WO2005020263A1

WO2005020263A1 - Surge protected fuse switch

Info

Publication number: WO2005020263A1
Application number: PCT/IB2004/002760
Authority: WO
Inventors: Philip Edward Lawrence Risi
Original assignee: Philip Edward Lawrence Risi
Priority date: 2003-08-26
Filing date: 2004-08-26
Publication date: 2005-03-03

Abstract

This invention relates to an electrical protection assembly (110) for connection between an electrical power supply line and electrical equipment which is susceptible to lightning damage. The assembly includes two sections that are electrically in parallel. A first of these sections has a fusible element (90) in series with a blocking arrangement for blocking extra high voltage surge current through the fusible element, to protect the fusible element. A second of these sectionshas an extra high voltage surge conducting device for conducting extra high voltage surge current. Theblocking arrangement includes a coil (64), and the extra high voltage surge conducting device is in the form of an air gap arrangement defining an air gap which is bridgeable, in use, by an arc. The assembly also includes an arc dissiating device for dissipating an arc formed when the fusible element fuses. The invention extends to an installation (12) which includes the electrical protection assembly.

Description

SURGE PROTECTED FUSE SWITCH THIS INVENTION relates to the distribution of electricity. In particular, the invention relates to an electrical protection assembly for connection between an electrical power supply line and electrical equipment which is susceptible to lightning damage. The invention also relates to an electrical installation which includes the electrical protection assembly.

In accordance with one aspect of the invention there is provided an electrical protection assembly for connection between an electrical power supply line and electrical equipment which is susceptible to lightning damage, which assembly includes two sections that are electrically in parallel, a first section having a fusible element in series with a blocking arrangement for blocking extra high voltage surge current through the fusible element, to protect the fusible element, and a second section having an extra high voltage surge conducting device for conducting extra high voltage surge current.

The extra high voltage surge conducting device may be in the form of an air gap arrangement, defining an air gap bridgeable, in use, by an arc.

The fusible element may be a fuse, the blocking arrangement being a circuit containing a coil. The assembly may include an elongated body structure at least partially constructed of an electrically insulating material, the body structure having first and second opposite ends, and first and second electrically conductive mounting formations connected to the body structure at longitudinally spaced positions along the body structure for removably and replaceably mounting the assembly, in use, on a support structure electrically connected to an electrical power supply line and to electrical equipment which is susceptible to lightning damage, one of the mounting formations being constructed to permit displaceable mounting of the assembly on the support structure, with the two sections being electrically connected to and extending between the first and the second mounting formations.

The second section may also include an arc dissipating device for dissipating an arc formed when the fuse fuses.

The arc dissipating device may have a first part and a second part between which the air gap is defined, the first part and the second part being movable apart to increase, in use, the length of an arc therebetween.

The extra high voltage surge conducting device and the arc dissipating device may be combined.

The arc dissipating device may include a first electrode defined by the first part of the device and electrically connected to the first mounting formation, ana a second electrode defined by the second part of the device and electrically connected to the second mounting formation, the first and the second electrodes being suitably spaced apart to define said air gap therebetween, and with the extra high voltage surge conducting device being defined by said first and second electrodes and the air gap therebetween.

The body structure may include a housing component in which at least part of the first and the second sections are housed.

The arc dissipating device may be in the form of a retracting arc dissipating horn, with at least one of the first and the second part of the arc dissipating device being movable, relative to the other part, through a dissipating passage defined by the housing component.

The first electrode may be located outside the dissipating passage, being fast with the body structure at a suitably spaced distance from a mouth of the dissipating passage, the second electrode projecting from the mouth of the passage and being provided with an insulating cap that closes the mouth of the passage when the second electrode moves into the passage, in use, to help extinguish an arc formed between the first and the second electrodes.

In one embodiment, the second mounting formation may include a spring loaded formation to which the second part of the arc dissipating device is mechanically connected, the spring loaded formation being displaceable between a cocked position in which the second electrode projects operatively form the dissipating passage, and a fused position in which it is displaced under said spring load to pull the second electrode in to the dissipating passage, the spring loaded formation being retained in its cocked position by a flexible electrically conductive wire fast with the fuse, so that when the fuse fuses, the spring loaded formation is automatically displaced towards its fused position to pull the second electrode in to the dissipating passage.

In this embodiment, the second mounting formation may be pivotally connected to the body structure to pivot about a transverse pivot axis, the second mounting formation being immovably anchorable to the body structure by means of a retaining formation provided by the spring loaded formation, and which retaining formation engages a complementary formation provided by the second end of the body structure when the spring loaded formation is in its cocked position, so that when the fuse fuses and the spring loaded formation is displaced towards its fused position, the second mounting formation is free to pivot relative to the body structure in a direction which shortens a distance between the first and the second mounting formation, in use, to release the first mounting formation from the support structure on which the assembly is mounted..

