JP4431660B2 - Improved clamping MOV surge arrester - Google Patents

Description

【００６１】
好適な実施形態としては、５０ナノ秒未満で大サージ電流（１,０００,０００アンペア超）を流す。好適な実施形態は、大径のＭＯＶ表面上で電流を均一に分布させることができる。好適な実施形態は、また、ＭＯＶからの迅速な熱伝達を実現することで、ＭＯＶの寿命を延ばすことができる。
【００６２】
次に図５及び図６を参照すると、サージアレスタ１の設置配線の好適な態様が示されている。サージアレスタ１は、地面（図示せず）に接続された接地ラグ５５を有するアルミニウム製バックパネル５６上に取り付けられる。４個の硬質のプラスチック製隔離絶縁器５３は、サージアレスタ１をアルミニウム製バックパネル５６から絶縁する。ナイロン製ボルト及びナット５４０は、プラスチック製隔離絶縁器５３をアルミニウム製バックパネル５６に固定する。
【００６３】
導電性ボルト１４には、呼称で８０アンペアのヒューズ５０が電気的に接続されている。ヒューズ５０は、スタッドブロック５１及びスタッドブロック延長５２に電気的に接続されている。中性導体５７は、図６に示した中性バス６４に接続する。
図６は、中性線６０を有する三相電力系統の典型的な配線構造である。位相１、位相２、位相３は、それぞれ符号６１，６２，６３を付されている。
【００６４】
次に図７を参照すると、同一の三相電力系統が、図６に示したものと同じサージアレスタ回路により保護された状態で示されている。別の実施形態である４個のＭＯＶを含むサージアレスタ７０が使用されている。サージアレスタ７０は、図１に示したものと同じエポキシ樹脂及びゴムコーティング構造を有する。
【００６５】
図８の説明に移ると、サージアレスタ１の好適な実施形態を用いた別の標準保護回路が示されている。アルミニウム製取付プレート２００には第一のアルミニウム製接触プレート１００が取り付けられている。ここでもアルミニウムは、熱を放散し易くする。各対の接触プレート１００,１２０には、ヒューズブロック２６０内のヒューズ２８０が直列に接続されている。ヒューズ２８０は、緩動ヒューズである。
【００６６】
ヒューズブロック２６０には、三相電流３１０，３２０，３３０が接続される。
各ヒューズブロック２６０には、信号装置へのリード線が取り付けられている。
この信号装置は、電球又はＬＥＤ（図示せず）でよい。信号装置は、特定のサージ除去装置が健全であるかどうかを見分けるために使用される。最後に、各ヒューズブロック２６０は、取付プレート２００に接続されて地面への接地接続部３４０を使用した接地プレート２２０に対して、電気的には絶縁された状態で取り付けられる。中性接続部３５０も設けられている。
【００６７】
以下は、サージアレスタ１の好適な実施形態を製造するのに必要な材料の詳細な説明と明細である。
【００６８】
（部品） 数量
アルミニウムプレート、3.63 x 3.63 x 1/4 2
ナイロンボルト：1/4 - 20 x 1 3/4 4
ナイロンナット：1/4 - 20 4
コーティングされたＭＯＶ 1
青銅ねじ：#10 x 32 x 5/8 FHSL 2
青銅ワッシャ：#10, SPLK 2
青銅ナット：#10-32 2
アルミニウム箔ディスク（１又は４のディスク不完全表面を矯正） 2
エポキシ樹脂、EVロバート・インコーポレーテッド（登録商標）：No. 51-40非着色 1
【００６９】
（一般注意事項）：
保護手袋は、ＭＯＶディスクの取り扱い中に摩耗すべきこと。
青銅ボルトには、３５インチ−ポンドのトルクを付与すること。
ナイロンボルトには、７インチ−ポンドのトルクを付与すること。
【００７０】
(製造)
１．
ａ）１０番のねじを３.６３ｘ３.６３プレートの中央孔に挿通する。１０番のワッシャとナットを締め付ける。
ｂ）３.６３ｘ３.６３プレートの各隅部の直径０.２６６インチの孔に１個のナイロンボルトを挿通する。
２．
ａ）３.６３ｘ３.６３プレートの中央に１個のアルミニウム箔ディスクを配置する。
＊品質検査：次の工程中に圧力の均一分布を確保すべく,クロスパターンを使用する。
ｂ）アルミニウムディスク上に１個のＭＯＶを中心決めして配置する。
ｃ）ＭＯＶ上に１個のアルミニウム箔ディスクを中心決めして配置する。
３．
ａ）各ＭＯＶ又はアルミニウムディスクの整合性を妨げないように注意しながら、３.６３ｘ３.６３プレート上の整合孔にナイロンボルトを挿通してＭＯＶ上に３.６３ｘ３.６３プレートを注意深く設置する。
＊品質検査：次の工程中に圧力の均一分布を確保すべく,クロスパターンを使用する。
ｂ）ナイロンナットでモジュールプレートを固定し、一般注意事項で明記したトルク値まで締め付ける。この最終トルク値は、二段階の締め付けで達成する。
＊次の工程中に全てのディスクが適切に着座したということを確認するためにモジュール組立体の目視検査を行う。
４．モジュールを光源に対して保持して、全ディスクがアルミニウムプレートと同一平面にあり、プレート、アルミニウム箔ディスク及びＭＯＶとの間に、空気間隙が存在しないことを確認する。
＊品質検査：プレートとＭＯＶとの間に光りが見える場合は、プレートを取り除き上述した指示に従いモジュールを再組み立てする。アルミニウム箔がＭＯＶの外縁部上に見えるときは、プレートを取り除き、上述した指示に従ってモジュールを再組み立てする。
５．モジュールの３つの側面をキャプトンテープ及びラテックスシーラントで封止する。無着色のエポキシ樹脂を製造者の書いた指示書に従って混合する。エポキシ樹脂をモジュール内に充填されるまでゆっくり注入する。
＊品質検査：気泡及び沈殿のため注入工程を厳密に監視しなければならない。
６．沈殿が終わって（約１０乃至１５分）モジュールが充填された時点で、プレート縁部と同じ高さになるまで余分なエポキシ樹脂を除去する。
７．エポキシ樹脂が硬化した時点で、キャプトンテープを除去し、エポキシ樹脂充填側を除きモジュールの外部から余分なエポキシ樹脂を全て取り除く。
【００７１】
表２には、サージアレスタ１及び/又は４個のＭＯＶを含む実施形態７０の典型的な動作特性を説明する。
【００７２】
【表２】

【００７３】
８５℃のＭＣＯＶは、周囲条件でのＭＣＯＶに等しいと仮定することができる。直流１mAでのＭＯＶ電圧は、交流５mAでの電圧の報告値より典型的には約５％小さい。
【００７４】
次に図９、図１０、図１１を参照すると、ＭＯＶケース９０は、単一のＭＯＶ組立体９１を収容している。
