Additional Terms Flashcards
Backup Relays
Relays that protect the same electrical equipment that the primary relays protect. They operate after a time delay and would generally affect more of the power system.
Bilateral
Affecting two parties, involving two groups, symmetry. Bilateral interchange is at least two Balancing Authorities that agree to move power generation from one party to another.
Capacitance
The property of an electrical circuit developed when two conductors are separated by a dielectric.
Capacitive Reactance
A measure of how a capacitor affects the flow of AC current. It describes the reaction of a circuit to the fluctuating electric fields of AC voltage. A capacitor that is placed into an AC circuit builds up a charge that opposes changes in the voltage.
Capacitor
A circuit element that stores energy in the form of an electrical charge and introduces capacitance into a circuit. The stored energy creates an electric field.
Control Performance Standard 1 (CPS1)
A frequency-sensitive evaluation of how well a Balancing Authority’s demand requirements were met. A CPS1 score of 200% is perfect (actual measured frequency equals scheduled frequency over any 1-minute period). The minimum passing long-term (12-month rolling average) score for CPS1 is 100%. CPS1 is a 12-month rolling average that recognizes that certain intervals will not have ideal performance and certain seasons may not be well managed.
Current Transformer
Instrument transformers designed for transforming large current magnitudes to secondary current suitable for relaying and metering. The secondary current flow is proportional to the larger primary current flow.
Cycle
One full sine wave cycle that is divided into 360 degrees. The wave form passes through zero, rises to a maximum, drops back to zero, drops to a minimum, then rises again to zero. Both current and voltage in North America power systems have cycle wave forms that will repeat 60 times a second.
Data Link
The means of connecting one location to another for the purpose of transmitting and receiving information.
Differential Relay Zone
A closed zone of protection. The current flowing into the protection zone must equal the current flowing out of the protection zone.
Direct Current
Current that flows in one direction only and is substantially constant in value.
Dynamic Reactive Reserves
Reactive power reserves that automatically respond to system voltage deviation. These reserve sources include synchronous generators, synchronous condensers, and static VAR compensators.
Energy Management System (EMS)
A system of computer-aided tools used by operators to monitor, control, and optimize the performance of the generation and/or transmission system. The monitor and control functions are known as SCADA, the optimization packages are often referred to as advanced applications.
Energy Sharing Agreement
Refers to an agreement among several parties to mutually cover the loss of resources. One example of an energy sharing agreement is the reserve-sharing group.
Epsilon-Sub One
Epsilon-Sub One is a constant derived from the targeted frequency bound. It is the targeted root mean square of one-minute average frequency error of the Interconnection for one minute. It is the same for every Balancing Authority Area within an Interconnection. It is the limit for determining a Balancing Authority’s compliance with Control Performance Standard 1 (CPS1).
Epsilon-Sub Ten
Epsilon-Sub Ten is a constant derived from the targeted frequency bound. It is the targeted root mean square of ten minute frequency error schedule based on frequency performance over a given year. It is the same for every Balancing Authority Area within an Interconnection. It is used in the calculation of a Balancing Authority’s L sub 10 for CPS2 compliance.
Frame Relay
Frame Relay is an extremely efficient data transmission technique used to send digital information such as voice, data, local area network and wide area network traffic quickly to many destinations from one point of origin.
Generator Droop Characteristic
Allows parallel operation of many generators on governor control in response to frequency deviations without competing with each other. It controls the generator response in proportion to its size. The droop characteristic of a generator determines how much its loading will change in response to a frequency deviation.
Impedance
A measure of the total opposition to current flow in an alternating current circuit. It has two components; resistance and reactance.
Inductance
The property of an electric circuit by which an electromotive force is induced in it as the result of a changing magnetic flux. Inductance opposes current changes.
Inductive Reactance
A measure of how an inductor affects the flow of current. It describes the reaction of a circuit to the fluctuating magnetic fields of AC power. It is measured in ohms.
Inductor
A coiled conductor. A circuit element that stores energy in its magnetic fields and introduces inductance into a circuit.
Inertia
The property of a rotating object that causes it to resist changes in momentum which is dependent upon the mass, diameter, and speed of the object. A generator resists a change to its speed of rotation due to the inertia of its rotor.
Information Assets
For purposes of the NERCNet Security Policy, information assets are processed or unprocessed data using NERCNet, including network documentation.
Instability
A voltage, angle or power flow condition where the transmission system is likely to suffer catastrophic failure should the existing conditions persist. Complete failure of a large are may be caused by voltage collapse, angular separation and/or by suffering a credible contingency.