In another embodiment, the second mounting formation may include a spring loaded holding member moveable between a holding position in which it holds the assembly, in use, in an operative condition on a support structure on which the assembly is mounted, and a fused release position in which it permits displacement ot the assembly, in use, relative to said support structure, the second part of the arc dissipating device being mechanically connected to the holding member, with the holding member being biased, on account of the spring loading, towards its fused released position and being kept in its holding position by means of a flexible electrically conductive wire connected to the fuse and fast with the holding member, such that, in use, when the fuse fuses, the holding member is moved, under said bias, towards its fused release position, which causes the second electrode to be pulled into the dissipating passage, so that an arc formed between the two electrodes upon fusing of the fuse is extinguished, and permits displacement of the assembly relative to said support structure.

The holding member may be an elongated member pivotally connected, between its ends, to the second mounting formation to pivot about a transverse pivot axis spaced from the second end of the body structure, the holding member defining two limbs, one on either side of the pivot axis, one of the limbs being provided with a holding formation for engaging, in use, a complementary holding formation provided on a support structure on which the assembly is mounted, with the second part of the arc dissipating device and said flexible electrically conductive wire being connected to the other limb, the holding member being biased to pivot towards its fused release position.

In yet another embodiment, the body structure may also include an elongated body component, the mounting formations being connected to the body component, with the second end of the housing component being pivotally mounted on the body component to be pivotable about a transverse axis adjacent the second mounting formation, the housing component defining another passage through which the first section extends, the fuse being of the detonating type and being mechanically connected to the first mounting formation, to anchor a first end of the housing component to the body component, so that, in use, when the fuse fuses and detonates, the first end of the housing component is released from the body component and the housing component is pivotally displaceable relative to the body component, causing the first electrode to be pulled out of the dissipating passage upon displacement of the housing component relative to the body structure, to extinguish an arc formed between the first and the second electrodes.

In still a further embodiment, the body structure may also include an elongated body component, the mounting formations being connected to the body component, with the second end of the housing component being pivotally mounted on the body component to be pivotable about a transverse axis between the first and the second mounting formations, the first part of the arc dissipating device being fast with the first mounting formation and the second part of the arc dissipating device being fast with a first end of the housing, with the fuse being of the detonating type and being mechanically connected to the first mounting formation by means of a flexible electrically conductive wire, to anchor the first end of the housing component to the body component with the first electrode and the second electrode spaced apart a suitable distance, so that, in use, when the fuse fuses and detonates, the first end of the housing component is released from the body component and the housing component is pivotally displaceable relative to the body component, causing, upon displacement of the housing component, the distance between the first electrode and the second electrode to increase, to dissipate an arc formed therebetween.

In still another embodiment, the body structure may include a body component to which the mounting formations and the extra high voltage surge conducting device are secured, and a housing component in which the first section is housed, the housing component being pivotally mounted at a second end thereof on the body component to be pivotable about a transverse axis between the first and the second mounting formations, with the fuse being of the detonating type and being mechanically connected to the first mounting formation by means of a flexible electrically conductive wire, to anchor a first end of the housing component to the body component, so that, in use, when the fuse fuses and detonates, the first end of the housing component is released from the body component and the housing component is pivotally displaceable relative to the body component.

In this embodiment, the assembly may include a surge arrestor for connection to earth, the surge arrestor being in series with the first and the second sections, the assembly also including a third mounting formation, the second mounting formation being located between the first and the third mounting formations, and with the surge arrestor being electrically connected to and extending between the second mounting formation and the third mounting formation. The blocking arrangement may include a resistor in series witn tne con.

In some embodiments, the extra high voltage surge conducting device may include two electrodes which are spaced apart to define said air gap therebetween, a first of the electrodes defining a tubular passage, with a second of the electrodes being received in the passage defined by the first electrode, so that the air gap is substantially annularly shaped, being defined between a surface of the wall of the first electrode defining the passage and an outer surface of the second electrode.

In accordance with another aspect of the invention there is provided an electrical installation which includes an electrical protection assembly as hereinbefore described.

The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Figure 1 shows a schematic, part-sectioned, side view of one embodiment of an electrical protection assembly in accordance with the invention in its normal operative configuration; Figure 2 shows the embodiment of Figure 1 just after an overload condition has occurred and a fusible element forming part of the assembly has fused; Figure 3 shows the embodiment of Figure 1 in a fused configuration; Figure 4 shows a schematic, part-sectioned, side view of another embodiment oτ an electrical protection assembly in accordance with the invention in its normal operative configuration; Figure 5 shows the embodiment of Figure 4 just after the fusible element has fused; Figure 6 shows a schematic, part-sectioned, side view of a further embodiment of an electrical protection assembly in accordance with the invention in its normal operative configuration; Figure 7 shows the embodiment of Figure 6 just after the fusible element has fused; Figure 8 shows the embodiment of Figure 6 in a fused configuration; Figure 9 shows a schematic side view of yet another embodiment of an electrical protection assembly in accordance with the invention in its normal operative configuration; Figure 10 shows a schematic side view of still another embodiment of an electrical protection assembly in accordance with the invention in its normal operative configuration; Figure 11 shows a schematic side view of still a further embodiment of an electrical protection assembly in accordance with the invention in its normal operative configuration; and Figure 12 shows a schematic, part-sectioned, side view of a yet further embodiment of an electrical protection assembly in accordance with the invention in its normal operative configuration;

Referring to Figure 1 , one embodiment of an electrical protection assembly in accordance with the invention is designated generally by reference numeral 10. The assembly 10 forms part of an installation 12 (shown in part only) for supplying electrical power to a transformer (not shown). The installation 12 has an upper supply arm 14 tnat is connected to a power supply line and a lower load arm 16 that is connected to the transformer. The supply arm 14 has a spring loaded contact 18 and the load arm 16 has a slot 20. The supply arm 14 and the load arm 16 form part of an electrical connection device as described in the Applicant's co-pending South African patent application no. 2004/3596.

