Abrasion Resistance ** Ability of material or cable to resist surface wear.


Alternating Current (AC) — A type of electrical current, the direction of which is reversed at regular intervals or cycles. In the Canada and the United States, the standard is 120 reversals or 60 cycles per second.  Frequency is expressed in cycles per second (Hertz or Hz). Electricity transmission networks use AC because voltage can be controlled with relative ease.

Alternating Current ** An electric current that continually reverses its direction giving a definite plus and minus wave form at fixed intervals.

Alternating Current Resistance ** The resistance offered by any circuit to the flow of alternating current.

Ambient Temperature ** Any all encompassing temperature within a given area.

American Wire Gage (AWG) ** The standard system used for designating wire diameter. Also referred to as the Brown and Sharpe (B&S) wire gage.

American Wire Gauge (AWG) — A standard system for designation wire diameter. Also referred to as the Brown and Sharpe (B&S) wire gauge.

Ampacity ** (See current-carrying capacity).

Amperage Interrupt Capability (AIC) — direct current fuses should be rated with a sufficient AIC to interrupt the highest possible current.

Ampere (amp) — A unit of electrical current or rate of flow of electrons. One volt across one ohm of resistance causes a current flow of one ampere.

Ampere Hour Meter — An instrument that monitors current with time. The indication is the product of current (in amperes) and time (in hours).

Ampere-Hour (Ah/AH) — A measure of the flow of current (in amperes) over one hour; used to measure battery capacity.

Anneal ** To subject to heat with subsequent cooling. When annealing copper; the act of softening the metal by means of heat to render it less brittle.

Anti-Oxidant ** A substance which prevents or slows down oxygen decomposition of a material.

Anti-Ozonant ** A substance which prevents or slows down material degradation due to ozone reaction.

Antimony is  added to lead to increase hardness. The high antimony content also reduces long discharge capability and increases the gases produced by the cells during charging.

Armor ** Mechanical protection usually accomplished by a metallic layer of tape, braid or served wires. Normally found only over the outer sheath.

Armored Cable ** A cable provided with a wrapping of metal, usually steel wires, flat tapes, or interlocked tapes, primarily for the purpose of mechanical protection.

ASTM ** Abbreviation for American Society for Testing and Materials.

AWG ** Abbreviation for American Wire Gage, a standard system used for designating wire diameter. Also referred to as the Brown and Sharpe (B&S) wire gage.

B&S Gage ** Brown and Sharpe wire gage used for copper conductor (same as American Wire Gage).

Binder ** A helically applied tape or thread used for holding assembled cable components in place until additional manufacturing operations are performed.

Blocking Diode — A semiconductor connected in series with a solar cell or cells and a storage battery to keep the battery from discharging through the cell when there is no output, or low output, from the solar cell. It can be thought of as a one-way valve that allows electrons to flow forwards, but not backwards.

Boot ** A protective covering over any portion of a cable or conductor in addition to its jacket or insulation.

Braid ** A fibrous or metallic group of filaments interwoven in cylindrical form to form a covering over one or more wires.

Breakdown (Puncture) ** A disruptive discharge through insulation due to failure under electrostatic stress.

Breakdown Voltage ** The voltage at which the insulation between two conductors, or a conductor and ground will break down.

Building Wire ** Wire used for light and power in permanent installations utilizing 600 volts or less. Usually in an enclosure and which will not be exposed to outdoor environments.

Bunch Stranding ** A method of stranding where a single conductor is formed from any number of wires twisted together in the same direction, such that all strands have the same lay length, but no specific geometric arrangement.

Butt Joint ** A splice or connection formed by placing the ends of two conductors together and joining them by welding, brazing or soldering.

Butt Wrap ** Tape wrapped in an edge- to -edge manner with no over-lapping between adjacent turns.

Bypass Diode — A diode connected across one or more solar cells in a photovoltaic module such that the diode will conduct if the cell(s) become reverse biased. It protects these solar cells from thermal destruction in case of total or partial shading of individual solar cells while other cells are exposed to full light

Cable Core ** A cable core is the portion of an insulated cable lying under the protective covering or coverings.

Cable Filler ** The material used in multiple conductor cables to occupy the spaces formed by the assembly of components, thus forming a core of the desired shape.

Capacitance (Capacity) ** That property of a system of conductors and dielectrics which permits the storage of electricity when potential difference exists between the conductors.

Capacitive Coupling ** Electrical interaction between two conductors caused by the capacitance between them.

