Coordination Of Insulation Research Articles

Co-ordination of Insulation and Spacing or Transmission Line Conductors

A SURVEY of practice on existing transmission systems shows, for the same operating voltage, wide variations in the insulation used. Also, wide variations occur in the spacing between conductors and from them to grounded members of the supporting structure.

Co-ordination of insulation and spacing of transmission line conductors

A SURVEY of practice on existing transmission systems shows, for the same operating voltage, wide variations in the insulation used. Also, wide variations occur in the spacing between conductors and from them to grounded members of the supporting structure.

Insulation stresses in transformers, with special reference to surges and electrostatic shielding

The paper discusses various types of abnormal voltagestresses in transformers, and in particular those due to surge phenomena. A brief resume of the theory of the effects of surge voltages on transformer windings is given, and a method of determining initial impulse-voltage distribution by means of a calculating board is explained. The principles of electrostatic shielding are considered and the application of a simple, economical and effective type of shield to commercial transformers is discussed. Illustrations of actual transformers fitted with such shields are given, and the efficacy of the shielding is demonstrated by means of cathode-ray oscillograms.An account is given of researches carried out by means of the recurrent-surge oscillograph, and results are compared with those obtained at high voltage, using a continuously evacuated cathode-ray oscillograph.In conclusion, reference is made to the problem of co-ordination of insulation, and the relative merits of various protective measures are briefly discussed.It is shown that a shielded-winding transformer, when properly co-ordinated with line protective devices, possesses a high degree of immunity from breakdown due to lightning or other transient voltages.

Lightning protection of 22-kv substations

This paper outlines laboratory and field tests with a surge generator and cathode-ray oscillograph which led to the co-ordination of insulation and lightning-arrester performance in substations on the 22-kv subtransmission system of the Duquesne Light Company.

Lightning Protection of 22-Kv Substations

This paper outlines laboratory and field tests with a surge generator and cathode-ray oscillograph which led to the co-ordination of insulation and lightning-arrester performance in substations on the 22-kv subtransmission system of the Duquesne Light Company. A basic level of 150 kv for station insulation was selected in 1932, and methods of obtaining this level are presented together with the operating record for five years. The index representing the station equipment faults in per cent of total system faults during thunderstorms has decreased 86 per cent following system-wide improvement programs modernizing insulation and arresters.

Coordination of Insulation

The general scheme of coordination is discussed. Average circuit insulation used in 1930 is shown. The relation that switching surges and arcing ground overvoltages bear on coordination is discussed giving the number and magnitude of such waves found in service. Levels of insulation in and around the station for outdoor and indoor apparatus are suggested. It is pointed out why a point gap offers the most reliable method of establishing the level for impulse testing of transformers. Also, reasons are given why bushings as made at present should not be used as the sole level for impulse testing. It is shown that on account of the similarity of the volt-time curves for insulations and sphere gaps for short impulse waves, the use of a sphere gap in parallel with a rod gap will give an added protection against direct strokes on or near the apparatus terminals. Also, various proposed schemes are shown to give protection to the transformer and against outages for both fast and slow waves. For potential and current transformers having voltage ratings differing from standard it is suggested that the coordination gaps be selected from the curve of gaps vs. rated circuit voltages. It is shown how an air gap of standardized construction can be used to advantage in expressing the impulse flashover of insulators and bushings. Curves are given showing the gap spacings that are the equivalent in flashover to suspension and pedestal insulators for the ?/5, 1/10 and 1 ?/40 positive and negative waves.

Impulse and Dynamic Flashover Studies of 26-Kv Wood Pole Transmission Construction

This paper presents the results of a series of laboratory tests made with a million volt surge generator and 60-cycle high-voltage testing equipment on unit pole transmission construction now in standard usage on a large 26-kv transmission system. Actual impulse curves are given for several types of straight span pole top construction. Basic values of impulse flashovers are presented which should facilitate coordination of impulse insulation between poles of any similar transmission lines, aid in applying protective gaps, and furnish a guide to the comparative impulse strength of both present and new types of construction. Defects in present design standards and possible improvements are discussed. An analysis of the factors governing the development of a power arc following impulse sparkover and corresponding experimental data showing the extent of occurrence of such arcs are presented. The paper concludes that reliance upon air or wood separations within the usual physical limits to prevent lightning outages will be unsatisfactory, and discusses the application of protective measures.

