JPH028437B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fault section locating circuit for insulated wires passed through series type skin current heating tubes.

The series type skin current heating tube essentially includes a ferromagnetic tube and an insulated wire passed through it, each one end of which is connected to two terminals of an alternating current power supply, and each other end of which is connected to two terminals of an alternating current power source. It is connected to.

The principle of this heating tube will be briefly explained with reference to FIG. In this figure, 1 is a heating tube made of a ferromagnetic tube, for example, a steel tube, and 2 is an insulated wire passed through the heating tube, which is connected in series with a connecting wire 3 to an AC power source 4. In such a case, there is a certain relationship (t ≧2s), then
Since the current i flowing through the heat generating tube does not flow out to the outer surface of the heat generating tube, for example, even if the pipeline and this heat generating tube come into metallic contact, there will be no electrical leakage, and the pipeline can be heated and kept warm as a safe heating element.

Recently, this skin current heating tube is several kilometers long,
Furthermore, it has come to be used for heating and insulating pipelines that are several tens of kilometers long, but so far, even if an abnormality5 occurs due to dielectric breakdown of the insulated wires passed through the heating tube, It is almost impossible to determine the location of the abnormality at the power supply location using known detection methods or devices. Therefore, the insulated wire is divided into several sections at the joint box position of the wire, and the sections are divided by a megger test or the like. I had no choice but to discover.

In such cases, it is possible to use a known device to find the insulation position of a normal power cable, etc.
In a skin current heating tube, unlike a power cable or the like, as is clear from FIG. 1, dielectric breakdown of the insulated wire 2 occurs between the wire and the heating tube, which is a ferromagnetic tube, through which the wire 2 is passed.

Then, for example, from the known power source 4 side to the heating tube 1
In a method in which a voltage pulse is sent to the power source 4 and the dielectric breakdown position 5 is determined by the reflected wave, the pulse attenuation is large because the heating tube 1 is a ferromagnetic material.
It is difficult to know the location of breakdown beyond several kilometers. Therefore, as in the case of the megger test, although not shown in the figure, the interval between the joint boxes (the boxes to which the insulated wires in the tube are connected when constructing the skin current heating tube) is made small so that it is within the effective range of the pulse. There is no other way to know the location of insulation breakdown.

Other known methods, such as the Murray loop method, are practical if the pipeline is located on land, although they are troublesome, but are almost impractical if the pipeline is located underwater, such as on the ocean floor.

This is because, in the case of pipeline heating, the outer surface of the heating tube 1 shown in FIG. 1 is considered to be grounded at all positions, so a bridge structure cannot be constructed.

An object of the present invention is to eliminate such difficulties and provide a means for knowing the location of a failure in the insulated wire in the series type skin current heating tube at a predetermined location, such as the location of the power source.

That is, the present invention provides a series of series type skin current heating tubes, which is divided into two or more sections in the length direction, but electrically connected, and (a) the skin current at both ends of each section. (b) A means for measuring the difference between the two currents flowing through the insulated wire passed through the ferromagnetic tube of the heating tube, and an alarm wire for notifying a predetermined position when this difference exceeds a certain value; means for measuring the difference in voltage between the insulated wire passed through the skin current heating tube and the ferromagnetic tube at both ends of each section, and when this difference rises above a certain value, The series type skin current heating tube is provided with at least one of the notification lines for notification at the position of.

The above series of series type skin current heating tubes refers to series type skin current heating tubes consisting of a set of ferromagnetic tubes fed from two terminals of one power source and an insulated wire passed through the tubes. .

The series type skin current heating tube in the present invention refers to one having the principle explained above with reference to FIG. 1, but includes those having various modifications as long as it has this principle. For example, the cross section of the ferromagnetic tube is circular or triangular, the material of the ferromagnetic tube is different in a certain section from the other parts, the ferromagnetic tube has a slit in the length direction in a certain section, These include those in which an impedance (especially a capacitor) is inserted near one end of an insulated wire that is passed through the tube far from the power source, and those in which a short-circuiting conductor is placed in a ferromagnetic tube in a certain section.

To explain the requirement (a) in a little more detail, when focusing on one section of the skin current heating tube, there are respective values of the current flowing through the insulated wire within the tube at both ends of this section. The difference between these two current values is constant when there is no failure in the insulated wire within the pipe, but increases when a failure occurs. This is intended to be notified to a predetermined location such as a power supply location via the notification line.

The requirement (b) is that when focusing on one section of the skin current heating tube, a voltage exists between the ferromagnetic tube and the insulated wire passed therein at both ends of this section. The difference between these two voltages is constant when there is no failure in the insulated wire within the tube, but increases when a partial or total disconnection occurs. This is intended to be notified to a predetermined location such as a power supply location via the notification line.

