Glossary L
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| L – A symbol used to express inductance. The unit of measure is a “Henry”. |
| Ladder Diagram (LD) – One of the IEC 61131-3 programming languages. |
| Lag – The condition where the current is delayed in time with respect to the voltage in an ac circuit (for example, an inductive load). |
| Lamp – A complete light source unit, usually consisting of a light generating element (arc tube or filament), support hardware, enclosing envelope and base. |
| Lamp Lumen Depreciation, LLD (Lighting) – Information about the chosen lamp and its lumen depreciation and mortality are available from lamp manufacturers’ literature. Rated average life should be determined for the specific hours per start; it should be known when burnouts occur. |
| LAN – Local Area Network which is a short-distance network used to link a group of computers or intelligent devices together, usually within a building. |
| Lateral Circuit – A tap-off line to take primary distribution from the main power line to a nearby load center. |
| Lateral Light Distribution – Lateral light distributions are classified by IES distribution Types I, II, III, IV and V. In general, the larger the number, the more is projected across the roadway. This allows the lighting designer to select the appropriate distribution pattern for |
| Lay Direction – 1) The direction in which the wires of a conductor are twisted. 2) The twist of conductors in a cable. |
| Lay Length – The distance required to complete one revolution of helically laid strands of wires. |
| LCD – Liquid Crystal Display. |
| LDC – A Line Drop Compensator is utilized to provide constant voltage at the load. |
| LDD – Luminaire Dirt Depreciation Factor. |
| Lead – The condition where the current precedes in time with respect to the voltage in an ac circuit (for example, a capacitive load). |
| Lead Acid (Battery) – Term used in conjunction with a cell or battery that utilizes lead and lead peroxide as the active plate materials in a diluted electrolyte solution of sulfuric acid and water. The nominal cell voltage is 2.1 volts. |
| Lead Acid Battery – The assembly of one or more cells with an electrolyte based on dilute sulfuric acid and water, a positive electrode of lead dioxide and negative electrodes of lead. Lead Acid batteries all use the same basic chemistry. |
| Lead Dioxide (Battery) – The higher oxide of lead present in charged positive plates. It is frequently referred to as lead peroxide. |
| Lead Peroxide – See Lead Dioxide. |
| Lead Sulfate – A lead salt formed by the action of sulfuric acid on lead oxide during paste mixing and formation. It is also formed electromechanically when a battery is discharged. |
| LED – Light Emitting Diode. |
| Light – Energy that is capable of exciting the retina and producing a visual sensation. |
| Light Loss Factor (LLF) – A factor used in calculating luminance after a given period of time and under given conditions. It takes into account temperature and voltage variations, dirt accumulation on luminaire and lit surfaces, lamp depreciation, and maintenance procedures. |
| Light Traffic – A grade level Box or Cover rating. See “Incidental Light Traffic”. |
| Lighting Arrester – A device that protects power lines and equipment against high voltage lighting surges and switching surges. Connected from line to ground potential, the device has a very high resistance to current flow at normal voltages. |
| Lighting Maintenance Factor (MF) – The result of time-dependent depreciation effects must be considered in the initial design. Regular maintenance is particularly important with regard to energy conservation and these plans, once incorporated into the design, should be carried out. |
| Lightning – Lightning is a powerful natural electrostatic discharge produced during a thunderstorm. Lightning’s abrupt electric discharge is accompanied by the emission of light. |
| Lightning & Switching Impulses – A distinction is made between Lightning and Switching impulses on the basis of duration of the wave front. Impulses with wave-front durations of up to a few tens of microseconds are in general considered to be lightning impulses. |
| Limit Switch – A protective device used to open or close electrical circuits when certain limits, such as temperature or pressure, are reached. |
| Limited Approach Boundary – An approach limit at a distance from an exposed live part within which a shock hazard exists. |
| Limiting Value of the output current – The upper limit of the output current which cannot, by design be exceeded under any conditions. |
| Line – Refers to the conductor in an overhead or underground distribution or transmission line. |
| Line Hose – A rubber dielectric cover for conductor that is used to electrically isolate a worker from an energized conductor. Line hose is made by W.H. Salisbury & Company. |
| Line Traps – High voltage lines can be used to transmit R. F. carrier signals for the purposes of voice communication, remote signaling and control. The frequency range from 30 to 500 kHz has proven to be advantageous for high frequency carrier transmission. |
| Liner – Cloth gloves used to line the inside of a rubber insulating glove. |
| LLF (Lighting) – Light Loss Factor. |
| Load – 1) The amount of electrical power required by connected electrical equipment. 2) The total impedance of all the items in the output circuit. |
| Load break – Refers to a group of rubber insulating products used to electrically connect apparatus with which load can be separated manually. Loadbreak products are manufactured by T&B Elastimold. |
| Load Loss – See “Coil Loss”. |
| Local Control Mode – When set for a given control point it means that the commands can be issued from this point. |
| Local Roadway (Lighting) – Roadways used primarily for direct access to residential, commercial, industrial or other abutting properties. They do not include roadways carrying through traffic. Long local roadways will generally be divided into short sections by collector roadway. |
| Long Distribution (Lighting) – A luminary is classified as having a long light distribution when its max candlepower point falls between 3.75MH – 6.0MH TRL. The maximum luminaire spacing-to-mounting height ratio is generally 12.0 or less. |
| Long-Term Stability – The stability over a period of one year. |
| LPW – Lumens Per Watt. |
| Lube – Slang for “Cable Pulling Lubricant”. |
| Lumen – Standard unit of measure for light flux or light energy. Lamp light output is measured in Lumens. |
| Lumens Per Watt (LPW) – The ratio of light energy output (Lumens) to electrical energy input (Watts). |
| Luminaire – A complete lighting unit consisting of a light source with a means of distribution (reflector and/or refractor), lamp positioning (socket), lamp protection (housing) and a provision for power connection. |
| Luminaire Dirt Depreciation (LDD) – The accumulation of dirt on luminaires results in a loss of light output on the road. This loss is known as the LDD factor and is determined by estimating the dirt category from the graph below. . |
| Luminaire Dirt Depreciation Factor (LDD) – The multiplier used in luminance calculations to relate the initial luminance provided by clean, new luminaries to the reduced luminance that they it will provide. |
| Luminance – The density of the luminous flux incident on a surface. It is the quotient of the luminous flux multiplied by the area of the surface when the later is uniformly illuminated. |
| Luminance – In a direction and at a point of a real or imaginary surface – The quotient of the luminous flux at an element of the surface surrounding the point, and propagated in directions defined by an elementary cone containing the given direction. |
| Lux – The SI unit of luminance. One lux is one lumen per square meter. |
| LV – Low Voltage. |
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Boyer Tile LLC.