Capillary Action ** The phenomenon of liquid rising in a small interstice due to surface tension.

Carbon Black-A black pigment. ** It imparts useful ultraviolet protective properties, and so is frequently suspended into plastic and elastomeric compounds intended for outside weather exposure.

Charge Controller — A component of a photovoltaic system that controls the flow of current to and from the battery to protect it from over-charge and over-discharge. The charge controller may also indicate the system operational status.

Charging Current ** The current produced when a d-c voltage is first applied to conductors of an unterminated cable. It is caused by the capacitive reactance of the cable, and decreases exponentially with time.

Chlorinated Polyethylene (CPE) ** A synthetic rubber jacketing compound.

Chlorosulfonated Polyethylene (CSPE) ** A synthetic rubber jacketing compound manufactured by Du Pont under trade name of Hypalon.

Circular Mil ** A unit of area equal to the area of a circle whose diameter is 1 mil (0.001 inch). Used chiefly in specifying cross-sectional areas of round conductors.

Coating ** A material applied to the surface of a conductor to prevent environmental deterioration, facilitate soldering or improve electrical performance.

Cold Flow ** Any permanent deformation due to pressure or mechanical force, without the aid of eat softening.

Cold Joint ** A soldered joint made with insufficient heat.

Cold Test ** Any test to determine the performance of cables during or after subjection to a specified low temperature for a specified time.

Cold Work ** The hardening and embrittlement of metal by repeated flexing action.

Color Code ** A color system for circuit identification by use of solid colors tracers, braids surface Printing, etc.

Compact round conductor ** A conductor constructed with a central core surrounded by one or more layers of helically laid wires and formed into final shape by rolling, drawing, or other means.

Compact Stranded Conductor ** A unidirectional or conventional concentric conductor manufactured to a specified diameter, approximately 8 to 10% below the nominal diameter of a noncompact conductor of the same cross-sectional area.

Concentric ** lay Conductor ** Conductor constructed with a central core surrounded by one or more layers of helically laid wires. Several types are as follows:

Concentric Stranding ** A method of stranding, wherein a single conductor is formed from a central wire surrounded by one or more layers of helically layed wires. Each layer is applied with an opposite direction of lay. The first layer has six wires, and each additional layer has six more wires than does the previous one. Thus the second layer has twelve wires, the third layer has eighteen wires, etc.

Concentricity ** In a wire or cable, the measurement of the location of the center of the conductor with respect to the geometric center of the circular insulation.

Conductivity ** A term used in describing the capability of a material to carry an electrical charge. Usually expressed as a percentage of copper conductivity -- copper being one hundred (100%) percent. Conductivity is expressed for a standard configuration of conductor.

Conductor — The material through which electricity is transmitted, such as an electrical wire, or transmission or distribution line.

Conductor ** A wire or combination of wires not insulated from one another, suitable for carrying an electric current.

Conductor Core ** The center strand or member about which one of more layers of wires or members are laid helically to form a concentric-lay or rope-lay conductor.

Contact Resistance — The resistance between metallic contacts and the semiconductor.

Continuous Vulcanization ** Simultaneous extrusion and vulcanization of wire coating materials. It is abbreviated CV.

Contrahelical ** A term meaning the application of two or more layers of spirally twisted, served, or wrapped materials where each successive layer is wrapped in the opposite direction to the preceding layer.

Conventional concentric conductor ** Conductor constructed with a central core surrounded by one or more layers of helically laid wires. The direction of lay is reversed in successive layers and generally with an increase in length of lay for successive layers.

Conversion Efficiency — See photovoltaic (conversion) efficiency.

Converter — A unit that converts a direct current (dc) voltage to another dc voltage.

Cord ** Small, flexible insulated cable usually size l0AWG or smaller.

Core ** Any portion of a cable over which some other cable component, such as a shield, jacket, sheath or armor, is applied.

Corona ** A luminous discharge due to ionization of the gas surrounding a conductor around which exists a voltage gradient exceeding a certain critical value.

Corona Resistance ** The time that insulation will withstand a specified level field-intensified ionization that does not result in the immediate complete breakdown of the insulation. Also called voltage endurance.

Corona Test ** A test to determine the ability of a cable to withstand the formation of corona under an increasing applied voltage, and to extinguish corona when a corona-producing voltage is reduced.

Crazing ** Minute lines appearing in or near the surface of materials, such as ceramics and plastics usually resulting as a response to environment. Crazing cannot be felt by running a fingernail across it. If the fingernail catches, it is a crack, not crazing.

