Distribution Systems 221

AC

Alternating current. Electricity that reverses direction at regularly recurring intervals of time. AC is supplied to homes and businesses by electrical distribution systems.

Alternating current

AC. Electricity that reverses direction at regularly recurring intervals of time. Alternating current is supplied to homes and businesses by electrical distribution systems.

Aluminum

A highly conductive, lightweight, silvery metal. Aluminum is often used in busbars and transmission lines.

Amperage

A measurement of the amount of current flowing in a circuit. Amperage is measured in amperes (A).

Amperes

A. A unit of measurement that indicates the amount of current flowing in a circuit. Amperes are also called amps.

Arc flash

An electrical explosion that can occur when an electric arc creates a short circuit between exposed conductors. Arc flash can produce enough heat, light, and explosive force to cause permanent injury or death.

Arc-rated

Safety equipment designed to protect against arc flash. Arc-rated PPE often includes an arc flash suit and arc flash hood.

Armature

The component of a generator in which current is induced. The armature usually consists of a series of coils or groups of conductors surrounding a core of iron.

Armature windings

A conducting coil that is wound around the armature and in which voltage is induced. Armature windings move through the magnetic field, inducing voltage in the windings.

Branch circuits

The section of a distribution system that carries electricity from the final overcurrent devices to the load. Branch circuits usually have lower voltages than feeder circuits.

Buckets

A modular unit that contains all the devices necessary to control a single motor. Buckets in a motor control center usually contain overcurrent devices, motor starters, contactors, and other motor control components.

Busbars

A solid strip of copper or aluminum that serves as a conductor for high-energy electrical systems. Busbars can carry more electricity than wires or cables and are housed in busways.

Busways

A protective enclosure containing one or more busbars. Busways may have built-in plugs or movable tap-off boxes to connect branch circuits to loads.

Circuit breakers

A reusable safety device that opens a circuit when it detects excess current. Circuit breakers can be reset after activating.

Conductor

A material or element that allows free movement of electrons and therefore allows easy flow of electricity. Conductors are used to create wires, cables, and busbars.

Contactors

A relay used to safely control a high-energy circuit. Contactors are also known as power relays.

Control circuit

A circuit that uses control devices to open and close an output circuit. Control circuits usually carry lower voltages than power circuits.

Control relays

A relay that opens or closes a circuit in response to electrical signals from other devices. Control relays are used to control manufacturing processes automatically or remotely.

Copper

A reddish metal that is very ductile, thermally and electrically conductive, and corrosion resistant. Copper is often used to make electrical wires and busbars.

Copper loss

A decrease in energy caused by the resistance that current encounters when flowing through a conductor. Copper loss can be reduced in long-distance transmission lines by using high-voltage AC.

Core

A magnetic component made of laminated iron or steel. The core of a transformer directs lines of magnetic flux from the primary winding to the secondary winding.

Cycle

The process of AC going from zero to its peak positive value, back to zero, then to its peak negative value, and back to zero. One complete AC cycle equals 360 electrical degrees.

Delta

Δ. A connection of three conductors that form a triangular series circuit. Delta connections often do not require grounding.

Delta/delta

A three-phase transformer with delta connections for both the primary and secondary winding. Delta/delta transformers are used in manufacturing facilities with certain types of three-phase motor loads.

Delta/wye

A three-phase transformer with a delta primary winding and a wye secondary winding. Delta/wye transformers are often used to step down voltage for applications that require both single- and three-phase voltages.

Direct current

DC. Electricity that travels in one direction. Direct current is less commonly used than alternating current.

Disconnect switches

A control device used to separate an electrical circuit from its supply of electrical energy. The disconnect switch should be used to de-energize a circuit before beginning maintenance or repair work.

Dissipate

To spread, separate, and disappear. Heat dissipates more efficiently in busbars than in wires or cables.

Distribution substations

A facility located very close to the end users that contains multiple step-down transformers. Distribution substations reduce voltage closer to the lower levels that end users require.

