JPH0690254B2 - Measuring method for abnormal parts of metal shielding layer - Google Patents
Measuring method for abnormal parts of metal shielding layerInfo
- Publication number
- JPH0690254B2 JPH0690254B2 JP17061887A JP17061887A JPH0690254B2 JP H0690254 B2 JPH0690254 B2 JP H0690254B2 JP 17061887 A JP17061887 A JP 17061887A JP 17061887 A JP17061887 A JP 17061887A JP H0690254 B2 JPH0690254 B2 JP H0690254B2
- Authority
- JP
- Japan
- Prior art keywords
- cable
- shielding layer
- metal shielding
- pulse
- layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Locating Faults (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、金属遮蔽層を有するケーブルの異常部位、例
えば銅テープ巻遮蔽層の吸水劣化の測定を行う金属遮蔽
層の異常部位測定法に関するものである。Description: TECHNICAL FIELD The present invention relates to a method for measuring an abnormal portion of a cable having a metal shielding layer, for example, an abnormal portion of a metal shielding layer for measuring water absorption deterioration of a copper tape winding shielding layer. It is a thing.
［従来の技術］ 従来から銅テープ巻等の金属遮蔽層を有するケーブルの
絶縁劣化の原因には、吸水、ボイド、傷などの諸種のも
のが知られているが、その中でも吸水劣化によるものが
最も多い。[Prior Art] Conventionally, various causes such as water absorption, voids, and scratches are known as causes of insulation deterioration of a cable having a metal shielding layer such as a copper tape winding. Among them, those caused by water absorption deterioration are known. Most.
絶縁劣化の測定法としては、直流法、tanδ法、部分放
電法等が知られているが、これらの方法を用いた場合
に、線路の長さ方向に次第に劣化してその境界が明らか
でないケーブルの絶縁劣化の測定では、次に述べるよう
な問題点がある。The DC method, tan δ method, partial discharge method, etc. are known as methods for measuring insulation deterioration, but when these methods are used, the cable is gradually deteriorated in the length direction of the line and its boundary is not clear. In the measurement of insulation deterioration, there are the following problems.
（１）直流法はCVケーブルの場合に、線路の長さ方向の
一部分の吸水劣化の有無は検知できるが、その位置を非
破壊的に知ることができない。(1) The DC method can detect the presence or absence of water absorption deterioration in a part of the length of the line in the case of a CV cable, but its position cannot be known nondestructively.
（２）tanδ法は吸水劣化などケーブル線路全体の劣化
の検知には優れているが、ケーブルの長さ方向の一部分
が劣化している場合には、絶縁の良い部分に隠されて劣
化を検知できない。(2) The tan δ method is excellent for detecting deterioration of the entire cable line, such as water absorption deterioration, but when part of the cable length direction is deteriorated, it is hidden by a well-insulated part to detect deterioration. Can not.
（３）部分放電法は外傷、ボイドなどの欠陥を検知で
き、その位置の測定も可能であるが、吸水劣化したケー
ブルは部分放電が起り難く適用することができない。(3) The partial discharge method can detect defects such as external damage and voids and can measure the position thereof, but a cable that has deteriorated due to water absorption is difficult to cause partial discharge and cannot be applied.
［発明の目的］ 本発明の目的は、上述した従来例の問題点を除去し、ケ
ーブル線路の吸水による金属遮蔽層の絶縁劣化の程度、
劣化区間の位置をパルスを用いて正確に測定することが
可能な金属遮蔽層の異常部位測定法を提供することにあ
る。[Object of the Invention] An object of the present invention is to eliminate the above-mentioned problems of the conventional example, and to determine the degree of insulation deterioration of the metal shielding layer due to water absorption of the cable line
An object of the present invention is to provide a method for measuring an abnormal portion of a metal shielding layer, which can accurately measure the position of a deteriorated section using a pulse.
