Customer-owned renewable generation definitions

Here is an explanation of the terms used for customer-owned renewable generation:

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 business.
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.
The closing of a circuit breaker without manual intervention after it has tripped under abnormal conditions.
The opening of a circuit breaker under predetermined conditions without the intervention of an operator.
Anaerobic digesters that over time convert waste products, such as farm manure, into methane, which can then be combusted.
Nameplate rating of generator in kW DC for invertor-based generating systems such as photovoltaic (solar) systems for PG-4, PG-2A, PG-2B, PG-2C rates and all PSC 119 categories.
A flow of electric charge measured in amperes.
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.
Energy sold to the utility.
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.
An electric current flowing in one direction only and substantially constant in value. For example, a flashlight uses direct current produced by the batteries.
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.
Cells that produce electric and thermal energy through an electrochemical process using hydrogen, which can be produced from natural gas or by renewable energy resources.
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 grounding.
Denotes frequency equivalent to cycles per second.
The Institute of Electrical and Electronics Engineers.
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 generator.
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.
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 voltages.
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.
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.
When reactive power is predominately inductive, such as with high motor loads or large amounts of transformers.
When reactive power is predominately capacitive, such as a circuit with large amounts of power factor capacitors or over-excited synchronous generators.
Electrical energy converted to heat in the resistance of all transmission and/or distribution lines and other electrical equipment.
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 terminals.
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.
The operation of a customer-owned generator while connected to the utility's grid.
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 one direction.
The point where the customer's conductors meet the utility's (point of ownership change).
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 relay action.
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 electric circuit.
An electric machine in which the field current is secured from its own armature current.
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 current.
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 circuit.
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 current.
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.
A three-phase circuit in which windings of all three phases have one common connection. The WPS distribution system is a grounded wye system where the common point is connected to ground.