Distribution systems

A group of electrical components that provide electricity from generating stations to specific end users. Distribution systems include components such as transformers, transmission lines, and substations.

Downtime

A period of time during which a machine or system is not operating. Downtime due to unscheduled repairs or maintenance can have a negative impact on overall production efficiency.

Electric arcs

The area in which electricity jumps from one conductor to another. Electric arcs produce heat and light.

Electric motors

A device that converts electricity into mechanical energy or motion. Electric motors operate on the principle of magnetic induction.

Electrical fault

Any condition that causes an abnormal flow of current in a circuit. Common types of electrical faults include open circuit faults and short circuit faults.

Electromagnets

A magnet that gains an attractive force only when current passes through it. An electromagnet is typically formed by wrapping several windings of wire around an iron core.

Enclosure

The metal frame or case of an electrical device such as a transformer or a motor. The enclosure protects the wiring inside the device.

End users

The final customer for whom a product or service is intended. End users of electricity include people in homes, businesses, and manufacturing facilities.

Feeder circuits

The section of a distribution system that carries electricity from sources outside a building to indoor switchgear and overcurrent devices. Feeder circuits usually have higher voltages than branch circuits.

Frequency

The number of complete AC cycles that occur in one second. Frequency is measured in hertz (Hz).

Fuses

A single-use safety device that opens a circuit when it detects excess current. Fuses must be replaced after activating.

Generating stations

A facility that houses multiple large, linked AC generators. Generating stations produce large amounts of electricity for distribution systems.

Generators

A device that converts mechanical energy into electrical energy. Generators operate on the principle of magnetic induction.

ground faults

A short circuit fault that creates an unintended path to the ground. Ground faults put employees at high risk of electric shock.

Grounding

A means of providing a safe path for electricity in case it strays from its intended path. Grounding directs current to the earth or another safe destination.

Hertz

Hz. A unit of measurement that indicates the frequency of alternating current. One hertz is equal to one cycle per second.

Hydroelectric power

The electrical energy produced by the movement of flowing water against turbines. Hydroelectric power is a form of renewable energy.

Industrial Internet of Things

IIoT. A network of physical devices used in manufacturing containing embedded computing systems that allow them to send and receive data. The Industrial Internet of Things allows devices to exchange data and automate processes without any human intervention.

Insulation

A non-conductive material used to protect electrical conductors. Insulation may be made of rubber, plastic, or ceramic.

Insulators

A material that is non-conductive and prevents the flow of electricity. Common insulators include plastic, glass, and rubber.

Interconnected system

A distribution system with multiple generating stations connected to end users in parallel. Interconnected systems, also known as network systems, are very reliable because they have redundant components.

Isolate

To separate a circuit or component from a source of electricity. Isolation protects one part of an electrical system from damage due to faults in another part of the system.

kilovolt

kV. A unit of measurement that indicates the amount of electrical force or pressure in a circuit. One kilovolt is equal to 1,000 volts.

Laminated

Consisting of thin sheets that are sealed together in multiple layers. Laminated metals are used in transformer cores because they reduce losses.

Line voltage

The voltage measured between any two phase conductors in a three-phase system. Line voltage is 1.732 times greater than phase voltage in a wye connection but equal to phase voltage in a delta connection.

Loads

A component in a circuit that converts electricity into light, heat, or mechanical motion. Examples of loads include light bulbs, appliances, and machines.

Loop system

A distribution system that provides a circular path from generating stations to end users. Loop systems are more reliable than radial systems because electricity can be supplied from two directions.

Magnetic field

The area in and around a magnet in which a magnetic force exists. Magnetic fields exhibit the powers of attraction and repulsion.

Magnetic flux

The force that surrounds a magnet and exhibits the powers of attraction and repulsion. Magnetic flux is described as imaginary lines of force that exit the magnet's north pole and return to its south pole.

magnetic induction

The use of magnets to cause voltage in a conductor. Magnetic induction occurs whenever a conductor passes through magnetic lines of flux.

MCC

Motor control center. A freestanding assembly of motor control devices that can control many motors from a central location. MCCs consist of several modular units called buckets.

