US3522366A - Electrical insulators - Google Patents

Electrical insulators Download PDF

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Publication number
US3522366A
US3522366A US811764A US3522366DA US3522366A US 3522366 A US3522366 A US 3522366A US 811764 A US811764 A US 811764A US 3522366D A US3522366D A US 3522366DA US 3522366 A US3522366 A US 3522366A
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United States
Prior art keywords
shed
insulator
sheds
size
length
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US811764A
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English (en)
Inventor
Peter John Lambeth
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Transmission Developments Ltd
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Transmission Developments Ltd
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Filing date
Publication date
Priority claimed from GB6046768A external-priority patent/GB1263465A/en
Application filed by Transmission Developments Ltd filed Critical Transmission Developments Ltd
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Publication of US3522366A publication Critical patent/US3522366A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B17/00—Insulators or insulating bodies characterised by their form
    • H01B17/42—Means for obtaining improved distribution of voltage; Protection against arc discharges

Definitions

  • the length of the creepage path L between the lowest point on the rim of any shed and the point immediately below it on the next shed of the same or larger diameter is related to the shortest distance X between the two points in such a way that the maximum value of X/L does not exceed the minimum value by more than 50% and the total creepage path between the ends of the insulating material is at least 4 times and typically 10 times the axial length.
  • This invention relates to shedding electrical insulators for high voltages and is directed more particularly but not exclusively to rod-type insulators for suspending the conductors of overhead power transmission lines.
  • an electrical insulator has a plurality of sheds with adjacent sheds of different diameters along the whole or at least the greater part of the length of the insulator, the total length of the creepage path between the ends of the insulating material being at least 4 times and preferably at least 8 times the axial length of the insulating material.
  • the creepage path length is the most important single parameter used in determining the performance of a polluated insulator, provided that the design is such as to permit effective utilisation of the creepage path (that is to say the risk of shorting out substantial sections of creepage by water droplets and/ or air discharges between sheds is minimised) it is preferred to adopt a high ratio of about 10 for the total length of the creepage path to the axial length of the insulation of a rod type insulator.
  • the length of the creepage path (L) between the lowest point on the rim of any shed and the point immediately below it on the next shed of the same or larger diameter, when the axis of the insulator is vertical is related to the shortest distance (X) between the two points, in such a way that the maximum value of X /L for any two such points on the insulator or on a major part of the length of the insulator shall not exceed the minimum value of X/L by more than 50%.
  • the larger and smaller diameter sheds are arranged alternately. If there are more than two shed sizes they are preferably arranged in a repeating pattern. This pattern is preferably such that if there are N different shed sizes then the pattern will be repeated after 2 sheds, and the order in which the sheds are arranged is determined by the following procedure:
  • the sheds be size 0, size 1, size 2 Size (N-l) where the shed diameters increase (as but not necessarily in proportion with) the size numbers, and let the position of the sheds in a set be position 1, position 2 position 2 where position 1 is the lowermost shed of the set; then the shed size number is given by the highest power of 2 that is exactly divisible into the position number.
  • the size number is 0 for positions 2 and 6 the size number is 1, for position 4 the size number is 2 and for position 8 the size number is 3.
  • N may be equal to 2 we prefer to make it or more, so that the pattern repeats after a minimum of four sheds.
  • a complete insulator will normally include a number of repeating patterns of sheds as described above.
  • the uppermost shed of the insulator is preferably of the largest size (i.e. the pattern sequence is completed at the top), but the lowest shed need not necessarily complete a pattern.
  • the shed diameters are preferably so chosen that drips from the rim of any shed, whether or not affected by electrical stress and/or wind or deflection of the insulator from the vertical when in normal use will not regularly fall onto the smaller shed below it. This will be effectively achieved by ensuring that a line drawn touching the outer extremity of a larger shed at an angle of 30 to the axis of the insulator does not intercept one of the smaller sheds beneath it before intercepting a shed of the same or larger size.
  • the shortest distance between the lowest part of any shed when the insulator is vertical (upright) and the surface of any other shed is preferably not less than 8 mm.
  • a line joining a point on any shed furthest from the insulator axis and the midpoint of the shed root where it meets the insulator stem in the same plane as the first point and the insulator axis should preferably but not essentially make an angle of between 50 and 65 with the axis of the insulator. For any single insulator the angle of each shed will usually be substantially the same.
  • the sheds are preferably of thin walled conical shape with their upper and lower surfaces each generated by rotation about the insulator axis of a substantially straight line passing through the axis.
