JPS60195461A - Method and device for measuring joint resistance of insulating joint - Google Patents

Abstract

PURPOSE:To measure a joint resistance of a pipe by means of non-cutting, by deriving the joint resistance from a current value flowing by applying an AC current to an exposed pipe and a buried pipe insulated by an insulating joint, and a voltage value applied between the upstream side and the downstream side of the insulating joint. CONSTITUTION:An AC signal is applied to a buried pipe 1 side and an exposed pipe 2 side into which an insulating joint 3 has been inserted, and only a current flowing through the joint 3 is measured by a clamp type current sensor 7 for converting an alternating field of the periphery of the joint 3 to an induced voltage, and an AC current measuring circuit 8. Also, at the same time, an AC voltage is applied to an exposed pipe side electric conductive terminal 4 and a buried pipe side electric conductive terminal 5 for holding an electric connection in the upstream side and the downstream side, respectively, of the joint 3 and measured by an AC voltmeter 10. Subsequently, a resistance value is measured by deriving the quotient obtained by dividing a joint up- and down-stream voltage value 14 by a joint passing current value 13, by an arithmetic circuit 11 and an indicator 12. In this way, a resistance of the joint installed in the pipe can be measured directly, easily and exactly in a state the pipe remains installed.

Description

[Detailed Description of the Invention] 1) Industrial Application Field The present invention aims to reduce the joint resistance of insulated joints installed in piping.
This article relates to a method and device for measuring without cutting pipes, and specifically relates to a terminal for energizing a 21-wire alternating current signal installed between the upstream and downstream sides of an insulated joint, that is, on the exposed piping side and the buried piping side. In order to measure only the current that flows through the insulated joint at 1° out of the AC current signal applied from the
The present invention relates to a method and an apparatus for precisely converting induced AC voltage signals to measurements by blocking internal magnetic noise and external electrical noise.

2) Problems with conventional technology In reinforced concrete buildings (1) Steel pipes for gas, water, etc. are buried in the ring as accompanying equipment, but 5. If these steel pipes become electrically connected to the reinforcing bars in the concrete. ,
A large battery is formed with 7 nodes of steel pipes buried in the soil and the cathode of the reinforcing steel, and the pipes buried in the soil become sites for the outflow of corrosion currents and sometimes suffer rapid corrosion of 1**/yr. Sometimes.

This form of corrosion is called macrocell corrosion, and this is to protect buried piping from this macrocell corrosion.

It is mandatory to insert insulating joints between exposed piping and buried piping installed in concrete buildings.

However, it is almost impossible to directly measure the joint resistance of an installed insulated joint;

Insulated joint-1 = If there is a defect in the pipe covering in the buried pipe on the downstream side, a metal/soil interface will be created, and if the exposed pipe downstream of the insulated joint is electrically connected to the reinforcing steel, This is because a metal (reinforcing bar)/soil (concrete) interface is created, and when an electrical signal is applied between the upstream and downstream of an insulated joint, a current will flow through the metal/soil (concrete)/metal (rebar). .

This phenomenon is caused by metal/soil (concrete)/metal (rebar)
This means that the thread acts as a resistance component that bypasses the insulated joint, and the resistance between the upstream and downstream sides of the insulated joint is measured as the parallel resistance of the joint resistance and the bypass resistance listed in -I-. Furthermore, the metal/soil interface has a characteristic that bipolarization occurs when a DC electric signal is applied, and the parallel resistance value itself changes.

