Method of manufacturing an electrode for a surge arrester, electrode and surge arrester

Abstract

A method for manufacturing of an electrode of a surge arrester, an electrode and a surge arrester are disclosed. In an embodiment, the method includes positioning an electrode body in an electrochemical cell with and an electrolyte solution for a nickel deposition. The electrolyte solution includes at least one or more of magnesium sulphate, sodium sulphate and sodium chloride and electrolytically coating the electrode body with a coating to form the electrode for the surge arrester. The coating has nickel and the electrolyte solution is configured such that a surface of the coating includes a reduced wettability.

Claims

1. An electrode for a surge arrester, comprising: an electrode body; and a coating being electrically conductive, wherein the coating comprises nickel and an additive, wherein the coating has a surface with a reduced wettability, wherein the additive comprises sulphur, which effects the reduced wettability of the surface of the coating for a solder, and wherein the sulphur of the additive is present in the surface of the coating between 0.05 and 0.2 weight percent based on a total weight of the coating.

2. The electrode according to claim 1, wherein the coating is an electrolytically deposited layer.

3. The electrode according to claim 1, wherein the additive further comprises chlorine.

4. The electrode according to claim 3, wherein the chlorine of the additive is present in the surface of the coating between 0.1 and 0.3 weight percent based on a total weight of the coating.

5. The electrode according to claim 1, wherein the solder is a hard solder.

6. The electrode according to claim 1, wherein a contact angle formed by the solder at a temperature of 800 C. on the surface of the coating is greater than a contact angle of the solder formed on a nickel surface not comprising the additive.

7. The electrode according to claim 1, wherein the coating is free of Cu.

8. A surge arrester comprising the electrode according to claim 1.

9. A surge arrester electrode, comprising: an electrode body; and a coating being electrically conductive, wherein the coating comprises nickel and an additive, wherein the coating has a surface with a reduced wettability when the surge arrester electrode is soldered to a surge arrester insulator, wherein the additive comprises sulphur and/or chlorine, wherein, when the additive comprises sulphur, the sulphur is present in the surface of the coating between 0.05 and 0.2 weight percent based on a total weight of the coating, and wherein, when the additive comprises chlorine, the chlorine is present in the surface of the coating between 0.1 and 0.3 weight percent based on a total weight of the coating.

10. The surge arrester electrode according to claim 9, wherein the additive comprises sulphur and chlorine.

11. An electrode for a surge arrester comprising: an electrode body; and a coating being electrically conductive, wherein the coating comprises nickel and an additive, wherein the coating has a surface with a reduced wettability, wherein the additive comprises chlorine, which effects the reduced wettability of the surface of the coating for a solder, and wherein the chlorine of the additive is present in the surface of the coating between 0.1 and 0.3 weight percent based on a total weight of the coating.

12. The electrode according to claim 11, wherein the additive further comprises sulphur.

13. The electrode according to claim 12, wherein the sulphur of the additive is present in the surface of the coating between 0.05 and 0.2 weight percent based on a total weight of the coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Features which are described herein above and below in conjunction with different aspects or embodiments, may also apply for other aspects and embodiments. Further features and advantageous embodiments of the subject-matter of the disclosure will become apparent from the following description of the exemplary embodiment in conjunction with the figures, in which:

(2) FIG. 1A shows a schematic cross-sectional view of a single unit of a surge arrester.

(3) FIG. 1B shows schematically a portion of FIG. 1A in greater detail.

(4) FIG. 2 shows a schematic cross-section of a stacked surge arrester.

(5) FIG. 3 shows a schematic perspective view of a stacked surge arrester.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(6) Like elements, elements of the same kind and identically acting elements may be provided with the same reference numerals in the figures. Additionally, the figures may be not true to scale. Rather, certain features may be depicted in an exaggerated fashion for better illustration of important principles.

(7) FIG. 1A shows schematically a cross-section of a surge arrester 100 embodied with a single arrester unit. The surge arrester 100 comprises a first electrode 10 with a first electrode body 1 (see also below). The surge arrester 100 further comprises a second electrode 20 with a second electrode body 2 (see also below).

(8) The first electrode body 1 and the second electrode body 2 are, preferably, made of Cu or predominantly comprise copper. Preferably, the electrode bodies have a copper surface However, said electrode bodies may also comprise further electrode materials such as a nickel/iron (NiFe) alloy or compound.

(9) The first electrode body 1 and the second electrode body 2 are arranged symmetrically in FIG. 1A. The first electrode body 1, as well as the second electrode body 2, are configured to form a discharge or main gap 3 of the surge arrester. In the gap 3, the first electrode body 1 and the second electrode body 2 are spaced at a minimal distance from each other. The surge arrester 100 further comprises two insulators 4 or two parts of one insulator 4 which are shown in FIG. 1A. The insulators 4 may be made of a ceramic. The two insulators 4 laterally separate the first and the second electrode bodies 1, 2 in lateral areas beside the gap 3, i.e. left and right in the cross section of FIG. 1A. Originating from such an area, wherein the first electrode 1 and the second electrode 2 are separated by the insulators 4, the first and the second electrode bodies 1, 2 extend towards each other and/or towards an interior of the surge arrester 100. The first and the second electrode bodies 1, 2 are tapered in order to approach each other to form the gap 3.

