July 2, 2011

Electrical Engineering Terms - E

  • Earth Fault Protection System - A protection system which is designed to excite during faults to earth.
  • Earthing Transformer - A three-phase transformer intended essentially to provide a neutral point to a power system for the purpose of grounding.
  • Eddy Current - The current that is generated in a transformer core due to the induced voltage in each lamination. It is proportional to the square of the lamination thickness and to the square of the frequency.
  • EEI - Edison Electric Institute.[www.eei.org]
  • EERA - Electrical Equipment Representatives Association. EERA is an association of electrical manufacturers representatives. Additional information on EERA can be found at www.eera.org. Young & Company is a member of EERA.
  • Effective Internal Resistance (Battery) - The apparent opposition to current within a battery that manifests itself as a drop in battery voltage proportional to discharge current. Its value is dependent on battery design, state-of-charge, temperature and age.
  • Effective Power (Watts) - See "Watt"
  • Effective Range - The range of values of the characteristic quantity or quantities. For example the energizing quantities to which the relay will respond and satisfy the requirements to precision.
  • Effective Setting - The setting of a protection system including the effects of current transformers, this effective setting can be expressed in terms of primary current or secondary current from the current transformers.
  • Effectively Grounded - Intentionally connected conductors or electric equipment to earth, where the connection and conductors are of sufficiently low impedance to allow the conducting of an intended current.
  • Efficiency (Lighting) - A ratio of light emitted from a luminaire to the light produced by the bare lamp.
  • EHV - See "Extra High Voltage".
  • Elbow - A device used to connect a medium voltage cable (4-35KV nominal) to an electrical component such as a switch or transformer. Its name is derived from the fact that its shape is an "L". Elbows are available in ratings of 200, 600 and 900 Ampere and are m
  • Electrical Hazard - A dangerous condition such that contact or equipment failure can result in electric shock, arc flash burn, thermal burn, or blast.
  • Electrical Relay - A device designed to produce sudden predetermined changes in one or more electrical circuits after the appearance of certain conditions in the controlling circuit.
  • Electrical Safety - Recognizing hazards associated with the use of electrical energy and taking precautions so that hazards do not cause injury or death.
  • Electrically Safe Work Condition - A state in which the conductor or circuit part to be worked on or near has been disconnected from energized parts, locked/tagged in accordance with established standards, tested to ensure the absence of voltage, and grounded if determined necessary.
  • Electricity - The flow of electrons through a conducting medium.
  • Electrolyte (Battery) - In a lead-acid battery, the electrolyte is sulfuric acid diluted with water. It is a conductor and also a supplier of hydrogen and sulfate ions for the reaction.
  • Electromechanical Relay - An electrical relay in which the designed response is excited by a relative mechanical movement of elements under the action of a current in the input circuit.
  • Electromotive Force - Potential causing electricity to flow in a closed circuit.
  • Elongation - The amount (% length) that a conductor or other material can stretch before breaking when a pulling force is applied.
  • Embedded Generation - Generation that is connected to a distribution system possibly at LV instead of HV.
  • EMS - See Energy Management System
  • EMTDC™ - Electro-Magnetic Transients for DC. Incorporates both EMTP and ATP, and integrates DC systems and components.
  • EMTP - Electromagnetic Transients Program
  • End Point Voltage - Battery Voltage reached at the termination of a discharge. Also Known as the Cut Off Voltage.
  • End-of-Discharge Voltage - The voltage of a battery at the termination of a discharge but before the discharge is stopped.
  • End-Point Voltage - The Cell or Battery voltage at which point the rated discharge capacity has been delivered at a specific Rate-of-Discharge. It is also used to specify the cell or battery voltage below which the connected equipment will not operate or below which operati
  • Energy - That which does work or is capable of doing work. Electricity is energy that is measured in kilowatt hours.
  • Energy Management System - A system in which a dispatcher can monitor and control the flow of electric power by opening and closing switches to route electricity or to isolate a part of the system for maintenance. It is also used to control the amount of generation needed to serve
  • Entrainment (Battery) - The process whereby gasses generated in the cell carry electrolyte through the vent cap.
  • EPDM - Ethylene Propylene Dione Monimer. This is a synthetic rubber compound used as insulation in making electrical components.
  • EPR - Ethylene Propylene Rubber, a synthetic rubber compound that is used as cable insulation.
  • EPRI - Electric Power Research Institute. EPRI is located at P.O. Box 10412, Palo Alto, CA 94303.
  • EPROM - Electrically Programmable Read Only Memory.
  • Eutectic - An alloy used to form the melting point of a fuse. It is frequently silver or tin based.
  • Event - In the digital world an event is any information acquired or produced by the digital control system.
  • Exciting Current - The magnetizing current of a device such as a transformer. Also known a field current.
  • Expressway Roadway (Lighting) - A divided major roadway for through-traffic with partial control of access and generally with interchanges at major crossroads. Expressways for non-commercial traffic within parks and park-like area are generally known as parkways.
  • Extension, Box - An add-on section that fits to the bottom or to the top of a gread level box, extending its height.
  • Extra High Voltage - An electrical system or cable designed to operate at 345kv (nominal) or higher.
  • Extrusion - The application of a semi-solid rubber or plastic material such as PVC onto a conductor




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