Therefore, the resistance value of insulated joints installed in the piping system should not be measured without cutting using a megger or tester.It is only applicable when at least one of the pipes is electrically insulated from the ground. The range of application is extremely limited, and even if the measured value shows a low resistance, it is extremely difficult to determine whether it is due to deterioration of the joint resistance or the effect of the bypass mentioned above. It had the following drawback. Of the alternating current applied from the outside between 1st and downstream of the insulated joint, this is a device that detects the value of the current flowing through the joint without cutting the 3 piping.
It is possible to use a device commercially available as a clip-on ammeter, but this clip-on ammeter is a device whose main purpose is to distinguish whether a commercial power line is live or not. The signal order of the AC current flowing through an insulated joint and the AC 100V current flowing through a commercial power line may differ by 4 to 6 orders of magnitude, so it is not recommended to use a clip-on ammeter as part of this detection device. It's impossible. Therefore, when using these conventional devices, they are susceptible to external electrical noise and magnetic noise caused by signal current flowing into and out of the bypass resistance component, current flowing through commercial power lines, and other magnetic fields. In order to detect the weak signal current flowing through the insulating joint when an AC signal is applied, 5. Select the clamp installation position and maintain the equipment.

It requires careful attention to the selection of applied current, noise removal, etc., and requires a high degree of skill.

When the joint resistance is high or when the bypass resistance component is low, the value of the current flowing through the 811 hand becomes small and is mostly below the detection limit of commercially available devices. AC signal applied from outside.

Considering work safety, etc., there is a limit to the use of high voltage and large current signals.9For example, the standard value of joint resistance should be set to 100.
Even if a voltage of IOV is applied between the top and downstream of the joint, the maximum value of the current flowing through the joint is only 0.1-8, while the detection limit of commercially available equipment is 1 m.
There were drawbacks such as the fact that it remained at about A, making it impossible to measure the 111 hand resistance value.

3) Purpose of the present invention Based on the above, the purpose of the present invention is to provide a method and apparatus for measuring the joint resistance of an insulated joint installed in a pipe without cutting the pipe. .

4) Structure of the Invention In order to achieve the above object, the present invention employs a combination of measurements of each item described below.

Joint resistance measurement where an AC signal is applied to the buried piping side and the exposed piping side of the insulating joint inserted into the piping in order to electrically insulate the buried piping from the exposed piping, and at that time, only the current flowing via j111 is measured. Measuring the pipe at undesired IUi using a detection device, that is, III Manual passing current measurement 5 Simultaneously with the measurement of the joint passing current, ! 1! 5. Measuring the AC voltage applied between '-1 downstream with a high input impedance type AC voltmeter 5, that is, measuring the voltage applied to the joint.

Calculating the joint resistance from the quotient of the voltage applied to the joint divided by the current passing through the joint, that is, calculating the joint resistance using the measured values in item iii, item 2, followed by the detection device for joint resistance measurement. In order to achieve the objective 1-1 described in -1-, the silk-texturing table top of each component described in detail below was adopted.

9. Exposed pipe side of insulated joint and buried pipe to measure current value flowing through insulated joint without cutting? ! II+
A current-carrying terminal for applying an alternating current signal to the exposed piping side and the buried piping side of the two-piece silk, which is provided with a fixing band configured to maintain electrical connection with the exposed metal part of the metal part and a tension fitting support part.

An electromagnetic path iron core having a removable mouth shape on one side in order to detect with high sensitivity an alternating magnetic field generated by an applied alternating current to the jIN power line terminal and convert it into an alternating current voltage signal.

Noise is prevented by a copper plate on the electromagnetic path core 2
An alternating magnetic field induction coil in which a set of individual coils are arranged in parallel positions and in series with the winding direction of the coils.

External noise prevention 11-frame consisting of an external magnetic field blocking permalloy material and a Kube electrical noise prevention copper plate arranged with a certain space outside the alternating magnetic field induction coil.

It consists of an alternating current voltage measuring circuit for converting the induced voltage generated by the alternating magnetic field induction coil and the electromagnetic path iron core into a current value flowing through the insulating joint.

5) Example Fig. 1 shows an example of the joint resistance measuring method, and the reference numeral 4 indicates the exposed pipe side of the insulating joint 3 inserted into the pipe to electrically insulate the buried pipe l from the exposed pipe 2. This is an exposed-side current-carrying terminal that maintains an electrical connection with the terminal.

Reference numeral 5 denotes a terminal for energizing the buried piping side that is electrically connected to the buried piping side of the insulating joint.

