The entry of power and control cables, maybe from the top or bottom. Which needs to be agreed upon before ordering of a switch gear. A full height cabling alley on the right hand side of functional units, is normally available to facilitate cabling. In addition, a full width cabling chamber can be made available at top or bottom of the functional unit, like ACBs depending upon cable entry arrangement. Normally, a full metal partition plate is provided for segregation between the module and cable alley. Though it is not uncommon to use switchgear with top cable entry, bottom cable entry is preferred. Advantages are ease of accessibility for inspection and maintenance, aesthetically better as the supports are inside the cable cellar or trench. Avoids possibility of any entry of water particle from A/C ducts or fire hydrant line. Accumulation of heat or improper dissipation can lead to higher temperature rise. Higher temperature rise could shorten the life expectancy of insulating material and hence the life expectancy of switchgear itself. Individual components, may also get damaged due to higher temperature rise. Factors to be considered while designing the type of cooling off switch gear, power loss in the equipment, upper limit for temperature rise, effective cooling surface area and allowable enclosure temperature. LV switchgear are generally naturally cool to limit the allowable temperature rise. However, with switchgear of higher current ratings, the degree of ingress protection is required to be reduced by providing additional lowers to facilitate better cooling and heat transfer. Forced air cooling using additional fans is also adopted, in case of switchgear of higher current rating. In such cases it could be prudent to provide redundant fans, so that failure of one fan shall not jeopardize the operational requirement of the switchgear. Forced cooling is not generally favored in the industry. Let us discuss now, forms of construction for LV switchgear. The design of switchgear will change depending on the requirement of increased level of segregation and flexibility. This will result in increased size and cost of switchgear. Engineers shall carefully evaluate the cost benefit prior to selection. IEC 61439-2, indicates standardized forms of construction and as of four times.. As a rule one may consider that increased level of segregation improves safe maintenance access. Inform one construction, you can observe that the Busbars, functional units and outgoing terminals are kept in the same enclosure without any segregation. Though, buzz bars and functional units are segregated in form 2A and 2B type of construction. Safe access to cables terminated at a functional unit is not guaranteed, without shutting down of adjacent or nearby functional units. Such constructions are usually of wall mounted design. Each functional unit is in each respective compartment. In this form, busbar is segregated from the functional units and the functional units are segregated from each other. The terminals for external cables are segregated from the functional units but not from one another. In this warm, separation of Busbars from the functional units and the segregation of all functional units, including the terminals for external conductors from each other is achieved. You would have noted from the definition of forms of construction, form 4B allows maximum flexibility and safe access to one functional unit or cable while the other unit is life. If segregation is designed with proper IP degree, that is IP 41 and about usage of tools and small falling objects as screws, bolts or washers from a compartment under maintenance, will not lead to any short circuit. Or flash over in the adjacent life compartment. Similar IP degree is difficult to achieve for the barriers between switching compartment and cable compartment. As cables are required to be connected to conductors, which come out of the switching compartment. All cables meant for several switching modules are taken through one common cable compartment in form four a type of construction and connected to conductors of each outgoing switching module. Hence it would be very difficult to provide barrier between cables of different switching modules inform foray to enable maintenance access to one module when others are live rigid shrouds are normally provided to ensure safe maintenance axes. In such cases here's a quick recap of what you've learned as far depending on the application or usage. LV switchgear may also be called as power control center, motor control center. Power come motor control center ups, distribution board Dc, distribution board, distribution board minimum I. P. 41 of ingress protection to be provided for LV switchgear installed indoors. M C B. S are usually mounted in a fixed version on a C channel called din drill. M C C B. S. Or S. F. U. S. R. A C B s can be mounted in a fixed version or draw out version. Drought version of a circuit breaker has three positions, service position, test position and isolated position. LV switchgear generally comprises of three compartments. They are Busbars, circuit breakers or M. C. C. B. S. Or switch views compartments. Or we can call in a generalized way as functional units, cable compartment, the entry of power, uncontrolled cables maybe from the top or bottom. A full height cabling alley on the side of functional units is available to facilitate cabling accumulation of heat or improper dissipation can lead to higher temperature rise and failure of switchgear or its components. Natural cooling of LV switchgear is preferred. Forced air cooling is not preferred. However, same is adopted for higher current, treating i. E. C 61439-2 indicates standardized forms of construction for a switchgear and is of four types form one form to A. B. Form three a. b. and Form four a. b. From four B. provides highest level of segregation and safe maintenance access