The assembly 10 is mounted between the supply arm 14 and the load arm 16. Thus, the assembly 10 has a lower pin 22 that is received in the slot 20 and an upper contact 24 that engages the contact 18. The pin 22 is metallic and is attached to or integral with a second mounting formation in the form of a metal fitting 26 (also hereinafter referred to as the lower fitting 26), such that it provides mechanical support and an electrical connection with the load arm 16. The upper contact 24 is provided on a first mounting formation in the form of a metal fitting 28 (also hereinafter referred to as the upper fitting 28). The lower fitting 26 is secured to the second- or bottom end of an elongated body component in the form of a support bar 30 that is of an electrically insulating material, and the upper fitting 28 is secured to a first- or upper end of the support bar 30. The fittings 26, 28 and the support bar 30 together form part of a body structure 32 of the assembly 10.

As shown in the drawings, the upper fitting 26 has an upper eye 34 that is engageable, in use, by a hook at the end of a pole (not shown) to remove or install the assembly 10. The lower fitting 28 also has a lower eye 36. Thus, to remove the assembly 10, the tool is engaged with the upper eye 34 and the upper Titting zo is puneo or yanked downwardly to disengage the contact 24 from the contact 18. The assembly 10 is then pivoted about the pin 22, the tool disengaged from the eye 34, engaged with the lower eye 36 and the pin 22 is lifted out of the slot 20. Installation of the assembly 10 is the reverse.

The assembly 10 further has an elongated housing component 38 formed from an insulating holder 40 and a metallic foot piece 42. The elongated housing component 38 and the foot piece 42 also form part of the body structure 32. The foot piece 42 has a further pin 44 that is received in a further slot 46 in the lower fitting 26. The holder 40 has two passages 48 and 50 that extend longitudinally therethrough. The passage 48 forms a dissipating passage, as will become more apparent hereinafter. In the passage 48 there is housed a pair of spaced electrodes 52 and 54. They provide a combination spark gap arrangement and retracting arc dissipating device, and form a second section of the assembly of the invention. The spark gap arrangement comprises an extra high voltage surge conducting device of the invention, as will become more apparent hereinafter. The lower (or second) electrode 52 is connected to the foot piece 42 by a conducting rod 56, the lower electrode and the conducting rod forming a second part of the retracting arc dissipating device. The upper (or first) electrode 54 is connected to the upper fitting 28 by a flexible conducting wire 58, the upper electrode 54 and the wire 58 forming a first part of the retracting arc dissipating device. The upper fitting 28 has a finger 60 to which the wire 58 is attached, the finger 60 providing an anchor for the wire 58. The electrode 54 is movable along and out of the passage 48. In the other passage 50 there are housed a spring loaded detonating

fuse 62, a coil 64 and a resistor 66 (all being shown in concept only), which together

form a first section of the assembly of the invention. The fuse 62, the coil 64 and

the resistor 66 are connected electrically in series by means of electrically conductive

wires, all of which are, conveniently, indicated by reference numeral 59, with the

resistor 66 being connected to the foot piece 42 by means of the electrically

conductive wire 59, and the fuse being in electrical contact with the finger 60. The

fuse 62 comprises the fusible element of the invention and the coil 64 and resistor 66

comprise the blocking arrangement of the invention. Furthermore, the first and the

second sections are electrically in parallel.

It will be appreciated by those skilled in the art, that, in use, normal current

supply will flow through the fuse 62, coil 64 and resistor 66. However, the coil 64 and

resistor 66 are such that if there is a high voltage surge such as occurs with lightening, the

impedance thereof will be sufficiently high for the voltage across the electrodes 52 and 54

to increase above the breakdown value and current will be diverted through the parallel

path provided by the electrodes 52 and 54, thereby protecting the fuse 62.

If there is a current overload at rated voltage, the fuse 62 will blow, activating

the detonator thereof. This dislodges the first or upper end of the housing component 38

from the finger 60 and the housing component 38 starts pivoting downwardly, under

gravity, about the pin 44, .as indicated by arrow 68 in Figure 2. Also, because of the rapid increase in voltage across the electrodes 52 and 54, an arc is created between tnem. However, because the wire 58 is anchored to the finger 60 the electrode 54 is pulled along and out of the passage 48, such that the arc dissipates. Thus, the electrodes 52 and 54 and the passage 48 form a retracting arcing horn. Eventually, the housing component 38 hangs down from the lower fitting 26, as shown in Figure 3, indicating to service personnel that there has been a problem and the assembly 10 needs to be replaced. It will be appreciated further that the spacing between the electrodes 52 and 54 is small enough for an arc to form when the fuse fuses and when there is a voltage surge from lightening or the like, but large enough to impede the formation of an arc under normal operating conditions.

