Causes of water-cooled cable breakage and repair methods

Technical

Equipment electrical maintenance knowledge

Causes of water-cooled cable breakage and repair methods

Time: 2019-09-07

The water-cooled cable consists of a central cooling water pipe, a wire around it, a rubber tube outside the wire, and a rubber tube. The inner and outer layers are integrally formed into a cylindrical shape, and the layers of the shielding layer, the heat insulating layer and the metal outer layer are respectively arranged. In addition to the many advantages of ordinary water-cooled cables, the utility model has changed the disadvantages of the prior art to expose the outer rubber tube. The metal bellows jacket is not afraid of spark splashing, will not age, does not charge when working, and has good heat insulation effect. It has a long service life and is a novel power supply cable used in electric furnaces and electric arc furnaces in the metallurgical industry. It is also an ideal water-cooled power supply cable for ferroalloy electric furnaces.

Due to the special structure of the water-cooled cable, it is different from the general cable fault judgment. An example is given below.

Phenomenon

The electric arc furnace enters the secondary material and is energized and smelted. The No. 2 electrode (V phase) has no arcing, and the No. 1 (W phase) and No. 3 (U phase) electrodes can arc, but the arc is weak. The cross-section of the V-phase water-cooled cable is 3,500 mm 2 and two are arranged in parallel. It is generally considered that the possibility of short-circuiting the two cables at the same time is small.

2. Judging

Adjust the secondary voltage of the electric arc furnace transformer to 360V gear, close the brake, first measure the secondary voltage of V phase with a multimeter, which is normal value; but this value is the measured value when there is no large current, and it does not indicate that the cable is intact (because After the large-section water-cooled cable is broken, the resistance value does not necessarily become infinite. For example, there is a resistance of several thousand ohms. For a meter with a high internal resistance such as a multimeter, the voltage drop is small, so the multimeter will display Basically normal voltage). For this reason, it is necessary to install the test load and test it (because a large power load is added to the disconnected water-cooled cable, the resistance of several thousand ohms on the line is almost reduced, and the multimeter can display Out of normal voltage). For example, a 500W bulb is connected in series to the conductive cross arm, and the gate is energized. If the bulb is not lit, the V phase voltage is measured at this time, and there is no reading, indicating that both cables have been disconnected.

3. Precautions

(1) The power of the test load should be large enough to allow a certain current to pass through the water-cooled cable for profit judgment;

(2) Before the load test, adjust the secondary voltage of the arc furnace transformer to 400V or less for safety.