(10) The surge arrester 100 further comprises an ignition aid 7 encompassing two parts arranged at the insulators 4 and at each lateral side of the gap 3. The ignition aid 7 may be arranged on or at the insulators 4 such that the gap 3 is arranged between said ignition aid or said parts. Between the first electrode body 1 and the second electrode body 2, as well as between the insulators 4, or as the case may be, the ignition aid 7, a gas may be arranged which may be electrically dischargeable by a current pulse or current load, caused by a lightning strike e.g., during an operation of the surge arrester 100. The gas or filling gas may comprise hydrogen (H.sub.2). In the case, wherein the first and second electrode bodies 1, 2 are made of a NiFe alloy, the H.sub.2 of the filling gas poses disadvantages as it may be absorbed by the NiFe electrodes and said electrodes may degenerate by said absorption.

(11) However, in the case that the first and the second electrode 1, 2 are made of copper, hydrogen is, preferably, applied as a filling or discharge gas as copper hardly absorbs hydrogen. Alternatively, nitrogen may be applied as a filling gas, wherein a larger arc or discharge voltage may be obtained during an operation of the surge arrester 100.

(12) The arrester 100 further comprises a cavity 9. The first and the second electrode bodies 1, 2 and the insulators 4 define the cavity 9. The surge arrester 100 or the cavity 9 of the surge arrester 100 is, expediently, filled with a gas 8. Said cavity 9 is further preferably sealed and/or configured to be gas-proof.

(13) The presented surge arrester 100 is, preferably, designed for an overvoltage or surge current protection of telecommunication devices against lightning strikes. The surge current capacity of the surge arrester may, thereby, be adjusted to a current of 4 kA and a wave form of 10/350 s. The first value of said specification may relate to the slope or increase duration of a DC current, while the second value (350 s) of said specification may relate to the half-life duration or half value period of the respective surge current pulse caused by the lightning strike.

(14) Preferably, the surge arrester 100 is provisioned for a protection of devices against DC currents.

(15) The ignition aid 7 may, particularly, ease or accelerate the process of gas discharging by a distortion of the respective electric field. Further, the average of the arc voltage or of the distribution of said voltage may be reduced by the provision of the ignition aid.

(16) The generation of heat or heat development during the described surge current loads on the surge arrester 100 may cause the electrode material of the mentioned electrode bodies 1, 2 to melt or evaporate. Such an evaporation can cause shortcuts in the surge arrester 100 and/or the narrowing of the gap 3. Thereby, the protection level of the surge arrester 100 may be increased due to the evaporation of electrode material, wherein the ignition aid 7 and/or the insulators 4 may be coated by said electrode material.

(17) FIG. 1B shows a part of the surge arrester 100 shown in FIG. 1A in greater detail. Particularly, it is shown that the first electrode body 1 and/or the second electrode body 2 may comprise or be coated with a layer or coating 6. Preferably, the coating 6 extends over the whole surface of the first and the second electrode bodies 1, 2. The coating 6 is, preferably, applied to or deposited onto the first and the second electrode bodies 1, 2 by means of an electrolytic method (see below) in order to form the first and the second electrode 10, 20 of each of the electrode bodies 1, 2, respectively. Said application or deposition may pertain to a plating process.

(18) The insulator 4 comprises a solder 5. The solder 5 may be a solder layer. In FIG. 1B, the solder 5 and the coating 6 are in contact, preferably soldered or brazed to each other such that the electrode bodies 1, 2 are mechanically connected to the insulator 4. The insulator 4 may be pre-coated or prefabricated with the solder 5. The solder 5 may be a hard solder such as an alloy of silver and copper. Preferably, the solder 5 is a eutectic compound comprising 72 at % of silver and 28 at % of copper. Said compound may have a melting point of or of about 780 C. During the fabrication of the surge arrester 100, the first and the second electrode 10, 20 are, preferably, hard soldered to the insulator 4 at a temperature of, e.g. 800 C.

(19) Prior to the soldering, the electrode bodies 1, 2 are preferably, coated with the coating 6. The coating 6 comprises nickel. Preferably, the coating 6 is a nickel coating. Preferably, the coating 6 is, further, a dark nickel coating.

(20) The electrode bodies 1, 2 are, preferably, electrolytically coated with the coating by means of an electrochemical cell (not explicitly shown) and an electrolyte solution (not explicitly shown) which is suitable or allows for a nickel deposition. Said coating process is, preferably, a special wet chemical electrolytic process.

