JPH0614096B2 - Divider for measuring dielectric loss of cable - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a voltage dividing rod used in measuring dielectric loss of a cable in a live state.

(Prior Art) The dielectric loss of the insulator of a power cable is one of the important factors that determine the performance of the cable. Generally, the dielectric loss of a cable is evaluated using tanδ. The tan δ of a cable that has not been laid yet before shipment is measured using a Schering bridge or the like. On the other hand, the measurement of tan δ for a cable in a live state is performed as follows.

FIG. 5 shows an explanatory diagram of the measuring method.

In the cable 1 shown in the figure, one end 2a of the conductor 2 is connected to the AC power supply 3, and the other end 2b is connected to the load 4. The one end 2a is connected to the measuring section via the voltage dividing resistor 5. On the other hand, the sheath 7 of this cable 1
Has one end directly grounded via a ground wire 8. Usually, if both ends of the cable sheath 7 are directly grounded, a large induced current circulates in the cable sheath 7, and thus such a single-end grounding method is often adopted in an actual line. A current transformer 9 for measuring current is attached to the ground wire 8.

The resistor 5 is provided with a voltage phase measuring terminal 10, one end 9a of the output of the current transformer 9 is grounded, and the other end 9b is provided with a charging current measuring terminal 12.

When connected in this way, the cable sheath 7 is grounded at one end, so that only the charging current based on the capacitance of the cable 1 flows through the ground wire 8. Therefore, the voltage phase measurement terminal 10
The output of the charging current measuring terminal 1 is proportional to the alternating voltage E applied to the conductor 2 of the cable 1 as shown in FIG.
The output of 2 is proportional to the charging current I of the cable 1. tan
δ can be obtained from the phase angle between the alternating voltage E and the charging current I.

It should be noted that, in practice, a live line in which a detection unit 13 surrounded by a dashed line in the figure and a measurement unit 14 that performs data processing such as calculation are integrated.
The tan δ measuring device is already on the market (Show Checker T
D: Trademark of Showa Electric Wire & Cable Co., Ltd.).

By the way, in the above measuring method, the resistor 5 constituting the detecting portion 13 shown in FIG. 5 is incorporated in the voltage dividing rod, and the voltage dividing rod is electrically contacted with the one end 2a of the cable conductor 2. Taking out the voltage phase.

FIG. 7 is an explanatory diagram in the case of extracting the voltage phase using the voltage dividing rod.

In the figure, the resistor 5 is arranged inside the voltage dividing rod 15, and a hook 16 electrically connected to the resistor 5 is attached to the tip of the voltage dividing rod 15. This hook 1
Reference numeral 6 is made of a conductive metal, and is hooked on one end 2a of a cable conductor extending from the cable head 17 to make electrical contact. The other end of the resistor 5 is connected to the detector 1 shown in FIG.
3 is connected to the voltage phase measurement terminal 10.

3 (A) and 3 (B) are a front view and a circuit configuration diagram of a conventional dielectric loss measuring voltage dividing rod 15. The voltage dividing rod 15 includes a rod body 18 made of an insulating material, and a rod body 18
Support 1 made of conductive metal attached to the tip of
9 and a hook 16 made of a conductive metal, which is integrally attached to the support base 19. Stick body 18
The resistor 5 described above is disposed at the tip of the resistor 5, and one end of the resistor 5 is electrically connected to the support base 19. The other end of the resistor 5 has an arrester 20 arranged substantially in the center of the rod body 18.
The arrester 20 is connected to a ground electrode 21 provided on the rod body 18. The ground electrode 21 is grounded via a ground wire 22. Further, one end of the output lead wire 23 is connected to the other end of the resistor 5, and the other end of the output lead wire 23 is connected to the voltage phase measuring terminal 10 as described above.
(Measurement section).

As described above, in the voltage dividing rod 15 having the above structure, the hook 16 is hooked on the one end 2a of the cable conductor 2 to be electrically contacted. Therefore, it is possible to take out the voltage phase from the cable 1 in the live line state by the voltage dividing rod 15 and supply this signal to the measuring section side.

