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Electric distribution system planning fundamentals

What is electric distribution system planning?

Electric distribution system planning is a forecast, analysis and solution planning cycle for maintenance and development of the utility grid. The goal is to maintain safe, reliable, and affordable service while also efficiently operating the existing electrical facilities that make up the grid. Future electric distribution planning should incorporate smart grid modernization efforts such as demand response, advanced metering infrastructure, grid automation and distributed energy resources while also balancing electric power quality, supply and cost.

The traditional focus of electric distribution planning is safety, reliability, load forecasting, risk mitigation and reasonable cost.

Electric distribution system planning software

Power engineering software is designed to help address the complex and emerging challenges of the electrical engineers that support power network planning and operation. Eaton's CYME power engineering software capabilities support any type of power system simulation, including the creation of planning scenarios and case studies that accurately and efficiently assess and substantiate the impact of modifications and reconfigurations to any power network.

Eaton’s CYME software interface includes the analysis functions used by power engineers as a seamless suite of applications. CYME software provides powerful modeling capabilities that support the detailed modeling of any distribution, industrial or transmission network of any scale or complexity. Creating balanced and unbalanced networks, secondary grids, substations, nested networks, whether radial or meshed, three-, two- or single phased, is fully supported and can represented schematically or geographically. To bring the network representation even closer to reality, the modeling capabilities are supported by extensive industry-standard equipment and control libraries that can be enhanced by the user. Discover how CYME software modules can support the electric distribution system planning cycle.

Quick links to electric distribution system planning fundamentals: Planning cycle | Risk mitigation | Safety | Reliability | DER
 

What is the electric distribution system planning cycle?

Electric utilities plan and make investment decisions based on current and future customer load and the impact of distributed generation resources.

Forecast cycle

  • Gather real-time data
  • Build load profiles
  • Assign load profiles
  • Create forecast scenarios
  • Publish forecast scenarios
  • Evaluate forecast scenarios
  • Allocate forecast
Analysis cycle
  • Capacity analysis
  • Protection analysis
  • Reliability analysis
  • Automation analysis
  • Contingency analysis
  • Analyze risk
Solution cycle
  • Create mitigation
  • Build mitigation portfolios
  • Evaluate mitigation portfolios
  • Approve mitigation
  • Update system model
 

What can be learned from electric distribution load forecast planning?

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During the electric distribution load forecasting process, the electric utility will track peak loads, publish an annual long-range forecast, evaluate each feeder for annual growth (new loads). Feeder load aggregation may require expansion of existing or new substations.

An advanced project manager software module may be used for as-planned system configuration, so the planning engineer can manage time-based projects and assess multiple scenarios in a flexible framework.

steady-state analysis with load profiles software module allow for time series load flow analysis based on modeled profiles created from available data sources.

load allocation and estimation software module for traditional peak planning enables the electric distribution system planning engineer to develop an accurate load model by allocating feeder demands across the network based on transformer connected capacity, consumption and billing data or existing calculated load data.

 

What can be learned from electric distribution risk mitigation planning?

Electric utility risk mitigation distribution planning determines N-0 and N-1 risks based on peak demand and available capacity in order to develop solutions such as demand management, new or reconductoring existing feeders, new or increased substation capacity.

contingency assessment and restoration software module helps the electric distribution system planning engineer to prepare for the inevitable while managing day-to-day operations. Engineers can study what-if situations of a single outage on a radial system to establish an optimal switching plan.

load flow contingency (N-p) software module assesses the future and manages day-to-day operations enabling the planning engineer to study unlimited what-if scenarios of up to N-p contingencies to establish an optimal network operation in order to manage and assess expansion or modifications.

network configuration optimization software module can help the planning engineer reconfigure radial networks to an optimal topology through various switching configurations.

load relief DER optimization software module provides for highly efficient evaluation of load relief projects. The module determines the best sites and sizes for energy storage systems and dispatchable generation.

An optimal voltage regulator placement software module helps the engineer to find the optimal location for the voltage regulator, set the tap position and determine the amount of regulators needed to achieve the desired voltage regulation.

techno-economic analysis software module can help to assure an optimal return on utility investments. Whether planning maintenance, replacements, improvements or expansions to a power system, the engineer can analyze the impacts of modifications made and the cost and gains they entail over the years.

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Eaton's CYMDIST software module includes these functions:

Optimize circuit load balancing of the network by rephasing of lateral circuits; optimize based on objective to minimize kW losses, or balance the current, the load, or the voltage; recommended rephasing based on selected objective and criteria; and circuit conditions presented before and after rephasing for neutral current, total losses (KW) average KVA and unbalanced factors.

Optimal capacitor placement and sizing to improve power factor or voltage and to evaluate switched versus fixed capacitor impact based on peak and minimum load levels.

 

What can be learned from electric distribution safety planning?

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Distribution safety planning entails designing, operating and maintaining an electric distribution system that does not risk safety to people.

short circuit analysis software module can help the electric distribution system planning engineer to ensure system safety by calculating fault currents, analyzing contributions from multiple sources for a fault, assess the effects of various short-circuits on system voltage profile, select interrupting equipment, establish protective settings and facilitate fault current assessment on system components.

protective device analysis software module can facilitate the planning engineer to verify and enhance power system protection. This functionality includes overcurrent protection, fault analysis and sequence of operation.

An arc flash hazard software module can enhance safety efforts throughout the distribution system by generating study benchmarks for curves and points and analyzing minimum faults and sequence of operation.

The advanced fault locator software module provides engineers with a rigorous method to calculate and visualize the possible fault locations on a detailed network model.

 

What can be learned from electric distribution reliability planning?

Electric distribution reliability planning goals are to provide the power the customer needs at a reasonable cost, maintain power quality and reduce SAIFI and SAIDI performance indices:

  • SAIFI = System Average Interruption Frequency Index
  • SAIDI = System Average Interruption Duration Index

reliability analysis asset management software module can help the planning engineer to assess the historic performance of utility assets and predict future reliability of the electricity delivered to the end-customer.

An optimal recloser placement software module helps achieve a better level of reliability by placing reclosers at optimal locations. System reliability can be improved by minimizing outages through the addition of protective devices. 

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How is electric distribution reliability planning affected by distributed energy resources (DERs)?

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Electric distribution system planning should include the effect DERs have on the grid such as available capacity, variability and risk mitigation.

An integration capacity analysis software module helps the electric distribution system planning engineer to determine the maximum allowable capacity that can be interconnected at any point of the network without compromising reliability and power quality.

The EPRI DRIVE module combines the engineering effort of the EPRI DRIVE engine with the Eaton CYME detailed distribution system model to analyze hosting capacity.

The steady-state analysis with load profiles software module conducts time series load flow analysis based on modeled profiles created from available data sources enabling the engineer to exploit new data sources and improve use of existing data while accurately modeling loading conditions at any moment in time.

The time series long-term dynamics load flow analysis software module is based on expanded modeling of equipment to simulate variable phenomena in the seconds to minutes range. This modeling includes the intermittency of wind and cloud-over periods effect on the output of wind energy systems and photovoltaic (PV) generation and also allows the study of reserve capability of battery energy storage devices on the network.

Time series analysis based on expanded equipment modeling to simulate electromechanical transients. This software module utilizes the simultaneous implicit trapezoidal integration solution technique for network, machine and controller equations. The electric distribution system planning engineer can test the step response of controllers and user-defined models to verify ability to withstand abnormal events (e.g. faults, switching, load shedding). Initial voltage profile of the balanced and unbalanced network are computed with balanced power flow algorithms namely the Newton Raphson or Fast Decoupled.

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