(21) The electrode bodies 1, 2, may act as a cathode during the electrolytic deposition of the coating on the electrode bodies 1, 2.

(22) For the electrolytic deposition, the electrolyte solution, preferably, comprises at least one or more of magnesium sulphate such as MgSO.sub.4 with 7 parts H.sub.2O, sodium sulphate such as NaSO.sub.4 and/or sodium chloride (NaCl). Preferably, the electrolyte solution further comprises nickel sulphate hexahydrate such as NiSO.sub.4*6H.sub.2O and boric acid such as H.sub.3BO.sub.3. The nickel sulphate hexahydrate is, preferably, present at a concentration of or of about 230 g/l, while the boric acid is, preferably, present at a concentration of 40 g/l.

(23) The coating 6 is, preferably, chosen or deposited such that the surface (not explicitly indicated) of the coating 6 comprises a lower wettability for the solder 5 as compared to nickel or a reference nickel surface, preferably at a temperature at which the electrodes are soldered to the insulator 4 during a fabrication or manufacturing of the surge arrester 100.

(24) Preferably, the surfaces of the electrode bodies 1, 2 are made of copper.

(25) The coating is, expediently, electrically conductive, comprises metallic electrical properties and comprises, in addition to nickel, an additive which may comprise sulphur and chlorine. The lowering of the wettability of the surface of the coating for the solder may be achieved by the presence of the additive and/or the provision of the dark nickel for the coating of the respective electrode.

(26) The sulphur for the additive is, preferably, present in the surface of the coating between 0.05 and 0.2 weight percent. On the other hand, the chlorine in the additive is, preferably, present in the surface of the coating between 0.1 and 0.3 weight percent. Said percentages may be rendered by means of an element analysis, e.g. x-ray fluorescence. In this regard, the term in the surface may indicate that said elements are detectable in the coating (or a surface thereof) up or down to a thickness corresponding to the characteristic active sampling or detection thickness of said element analysis.

(27) Preferably, the surface of the coating comprises a lower free electron density as compared to a nickel or reference nickel surface.

(28) Preferably, the contact angle formed by the solder at a temperature of 800 C. or at that temperature at which the electrode is soldered to the insulator 4, on the surface of the coating 6, is greater than the contact angle of the solder formed on a nickel surface not comprising the additive and/or not being a dark nickel surface.

(29) Preferably, the coating is, furthermore, free of copper. Thereby, it may be avoided that the copper of the electrode melts or evaporates as a consequence of a lightning strike or a surge current or the respective thermal load. Nickel, on the other hand, does not evaporate that easily due to the greater melting point of nickel as compared to copper. The surface roughness of the coating may further be greater or smaller than the surface roughness of the reference nickel surface not comprising the additive and/or not being a dark nickel surface, for example. The coating may further comprise a thickness between 5 and 20 m, preferably between 6 and 10 m. The surface of the coating 6 may further be configured such that the wettability of the coating 6 or its surface for the solder 5 is reduced or lower than the reference nickel surface. The surface of the coating 6 thereby, preferably, inherently emerges by the above-mentioned electrolytic method.

(30) The coating 6, particularly the embodiment as dark nickel coating effects the reduced wettability of the solder 5 on the coating during the mentioned soldering such that said solder 5 does not flow or run towards a region of the gap 3 and the surge arrester 100 becomes leaky, e.g. at the lateral sides of the surge arrester 100, where the insulator 4 contacts the electrodes, respectively. Instead, as the viscosity or wettability of the solder 5 on the coating 6 is kept moderate and the advantages of a fairly high capability for surge currents or thermal loads can be exploited by the surge arrester 100.

(31) FIG. 2 shows a schematic view of a stacked surge arrester 100. In contrast to the one shown in FIG. 1A, the surge arrester comprises a plurality of arrestor units 50 in a stacked sequence. Exemplarily, three units 50 are shown. By means of the series of cascaded configuration, the possible operating voltages of the respective circuits of the surge arrester 100 can be increased. Particularly. The possible voltage of the circuit corresponds to the number of arrestor units multiplied by the arc discharge voltage of each arrestor unit 50 in the respective embodiment.

(32) FIG. 3 shows a perspective view of stacked surge arrester 100 comparable to the one shown schematically in FIG. 2. The surge arrester 100 comprises at least 4 arrester units 50 in a stacked sequence. The surge arrester device 100 comprises an octagonal shape and/or an octagonal front and end wall. The surge arrester 100 may further comprise one or more mounting elements (see bottom not explicitly indicated in FIG. 3) which allow for a mounting or fixation to a telecommunication device, for example.

(33) The scope of protection is not limited to the examples given herein above. The invention is embodied in each novel characteristic and each combination of characteristics, which particularly includes every combination of any features which are stated in the claims, even if this feature or this combination of features is not explicitly stated in the claims or in the examples.