  • the sheds may be of generally conical form with upper and lower surfaces generated by the rotation of smoothly curved generator lines of a shape such that the maximum deviation from a straight line is not greater than the average thickness of the shed.
  • the upper or lower surface of a shed, or both may he stepped or corrugated, provided that the maximum depth of any step or corrugation does not exceed 40% of the average thickness of the shed.
  • Each shed may be of substantially uniform thickness throughout or tapering with a taper angle up to 15.
  • the preferred conical shape of the sheds described has the advantage that, if the insulator is to be greased with a hydrocarbon or other grease, the grease is easily applied by spraying and easily removed by a simple scraper.
  • the invention may be applied to a porcelain insulator with end caps.
  • the body of the insulator may be formed integrally with the sheds as a single porcelain element, end caps being secured to the ends of the porcelain element in the known way.
  • the invention however may equally be applied to rod type insulators constructed in other ways for example formed from a plurality of units assembled together, e.g. moulded resin insulators on a resin-bonded glass-fibre core. This type of material permits of a high ratio of shed overhang to thickness, as is required if more than two diameters of shed are used.
  • FIG. 1 is a side elevation, partly in section, of a rodtype insulator
  • FIG. 2 is a side elevation, partly in section, of another construction of insulator.
  • FIG. 3 is a view similar to FIG. 2 of a slightly different construction of insulator.
  • FIG. 1 there is shown a rod-type insulator for suspending a conductor for an E.H.V. overhead transmission line.
  • the insulator has a main body portion formed of porcelain and having integral sheds which are alternately of larger and smaller diameter.
  • the insulator has fourteen larger diameter sheds 11 and thirteen smaller diameter sheds 12.
  • Each shed is formed with a concave or conical undersurface and a generally convex upper surface, these surfaces merging smoothly into the main body portion of the insulator, the upper and lower shed surfaces both sloping downwardly and outwardly so that rain tends to run off the sheds or forming droplets collecting at the lowest point part on a shed, which part is at or near the outer periphery.
  • the ends of the insulator are secured in metal end caps 13, 14 in the known way.
  • FIG. 2 illustrates part of a moulded resin insulator.
  • the insulator is conveniently moulded from a synthetic resin and may be secured around a resin-bonded glassfibre core.
  • the moulding is preferably carried out by vacuum casting using an epoxy resin. Because of the high vantage of such an arrangement over that with two shed sizes is that, for a given overall diameter the ratio of creepage paths to gap widths can be increased, and the pollution performance of the insulator improved.
  • FIG. 2 there are shown two of the largest size sheds, 20, 21, one intermediate size shed 22 and two of the smallest sheds 23, 24.
  • the gap widths are shown as the dimension X between sheds 20, 21, the dimension X between sheds 22 and 21, the dimension X between sheds 23 and 22 and the dimension X between sheds 24 and 21.
  • Associated with the gaps X, X, X" and X are creepage path lengths L, L, L" and L respectively, these creepage path lengths being the shortest lengths (in a radial plane through the axis of the insulator) along the surface of the sheds between the two ends of the respective gaps.
  • the values of X/L X/ L" etc. vary from 0.0758 to 0.0936, the shed taper is 5,
  • the shed angle is 63, and the ratio of the length of creepage path to the length of the insulation of the insulator is 10.
  • FIG. 3 which illustrates a modification of the insulator of FIG. 2, the corresponding values are 0.103 to 0.136, 5, 63 and 6.9.
  • N 3 and consequently the pattern repeats every four sheds.
  • the shortest distance between the lowest part of any shed when the insulator is vertical (upright) and the surface of any other shed is made greater than 8 mm.
  • An electrical insulator having a plurality of sheds along at least the greater part of the length of the insulator, the sheds being of N different diameters, N being a whole number equal to or greater than 3, the shed sizes being of size 0, size 1, size 2 size (N1), the shed diameters increasing in the order of the size numbers, and the sheds being arranged in a repeating pattern with 2 sheds in each set of the repeating pattern, the positioning of the sheds in the pattern being defined as position 1, position 2 position 2 in numerical order upwards from the lowest shed and wherein the shed size number is given by the highest power of 2 that is exactly divisible into the position number, the total length of the creepage path between the ends of the insulating material being at least 4 times the axial length of the insulating material.
  • An electrical insulator having a plurality of sheds along at least the greater part of the length of the insulator, the sheds being of N different diameters, N being equal to or greater than 3, the sheds of different sizes being arranged in a repeating pattern of 2(Nr1) sheds in each set of the pattern, the shed sizes being of size 0, size 1, size 2 size (N-l), the shed diameters increasing in the order of the size numbers, and the positioning of the sheds in the pattern being defined as position 1, position 2 position 2 in numerical order upwards from the lowest shed and wherein the shed size number for each position in a set is given by the highest power of 2 that is exactly divisible into the position number and wherein the length of the creepage path L between the lowest point on the rim of any shed and the point immediately below it on the next shed of the same or larger diameter, when the axis of the insulator is vertical, is related to the shortest distance (X) between the two points in such a Way that the maximum value of X/L for any two such points on the insulation or

