common utility intranet. The intranet will almost certainly be based on Internet standards due to their widespread use, low cost, and easy migration path over time. A utility intranet, common to the utilities but separate from the Internet, will allow for the eventual connection of regional substations, equipment, and control centers throughout the grid. The transition will allow capabilities beyond what is currently available, but it requires a careful understanding of the implications for network capacity constraints, protocol selections, and quality-of-service technologies. This paper discusses the benefits of utility communication, the likely pitfalls in the use of Internet technology for protection and control systems, and technologies that can help to mitigate those pitfalls. This paper also introduces a model for the expected background traffic that will be present in a utility intranet. Experimental results illustrate the use of different communications protocols in representative power situations in the face of different levels of background traffic in the electric power and communication synchronizing simulator simulation environment.

Analysis of Energy Dissipation in Resistive Superconducting Fault-Current Limiters for Optimal Power System Performance

Abstract: Fault levels in electrical distribution systems are rising due to the increasing presence of distributed generation, and this rising trend is expected to continue in the future. Superconducting fault-current limiters (SFCLs) are a promising solution to this problem. This paper describes the factors that govern the selection of optimal SFCL resistance. The total energy dissipated in an SFCL during a fault is particularly important for estimating the recovery time of the SFCL; the recovery time affects the design, planning, and operation of electrical systems using SFCLs to manage fault levels. Generic equations for energy dissipation are established in terms of fault duration, SFCL resistance, source impedance, source voltage, and fault inception angles. Furthermore, using an analysis that is independent of superconductor material, it is shown that the minimum required volume of superconductors linearly varies with SFCL resistance but, for a given level of fault-current limitation and power rating, is independent of system voltage and superconductor resistivity. Hence, there is a compromise between a shorter recovery time, which is desirable, and the cost of the volume of superconducting material needed for the resistance required to achieve the shorter recovery time.