GB2037492A - Burning Electrode for an Arcing Ring, and an Arcing Ring for High- tension Overhead Transmission Line Insulators - Google Patents

Abstract

A burning electrode for an arcing ring 2 for a high-tension insulator comprises a mounting strut 4 carrying an electrode head 5 held between ends of the ring consisting of a shell 6 containing a relatively infusible insert 15 exposed at the surface of the head to form the foot of any arc struck from the ring. End bore 16 fixes the arc. Two inserts (20,21) of different m.p. materials may be incorporated (Figs. 3, 4, not shown). A further construction is detailed w.r.t. Figs. 6-8 (not shown). Transverse passages in the head permit escape of plasma and inhibit damage of the ring ends. Materials are exemplified. Fabrication includes casting. <IMAGE>

Description

SPECIFICATION Burning Electrode for an Arcing Ring and an Arcing Ring for High-Tension Overhead Transmission Line Insulators The invention relates to a burning or sacrificial electrode for an open arcing ring and to arcing rings incorporating such electrodes.

The arc protection fittings of high-tension overhead transmission lines serve primarily, after the original task of field control along the insulator string, to protect the string against the destructive consequences of an arc produced by a flash-over.

The protective fittings for this purpose must enclose the cap of the voltage-carrying insulator side as closely as possible and guide any arc that occurs to a point as remote as possible from the insulator. Then the arc should remain stably on this point until it is quenched by the response of the line fuse.

In known arcing rings with unilateral feed and a burning electrode mounted on a strut and having head set between free ends of the ring the insulation between the electrode head and the ring ends is effected by means of insulating caps which are firmly fitted on to the ring ends. The electrode head and the strut, which both consist of metal, carry no insulation. As a rule in these arcing rings, after the lighting of an arc, the foot of the arc runs along the ring to the electrode head and remains stationary there. It is not impossible in this case, if the line fuse does not respond immediately, that a large part of the electrode head may burn away, whereby the protective fitting becomes useless and at least the strut carrying the electrode head has to be replaced.

From German Patent Specification No 973,288 an arc protection device for high-tension insulators has become known of which the burning electrodes pointing away from the insulator consist of a difficulty fusible material, especially electrode carbon or graphite, to reduce the burning away of the electrode. In this case it is disadvantageous that the burning electrode which is arranged perpendicularly on the ends of the annular arc protection device is not capable of adequately stabilising the arc which therefore begins to flicker and can destroy the insulator.

The present invention provides a burning or sacrificial electrode for an open arcing ring which electrode comprises a strut carrying at one end an electrode head adapted to lie between and engage the ends of the arcing ring when in use and having an end face for in use forming the foot of any arc struck to the electrode, which electrodehead comprises a shell containing an insert of high burning resistance material which is exposed.

at and lies flush with the said end face.

The invention includes an arcing ring for a high-tension overhead transmission line insulator comprising an open-ended electrically conductive ring having insulating end caps disposed on its open ends and, engaging the end caps, an electrode of the invention.

Preferably the electrode head includes a bore extending from the said end face into the insert to assist in fixing the foot of any arc struck when the electrode is in use.

Preferably one or more bores transverse to and communicating with the said bore are provided opening the exterior of the electrode shell.

The invention further concerns an arcing ring, a high-tension overhead transmission line insulator, having a pair of free ends covered by caps of insulating material between which ends lies an electrode head to serve as an arc foot, which head bears a mounting strut extending into the ring and has on the side opposite to the entry point of the strut an end bore which is in communication with at least one transverse passage which opens into a side face of the electrode head between the free ends of the arcing ring, and which ring bears a second metallic strut serving for securing the assembly to the insulator and which is adapted to be attached with the first mentioned strut to the insulator, wherein side faces of the electrode head are provided with C-shaped protruding beads which firmly and non-displacably accommodate the caps fitted on the rings ends and serve as support for the ends of the arcing ring.

