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NISAC  National Infrastructure Simulation and Analysis Center




NISAC Tools: EPRAM

EPRAM: Electric Restoration Analysis

Overview

The EPRAM electric restoration analysis model is used to determine the impact of network-level damage on electric power restoration by analyzing work rates and substation priorities, critical path activities, and time to restore.

Model Characteristics

  • National-scale data coverage
  • Cellular automata (CA) technique
  • Simulates work management practices used by electric utilities during a variety of natural and manmade events

EPRAM utilizes a cellular automata approach built on geo-spatial representations of electric substation service areas. Service areas are initially modeled as contiguous polygons at “normal” status. During a damage event, service areas progress from “outaged” to “partially restored” to “fully restored.” The model incorporates constraints such as priority scheduling of field crews, availability of spares, line switching, and generator black-start options, travel time across damaged areas, and the extent of debris. EPRAM provides a variety of outputs such as charts of aggregate event (time to restoration); geo-spatial restoration sequences; tabular lists of critical facility impacts; and work crew assignments.

Where Is the Tool Applied?

EPRAM has been routinely applied to a variety of real and hypothetical damage events. For example, in 2006 and 2007, NISAC used the model to estimate electric restoration sequences for six hypothetical hurricane tracks affecting eastern and Gulf Coast cities (New York, Washington, Miami, Tampa, Mobile, Houston). The model was used to identify key response options, such as FEMA pre-positioning of emergency electric generators, likely critical paths for emergency services, and long-term customer impacts due to extended electric outages. EPRAM provided in-depth reporting for electric restoration issues as needed for DHS response and recovery activities.

EPRAM Application to Cross-Border Electric Outage Event

Aggregate time-to-restore; includes EPE and CFE customers

Aggregate time-to-restore; includes EPE and CFE customers (Click to enlarge)

During March 2009, NISAC used EPRAM to estimate impacts resulting from a hypothetical cross-border electric outage event affecting El Paso, Texas, and Cd. Juarez, Mexico. Modeling results included:

  • 950 MW customer demand outaged in El Paso
  • 46 substations potentially disrupted in the United States
  • Restoration estimated at 25 hours+ including damage assessment
Partially-restored and outaged service areas in El Paso and Cd.Juarez

Partially-restored and outaged service areas in El Paso and Cd.Juarez (Click to enlarge)

Most significantly impacted utilities:

  • El Paso Electric EPE (over 60% of outaged demand)
  • Texas-New Mexico Power Co.
  • Comisión Federal de Electricidad CFE (35% of outaged demand)
  • 720,200 total population impacted: 478,700 in the United States and 241,500 in Mexico

Confidence in the Model

EPRAM has been continuously validated using a variety of real damage events. A series of post-event validations was completed for the 2004 through -07 hurricane seasons. Documented validations of model output have also been completed for a variety of historic events such as tornados, ice storms, wind storms, and earthquakes. In 2007, an industry audience at the National Hurricane Conference in New Orleans Model results formally evaluated EPRAM

Industry-standard data is applied to EPRAM’s input and output processing sequence
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Industry-standard data is applied to EPRAM’s input and output processing sequence. (Click to enlarge)

Industry Data Basis

Data for substations, generators, and electric component ratings are updated yearly (Source: Utility FERC 715 filings). Other data is extracted for transportation, emergency services, public health, population (day/night), and business locations (Source: HSIP Gold).

Documentation/References

  • National Infrastructure Simulation and Analysis Center EPRAM Model Methodology Overview, January 2006.
  • Session proceedings (April 10, 2007), industry presentation materials and comments, National Hurricane Conference, New Orleans, LA.
  • National Infrastructure Simulation and Analysis Center Miami Category 5 Hurricane Simulation (Florida Power & Light critique), September 2007.
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