Mechanical energy

Energy transmitted through physical interaction and motion. Mechanical energy can be converted to electrical energy by a generator.

Modular

Consisting of interchangeable and discrete parts. Modular assemblies allow for easier customization, repair, and replacement of individual parts.

Motor control

Any device used to start, stop, or change the speed, torque, or direction of a motor. Motor controls are essential for operating manufacturing equipment such as conveyor belts and industrial robots.

Motor control center

MCC. A freestanding assembly of motor control devices that can control many motors from a central location. Motor control centers consist of several modular units called buckets.

Motor starters

A device used to turn a motor on and off. A basic motor starter consists of a contactor combined with an overload relay.

Mutual induction

The process of one coil inducing a voltage in another coil that is not electrically connected. Mutual induction is used to transfer current between circuits in transformers.

Network system

A distribution system with multiple generating stations connected to end users in parallel. Network systems, also known as interconnected systems, are very reliable because they have redundant components.

neutral conductor

A conductor in a three-phase system that completes a circuit by connecting back to the source. The neutral conductor in a wye connection is attached to the center point of the wye.

Nuclear fission

A nuclear reaction that releases energy when the nucleus of one particle splits spontaneously or collides with another particle. Nuclear fission can be used to create steam and generate electricity.

Nuclear power

The electrical energy produced by the movement of steam heated up by nuclear fission reactions. Nuclear power plants use the steam to move turbines connected to generators.

Out-of-phase

A condition that occurs when AC waves reach their peak positive and peak negative values at different times. Out-of-phase waves occur in a three-phase generator.

Overcurrent devices

A component that opens a circuit when current rises above a certain level. Common overcurrent devices include circuit breakers and fuses.

Overload relays

A protective relay that opens a motor circuit when overcurrent conditions persist for too long. Overload relays prevent a motor from overheating due to overloading.

Panelboards

A wall-mounted panel or group of panels containing devices used to control, monitor, and distribute electricity. Panelboards are smaller than switchboards and handle less current.

Parallel

An electrical system that has multiple paths for the flow of electricity. Loads connected in parallel can operate independently of one another.

Path

A conductor that directs electricity along a controlled route in a circuit. Paths are often made of copper wires or cables.

Peak negative value

The lowest negative point on an AC wave. Peak negative value is the maximum negative voltage or amperage of the wave.

Peak positive value

The highest positive point on an AC wave. Peak positive value is the maximum positive voltage or amperage of the wave.

Period

The time required for an AC wave to complete one full cycle. Periods are measured in seconds per cycle.

Personal protective equipment

PPE. Any clothing or device worn or used to minimize exposure to hazards and prevent injury. Personal protective equipment for electrical work may include eye and ear protection, dielectric boots, insulated gloves, and an insulated hard hat.

Phase

The timing or position of an AC wave relative to a reference point or another wave. Most AC is either single-phase or three-phase.

Phase voltage

The voltage measured between any one phase conductor in a three-phase system and a neutral conductor. Phase voltage is lower than line voltage in a wye connection but the same as line voltage in a delta connection.

Power

The rate at which one form of energy is converted into another form. Power is measured in watts (W).

Power circuit

A circuit that carries high-energy electricity to a load. Power circuits often have very high voltage and require additional safety precautions.

Preventive maintenance

Regularly scheduled service and upkeep performed while a machine or system is still in working order. Preventive maintenance can prolong equipment life and increase production.

Primary winding

The winding through which current first passes when it enters a transformer. Primary windings bring supplied electricity into the transformer.

Programmable logic controllers

PLCs. A processor-driven device that uses logic-based software to provide electrical control to a machine or process. Programmable logic controllers can be used to automate processes.

Protective relays

A relay designed to open a circuit when it detects dangerous conditions. Protective relays help prevent hazards caused by overcurrent and electrical faults.

Radial system

A distribution system with a single generating station that provides only one path to all end users. In a radial system, the entire system loses electricity if one component malfunctions.

Redundant

A component that duplicates another component's function. Redundant components in distribution systems help protect against electrical outages.

