What is a feeder

Operating principle and classification

What is a feeder in the electric power industry? It is often confused with a distributor, because it also transfers energy from a generating station (or substation) to points of electricity consumption. However, the feeder does not perform intermediate control, so the current values ​​remain the same on both the sending and receiving sides.

Depending on operating conditions, feeders are divided into the following groups:

• Industrial;
• For use in agriculture;
• Household (lighting).

In the latter cases, the line is designed for a voltage of 220 V (for other types - 220 and 380 V).

The sequence of operation of the feeder is determined by its purpose. The feeder line is part of the electrical distribution network. The electrical circuit in a building that transfers energy from a transformer or other similar device to a distribution panel is shown in Figure 1. Different loads are connected to buses to supply different loads: power and/or lighting.

Distribution feeder conductors exit the circuit breaker (or substation circuit recloser) through underground cables called output cables. Thus, the feeder in electrical engineering is part of the energy distribution system from primary devices to secondary devices. As follows from Figure 1, after energy is transmitted through the line, it reaches the substation, where the network voltage can decrease, depending on the power and the number of consumers.

Where did the name come from

The very concept of “feeder” is a transcription of the English term “feeder”, which comes from the word “feed”, which has several meanings. The most famous of them is “to feed, feeding” but can also mean “feeding mechanism”. In the energy industry, this term refers to the supply line or input cable.

In fact, the concept of feeder in the electric power industry is used only colloquially, and it is absent in regulatory documents, so the question arises - what is a feeder in electrics?

Despite the complexity of the issue, electricians working at the substation understand the meaning of this term. It does not denote the type of device, but the functional parts of the circuit. Most often this is a 6-10 kV line that supplies transformers and connects them to an oil switch or disconnector.

This concept in energy is used in different, but similar situations:

• if at a substation the input switch (disconnector) is turned off emergencyly or scheduled and all transformers are left without power, then they say that the feeder line is turned off;
• if the connecting cable between the transformer and the switch is damaged, they also say “the feeder is damaged”;
• A feeder is a cable running from one of the output machines to the consumer.

In addition to cables and busbars, a feeder at a substation may include oil or air circuit breakers, disconnectors, measuring instruments, protection and automation devices. Switchgears of various types may consist of several outgoing lines.

This term is also applied to power lines connecting different substations, but primarily it is a network that supplies power, usually high voltage, to equipment. If the line does not go to the transformer, but to the distribution node, then the lines extending from this node are called branches.

Components

What is a feeder in electrical engineering? Since it is the main conductor, it supplies power to the main load center and then to the distributor (usually three-phase, four-wire). Next, the load enters the service network, to which direct consumers are already connected (see Figure 2).

Figure 2. Internal feeder line elements

Feeders in electrical engineering are designed based on the current-carrying capacity of the conductors, and their calculations are made based on known values ​​of the voltage drop and line duration (maximum - up to 12...15 km).

Not all conductors are included in the line. Those of them that are located between the service point and the devices designed to disconnect the consumer are service conductors. Special maintenance rules apply here since they do not have grounding devices or other protective devices (other than those provided on the primary side of the secondary transformer).

An electrician's feeder does not always represent any internal branching, since the branched circuit includes conductors between the overcurrent device protecting the circuit and the outlet (regardless of what current the fixture is rated for).

Practical use

Electricians at a substation use this term in the following cases:

1. Emergency shutdown of a high-voltage switch (oil or vacuum), which cuts off the power to the primary windings of all step-down transformers. When handing over a shift or describing the situation, electricians say that feeder protection No. has tripped...
2. Damage to the cable running from the feeder to the transformer. In this case, they say that there is a fault on the feeder line No....

In these situations, the feeder is part of the substation input circuit.

A feeder or feeder line is also called a line going from one substation to the next, as well as a distribution node. Therefore, the terms “feeder”, “power line” and “main” are interchangeable.

This term is used not only by practicing electricians. It is also used by designers of power supply systems. In this case, the feeder is a cable or overhead line connecting two switchgears or switchgear and a step-down transformer or other device.

And yet, what is a feeder in electrical engineering ? This is the line running from one switchgear to the next on the circuit or from the disconnector to the consumer.

It can be overhead, cable or system, but in order to be called a feeder, a line must carry power from one apparatus to another. Circuits that serve to connect transformers or bus sections in parallel operation are not called feeder lines.

An example is the power supply system of wired electric transport. These are high-power consumers connected to their own step-down substation.