(Problems to be Solved by the Invention) By the way, a power cable is usually used in three-phase alternating current. Therefore, as shown in FIG. 4, at the end of the cable 1, the three cable heads 17 are positioned adjacent to each other with a small space of, for example, 20 cm. On the other hand, the conventional voltage dividing rod 15 has a structure in which the exposed hook 16 formed of a conductive metal is directly hooked on the cable conductor 2 as described above. Therefore, when the hook 16 is brought close to one cable head 17 so as to be hooked on the cable conductor, the hook 16 may come into contact with a cable conductor extending from another adjacent cable head 17, and a flashover may occur between the phases. It was Therefore, in the conventional voltage dividing rod 15, it is necessary to be careful enough to approach the cable conductor of the cable head 17 when hooking the hook 16.

The present invention has been made in view of the above points, and an object of the present invention is to provide a voltage dividing rod capable of safely measuring the dielectric loss of a cable with good workability.

(Means for Solving the Problems) A voltage-dividing rod for measuring dielectric loss of a cable of the present invention is for detecting a voltage applied to a cable conductor, and a rod main body formed of an insulating material, and A contact electrode projectingly attached to the tip end surface of the rod body and contacting the cable conductor for detecting the voltage, and a tip end of the rod body movably attached in the axial direction to cover the contact electrode. An insulating cylinder having an opening for projecting the contact electrode; an elastic member for applying an elastic force to the insulating cylinder in a direction away from the tip surface of the rod body; and an insulating member attached to the tip of the rod body. , And an insulating hook member formed in a key shape so as to surround the cable conductor.

(Operation) With the insulating hook member hooked on the cable conductor, the contact electrode is positioned in the insulating cylinder and the tip of the insulating cylinder is brought into contact with the cable conductor.

After that, the rod main body is pressed against the elastic force of the elastic member, the contact electrode is projected from the opening of the insulating cylinder, and pressed against the cable conductor to bring them into contact with each other.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 (A) and 1 (B) are a front view of a voltage dividing rod for measuring dielectric loss (hereinafter referred to as a voltage dividing rod) of a cable according to the present invention and a sectional view showing a lock mechanism thereof.

In FIG. 1, reference numeral 30 indicates a rod body. The rod body 30 is made of glass fiber reinforced plastic (FRP), and a voltage dividing resistor 31 is arranged on the tip side. A support base 32 is attached to the tip surface of the rod body 30. The support 32 is made of a conductive metal such as brass plated with chrome and has a disk shape, and a contact electrode 33 is attached to the center thereof. The contact electrode 33 is similarly formed of a conductive metal into a cylindrical shape, and projects from the tip end surface of the rod body 30 along the central axis thereof. One end of a resistor 31 is electrically connected to the support 32, and one end of an output lead wire 34 is connected to the other end of the resistor 31.
The other end of the output lead wire 34 is led out to the outside from the lower end of the rod main body 30 and connected to the measuring unit side (not shown). Further, an arrester 35 arranged substantially in the center of the rod body 30 is connected to the other end of the resistor 31, and the arrester 35 is connected to a ground electrode 36 provided on the outer peripheral surface of the rod body 30. The ground electrode 36 is grounded via a ground wire 37.

An insulating cylinder 38 is fitted to the tip of the rod body 30 so as to be movable in the axial direction. The insulating cylinder 38 is made of an insulating material such as polyacetal resin, and has a spring receiving portion 38a inside the upper end side. An opening 39 for projecting the contact electrode 33 is formed at the center of the spring receiving portion 38a. One end of the coil spring 40 is in contact with the spring receiving portion 38a, and the other end of the coil spring 40 is in contact with the support 32. The coil spring 40 imparts an elastic force to the insulating cylinder 38 in a direction in which the insulating cylinder 38 is separated from the support base 32, that is, in a direction in which the insulating cylinder 38 projects from the tip of the rod body 30. Normally, the contact electrode 33 is covered with the insulating cylinder 38 and is positioned inside thereof.