Creep ** The dimensional change with time of a material under load. At room temperature, it is sometimes called cold flow.

Creepage ** Electrical leakage on a solid dielectric surface.
Crimp Termination ** A wire termination that is applied by physical pressure of terminal to wire.

Cross Linking ** The establishment of chemical bonds between polymer molecule chains. It may be accomplished by heat, vulcanization, irradiation or the addition of a suitable chemical agent.

Cross Sectional Area ** The area of the cut surface of an object cut at right angles to the length of the object.

Cross Sectional Area of a Conductor ** The sum of cross sectional areas of all the individual wires composing the conductor. It is generally expressed in circular mils.

Crush Resistance Test ** A test to determine the ability of a cable to resist damage from radial compression, such as might be encountered in service.

Cure ** (See Vulcanization.)

Current — See electric current.

Current-carrying Capacity ** The maximum current an insulated conductor or cable can continuously carry without exceeding its temperature rating. It is also called ampacity.

Cut-through ** Resistance of solid material to penetration by an object under conditions of pressure, temperature, etc.

Cut-through Resistance ** The ability of a given material to withstand penetration by a solid object of specified dimensions and weight, which is permitted to free fall onto this material from a specified height.

Cutoff Voltage — The voltage levels (activation) at which the charge controller disconnects the photovoltaic array from the battery or the load from the battery.

CV (Continuous Vulcanization) ** Simultaneous extrusion and vulcanization of wire coating materials.

Cycle ** One complete sequence of variations in an alternating current. The number of cycles occurring in one second is called the frequency.

Cycles (Battery)- A period of discharge and recharge is called one cycle. Battery performance may be measured by the expected number of cycles it may deliver at varying depths of discharge.

DC — See direct current.

DC-to-DC Converter — Electronic circuit to convert direct current voltages (e.g., photovoltaic module voltage) into other levels (e.g., load voltage). Can be part of a maximum power point tracker.

Decibel ** Unit to express differences of power level. It is used to express power loss in cables.

Density ** The weight per unit volume of a substance.

Depth of Discharge (DOD)- is the ratio of amp hours removed from a battery versus its full capacity. For example 25 Ah are removed from a 100 Ah battery, thus it's depth of discharge is 25% and the battery is at a 75% state of charge.

Derating Factor ** A factor used to reduce a current carrying capacity of a wire when used in other environments from that for which the value was established.

Dielectric breakdown ** The voltage at which a dielectric material is punctured; which is divisible by thickness to give dielectric strength.

Dielectric Constant ** That property (K) of an insulating material which is the ratio of the parallel capacitance (C) of a given configuration of electrodes with the material as the dielectric, to the capacitance of the same electrode configuration with a vacuum as the dielectric.

Dielectric Strength ** The voltage which an insulating material can withstand before breakdown occurs, usually expressed as a voltage gradient (such as volts per mil).

Dielectric Tests ** 1). Tests which consist of the application of a voltage higher than the rated voltage for a specified time for the purpose of determining the adequacy against breakdown of insulating materials and spacings under normal conditions. 2). The testing of insulating materials by application of constantly increasing voltage until failure occurs.

Diode — An electronic device that allows current to flow in one direction only. See blocking diode and bypass diode.

Direct Current (DC) — A type of electricity transmission and distribution by which electricity flows in one direction through the conductor, usually relatively low voltage and high current. To be used for typical 120 volt or 220 volt household appliances, DC must be converted to alternating current, its opposite.

Direction of Lay ** The lateral direction, designated as left-hand or right-hand, in which the wires of a member or units of a conductor run over the top of the member or conductor as they recede from an observer looking along the axis of the member or conductor.

Discharge Rate — The rate, usually expressed in amperes or time, at which electrical current is taken from the battery.

Disconnect — Switch gear used to connect or disconnect components in a photovoltaic system.

Dissipation ** Unusable or lost energy, as the production of unused heat in a circuit.

Drain Wire ** An uninsulated wire, usually placed directly beneath and in electrical contact with a grounded shield, which is used for making ground connections.

Drawing ** In the manufacture of wire, pulling the metal through a die or series of dies for reduction of diameter to specified size.

Durometer ** A measurement used to denote the hardness of a substance (usually of thermosetting and thermoplastic materials).

Eccentricity ** A measure of the lack of coincidence of longitudinal axes of a circular cross-sectional wire and its surrounding circular cross-sectional insulation. It is expressed as the percentage ratio of the distance between wire and insulation centers to the difference between wire and insulation radii.