Reference numeral 6 denotes a signal source that applies an alternating current signal between the buried piping-side energizing terminal and the exposed piping-side energizing terminal.

7 is a clamp type that is wrapped around an insulated joint and converts the alternating magnetic field around the insulated joint into an induced voltage using an electromagnetic induction core and an electromagnetic induction coil in order to measure the value of alternating current flowing through the insulated joint without cutting the pipe. 8 is a current sensor, and 8 is an AC current method measurement circuit that converts the induced voltage of the clamp-type current sensor into an AC current flowing through an insulated joint.

Reference numeral 9 denotes a reference resistor which is inserted into the output circuit of the buried piping-side energizing terminal side of the AC signal source and limits the upper limit of the energizing current.

Reference numeral 10 denotes a high input impedance type AC voltmeter for measuring an AC voltage value appearing between the upper and downstream sides of the insulated joint when an AC signal is applied.

Reference numeral 11 denotes an arithmetic circuit for calculating the insulation joint resistance from the current indication value of the clamp type current sensor and the alternating current measuring circuit and the voltage indication value of the high input impedance type alternating current voltmeter.

12 is a joint passing current (1) measured by the clamp-type current sensor and the alternating current measuring circuit out of the alternating currents 8 for displaying the calculation results based on the arithmetic circuit.

I4 is the joint up-and-down flow voltage (V)-1 (1-) measured by a high input impedance type AC voltmeter inserted in parallel with the joint between the upstream and downstream sides of the joint when measuring the 11-hand passing current.

Next, Figures 2 and 3 show the actual detection device for joint resistance measurement.
An example is shown in which the symbol 1' is used to measure the joint resistance of an insulated joint installed in a pipe without cutting it.

Two pieces 1 are provided with a Velcro (registered trademark)-like freely positionable fixing band 2' and a tension fitting support part 3' to maintain electrical connection with the exposed metal parts on the exposed piping side and the buried piping side of the insulated joint. This is a current-carrying terminal for applying an alternating current signal to the exposed pipe (III) and the buried pipe 1.

``4'' is a removable opening on one side and a joint for attachment/detachment in order to detect with high sensitivity the alternating magnetic field generated by the alternating current applied from the current-carrying terminal and convert it into an alternating voltage signal. These are knife-shaped and zigzag-shaped cores for electromagnetic paths.

6', two 1 ill coils are arranged parallel to each other and in series with respect to the winding direction of the coils. It is an alternating magnetic field induction coil. Reference numeral 7' denotes an external noise prevention frame consisting of an external magnetic field blocking permalloy plate 9' and an external electrical noise prevention copper plate 8', which are arranged with a certain space outside the alternating magnetic field induction coil.

Reference numeral 14' denotes an alternating current measuring circuit for converting the induced voltage generated by the alternating magnetic field induction coil and the electromagnetic path iron core into an alternating current flowing through the insulating joint.

The detection device for measuring joint resistance is as described above, and a fixed band 2 is attached to the exposed piping of the insulated joint and the metal protrusion of the buried piping.
' and a tension fitting support part 3' to add a current-carrying terminal 1', apply an AC signal to each piping side, detect the alternating magnetic field with the electromagnetic path iron core, and obtain an AC voltage signal 1. Next, the induced voltage generated by the alternating magnetic field induction coil 6' and the electromagnetic path iron core 4' is converted into an alternating current flowing through the insulated joint by the alternating current measuring circuit 14', and the joint resistance value of the insulated joint is determined. It is something.

6) Effects The effects obtained by the joint resistance measuring method, which is one of the aspects of the present invention, are as detailed below.

Since the joint resistance can be measured while installed in the piping, there is no need to cut the piping.

It is extremely easy to assemble a portable measuring device.

Next, the effects obtained by the detection device for joint resistance measurement will be described in detail below.

