JP2933170B2 - Current test method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an energization test method for energizing a power cable or the like and measuring a temperature characteristic thereof.

(Prior Art) To know the characteristics of a power cable, it is extremely important to clarify its temperature characteristics.

Conventionally, the temperature characteristics of a power cable have been measured by a method as shown in FIG.

That is, in the figure, a sample cable 1 has slip-on type terminations 2 formed at both ends thereof,
It is mounted on an epoxy sleeve and the like housed inside.
Thereby, both ends of the sample cable 1 are short-circuited in the metal case 3, and a loop is formed.

On the other hand, a current transformer 4 composed of a toroidal coil is mounted on the sample cable 1. This current transformer 4 is connected in parallel with the capacitor 5 and is connected to the secondary side of the slidac 6. Slidak 6
The voltage received from the current 7 is varied to supply a predetermined primary current to the current transformer 4. The capacitor 5 is connected in parallel to the primary coil of the current transformer 4 to cut off an external surge.

As described above, when the predetermined current on the primary side of the current transformer 4 is supplied, the sample cable 1 becomes a secondary coil of the current transformer 4 and a predetermined current is induced. The current is set to a predetermined value, and if necessary, the current is varied stepwise by using a sliderac 6 to measure the temperature characteristics of the sample cable 1.

Note that the sample cable 1 itself cannot directly measure the temperature by making a hole in the insulator or cutting out the sheet for the purpose of conducting subsequent tests of electrical characteristics and the like.

Therefore, in addition to the sample cable 1, a dummy cable 1 'having a separate and substantially equivalent configuration is prepared. Then, just like the sample cable 1, the slider cable 6 ′, the capacitor 5 ′, and the current transformer 4 ′ are connected in parallel and attached to the dummy cable 1 ′. Then, electricity is supplied to the Tammy cable 1 'under the same conditions as the sample cable 1, and its temperature characteristics are measured using a thermocouple or the like embedded in the conductor or insulator of the dummy cable 1'. According to the value thus obtained,
The temperature characteristics of the sample cable 1 are estimated.

(Problems to be Solved by the Invention) By the way, conventionally, when the connection as shown in FIG. 2 is performed and a predetermined value is applied to the sample cable 1 and the dummy cable 1 ′, respectively, The inductance of the dummy cable 1 'has been an important problem.

That is, the sample cable 1 connected in a loop has a predetermined inductance. Therefore, when conducting a large current through the sample, it is necessary to cancel the inductance. Otherwise, a large-capacity power supply is required to overcome the inductance. For this purpose, measures such as inserting a compensating capacitor in the sample cable 1 in series are taken.

However, the compensating capacitor requires a relatively large-capacity power capacitor, and the larger the loop of the sample cable 1, the greater the inductance, and the more space required for disposing the necessary capacitor. There was a point.

The same can be said for the dummy cable 1 '.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an energization test method that reduces the size of a test apparatus and simplifies connection.

(Means for Solving the Problems) The present invention relates to an energization test in which a sample cable is connected in a loop, and the sample cable is passed through a coil of a current transformer to induce an alternating current to estimate a temperature characteristic of the sample cable. A method comprising: arranging a dummy cable connected in a loop along the sample cable, and spotting the dummy cable on the coil to induce an alternating current in the dummy cable in a direction opposite to the direction of the sample cable. Let it through,
Measuring the temperature of the dummy cable to estimate the temperature characteristics of the sample cable, canceling the inductance caused by the application of the alternating current of the sample cable by the inductance generated by the application of the reverse current of the dummy cable. It is characterized by doing.

(Operation) In the above method, the sample cable and the dummy cable are connected in a loop, respectively, and are arranged so that their inductances cancel each other, and the current is supplied. As a result, the inductance of both the sample cable and the dummy cable is reduced, and a current test with a large current can be easily performed. In this case, installation of a capacitor or the like for canceling the inductance can be omitted.

(Examples) Hereinafter, the present invention will be described in detail with reference to the illustrated examples.

FIG. 1 shows a connection diagram when the energization test method of the present invention is performed.