Elastic Deformation ** A change in a substance whereby it reverts to its original dimensions on release of an applied stress.

Elastomer ** A material that at room temperature returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress and release of the stress.

Electrolyte — A nonmetallic (liquid or solid) conductor that carries current by the movement of ions (instead of electrons) with the liberation of matter at the electrodes of an electrochemical cell.

Elongation ** The fractional increase in length of a material stressed in tension.

Embossing ** A means of marker identification by means of thermal indentation leaving raised lettering on the sheath material of cable.

Environmental Stress Cracking Resistance -The ability of a material to resist crack formation and crack propagation when subjected to stress within a contaminating environment.

Equalization Charge — The process of mixing the electrolyte in batteries by periodically overcharging the batteries for a short time. A continuation of normal battery charging, at a voltage level slightly higher than the normal end-of-charge voltage, in order to provide cell equalization within a battery.

Equilay Conductor ** (See Concentric-lay Conductor.)

Equilay conductor ** Conductor constructed with a central core surrounded by more than one layer of helically laid wires, all layers having a common length of lay, direction of lay being reversed successive layers.

Ethylene Propylene Rubber ** A synthetic rubber insulation based upon ethylene propylene hydrocarbon.

Extrusion ** The process of continuously forcing either a plastic or elastomer and a conductor or core through a die, thereby applying an insulation or jacket to the conductor or core.
Fatigue Resistance ** The ability of a repeatedly deformed material to resist crystallization and accompanying failure.

Fault Current ** The maximum electrical current that will flow in a short-circuited system prior to the actuation of any current-limiting device. It is far in excess of normal current flow and is limited only by a system's generating capacity and a cable's impedence.

Fibrous Filler ** A material used to fill interstices in cables made from fibers, such as jute, polypropylene, cotton, glass, etc.

Filler ** Any material used in multiconductor cables to occupy interstices between insulated conductors or form a core into a desired shape (usually circular). Also, any substance, often inert, added to a plastic or elastomer to improve its properties or decrease its cost.

Film ** Thin, plastic sheeting having nominal thickness usually not greater than 0.010 inch.

Flame Resistance ** The ability of a burning material to extinguish its own flame, once its flame-initiating heat source is removed.

Flame Retardance ** Ability of a material to prevent the spread of combustion by a low rate of travel so the flame will not be conveyed.

Flex Life ** The number of bends or twists, of specified type, that a cable will withstand before failure.

Flexing Test ** Any test to determine the ability of a cable to withstand repeated bending and twisting.

Float Charge — The voltage required to counteract the self-discharge of the battery at a certain temperature.

Gassing Current — The portion of charge current that goes into electrolytical production of hydrogen and oxygen from the electrolytic liquid. This current increases with increasing voltage and temperature.

Gel-Type Battery — Lead-acid battery in which the electrolyte is composed of a silica gel matrix.

Ground ** A conducting connection, intentional or accidental, between an electric circuit or equipment and the earth or some conducting body serving in place of the earth.

Ground Potential ** Zero potential with respect to the ground or earth.

Grounded Neutral ** A circuit operates with grounded neutral when the neutral is metallically connected to ground and there is a provision for immediate removal of a faulted element.

Grounding Conductor ** A conductor used to connect equipment or the grounded circuit of a wiring system to a grounding electrode or electrodes; usually colored green.

Hard-drawn Wire ** As applied to aluminum and copper, wire that has been cold drawn to final size so as to approach the maximum strength obtainable.

Heat Endurance ** The time of heat aging that a material can withstand before failing a specific physical or electrical test.

Heat Resistance ** Ability of a substance to maintain physical and chemical identity and chemical identity and electrical integrity under specified temperature conditions.

Heat Shock ** A test to determine stability of a material by sudden exposure to a high temperature for a short period of time.

Helix ** A spiral winding.

Hertz ** (Abbr. H) A term rapidly replacing cycles-per-second as an indication of frequency.

High Voltage Time Test ** A high-voltage time test is an accelerated life test on a cable sample in which voltage is the factor increased.

Hygroscopic ** Attracting or absorbing moisture from the ambient atmosphere.

Hypalon ** Du Pont trademark for chlorosulfonated polyethylene (CSPE) synthetic rubber.

ICEA ** Insulated Cable Engineers Association (Formerly lPCEA). An Association of Engineers of most cable manufacturers.

Inverter — A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid.
Inverter,  Pulse-Width-Modulated (PWM) Wave — A type of power inverter that produce a high quality (nearly sinusoidal) voltage, at minimum current harmonics.