単一のＭＯＶ組立体９１は、図４に示したものと同様にＭＯＶ９２を挟持するプレート９３，９４から構成される。図４に示したエポキシ樹脂１２は、図１０では充填材９６としても使用される。位相導体９７は、好ましくは、図１１に最もよく示したようにプレート９４から外部ケース９５を通って延びるボルトである。接地導体９８は、好ましくは、プレート９３から外部ケース９５を通って延びるボルトである。外部ケース９５は、好ましくは硬質のプラスチックから形成される。
【００７５】
呼称寸法は、ｄ₁₀＝ｄ₁₁＝４.５０インチ（１１.４３cm）、ｄ₁₂＝１.２５インチ（３.１８cm）である。取付プレート９９は、ナットボルト組立体１００を用いて外部ケース９５に固定される。
ナット及びボルト組立体１００は、ＭＯＶケース９０を基板（図示せず）に固定するために使用することもできる。外部ケース上９５に堆積した埃、グリース又は水は、ＭＯＶ組立体９１の電気特性に影響しないことは理解されよう。一方、図１に示した実施形態では、同様の堆積がＭＯＶサージアレスタ１の電気特性を損なうことになる。
【００７６】
次に図１２、図１３を参照すると、三相ＭＯＶ組立体１２０が示されている。外部ケース１２１は、好ましくは硬質のプラスチックから形成される。取付ブラケット１２２は、取付孔１２３を有する。位相１接続プレート１２４は、コネクタ１２４０を有する。
位相２接続プレート１２５は、コネクタ１２５０を有する。位相３接続プレート１２６は、コネクタ１２６０を有する。接地導体１２７は、好ましくは、コネクタ１２７０を有する厚さ０.２５インチ（０.６４cm）のアルミニウムプレートである。
【００７７】
各ＭＯＶ組立体１３０は、図１のＭＯＶサージアレスタ１と同一且つ電気的に等価物である。ＭＯＶ１３１は、プレート１３２及び１３３の間に挟持され、挟持体は、充填物１３９９と同一のエポキシ樹脂１２を含む。
プラスチック製の仕切プレート１３９８は、構造的な剛性を付与する。プレート１３２は平坦であり、外部ケース１２１を貫通して接続プレート１２４，１２５，１２６を形成する。プレート１３３は屈曲してブラケット１３４を形成し、接地コネクタ１２７に取り付けるためのナット及びボルト組立体１３５を構成する。
呼称寸法は、ｄ₁₃＝６.７５インチ（１７.１５cm）、ｄ₁₄＝５.１７インチ（１３.１３cm）である。ここでもまた、外側ケース１２１上に堆積した埃、グリース又は水はＭＯＶ組立体の電気特性に影響することはない。
この実施例では、各ＭＯＶが、約3.１５インチ（約８０mm）の直径を有する。
【００７８】
次に図１４，１５を参照すると、別の実施形態である三相ブロック１４００が示されている。Ｇは接地、１は位相１電力、２は位相２電力、３は位相３電力、ｘはスペーサを表す。ＭＯＶ１４８１は、位相２乃至位相３を保護する。ＭＯＶ１４８２は位相３乃至接地を保護する。ＭＯＶ１４８３は、位相２乃至接地を保護する。ＭＯＶ１４８４は、位相１乃至位相２を保護する。
ＭＯＶ１４８５は、位相１乃至位相３を保護する。ナット及びボルト組立体１４８６は,三相ブロック１４００の構造的剛性を維持する。各ＭＯＶとプレート間の封止層は全て、図１に示した構造と同一であるが、好ましくは図１６に示した蒸着型ＭＯＶを使用する。互い違いに配置されて取り付けが容易な接続端部１４３０乃至１４３４により、コンパクトで低電圧（６６０Ｖまでの）のサージ保護モジュールが提供される。
【００７９】
以上、本発明を好適な実施形態に基づき説明してきたが、多くの修正及び変形を行うことが可能であり、その結果も依然として本発明の範囲内に在る。ここに開示した特定の実施形態に関しての限定は意図されておらず、また推定されるべきではない。
【００８０】
【発明の効果】
本発明の効果は、塵や湿気の堆積を含むプレート間の幾つかの要因により生じる短絡回路の可能性を除去するために、冷却機能とＭＯＶの表面接触を改善して、部品故障の危険を減少させる。更に、ＭＯＶサージアレスタをパッケージ化することで、均一な電流分布を実現すると共に、サージにより生成される熱の迅速な除去を達成し、且つ取り付けを容易にすることができる。また、どんな形の外部汚染でも早期クランプを許容しない単相及び三相用の単一のパッケージ内に、多数のＭＯＶをパッケージすることができ且つ個々を効果的に絶縁可能なＭＯＶ使用サージアレスタパッケージを提供することができる。
【００８１】
耐候性のケーシング内に、予めパッケージ化された単一ディスクＭＯＶサージアレスタを提供することで、１,０００,０００アンペアを超えるサージ電流に対応できると共に、最大ピーク電流に５０ナノ秒未満で反応することができる。
【００８２】
また、軟質プレート、エポキシ樹脂、誘電性ゴム被膜、及び箱型ケースを使用することにより、著しいサージアレスタ性能の改善が実現される。
従来技術は、雷のみに関係していたが、本発明では、ピークサージ電流でも通過電圧を装置平均故障間隔（ＭＴＢＦ）を減少させるレベルより、十分に低いレベルまでに制限することにより信頼性を維持することができる。加えて、電圧クランプを従来技術より低いレベルで開始することにより、信頼性の維持を更に確実なものとする。
【００８３】
以上、本発明では、その他様々な効果が期待でき優れたＭＯＶサージアレスタを提供することが出きることとなった。
【図面の簡単な説明】
【図１】単一のＭＯＶを含むサージアレスタの好適な実施形態の上方から見た一部破断斜視図。
【図２】図１のサージアレスタの正面図。
【図３】図１に示したサージアレスタの側面図。
【図４】図１に示したサージアレスタの分解組立図。
【図５】１２０／２４０Ｖ単相回路に接続されたサージアレスタの側面図。
【図６】三相サージアレスタ回路の平面図。
【図７】４個のＭＯＶサージアレスタモジュールを使用した三相サージアレスタの別の実施形態の平面図。
【図８】図６に示した三相サージアレスタの別の実施形態の平面図。
【図９】単一のＭＯＶケースの好適な実施形態の一部破断側面図。
【図１０】図９の線１０−１０に沿った断面図。
【図１１】図９に示した実施形態の上方から見た斜視図。
【図１２】三相ＭＯＶケースの好適な実施形態の上方から見た斜視図。
【図１３】図１２の線１３−１３に沿った断面図。
【図１４】三相モジュールの別の実施形態の側面図。
【図１５】図１４に示した実施形態の下方から見た斜視図。
【図１６】コーティングされたＭＯＶの平面図。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surge protector. In particular, the present invention discloses an improved surge arrester using a large diameter, single zinc oxide surge arrester disk sandwiched between a pair of contact plates.