The invention will be illustrated by the following description of specific embodiments shown in the accompanying drawings in which: Figure 1 shows a section on a radius of an arcing ring, Figure 2 shows a plan view in part section, of the example of embodiment according to Figure 1, Figure 3 shows an incomplete longitudinal section of an arcing ring provided with a second example of an electrode of the invention, Figure 4 shows a part section plan view of the embodiment according to Figure 3, Figure 5 shows a lateral elevation of an example of an arcing ring arranged on an insulator string, Figure 6 shows a ring according to Figure 5 in partial section plan view, Figure 7 shows a partial section plan view of a further example of an arcing ring, and Figure 8 shows a part section on an enlarged scale along the line VIll-VIll in Figure 6.

The protective fitting designated as a whole by 1 for an insulator carrying a high-tension overhead transmission line consists, as shown by Figure 1, of an arcing ring 2 of circular arc form, a burning electrode 3 and a carrier strut, not further illustrated.

The open arcing ring 2 has a C-shaped cross-.

sectional profile and consists for example of hotdip galvanised steel. If however as a result of unfavourable environmental influences, for example heavy air soiiing, increased demands have to be made of the corrosion resistance of the protective fitting, the arcing ring 2 may be produced from aluminium.

This ring carries, mechanically firmly and electrically conductively connected thereto in a known manner, at a point lying approximately diametrically opposite (Figure 2) the gap present between the free ends 2', a carrier strut (not shown) which is ordinarily made in a goose-neck form.

The burning electrode 3 consists, as shown by Figures 1 and 2, of a metallic strut 4 connected at an end 4' to an electrode head designated as a whole by 5. The one end (not shown) of the strut 4 is connected at the same position as the carrier strut to a connection plate of the insulator string.

The connection can be effected for example with the same screw with which the carrier strut is made fast.

The electrode head 5 has a metallic shell 6 consisting for example of aluminium, if as already described above an increased corrosion resistance is required. The basic body or shell 6, as shown especially by Figure 1, is of pear-shaped form viewed perpendicular to the longitudinal central plane A-A, in order to obtain an adequate material volume.

A bore 7 is provided in one end of the shell 6 to accommodate the end 4' of the strut and is welded therewith.

The bore 7 opens inside the shell into a coaxial bore 8 of larger diameter which then merges into a section 9 with frusto-conical internal peripheral surface. This section 9 of the bore is continued, likewise coaxially with the bore 7, in a bore 10 which opens to the outside 11 of the electrode head 5. As shown especially by Figure 2 the curvature of the outer side is adapted to or matches the curvature of the arcing ring 2.

The shell 6 has extension pieces 1 3 arranged one on each side symmetrically of the longitudinal central plane A-A which grasp over the free ends 2' of the arcing ring 2, which ends are provided with synthetic plastics caps 12. These ends are then electrically insulated from the shell 6. The C-form of the two extension pieces 13 also renders it possible to introduce the electrode head and thus the strut 4 from the exterior radially in between the two free ends 23 in order to make the protective fitting renovatable or replacable.

In accordance with the invention a metallic insert 1 5 is arranged in the shell 6, which insert in the embodiment shown is a turned part. The end face 1 5' of the insert 1 5, as shown in Figure 2, is exposed at the outer side 11 of the electrode head 5 and is flush therewith, the curvature of the end face 15' being adapted to the curvature of the outer side 11. The outer peripheral surfaces of the insert then correspond with the inner peripheral surfaces of the bores 8 and 10 and the frusto-conical section 9.

Since the shell can be produced by a casting process it is possible to insert the insert body into the casing mould and cast around it. It is however on the other hand also possible to press or screw the insert into the shell.

The insert 1 5 advantageously consists of a material having a substantially higher melting point than that of the shell 6. Steel in its various alloys, tungsten, graphite, etc., are especially suitable for this purpose, if for example the basic body consists of aluminium.