［発明の概要］ 上述の目的を達成するための本発明の要旨は、金属遮蔽
層を有するケーブルの導体にパルス電圧を印加して、こ
のパルスが前記ケーブル線路中で最初に反射して戻って
くる伝送時間を測定し、前記金属遮蔽層に異常がないケ
ーブル線路における伝送時間と比較することにより、前
記金属遮蔽層の吸水劣化による複合インダクダンスの変
化を利用して前記金属遮蔽層の吸水劣化の程度及び位置
を検出することを特徴とする金属遮蔽層の異常部位測定
法である。[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to apply a pulse voltage to a conductor of a cable having a metal shielding layer, and the pulse is first reflected and returned in the cable line. The transmission time of the metal shielding layer is measured and compared with the transmission time in a cable line in which the metal shielding layer has no abnormality. It is a method for measuring an abnormal portion of a metal shielding layer, which is characterized by detecting the degree and position of.
［発明の実施例］ 本発明による測定法を図示の実施例に基づいて詳細に説
明する。[Examples of the Invention] The measuring method according to the present invention will be described in detail with reference to the illustrated examples.
第１図はこの測定法の説明図であり、導体１は絶縁層を
介在して金属遮蔽層２によって包囲されている。近端Ａ
における導体１にはパルス発生器３及び波形観測器４を
接続し、金属遮蔽層２にも同じパルス発生器３及び波形
観測器４を接続する。なお、金属遮蔽層２は絶縁層上に
例えば銅テープを重ねながら巻き付けて形成したもので
あり、導体１及び金属遮蔽層２及び絶縁層から成るケー
ブルは、ケーブルの長さ方向に例えば260pF/mの静電容
量Ｃと、0.37μH/mのインダクタンスＬを持つと共に、
ケーブルの長さ方向の導線抵抗及び漏洩コンダクタンス
は殆ど零に近い分布定数であるものとする。FIG. 1 is an explanatory view of this measuring method, in which a conductor 1 is surrounded by a metal shielding layer 2 with an insulating layer interposed. Near end A
The pulse generator 3 and the waveform observing device 4 are connected to the conductor 1 and the same pulse generator 3 and the waveform observing device 4 are also connected to the metal shield layer 2. The metal shielding layer 2 is formed by, for example, winding a copper tape on the insulating layer while wrapping it, and the cable including the conductor 1, the metal shielding layer 2 and the insulating layer is, for example, 260 pF / m in the length direction of the cable. With capacitance C and inductance L of 0.37 μH / m,
The conductor resistance and leakage conductance along the length of the cable are assumed to be distributed constants close to zero.
ケーブルの特性インピーダンスZ0は、 Z0＝（L/C）1/2 …（１） の式で表されるので、この場合の特性インピーダンスZ0
は、 Z0＝｛（0.37/260）・106｝1/2 ≒38［Ω］である。The characteristic impedance Z0 of the cable is expressed by the formula Z0 = (L / C) 1/2 (1), so the characteristic impedance Z0 in this case
Is Z0 = {(0.37 / 260) · 10 6 } 1/2 ≈38 [Ω].
ところで、ケーブルの金属遮蔽層２が浸水して錆びる
と、銅テープの重なった部分が絶縁され、コイルと同じ
状態になる。錆びた銅テープの１回転当りのインダクタ
ンスＬは例えば0.37μＨであり、ケーブル1mについて錆
びた銅テープが３回転分のコイルを形成したとすると、
このケーブルの浸水部分の特性インピーダンスZ1は、
（１）式より、 Z1＝｛３×0.37/260）・106｝1/2 ≒65［Ω］となる。By the way, when the metal shielding layer 2 of the cable is flooded and rusted, the overlapped portions of the copper tape are insulated and become in the same state as the coil. The inductance L of the rusted copper tape per revolution is, for example, 0.37 μH, and assuming that the rusted copper tape forms a coil for three revolutions per 1 m of cable,
The characteristic impedance Z1 of the flooded part of this cable is
From the equation (1), Z1 = {3 × 0.37 / 260) · 10 6 } 1/2 ≈65 [Ω].
ケーブルの浸水していない部分と、浸水した部分との境
界における電気パルスの反射係数ｍは、 ｍ＝（Z1−Z0）／（Z1＋Z0） …（２） の式で表されるので、 ｍ＝（65−38）／（65−38） ≒0.26 となり、電気パルスがケーブルの浸水していない部分か
ら浸水した部分に入射すると、入射した電気パルスの振
幅値の26％が反射されてしまう。これだけの振幅のパル
スが反射されると、波形観測器４で反射パルスを観察す
ることが可能になる。The reflection coefficient m of the electric pulse at the boundary between the unflooded portion of the cable and the flooded portion is expressed by the equation m = (Z1-Z0) / (Z1 + Z0) (2), so m = ( (65-38) / (65-38) ≈ 0.26, and when an electric pulse is incident on the flooded part from the unflooded part of the cable, 26% of the amplitude value of the incident electric pulse is reflected. When the pulse having such an amplitude is reflected, it becomes possible to observe the reflected pulse with the waveform observing device 4.