Next, the present invention will be explained with reference to FIG. Second
In the figure, 1, 1', and 1'' are ferromagnetic heat-generating steel tubes in which the ferromagnetic tube 1 in Figure 1 is divided into three sections, and are electrically connected by connections 27 and 27'. , 27', in the case of heating a pipeline made of conductive material, the pipeline plays the same role as the ground 31. This division is an example, and the length and other physical characteristics of each division are not necessarily equal. Although it is not necessary, here we assume that they are almost equal.

Reference numeral 2 denotes insulated wires or cables passed through these heating tubes, which are connected to a power source 4 together with connecting wires 3 and 3' to form a series circuit. 5 illustrates the dielectric breakdown position of the electric wire 2, and 6 illustrates the disconnection position of the electric wire 2. Of course, this dielectric breakdown and disconnection do not occur at the same time, but for convenience of explanation, both of them 5 and 6 are shown in FIG.

23, 24, 25, and 26 are current transformers for measuring the current flowing through the wire 2 at the end of each section or at section positions A, BC, and D. When the current value is small, the circuit voltage is low. can be omitted.

Reference numerals 7, 8, 9, 10, 11, and 12 are current value measurement/comparison devices connected to the current transformer, and comparisons are made between adjacent 7, 8; 9, 10; In the state, the circuit current is i (in the normal state, it can be considered to be substantially constant in the length direction of the tube).
If so, since i is flowing through all the current transformers, for example, any of the current transformers 8, 10, and 12 will send a notification to the fault section detector 32 through the connecting wires 20, 20', 20'' and the notification line 2. It is configured so that nothing is done.

However, if dielectric breakdown occurs at position 5 in FIG. 2, the current values of current transformers 24 and 25 will be different, so comparison device 9
The difference is between 10 and 20',
21 to reach the discoverer 32. At this time, the fault current is varies depending on the degree of dielectric breakdown and the distance from the power source, but it is a circuit that returns from the connection 27' to the inner skin of the heating tube 1'', through the ground 31, and the connecting wire 3' to the power source 4. Therefore, since the current values of current transformers 25 and 26 are the same value as Is, comparators 11 and 12 do not operate, and the current values of current transformers 23 and 24 are both zero, although their values are not is. Since they are equal even if they are not zero, comparison devices 7 and 8 do not operate either.

Therefore, in this case, if the notification wire 21 is made up of two wires, and the comparison device 10 is configured to create a closed circuit between the two wires, the resistance of these two wires can be determined by the detector 32. Measuring device 10
Knowing the distance between the detector 32 and the dielectric breakdown 5,
It can be confirmed that this occurs in the heat generating tube 1'.

Normally, the distance between the ends of the section or the section positions A, B, C, and D is determined by the connection interval of the insulated wires 2, and its value is usually about 300 to 2000 m. Assuming that the total length is 30 km and cables are connected every 1 km, the location of dielectric breakdown 5 can be determined if the resistance value of the notification wire 21 can be measured with an accuracy of about 1/30, that is, about 3% or more. This is fully possible using known methods.

Also, the segment position value of the compartment, e.g. current transformer 2 in B
4. Comparing devices 8, 9, voltage measuring/comparing devices 13, 14 (to be described later), connections 20, 22, connecting wires 28, etc. are put together and placed in a watertight box if necessary.

The above has been about the case of dielectric breakdown of the insulated wire 2, but in the case of a break in the insulated wire 2 as shown in 6, the currents flowing through the current transformers 24, 25, and 26 are equally zero, making it impossible to discover the faulty section. It's impossible.

However, in this case, the faulty section can be discovered using the method described below. That is, in FIG. 2, the voltage measurement and comparison devices 13 and 14 are
15 and 16 are connection wires 29, and 17 is a connection wire 30 which is connected to the insulated wire 2 and measures the voltage between it and the ground 31. In this case, since the ferromagnetic tubes 1, 1', 1'' are also grounded, the measurement will be made between the insulated wire and the ferromagnetic tube.

For example, if the length of the heating tube 1 (the length between A and B) is 1000 m, the voltage applied to both ends of the heating tube 1 is usually 300 to 700V, so the voltage measurement and comparison device 13 The value is shown here, but let's assume it is 500V.

However, if a break 6 occurs, the current flowing through the wire 2 will be zero, so the wire 2 will be able to maintain the voltage of the power source 4, for example, over the entire length between the power source and the disconnection point 6.
It becomes 1500V. Therefore, voltage measuring and comparing devices 13, 14, 15, connected by wires 19, 19',
For example, 13 out of 16 and 17 is the normal voltage.
When the voltage becomes higher than 500V, the abnormality reaches the detector 32 through the connecting wire 22 and the notification wire 21. If disconnection 6
If this occurs at position 5, the voltage of the comparator 14 is zero and the voltage of the comparator 15 is 1500V, which also reaches the detector 32 through the connecting wire 22' and the notification wire 21, but the comparator Since the voltages of voltages 16 and 17 are equal to 1500V, comparator 17 does not operate. Therefore, it becomes possible to discover the location of the disconnected section, but
An example of the method may be the same as the method for dielectric breakdown described above.