As shown by Figures 1 and 2 an end bore 1 6 penetrates the insert 1 5 along its whole length, while the mouth or opening of this bore, 16', lying in the outer side 11 is sharp-edged or defined with a very small radius. In that region of the insert which has the smallest external diameter there are arranged two diametrically arranged, equally sized, radially extending transverse bores 1 7. These are coaxially adjoined by bores 1 8 in the shell 6, the diameter of which bores is larger than that of the transverse bores 1 7.

After the lighting of an arc, its foot is driven towards the electrode head and there remains stationary on the insert 1 5 because the end bore 1 6 fixes the arc foot in known manner. The line fuse responding immediately after the occurrence of the arc then brings the latter to extinction.

In the case of a delayed response by the said fuse, the insert 15, as a result of its good refractory quality, advantageously prevents excessive electrode burning on the electrode head 5. This ensures that the burning electrode 3 no longer has to be replaced, which would signify a considerable cost factor for the energy supplying undertaking in each case, quite apart from the fact that the line would otherwise have to be switched off.

In Figures 3 and 4 a second example is illustrated. This differs from the form shown in Figures 1 and 2 in that the metallic shell 19 carries a cylindrical first insert 20 and a second insert 21 arranged perpendicularly thereto and formed as a tube section.

The shell 19, which consists for example of aluminium if the protective fitting must take account of increased corrosion resistance, has almost the same external contour as the shell 6.

The bore 22 arranged at the one end of the shell also serves to accommodate a strut end, as shown by Figure 3.

A bore 23 arranged in the shell 19 perpendicularly of the longitudinal central plane B-B (see Figure 4) carries the first insert 20 which consists of a metallic material, for example steel, the melting point of which lies considerably higher than that of the shell 1 9. Since this is produced for example by a casting process it is possible to insert the first insert 20 into the casting mould and then to cast around it.

The second insert 21, which is formed as a tube section and consists of a material such as graphite or tungsten the melting point of which lies considerably higher than that of the first insert 20, is arranged coaxially with the bore 22 in the longitudinal central plane B-B.

The second insert is exposed at the exterior of the shell 1 9, the curvature of which is adapted to that of the ring ends. For better anchorage of the second insert 21 in the shell 19 the corresponding external circumferential surface of the insert 21 is knurled.

As Figures 3 and 4 show this embodiment also has an end bore and two diametrically arranged radially extending transverse bores, as already set forth in the description of Figures 1 and 2.

If after the lighting of an arc its foot springs over on to the electrode head and remains stationary there on the second insert 21, because its end bore fixes the arc foot point in known manner, then the second insert 21 as a result of its very good thermal stability advantageously prevents the burning away and thus destruction of the electrode head.

If as may happen the line fuse responds only with a certain time delay so that the arc may cause a certain burning away on the shell 19 surrounding the insert 21, then the first insert 20 as a result of its high thermal stability prevents the entire burning body, and thus the burning strut, from becoming useless.

In Figure 5 the insulator string is represented in dot-and-dash lines in the form of a long rod 1 01.

By means of a screw (not shown) a double eye 103 is articulated to the cap 102 and again the arcing ring, designated as a whole by 104, is fitted fast in rotation on this eye by means of a screw 105.

The arcing ring 104 itself consists of, as well as the two approximately diametrically opposed struts 106 and 107, the actual ring 108 which has a C-shaped profile as shown by Figure 5. The arcing ring 108, as shown by Figure 6, has free ends 112 and 113 which together form the opening 114.

The ring 108 is secured directly to the string fitting 103 in its middle plane E-E (see Figure 5) by means of a solid metal strut 106, which for this purpose has an eye 110 formed by pressing on its end 109. The other end 111 of the strut 106 opens in the interior of the ring 108 and is there preferably welded, as shown by Figures 5 and 6.

