Not sure of a definition? Check out our glossary of common terms

Alternating current (AC): An electrical current that reverses direction of flow at regularly occurring intervals; contrast with direct current (DC).

Automated meter reading (AMR): Otter Tail Power Company's system is automated meter reading transmittal. Someone still enters the reading from the meter into a hand-held unit that, when placed into its cradle, transmits the meter reading automatically.

Ampere: The unit of measure of electric current. It's proportional to the quantity of electrons flowing through a conductor past a given point in one second. It's analogous to cubic feet of water flowing per second.

Ash: The noncombustible residue of burned coal. Ash occurs in raw coal as clay, pyrite, or other mineral matter.

Base load: A utility's minimum load over a given period; a base-load generating plant is designed for continuous operation and generates electricity around the clock.

Btu (British thermal unit): The standard unit for measuring heat energy in fuel. It's the amount of heat energy required to raise the temperature of one pound of water one degree Fahrenheit. 1 kW = 3,413 Btu.

Capability: The maximum load that a generating unit or other electrical apparatus can carry without exceeding limits of temperature or stress.

Circuit: A conductor or system of conductors through which an electric current flows.

Conductor: A wire through which electricity flows.

Connected load: A customer's total load on the electrical system if all of the customer's electrically powered equipment were operating at one time. Connected load can be measured in horsepower, watts, or volt-amperes. Some rate schedules establish a minimum demand charge by imposing a fee per unit of connected load.

Current: The flow of electricity through a conductor measured in amperes.

Demand: A measure of the customer load connected to the electrical system at any given time. Units are usually watts or volt-amperes.

Direct current (DC): An electrical current that flows continuously in one direction; contrast with alternating current (AC).

Distribution: The process of conveying electric energy from the generating source or substation to the point of use.

Distribution line: A circuit on the same line of poles or structures operating at relatively low voltage (15 kv – 600 v); contrast with transmission lines that operate at higher voltages.

Eminent domain: The power of a government body to condemn private property for public use; sometimes used as a last resort by electric utilities constructing power lines. Property owners are compensated for the use of their condemned property.

Energy: The capacity to do work.

Energy, electric: As commonly used in the electric utility industry; it means kilowatt-hours.

Energy interchange: Kilowatt-hours delivered to or received by one utility system from another. They may be returned in kind at a later time or may be accumulated as energy balances until the end of a stated period.

Energy, off-peak or on-peak: Energy supplied during periods of low (off-peak) or high (on-peak) system demands.

Firm power: Power intended to be available at all times, even under adverse conditions, during the period covered by a commitment.

Grounded: Connected to earth or to some extended conducting body that serves instead of the earth, whether the connection is intentional or accidental.

Horsepower (hp): A unit of power, or the capacity of a mechanism to do work. One horsepower equals 746 watts.

Insulation: Material having high resistance to electricity that prevents possible contact between conductors.

Kilovolt (kv): One thousand volts.

Kilowatt (kW): 1,000 watts; a measure of the rate of electricity generation or consumption.

Kilowatt-hour (kWh): A unit of electrical measurement indicating the expenditure of 1,000 watts for one hour. Higher quantities are expressed in megawatt-hours (MW), or the expenditure of one million watts for one hour.

Lignite: A soft coal that ranks below subbituminous coal in energy value. We generate electricity at Coyote Station using lignite.

Load: The amount of electric power delivered or required at any point on a system; the load originates at the customer's power-consuming equipment.

Load factor: A quantity related to connected load, installed load, and contracted load capacity. Utilities use load factor to establish a minimum billing demand. Normally known as the ratio of average load to peak load, expressed as a percentage.

Loss: Energy (kilowatt-hours) and power (kilowatts) lost in an electrical system; losses occur principally as waste heat.

Megawatt (MW): One thousand kilowatts or one million watts.

Neutral: The conductor chosen as the return path for the current from the load to the source in power-measurement procedures. The neutral conductor normally is grounded and will carry unbalanced current in three-phase circuits and the return current in single-phase circuits.

Peak load: Maximum electricity demand.

Power: The time rate of generating, transferring, or using electric energy, usually expressed in kilowatts.

Power factor: The ratio of real power in watts of an alternating-current circuit to the apparent power in volt-amperes. In addition, the cosine of the phase angle between the voltages applied to a load and the current passing through it. It's always between zero and one. Purely resistive load will have a power factor of 1.0 and a motor load will have about a .8 power factor.

Power pool: Two or more interconnected electric systems planned and operated to supply power in the most reliable, economical manner for their combined load requirements and maintenance program.

Service: Conductors operating at less than 600 volts from Otter Tail Power Company's transformer, pedestal, or pole to a building. If the conductors do not end on a building, these conductors are secondary and NOT service wires. Example: Wire to meter pole on farm or meter pedestal next to mobile home is secondary.

Service entrance: Conductors installed and paid for by the customer between the point of attachment of the service or secondary and the customer's service equipment within or on a building.

Service equipment: The circuit breakers or switches and fuses installed and paid for by the customer and located near the point of entrance of the service entrance; intended to be the main controls and means of cutoff for the electric supply to the building.

Single-phase: An alternating-current circuit in which only one phase of current is available in a two-conductor or three-conductor system.

Step-down transformer: A device for changing the small current at high voltage that's transmitted from power plant to local substation into larger current at lower voltage for consumer use.

Subbituminous coal: A high-energy soft coal that ranks below bituminous coal but higher than lignite in energy value. It generally has high heat content and can be readily ground for easy combustion. We use subbituminous coal to generate electricity at Big Stone Plant.

Substation: Equipment used for switching and/or changing or regulating the voltage of electricity. Step-down substations reduce voltage and step-up substations raise voltage.

Transformer: An electromagnetic device for changing the voltage of alternating-current electricity.

Transmission: The process of transporting electric energy in bulk from a source of supply to other parts of the system or to another utility.

Transmission line: A circuit on the same line of poles or structures operating at relatively high voltage—contrast with distribution lines that operate at lower voltages.

Turbine generator: A device consisting of blades attached to a shaft that generates electricity.

Voltage (v): The force that causes current to flow through a conductor. One volt equals the force required to produce a current flow of one ampere through a resistance of one ohm. Potential energy; a measure of the difference in electrical potential of two points.

Watt (w): A measure of real power; power required to do work at the rate of one joule per second. It's the power expended when one ampere of direct current flows through a resistance of one ohm under a pressure of one volt. It's analogous to horsepower or foot-pounds per minute of mechanical power.