Referring now to Figure 4 another embodiment of an electrical protection assembly in accordance with the invention is designated generally by reference numeral 70. The embodiment 70 more or less resembles the first embodiment 10 and, unless otherwise indicated, is similarly referenced.

However, with the embodiment 70 the body component and the housing component are integrally formed and conveniently hereinafter referred to as the body structure 32. The lower fitting 26 is fast with a lower end of the body structure. The lower fitting 26 is held in its operative position by a holding member 72 that is pivotal, about a transverse pivot axis, relative to the lower fitting 26 between a normal holding position (shown in Figure 4) in which the lower fitting 26 is held in its operational position relative to the load arm 16; and a fused release position, (shown in Figure 5) in which the lower fitting 26 and the body structure 32 are released and may automatically pivot, under gravity, away from their operational positions and the body structure 32 disengages the supply arm 14. Thus, the holding member 72 has a holding formation in the form of a hook 74 provided by one limb of the holding member 72, which hook 74 engages a complementary holding formation in the form of slot 76 in the load arm 16. The holding member 72 is pivotal about the pin 22. The holding member 72 further has another limb 76 which is below the lower fitting 26 and extends away from the pin 22 on the opposite side thereof than the hook 74, the limb 76 being urged away from the lower fitting 26 by a compression spring 78.

The body structure 32 has three passages 80, 82 and 84. The passage 80 is closed at its upper end by a contact 86 that engages the contact 18, in use, when the body structure 32 is in its operative position. The coil 64 is housed in the passage 80 and is electrically connected to the contact 86. The passage 84 is also closed off at its upper end by a metal connector 88 that is integral with the upper eye 34. A fusible element, in the form of a fuse 90 which is not of the detonating type, is housed in the passage 84. One end of the fuse 90 is connected to the connector 88 by an electrically conductive wire 92 and the other end of the fuse 90 is connected to the limb 76 by an electrically conductive wire 94 that passes through an opening 96 in the lower fitting 26. The connector 88 is connected to the coil 64 by an electrically conductive wire 98. It will be understood that the wire 94 keeps the limb 76 adjacent the lower fitting 26, in its holding position, with the spring 78 compressed. A cylindrical electrode 100 is positioned at the upper end of the passage 82, with a portion thereof protruding from the mouth of the passage 82. The electrode 100 has an insulating cap 102. It will be appreciated that the side of the electrode 100 is spaced a suitable distance from the side of the contact 86, so that the contact 86 also acts as an electrode and the two define between them a spark gap. The electrode 100 is connected to the limb 76 by an electrically conductive wire 104, which passes through a further opening 106 in the lower fitting 26.

As shown in Figure 5, when the fuse 90 fuses, the limb 76 is released and it is pivoted, relative to the lower fitting 26, by the force exerted thereon by the spring 78. The electrode 100 is pulled into the passage 82, with the cap 102 then closing the mouth of the passage 82. It will be appreciated that an arc will be created between the contact 86 and the electrode 100, which gets extinguished when the cap 102 closes the mouth of the passage 82.

Further, it will be understood that the lower fitting 26 is able to pivot about the pin 22 when the hook 74 exits the slot 76, and the assembly 70 then pivots about the pin 22, in a direction indicated by arrow 108, under gravity, with the contact 86 disengaging the contact 18, until the assembly 70 hangs down from the load arm 16.

Figures 6 - 8 show yet another embodiment of an electrical protection assembly in accordance with the invention, the assembly being designated by reference numeral 110. The embodiment 110 is more or less similar to the embodiment (0 and, accordingly, is similarly referenced.

In the embodiment 110, the body component and the housing component are fast with each other, being referred to as the body structure 32. The body structure 32 is of composite construction, including an elongated casing 107 of an insulating material, and three hollow rods 109, 111 , 113 of insulating material secured to the casing 107. The rod 109 provides the passage 80, the rod 111 provides the passage 82, and the rod 113 provides the passage 84. A top of the passage 84 is closed by a screw-on cap 115, to permit easy replacement of the fuse 90 when it has fused.

The wire 98 is electrically connected to an electrically conductive base portion of the upper eye 34 by means of a screw 117. Naturally, one end of the wire 92 is also electrically connected to said base portion of the upper eye 34. Two spacers 119, 121 of insulating material are provided between the rods 111 , 113.

The lower fitting 26 is secured to the lower end of the body structure 32. In this embodiment, however, the lower fitting 26 is pivotally secured, by means of a pin 112, to a ring 114 fast with the lower end of the body structure 32, to pivot about a transverse axis defined by an axis of the pin 112. The pin 112 is mounted on or is integral with the ring 114. The lower fitting 26 includes a spring loaded formation 116 which is pivotally connected thereto adjacent that end of the lower fitting 26 at which the pin 22 is provided.

The formation 116 is pivotable about a transverse pivot axis between a cocked position

(Figure 6) and a fused position (Figures 7 and 8). The formation 116 defines a retaining formation 118 and a lever 120. A spring 122 biases the formation 116 towards its fused position. The lower fitting 26 is provided with a threaded stud 124 onto which a washer- and-nut arrangement 126 is received. The flexible conducting wire 94 is fed over the lever

120 and pulled tight to displace the formation 116 to its cocked position, with the wire 94 being secured to the lower fitting 26 by means of the washer-and-nut arrangement 126.

A cap member 128 closes a lower end of the passage 82. The electrical wire 104 extends through the cap and is connected to a cable 130 which, at one end thereof, is also connected to the cap 128. The other end of the cable 130 is secured to the spring loaded formation 116. One end of a further conductive wire 132 is connected to the cap 128, the other end of the wire 132 being connected to the lower fitting 26 by means of a screw 134.

When the formation 116 is in its cocked position, the retaining formation 118 defined thereby engages a complementary formation 128 defined by the lower eye 36, so that the lower fitting 26 is immovably anchored, i.e. it cannot pivot, relative to the body structure 32. The wire 94 thus retains the spring loaded formation 116 in its cocked position, which results in said immovability between the lower fitting 26 and the body structure 32. The length of the cable 130 between the cap 128 and the spring loaded formation 116 is such that when the spring loaded formation 116 is in its cocked position and the lower fitting 26 is anchored relative to the body structure 32, the cable 130 is substantially taught. Pivoting of the spring loaded formation 116 towards its fused position will thus cause the second electrode 100 to be pulled into the passage 82.

When the fuse 90, which is in this embodiment is also not of the detonating type, fuses, the spring loaded formation 116 is automatically, under bias of the spring 122, pivoted towards its fused position, which, as hereinbefore mentioned, results in the electrode 100 being pulled into the passage 82. The cap 102 closes of the mouth of the passage 82, and an arc formed between the contact 86 and the electrode 100 is extinguished. Further, because the spring loaded formation 116 is then in its fused position, the lower fitting 26 is free to pivot relative to the body structure 32. The lower fitting 26, while the pin 22 remains in the slot 20, pivots upward, which decreases the distance between the pin 22 and the contact 86, which enables the assembly 110 to pivot, about the pin 22, downward under gravity in a direction indicated by arrow 136 ( Figure 7), so that it hangs down from the load arm 16 as shown in Figure 8.

Referring now to Figure 9 of the drawings, reference numeral 150 generally indicates still a further embodiment of a protection assembly in accordance with the invention. The embodiment 150 more or less resembles the embodiment 10 and, unless otherwise indicated, is similarly referenced. In this embodiment, the housing component and the body component are integrally formed, being in the form of an elongated hollow rod, indicated by reference numeral 38, of an insulating material. The lower fitting 26 and the upper fitting 28 are secured respectively to the lower- or second end of the rod 38 and to the upper- or first end of the rod 38. The first section of the assembly of the invention, i.e. the fuse 62, the coil 64 and the resistor 66, are housed in the rod 38. The second section of the assembly of the invention, i.e. two electrodes 52, 54 and their associated conductive links, which are both electrically conductive rods 56, 58, are also housed in the rod 38. The conductive rod 58 is connected to the upper fitting 28, and the conductive rod 56 is connected to the lower fitting 26. The embodiment 150 does thus not include an arc dissipating device.

Figure 10 shows still another embodiment of the assembly in accordance with the invention. The embodiment shown in Figure 10 is generally designated by reference numeral 160. The embodiment 160 more or less resembles the embodiment 150 and, unless otherwise indicated, is like referenced.

In the assembly 160, the body structure 32 includes both the body component 30 and the housing component 38. The body component 30 is similar to the elongated rod 38 hereinbefore described with reference to Figure 9, with the exception that it houses nothing.

The housing component, in this embodiment, is in the form of a block 38 of insulating material, which is pivotally attached, by means of a pin 57, adjacent its bottom end to the body component 30 to pivot about a transverse axis. The block 38 has a longitudinally extending groove (not shown) in which is housed the fuse 62, the coil 64 and the resistor 66. The resistor 66 is electrically connected to the lower fitting 26 by means of an electrically conductive link in the form of a flexible electrically conductive wire 59. The fuse 62, on the other hand is connected to the upper eye 34 by means of a flexible electrically conductive wire, also indicated by reference numeral 59. The block 38 further has a passage (not shown) through which the wire 56 extends. The electrode 52 is connected to the wire 56 and is located outside the block 38, so that it is spaced at a suitable distance from the electrode 54, which electrode 54 is defined by the upper eye 34. In this embodiment, the electrode 52 includes a screw cap, to permit adjustment of the length of the air gap defined between the electrodes 54, 52. The wire 56 is connected to the wire 59, so that the first and the second sections of the invention are in parallel.

In this embodiment, the block 38 is held in its operative position (as shown in Figure 10) by means of the wire 59 connected to the fuse 62 and to the eye 34. When the fuse 62 (which is of the detonating type) fuses and detonates, the block 38 is thus free to pivot, under gravity, away from the body component 30. Upon pivoting, the length of the air gap between the electrodes 52, 54 is increased, and the groove acts as an arc chute, to help extinguish the arc formed between the electrodes 52, 54. When the block 38 has pivoted, it hangs down from the body component 30, serving as a visual indication that the fuse 62 has fused, and needs to be replaced. In Figure 11 , reference numeral 170 generally designates still a further embodiment of the assembly in accordance with the invention. The assembly 170, or at least part thereof, resembles the assembly 160 and is, unless otherwise indicated, like referenced.

The assembly 170 includes also a surge arrestor unit 172 including a surge arrestor. The surge arresting unit 172 forms a longitudinal extension of the body component 30 of the embodiment 160. The lower fitting, in this embodiment, is in the form of a laterally projecting arm 26 fast with the body portion 30. The arm 26 is provided with a contact 174 for engaging a contact 176 provided by the load arm 16. The surge arrestor of the surge arresting unit 172 is electrically connected to the arm 26. At a lower end of the surge arresting unit 172 is provided a third mounting formation 178. The mounting formation 178 is provided with a pin 180 received in a slot 182 defined by an earth arm 184 forming part of the support structure on which the assembly 170 is mounted. The earth arm 184 also forms part of an electrical connection device as described in the Applicant's co-pending South African patent application no. 2004/3596.

The lower eye 36, in this embodiment, is fast with a lower end of the surge arresting unit 172.

In this embodiment, the electrically conductive links, which are in the form of electrically conductive rods 56, 58, are located outside of the body component 30. Again, as hereinbefore, it will be appreciated that the coil 66 and the resistor 64 are such that their series impedance is negligible in normal operation, but increases substantially when an extra high voltage pulse appears, as would happen with a lightning strike. Then, as a result of the high impedance, the air gap defined between the two spaced electrodes 52, 54 breaks down and conducts the extra high voltage current, protecting the fuse 62. This extra high voltage current is then bypassed to earth, via the surge arresting unit 172. When the extra high voltage surge passes, the air gap is reestablished and normal current then flows again through the fuse 62.

The body component 30 is of composite construction, including, iri series, a head 188 of an electrically conductive material, an insulating bar 190, and a lower portion 192 of an electrically conductive material. The head 188 provides the upper fitting, with the eye 34 being fast with the head 188. The block 38 is pivotally connected to the insulating bar 190, and the lower fitting 28 is fast with and projects from the lower portion 192. The fuse 62 is electrically connected to the head 188 by the wire 59, and the resistor 66 is connected to the lower portion by means of the other electric wire 59, which wire 59 is secured to the lower portion 192 by means of a wing-nut 194 received over a threaded stud 196 fast with and projecting laterally from the lower portion 192.

The surge arrester of the surge arresting unit 172 is of the type typically used to protect electrical equipment, such as a transformer, against lightning damage in high tension power installations. The surge arrester thus provides a relatively high impedance at normal voltage levels, and low impedance at extra high voltage levels, so that current resulting from a high voltage surge is channeled to earth.

The surge arresting unit 172 further includes a detonator cap 186 which is arranged automatically to detonate when the performance parameters of the search arrester, which deteriorate over time, fall below predetermined levels, i.e. when the surge arrester is about to malfunction.

During normal operation, electrical power is conducted through the fuse 62 to electrical equipment. If the current through the fuse 62, owing to malfunction of the electrical equipment or for any other reason, exceeds the predetermined limit, the fuse 62 blows. This power failure will prompt repair services to replace the fuse 62 by replacing the entire assembly 170.

When lightning strikes the installation of which the assembly 170 forms part, the resultant extra high voltage current surge is diverted through the air gap arrangement and the through the surge arrester to earth, thus protecting the equipment from lightning damage. However, when, over time, the surge arrester deteriorates past a predetermined limit, the detonator cap 186 automatically blows. This detonation of the detonator cap 186 causes shortening of the assembly 170, and consequent disengagement of the contacts 24, 174 from their engagement with the contacts 18, 176, resulting in pivotal displacement of the assembly 170 downwardly under gravity about an axis of the pin 180. Referring now to Figure 12, a yet further embodiment of an assembly in accordance with the invention is generally designated by reference numeral 200. The embodiment 200 is more or less similar to the embodiment 110 shown in Figures 6 - 8 and, unless otherwise indicated, is similarly referenced.

The body structure 32 of the assembly 200 is in the form of a moulding or casting formed from an electrically insulating resin. The coil 64 and the hollow rod 113 is thus embedded in the body structure 32. In the assembly 200, the contact 86 also forms part of the upper fitting of the assembly 200. Here, however, the contact 86 defines a passage 202, the passage 202 having an open bottom, within which an elongated rod-like electrically conductive connector 204 is received. The contact 86 is thus received over one end of the connector 204, and is secured thereto by means of a grub screw 206, so that the longitudinal position of the contact 86 relative to the connector 204 is adjustable, to permit adjustment of the length of the assembly 200. Engagement between the contact 86 and the connector 204 is, naturally, of an electrically conductive nature.