The goose-neck form of the strut 106 (see Figure 5) permits on the one hand convenient attachment to the fitting 103 and on the other hand deep introduction into the profile of the ring 108 and secure fastening there. It further permits of guiding the strut 106 close along on the insulator cap 102. By shifting the central axis C C (see Figure 6) of the string insulator 101 in relation to the central axis D-D of the ring 108 by the amount "a" it is ensured in previously known manner that the open ring ends lie remote from the insulator 101, even when a favourably priced ring of relatively small diameter is used.

The arcing strut 107 is also made in gooseneck form, the one end 11 5 being formed with a pressed eye 116, as shown by Figures 5 and 6.

This eye can then be screwed, together with the eye 110 of the strut 106, to the fitting 1 03 of the string insulator 101. For this purpose beside a screw 105 there also serves a nut 117 and securing washers 1 18, which lie firmly free from rotation in notches 1 9, 1 19' of the strut eyes 110/11 6 and the turned-up tabs of which secure the hexagon of the nut and screw.

The other end of the mounting strut 107 terminates at the level of the ring central plane E-E in an arm 120 centrally penetrating the opening 114 of the ring 108, which arm carries an electrode head 1 21. As regards dimensions the strut 107 is designed according to the rated short-term current to be transmitted in an emergency.

As seen in Figure 8, the electrode head 1 21 has a frontal approximately part spherical external configuration 1 22 adjoined by an upper defining surface 1 23 and the lower defining surfaces 1 24 and 125. The defining surfaces 1 23 and 125 are arranged at an acute angle to one another.

Symmetrically of the longitudinal central plane F-F the electrode head 121 is defined by mutually parallel side faces 126 and 127, as shown by Figure 6. The curvature of the outside 128 is adapted to the curvature of the profile of the arcing ring 108.

The side faces 126 and 127 continue with defining surfaces 129 and 130 which in collaboration with the surfaces 123 and 125 (see Figure 8) form a pyramid frustum which defines the end of the electrode head 1 21 opposite to the outer side 128.

Into the end face of the pyramid frustum there opens a bore 1 31 which receives the arm 120 of the arcing strut 1 07. However this arm is introduced into the bore 131 only so far that there remains a cavity 1 32 between the end face 107', of the strut 107 and the bottom of the bore 131.

Then the strut 107 is welded with the electrode head.

A passage 133 penetrating the electrode head and terminating at the outside 128 as shown by Figure 6 co-axially adjoins the bore 131. The mouth opening is sharp-edged or defined with a small radius.

The side faces 126 and 127 are connected with the bore 131 by transverse passages 133'.

The longitudinal axes of the transverse passages 133' point away from the outer side 128 and each form an acute angle with the longitudinal central plane F-F, as shown by Figure 6. The transverse passages 133' then extend advantageously nearly parallel with the ends 11 2 and 113 of the arcing ring 108.

In accordance with the invention and as shown by Figures 6 and 8, the side faces 126/127 of the electrode head 1 21 each carry a raised bead 134 and 135. The beads are made C-shaped (see Figure 8); the opening of the C then faces the arm 120 of the strut 107.

The upper arm 136 of the C-shaped bead 135, as shown by Figure 8, is shorter than the lower arm 137; the free ends of the arms 136,137 are rounded. Moreover the beads 134, 135 are made symmetrical of the central plane E-E and F-F.of the ring 108.

As Figure 6 shows, the beads 134, 135 comprise the support faces 138 and 1 39 facing the outside 128, the curvature of which is adapted to the curvature of the ends 112 and 113 of the arcing ring 108.

These arcing-ring ends are provided with caps 110 consisting of synthetic plastics material, as shown by Figure 6, which then enclose the ring ends 112 and 113.

As Figure 8 shows, the cap 140 is made in C form with adaptation to the cross-sectional form of the arcing ring 108; the opening of the C-form of the end cap 140 is then placed in the same direction as the C-shaped opening of the bead 135.

The curvature of the inner peripheral surface 140' of the end cap 140 is advantageously adapted to the curvature of the outer peripheral surface 135' of the bead 135 as shown by Figure 8. The radially extending fianks of the end caps 140 also fit closely to the support surfaces 138/139 of the beads 134, 135 as shown especially by Figure 6.

