Cable damage

With the exception of terminal compartments in e or d or within an enclosure in case of direct cable entries into d or p, such an IT system shows totally screened phase conductors which are not subject to an immediate short-circuit condition in case of cable damage or an internal insulation fault. Even in the earth fault condition the network may remain operational. And this is the great advantage of these systems compared with, e.g., a TN system... 

Moreover, the cable was cut at the vertex of a U-shaped loop to ensure gas entry to the point of cable damage as quick as possible. 

Case 8. On September 28, a 49-year-old man in San Juan was electrocuted while repairing a cable damaged by the storm. He was an employee of the electrical company. 

Application of a three-phase short circuit to the terminals of an unloaded induction motor is not a practical factory test, especially for a large high-voltage motor, because the motor can only be excited at its stator windings from the power supply. A three-phase short circuit at or near the stator terminals can occur in practice e.g. damaged supply cable, damage in the cable terminal box. The parameters of the stator and rotor windings can be obtained from other factory tests. However, the derived reactance can be defined in the same manner as those for the synchronous machine, but with... 

Break of the cable strain relief, causing cable damage IR travels at high speed against end stop Physical injury (arm)... 

The mean conditional probability that an I C cable in the fire compartment is damaged during the fire scenario was estimated to be 1.76 E-02 based on failure criterion 1 and 4.10 E-03 based on criterion 2. Figure 5 shows the epistemic uncertainty of the cable damage probability for each criterion. It can be seen that the epistemic probability distributions due to both criteria differ significantly. Since just a sample of 60 values is available from the simulations of MCDET and FDS, the one-sided upper (95%, 95%) tolerance limit was calculated to quantify the epistemic uncertainty of the cable damage probability (see section 3.2). With failure criterion 1, the (95%, 95%) tolerance limit is 0.5. The (95%, 95%) tolerance limit based on criterion 2 is 1.53 E-02. 

The results clearly show the effect of different failure criteria on the calculated cable damage probability. They underline what intuitively seems to be more realistic, namely to consider both... 

Bell s use of vacuum excavation to expose and document exact facility locations is credited with decreasing cable damages by 50 percent in Texas during 1996 [57], This method positively identifies both the horizontal and vertical location of the pipe at a specific site. Bnt certainty about the line s position is inversely related to its distance from the test hole. Depth depends on how the line was installed and on the changes in surface grade caused by erosion or constmction since installation. 

MI cables can maintain temperatures up to 1200°F and withstand exposure to up to 1500°F. The major disadvantage of Ml cable is that it must be factory-fabricated to length. It is very difficiilt to terminate or splice the heater in the field. This means pipe measurements are necessary before the heaters are ordered. Also, any damage to an MI cable generally requires a complete new heater. It s not as easy to splice in a good section as with self-regulating heaters. 

While connecting a delta-wound motor through a Y A starter, the metallic shorting links should be removed. Otherwise the starter will have a dead short-circuit at the motor terminal box and may burn the starter, damage the motor terminal box and even line cables. 

For installations prone to ignition and l ire, these cables can sustain fire for three hours as in lEC 60331. to minimize the extent of fire and consequent damage. 

The first few turns of the line end coil of a motor or transformer and short lengths of interconnecting cables and overhead lines and their associated terminal equipment, will thus be subject to severe stresses and will be rendered vulnerable to damage by such sleep-fronted transient voltages. 

The Journal fur Gasbeleuchtung mentions electrolytic corrosion damage caused by direct current cables in Berlin in 1892, and a few years later damage by tramway currents was reported in 14 German towns. As early as 1894 the electrolytic processes of stray current corrosion were explained in detail in this Journal by G.Rasch [65]. 

With impressed current stations on privately owned sites, it is advisable to conclude contracts with the property owner in order to guarantee access to the installation at all times, to prevent damage to the cables and to exclude construction or modifications in the area of the anode beds. 

The header cable between anode bed and rectifier must be particularly well insulated. For this reason cables with double plastic sheathing of type NYY-O are used. The cable sheath must not be damaged during installation because the copper core at the defects will be anodically attacked in a very short time and the connection to the rectifier broken. Damage to the cable sheath is not so serious if a multicored cable is used. Usually not all the core insulation is damaged so that the operation of the anode bed is not interrupted. In addition, measurement of resistance and detection of defects is easier. 

For several years now, cable ducts have been manufactured from plastic pipes, which are watertight and form a continuous run of piping. In laying the ducts, low points can occur in which condensed water or water penetrating from the ends can collect. In many cases this water has led to corrosion damage in lead-sheathed cables. Lead-sheathed cables must therefore only be used in such ducts with an additional PE sheath of type A-PM2Y. Cathodic protection of these cables is not possible because of their complete insulation by the plastic pipe. 

Cathodic protection with impressed current anodes is used predominantly with cables or steel casing in which the cable is inserted, outside built-up areas where it is possible to build large anode installations without damaging interference with other lines. In densely populated areas, protection with impressed current anodes is often only possible with deep anodes, with surface anodes or locally at individual problem points (local cathodic protection, see Chapter 12). 

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