How Energy Systems Group uses ETAP to evaluate ground fault trips for utility microgrid integration projects

Using ETAP, designers can model low-flow, short circuit events, minimum and peak load conditions, switching and islanding scenarios, and complete ground fault sequences to ensure that protection devices operate as intended.
Jesse Hoffman, Engineering Manager at Energy Systems Group

In this technical presentation, the potential issues are identified when adding distributed generation sources to existing power distribution systems. If not properly designed, implementing islanding microgrid capability introduces protection and control challenges. Each new generator may present a new source ground fault current to the system, which can result in unanticipated breaker operation. Energy Systems Group used ETAP to model the system and check the coordination of local and remote breakers to optimize the system, reduce downtime, and simplify troubleshooting.

The Energy Systems Group, LLC provides specialized engineering services and is headquartered in Newburgh, Indiana. With offices located throughout the U.S., ESG helps companies achieve their energy efficiency, resiliency, and sustainability goals.

Location: Newburgh, Indiana, United States

Year: 2022

Coordinating protection and control in a microgrid integration project

Challenges

1. Designing protection for islanded medium-voltage networks. Utility distribution systems behave differently when islanded: grounding references disappear, zero-sequence paths change, and traditional protection assumptions may no longer hold.

2. Ensuring correct tripping sequences during ground faults. In grid-parallel mode, reclosers typically trip first. If generator relays fail to detect ground faults before reclosing, severe out-of-phase risks can occur.

3. Selecting proper transformer winding configurations. A Δ–YG configuration can block ground fault current, preventing generator relays from detecting faults in both normal and island mode and creating temporary overvoltages on unfaulted phases.

4. Balancing utility requirements with microgrid operation. Utilities may impose YY windings, which can introduce high-impedance grounding behavior and lead to overvoltage issues in adjacent buildings unless properly analyzed.

Which solutions did they choose?

Selected applications

ETAP Protective Device Sequence-of-Operation

  • Simulates protection tripping order, reclosing behavior, relay pickups, and timing - allowing designers to visualize miscoordination before equipment is installed.

ETAP Short Circuit & Grounding Analysis

  • Models zero-sequence networks, grounding impedance, transformer behavior, and evaluates how winding configurations affect fault detection. 

ETAP Load Flow & Switching Studies

  • Evaluate minimum-load ground fault conditions, switching transitions, and islanding performance. The ETAP platform provides compatibility with both grid-connected and fully islanded electrical distribution systems.

Why do they use ETAP?

Main customer benefits

Clear visibility into generator and recloser coordination

  • ETAP reveals cases where reclosers clear faults before generator relays see ground current, exposing miscoordination that could otherwise be overlooked.

Understanding temporary overvoltage risks

  • Simulation shows unfaulted phases rising to line-to-line voltage during ungrounded or high-impedance grounded conditions - highlighting risks to surge arresters and single-phase loads.

Avoiding costly redesigns

  • ETAP enables evaluation of transformer windings (Δ–YG, YY, Δ–Δ, etc.) early in the design phase, preventing late-stage equipment replacement.

Improved protection in both normal and island modes

  • Relay settings, tripping schemes, and transfer trip options can be evaluated to ensure faults are cleared before reclosing and that islanded systems maintain a ground reference.

Better coordination across entire systems

  • ETAP considers generator grounding, utility systems, and downstream building transformers - ensuring that all components behave correctly as one system.

 

Conclusion

Fault behavior in microgrids is heavily influenced by transformer winding configuration, grounding methods, and system topology. ETAP provides the analytical tools needed to identify miscoordination, visualize ground fault sequences, validate tripping logic, and ensure both normal and islanded operation remain safe. Small checks early in design can prevent major cost and schedule impacts.

 

What do they think about ETAP?

Customer perspective

Doing some very quick checks using ETAP can prevent some pretty big cost and schedule impacts to microgrid projects.

Jesse Hoffman, Engineering Manager at Energy Systems Group



Videos

Using ETAP to Evaluate Ground Fault Trips in a Microgrid

Adding distributed generation sources to existing power distribution systems and the implementation of islanding microgrid capability introduce protection and control challenges if not properly designed. Each new generator may present a new source ground fault current to the system, which can result in unanticipated breaker operation. Energy Systems Group, was using ETAP to model the system and check coordination of local and remote breakers can reduce downtime and troubleshooting.


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