As shown in FIG. 1 (B), an engaging protrusion 38b protruding inward is integrally formed at the lower end of the insulating cylinder 38. On the other hand, an opening 30a is formed at a predetermined position of the rod body 30, and a lock mechanism is provided in this opening 30a. This locking mechanism includes a casing 41 that closes the opening 30a, a locking piece 42 that is rotatably supported by the casing 41, a release protrusion 43 that is integrally formed with the locking piece 42, and a locking piece. A coil spring 44 that applies a pressing force to the piece 42 in a direction projecting outward from the rod body 30. The locking piece 42 has a protruding portion 42a that protrudes in a substantially triangular shape.
have. Therefore, the insulating cylinder 38 is
Is moved downward in the figure against the elastic force of the coil spring 40, the engaging protrusion 38b is released.
The locking piece 42 is pushed inward of the rod body 30 against the elastic force of 4. When the insulating cylinder 38 is further moved, the engaging protrusion 38
Since b is disengaged from the locking piece 42, the locking piece 42 again projects from the rod body 30 by the elastic force of the coil spring 44. Therefore, the engaging protrusion 38 is attached to the protrusion 42 a of the locking piece 42.
Since b is locked, the insulating cylinder 38 is held in a moved state. On the other hand, when the release protrusion 43 is pushed inward of the rod body 30 against the elastic force of the coil spring 44,
The locking piece 42 rotates so that the protruding portion 42a is disengaged from the engaging protrusion 38b. Therefore, the insulating cylinder 38 is connected to the coil spring 40.
The elastic force moves to the original position shown in FIG. 1 (A) to cover the contact electrode 33.

A thread groove 38c is provided on the inner wall on the upper end side of the insulating cylinder 38, and a mounting member 45 having a thread groove on the outer peripheral surface is screwed into this thread groove. The attachment member 45 has a through hole formed in the center thereof so that the contact electrode 33 can be projected, and a hook 46 is attached thereto. The hook 46 and the mounting member 45 are made of an insulating material such as polyacetal resin.

Next, a usage mode of the voltage dividing rod of the present invention will be described.

First, the voltage dividing rod of the present invention is brought close to the cable conductor of a predetermined cable head, and the upper end surface of the insulating cylinder 38 is brought into contact with the cable conductor. In this case, since the contact electrode 33 is located inside the insulating tube 38, even if the insulating tube 38 contacts the cable conductor of the nearby cable head, flashover does not occur.

Next, the rod body 30 is pushed up against the elastic force of the coil spring 40, and the insulating cylinder 38 is relatively moved (downward) on the rod body 30. Therefore, the contact electrode 33 becomes
Since it projects further and contacts the cable conductor, the voltage phase applied to the cable in a live state can be taken out. In this case, since the insulating cylinder 38 is locked by the lock mechanism as described above, the contact electrode 33 is held in the protruding state. Therefore, after that, the contact electrode 3 of the voltage dividing rod of the present invention
3 may simply be brought into contact with the cable conductor.

When the work of extracting the voltage is completed, the release protrusion 43 is pushed in to move the insulating cylinder 38 to the original position, and the contact electrode 33 is positioned in the insulating cylinder 38. Then, the voltage dividing rod of the present invention is brought close to the cable conductor of another cable head, and the same work is repeated.

Since the voltage dividing rod is quite long and heavy when the voltage of the overhead power transmission line is taken out, the insulating hook 46
Is hooked on the cable conductor to hold the voltage divider rod, which reduces the labor of the operator.