Inverter, - Grid Tie or  Line-Commutated — An inverter that is tied to a power grid or line. The commutation of power (conversion from direct current to alternating current) is controlled by the power line, so that, if there is a failure in the power grid, the photovoltaic system cannot feed power into the line.

Inverter, Utility-Interactive— An inverter that can function only when tied to the utility grid, and uses the prevailing line-voltage frequency on the utility line as a control parameter to ensure that the photovoltaic system's output is fully synchronized with the utility power.

Irradiation ** The exposure of a material to high energy emissions. In insulations for the purpose of favorably altering the molecular structure. Excessive exposure can be detrimental to the physical and electrical properties.
Jacket ** A material covering over a wire insulation or an assembly of components, usually an extruded plastic or elastomer.

Jumper ** A short length of conductor used to make a connection between terminals, around a break in a circuit, or around an instrument.

Kilowatt (kW) — A standard unit of electrical power equal to 1000 watts, or to the energy consumption at a rate of 1000 joules per second.

Kilowatt-Hour (kWh) — 1,000 thousand watts acting over a period of 1 hour. The kWh is a unit of energy. 1 kWh=3600 kJ.

Lap Splice ** A permanent joint formed in a short overlapping region of two parallel conductors or tapes. Also called parallel splice.

Lay ** The distance along a cable occupied by one complete helix of a strand or conductor. The direction of lay (left or right hand) is the direction of the helix looking away from an observer. Also to arrange the wires or members of a conductor either by twisting them or by forming them into one or more layers helically applied.

Lead-Acid Battery — A general category that includes batteries with plates made of pure lead, lead-antimony, or lead-calcium immersed in an acid electrolyte.

Length of Lay ** The axial length of one turn of the helix of a wire or member.
Line-commutated Inverter - Grid tie inverters use the grid to set frequency.

Liquid Electrolyte Battery — A battery containing a liquid solution of acid and water. Distilled water may be added to these batteries to replenish the electrolyte as necessary. Also called a flooded battery because the plates are covered with the electrolyte.

Maintenance-Free Battery — A sealed battery to which water cannot be added to maintain electrolyte level.

Marker Tape ** A narrow strip of fabric, paper or plastic laid longitudinally within a cable; it bears printed information such as the specification to which the cable was made and the name of the cable's manufacturer.

Marker Threads ** Colored strings laid parallel and adjacent to the strands of an insulated conductor to reveal information such as the conductor's manufacturer, the specification to which it was made, or its thermal capability.

Maximum Power Point Tracking (MPPT) - is system that uses a control algorithm to keep the PV modules operating close to their peak power point while the incoming power level varies.

Messenger Wire ** A metallic supporting member either solid or stranded which may also perform the function of a conductor.

Migration ** The loss of plasticizer from a plastic, usually due to heat or aging. It is undesirable since it will make the plastic hard and brittle. It is also called leaching.

Mil ** Unit of measure equal to 1/1000 of an inch.

Mining Cable ** A flame retardant cable especially constructed to withstand rough handling and exposure to moisture for underground use in the environment of a mine or tunnel, or surface use where exposed to sunlight and extremes of temperature.
Module Integrated Inverter (MIC) - are tiny inverters designed for use with a single large module.

Moisture Absorption ** The amount of water that an insulation or jacket, which is initially dry, will absorb under specified conditions. It is expressed as the percentage ration of the absorbed water's weight to the weight of the jacket or insulation alone.

Multi-string inverter - is a recent development. This is where one inverter unit has multiple MPPT and DC-DC converter units each connected to a string of modules. Shading and mismatch losses are again reduced but only one inverter is required.

NEMA Standards ** Property values adopted as standard by the National Electrical Manufacturers Association.

Neoprene ** Trade name for polychloroprene, used for jacketing (See Polychloroprene).
Nickel Cadmium Battery — A battery containing nickel and cadmium plates and an alkaline electrolyte.

Nitrile Rubber ** A rubbery copolymer of butadiene and acrylonitrile. It is usually compounded and vulcanized.

Nominal ** Name or identifying value of a measurable property by which a conductor or component or property of a conductor is identified, and to which tolerances are applied.

Nominal Voltage — A reference voltage used to describe batteries, modules, or systems (i.e., a 12-volt or 24-volt battery, module, or system).

Nominal Voltage — A reference voltage used to describe batteries, modules, or systems (i.e., a 12-volt or 24-volt battery, module, or system).