Then the end caps 140 fitted on the ring ends 112, 11 3 advantageously are supported firmly and non-displacably on the beads 134,135 and the support faces 1 38, 1 39 of the electrode head 121, as shown by Figures 6 and 8. Thus in desired manner feed of an arc foot can take place on the one hand from the ring and on the other directly through the arcing strut 107, the introduced arc foot being held fast securely on the electrode head.

On the occurrence of an arc the transverse passages 133' in the electrode head 1 21 advantageously permit the escape of the plasma current of the arc into the interior of the ends 112, 113 of the arcing ring 108, without the arcing ring ends being damaged by the hot plasma current, which could lead to the arcing ring becoming useless.

Arcing ring and struts can consist according to choice of steel or light metal. The burning electrode 121 on the other hand fundamentally consists of steel or malleable cast iron, in order to minimize the burningaway effect of the arc.

The example of embodiment as illustrated in Figure 7 differs from that in Figure 6 merely in that the two struts 106 and 107 are made in one piece. Thus the single strut 141 fulfills the function of a retaining strut and an arcing strut, as already set forth in the description of Figure 6. All further functions of the arcing ring according to Figure 7 can thus be attributed to the example of embodiment according to Figure 6.

As compared with existing devices, the arc rings and electrodes illustrated have a higher resistance to burning away and can be produced at a favourable cost.

Claims (12)

Claims

1. A burning or sacrificial electrode for an open arcing ring which electrode comprises a strut carrying at one end an electrode head adapted to lie between and engage the ends of the arcing ring when in use and having an end face for in use forming the foot of any arc struck to the electrode, which electrode head comprises a shell containing an insert of high burning resistance material which is exposed at and lies flush with the said end face.

2. An electrode as claimed in claim 1 , wherein the insert is of metal or graphite.

3. An electrode as claimed in claim 2, wherein the insert is of steel or tungsten.

4. An electrode as claimed in any preceding claim, wherein the shell is of aluminium.

5. An electrode as claimed in any preceding claim, wherein there is a bore extending from the said end face into the insert to assist in fixing the foot of any arc struck when the electrode is in use.

6. An electrode as claimed in claim 5, wherein one or more bores transverse to and communicating with the said bore are provided opening the exterior of the electrode shell.

7. An electrode substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2, Figures 3 and 4, Figures 5, 6 and 8, or Figure 7.

8. An arcing ring for a high-tension overhead transmission line insulator comprising an openended electrically conductive ring having insulating end caps, disposed on its open ends and, engaging the end caps, an electrode as claimed in any preceding claim.

9. An arcing ring as claimed in claim 8, wherein the ring is formed from C-section metal having the open face of the section facing the centre.

10. An arcing ring, a high-tension overhead transmission line insulator, having a pair of free ends covered by caps of insulating material between which ends lies an electrode head to serve as an arc foot, which head bears a mounting strut extending into the ring and has on the side opposite to the entry point of the strut an end bore which is in communication with at least one transverse passage which opens into a side face of the electrode head between the free ends of the arcing ring, and which ring bears a second metallic strut serving for securing the assembly to the insulator and which is adapted to be attached with the first mentioned strut to the insulator wherein side faces of the electrode head are provided with C-shaped protruding beads which firmly and non-displacably accommodate the caps fitted on the ring ends and serve as support for the ends of the arcing ring.

11. An arcing ring as claimed in claim 10, wherein the curvature of the internal peripheral surface of the end caps matches the curvature of the external peripheral surface of the beads.

12. An arcing ring as claimed in claim 5, wherein the longitudinal axes of the transverse passages point away from the outer side of the electrode head and extend approximately parallel with the arcing ring ends.

1 3. An arcing ring and electrode assembly substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2, Figures 3 and 4, Figures 5, 6 and 8 or Figure 7 of the accompanying drawings.