Mineral insulated copper sheathed cable

MIMNS cable is extemely robust and , when properly installed , has an indefinite life . It can be used outdoors and for usch use is usually supplied with an overall covering of pVC . It is then known as MIMS PVC sheathed . Since PVC is embrittled with ultraviolet light , this PVC covered cable should not be installed where it will exposed to direct sunlight . THis is not as drastic a restriction on its use as may appear since it is probably unwise to run any cable where it is so exposed that direct sunlight can reach it . In any such situattion , it would also be too vulnerable to damage by vandalism and from animals . because of its robustness , MIMS requires no further protection , but will not withstand being struck by sharp objects. It is , therefore , more easily built into the structure of a building than other cables , nearly all of which must have some form of enclosure around them . Because it has an idenfinite life . There is no need for facilities to make it possible to reqire the installation . For both these reasons , it can often be used where no other cable would be entirely satisfactry . MIMS cable can carry a higher current than other cables with same size conductors because the insulation can withstand a higher conductor operating temperature . However , its current carrying capacity depends on wheather it is bare , PVC-covered , exposed to touch , or in contact with a combustible materials .IT follows that for a given current the cable can be smaller if MIMS is used than if another type of cable is used . This is very useful property which makes it possible to conceal MIMS cable in corners which are not large enough to hide the larger cable that would have to be used with another system .
  The magnesium oxide insulation is hygroscopic and will lose its insulating properties if left unprotected against the ingress of moisture from the atmosphere . To prevent this happening , MIMS cable must be terminated in special seals and glands , which are supplied for the purpose by the cable manufacturers . IF the cable is cut and the ends left unsealed for any length of time , as can happen in the course of work on building sites , moisture can penetrate  the insulation and render the cable useless . In most cases , however , moisture will penetrate unsealed ends for olny a short distance of not more than 50mm . It is then sufficient to cut off the damaged end of the cable , fter which the remainder can be used in the normal way . If the cable is carrying full rated current , it will operate at about 90 celcius ; care must be taken that the accessory or luminaire to which the cable is connected is designed to withstand 90 celcius .