[0002]
[Prior art]
Surge arresters are useful for protecting electronic circuits from extreme overrated transients. Such overrated transient currents can be caused by switching transient currents or by lightning strikes.
In particular, some surge arresters for high voltage operate due to damage of the surge arrester. This is not practical from an economic or functional standpoint for certain applications such as secondary or low voltage applications.
[0003]
One solution to the structure of surge arresters is the use of metal oxide varistors (hereinafter abbreviated as MOV). These MOVs are currently manufactured by many manufacturers, along with surge arresters that utilize them.
However, Reycom Corporation of California has developed a very high quality MOV that extends its utility for LEC. The powder includes small-diameter metal oxide particles that are uniformly distributed in the large-diameter primary metal oxide particles. By using a fine powder base for MOV, a more stable protection voltage can be obtained especially when slicing to various voltages. Tolerance is kept at ± 0.2%. The following patents assigned to Raychem represent the prior art.
[0004]
Koch et al., European Patent No. 0,229,464 (published 22 July 1987), for electrical components reinforced against explosions by wrapping curable sheet material around spaced apart parts. Shows a fragile housing. The wrapping material is cured by ultraviolet radiation. This material holds together the fragments that have been crushed by overvoltage.
[0005]
Koch et al., European Patent No. 0,230,103 (published July 29, 1987) discloses a surge arrester in which circular varistor blocks are stacked for larger voltages.
[0006]
Thompson et al. US Pat. No. 5,039,452 (August 1991) discloses a precursor powder for a metal oxide varistor (MOV) of zinc oxide.
[0007]
Mikuli et al. PCT Patent No. WO 91/14304 (UK 91/00405) (published 19 September 1991) has 8 stacked varistor blocks that penetrate the stack to detect component failures. A surge arrester provided with an optical fiber cable is disclosed.
[0008]
Wiseman et al., PCT Patent No. WO 93/26017 (US 93/05679) (published 23 December 1993), MOV valve bodies are stacked along the longitudinal axis, and the MOV valve bodies are disposed between conductive terminals. Discloses a method of manufacturing a voltage arrester compressed in the above.
[0009]
Another solution for low voltage applications of MOV surge arresters is realized by Lee Dynatech of Tampa, Florida and used in Lightning Eliminator & Consultants Inc. (LEC) TVSS products. Wagon wheel (registered trademark) technology. This technique is based on US Pat. No. 4,875,137 to Rozansky et al. (October 1, 1989). LEC TVSS products utilize low or medium sized individually fused parallel metal oxide varistors (MOVs).
[0010]
Carpenter II, US Pat. No. 5,519,564 (1996), discloses a pinching block package for mounting a plurality of MOVs in parallel and spaced apart. Thereby, the surge is distributed to each MOV. Each MOV in the sandwich must be matched to the clamp voltage setting to prevent any one MOV from being clamped too early and taking on the entire surge.
[0011]
The Ohio Brass Company in Mansfield, Ohio, manufactures a strong-distribution surge arrester as Dynavar® PDV-100. Normal operating voltage is over 2400V with a clamp voltage of about 3000V. The single MOV is accommodated in a ribbed EPM rubber housing and an epoxy resin glass fiber packaging cylindrical container. Here, there is no suggestion that a single MOV is held in the holding block structure in the power transmission region.
[0012]
One related art document is U.S. Pat. No. 5,088,001 (1992) to Yawaski et al. The device as shown in FIG. 2 is used for high voltage distribution and surge protection. The outer rubber body has a conductive outer layer to allow surface transients to flow to the ground to protect personnel. A pair of thin metal end plates are used to contact one or more high voltage MOVs stacked in series, each plate being 1 inch thick (2.54 cm) and 3/4 inch in diameter (1 .91 cm).
[0013]
A conductive adhesive is used to correct surface defects. This adhesive decomposes at approximately the same peak current rating as MOV, and in the case of 40 mm MOV, it decomposes at 30,000 amperes (model number V131CA40, CA series). Structural rigidity is provided by a non-conductive inner epoxy and outer rubber shell. The use of the MOV and the housing is for the purpose of self-destructing without exposing the personnel to danger during a damage surge such as a lightning strike. The use of the device is limited to the primary distribution system of high voltage, ie 2,000-33,000V.
[0014]
[Problems to be solved by the invention]
There are several problems with MOV surge arresters. One problem described in some of the above-mentioned patents is that MOVs often explode when dealing with excessive transient energy. To make this problem even more difficult, the MOV is different when the MOVs are parallel, as in Carpenter II's US Pat. No. 5,519,564 and the Wagon Wheel® technology described above. The problem is that it can have a clamping voltage.
[0015]
Thus, a greater proportion of surge current than expected would flow through a single MOV. As a result, the part of the parallel circuit is destroyed. The destruction of a single MOV can cause a chain reaction of similar individual MOV overloads, and ultimately the entire parallel circuit can be destroyed. When MOVs are stacked in series, such a failure does not stop at the deterioration, but stops the entire surge arrester.
[0016]
The prior art uses wires to connect between MOVs and to MOVs in order to increase the energy handling performance of a single assembly. These wires introduce inductance that delays the reaction time and causes variations in response time.
In addition, these wires bring a single point into contact with the MOV surface, thus concentrating surge energy on a very limited portion of the wire connection. As a result, the transmission of surge energy between the wire and the MOV is limited and again becomes a serious failure condition, burning at that point and causing uneven distribution of the surge energy to the MOV surface.