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Insulators (AREA)
US811764A 1968-04-01 1969-04-01 Electrical insulators Expired - Lifetime US3522366A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1557668 1968-04-01
GB6046768A GB1263465A (en) 1968-04-01 1968-04-01 Improvements in or relating to electrical insulators

Publications (1)

Publication Number Publication Date
US3522366A true US3522366A (en) 1970-07-28

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Application Number Title Priority Date Filing Date
US811764A Expired - Lifetime US3522366A (en) 1968-04-01 1969-04-01 Electrical insulators

Country Status (4)

Country Link
US (1) US3522366A (enrdf_load_stackoverflow)
CH (1) CH499182A (enrdf_load_stackoverflow)
DE (1) DE1916767A1 (enrdf_load_stackoverflow)
FR (1) FR2005296A1 (enrdf_load_stackoverflow)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4174464A (en) * 1977-04-28 1979-11-13 Ngk Insulators, Ltd. Rod-type insulator having improved withstand voltage characteristics under a contaminated condition
US4833278A (en) * 1988-10-31 1989-05-23 Hyrdro-Quebec Insulator housing made from polymeric materials and having spirally arranged inner sheds and water sheds
US20030231097A1 (en) * 2002-06-16 2003-12-18 Victor Almgren Composite insulator for fuse cutout
US20040001298A1 (en) * 2002-06-16 2004-01-01 Scott Henricks Composite insulator
US20040187433A1 (en) * 2000-12-26 2004-09-30 Barker James W. Method and arrangement for providing a gas-tight housing joint
US7028998B2 (en) 2001-04-30 2006-04-18 Maclean-Fogg Company Stabilizer bar
US20090153286A1 (en) * 2007-12-14 2009-06-18 Maclean-Fogg Company Insulator for cutout switch and fuse assembly