FIG. 2 is a view showing a main part of a voltage dividing rod according to another embodiment of the present invention. In this embodiment, the insulating cylinder 38 is formed in a short length, and a small diameter cylindrical portion 38A is coaxially formed at the tip. An opening 39 is formed in the cylindrical portion 38A, and the contact electrode 33 is located inside. This contact electrode 33 is attached to a conductive compression spring 47,
Is fixed to a support 32 '. The support 32 'is formed to have a larger diameter than the rod body 30. A stopper member 48 made of an insulating material is screwed to the lower end of the insulating cylinder 38. This stopper member 48 is a hook 46.
When the rod main body 30 is pulled down while being hooked on the cable conductor, the lower surface of the support base 32 'is touched so that the insulating cylinder 38 does not come off from the rod main body 30 and the coil spring 40 is not permanently distorted. The rod main body 30 is prevented from moving downward.

In addition, the mounting member 45 for mounting the hook 46 is the cylindrical portion 3
It is screwed into a screw groove 38c provided on the outer peripheral surface of 8A.

In this embodiment, the rod body 30 is pushed up against the elastic force of the coil spring 40 to push the contact electrode 33 into the cylindrical portion 3.
After contacting the cable conductor with 8A, the rod body 3
0 is pushed up, and only the contact electrode 33 is pressed against the cable conductor by the large pressing force of the compression spring 47. Therefore, the contact electrode 33 can be more surely brought into contact with the cable conductor.

(Effects of the Invention) As described above, according to the present invention, in a state where the rod body is supported by the cable conductor by the insulative hook, the contact electrode protruding and attached to the tip end surface of the rod body is attached to the insulating cylinder. The contact electrode inside the insulating tube until it comes close to the cable conductor, and when the contact electrode contacts the cable conductor, the insulating tube resists the elastic force of the elastic member against the rod body. Since the contact electrode is made to project from the insulating tube by moving the contact electrode, it is possible to provide a voltage divider rod that can extract the voltage phase of the cable in a live state safely and with good workability.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 (A) and (B) are a front view of a voltage dividing rod according to the present invention and a sectional view showing a lock mechanism thereof, and FIG. 2 is a diagram showing another embodiment of the present invention. The figure which shows the principal part of a pressure rod, FIG. 3 (A), (B)
Is a front view and a circuit configuration diagram of a conventional voltage dividing rod, FIG. 4 is a diagram schematically showing a voltage extraction state by a conventional voltage dividing rod, FIG. 5 is an explanatory diagram of a dielectric loss measuring method of a cable, FIG. 6 is an explanatory diagram of the operation of the measuring section, and FIG. 7 is a general explanatory diagram of the voltage extraction method. 1 ... Cable, 2 ... Cable conductor, 30 ... Rod main body, 31 ... Resistor, 32, 32 '... Support stand, 33 ... Contact electrode, 38 ... Insulation tube, 39 ... Opening part, 40 ... Coil spring, 42 ... Locking piece, 43 ... Release protrusion, 47 ... Compression spring, 48 ... Stopper member.

Front page continuation (72) Inventor Yasutaka Fujiwara 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Showa Electric Wire & Cable Co., Ltd. (72) Inventor Kazuo Yamaguchi 2-chome Oda, Kawasaki-ku, Kanagawa Prefecture No. 1 Showa Densen Denki Co., Ltd. (72) Inventor Jiro Kawai 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Densen Denki Co., Ltd. (56) Reference JP 62-254078 (JP, A) ) Actually open 61-65362 (JP, U) Actually open 63-54069 (JP, U)

Claims (1)

[Claims] 1. A cable main body for detecting a voltage applied to a cable conductor, the rod main body being formed of an insulating material, and projectingly attached to a tip end surface of the rod main body. The cable for detecting the voltage. A contact electrode that contacts the conductor, an insulating cylinder that is movably attached in the axial direction at the tip of the rod body, covers the contact electrode, and has an opening for projecting the contact electrode; An elastic member that gives an elastic force to the cylinder in a direction away from the tip surface of the rod body, and an insulating hook member that is attached to the tip of the rod body and is formed in a key shape so as to surround the cable conductor. A voltage dividing rod for measuring dielectric loss, which is characterized by being provided.