Distribution Planning


Electrotek performs a variety of distribution system analysis and planning activities for utilities.  Typical services include complete planning studies, power factor correction, voltage regulation, calculation of reliability indices, and harmonics analysis. A typical planning study starts with the collection of both electrical system data and decision-making criteria from the client utility. After building a circuit model on the appropriate computer tool, we perform capacity studies to determine where the system needs to be reinforced. Reinforcement options are evaluated and compared using a value-based economic analysis. The models can be customized for the client's tools and data sources, and training is provided to the client for their use. 

We also supply solution engines that either end users or software vendors can incorporate into their packages to perform specialized tasks. Examples of specialized tasks include harmonics analysis, dispersed generation analysis, system dynamics and reliability analysis. While these solution engines can perform many conventional analyses, they are primarily designed to fill in the gaps of conventional distribution analysis packages. We supply stand-alone analysis applications for helping distribution planners study difficult application problems. These applications are characterized by an intuitive user-interface and they generally address a single problem.

Electrotek has developed new methodologies and supporting computer tools for evaluating expansion plans for utility electrical distribution systems. To perform a typical study, we work with the utility’s distribution engineers and planners to build computer models of the subject planning area. Capacity, reliability, and other analyses are performed through computer simulation for a predetermined planning horizon – typically 10-20 years. The costs of candidate expansion plans are estimated and the least cost expansion plan considering future operating costs is determined.

Our planning methodologies permit the evaluation of such diverse capacity alternatives as dispersed resources, demand-side management, and distribution automation as well as conventional substation and feeder additions. These methods differ from traditional planning methods based on the peak capacity of the system, which often result in excessive conservatism in adding new capacity. Instead, the methods assign costs to exceeding capacity and seek to minimize the costs.

Traditional planning methods often are inadequate for exposing the potential benefits of using DR for incremental capacity expansion. We take a multi-step approach that begins with pure economic screening and proceeds to detailed interconnections studies, which are mostly technical. A variety of power system analysis and economic investment analysis tools are utilized. The bulk of the engineering analysis is performed using a power flow tool.  The planning problem often requires modeling of a portion of the transmission system as well as the distribution system. Thus, the Distco Suite contains capabilities not found in traditional distribution system analysis tools.  In addition, we also use sophisticated electromagnetic transients programs for detailed simulations of machine dynamics and static power converter interfaces.

In a typical system capacity analysis, a “do-nothing” analysis serves as a base case and translates the following operational phenomena into utility operational costs. Focal areas include:

  • Voltage regulation
  • Substation and line capacity
  • Transformer thermal re-rating
  • Losses (substation and feeder)
  • Reliability (expected unserved energy)

The energy shortage in these categories is combined with other energy-dependent costs in the do-nothing scenario to indicate the importance and cost-effectiveness of an expansion project.  To evaluate alternative expansion plans, annual load flow simulations are run for several expansion alternatives. These simulations are the basis for determining the annual cost of losses, O&M, and energy shortage, for the length of the study period (i.e., for 10 years).  Electrotek then organizes the results into plans. For example, a plan representing a proposed new substation will contain the combined results of all related normal and contingency cases.  The model automatically sums or aggregates this data and creates a summary data set to be used in the costing model. 

A database of capital and O&M costs for distributed generation, storage, and demand side management technologies, as well as conventional feeder and substation equipment, is used to determine the investment costs of the alternative expansion plans.

Electrotek offers a three-day Distribution Planning with Distributed Generation Workshop that trains utility distribution planners and engineers in these planning techniques, placing particular emphasis on distributed generation technologies and the changing business and regulatory environment in the utility industry. This workshop covers a broad range of engineering and economic issues related to distributed generation. It presents basic distribution analysis techniques and then shows how they can be extended to support planning under the new industry environment. Both existing planning tools and advanced tools are utilized, and economic analysis and load forecasting fundamentals are presented to lay the groundwork for understanding the overall planning framework. The workshop covers advanced marginal costing and screening methods, culminating with the decision-making process.