Technical Presentations

Time-Domain Protection Scheme for Microgrids with Aggregated Inverter-Based Distributed Energy Resources897

Abstract
This paper proposes a time-domain-based protection scheme for radial and loop microgrid systems with inverter-based resources (IBRs), such as solar photovoltaic (PV) systems and type-4 wind turbines. ... see moreThe protection scheme is designed to function during both grid-interconnected and grid-isolated modes. The proposed scheme provides an ultra-high-speed sub-cycle directional element aided with low bandwidth communication between relays. Like directional comparison schemes, relays identify whether faults are in-zone or out-zone. The directional element is based on time-domain superimposed quantities and Park`s transformation algorithms. Specifically, the element calculates the superimposed positive-sequence direct component of transient energy during faults. Superimposed voltage and current quantities are calculated using delta filters and decoupled double synchronous reference frame (DDSRF) filters. The proposed filtering method improves the reliability of the superimposed directional element when IBRs are the main source of fault current. The protection scheme is evaluated on a modified IEEE 34-bus distribution system simulated using an electromagnetic transients program (EMTP).

Tag(s): Microgrid, Protection Scheme, Inverter-Based Resources (IBRs)

Distributed Energy Resources Large-scale Integration Impacts on the Distribution System Protection902

Abstract
This presentation examines the impact of high DER penetration, particularly PV systems, on EPDS protection reliability. Instead of concentrating DERs in specific nodes, they are distributed along an u... see morenbalanced feeder with single-phase and three-phase PV systems. Various fault types, including impedance faults, were analyzed using the IEEE 34-node test feeder in EMTP-RV. Three scenarios were considered: (i) without DERs, (ii) 50% DER penetration with protection set by rated load, and (iii) 50% DER penetration with protection set by conductor capacity. Results showed reduced feeder relay currents for three-phase and phase-to-phase faults and significant decreases for phase-to-ground faults with impedance, leading to relay blindness and delayed protection operation. These insights support utilities in adapting EPDS protection systems for DER integration.

Tag(s): Distributed Energy Resources, Photovoltaic Systems, Protection System Coordination, Fault Detection

Ground Fault Overvoltage with Inverter-Based Distributed Energy Resources841

Abstract
A Ground Fault Overvoltage (GFO) can occur in situations where an ungrounded transmission line and associated ungrounded transmission equipment is energized from distribution connected Distributed En... see moreergy Resource (DER) during a transmission single-phase-to-ground (SLG) fault. The condition could result in 1.73 pu overvoltage on phase to ground connected equipment which will be sustained until the DER ceases to energize the substation distribution transformer. Transmission equipment on the isolated circuit will be subjected to the above phase to ground overvoltage, also if there is frequency shift, the isolating transmission circuit breakers could potentially see up to 2.73 pu phase to ground overvoltage. Such an overvoltage can cause damage to customer or utility equipment and must be avoided. GFO concerns are already becoming a barrier to large-scale DER deployment either by posing low hosting capacity or by necessitating installation of costly mitigation equipment. Utilities need to study GFO risks and identify low-cost mitigation options to enable large-scale DER deployment. Given the fundamental differences in mechanisms and phenomena driving a GFO under DERs, classical GFO analysis methods do not apply to inverters, and advanced simulation methods and tools are required.


This presentation highlights EPRI’s work on GFO analysis, concerns, and evaluation of mitigation options using EMTP. The objective is to determine if or when high DER penetration presents a GFO problem and how to prioritize the mitigation and equipment evaluation. This includes evaluating the impact lightning arresters can have in reducing or clamping the overvoltage, the application and performance of high voltage substation overvoltage protection, and DER on-board voltage/frequency protection. The presentation further provides modeling recommendations for such a study using EMTP. As DER deployment increases, utilities will need to perform similar analysis to identify potential overvoltage risks and develop low-cost mitigation methods. This work provides a basis for such a study.

Tag(s): gfov, tov, ibr, DER, inverter, islanding, load rejection, inverter based resources

EMT models to evaluate traveling wave based protection in distribution system767

Abstract
This presentation will discuss the need for using wide-band models to model the traveling wave phenomenon in the distribution system. The distribution system is going through significant changes. On... see moree of them is the high penetration of inverter-based distributed energy resources in the distribution system. Due to this high penetration, there is a need for a better protection system. Multiple organizations are working on creating novel protection techniques for distribution systems with high penetration of inverter-based DERs. One such innovative method is the use of traveling waves to detect and locate faults. Transmission system protection utilizes this approach, and commercial solutions exist for the transmission system. Using this approach in the distribution system is not straightforward and presents some challenges for implementation.