A lower end of the connector 204 is embedded in the body structure 32, and is provided with a longitudinally extending tubular-shaped blind passage 208. An upper end of the elongated rod 111 is snugly received into the open end of the passage 208. As mentioned, the rod 111 is of an insulating material construction. The rod 111 extends to a lower end of the body structure 32, so that the passage 82 defined thereby provides communication between the blind passage 208 and the atmosphere. A lower end of an electrically conductive tube 210 is received in the upper end of the rod 111 , so that an upper end of the tube 210 is located in the blind passage 208. As can be seen, the upper end of the rod 111 insulates the connector 204 from the tube 210. However, due to the fact that the upper end of the tube 210 is located in the passage 204, a spark gap is defined between the tube 210 and the connector 204. The spark gap is thus annularly shaped. In this embodiment, the spacing between an outer surface of the tube 210 and the wall of the passage 208 is 0.9mm. One end of the wire 104 is electrically and mechanically connected to the tube 210, and the other end thereof is electrically and mechanically connected to the lower eye 36, the wire 104 being long enough, to accommodate pivoting of the body structure 32 about the pin 112. The connector 204 thus defines the first electrode of the assembly 200, and the tube 210 defines the second electrode thereof. The length of the spark gap is thus 0.9mm. Naturally, in other embodiments the length of the spark gap can have a different length.

The coil 64 is electrically connected between the connector 204 and the base portion of the upper eye 34.

During normal operation, and when the fuse 90 has fused, the assembly 200 operates like the assembly 110. However, during a high voltage surge condition, such as when lightning strikes, an arc will be created between the connector 104 and the tube 210. When the arc is created, the temperature of air in the blind passage 208 increases, causing it to expand, so that it blows out through the passage 82 into the atmosphere. Energy created by the arc is thus dissipated via the passage 82. The passage 82 thus serves as an arc dissipating device of the assembly 200. In use, the embodiments 10, 70, 110, 150 and 160 will typically be used in combination with surge arresting units, for purposes hereinbefore described with reference to the embodiment 170.

Claims

CLAIMS:

1. An electrical protection assembly for connection between an electrical power supply line and electrical equipment which is susceptible to lightning damage, which

> assembly includes two sections that are electrically in parallel, a first section having a fusible element in series with a blocking arrangement for blocking extra high voltage surge current through the fusible element, to protect the fusible element, and a second section having an extra high voltage surge conducting device for conducting extra high voltage surge current.

) 2. An assembly as claimed in Claim 1, in which the extra high voltage surge conducting device is in the form of an air gap arrangement, defining an air gap bridgeable, in use, by an arc.

3. An assembly as claimed in Claim 2, in which the fusible element is a fuse, the blocking arrangement being a circuit containing a coil.

4. An assembly as claimed in Claim 3, which includes an elongated body structure at least partially constructed of an electrically insulating material, the body structure having first and second opposite ends, and first and second electrically conductive mounting formations connected to the body structure at longitudinally spaced positions along the body structure for removably and replaceably mounting the assembly, in use, on a support structure electrically connected to an electrical power supply line and to electrical equipment which is susceptible to lightning damage, one of the mounting formations being constructed to permit displaceable mounting of the assembly on the support structure, with the two sections being electrically connected to and extending between the first and the second mounting formations.

5. An assembly as claimed in Claim 4, in which the second section also includes an arc dissipating device for dissipating an arc formed when the fuse fuses.

6. An assembly as claimed in Claim 5, in which the arc dissipating device has a first part and a second part between which the air gap is defined, the first part and the second part being movable apart to increase, in use, the length of an arc therebetween.

7. An assembly as claimed in Claim 6, in which the extra high voltage surge conducting device and the arc dissipating device are combined.

8. An assembly as claimed in Claim 7, in which the arc dissipating device includes a first electrode defined by the first part of the device and electrically connected to the first mounting formation, and a second electrode defined by the second part of the device and electrically connected to the second mounting formation, the first and the second electrodes being suitably spaced apart to define said air gap therebetween, and with the extra high voltage surge conducting device being defined by said first and second electrodes and the air gap therebetween.

9. An assembly as claimed in Claim 8, in which the body structure includes a housing component in which at least part of the first and the second sections are housed.

10. An assembly as claimed in Claim 9, in which the arc dissipating device is in i the form of a retracting arc dissipating horn, with at least one of the first and the second part of the arc dissipating device being movable, relative to the other part, through a dissipating passage defined by the housing component.

11. An assembly as claimed in Claim 10, in which the first electrode is located ) outside the dissipating passage, being fast with the body structure at a suitably spaced distance from a mouth of the dissipating passage, the second electrode projecting from the mouth of the passage and being provided with an insulating cap that closes the mouth of the passage when the second electrode moves into the passage, in use, to help extinguish an arc formed between the first and the second electrodes.

12. An assembly as claimed in Claim 11 , in which the second mounting formation includes a spring loaded formation to which the second part of the arc dissipating device is mechanically connected, the spring loaded formation being displaceable between a cocked position in which the second electrode projects operatively form the dissipating passage, and a fused position in which it is displaced under said spring load to pull the second electrode in to the dissipating passage, the spring loaded formation being retained in its cocked position by a flexible electrically conductive wire fast with the fuse, so that when the fuse fuses, the spring loaded formation is automatically displaced towards its fused position to pull the second electrode in to the dissipating passage.