Nordel ** Du Pont trademark for EPDM synthetic rubber.

Ohm — A measure of the electrical resistance of a material equal to the resistance of a circuit in which the potential difference of 1 volt produces a current of 1 ampere.

Overcharge — Forcing current into a fully charged battery. The battery will be damaged if overcharged for a long period.

Oxygen Bomb Test ** A test to determine the ability of conductors and insulations to withstand physical and electrical change when immersed in pure oxygen gas of specified temperature and pressure for a specified time.

Plastic ** Any solid material employing organic matter of a high molecular weight as a principal constituent, which can be shaped by heat and pressure during manufacturing or processing into a finished article.

Plasticizer ** A substance incorporated into a material to increase its workability or flexibility.

Plates — A metal plate, usually lead or lead compound, immersed in the electrolyte in a battery.

Plating ** Any thin metallic coating applied over a metallic substratum.

Polychloroprene ** Chemical name for neoprene. A rubber-like compound used for jacketing where wire and cable will be subject to rough usage, moisture, oil, greases, solvents and chemicals.

Polyester ** A resin generally used as a thin film in tape form.

Polyethylene ** A thermoplastic material composed of polymers of ethylene.

Polymer ** A material formed by the chemical combination of monomers having either the same or different chemical composition.

Polypropylene ** A thermoplastic polymer of propylene.

Polyvinyl Chloride (PVC) ** A thermoplastic material composed of polymers of vinyl chloride, which may be rigid or elastomeric, depending on specific formulation.

Pothead ** An insulator used in making a sealed joint between an underground cable and an overhead line.

Potting ** Applying a hydrostatic seal and mechanical reinforcement by means of a thermosetting liquid, which cures either at room temperature or at a slightly elevated temperature.

Power Conversion Efficiency — The ratio of output power to input power of the inverter.

Power Factor (PF) — The ratio of actual power being used in a circuit, expressed in watts or kilowatts, to the power that is apparently being drawn from a power source, expressed in volt-amperes or kilovolt-amperes.

Pulse Width Modulation - is used to generate a waveform as close as possible to a sine wave. Pulses of different voltages are generated and the width of the pulse is modified so that the resulting wave is as close as possible to a sinusoidal wave form

Quad ** A structural unit employed in cables, consisting of four separately insulated conductors twisted together.

Rated Battery Capacity — The term used by battery manufacturers to indicate the maximum amount of energy that can be withdrawn from a battery under specified discharge rate and temperature. See battery capacity.

Rated Module Current (A) — The current output of a photovoltaic module measured at standard test conditions of 1,000 w/m2 and 25�C cell temperature.

Rectifier — A device that converts alternating current to direct current. See inverter. Rated Power — Rated power of the inverter. However, some units can not produce rated power continuously. See duty rating.

Regulator — Prevents overcharging of batteries by controlling charge cycle-usually adjustable to conform to specific battery needs.Rectifier — A device that converts alternating current to direct current. See inverter. Rated Power — Rated power of the inverter. However, some units can not produce rated power continuously. See duty rating.

Resistance ** Property of a conductor that opposed the current flow produced by a given difference of potential. The ohm is the practical unit of resistance.

Reverse Current Protection — Any method of preventing unwanted current flow from the battery to the photovoltaic array (usually at night). See blocking diode.

Rope-lay Conductor ** (See Concentric-lay Conductor.)

Rope-lay conductor ** Conductor constructed of a bunch-stranded or a concentric-stranded member or members, as a central core, around which are laid one or more helical layers of such members.

Rubber ** A material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent.

Rupture ** In the breaking strength or tensile strength tests the point at which a material physically comes apart as opposed to yield strength, elongation, etc.
Screen ** (See Shield.)

Secondary Insulation ** Any extremely high resistance material which is placed over primary insulation to protect it from abrasion.

Self Commutated - Most modern inverters are self-commutated,  they set their own frequency rather than relying on the grid to provide the frequency as a line-commutated inverter does.
Semi-conductor ** A solid material characterized by comparatively high resistivities.

Series Connection— A way of joining battery or photovoltaic cells by  connecting positive leads to negative leads; such a configuration increases the voltage.
Serve ** Any helical wrapping applied over a wire or cable core. It may consist of wires, fibers, yarns or tapes.

Served Wire Shield ** A barrier to the passage of interference formed by a helical wrapping of wires over a cable core. It is also called spiral shield.
Sheath ** The material, usually an extruded plastic or elastomer, applied outermost to a wire or cable. Very often referred to as a jacket, or an impervious metal covering usually lead.

