Basic Principles of Electric Distribution Design

For a vast majority of the population, power is one of those things that you don’t notice unless it stops working. Often, power outages can be chalked up to intense weather, vegetation issues, or vehicle collisions, but sometimes high power demand (think heat waves or unexpected cold snaps when everyone bumps up the AC or heat) can overburden the grid and create failures. One of the goals of electric distribution design is to avoid those outages completely (or at least make them as rare as possible). 

Essentially, distribution design creates and builds electrical plants that manage and coordinate power flow based on electricity demand to keep the lights on and limit the risks of outages. 

Using software like AutoCAD, distribution design engineers draft power systems to bring electricity from distribution substations to homes. Designers have to calculate electricity usage and needs, prepare sketches, prescribe necessary equipment, estimate costs, update infrastructure, and more to make sure that power reaches customers and communities without jeopardizing the grid. 

Design Principles for Electrical Distribution Systems 

The process of lighting up a home or business is complex, and it has changed over the years. With new tech, new demands, and new regulations, designers have more to consider.

While certainly not exhaustive, these are some major concerns and principles that distribution designers and engineers keep in mind when designing new distribution systems: 

Load Balancing 

Load balancing ensures the even distribution of electricity across the electrical distribution system. Uneven loads create issues across the feeder—excess load in one area forces equipment to work harder, damaging assets and shortening their lifetime. Imbalances also waste energy with line losses across the system. 

From a reliability point of view, unbalanced loads increase the potential and likelihood of outages. Overloaded phases may trip protective devices more frequently and interrupt supply for customers. In worst-case scenarios, severe overbalance can create cascading failures across the system. 

Load balancing is becoming increasingly more difficult as DERs and EVs change peak patterns and loads throughout the day. Smart tech is starting to employ real-time load balancing to automatically redistribute power based on conditions. More and more engineers will need smart monitoring to provide intel on flow, voltage levels, and power across feeder phases to detect imbalances and redirect customers. 

Redundancy Planning

We engineer and conduct pole loading analysis for storms and in case of inclement weather, but even the best plans and systems need redundancy built in. Whether this is parallel lines, backup generators, or multiple transformers serving the same area, redundancy paths keep electricity flowing while repairs are made. 

Critical systems (such as those that serve hospitals or emergency services) need higher levels of redundancy than other systems. A tiered approach helps engineers prioritize feeders based on the level of impact in case of a failure. For example, an “N+2” redundancy, where N represents the number of components needed for normal operation plus the backup (+2), would denote a higher level of redundancy for an essential area. 

Of course, redundancy doesn’t come without a price tag. Backup components cost real dollars for equipment and maintenance. These costs do need to be weighed against the benefit of preventing outages. Utilities often use “customer minutes interrupted” to quantify the value of reliability and redundancy investments. 

Smart Tech Integration

Advanced technologies like smart switches and circuit breakers help avoid outages and reduce their impact by adjusting supply based on feeder reports. So when the electricity to one feeder goes out, another can jump in to keep power flowing.

With smarter technology, systems become more flexible, able to switch loads and flow from different pieces of equipment. Just as important is the speed at which systems can switch to backups—while a suburban area might be able to tolerate an hour or more in transition, hospitals need seamless transitions in just seconds. 

Smart tech is making redundancy more efficient and less costly over time. Automatic switches and reclosers reroute power without human intervention or oversight, and monitoring systems can predict failures ahead of time so engineers can focus on scheduled maintenance rather than emergency repairs. 

The Why Behind the Distribution Design 

Distribution design demands high attention to detail and an understanding of complex electric components. Because designers directly affect the flow of power, they have to be cognizant of the serious safety risks and concerns associated with electrical systems. 

Plus, the quality of the designs determines how reliable and efficient the grid is. Well-designed systems need to be flexible enough to meet a variety of needs for customers without overestimating the electricity demand. The better the design, the less unexpected maintenance required. 

Design Difficulties

Meeting Standards and Specs

Engineers have to minimize the costs of distribution while still ensuring standards are met. These standards are set by bodies like equipment manufacturers, standards organizations, and utilities.

Standards help ensure proper clearance and safe conditions for work, equipment doesn’t get damaged, and customers have access to the energy they need. (The American National Standard Institute, or ANSI, provides ranges for power distribution.) 

Because the distribution industry is an ever-changing environment, codes and regulations are required to change and adapt as well to keep people safe and the lights on.  

New Technologies 

As better tech options and practices for electricity and grid management emerge, legacy distribution systems need updating. 

Previously, only the loads on substation transformers and feeders were measured. Without more detailed monitoring and data on peak demands, distribution plants have been overdesigned, providing more energy than is needed. With more metering capabilities, utilities and their distribution designers can collect data on peak hours and demand. That way, they can tailor the energy flow based on what’s actually used and pad estimates based on risk assessments. 

As distributed energy resources (DERs) rise in popularity and commonality, they also create new challenges. Designs need to determine and account for the maximum capacity that DERs can add to a network without compromising reliability or performance. 

Geographic Differences 

Distribution plants in different areas will have to meet different demands. These are often categorized as urban, suburban, and rural based on what kind of load they’ll have to manage. 

Urban areas require greater loads, with more substations and bigger equipment. Rural areas tend to serve fewer people, meaning they can supply a smaller load, with more space between substations and smaller equipment to meet consumers’ needs. Semi-urban areas fall somewhere in the middle. 

Different load requirements, voltage fluctuations, and potential risks will affect the design process. 

Distribution Tools 

Great distribution designs should help minimize the need for constant maintenance, but some degree of upkeep is always necessary. Utilities need tools and software that help them manage their grid and ensure uninterrupted service. 

As equipment ages, tools need to help create replacement plans to avoid huge costs while still mitigating risks. When updating old distribution plants, having an overview of all equipment and assets currently in use with their specs, age, and performance helps inform decisions for replacements and updates.

As new distribution designs get built, power providers have to balance timing to make sure build-outs won’t create major consequences or outages. Good asset management tools give a broad view of different actions and their effects on the surrounding environment and provide cohesive workflows and processes for distribution projects. As assets age and technologies change, good software will be crucial to supporting utilities as they update and protect their grid.   

Thanks for reading! Katapult can be used to manage distribution equipment, create inventories, and build out maps for distribution design, and house asset records. We’re working on creating better tools to reduce the headaches and challenges of designing excellent distribution systems!