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Archives for Interconnection Studies

Pterra Conducts Interconnection Assessment for New York Great Lakes Wind Energy Feasibility Study

In December 2022, the New York State Energy Research and Development Authority (NYSERDA) published a report on the Great Lakes Wind (GLW) energy feasibility based on a study conducted by the National Renewable Energy Laboratory (NREL), Advisian Worley Group, Brattle Group and Pterra Consulting.  This study (link to the full report) was intended to complement the options for renewable resources such as land-based wind, solar, hydro and offshore wind that would help meet New York’s renewable energy portfolio and decarbonization goals under the New York State Climate Act.

New York State is bounded by two of the Great Lakes, Lake Erie to the west and Lake Ontario to the north. The potential for developing fixed and floating wind turbines on the lakes using both existing and emerging technologies was the focus of the feasibility study. The study examined myriad issues, including environmental, maritime, economic, and social implications of wind energy areas in these bodies of freshwater and the potential contributions of offshore GLW projects.

Pterra’s role in the study (link to interconnection report) was to conduct a feasibility assessment for potential interconnections of GLW generation with the New York Bulk Power System (NYBPS). To perform the assessment, Pterra developed power flow models to represent the NYBPS in 2030 with an assumed renewable generation buildout.

To provide a measure of interconnection capacity, the capacity headroom definition and calculation method described in recent New York State Public Service Commission orders were selected. Potential points of interconnection (POIs) on the existing NYBPS substations located within 20 miles of either the Lake Erie or Lake Ontario shoreline were initially selected for analysis. These were filtered down to a few representative POIs for more detailed analysis. (Headroom represents the potential capability for GLW to interconnect; however, it also represents the capacity that is available to any other generation resource that may want to interconnect at the same POI. The nature of the NYISO market for any new generation is competitive and GLW is expected to compete with other resource development modeling analyses to utilize the available headroom.)

Lake Erie abuts the New York counties of Erie in the north and Chautauqua in the south. For Lake Erie GLW, the available POIs showed combined capacity headroom of 270 megawatts (MW) without transmission upgrades. Applying a set of simple transmission upgrades costing some $68.8 million can increase the Lake Erie total headroom capacity by 60 MW to 330 MW.

New York State has a longer shoreline along Lake Ontario compared to Lake Erie. Several New York State counties border the lake, including Niagara, Orleans, Monroe, Wayne, Cayuga, Oswego and Jefferson. For Lake Ontario GLW, several POIs in Monroe and Oswego counties showed solo headroom capacity in the range of 850 to 1100 MW without the need for transmission upgrades. At most, there is a total headroom capacity of up to 1140 MW for the Lake Ontario POIs. The total headroom capacity may be increased by 140 MW by implementing simple upgrades costing some $236.6m. In Jefferson County, the studied POIs showed no solo headroom capacity. Simple transmission upgrades costing at least $164.5 million may open about 50 MW of headroom capacity.

Pterra’s interconnection assessment found that there is some headroom capacity on the NYBPS for which GLW can compete for the delivery of energy to the grid. In order to access the POIs with headroom, other reliability issues relating to transient voltage, stability, short circuit, deliverability, transfer capability and higher-level contingencies would also need to be considered.

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Benchmarking Phasor and EMT Models for Inverter-Based Energy Resources

By Francis Luces, Ric Austria

Power projects planning to participate in the wholesale market are required to undergo impact studies as part of the interconnection application process. The studies, as a minimum, evaluate the performance of the projects under instantaneous, steady-state and transient conditions. The timescales of phenomena and equipment studied are as illustrated in Figure 1.

In the specific case of transient studies, the impact of a proposed project on the voltage and frequency control capability of the overall grid is evaluated. Traditionally, it was sufficient to consider a timeframe of 0.5 to 10 Hz (10-100 msec) for a type of study known as transient stability. The computer models (and software, such as PSS/E and PSLF) used to conduct these studies are known as phasor-based models. These models capture phenomena limited to the target timeframe.

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System Impact Study for a Proposed Transmission Interconnection Project in New York

By R. Tapia, M. Gutierrez and M. Infantado


Independent System Operators (ISO) constantly face the challenge of assessing the impact of facility additions to the power grid. They normally require a system impact study for any proposed interconnection of a large generating plant or transmission project. The purpose of this analytical study is to determine the potential adverse impacts of the interconnection of transmission facilities to a power system and whether it would cause any of the following:

  • Post-contingency thermal overloading on transmission lines and transformers,
  • Voltage criteria violations on substations,
  • Negative impact on the dynamic response of power system facilities,
  • Degradation on the transfer limit of transmission interfaces,
  • Increase in substation short circuit current that could possibly exceed the fault duty of existing circuit breakers.

The system impact study determines the impact of the proposed project by comparing simulation results of the case with the project in service against the case without the project. If adverse impacts were to be found, appropriate solutions to mitigate the violations would be required, except for the extreme contingency assessment which is performed for information purposes on issues such as avoidance of widespread load interruptions, uncontrolled cascading, and system blackouts among others.

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Siting of Power Plants: A Thermal Capacity Assessment for Grid Interconnection

by Francis Luces


For developers of power plants, one of the important factors to consider is where and how to interconnect a plant to an existing transmission network in order to reliably deliver its full output. For conventional power plants (i.e. coal, oil, natural gas, etc.), the availability of fuel supply and environmental permitting are the main considerations for siting. In the case of solar photovoltaic (PV) projects, given the availability of land area for mounting solar panels and sufficient solar irradiance, the point of interconnection (POI) to the grid can be the determining factor for siting. An assessment of the thermal capacity at potential POIs provides an effective screen for potential sites. Using transmission capacity injection analysis, developers can swiftly determine the capability of the existing network to support additional power from a new source such as a PV project. With this type of analysis, solar power project developers can know fairly early in the development process if the selected site and POI can support the plant’s output.

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