How FortisTCI Uses ETAP Modeling and ETAP ILS to Mitigate Transient Stability Issues and Stabilize Power Systems

We also performed various transient stability analyses for dozens of predetermined scenarios. This scope also included an analysis of battery energy storage and its impact on frequency response, an analysis of the implementation of ETAP ILS to optimize frequency response, and a review of integrating an ETAP ILS system with our existing architecture.
Mr. Hortnel Johnson, Director of Engineering and Planning, FortisTCI Ltd.

This case study shows how the FortisTCI company sought a solution to mitigate frequency decline during diesel generator outages using the ETAP Digital Twin solution with an Intelligent Load-Shedding Scheme. The traditional under-frequency protection and PLC-based load-shedding scheme respond as per design, but their response is inadequate in preventing a further steady decline in frequency. The implementation of ETAP ILS was used to optimize the frequency response. Additionally, the study shows that a complex power system can be more stable using BESS.

 

Fortis Inc. is a Canadian electric utility holding company, based in St. John's, Newfoundland and Labrador. It operates in Canada, the United States, Central America, and the Caribbean.
FortisTCI Limited, a subsidiary of Fortis Inc., provides electricity throughout the Turks and Caicos Islands, serving Providenciales, North Caicos, Middle Caicos, South Caicos, East Caicos, and adjacent Cays. Turks and Caicos Utility Limited serves the Islands of Grand Turk and Salt Cay and was acquired by FortisTCI in 2012. Together, both companies serve over 15,000 customers and are regarded as one of the most reliable electricity providers in the Caribbean.
FortisTCI operates under the vision of Transforming Energy in the Turks and Caicos Islands.

Location: Providenciales, Turks and Caicos Islands, British Overseas Territory

Year: 2021

Optimizing mitigation strategies for system shutdown from various disturbances via the appropriate Remedial Action Scheme

Challenges

  • Finding software with the possibility to model a complicated electrical power structure with 13 Diesel generating units, ranging from 2 to 8.73MW, and an operating system frequency of 60Hz, which generate power at 4.16kV, 12.47kV, and 34.5kV. The maximum system demand is about 37.5MW. Also, over 1MW of distributed solar PV generation was installed in this network.
  • Mitigating the impact of generator outages. In June 2021, they lost one generator tripping due to a voltage-sensing issue. This was the significant disturbance that led to the overloading of the remaining units, a widespread outage, and a subsequent total system shutdown.
  • Mitigating frequency decline. During the outage, the frequency was 2.4Hz/s below the nominal frequency. They must explore solutions to optimize mitigation strategies for system shutdown on the high-quality virtual model.
  • Improve electrical analysis efficiency by allowing the analysis of various disturbances in the same model, analyzing dependencies between critical events in the grid, and making them understandable.
  • Creating an appropriate Remedial Action Scheme, according to the predetermined events in the virtual model, to improve energy production stability.
  • Analyzing the impact of distributed energy resources on the stability or instability of the network, with simulation, plotting, and visualization.

Optimization of mitigation for power system shutdown

Used applications

ETAP Digital Twin is the leading solution for modeling and working on Remedial Action Schemes. Intelligent Load Shedding (ILS™) was used to provide optimal, fast load shedding based on the system's actual operating conditions, including the type and location of the disturbances. Dynamics and Transient analysis software were used to simulate the sequence of events, including power system disturbances, and evaluate system stability.

The Sequence of Operation Viewer enables clear visualization of the processes.

Why do they use ETAP?

Main Customer Benefits

  • They created an accurate ETAP Digital Twin model. Thanks to the extensive ETAP library, all symbols and behaviors have been accurately reflected. If symbols did not exist in the ETAP models, new user-defined models would be created. For example, they made the Woodward 723 governor, which they use in our larger generating units.
  • Thanks to the ETAP solution’s flexibility, the virtual model accurately represented all equipment nameplate data and operating parameters. This was done by rigorous field data verification. The generator's dynamic data were validated and compared with the ETAP model.
  • They solved the problem with the generator's blackouts using a study and simulation on the ETAP model. Two primary issues were identified. One of them was low spinning reserve. The other was inadequate speed under frequency response. These two issues were addressed to implement more rigorous rules on frequency setting, including the frequency change rate. Also, the spinning reserve capacity increased. An initial study guided this.
  • The outage process was checked progressively, second by second, sequence by sequence. Thanks to scenarios and process viewing over time, users can observe where and when the trip can be, and why a specific event occurred. For example, researchers can see when the under-frequency relay detects a decline in frequency and why it trips. They can evaluate it in the model and check how it performs.
  • The measures were imposed on the real system. The success of these measures can be seen in an event that occurred on October 7, 2021, when they had the shedding of one generator offline under a similar condition, with the newly implemented relay settings and the higher spinning reserve. They recognize that they could maintain system stability in the end for the same kind of disturbance as it was on June 6. The frequency decline was below 1Hz/sec.
  • In the ETAP Digital Twin model, they could analyze new opportunities: using the Battery Energy Storage System and Intelligent Load-Shedding (ILS) schemes to improve fuel efficiency, minimize outages, stabilize the system, and lower spinning reserve requirements.
  • They recognize an opportunity to implement a battery energy storage system to replace the spinning reserve and reduce operating costs. It can also contribute to sustainability requirements and significantly contribute to the reduction of carbon dioxide production.
  • They found that the Intelligent Load-Shedding Scheme can provide an optimized Remedial Action Scheme, reducing the capex requirement for a battery energy system and improving stability response for disturbances.
  • An ETAP plot manager shows the results in a friendly manner. The user can plot the speed of the diesel generator depending on the frequency. The names, units, graphics, and colors are readable according to technical rules.

What do they think about ETAP?

Opinions

We collected all requisite information for the manufacturer's data to ensure our operational settings were accurate and conforming to the IEEE models. And if these models did not exist in the ETAP models, new user-defined models would be created. For example, we made the Woodward 723 governor, which we used in our larger generating units. The dynamic data was then simulated against the real-world condition and compared satisfactorily.Mr. Hortnel Johnson, Director of Engineering and Planning, FortisTCI Ltd.

The real load flow data was compared to the ETAP model and was found to be satisfactory. Our system protection settings were also updated for all components in our dynamic data validation. We ensured that we validated the generator's dynamic data.
Mr. Hortnel Johnson, Director of Engineering and Planning, FortisTCI Ltd.



Videos

Remedial Action Scheme for Integrated G-T-D System

Due to system shutdowns stemming from drastic frequency decline associated with the loss of relatively large generating units, Fortis TCI embarked on exploring opportunities to curtail these events to improve system response. This was achieved through detailed modeling and validation of system parameters with event data gathered from previous events.  Carefully implemented Remedial Action Schemes are currently explored to provide cost-saving benefits; significantly improving frequency response, without the need for larger spinning reserves and minimize investment costs for BESS.


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