The second method of arranging the coils installed on the electromagnetic path core
By adopting a two-coil system as shown in Figures and Figures 3, it is possible to improve the S/N ratio and frequency selectivity compared to the one-coil and four-coil systems. This will improve the accuracy and precision of

A cylindrical copper plate is wound around the coil, and the copper plate and permalloy plate are placed with a certain space between them and the electromagnetic path iron core, which significantly reduces noise and improves the S/N ratio.

The lower detection limit can be set to O, OI+*A, making it possible to measure even high-resistance joints, expanding the range of measurement targets.

It is resistant to external noise, has improved operability, and can be easily handled by anyone.

[Brief explanation of the drawing]

11th! I is a circuit block diagram showing an example of the al1 hand resistance measuring method, Fig. 2 is a perspective view showing a detection device for joint resistance measurement and a terminal for energization, and Fig. 3 is a perspective view showing an iron core and a coil. . 1. Buried side piping 2, W outlet side piping 3, insulation joint 4, outlet side piping energization terminal 5, buried side piping energization terminal 6, AC signal source 7, clamp type current sensor 8, AC current measuring circuit 9 , reference resistance 10, high input impedance AC voltage needle 11, arithmetic circuit 12, display -14 = 13, joint passing current value +4. Joint applied voltage value 15, buried pipe covering 16, insulating joint 17, main branch pipe 1' energizing rod 2' magic tape 3' tensile fitting support section 4' iron core for electromagnetic path 5I, copper cylindrical plate for noise prevention 6' alternating magnetic field Induction coil 7' External noise prevention frame 8' External electrical noise prevention Ichikawa copper plate 9' Permalloy plate for external magnetic field interruption 10'' Cedar 1 fat for holding iron core for electromagnetic path 11' Lead wire for main body connection 12' Lead wire for signal source connection 13'Acicular current-carrying point 14'Alternating current measuring circuit 15- Procedural amendment (voluntary) June 1980 22F1 Kazuo Wakasugi, Commissioner of the Patent Office 2 Title of invention Method and device for measuring joint resistance of insulated joints 3, Amendment Applicant: Tokyo Chuo IK Yaesu 1-r 112-16V-3 Tokyo Gas Co., Ltd. Representative Hiroshi Watanabe and 1 other company 4, Agent 5T Honkomagome, Bunkyo-ku, Tokyo [+73-2-6 , Contents of the amendment (1) Add the words "patent application pursuant to the proviso to Article 38 of the Patent Act WIJ" next to the application for patent (2). (2) Correct the column for the number of inventions stated in the claims of the application to "2".

Claims (1)

[Claims] 1) When an alternating current is applied upstream and downstream of an insulated joint installed in a pipe, that is, to the exposed pipe side and the buried pipe side that are electrically insulated by the insulated joint. The value of the current flowing through the insulated joint and the value of the voltage applied between the upstream and downstream sides of the insulated joint at that time were measured simultaneously. A method for measuring joint resistance of an insulated joint, which calculates the joint resistance of an insulated joint installed in a pipe without cutting the pipe from calculation of the current value and voltage value. 2) In order to measure the current value flowing through the insulated joint without any delay, a fixing band and a tension fitting support are used to maintain electrical connection with the exposed metal parts on the exposed piping side and the buried piping side of the insulated joint. A current-carrying terminal for applying an alternating current signal to the exposed piping side and the buried piping side of the two silks. An electromagnetic path iron core having a removable opening on one side for detecting with high sensitivity an alternating magnetic field generated by an alternating current applied from the energizing terminal and converting it into an alternating voltage signal. Noise is prevented by a copper plate on the electromagnetic path core 2
11 & 11 sets of coils are placed parallel to each other. and an alternating magnetic field induction coil arranged in series with the winding direction of the coil. An external noise prevention frame comprising a permalloy plate for blocking external magnetic fields and a copper plate for preventing external electrical noise, which are arranged with a certain space outside the alternating magnetic field induction coil. An insulating joint installed in piping, comprising the alternating magnetic field induction coil and an alternating current measuring circuit for converting the induced voltage generated by the electromagnetic path iron core into an alternating current flowing through the insulating joint. Device for measuring joint resistance.