金属遮蔽層２が正常な場合には、パルス発生器３からケ
ーブルに近端Ａでパルスを注入し、伝送時間を横軸にと
ると、波形観測器４には第１図（ｂ）に示すような時間
軸に対する反射パルスが現れる。即ち、近端Ａにおい
て、数μＳの幅のパルスPaを加えると、遠端Ｂにおいて
パルスPbが反射して時間t1に戻ってくる。なお、特性イ
ンピーダンスZ0が一定であれば、パルスの伝播速度は一
定であるから、パルスの伝送時間ｔは近端Ａから反射点
までの距離に比例する。ここで、反射点までの距離をＬ
とし、比例定数をｋとすると、 Ｌ＝ｋ・ｔ …（３） という式が成り立つ。When the metal shield layer 2 is normal, a pulse is injected from the pulse generator 3 into the cable at the near end A, and the transmission time is plotted on the horizontal axis. The reflected pulse appears on the time axis. That is, when a pulse Pa having a width of several μS is applied at the near end A, the pulse Pb is reflected at the far end B and returns to time t1. If the characteristic impedance Z0 is constant, the pulse propagation speed is constant, so the pulse transmission time t is proportional to the distance from the near end A to the reflection point. Where the distance to the reflection point is L
And the proportional constant is k, the equation L = k · t (3) holds.
次に、金属遮蔽層２が点Ｃで浸水劣化し、上述したよう
にその部分の特性インピーダンスZ1が大きくなると、近
端Ａから注入したパルスPaは点Ｃで一部が反射され、第
１図（ｃ）に示すような時間軸に反射パルスが現れる。
即ち、点Ｃにおける反射パルスPcが時間t2に波形観測器
４で観察されることになる。点Ｃにおける反射パルスPc
は、金属遮蔽層２が正常な特性インピーダンスZ0の部分
しか伝送していないので、金属遮蔽層２が正常な時に測
定した時間t1と、この時間t2との比はケーブルの長さL1
と近端Ａから点Ｃまでの距離L2との比に等しく、 L2/L1＝t2/t1 …（４） という関係式が成り立つ。この（４）式を変形すると、 L2＝（L1/t1）・t2 …（５） なる式が導出される。即ち、予め正常なケーブルの長さ
L1及び遠端Ｂによる反射パルスPbの伝送時間t1を測定し
ておけば、ケーブルが浸水劣化した際に、反射パルスPc
の伝送時間t2を測定するだけで劣化した点Ｃの位置を知
ることができる。Next, when the metal shielding layer 2 is deteriorated by flooding at the point C and the characteristic impedance Z1 at that portion becomes large as described above, a part of the pulse Pa injected from the near end A is reflected at the point C, and FIG. A reflected pulse appears on the time axis as shown in (c).
That is, the reflected pulse Pc at the point C is observed by the waveform observer 4 at time t2. Reflection pulse Pc at point C
Since the metal shield layer 2 transmits only the portion of the normal characteristic impedance Z0, the ratio between the time t1 measured when the metal shield layer 2 is normal and this time t2 is the length L1 of the cable.
Is equal to the ratio of the distance L2 from the near end A to the point C, and the relational expression L2 / L1 = t2 / t1 (4) holds. When this equation (4) is modified, the equation L2 = (L1 / t1) · t2 (5) is derived. That is, the normal cable length
If the transmission time t1 of the reflected pulse Pb due to L1 and the far end B is measured, the reflected pulse Pc
The position of the deteriorated point C can be known only by measuring the transmission time t2 of.