[0017]
The present invention solves all of the problems described above. For applications in low voltage circuits, a soft metal disc is used to reduce the contact resistance, and a single, relatively large diameter MOV, made by order, is sandwiched between the two contact plates. Although low voltage is the prospect of up to about 660V, are not limited to, be in the commonsense range to those skilled in the art.
The new casing holds either a single MOV sandwich for single phase or a triple MOV sandwich for three phases. The casing is pre-mounted on the mounting bracket to facilitate installation by the end user on the busbar or in a dedicated container. The outer plastic of the casing prevents arcing and short circuits caused by the accumulation of dust and grease on the MOV sandwich plate surface.
[0018]
Surge arresters (protectors) are necessary to protect electronic and electrical equipment. Its normal purpose is to prevent immediate loss due to abnormal overvoltage. However, the decline in long-term reliability is virtually ignored.
Despite the possibility of reduced reliability, the mean time between failures (MTBF) has increased significantly, especially in areas with thunderous activity and unstable power sources.
Studies have shown that over 50% of voltage anomalies in metropolitan areas significantly reduce the mean time between failures of electronic systems. This results in device loss that is not usually known as a “random failure”. These types of failures often cause greater losses than failures caused by lightning itself.
[0019]
All the prior arts have been configured to handle only lightning. In order to prevent a decrease in reliability, the requirements for the protector performance become extremely strict.
First, the initial protection or clamp voltage needs to be set much lower than with lightning protection alone. Furthermore, the clamp ratio (ratio of peak current to initial voltage) must be set much lower than for lightning protection alone. Also, the maximum surge current needs to be set much higher than the standard or reference.
[0020]
To achieve the above objective, the protector can dissipate about 10 times more energy (joules) and deliver about 10 times the surge current (amperes) compared to that required only for lightning protection. It must be possible.
[0021]
Conventional protectors using MOVs are configured to accommodate a limited amount of surge current and surge energy. This is limited by the size and number of MOV wafers used in parallel for each phase. The MOV wafer thickness is determined by the operating voltage, and the maximum surge current is determined by the diameter. The thickness of the conductive coating limits the reaction time in the prior art. Because of these limitations, an appropriate number of wafers selected to meet the above criteria need to be collimated by the present technique.
[0022]
There are two problems associated with placing MOVs in parallel. That is, the clamp voltages fluctuate over a range of at least ± 5%, resulting in non-uniform load sharing and the use of wire inductance to make the connection.
These are discussed in Carpenter US Pat. No. 5,519,564, which discloses a method for parallelizing MOV wafers that overcomes the above-mentioned problems. Although this method worked as expected, it has been found that the effect is limited at high energy levels due to the MOV and plate coupling configuration, tight air gap and fusing constraints. Prior art limitations have been overcome by the embodiments presented in this patent.
[0023]
The present invention is novel, useful and non-obvious for Yawasky and all known prior art because secondary power applications at low voltage present different problems overall.
The present invention is configured to extend the lifetime of the MOV by supporting over 800,000 amperes.
The present invention is configured to prevent self-destruction and extend its reliability.
The present invention is structurally connected by nuts and bolts and optionally has an outer rigid plastic box.
The present invention uses, in particular, a new, thin, low voltage, high surge current, large diameter deposited coating MOV manufactured for voltage systems up to 660V as secondary commercial voltage.
[0024]
The present invention provides a configuration that withstands current surges caused by lightning and self-destructs by maximizing heat transfer and low path impedance. Since Yawasky cannot conventionally handle a primary high voltage up to 33,000 V with a single MOV, the MOVs are stacked to meet the high voltage requirement. Yawasky's high-voltage small-diameter disks have low impedance due to their small diameter. Although Yawaski's conductive epoxy resin yields at 30,000 amps, the present invention works with a “soft” metal disk to make contact between the conductive plate and the MOV, By using a vapor-deposited film, it is possible to handle up to 800,000 amps or more. The present invention protects and extends the life of both the circuit and the MOV assembly.
[0025]
The present invention uses zinc oxide MOVs manufactured from conventional methods, although manufactured or inferior in effect from the improved manufacturing method disclosed in the '452 patent. The preferred embodiment here is a single thin zinc oxide MOV [0.061 (0) sandwiched between a pair of contact plates and having a thin deposited layer and a width of 3.5 inches (8.89 cm) or greater. .155 cm) to 0.500 inch (1.27 cm)].
This structure does not require a single MOV match, thus extending the life of the surge arrester and the equipment protecting it. Also, with this structure, the multi-module surge arrester with a small number of parts can have an energy handling function. The main application is for use at secondary voltages up to at least 4160 Vrms for home and industrial use.
Alternatively, rather than using a vapor deposited coating, the present invention sandwiches the MOV between two or more soft metal contact plates and connects the assembly with non-conductive nuts and bolts to apply tension.
[0026]
The present invention is an extension of the prior art as disclosed in US Pat. No. 5,519,567. The prior art presented an improved concept for placing MOVs in parallel. However, performance was limited due to some embodiments and did not include very large MOV wafers.
The present invention eliminates these limiting factors and realizes a unique form of circuit storage. The present invention can also use very large diameter disks that are sized to accommodate all possible surge energy and to function in some overcurrent conditions.
[0027]
Although the prior art was concerned only with lightning, the present invention maintains reliability by limiting the passing voltage to a level well below the level that reduces the device mean time between failure (MTBF) even at peak surge currents. can do. In addition, reliability is further ensured by starting the voltage clamp at a lower level than in the prior art.
[0028]
The main aspect of the present invention is to improve the cooling function and the surface contact of the MOV to eliminate the possibility of short circuits caused by several factors between the plates including dust and moisture build-up, and the risk of component failure. And a MOV surge suppressor package pre-stored in a plastic case.
[0029]
Another aspect of the present invention is to package the MOV surge arrester to achieve uniform current distribution, to achieve rapid removal of heat generated by the surge, and to facilitate installation. .
[0030]
Another aspect of the present invention is that multiple MOVs can be packaged in a single package for single and three phases that do not allow early clamping of any form of external contamination and can be effectively isolated individually. MOV surge suppressor package is provided.
[0031]
Another aspect of the present invention is capable of handling surge currents in excess of 1,000,000 amps, can respond to maximum peak currents in less than 50 nanoseconds, and is prepackaged in a weather resistant casing. Another object is to provide a single disk MOV surge arrester. High peak current adaptability is required to maintain reliability.