Risk assessments

A documented process that an organization uses to evaluate and plan for possible risks. Risk assessments are necessary for electrical work and many other hazardous activities.

Secondary winding

The winding through which current passes last as it exits a transformer. Secondary windings output electricity from the transformer.

Single-phase

1Φ. Alternating current that consists of only one voltage wave. Single-phase AC is typically used for simple applications like lighting and heating.

Step-down transformers

A transformer that decreases voltage and increases amperage. Step-down transformers have fewer turns in the secondary winding than in the primary winding.

Steps down

To decrease the voltage of electrical current with a transformer. Step-down transformers are used to bring high-voltage electricity down to usable levels.

Steps up

To increase the voltage of electrical current with a transformer. Step-up transformers are used to prepare electricity for long-distance transmission.

Step-up transformers

A transformer that increases voltage and decreases amperage. Step-up transformers have more turns in the secondary winding than in the primary winding.

Substations

A facility that contains switchgear, transformers, and monitoring equipment. Substations alter voltage levels and provide a point of control in distribution systems.

Sulfur hexafluoride

A colorless, non-flammable gas used as an insulator in high-voltage circuit breakers. Sulfur hexafluoride is a better insulator than air or a vacuum.

Switchboard

A freestanding assembly of panels containing devices used to control, monitor, and distribute electricity. Switchboards are common in manufacturing facilities.

Switchgear

A group of devices that control, protect, and isolate components in an electrical system. Switchgear includes devices such as disconnect switches, fuses, and circuit breakers.

Tap-off boxes

A modular unit that attaches to a busway and provides a connection point for loads. Tap-off boxes are movable and can be installed anywhere along a busway.

Three-phase

3Φ. Alternating current that consists of three overlapping voltage waves. Three-phase AC is used for all large AC motors and is the standard electrical supply for factories and industrial buildings.

Transformers

A device that uses mutual induction to transfer electrical energy from one circuit to another without changing the frequency. Transformers are most often used to increase and decrease voltage.

Transmission lines

A conductor that carries high-voltage electricity over long distances. Transmission lines are often suspended on utility poles or buried underground.

Transmission substations

A facility located near a generating station or before a distribution substation that contains multiple step-up or step-down transformers. Transmission substations increase voltage for efficient long-distance travel and then decrease it to usable levels.

Turbines

A wheel or rotor used to produce continuous motion. A turbine is forced to rotate by the fast-moving flow of water, steam, gas, air, or other fluid.

Turns

A loop or wrap of conducting wire in a coil. The number of turns in a coil affects the strength of the magnetic field.

Utility company

An entity recognized by governmental law that installs, operates, and maintains electrical distribution systems. Utility companies generate and transmit AC electricity.

Vacuum

A space with negative air pressure created by removing air with suction. A vacuum is a better insulator than air.

Variable frequency drives

VFDs. A device that converts incoming 60 Hz AC electricity into other desired frequencies. Variable frequency drives can be used to control the speed of AC motors.

VFD

Variable frequency drive. A device that converts incoming 60 Hz AC electricity into other desired frequencies. VFDs can be used to control the speed of AC motors.

Voltage

The electrical force or pressure that causes current to flow in a circuit. Voltage is measured in volts (V).

Volts

V. A unit of measurement that indicates the amount of electrical force or pressure in a circuit. One volt is equal to one ampere multiplied by one ohm.

Waveform

The shape of a wave produced by AC voltage or amperage. Waveforms vary based on the method used to generate electricity.

Wind power

The electrical energy produced by the movement of air against wind turbines. Wind power is a form of renewable energy.

Wye

Y. A connection of three conductors that meet at a central, neutral point and form a Y-shape. Wye connections must usually be grounded.

Wye/delta

A three-phase transformer with a wye primary winding and a delta secondary winding. Wye/delta transformers are used as both step-up and step-down transformers.

Wye/wye

A three-phase transformer with wye connections for both the primary and secondary winding. Wye/wye transformers are uncommon and are used when both sides must be grounded.