In the figure, a sample cable 1 has a slip-on type terminal 2 formed at both ends as in the conventional case, and a metal case 3.
Are mounted on an epoxy sleeve or the like and electrically connected to each other. Inside the metal case 3 is insulated by a gas such as SF _6. A current transformer 4 is mounted on the sample cable 1 whose both ends are short-circuited inside the metal case 3. The primary coil of the current transformer 4 is connected in parallel with the output terminals of a capacitor 5 and a slider 6. As a result, a predetermined current is supplied from the power supply 7 to the primary side of the current transformer 4 via the SLISAC 6, and a predetermined conduction current is induced in the sample cable 1.

On the other hand, in the present invention, a dummy cable 10 that is connected in a loop using a conducting lead 13 is disposed inside the sample cable 1. In addition, a reversing portion 13a is formed in a part of the conducting lead 13, and the current transformer 4 is mounted here.

The dummy cable 10 is a cable equivalent to the sample cable 1, and the energizing lead wire 13 is composed of a group of twisted wires.

That is, as is clear from the figure, the sample cable 1 is mounted on the secondary side of the current transformer 4, and the polarity of the sample cable 1 is reversed, and the current-carrying lead 13 is mounted. As a result, at a certain moment, for example, if a current flows in the sample cable 1 in the direction of the arrow 11, a current flows in the dummy cable 10 in the direction of the arrow 12, that is, in the opposite direction to the sample cable 1. Therefore, if the current-carrying sides are equal, the magnetic fields formed by the currents cancel each other. Thus, both the loop of the sample cable 1 and the loop of the dummy cable 10 have apparently zero inductance.

Note that the current flowing through the dummy cable 10 was
In order to make it equal to the above, a current adjusting portion 13b is provided on a part of the conducting lead wire 13.

That is, in the current adjusting section 13b, the current lead 13 is used to wind it into a sufficiently small loop to form a predetermined inductance. By adjusting the size and the number of turns of the loop, the inductance of the loop of the dummy cable 10 can be adjusted so that the current flowing through the dummy cable 10 and the current flowing through the sample cable can be made equal.

In the case of the above configuration, the inductance of the sample cable 1 and the inductance of the dummy cable 10 have extremely low values, and a large current can be supplied. Needless to say, in this case, it is not necessary to install a capacitor for canceling the inductance as in the conventional case.

In addition, if the conducting lead 13 is used, a dummy cable can be used.
10 current adjustments are possible. As a result, compared with the conventional method shown in FIG. 2, a capacitor or a slider for supplying a predetermined current to the dummy cable is not required.
Further, since the inductance of the sample cable 1 and the dummy cable 10 is small, it is also possible to conduct an energization test using a relatively small current transformer 4 having a small capacity.

In the above embodiment, one current transformer was used in common for the sample cable 1 and the current-carrying cable 10. However, two or three current transformers were mounted at the same time to increase the current-carrying current. But it doesn't hurt.

Further, the current may be supplied to the sample cable 1 and the current supply lead 13 using separate current transformers. The means for adjusting the current flowing through the dummy cable 10 may be configured such that an appropriate resistor is inserted into the current-carrying lead wire 13 that connects the dummy cable 10 in a loop.

(Effects of the Invention) According to the energization test method of the present invention described above, the sample cable and the dummy cable are arranged so that their inductances are canceled each other, and currents of substantially equal values in opposite directions are applied. As a result, the inductance of the sample cable and the dummy cable is reduced, and a large-current conduction test can be performed without installing a capacitor or the like. As a result, the test circuit is simplified, the installation space is easily secured, and the reliability of the test can be improved.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing an example of a conduction test method of the present invention, and FIG. 2 is a connection diagram showing an example of a conventional conduction test method. 1 ... Sample cable, 2 ... Terminal, 3 ... Metal case, 4 ... Current transformer, 5 ... Capacitor, 6 ... Slidac, 7 ... Power supply 10 ... Dummy cable, 13 ... Electrification lead wire .

Claims (1)

(57) [Claims] 1. An energization test method for connecting a sample cable in a loop, passing the sample cable through a coil of a current transformer, inducing an alternating current, and estimating a temperature characteristic of the sample cable. A dummy cable connected in a loop is arranged along with, and the dummy cable is inverted and passed through the coil to induce an alternating current in the dummy cable in a direction opposite to that of the sample cable. It is characterized in that the inductance caused by the passage of the alternating current is canceled by the inductance caused by the passage of the alternating current in the opposite direction of the dummy cable, and the temperature of the dummy cable is measured in order to estimate the temperature characteristics of the sample cable. Test method.