[0032]
Another aspect of the invention corrects surface defects in the MOV by forming a thin vapor deposited film on the MOV surface and / or uses a soft metal “washer” that fits between the sandwich plate and the MOV film. That is.
[0033]
The present invention also presents an improved method that facilitates the connection between the outer conductive plate and the MOV wafer. In addition, a method is presented that eliminates the possibility of arcing between the outer plates.
[0034]
The present invention also presents a fusing method that satisfies the requirement that an extremely high surge current is passed but the circuit is opened without explosive force when necessary. In addition, a method for analyzing the requirements of a protector that satisfies the configuration of the reliability protection assembly is presented.
[0035]
The present invention teaches maintaining substantially perfect contact over the entire surface of the MOV wafer while maintaining the same contact pressure level over the entire MOV surface.
The above-mentioned MOV sandwiching body may be previously accommodated in an outer plastic casing (box) having a conventional mounting bracket. The MOV clamping body is covered with an epoxy resin molding inside the outer plastic casing.
[0036]
[Means for Solving the Problems]
The present invention is a surge arrester used at a low voltage, and is supported in the space between a pair of conductive plates having a parallel spatial position with a space in between, and the conductive plate. A large-diameter, thin-thick MOV that makes conductive contact with each of the plates, a non-conductive epoxy resin that fills the space, and a dielectric coating that encloses the plate and the epoxy resin. Thus, by the power connection to the pair of conductive plates, surge protection against current is achieved without self-destruction by surge current across the MOV,
Furthermore, it is basically to provide a surge arrester with soft conductive disks provided on both sides of the MOV in order to correct surface defects.
[0037]
Further, instead of the soft conductive disk, thin conductive vapor deposition films are formed on both sides of the MOV.
[0038]
By using a soft plate, epoxy resin, dielectric rubber coating, and box-type case, significant surge arrester performance is achieved.
The epoxy resin prevents moisture from reaching the MOV, dissipates heat faster than air, increases the breakdown voltage between the contact plates, and further increases the mechanical strength of the surge arrester to suppress vibration degradation. The dielectric rubber coating also prevents moisture from entering the MOV, helps keep the surge arrester clean, and prevents arcing at corners where dust and the like are likely to accumulate.
[0039]
The preferred embodiment teaches the use of a large diameter disk with virtually no practical diameter limitations. In a sandwich block assembly, a single very large wafer can actually function well. This eliminates the non-uniform distribution of energy that often occurs with parallel wafer configurations.
[0040]
Further, the present invention is a surge arrester used at a low voltage, and a pair of conductive plates having a parallel spatial relationship with a space in between, and the space between the conductive plates. A large, thin single MOV that is supported and in conductive contact with each of the plates; a non-conductive epoxy resin that fills the space; and a dielectric coating that encloses the plate and the epoxy resin; By this, the power connection to the pair of conductive plates achieves surge protection against current without self-destructing with a surge current of 1,000,000 amperes or more across the MOV, and surface defects. A thin conductive deposition film formed on both sides of the MOV to correct the distortion, and a non-conductive nano film provided at each corner of the conductive plate to bond the plate and apply tension. A surge arrester having a nut and a bolt is provided.
[0041]
The present invention is also a three-phase surge arrester block for systems up to 660 volts,
A plurality of at least eight parallel spaced apart conductive plates, including at least two ground plates and a pair of plates for each phase, to connect the first, second, third phase and ground to them A surge plate of at least 1,000,000 amps sandwiched between a conductive plate having at least one staggered plate and a continuous plate to provide surge protection between phases and between phase and ground A MOV having a small thickness and large diameter to withstand, a non-conductive epoxy resin that fills all gaps between the plates, a dielectric coating that encloses the plates, and applying tension to the plates In order to provide a three-phase surge arrester block, a non-conductive nut and bolt provided at each corner of the conductive plate are provided.
[0042]
Other solutions of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings, which form a part hereof. Like reference numerals designate corresponding parts in the several drawings.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
Before describing the disclosed embodiments of the present invention in detail, it is understood that the present invention is not limited to the specific details shown in the application, as other embodiments are possible. I want you to understand. Also, the terminology used here is for the purpose of explanation and not for limitation.
[0044]
Referring first to FIGS. 1 and 4, one embodiment of a single MOV surge arrester 1 is shown. The contact plates 2, 3 are preferably made of aluminum. These plates are joined by nylon nuts and bolts 4 at the respective corners 5, 6, 7, 8. MOV9 has a nominal diameter of 3.12 inches (7.92 cm).
The MOV 9 is sandwiched between a pair of aluminum disks 10 and 11 in order to correct the surface defects. These discs may also be formed from a dense metal sponge material.
[0045]
In the preferred embodiment, the disks 10, 11 are removed. In order to correct surface defects, a thin conductive film is formed on the surface of the MOV as shown in FIG.
The low temperature arc deposition (LTAVD) method was developed in Boulder, Colorado. In 1981, Vapor Technologies of Boulder, a division of Masco Corporation, developed the LTAVD method along with other thin film coating technologies.
The company was incorporated in 1988, and the first major commercialization of methods and equipment began in 1989.
[0046]
The LTAVD method forms a variety of functional and decorative metal coatings on virtually any substrate, from metals to plastics. The LTAVD method involves decorative styling and functional parts for automobiles, medical devices and instruments, EMI / RFI / ESD shields on plastic electronic housings, functional coatings for outer space, and household metal products, jewelry and plastics. Used for decorative coating.
It goes without saying that these objects have a wide range of shapes, dimensions and configurations.
[0047]
The LTAVD method is a physical vapor deposition method that employs a high current, low voltage arc to substantially evaporate the conductive material. The vapor deposition material is formed as a cylindrical source on which an electric arc is ignited. This vapor deposition method is performed in a highly controlled vacuum to deposit a dense thin film coating layer with adhesion.
[0048]
The LTAVD method has many advantages over other physical vapor deposition techniques and has advantages not found in chemical vapor deposition. The LTAVD coating has extremely strong adhesion and wear resistance and corrosion resistance. In addition, the LTAVD method can be coated at room temperature or higher, and does not apply a considerable amount of heat energy (heat) to the substrate. Heat is harmful to each part, and may deteriorate the tempering degree or cause deformation or change in crystal structure.
