Glossary - Power Grid

		Glossary of Terms

1	Composite Insulator	A composite insulator is made of at least two insulating parts - a core and a housing. It is equipped with end fittings. A composite insulator is a manufactured device intended to give flexible or rigid mechanical support to electric conductors or equipment while electrically separating these conductors or equipment from ground or from other conductors or equipment.
2	Cantilever Breaking Load (CBL)	The maximum load reached during destructive cantilever testing.
3	Coupling zone	The coupling zone is the part of the end fitting that transmits the load to the line
4	Critical Impulse Flashover Voltage	The critical impulse flashover voltage of an insulator is the crest value of the impulse wave that, under specified conditions, causes flashover through the surrounding medium on 50 % of the applications.
5	Dry-Arcing Distance	The dry-arcing distance of an insulator is the shortest distance through the surrounding medium between terminal electrodes with the insulator mounted for dry flashover tests.
6	End Fittings	End fitting transmit the mechanical load to the core
7	Erosion	Erosion is the loss of material from the insulating surface resulting in a nonconductive surface. It can be uni- form, localized, or tree-shaped. Shallow surface traces commonly tree-shaped can occur on composite insulators after arcing. These traces do not affect the operating characteristics of the insulator.
8	Impulse Flashover Voltage	The crest value of the impulse voltage that, under specified conditions, causes flashover of an insulator through the surrounding medium.
9	Impulse Wave	An impulse wave is a unidirectional surge generated by the release of electrical energy into an impedance network.
10	Impulse Withstand Voltage	The impulse withstand voltage of an insulator is the crest value of an applied impulse voltage that, under specified conditions, does not cause a flashover, puncture, or disruptive discharge on the test specimen.
11	Insulator Core	The core is the internal insulating part of a composite insulator. It is intended to carry the mechanical load. It consists mainly of glass fibers positioned in a resin matrix to develop mechanical strength.
12	Insulator Housing	The housing is external to the core and protects it from the weather, it may be equipped with weathersheds. Some designs of composite insulators employ a sheath made of insulating material between the weathersheds and the core. This sheath is part of the housing.
13	Leakage Distance	The leakage distance of an insulator is the shortest distance measured along the insulating surface between the conductive parts, as arranged for dry flashover tests.
14	Line and Apparatus Post Insulators	A post insulator is an insulator with attached metal parts having means for direct and rigid mounting to a supporting structure and for semi-rigidly supporting conductors.
15	Low-Frequency	Low frequency means any frequency between 15 and 100 hertz.
16	Low-Frequency Flashover Voltage	A low-frequency flashover of an insulator is the root-mean-square value of the low-frequency voltage that, under specified conditions, causes a sustained disruptive discharge through the surrounding medium.
17	Low-Frequency Withstand Voltage	A low-frequency withstand voltage of an insulator is the root-mean-square value of the low-frequency voltage that, under specified conditions, can be applied without causing flashover or puncture.
18	Radio-Influence Voltage³	The magnitude of high-frequency voltage (noise) generated by all sources of ionization measured near the mid-point of the AM radio band using prescribed circuits and under defined conditions
19	Reference Cantilever Load (RCL)	The RCL is a rating that is less than or equal to 50% of the SCL.
20	Routine Test Load (RTL)	The RTL is a rating equal to 50 % of the SML.
21	Specified Cantilever Load (SCL)	The SCL is a value that has to be verified during a cantilever load test. it forms the cantilever loading basis for selection of a composite insulator.
22	Specified Mechanical Load (SML)	The SML is a value that has to be verified during a tensile load test. It forms the tensile loading basis for selection of a composite insulator.
23	Specified Tensile Load (STL)	The tensile load that can be withstood by the insulator when tested in accordance with the test protocol described in clause 9.4. This value is considered to be equivalent to a one minute withstand. This value is specified by the manufacturer.
24	Suspension Insulator	A suspension insulator is an insulator with attached metal parts having means for non-rigidly supporting electric conductors.
25	Tracking	Tracking is the formation of electrically conducting paths starting and developing on the surface of an insulating material. These paths are conductive even under dry conditions. Tracking can occur on surfaces in contact with air and also on the interfaces between insulating materials.
26	Ultimate Mechanical Strength²	The ultimate mechanical strength of an insulator is the load at which any part of the insulator fails to perform its function of providing a mechanical support without regard to electrical failure.
27	Weathersheds	Weathersheds are insulating parts projecting from the housing or sheath that are intended to increase the leakage distance and to provide an interrupted path for water drainage.

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