また、ケーブルの浸水劣化が進行すると、特性インピー
ダンスZ1が増加し、（２）式から反射係数ｍも大きくな
るので、波形観測器４で観察される点Ｃによる反射パル
スPcの振幅が大きくなる。このことから、反射パルスPc
の振幅値からケーブルの浸水劣化の程度を知ることが可
能となる。Further, as the deterioration of the cable by flooding increases, the characteristic impedance Z1 increases and the reflection coefficient m also increases from the equation (2), so that the amplitude of the reflection pulse Pc at the point C observed by the waveform observing device 4 increases. From this, the reflected pulse Pc
It is possible to know the degree of water degradation of the cable from the amplitude value of.
また、予め正常なケーブルを用いて、（３）式の比例定
数ｋを求めておけば、ケーブルが浸水劣化した際に反射
パルスPcの伝送時間t2を測定するだけで、（３）式から
劣化した点Ｃの位置を検出することができる。Moreover, if the proportional constant k of the equation (3) is obtained in advance using a normal cable, it is possible to measure the transmission time t2 of the reflected pulse Pc when the cable is submerged and deteriorate by the equation (3). It is possible to detect the position of the point C.
［発明の効果］ 以上説明したように本発明に係る金属遮蔽層の異常部位
測定法によれば、金属遮蔽層を有するケーブルの異常部
位、特に吸水劣化した位置及びその程度を正確かつ簡便
に検出することが可能になる。[Effects of the Invention] As described above, according to the method for measuring an abnormal portion of a metal shielding layer according to the present invention, an abnormal portion of a cable having a metal shielding layer, in particular, a position where water absorption is deteriorated and its degree are accurately and easily detected. It becomes possible to do.
【図面の簡単な説明】 図面は本発明に係る金属遮蔽層の異常部位測定法を示
し、第１図（ａ）はその説明図、（ｂ）は正常なケーブ
ルの反射パルス波形図、（ｃ）は浸水劣化したケーブル
の反射パルス波形図である。 符号１は導体、２は金属遮蔽層、３はパルス発生器、４
は波形観測器である。BRIEF DESCRIPTION OF THE DRAWINGS The drawings show a method for measuring an abnormal portion of a metal shielding layer according to the present invention. FIG. 1 (a) is an explanatory view thereof, FIG. 1 (b) is a reflection pulse waveform diagram of a normal cable, and FIG. [Fig. 4] is a reflection pulse waveform diagram of a cable that is deteriorated by flooding. Reference numeral 1 is a conductor, 2 is a metal shielding layer, 3 is a pulse generator, 4
Is a waveform observer.
Claims (1)
ス電圧を印加して、このパルスが前記ケーブル線路中で
最初に反射して戻ってくる伝送時間を測定し、前記金属
遮蔽層に異常がないケーブル線路における伝送時間と比
較することにより、前記金属遮蔽層の吸水劣化による複
合インダクダンスの変化を利用して前記金属遮蔽層の吸
水劣化の程度及び位置を検出することを特徴とする金属
遮蔽層の異常部位測定法。1. A pulse voltage is applied to a conductor of a cable having a metal shielding layer, and a transmission time of the pulse which is first reflected and returned in the cable line is measured, and an abnormality is detected in the metal shielding layer. A metal shield characterized by detecting the degree and position of water absorption deterioration of the metal shield layer by utilizing the change of the composite inductance due to water absorption deterioration of the metal shield layer by comparing with the transmission time in a non-cable line. Method for measuring abnormal site of layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17061887A JPH0690254B2 (en) | 1987-07-08 | 1987-07-08 | Measuring method for abnormal parts of metal shielding layer |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17061887A JPH0690254B2 (en) | 1987-07-08 | 1987-07-08 | Measuring method for abnormal parts of metal shielding layer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6413471A JPS6413471A (en) | 1989-01-18 |
| JPH0690254B2 true JPH0690254B2 (en) | 1994-11-14 |
Family
ID=15908209
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17061887A Expired - Fee Related JPH0690254B2 (en) | 1987-07-08 | 1987-07-08 | Measuring method for abnormal parts of metal shielding layer |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0690254B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3247049B2 (en) * | 1996-08-08 | 2002-01-15 | 三菱電線工業株式会社 | Cable deterioration diagnosis method |
| JP2006023105A (en) * | 2004-07-06 | 2006-01-26 | Hitachi Cable Ltd | Method of detecting disconnection in electric wire |
-
1987
- 1987-07-08 JP JP17061887A patent/JPH0690254B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6413471A (en) | 1989-01-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |