Trystan Casey
In electrical engineering, a feeder is a dedicated line of cables that carry electricity from a power station or substation to the end user, usually through an intermediate tapping point. Feeders are a crucial component in the distribution of electricity, connecting the sources of electricity (power stations and substations) with the end user (homes and businesses). They are also important in public transportation, ensuring connectivity between high-capacity routes and more localized departure and destination points.
Characteristics and Values of Electrical Feeders
| Characteristics | Values |
|---|---|
| Definition | All circuit conductors between the service equipment, the source of a separately derived system, or other power supply sources and the final branch-circuit overcurrent device |
| Function | To deliver electricity within a house or building |
| Connection | Connects the source of power, such as a power station or substation, to the end user |
| Safety | Provides a safe means for electricity distribution |
| Reliability | Ensures reliability of electricity supply |
| Distribution | Distributes electricity within a given area |
| Components | Circuit breakers, transformers, distribution points, and other related components |
| Type | Feeder lines can be either underground or overhead depending on the type and local regulations |
| Identification | Standard feeder identification methods allow qualified persons to quickly identify the phase and voltage of feeder conductors |
| Use Cases | Commonly used in commercial projects with multiple distribution points and in public transportation systems |
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What You'll Learn
Feeder identification methods
In power engineering, a feeder is a type of electrical line or wire that carries power from a main distribution point, such as a substation, to smaller distribution points or end users. Feeders are an essential component of electrical systems as they ensure the distribution of electricity to all areas that need it.
Colour-Coding
Feeders are often identified by colour-coding, which helps distinguish different feeder voltages. For example, the NEC mandates the use of the colour orange to identify the high-leg of a 4-wire delta-connected system. If a high-leg system is present on the same premises with a 480-volt system, the common practice of identifying 480-volt feeder conductors using the colours brown, orange, and yellow may need adjustment.
Marking Tape and Tagging
Marking tape, tagging, or other approved means of feeder identification may be required to distinguish the different feeder voltages. This method is especially useful when dealing with ungrounded conductors supplied from a DC system operating at more than 50 volts. Each ungrounded conductor must be identified by polarity at all termination, connection, and splice points.
Continuous Outer Finish or Stripe
Where the polarity of a DC system does not serve as the connection point for the grounded conductor, each ungrounded conductor can be identified by a continuous outer finish or stripe in a specific colour. For example, a positive ungrounded conductor may have a red outer finish or stripe, while a negative ungrounded conductor may have a black outer finish or stripe.
Imprinted Signs or Words
Another identification method for ungrounded conductors is to imprint signs or words on the insulation of the conductor. For instance, a positive ungrounded conductor may have plus signs (+) or the word "POSITIVE" or "POS" imprinted on its insulation.
Documentation and Posting
Using a standard feeder identification method throughout the premises wiring system is essential. This allows qualified persons to quickly identify the phase and voltage of the feeder conductors at all termination or splice points after installation. The feeder identification method used should be posted at each feeder panel board or documented and readily available to those servicing the electrical system.
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Feeder conductors
To understand feeder conductors, it's important to clarify what they are not. Conductors that connect the utility service point to the service disconnecting means are service conductors, governed by specific rules due to their lack of short-circuit protection. Similarly, branch circuits are not feeders; they are defined as circuit conductors connecting the final overcurrent device to the outlets.
The identification of feeder conductors is important for safety and maintenance. A standard feeder identification method, such as colour-coding or tagging, enables qualified personnel to swiftly identify the phase and voltage of feeder conductors after installation. This simplifies troubleshooting and ensures compliance with electrical safety standards.
Prior to installing feeder conductors, a feeder diagram may be required. This diagram includes critical details such as the calculated load on the feeder, demand factors, the size and type of feeder conductors, and the rating of the feeder overcurrent protective devices. Accurate load calculations are vital for safety, taking into account factors like demand factors and load types. Feeder conductors are sized based on the load they carry, with minimum size requirements outlined in electrical codes like NEC Article 220.
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Feeder vs branch circuit
A feeder is a circuit conductor that connects the power supply source to the final branch-circuit overcurrent device. It is a larger conduit that runs between pieces of switchgear, panels, and larger loads, such as HVAC units and large motors. Feeder circuits may also be referred to as power distribution circuits.