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2374729A1 (fr) * 1976-12-17 1978-07-13 Villamos Ipari Kutato Intezet Isolateur en matiere synthetique, procede pour sa fabrication et appareil pour la mise en oeuvre du procede
US4572357A (en) * 1984-01-26 1986-02-25 Gerber Garment Technology, Inc. Sheet material conveyor with unloading apparatus
DE3713588A1 (de) * 1987-04-23 1988-11-03 Bayer Ag Dosiergeraet
DE8915286U1 (de) * 1989-12-30 1990-03-29 NIKO Nahrungsmittel-Maschinen GmbH & Co KG, 41334 Nettetal Steilförderer für Gemüse, Obst u.dgl.
DE4319418A1 (de) * 1993-06-11 1994-12-15 Helmut Kingler Vorrichtung zum Aufsammeln von rollbaren Gegenständen
AT507991B1 (de) * 2009-03-06 2012-01-15 Kuvag Kunststoffverarbeitungs Ges M B H Abspannisolator

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1768948A (en) * 1921-12-03 1930-07-01 Westinghouse Electric & Mfg Co High-voltage insulator
FR871851A (fr) * 1939-08-15 1942-05-20 Brown Isolateurs rigides à fût allongé protégés contre l'encrassement
GB940400A (en) * 1961-06-06 1963-10-30 Central Electr Generat Board Improvements in or relating to electrical insulators
GB978501A (en) * 1962-11-08 1964-12-23 Siemens Ag An electrical insulator
GB1010362A (en) * 1961-08-01 1965-11-17 English Electric Co Ltd Improvements in or relating to shedded electrical insulators

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1768948A (en) * 1921-12-03 1930-07-01 Westinghouse Electric & Mfg Co High-voltage insulator
FR871851A (fr) * 1939-08-15 1942-05-20 Brown Isolateurs rigides à fût allongé protégés contre l'encrassement
GB940400A (en) * 1961-06-06 1963-10-30 Central Electr Generat Board Improvements in or relating to electrical insulators
GB1010362A (en) * 1961-08-01 1965-11-17 English Electric Co Ltd Improvements in or relating to shedded electrical insulators
GB978501A (en) * 1962-11-08 1964-12-23 Siemens Ag An electrical insulator

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4174464A (en) * 1977-04-28 1979-11-13 Ngk Insulators, Ltd. Rod-type insulator having improved withstand voltage characteristics under a contaminated condition
US4833278A (en) * 1988-10-31 1989-05-23 Hyrdro-Quebec Insulator housing made from polymeric materials and having spirally arranged inner sheds and water sheds
US7180004B2 (en) 2000-12-26 2007-02-20 Maclean-Fogg Company Method and arrangement for providing a gas-tight joint
US20040187433A1 (en) * 2000-12-26 2004-09-30 Barker James W. Method and arrangement for providing a gas-tight housing joint
US7041913B2 (en) 2000-12-26 2006-05-09 Barker Jr James W Method and arrangement for providing a gas-tight housing joint
US7028998B2 (en) 2001-04-30 2006-04-18 Maclean-Fogg Company Stabilizer bar
US20040001298A1 (en) * 2002-06-16 2004-01-01 Scott Henricks Composite insulator
US6952154B2 (en) 2002-06-16 2005-10-04 Maclean-Fogg Company Composite insulator for fuse cutout
US6831232B2 (en) 2002-06-16 2004-12-14 Scott Henricks Composite insulator
US20030231097A1 (en) * 2002-06-16 2003-12-18 Victor Almgren Composite insulator for fuse cutout
US20090153286A1 (en) * 2007-12-14 2009-06-18 Maclean-Fogg Company Insulator for cutout switch and fuse assembly
US7646282B2 (en) 2007-12-14 2010-01-12 Jiri Pazdirek Insulator for cutout switch and fuse assembly
US20100102919A1 (en) * 2007-12-14 2010-04-29 Jiri Pazdirek Insulator for Cutout Switch and Fuse Assembly

Also Published As

Publication number Publication date
DE1916767A1 (de) 1969-10-16
FR2005296A1 (enrdf_load_stackoverflow) 1969-12-12
CH499182A (de) 1970-11-15

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