In this case, the term "feeder" is applied to the cable or overhead line connecting the transformer and the overhead wires or, in the subway, buses. In addition to cables, connecting circuits include switches, disconnectors, protective relays and other signaling equipment.

Line diagram

It will be required whenever a partial redesign of internal and external power connections is made. In this case, you need to know the values ​​of the following parameters:

1. Total design load.
2. The maximum value of the demand coefficient.
3. Current limits.
4. Maximum length of external conductors.
5. Characteristics of overload protection devices.

A typical electrical system may contain several types of feeders. In accordance with this, lines are designed for different types of loads - continuous, periodic, combined, external. The latter are taken into account when designing the energy supply system for individual buildings. In particularly complex cases, feeders can be composite, representing more than one voltage system, or incorporating direct current lines.

The electrical diagram of one of the sections is shown in Figure 3.

Figure 3. Electrical diagram of one of the indoor feeder blocks

Primary feeder lines are typical for power plants. The distribution node can be internal or external. Although the rules for electrical overcurrent protection vary depending on the load supplied, the limit is usually set at the end of the branch.

How are feeders used in electricity?

Power engineers began to use the word “feeder” in their work quite a long time ago. This happened shortly after the start of electricity supply to England and the USA. The electrical loss indicators characteristic of a particular system will depend on the use of equipment. In turn, this determines the efficiency of a particular network.

The usual voltage of operating networks is 6-10 kW. Calculations for electricity losses are performed literally every month. Depending on the accuracy of these calculations, certain tariffs are set for the use of electrical energy. Loading 10 kW feeders affects the results of some calculations and design activities.

Power transmission

Application for electric vehicles

Protection schemes using switches are used to ensure the safest operation. The parameters that the network has in a particular case depend on the operating voltage. An example is traction substations, where the standard voltage is 3.3 kW. Here, each switch is equipped with both primary and additional protection in case of outages.

Polarized switches with maximum operating speed act as switches. The overcurrent protection function in this case is transferred to the circuits, which are also responsible for the general control of the system. Standard current protection is provided by the same part.

In case of short circuits, the above types of protection become the main ones. Backup protection is needed to enhance user experience

To organize proper work, it is important to correctly configure current schemes. Even at maximum loads, accidental operation must be prevented

The safety factor is set within 1.15.

Interesting! Feeders in a traction network are the most complex devices. The load occurs gradually, and more than once in each of the elements. There can be many such loading modes depending on how many elements are moving along the road. For the movement of electric vehicles, the accuracy of all characteristics is important.

Wiring

For this network, thin wires are used, which under normal conditions are not capable of withstanding significant loads. For example, even a current of 2 kA is enough to burn out a device in a split second. Only a fast-acting protection system with a short shutdown time ensures normal operation under these conditions.

Different wires and protection

Standard protection is installed in two stages. It includes accelerated current cut-off together with teleblocking. Installed at traction substations with a power of up to 25 kW, such solutions are made in the form of separate devices. The operation of the system itself deserves a separate discussion.

Feeder line - general view

To identify specific sections of circuits, the feeder structuring system remains quite convenient. But in regulatory documents there is no precise regulation of the term, and therefore, in practice, difficulties and misunderstandings are possible even between masters. Because of this, the likelihood of emergencies and accidents increases. It is better to rely on the terminology developed for regulatory documents. It is always easy to find, if not the same values, then with approximately the same decoding.

How to identify a feeder line

If there are feeders powered from different voltage systems, each ungrounded conductor must be installed in a phase or line along its entire length: from the connection point to the splice point. Identification of ungrounded ac system conductors may be accomplished by color coding, tape marking, or other approved means. Red color is allowed to be used for an ungrounded conductor of positive polarity, and black color for a conductor of negative polarity.

With the exception of high power systems and isolated power systems, the color orange is used to identify ungrounded AC conductors. It demarcates the upper part of the four-wire delta-connected system, where the midpoint of the single-phase winding is grounded, from the rest of the network. If there is a high voltage system (more than 220 V) in the same premises, then brown, orange and yellow colors should be used to mark ordinary feeder conductors (see Figure 4). Marking tapes or other means of identifying the feeder are also used to distinguish between areas of different voltages.

Figure 4. Marking of feeder conductors with different polarities and permissible heating temperatures

Circuits to all devices that require power are started from fuses or circuit breakers. Feeder circuits use thicker cables that run from the main entrance panel to smaller distribution panels that act as load centers. These panels are located in remote parts of the house or in outbuildings; they are also used to redistribute energy, for example, in garages or parking lots.