Coordination of insulation

COORDINATION of system insulation is the selection of insulation in proportion to the anticipated overvoltages as limited by a coordination gap. A review of the development of coordination during the past few years is presented briefly in this paper, as a basis for discussing the means at present used for obtaining coordination of system insulation together with the advantages and disadvantages of various schemes. The 2 classes of overvoltage which may appear on a system, namely, switching surges and arcing ground voltages in the first class, and lightning voltages in the second class, are considered in respect to the selection of the coordination gap. It is pointed out that it is not logical to have steps or levels of insulation within a station, but that a uniform level of at least 10 per cent above the strength of the gap seems logical.

The Coordination of Transformer Insulation with Line Insulation

The Coordination of Transformer Insulation with Line Insulation

Coordination of line and transformer insulation

The coordination of transformer insulation with line insulation recently has been discussed widely, and sentiment has changed gradually in favor of the use of an air-gap for purposes of coordination as against the practise of reducing the line insulation near the substation. Standards of dielectric strength and air-gap spacing in accordance with this trend are presented herewith.

The coordination of transformer insulation with line insulation

PUBLISHED in full in this issue of Electrical Engineering, p. 390–1.

Insulation coordination of distribution transformers

ASAN ALTERNATIVE to the use of distribution transformers of present levels of dielectric strength with lightning arresters connected either in the customary manner or having the primary lightning arrester ground interconnected with the grounded neutral of the transformer secondary main, a study of the coordination of insulation of distribution transformers has been carried out.

Coordination of Insulation as a Design Problem

The factors having influence on insulation design of transmission line and station are briefly reviewed, and it is pointed out that the progress of the art does not yet allow of close design of the insulation structure for insulation strength. The prominent part played by the lightning arrester is stressed, and the fact that it has a marked effect on the coordination of station insulation. Examples of a typical 110-kv. station where no coordination was made, and of a 220-kv. station where a deliberate coordination was attempted, are given, as well as the experience obtained with each.

Essential Factors in the Coordination of Line, Station and Apparatus Insulation

Generated, switching, and lightning surge voltages all influence the design and application of insulation. The first two might logically be taken as the bases for determining the minimum insulation levels at stations; also, for lines where lightning is not encountered. Since lightning voltages affect service primarily through their influence on lines, the insulation strengths suitable for the lines may bear little relation to the insulation strengths of the stations. Several lightning insulation levels are proposed for the coordination of line, station, and apparatus insulation; the basic or lowest level (determined by consideration of generated and switching surge voltages), being established by the line insulation or spillway gaps at the line station entrances, when the line is at a higher level; the busses and connections would constitute the next higher level; the apparatus bushings next; and finally, the apparatus internals. More complete data on the nature of transient voltages as they originate and are modified by the circuit, and the performance of insulation with these voltages applied, are required before insulation can be coordinated with assurance. During the interim it should be possible to accomplish substantial improvement to service by applying to specific cases as they arise, the knowledge and data already available and being gathered, along the general lines proposed in the paper.

Abridgment of the effect of transient voltages on dielectrics — IV: Law of impulse spark-over and time lag: Relative effects of different wave shapes — Comparison of lightning waves and laboratory waves — Coordination of line insulation

Abridgment of the effect of transient voltages on dielectrics — IV: Law of impulse spark-over and time lag: Relative effects of different wave shapes — Comparison of lightning waves and laboratory waves — Coordination of line insulation

Abridgment of essential factors in the coordination of line, station and apparatus insulation

Abridgment of essential factors in the coordination of line, station and apparatus insulation

Coordination of insulation as a design problem

The factors having influence on insulation design of transmission line and station are briefly reviewed, and it is pointed out that the progress of the art does not yet allow of close design of the insulation structure for insulation strength. The prominent part played by the lightning arrester is stressed, and the fact that it has a marked effect on the coordination of station insulation. Examples of a typical 110-kv. station where no coordination was made, and of a 220-kv. station where a deliberate coordination was attempted, are given, as well as the experience obtained with each.