[0049]
This method is extremely productive and the deposition is performed over a 360 degree range rather than a 180 degree range. Therefore, the part in the coating is always in a coating plasma state, which is extremely advantageous in terms of film quality and deposition rate.
The electrodes can be formed into any shape necessary to “fit” the part in the coating. If a planetary jig is not feasible, the electrodes may be formed so that the substrate can be coated without moving the substrate, as in the case of a pipe that coats the inside and outside with a single electrode.
[0050]
However, if necessary, both the substrate and the electrode can be moved. The electrode can be manufactured from a solid-phase sintered cold-pressed powder ingot of metal, alloy or carbon grade material. Since there is little waste heat and low temperature radiation, this method can deposit a high melting point material on a substrate at a low melting point.
Therefore, a high melting point material such as tungsten (3410 ° C.) can be deposited on the plastic film without using a cooling radiator and without damaging the substrate. The energy of metal ions emitted from the electrode is high (60 to 100 electron volts / ion). The ionization rate is extremely good, exceeding 90%, and good mechanical adhesion can be obtained even when the substrate temperature is the ambient temperature.
[0051]
When the substrate is heated, good mechanical adhesion occurs depending on the substrate. Since the temperature rise does not interfere with this method, the substrate temperature can be adjusted throughout.
As the arc moves over the electrode surface, its speed is adjustable. The coating range can be fine-tuned from a narrow range to a full application range of 360 degrees. The uniformity of the coating is obtained by the uniformity of arc movement across the electrode surface, and the depleted electrode appears as if it is uniformly eroded or milled.
The coating speed and uniformity are very good. The deposition rate is fast. The film thickness varies from 300 angstroms to several mils depending on the specifications.
The deposition rate is inversely proportional to the distance. In the case of high melting point and high density metals and ceramics, the deposition rate is slow. Nickel erosion rates are greater than 1 gram per minute per electrode. For thin film processes, a typical uniformity specification is ± 5%. Due to the high deposition rate, adaptability to large target dimensions and large vacuum chambers, a wide range or large volume can be uniformly coated.
[0052]
Alloy coatings can also alloy dissimilar materials using the LTAVD method. This method can be used to deposit materials that are not commercially available. For this purpose, it is necessary to first synthesize the target and then to perform vapor deposition using the LTAVD method. This is useful for titanium / aluminum and other compounds having different melting points and vaporization points.
[0053]
The purity of the vapor deposition material is the same as the starting material. Alloys maintain their composition throughout the coating process. Ceramic materials can be synthesized by vaporizing a metal or alloy in the presence of a low-temperature reaction gas, resulting in materials such as titanium carbonitride (TiCN) and titanium oxide. Pure carbon can also be vaporized.
[0054]
The LTAVD method has also been used to coat substrates that cannot be heated beyond hundreds of degrees, such as epoxy resin / metal composites, substrates with complex surface shapes, and the like. The coating layer includes various metals and reacted metal nitrides, carbides and oxides. These coating layers solve the problems caused by erodible and oxidizing hot gases, acids, corrosives, organic compounds and molten materials.
[0055]
A preferred embodiment of the MOV is indicated by reference numeral 1600 in FIG. The top surface (and the same bottom surface) 1601 is coated to a 1/16 inch (0.159 cm) outer perimeter 1602. The outer edge 1603 is not coated. The coating is preferably a copper coating having a thickness of 10 microns or more by the LTAVD method. The non-conductive epoxy resin 12 fills the entire space between the contact plates 2 and 3.
[0056]
The epoxy resin is preferably No. 51-41 by EV Robert Incorporated.RTM. R. Also known as Epoxy Encapsulate 2651-40 “Stycast” (registered trademark) by Grace & Company.
The epoxy resin 12 prevents moisture from reaching the MOV 9, dissipates heat faster than air, increases the breakdown voltage between the contact plates 2 and 3, and further increases the mechanical strength of the surge arrester 1 to vibrate. Suppress deterioration. Air has a breakdown voltage of 3 KV / mm compared to 20 KV / mm for epoxy resin 12.
[0057]
The dielectric sealant 13 covers the entire outside of the surge arrester 1. The dielectric sealant 13 is preferably a rubber having a strength of 2600 V / mm. In the best mode, seven spray coats of Loctite® are used to obtain a coating of about 5 mm. The dielectric sealant 13 prevents moisture from entering the MOV 9, helps keep the surge arrester 1 clean, and prevents arcs from occurring at the corners 5, 6, 7, and 9 where dust and the like tend to accumulate.
The conductive bolt 14 is embedded in the countersink of the inner surface 15 of the contact plate 3 in order to connect the conductor and the nut 16.
[0058]
2 and 3, the nominal dimension is d ₁ = 3.73 inches (9.47 cm),
d ₂ = 3.12 inches (7.92 mm), d _Three = 0.25 inch (0.64 mm), d _Four = 0.74 (1.88 mm).
A preferred embodiment of the MOV is shown in FIG. 16 and is used in place of the MOV 9 and the disks 10 and 11 of FIGS.
In the assembly of FIG. 1, the preferred embodiment assembly using MOV 1600 is used in commercial power distribution equipment up to 660V with a single MOV, each on a 220V leg.
[0059]
Raychem® forms a preferred embodiment of a thin MOV as shown in Table 1. The low voltage MOV disk slice of the present invention is standardized on varistor characteristics using a protection level of 2.2 (peak voltage = 2.2 × applied voltage rms).
The switch voltage means a clamp voltage. The height tolerance is ± 0.05 mm.
[0060]
[Table 1]

[0061]
In a preferred embodiment, a large surge current (greater than 1,000,000 amps) is applied in less than 50 nanoseconds. Preferred embodiments can distribute the current evenly over a large diameter MOV surface. The preferred embodiment can also extend the life of the MOV by providing rapid heat transfer from the MOV.
[0062]
Next, referring to FIGS. 5 and 6, a preferred embodiment of the installation wiring of the surge arrester 1 is shown. The surge arrester 1 is mounted on an aluminum back panel 56 having a ground lug 55 connected to the ground (not shown). Four hard plastic isolation insulators 53 insulate the surge arrester 1 from the aluminum back panel 56. Nylon bolts and nuts 540 secure the plastic isolator 53 to the aluminum back panel 56.
[0063]
The conductive bolt 14 is electrically connected with a fuse 50 having a name of 80 amperes. The fuse 50 is electrically connected to the stud block 51 and the stud block extension 52. The neutral conductor 57 is connected to the neutral bus 64 shown in FIG.