Shield ** Any barrier to the passage of interference causing electrostatic or electromagnetic fields, formed by a conductive layer surrounding a cable core. It is usually fabricated from a metallic braid, foil or wire serving.

Shield Coverage ** The amount of cable core surface area which is covered by a shield. It is expressed as a percentage of the cable core's total surface area. It is also called braid coverage when applied to a braided shield.

Shielding ** The practice of confining the electrical field around a conductor to the primary insulation of the cable by putting a conducting layer over and/or under the insulation. (External shielding is a conducting layer on the outside of the insulation. Strand or internal shielding is a conducting layer over the conductor itself).

Short-Circuit Current (Isc) — The current flowing freely through an external circuit that has no load or resistance; the maximum current possible.

Shunt Controller — A charge controller that redirects or shunts the charging current away from the battery. The controller requires a large heat sink to dissipate the current from the short-circuited photovoltaic array. Most shunt controllers are for smaller systems producing 30 amperes or less.

Shunt Regulator — Type of a battery charge regulator where the charging current is controlled by a switch connected in parallel with the photovoltaic (PV) generator. Shorting the PV generator prevents overcharging of the battery.

Single-Stage Controller — A charge controller that redirects all charging current as the battery nears full state-of-charge.

Skeleton Braid ** A braid of widely separated wires or fibers, used to reinforce a jacket, bind a cable core, or prevent the passage of electrostatic or electromagnetic fields.

Soft Wire ** Wire that has been drawn or rolled to final size and then heated to remove the effects of cold working.

Spark Test ** A test designed to locate pin-holes in an insulated wire by application of an electrical potential across the material for a very short period of time while the wire is drawn through an electrode field.

Specific Dielectric Strength ** The dielectric strength per millimeter of thickness of an insulating material.

Specific Gravity ** The density (mass per unit volume) of any material divided by that of water at a standard temperature.

Specific Inductance Capacitance ** That property of a dielectric material which determines how much electrostatic energy can be stored per unit volume when unit voltage is applied.

Specific Resistance ** The resistance of a unit conductor having a length of one foot and across-sectional area of one circular mil.

Spiral Wrap ** A term given to describe the helical wrap of a tape or thread over a core.

Splice ** A joint used for connecting two lengths of conductor or cable with good mechanical strength as well as good conductivity.

Square Wave — A waveform that has only two states, (i.e., positive or negative). A square wave contains a large number of harmonics.

Square Wave Inverter — A type of inverter that produces square wave output. It consists of a direct current source, four switches, and the load. The switches are power semiconductors that can carry a large current and withstand a high voltage rating. The switches are turned on and off at a correct sequence, at a certain frequency.

Stabilizer ** Any ingredient added to plastics to preserve their physical and chemical properties.

Standby Current — This is the amount of current (power) used by the inverter when no load is active (lost power). The efficiency of the inverter is lowest when the load demand is low.

Static ** Electrical discharges in the atmosphere such as lightning, corona, etc.
Strand ** One of the wires of any stranded conductor.

Strand Lay ** The distance of advance of one strand of a spirally stranded conductor, in one turn, measured axially.

Stranded Conductor ** A conductor composed of a group of wires, usually twisted, or of any combination of such groups of wires.

Stress Cone ** A conical section built up of insulating tapes or a pennant to relieve the stress at the terminal end of the cable.

String inverters - is where a number of inverters are used, each receiving input from a single string of modules. This concept introduced by SMA with their Sunnyboy range and string inverters quickly came to dominate the market for domestic scale PV systems

Surge Capacity — The maximum power, usually 3-5 times the rated power, that can be provided over a short time.

System Operating Voltage — The photovoltaic array output voltage under load. The system operating voltage is dependent on the load or batteries connected to the output terminals.

Tank Test ** A voltage dielectric test where the specimen to be tested is submerged in a liquid (usually water) and a voltage potential applied between the conductor and the liquid as ground.

Tape Wrap ** A term denoting a spirally or longitudinally applied tape material wrapped around the wire, either insulated or uninsulated, used as an insulation or mechanical barrier.

Tare Loss — Loss caused by a charge controller. One minus tare loss, expressed as a percentage, is equal to the controller efficiency.

Tear Strength ** The force required to initiate or continue a rip in a jacket or other insulation under specified conditions.

Temperature Compensation — A circuit that adjusts the charge controller activation points depending on battery temperature. This feature is recommended if the battery temperature is expected to vary more than ±5°C from ambient temperature.

