can some one clearly explain why -48 volt DC use in telecom site????


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There are two nos of 33Kv/11Kv 5MVA transformers conecting through HT cable from substation having metering at substation itself.One transformer used at a time another remains stand by.Further 11 nos of 11Kv/440V transformers are attached on it and each transformer is having its own Power factor correction panel.Now one 33/11Kv transformer at no load condition/Stand by condition is having power factor in leading side upto 0.21 and while when another tranformer at same situation have power factor in lagging 0.42. Now one thing is clear that transformer one is having 1.5 Km long 33kv cable due to that PF goes in leading side and another is having only 250 mtr length remains him lagging. Now i want to know that how i can maintain the Power factor at no load/ stand by position though both are behaving in seperate manner.

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