FIG. 6 is a typical wiring structure of a three-phase power system having a neutral wire 60. Phases 1, 2 and 3 are denoted by reference numerals 61, 62 and 63, respectively.
[0064]
Referring now to FIG. 7, the same three-phase power system is shown protected by the same surge arrester circuit as shown in FIG. In another embodiment, a surge arrester 70 including four MOVs is used. The surge arrester 70 has the same epoxy resin and rubber coating structure as shown in FIG.
[0065]
Turning to the description of FIG. 8, another standard protection circuit using a preferred embodiment of the surge arrester 1 is shown. A first aluminum contact plate 100 is attached to the aluminum attachment plate 200. Again, aluminum facilitates heat dissipation. A fuse 280 in the fuse block 260 is connected in series to each pair of contact plates 100 and 120. The fuse 280 is a slow-moving fuse.
[0066]
Three-phase currents 310, 320, and 330 are connected to the fuse block 260.
Each fuse block 260 is provided with a lead wire to the signal device.
This signaling device may be a light bulb or LED (not shown). The signaling device is used to determine whether a particular surge relief device is healthy. Finally, each fuse block 260 is attached to the ground plate 220 connected to the mounting plate 200 and using the ground connection 340 to the ground in an electrically insulated state. A neutral connection 350 is also provided.
[0067]
The following is a detailed description and specification of the materials necessary to manufacture a preferred embodiment of the surge arrester 1.
[0068]
(Parts) Quantity
Aluminum plate, 3.63 x 3.63 x 1/4 2
Nylon bolt: 1/4-20 x 1 3/4 4
Nylon nut: 1/4-20 4
Coated MOV 1
Bronze screw: # 10 x 32 x 5/8 FHSL 2
Bronze washer: # 10, SPLK 2
Bronze nut: # 10-32 2
Aluminum foil disc (corrects the disc imperfect surface of 1 or 4) 2
Epoxy resin, EV Robert Incorporated (registered trademark): No. 51-40 Uncolored 1
[0069]
(General notes):
Protective gloves should be worn when handling MOV discs.
Bronze bolts should be torqued 35 inches-pounds.
Nylon bolts should be torqued 7 inches-pounds.
[0070]
(Manufacturing)
1.
a) Insert No. 10 screw through the center hole of the 3.63 x 3.63 plate. Tighten the number 10 washer and nut.
b) Insert one nylon bolt through a 0.266 inch diameter hole in each corner of the 3.63 x 3.63 plate.
2.
a) Place one aluminum foil disc in the center of the 3.63 x 3.63 plate.
* Quality inspection: A cross pattern is used to ensure a uniform distribution of pressure during the next process.
b) A single MOV is centered on the aluminum disk.
c) Center and place one aluminum foil disc on the MOV.
3.
a) Carefully install the 3.63 × 3.63 plate on the MOV by inserting nylon bolts through the alignment holes on the 3.63 × 3.63 plate, taking care not to interfere with the alignment of each MOV or aluminum disk.
* Quality inspection: A cross pattern is used to ensure a uniform distribution of pressure during the next process.
b) Fix the module plate with a nylon nut and tighten it to the torque value specified in the general precautions. This final torque value is achieved in two stages of tightening.
* Perform a visual inspection of the module assembly to ensure that all disks are properly seated during the next step.
4). Holding the module against the light source, ensure that all discs are flush with the aluminum plate and that there is no air gap between the plate, the aluminum foil disc and the MOV.
* Quality inspection: If there is light between the plate and the MOV, remove the plate and reassemble the module according to the instructions above. When the aluminum foil is visible on the outer edge of the MOV, remove the plate and reassemble the module according to the instructions described above.
5). The three sides of the module are sealed with capton tape and latex sealant. Mix the uncolored epoxy resin according to the manufacturer's instructions. Slowly inject the epoxy resin until it is filled into the module.
* Quality inspection: The injection process must be closely monitored due to air bubbles and precipitation.
6). When settling is complete (about 10-15 minutes) and the module is filled, the excess epoxy is removed until it is level with the plate edge.
7). When the epoxy resin is cured, the capton tape is removed, and all of the excess epoxy resin is removed from the outside of the module except for the epoxy resin filling side.
[0071]
Table 2 describes exemplary operating characteristics of an embodiment 70 including a surge arrester 1 and / or four MOVs.
[0072]
[Table 2]

[0073]
It can be assumed that the 85 ° C. MCOV is equal to the MCOV at ambient conditions. The MOV voltage at 1 mA DC is typically about 5% less than the reported voltage at 5 mA AC.
[0074]
Next, referring to FIGS. 9, 10, and 11, the MOV case 90 contains a single MOV assembly 91.
The single MOV assembly 91 is composed of plates 93 and 94 that sandwich the MOV 92 in the same manner as shown in FIG. The epoxy resin 12 shown in FIG. 4 is also used as the filler 96 in FIG. The phase conductor 97 is preferably a bolt that extends from the plate 94 through the outer case 95 as best shown in FIG. The ground conductor 98 is preferably a bolt extending from the plate 93 through the outer case 95. The outer case 95 is preferably formed from hard plastic.
[0075]
The nominal dimension is d _Ten = D ₁₁ = 4.50 inches (11.43 cm), d ₁₂ = 1.25 inches (3.18 cm). The mounting plate 99 is fixed to the outer case 95 using the nut bolt assembly 100.
The nut and bolt assembly 100 can also be used to secure the MOV case 90 to a substrate (not shown). It will be appreciated that dust, grease or water deposited on the outer case 95 will not affect the electrical characteristics of the MOV assembly 91. On the other hand, in the embodiment shown in FIG. 1, similar deposition will impair the electrical characteristics of the MOV surge arrester 1.
[0076]
Referring now to FIGS. 12 and 13, a three-phase MOV assembly 120 is shown. The outer case 121 is preferably formed from hard plastic. The mounting bracket 122 has a mounting hole 123. The phase 1 connection plate 124 has a connector 1240.
The phase 2 connection plate 125 has a connector 1250. The phase 3 connection plate 126 has a connector 1260. The ground conductor 127 is preferably a 0.25 inch (0.64 cm) thick aluminum plate with a connector 1270.
[0077]
Each MOV assembly 130 is identical and electrically equivalent to the MOV surge arrester 1 of FIG. The MOV 131 is sandwiched between the plates 132 and 133, and the sandwich body includes the same epoxy resin 12 as the filler 1399.
