Here is an explanation of the terms used for Customer-Owned Renewable Generation:
- Alternating Current (AC)
- Electric current that alternates or changes in magnitude and polarity
(direction) in what is normally a regular pattern for a given time period.
The number of direction changes in a given time period is called the
frequency. Alternating current is supplied by the utility to your home or
- Self-acting; operated by its own mechanism when actuated by some
impersonal influence, such as a change in current strength. Not manual.
Without personal intervention.
- Automatic Reclosing
- The closing of a circuit breaker without manual intervention after it
has tripped under abnormal conditions.
- Automatic Tripping (Automatic Opening; Automatic Disconnecting)
- The opening of a circuit breaker under predetermined conditions without
the intervention of an operator.
- Biomass/Agricultural Digesters
- Anaerobic digesters that over time convert waste products, such as farm
manure, into methane, which can then be combusted.
- A flow of electric charge measured in amperes.
- Current Transformer (CT)
- A transformer intended for metering, protective or control purposes,
which is designed to have its primary winding connected in series with a
circuit carrying the current to be measured or controlled. A current
transformer normally steps down current values to safer levels. A current
transformer secondary circuit must never be open circuited while energized.
- Delivered Energy
- Energy sold to the utility.
- Delta Connected Circuit
- A three-phase circuit with three source windings connected in a closed
delta (triangle). A closed delta is a connection in which each winding terminal
is connected to the end (terminal) of another winding.
- Direct Current (DC)
- An electric current flowing in one direction only and substantially
constant in value. For example, a flashlight uses direct current produced by
- A device used to isolate a piece of equipment. A disconnect may be gang
operated (all poles switched simultaneously) or individually operated.
- Federal Energy Regulatory Commission. FERC is an independent body within
the Department of Energy (DOE) that regulates interstate transmission and the
prices of electricity and natural gas. It also licenses hydroelectric projects,
interconnections, construction work in progress, rates for wholesale customers,
and utility accounting practices and procedures.
- The number of cycles occurring in a given interval of time (usually one
second) in an electric current. Frequency is commonly expressed in hertz.
- Fuel cells
- Cells that produce electric and thermal energy through an electrochemical
process using hydrogen, which can be produced from natural gas or by renewable
- A short piece of conducting material of low melting point that is inserted
in a circuit for the purpose of opening the circuit when the current reaches a
certain value at which point the fuse melts, disconnecting the circuit.
- A large conducting body, such as the earth, used as a return for electric
currents and as an arbitrary zero of potential. For safety purposes, circuits
are grounded while any work is being done on or near a circuit or piece of
equipment in the circuit; this is usually called protective or safety
- Denotes frequency equivalent to cycles per second.
- The Institute of Electrical and Electronics Engineers.
- Induction Generator
- An induction generator is constructed the same as an induction motor
except it is spun by its prime mover at higher than synchronous speed. It
requires an external source of magnetizing current, which can be supplied by
a capacitor or, if interconnected to the utility, by the utility system. The
two major components of an induction generator is the stator or the stationary
portion, which has a series of coils wound around it that produce a rotating
magnetic field and a rotor which typically has a set of rods running lengthwise
and shorted together at the ends. As the rotating magnetic field cuts across
those rods, a current is induced creating a corresponding magnetic field. If the
rotor is spinning slower than the rotating field in the stator, it operates as
a motor; but if it is driven faster than the rotating field, it acts as a
- Internal Combustion Engine
- Device much like an automotive engine, fueled with either diesel or natural
gas, connected to and driving an electrical generator.
- The physical connection of distributed generation to the utility system so
that parallel operation can occur.
- Interconnection Agreement
- The standard form of agreement, which has been approved by the Commission.
The interconnection agreement sets forth the contractual conditions under
which a utility and a customer agree that one or more facilities may be
interconnected with the utility’s distribution system.
- A temporary discontinuance of the supply of electric power.
- An electronic circuit that changes direct current (DC) to alternating
current (AC) by turning on and off semi-conducting switches in the proper
sequence and at the proper speed to get the desired frequency. In most wind
turbines, an induction generator creates alternating current of variable
frequency due to variations in the wind speed, which is then rectified to DC.
This DC is then converted to the desired AC frequency via an inverter.
Inverters are also used on solar panels, as solar panels only generate DC.
Inverters can either be self-commutated or line commutated. A self-commutated
inverter does not need utility grid power to generate electricity, where as a
line commutated inverter does. Inverters certified to UL-1741 meet the
requirements of IEEE-1547 and will drop off-line if the utility power is lost
to avoid creating an unsafe condition on the utility system and damaging the
customer’s generator installation. Inverters can also cause issues with motors
and other electronic equipment, because they can generate high levels of
harmonic distortion causing excess heating and miss-operation.
