Quantities
Kilovolt-Amperes (KVA): The apparent power in a circuit expressed in 1,000 volt-amperes.
Kilowatts (kW): A unit of measure of power, equal to 1,000 watts.
Megawatt (MW): A unit of measure of power, equal to one million watts.
Apparent Power (VA): The vector sum of real and reactive power in volt-amperes.
Real Power (kW): The power in an electrical circuit produced by current flow and measured in watts after power factor correction.
Reactive Power (kVAR): The power in an electrical circuit produced by the reaction of an inductor and/or capacitor on the current flow. Reactive power, being an inductive or capacitive kVAR, must be in pedal balance to the resistive kW in a system. If the resistive kW and inductive/capacitive kVAR are not in balance, the resultant is a reactive net kVAR.
Voltage (kV): A measurement in kilovolts of the electrical potential difference at two points in a circuit.
Current (A): A measure of the rate of flow of an electric current, expressed in amperes (amps).
Power Factor (PF): The ratio in a circuit between the real power and the apparent power.
Asymmetrical Load: Non-symmetrical current loading on three-phase power or systems, such as a sudden, high-current single-phase field excitation of a motor or transformer, causing a higher current on one leg of the power system than the other two.
Frequency (Hz): A measure of the number of alternating cycles of current or voltage in one second.
Demand (=Maximum Load): The greatest amount of power, as measured in kilowatts (kW), taken in any interval of time, usually 15 minutes or 1 hour.
Load Factor: The ratio of the average load (KW) to the maximum demand (KW).
Equipment Ratings
Circuit Breaker: A device designed to interrupt current flow in a circuit, usually employed to protect other devices from fault currents.
Conductor: Any material through which electrical current may flow.
Line Voltage Regulator: A device, usually an autotransformer, which is used to provide a controlled, constant voltage to a load.
Load Tap Changer (LTC): A device that is used to make automated and accurate adjustments to the output voltage of a transformer as required by the electrical system load.
Motor Control Center (MCC): A pre-engineered device comprised of motor control elements that combine to make a motor control system.
Switchgear: That portion of electrical equipment used to connect or disconnect power circuits, which includes lightning or surge arrester and current fuses, circuit breakers, switches, relays, etc.
Terminal Blocks: Connector equipment used to interconnect electrical components.
Transformer: A device used to step up or step down voltage in an AC electrical circuit.
Voltage Sensitive Relay (VSR): A relay used to detect a voltage increase above a predetermined level, providing a switch contact closure as a result.
Other Terms
Advanced Distribution Automation (ADA): Distributed digital control systems that reduce outage times and improve the reliability, utilization, and throughput of parts of a distribution system.
Arc Flash: A type of electric arc over currents in distribution systems that can cause severe damage to nearby personnel and equipment.
Automatic Voltage Regulator (AVR): A device used to control a voltage regulator with an automatic regulator and other automated devices.
DeviceNet: A communication network and protocol used to interconnect nodes and devices used in an automated system.
Distribution Automation (DA): Also known as Advanced Distribution Automation (Advanced DA), a complex network of automation systems that integrate automated controller, measurement, monitoring, protection, and communication devices to improve the operational performance of power distribution systems.
Dynamic Reactive Compensation: The injection of reactive power from a capacitor or other power sources to balance out the load on a distribution system.
Gearless Power Conversion (GPC): An integrated system that combines distributed generation sources and dynamic compensation power sources to maintain voltage stability on a power distribution system.
Grid-Connected: Also known as Utility-Connected, a power system connected to the power grid in which power is produced, distributed and consumed in an integrated fashion.
Overcurrent Protection: An element of power system protection to guard against overloads, short circuits, and other fault current conditions.
Real-Time Monitoring: The process of measuring and recording real-time data on the power distribution system, such as voltage, frequency, temperature, etc.
System Loss: The sum total of line losses and heat losses associated with a particular power systems network.
Uninterruptible Power Supply (UPS): A backup power supply that is capable of supplying power to a load when the primary source fails.