The plastic partition plate 1398 provides structural rigidity. The plate 132 is flat and penetrates the outer case 121 to form connection plates 124, 125, and 126. The plate 133 is bent to form a bracket 134 and constitutes a nut and bolt assembly 135 for attachment to the ground connector 127.
The nominal dimension is d ₁₃ = 6.75 inches (17.15 cm), d ₁₄ = 5.17 inches (13.13 cm). Again, dust, grease or water deposited on the outer case 121 does not affect the electrical properties of the MOV assembly.
In this example, each MOV has a diameter of about 3.15 inches (about 80 mm).
[0078]
14 and 15, another embodiment, a three-phase block 1400, is shown. G represents ground, 1 represents phase 1 power, 2 represents phase 2 power, 3 represents phase 3 power, and x represents a spacer. MOV 1481 protects phase 2 to phase 3. MOV 1482 protects phase 3 to ground. MOV 1483 protects phase 2 to ground. MOV 1484 protects phase 1 or phase 2.
MOV 1485 protects phase 1 to phase 3. Nut and bolt assembly 1486 maintains the structural rigidity of three-phase block 1400. The sealing layers between each MOV and the plate are all the same as the structure shown in FIG. 1, but preferably the vapor deposition type MOV shown in FIG. 16 is used. The connection ends 1430-1434, which are staggered and easy to install, provide a compact, low voltage (up to 660V) surge protection module.
[0079]
Although the present invention has been described based on the preferred embodiments, many modifications and variations can be made and the results still remain within the scope of the present invention. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred.
[0080]
【The invention's effect】
The effect of the present invention is to improve the cooling function and the surface contact of the MOV in order to eliminate the possibility of short circuit caused by several factors between the plates including dust and moisture build-up, reducing the risk of component failure. Decrease. Furthermore, by packaging the MOV surge arrester, a uniform current distribution can be achieved, rapid removal of heat generated by the surge can be achieved, and installation can be facilitated. Also, MOV surge arrester package that can package multiple MOVs in single package for single phase and three phase that do not allow early clamping with any form of external contamination and can effectively isolate each one Can be provided.
[0081]
Providing a pre-packaged single disk MOV surge arrester in a weatherproof casing can handle surge currents in excess of 1,000,000 amps and reacts to maximum peak currents in less than 50 nanoseconds be able to.
[0082]
In addition, by using a soft plate, an epoxy resin, a dielectric rubber coating, and a box-type case, a significant improvement in surge arrester performance is realized.
Although the prior art related only to lightning, the present invention limits reliability by limiting the passing voltage to a level that is sufficiently lower than the level that reduces the device mean time between failure (MTBF) even at peak surge currents. Can be maintained. In addition, reliability is further ensured by starting the voltage clamp at a lower level than in the prior art.
[0083]
As described above, according to the present invention, various other effects can be expected and an excellent MOV surge arrester can be provided.
[Brief description of the drawings]
FIG. 1 is a partially broken perspective view from above of a preferred embodiment of a surge arrester including a single MOV.
FIG. 2 is a front view of the surge arrester of FIG.
3 is a side view of the surge arrester shown in FIG. 1. FIG.
4 is an exploded view of the surge arrester shown in FIG. 1. FIG.
FIG. 5 is a side view of a surge arrester connected to a 120/240 V single phase circuit.
FIG. 6 is a plan view of a three-phase surge arrester circuit.
FIG. 7 is a plan view of another embodiment of a three-phase surge arrester using four MOV surge arrester modules.
8 is a plan view of another embodiment of the three-phase surge arrester shown in FIG. 6. FIG.
FIG. 9 is a partially cutaway side view of a preferred embodiment of a single MOV case.
10 is a cross-sectional view taken along line 10-10 of FIG.
11 is a perspective view of the embodiment shown in FIG. 9 as viewed from above.
12 is a top perspective view of a preferred embodiment of a three-phase MOV case. FIG.
13 is a cross-sectional view taken along line 13-13 of FIG.
FIG. 14 is a side view of another embodiment of a three-phase module.
15 is a perspective view of the embodiment shown in FIG. 14 as viewed from below. FIG.
FIG. 16 is a plan view of a coated MOV.

Claims (6)

A surge arrester used at low voltage,
A pair of conductive plates having a parallel spatial relationship with a space in between;
A single large and thin MOV that is supported in the space between the conductive plates to make conductive contact with each of the plates;
A non-conductive epoxy resin filling the space;
The plate and a dielectric coating enclosing the epoxy resin,
Thereby, by power connection to the pair of conductive plates, surge protection against current is achieved without self-destructing by surge current across the MOV,
A surge arrester further comprising a soft conductive disk provided on both sides of the MOV to correct surface defects.   The surge arrester according to claim 1, wherein the soft conductive disk is further made of aluminum.   2. A surge arrester according to claim 1, wherein a thin conductive vapor deposition film is formed on both sides of the MOV instead of the soft conductive disk.   4. A surge arrester according to claim 3, wherein said thin conductive vapor deposited film comprises a low temperature vapor deposited film of copper having a thickness of 10 microns. A surge arrester used at low voltage,
A pair of conductive plates having a parallel spatial relationship with a space in between;
A single large and thin MOV that is supported in the space between the conductive plates to make conductive contact with each of the plates, and a non-conductive epoxy resin that fills the space; A dielectric film covering the plate and the epoxy resin,
Thus, the power connection to the pair of conductive plates achieves surge protection against current without self-destructing with a surge current of 1,000,000 amperes or more across the MOV, and further to correct surface defects. A thin conductive vapor-deposited coating formed on both sides of the MOV, and non-conductive nuts and bolts provided at each corner of the conductive plate for joining and applying tension to the plate. Surge arrester. A three-phase surge arrester block for systems up to 660 volts,
A plurality of at least eight parallel spaced apart conductive plates, including at least two ground plates and a pair of plates for each phase, to connect the first, second, third phase and ground to them A surge plate of at least 1,000,000 amperes sandwiched between a conductive plate having at least one staggered plate and a continuous plate for phase-to-phase and phase-to-ground surge protection A MOV having a small thickness and a large diameter to withstand, a non-conductive epoxy resin that fills all gaps between the plates, a dielectric coating that encloses the plates, and applying tension to the plates Therefore, a three-phase surge arrester block comprising: a non-conductive nut and a bolt provided at each corner of the conductive plate.

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