A feeder in electrical distribution is a circuit that carries power from a substation to the area where customers need it. Think of it as the main highway in an electrical network: it moves large amounts of electricity at medium voltage (typically 5 to 35 kV) from a distribution substation outward toward neighborhoods, commercial areas, or industrial zones. No customers tap power directly from a feeder. Instead, transformers along the feeder step the voltage down to usable levels, and smaller circuits called distributors deliver it the final stretch to homes and businesses.
How a Feeder Fits Into the Distribution System
Electricity travels through a clear hierarchy before it reaches your outlet. Generation plants produce power at high voltage, transmission lines carry it across long distances, and substations step it down. From there, feeders take over. They form the medium-voltage backbone of the local distribution network, branching out from the substation along streets and corridors to cover a designated service area.
Feeders often curve and branch as they follow roads and utility corridors. Smaller branches called lateral taps split off the main trunk to reach pockets of customers that aren’t directly along the feeder’s path. These laterals are typically protected by fuses, reclosers, or automatic sectionalizers so that a problem on one branch doesn’t knock out the entire feeder.
Distribution transformers sit along the feeder at regular intervals. Each one converts the medium voltage down to the low voltage your appliances use, usually 120 or 240 volts in North America, or 230 volts in much of the rest of the world. From those transformers, a secondary (low-voltage) network branches off to individual customer connections through service drops.
Feeder vs. Distributor
The key difference is simple: a feeder operates at medium voltage and no consumer draws power directly from it. A distributor operates at low voltage and connects directly to customer meters. Feeders supply distributors, not the other way around. If a feeder is the highway, a distributor is the local road that ends at your driveway.
Because feeders carry higher voltages, they require heavier insulation, larger conductors, and more robust protective equipment. Distributors handle the final, low-voltage delivery and are sized for the relatively modest loads of individual homes or small commercial buildings.
Types of Feeder Configurations
Radial Feeders
A radial feeder is the simplest and most common layout. Power flows in one direction only, from the substation outward to the end of the line. It’s cheaper to build and easier to protect because fault current only flows one way. The tradeoff is reliability: if a section of the feeder fails, every customer downstream of the fault loses power until crews fix it. Radial feeders are standard in suburban and rural areas where the cost of more complex systems isn’t justified.
Radial feeders can vary widely in size. Some are short and heavily loaded, serving dense areas at voltages around 4 kV. Others stretch for miles through rural territory, lightly loaded and requiring multiple voltage regulators along the way to keep voltage from sagging at the far end. Longer feeders are more prone to voltage fluctuations and can be trickier to manage.
Ring Main Feeders
A ring main feeder forms a continuous loop. Power can reach any point on the ring from two directions, so if one section develops a fault, crews can isolate that section and restore supply through the other path. Every distributor connected to the ring effectively has two parallel supply routes.
This redundancy makes ring main systems significantly more reliable than radial ones. They also produce fewer voltage fluctuations because power flows from both sides of the loop, balancing the load. Ring main systems are common in urban centers and industrial parks where outages are especially costly. The downside is higher construction and equipment costs, since the loop requires more cable, more switchgear, and more sophisticated protection.
Parallel Feeders
In a parallel feeder arrangement, two or more feeders run side by side to serve the same load. This is used where a single feeder can’t handle the required current on its own, or where extra redundancy is needed. Splitting current across multiple conductors reduces resistance, improves efficiency, and minimizes uneven loading that can wear out components faster. Parallel feeders are most common in industrial facilities with heavy electrical demands.
How Feeders Are Protected
The most common fault on a distribution feeder is a single line-to-ground fault, often caused by a tree branch, animal contact, or equipment failure on one of the conductors. Protection systems need to detect these faults quickly and isolate them before they damage equipment or cascade into larger outages.
Modern substations use multifunction digital relays that monitor each feeder for overcurrent conditions. These relays contain both instantaneous elements (which trip immediately for severe faults close to the substation) and inverse-time elements (which allow brief overloads but trip if the overcurrent persists). The same relay typically monitors all three phases plus the ground path, catching both phase-to-phase and ground faults.
Reclosing relays add another layer of resilience. Many feeder faults are temporary. A tree branch touches a line, an arc forms, and then clears on its own once the branch falls away. A recloser automatically opens the circuit to clear the fault, waits a few seconds, then re-energizes the feeder. If the fault is gone, power is restored without a crew ever leaving the shop. If the fault persists, the recloser locks open and the section stays de-energized until crews arrive. Breaker failure protection also watches for situations where a circuit breaker is commanded to open but doesn’t, triggering backup breakers upstream to prevent damage.
Feeders and Rooftop Solar
Traditional feeders were designed for one-way power flow: substation to customer. Rooftop solar panels and other distributed energy sources have changed that. On a sunny afternoon, homes with solar panels may push excess electricity back onto the feeder, reversing the normal flow direction.
This bidirectional flow creates challenges. Voltage can rise unexpectedly on sections of the feeder receiving power from solar panels. Protection equipment calibrated for one-direction fault current may not respond correctly when current flows the other way. Utilities are addressing this with new switchgear that can detect and control bidirectional power flow using fast-acting semiconductor switches. These systems can connect or disconnect solar generation, battery storage, and loads independently, and can even island a section of the grid to keep customers powered during broader outages.
Some newer switchgear designs use a DC bus internally, allowing various generation sources (solar, wind, battery storage) to plug in through converters. An intelligent electronic device coordinates everything, deciding when to feed power to the grid, when to store it, and when to disconnect from the grid entirely for safety. If something goes wrong on the main grid, the system can isolate customers from the fault within a quarter of a power cycle and keep them supplied from local generation.
Voltage Levels and Feeder Classification
Feeders are broadly split into two categories based on voltage. Primary feeders operate above 1,000 volts AC, typically in the 5 to 35 kV range. These are the main arteries leaving the substation. Secondary feeders operate at 1,000 volts AC or below, carrying power the last stretch from distribution transformers to customer meters.
The U.S. National Electrical Code treats these two categories separately, with distinct rules for conductor sizing, overcurrent protection, and installation methods. The upcoming 2026 edition of the code further separates feeder requirements into dedicated articles for circuits above and below the 1,000-volt threshold, reflecting how different the engineering challenges are at each level.