A branch circuit, on the other hand, is the utility circuit that starts from the load and ends at the first short circuit protection, also known as the Branch Circuit Protection Device (BCPD) or the final overcurrent device. It is a smaller conduit and wire, including conduit that is 1 inch and smaller, and wire #6 and smaller.
The National Electrical Code (NEC) definitions clarify that while feeders are often referred to as "motor feeders", they are, in fact, usually "motor branch circuit conductors". This is because, according to the NEC, if the motor disconnect has OCP, then it is a feeder, but if it doesn't, it is a branch circuit.
The distinction between the two is important for machine builders, especially those exporting to North America, as it determines the selection of components for their equipment. For example, the use of miniature circuit breakers in accordance with UL 1077 instead of branch circuit protective devices may result in the machine not being approved for export to North America.
Furthermore, the cost difference between the two is significant, with branch circuits being relatively inexpensive, while feeders can cost up to hundreds of dollars per foot.
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Feeder lines in public transport
In the context of electrical engineering, a feeder is a type of transmission line that transmits power from a generating station or substation to distribution points.
Now, onto the concept of feeder lines in public transport. Feeder lines are peripheral or branch routes in a public transportation network that connect smaller or more remote nodes to routes or branches carrying heavier traffic. This concept is particularly important in US air travel and rail transport, where feeder lines ensure connectivity between high-capacity routes and more localized departure and destination points.
In urban transit planning, bus routes often act as feeder lines, collecting passengers from various neighbourhoods and transporting them to major transit hubs like subway systems or light rail. This hierarchical network structure facilitates seamless and efficient travel across a region, allowing passengers to transition smoothly from local to long-distance travel segments.
To ensure the efficiency of feeder lines in public transport, it is crucial to coordinate their schedules with collector public transit lines. This coordination can reduce passenger travel times and enhance the overall travel experience. For instance, in New Zealand, the most common form of public transport is fixed-schedule services, which offer pulse, timed, and frequent connections between feeder and collector lines. Pulse connections involve multiple routes coordinating their schedules to arrive at a station at regular intervals, enabling passengers to transfer between routes conveniently. Timed connections involve a feeder service arriving before a connecting service, with a brief waiting period in between. Frequent connections occur when two high-frequency routes intersect, allowing passengers to transfer with minimal waiting times.
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Feeder lines vs transmission lines
In the context of electrical power systems, a feeder is a power line that delivers electricity within a localized area, typically operating at low to medium voltage levels. It carries electricity from a substation to distribution transformers, which are usually located near the end-users, such as homes and businesses. Feeder lines are found in both urban and rural areas and ensure connectivity between high-capacity routes and more localized departure and destination points.
On the other hand, transmission lines are high-voltage power lines that serve to carry electricity over long distances, connecting power plants to substations. They are often found in less populated areas and are crucial for transmitting electricity efficiently across regions.
One key distinction between the two is their voltage level. Feeder lines typically operate at lower voltage levels, usually between 1 kV and 33 kV, while transmission lines operate at high to very high voltage levels. This difference in voltage levels reflects the distinct purposes of the two types of power lines.
The length of feeder and transmission lines also varies significantly. Feeder lines are generally shorter, distributing power within localized areas. In contrast, transmission lines are designed for long-distance power transmission, spanning much greater distances than feeder lines.
Additionally, feeder lines are commonly associated with public transportation systems, particularly in US air travel and rail transport. They facilitate seamless travel by connecting local departure points to long-distance routes, allowing passengers to transition easily between different segments of their journey.
In summary, feeder lines and transmission lines play complementary roles in the electrical power system. Feeder lines focus on localized power distribution, operating at lower voltage levels and shorter lengths, while transmission lines excel at long-distance power transmission, utilizing high-voltage capabilities to efficiently transport electricity across regions. Both are essential for ensuring a reliable and robust electrical power network.
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Frequently asked questions
A feeder is a dedicated line of cables that carry electricity from a power station or substation to the end user. This is usually done through an intermediate tapping point.
Feeders distribute power within a localized area. They are key components in managing the distribution of electricity.
The feeder system includes circuit breakers, transformers, and other related components that help regulate and distribute electricity within a given area.
A feeder distributes power over short distances, typically with low to medium voltage. A transmission line carries electricity over long distances, with high to very high voltage.
