Frequently Asked Questions from TANO CABLE

1. According to the conductor permissive current, When low voltage overhead cable conductor passes the maximum permissible continuous load current, conductor wire core heat does not exceed the allowable temperature. 2. According to the permissive voltage loss. voltage loss is generated by low voltage overhead cable conductor continuously pass the normal maximum load current not exceed the permitted range, to ensure the normal operation of electrical equipment. 3. According to the mechanical strength, low voltage cable conductors should be prevented from breakage during installation or operation. Low voltage overhead cable conductor cross-section, AAC and AAAC are required not less than 25mm2, ACSR is not less than 25mm2, copper bare conductor voltage overhead cable diameter is not less than 4mm. When you select a larger conductor cross-section should consider according to the economic current density to minimize power consumption and operating costs of the line.

1. High current power cables cause eddy current problems. Power cables in the construction some use steel bracket some use steel protection tube and some use strain relief clamp and overhead cable laying. all in the vicinity of power cables formed of steel (iron)of a closed loop. it is likely to form a vortex, especially in high current power cable system, the eddy current is greater. When the power cable laying construction, measures must be taken so that the cable can not be formed closed loop around the steel(iron), prevent power cable causing eddy current. 2. Mechanical damage problems caused by power cable bending Due to the large diameter of power cable, transportation and laying is more difficult, the power cable to bending radius requirements is more stringent. When power cables is in laying construction, if the bending angle is too large, it may make the internal conductor subjected to mechanical damage, and cause mechanical damage cable insulation strength decline, until break down. In power cable construction process, we should minimize the torque cable suffered, when cable turning and obligate power cable, we should let the cable in a natural bent, prevent the power cable internal mechanical damage. 3. Power cable moistureproof problem. Operating experience shows that most of medium voltage power cable and low voltage power cable faults are occurred at the middle connector or terminal head of the cable, and the middle joints, and terminations head failure is largely due to poor sealing moisture intrusion caused dielectric strength decreased, while the medium voltage power cable and low voltage power cable net are usually use dendritic power supply, a larger number of cable terminal head. So to ensure that the cable head end and middle joints plugging seal i to ensure safe and reliable operation of the cable one of the important measures. 4. Medium voltage power cable and low voltage power cable grounding problems. In public medium voltage power cables net, since the three-phase load are not equal, so if using a metal sheath of the cable, the metal sheath grounded problem must be considered, and to ensure that at any point of non-ground metal protective layer normal induction voltage shall not exceed 100V.

1. The conductor must be smooth and free of burrs, and the insulating material should not contain impurities. 2. The three-layer co-extrusion is strictly implemented in accordance with the production process to avoid scorching and aging. 3. Safe operation at the construction site to avoid damage to the cables 4. Safe use of electricity and avoid overload. 5. Regular maintenance Line to ensure safe electricity use.

The core of optical fiber cable is a communication line which is composited of a certain number of optical fibers in a certain way, with outer jacket and outer sheath, for effecting optical signal transmission. Optical fiber cable has a larger transmission capacity than copper cable, long-distance relay, small size, light weight, no elctromagnetic inteference. Since 1976, optical fiber cable has developed into the main wire transmission line for long haul line. the city relay, coastal and transoceanic submarine communications. LAN, as well as private network . And begin to spread to areas of city subscriber loop distribution network, provide a transmission line for FTTH and B-ISDN.
Communication cable is usually made of a few or several groups of wires [each at least two] twisted together like rope cable, insulated from each other between each group wire, and often twisted around a center, there is the whole package outside highly insulating cover layer, especially a submarine cable.
Firstly, different material. Communication cable uses metal(mostly copper or aluminum) as conductor, optical fiber cable uses glassy fiber as conductor.
Secondly, different transmission signals. Communication cable transmission is electrical signal. Optical fiber cable transmission is optical signal.
Thirdly, different applications. Communication cable is used for energy transmission and low-end data transmission (eg. telephone). Optical fiber cable is used for data transmission.

1. Bare Conductor Overhead Cable is outside: it will be affected by climate and environmental conditions. Lightning, fog, wind, rain, snow, heat cold food, smoke and dust, fibers, etc are from different aspects threaten to Bare Conductor overhead Cables.

2.For the Bare Conductor Overhead Cable line fault phenomenon, there are mainly following situations mechanical damage, lead sheath cracking and spalling, head terminal flashover, head terminal or intermediate joints explode, insulation breakdown, metal sheath corrosion perforation and so on. For line fault causes of Bare Conductor Overhead Cable, there are following situations external damage, chemical etching or electroytic corrosion, lightning, flooding, pests and other
natural disasters as well as the improper construction, improper maintenance etc. personnel negligence factors.

3. When lightning struck Bare Conductor Overhead Cable it has the potential to make insulator flashover or breakdown. In order to improve resistance capacity to lightning and prevent lightning accidents, we can install lightning wire or lightning rod to prevent the conductor directly struck by lightning. we can install tube arrester to prevent harm lightning invasion wave, we can configure automatic reclosing prevent lightning flashover or other discharge causing power outages; we also can install n the neutral point arc suppression coil, in order to reduce other risk of lightning or other causes or single-phase ground.

1. Cable insulation should be checked before laying cables, 6-10KV cable uses 2500V magneto-ohmmeter, telemetry insulation resistance 2100MΩ; 3KV and below cable uses 1000V magneto-ohmmeter, telemetry insulation resistance 250MΩ, the suspected cable insulation should be taken withstand voltage test before laying confirm eligibility.

2. We should pay attention to the winding direction of the cable when erecting cable tray, should pull the cable from the top of cable tray, to prevent loose cable when cable tray is rotated. Pulled cable should be hold on rolling shelves or hold by people, not rub on the ground or gallows.

3. When laying cable, its curvature shall not less than the minimum allowable bend radius. At the end. persons who pull the cable should stand in the opposite direction of cable.

4. High voltage cables, low voltage cables and control cables should be separated laying. they arranged sequentially from top to bottom is high voltage cables, low voltage cables and control cables. Cross intersection should be arranged at the bottom of the cable or the inside, so that the exposed parts in order.

5. When cable laying, cable end termination and connector can leave spare length, and cable should be left at a small margin of the entire length when laying underground cable, and for undulating (snake) shape laying.

6. After the cable laying we should hang signboard in time, at both ends of the cable intersection, the corner point, entrance and exits of buildings all should be hang signboard.

7.Cable hardens in winter so that insulation is vulnerable to damage when laying cable. Thus, if the cable is laid prior to placement at the temperature below 0~5℃, the cable should be preheated.
There are two methods of preheating:
1)Increase the ambient temperature around the cable It will take three days and nights when the room temperature is 5- 10℃, one day and night at 25℃. and 18 hours at 40℃. Preheated cable should be completed laying within 1 hour.
2)Energized cables make the cable itself fever. Heating time is short with this method, but we should pay attention the applied current should not exceed the allowable cable ampacity. Cable surface temperature should not be higher than 40℃, not less than 5℃.

8.When cutting the cable, it should be based on the location of device terminals, and to consider maintenance moisture and other needs, determine the location of the fracture cable. To prevent loosening both sides will be tied up before sawing with iron wire and after sawing cable should be sealed immediately.