Therefore, one common line can be used for both methods without providing separate notification lines.

In Figure 2, 18, 18', 18'' and 1
The former is an electric wire connecting adjacent current measuring and comparing devices, and the latter is an electric wire connecting adjacent voltage measuring and comparing devices, and the required number is represented by one wire.

As described above, according to the device of the present invention, by comparing the current values of adjacent skin heating tube sections, it is possible to detect insulation defects in the insulated wires passed through the heating tubes, as well as areas where dielectric breakdown has occurred. This discovery makes it easier to find disconnected sections by comparing voltage values, and is currently being implemented to improve the safety of long-distance pipelines that require heating and insulation, especially submarine lines. This increases reliability, and in the event that an abnormality occurs, it is easier to find the abnormality, which is useful for early repair.

The above is a single-phase skin current heating tube with a power supply of 4 and 3
Although the case of series connection has been described above, in the case of three phases, the single-phase method described above is simply applied to three sets for each phase. In this case discovery device 3
2 may be shared.

The device of the present invention can only detect the location of the faulty section, but if the insulated wire of the present invention is housed in a metal tube (heat-generating tube), the device of the present invention can detect only the location of the faulty section, but if the insulated wire of the present invention is housed in a metal tube (heating tube), Since the connection is only authorized within the junction box, it is not necessary to know the exact location of the fault; it is only necessary to find the faulty section, and the entire length of the wire in that section, including the healthy section, is replaced. Ru.

An impedance (preferably a capacitor) 3 is provided near the connection point between the ferromagnetic tube 1 and the insulated wire 2 in the tube.
3 may be inserted. This creates a large difference between the two currents flowing through the insulated wires in each section, especially in the section farthest from the power source or the section closest to it, making it possible to more sensitively detect insulation defects (this is not possible with general series type (The skin current heating tube was already proposed in Japanese Patent Application No. 170286/1986.) Furthermore, when the impedance 33 is a capacitor, the power factor of the series skin current heating tube circuit is improved,
Furthermore, it can be expected that the voltage of the power source 4 can be lowered, the capacity of the power transformer can be reduced, and the rating of the insulated wire can be lowered.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a skin current heating tube to which the device of the present invention is applied, and Fig. 2 shows the case of a skin current heating tube that is divided into three parts although they are electrically connected to each other. FIG. 2 is a principle circuit diagram for explaining. In these figures, 1, 1', 1'' are ferromagnetic (steel) tubes that serve as heating tubes, 2 is an insulated wire or cable that is passed through these, and 3, 3' is the load that the heating tube has on the electric wire 4. Connecting wires to form a circuit, 5 is an exemplary location of poor insulation or breakdown, 6 is an exemplary location of disconnection, 7, 8; 9, 10; 11, 12 are current transformers 2
A device capable of measuring and comparing the currents flowing in 3, 24, 25, and 26 between adjacent current transformers, 13; 1
4; 15; 16 and 17 are devices that can measure and compare the voltages with the heating tube (or ground) at each position of the insulated wire 2; 18 and 18' are devices that measure and compare adjacent currents; the wire 19 is This is also an electric wire for a voltage measurement and comparison device. 20; 20', 2
0'' is an electric wire that connects the failure section notification line 21 and the current measurement and comparison device, and 22, 22', and 22'' are electric wires that connect the notification line 21 and the voltage measurement and comparison device. Reference numerals 27 and 27' indicate electrical connections of the skin current heating tube divided into three sections. 28, 29, and 30 are connections for voltage measurement comparison between the insulated wire 2 and the heating tubes 1, 1', and 1'' (or the ground) at the division positions B, C, and D. 32 is the fault section It is a discovery device.

Claims (1)

[Scope of Claims] 1. A series of series type skin current heating tubes, which is divided into two or more sections in the length direction but electrically connected, and (a) at both ends of each section, means for measuring the difference between the two currents flowing through the insulated wire passed through the skin current heating tube; and a notification wire for notifying a predetermined position when this difference exceeds a certain value; and (b) each means for measuring the difference in voltage between the insulated wire passed through the ferromagnetic tube of the skin current heating tube and the ferromagnetic tube at both ends of the section, and when this difference rises above a certain value, A skin current heating tube having a fault section detection circuit, characterized in that at least one of the notification lines for reporting this to a predetermined position is provided. 2. The skin current heating tube according to item 1, characterized in that only (a) is provided. 3. The skin current heating tube according to item 1, characterized in that only (b) is provided. 4. The skin current heating tube according to item 1, characterized in that it is provided with both (a) and (b). 5. The skin current heating tube according to item 4, wherein the notification wires in (a) and (b) are common. 6. The notification line consists of two electric wires, and the distance between the power source and the faulty section can be estimated by means of measuring the electrical resistance between the predetermined position of these wires and the faulty section. Features 1~
The skin current heating tube according to any one of Item 5.