13. An assembly as claimed in Claim 12, in which the second mounting formation is pivotally connected to the body structure to pivot about a transverse pivot axis, the second mounting formation being immovably anchorable to the body structure by means of a retaining formation provided by the spring loaded formation, and which retaining formation engages a complementary formation provided by the second end of the body structure when the spring loaded formation is in its cocked position, so that when the fuse fuses and the spring loaded formation is displaced towards its fused position, the second mounting formation is free to pivot relative to the body structure in a direction which shortens a distance between the first and the second mounting formation, in use, to release the first mounting formation from the support structure on which the assembly is mounted.

14. An assembly as claimed in Claim 11 , in which the second mounting formation includes a spring loaded holding member moveable between a holding position in which it holds the assembly, in use, in an operative condition on a support structure on which the assembly is mounted, and a fused release position in which it permits displacement of the assembly, in use, relative to said support structure, the second part of the arc dissipating device being mechanically connected to the holding member, with the holding member being biased, on account of the spring loading, towards its fused released position and being kept in its holding position by means of a flexible electrically conductive wire connected to the fuse and fast with the holding member, such tnat, in use, wnen me fuse fuses, the holding member is moved, under said bias, towards its fused release position, which causes the second electrode to be pulled into the dissipating passage, so that an arc formed between the two electrodes upon fusing of the fuse is extinguished, and permits displacement of the assembly relative to said support structure.

15. An assembly as claimed in Claim 14, in which the holding member is an elongated member pivotally connected, between its ends, to the second mounting formation to pivot about a transverse pivot axis spaced from the second end of the body structure, the holding member defining two limbs, one on either side of the pivot axis, one of the limbs being provided with a holding formation for engaging, in use, a complementary holding formation provided on a support structure on which the assembly is mounted, with the second part of the arc dissipating device and said flexible electrically conductive wire being connected to the other limb, the holding member being biased to pivot towards its fused release position.

16. An assembly as claimed in Claim 10, in which the body structure also includes an elongated body component, the mounting formations being connected to the body component, with the second end of the housing component being pivotally mounted on the body component to be pivotable about a transverse axis adjacent the second mounting formation, the housing component defining another passage through which the first section extends, the fuse being of the detonating type and being mechanically connected to the first mounting formation, to anchor a first end of the housing component to the body component, so that, in use, when the fuse fuses and detonates, the first end of the housing component is released from the body component and the housing component is pivotally displaceable relative to the body component, causing the first electrode to be pulled out of the dissipating passage upon displacement of the housing component

5 relative to the body structure, to extinguish an arc formed between the first and the second electrodes.

17. An assembly as claimed in Claim 9, in which the body structure also includes an elongated body component, the mounting formations being connected to the

0 body component, with the second end of the housing component being pivotally mounted on the body component to be pivotable about a transverse axis between the first and the second mounting formations, the first part of the arc dissipating device being fast with the first mounting formation and the second part of the arc dissipating device being fast with a first end of the housing, with the fuse being of the detonating type and being mechanically

5 connected to the first mounting formation by means of a flexible electrically conductive wire, to anchor the first end of the housing component to the body component with the first electrode and the second electrode spaced apart a suitable distance, so that, in use, when the fuse fuses and detonates, the first end of the housing component is released from the body component and the housing component is pivotally displaceable relative to the body

:0 component, causing, upon displacement of the housing component, the distance between the first electrode and the second electrode to increase, to dissipate an arc formed therebetween.

18. An assembly as claimed in Claim 4, in which the body structure includes a body component to which the mounting formations and the extra high voltage surge conducting device are secured, and a housing component in which the first section is housed, the housing component being pivotally mounted at a second end thereof on the body component to be pivotable about a transverse axis between the first and the second mounting formations, with the fuse being of the detonating type and being mechanically connected to the first mounting formation by means of a flexible electrically conductive wire, to anchor a first end of the housing component to the body component, so that, in use, when the fuse fuses and detonates, the first end of the housing component is released from the body component and the housing component is pivotally displaceable relative to the body component.

19. An assembly as claimed in Claim 18, which includes a surge arrestor for connection to earth, the surge arrestor being in series with the first and the second sections, the assembly also including a third mounting formation, the second mounting formation being located between the first and the third mounting formations, and with the surge arrestor being electrically connected to and extending between the second mounting formation and the third mounting formation.

20. An assembly as claimed in any one of Claim 17 to Claim 19 inclusive, in which the blocking arrangement includes a resistor in series with the coil.

21. An assembly as claimed in any one of Claim 2 to Claim 4 inclusive, in which the extra high voltage surge conducting device includes two electrodes which are spaced apart to define said air gap therebetween, a first of the electrodes defining a tubular passage, with a second of the electrodes being received in the passage defined by the first electrode, so that the air gap is substantially annularly shaped, being defined between a surface of the wall of the first electrode defining the passage and an outer surface of the second electrode.

22. An electrical installation, which includes an electrical protection assembly as claimed in any one of Claim 1 to Claim 21 inclusive.

23. An assembly as claimed in Claim 1 , substantially as herein described and illustrated.

24. An electrical protection assembly as claimed in Claim 22, substantially as herein described and illustrated.