How the feeder line is displayed on the diagram

As an example, we can consider part of the circuit of a high-voltage substation, consisting of a 154/6 kV transformer T1 and step-down transformer substations TP1-TP3, consisting of bus sections and 6/0.4 kV transformers not indicated on the diagram. This will help you understand what a feeder is in electrical engineering.

In this diagram, the feeder is all the circuits connected to cell F1. These are sections of the power supply diagram designated by the letters “A” and “B”.

It is also allowed to consider only the circuits feeding substations TP1-TP3 as feeders. In the diagram, this section is designated “B” and is the F1 feeder network.

If it is necessary to turn off a given section, then the corresponding switch in the cell is turned off. For example, to turn off feeder “B” it is necessary to turn off the switch in cell F1. If they say that the feeder is damaged, then this means an accident on the entire section “B”.

Using this term allows you to indicate a section of the circuit, but does not indicate the location of the damage. This could be one of the cable lines, a disconnector or switch located on the same line.

In order to avoid confusion, the concept of “feeder” is used only in conversations, and in documents alphanumeric markings of electrical circuit elements are used.

Feeder for electricians

Substation workers, like representatives of many other professions, have their own “language” that is poorly understood by mere mortals. In order for these expressions to be understandable to ordinary people, they need to be deciphered:

1. Feeder. Its circuit can contain a variety of devices - oil switches, disconnectors, cables, overhead lines, control and automation systems.
2. The third feeder switched off or an emergency shutdown of F-3 occurred. This expression is used when there is an emergency network shutdown due to the activation of protection systems.
3. The third feeder is damaged. The phrase is used when protection is triggered due to damage to the line or breakers.
4. Fault in the feeder network or in the feeder network. The expression is applied after specifying the location of the accident and is supplemented by an indication of the faulty element.
5. The feeder has switched off. This means that the step-down transformer and the consumers connected to it were left without power. Some industries have the ability to switch to other power supply schemes, but for residential buildings this option is usually not available.
6. Your feeder is damaged. This is what electricians tell owners of private houses or residents of apartment buildings. Most often, this means that the network is damaged in the area from the power line pole to the input circuit breaker or switch. This could be a broken cable, oxidized terminals or connection point on a pole or in a water shield.

The concept of “feeder” and other related definitions are convenient for indicating a specific part of the network. The disadvantage of this term is that it indicates several elements of the circuit at once, united by a common function.

This may lead to disagreements in the understanding of the causes and location of the accident by operational and repair personnel. Such misunderstanding is dangerous for workers involved in troubleshooting, therefore, when solving practical problems, it is more advisable to use official terminology, in which the term “feeder” is absent.

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• How to plan an electrical wiring diagram
• Why is PUNP wire prohibited for use?
• Purpose of Phase and Zero

How to determine the load on the feeder

In new houses, mainly three-phase lines are laid, designed for a voltage of 220-240 V AC. That being said, all the circuits in the house that run from the main entry panel or from other small panels to various points of use are branch circuits using only two main buses.

Fuses or breakers are designed for a current load of 15 or 25 A.

The 15-amp circuits go to ceiling lights and wall outlets in rooms where less power-hungry appliances are installed, while the 20-amp circuits go to outlets in the kitchen or dining room where more powerful appliances are used.

It is estimated that a 15 amp circuit can handle a total of 1800 watts, while a 20 amp circuit can handle up to 2400 watts. These limits are set for full load circuits, but in practice the power is limited to 1440 W and 1920 W respectively.

To determine the load on the circuit, the individual power for all connected consumers is summed up. When calculating the load in each branch circuit, motor-driven devices, which consume more current at startup, are taken into account.

Types of feeder lines

Requirements for calculating loads on branches, services and feeders are differentiated in relation to the following categories of consumers:

• Electrical appliances;
• General purpose loads;
• Individual;
• Multi-wire.

The loads of general lighting and branched circuits of small devices are calculated in the same way. Under the standard load calculation method, when there are four or more customers assigned to a site, it is acceptable to apply a demand factor of 75%. When using the additional method, the demand factor of 100% is applied only to stationary consumers. The passport table includes all devices that are constantly connected or located in a specific circuit.

The external structure of a feeder designed for a voltage of 380 V is shown in Figure 5, and the general view of the feeder distribution board is shown in Figure 6.

Figure 5. General view of the high voltage feeder line

Figure 6. General view of the distribution board for the feeder