- Independent Power Producer. A non-utility organization that operates a
power plant, produces energy, and sells the energy to a utility.
- A part of an interconnected system that is isolated during a system
disturbance and starts operating as a subsystem with its own generation,
transmission and distribution capability. When this occurs, the island system
and the main interconnected system will operate at different frequencies and
- Kilowatt (kW)
- An electric unit of power that equals 1,000 watts. One watt is the basic
measure of electrical power and is equal to one volt of electrical potential
multiplied times one ampere of current.
- Kilowatt-hour (kWh)
- One thousand watts of power supplied for one hour. A basic unit of
electric energy equal to the use of one kilowatt for a period of one hour.
- Lagging Power Factor
- When reactive power is predominately inductive, such as with high motor
loads or large amounts of transformers.
- Leading Power Factor
- When reactive power is predominately capacitive, such as a circuit with
large amounts of power factor capacitors or over-excited synchronous
- Line Losses
- Electrical energy converted to heat in the resistance of all transmission
and/or distribution lines and other electrical equipment.
- Micro turbines
- Small combustion turbines that burn natural gas to produce less than 500
kW. Simpler than internal combustion engines, they have only one moving part
on a central rotating shaft that generates electricity. They are characterized
by simple design, modularity and fuel flexibility.
- A unit of electrical resistance equal to that of a conductor in which a
current of one ampere is produced by a potential of one volt across its
- One-Line Diagram
- A diagram in which several conductors are represented by a single line and
various devices or pieces of equipment are denoted by simplified symbols. The
purpose of such a diagram is to present an electrical circuit or circuits in a
simple way so their function can be readily grasped.
- Parallel Operation
- The operation of a customer-owned generator while connected to the utility’s
- Point of Energy Exchange
- The point in the delivery system where one party takes delivery of the
energy from the other party. This point is defined in the contract between the
utility and the customer. It is often the point where facility ownership changes.
This point may also be called the Point of Interchange when dealing with a
bi-directional energy exchange or the Point of Delivery if the energy flows in
- Point of Interconnection
- The point where the customer’s conductors meet the utility’s (point of
- Point of Metering
- The point where metering equipment (meters, transducers, current
transformers, potential transformers, etc.) is, or will be, installed to measure
the power flow and energy exchange between the utility and the customer.
- All of the relays and other equipment that are used to open the necessary
circuit breakers to clear lines or equipment when trouble develops.
- The voltage of an electrical circuit.
- Qualifying Facility. An Independent Power Producer (IPP) that has met
criteria to be certified by FERC as a Qualifying Facility and that has rights
established by the PURPA of 1978.
- To return a circuit breaker to its closed position after it has opened by
- A device that is operative by a variation in the condition of one electric
circuit to affect the operation of another device in the same or in another
- An electric machine in which the field current is secured from its own
- Separately Excited
- Use of an exciter for sending current through the field windings of an
electric machine in place of taking the field current from its own armature
- Photovoltaic materials contained in solar cell array convert energy from
sunlight directly into electricity, typically connecting to utility
distribution system via inverter.
- A device for making, breaking or changing the connections in an electric
- Synchronous Generator
- A synchronous generator has two main components, a stator and a rotor. The
stator has a series of coils wrapped around it as does the rotor. A DC current
is applied to the rotor through a set of slip rings to set up a magnetic field.
As the rotor is turned, the magnetic field cuts across the windings in the
stator and induces an alternating current in them.
- Expresses the condition across an open circuit wherein the voltage sine
wave on one side matches the voltage sine wave on the other side in frequency
and amplitude without phase angle difference.
- An electric device, without continuously moving parts, in which
electromagnetic induction transforms electric energy from one or more other
circuits at the same frequency, usually with changes of value, voltage and
- Utility Grade Relays
- Relays which meet IEEE standards C37.90, C37.90.1, and C37.90.2.
- The electromotive force or electrical potential causing current to flow in
a circuit. One volt will cause one ampere to flow through a resistor of one ohm
dissipating one watt of energy in the form of heat.
- Wind turbine generators, harnessing energy contained in wind to turn wind
turbine blades connected to generator for electricity production.
- Wye or “Y” Connected Circuit (Star Connected)
- A three-phase circuit in which windings of all three phases have one common
connection. The UPPCO distribution system is a grounded wye system where the
common point is connected to ground.