Temperature Rating ** The maximum temperature at which a given insulation or jacket may be safely maintained during continuous use, without incurring any thermally-induced deterioration.

Tensile Strength ** The longitudinal stress required to break a specimen of prescribed dimension divided by the original cross-sectional area at the point of rupture (usually expressed in pounds per square inch).

Termination ** 1). The load connected to the output end of a transmission line. 2). The provisions for ending a transmission line and connecting to a bus bar or other terminating device.

Thermal Conductivity ** Ability of material to conduct heat.

Thermal Endurance ** The time in hours at a selected temperature for an insulating material or system of material or system of materials to deteriorate to some predetermined level of electrical, mechanical, or chemical performance under prescribed conditions of test.

Thermal Expansion (Coefficient of) ** The fractional change in length (sometimes volume) of a material for a unit change in temperature.

Thermal Rating ** The maximum and/or minimum temperature at which a material will perform its function without undue degradation.

Thermoplastic ** A classification of resin that can be readily softened and reformed by heating and be rehardened by cooling.

Thermoset ** 1). To cure through chemical reaction by heat to a point of not being resoftened by subsequent heating. 2). A resin which cures by chemical reaction.

Tinned Wire ** Copper wire that has been coated during manufacture with a layer of tin or solder to prevent corrosion or facilitate soldering.

Tolerance ** A specified allowance for error from a standard or given dimension, weight or property.

Total AC Load Demand — The sum of the alternating current loads. This value is important when selecting an inverter.

TPR ** A trade name of Uniroyal Inc. for their thermoplastic rubber.

Triad ** Any grouping of three conductors or three assemblages of conductors, generally twisted together and found within a cable.

Triplex ** Three single conductors twisted together, usually three single conductor cables twisted without over-all covering. Do not use for three conductors laid parallel on a reel.

Ultra Violet Degradation ** The degradation caused by long time exposure of a material to sunlight or other ultraviolet rays containing radiation.

Unidirectional Conductor ** (See Concentriclay Conductor.)

Unidirectional conductor ** Conductor constructed with a central core surrounded by more than one layer of helically laid wire, all layers having a common direction of lay, with increase in length of lay for each successive layer.

Unilay Conductor ** (See Concentric-lay Conductor.)

conductor ** conductor constructed with a central core surrounded by more than one layer of helically laid wires, all layers having a common length and direction of lay.

Varistor — A voltage-dependent variable resistor. Normally used to protect sensitive equipment from power spikes or lightning strikes by shunting the energy to ground.

Volt (V) — A unit of electrical force equal to that amount of electromotive force that will cause a steady current of one ampere to flow through a resistance of one ohm.

Volt ** Unit of electromotive force. It is the difference of potential required to make a current of one ampere flow through resistance of one ohm.

Voltage — The amount of electromotive force, measured in volts, that exists between two points.

Voltage Disconnect — HIGH -  The voltage at which a charge controller will disconnect the load from the batteries to prevent over-discharging.

Voltage Disconnect —Low - The voltage at which a charge controller will disconnect the photovoltaic array from the batteries to prevent overcharging.

Voltage Drop ** The voltage developed between the terminals of a circuit component by the flow of current through the resistance or impedance of that part.

Voltage Rating ** The maximum voltage at which a given cable or insulated conductor may be safely maintained during continuous use in a normal manner. It is also called working voltage.

Vulcanization ** An irreversible process during which a rubber compound through a change in its chemical structure (for example, cross-linking), becomes less plastic and more resistant to swelling by organic liquids and elastic properties are conferred, improved, or extended over a greater range of temperature.

Water Absorption ** The ratio of the weight of water absorbed by a given material under specified conditions, to the weight of that material when dry. It is generally expressed as a percentage.

Watt - is a measure of power.  Volts multiplied by Amps = Watts

Watt — The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals 1/746 horsepower, or one joule per second. It is the product of voltage and current (amperage).

Watt-hour - is a unit of energy, electrical energy, equal to the work done by one watt acting for one hour.

Waveform — The shape of the phase power at a certain frequency and amplitude.

Wicking ** The longitudinal flow of a liquid in a wire or cable construction due to capillary action.

Wire Gage ** Any of several standard systems for designating wire sizes. As an example, see American Wire Gage.

Work Hardening ** The increased stiffness and brittleness accompanying plastic deformation of metal.

Yield Strength ** The lowest stress at which a material undergoes plastic deformation. Below this stress, the material is elastic; above it, viscous.