Choosing Breaking Capacity
Calculation of the required breaking capacity involves determining the supply impedance and voltage. Supply impedance is calculated from the impedance of the elements making up the supply system. Customers of an electrical supply utility can request the maximum value of prospective short circuit current available at their point of supply. Networks involving multiple sources of current, such as multiple generators, electric motors, and with variable interconnections may be analyzed using computer software. A system study will generally consider the maximum case of additions of generation and interconnection out to some projected horizon year, to allow for system growth during the useful life of the studied installation. Since practical calculations involve a number of approximations and estimates, some judgment is required in applying the results of a short-circuit calculation to the selection of apparatus.
Some applications have low short circuit current so any fault current protector will suffice. This is typical for supplies from miniature transformers as used in control circuits. In large systems such as industrial power centers or utility networks, fault currents can be very high and selection of a suitably rated device is important.
Read more about this topic: Breaking Capacity
Famous quotes containing the words choosing, breaking and/or capacity:
“To throw obstacles in the way of a complete education is like putting out the eyes; to deny the rights of property is like cutting off the hands. To refuse political equality is like robbing the ostracized of all self-respect, of credit in the market place, of recompense in the world of work, of a voice in choosing those who make and administer the law, a choice in the jury before whom they are tried, and in the judge who decides their punishment.”
—Elizabeth Cady Stanton (1815–1902)
“[T]here is no breaking out of the intentional vocabulary by explaining its members in other terms.”
—Willard Van Orman Quine (b. 1908)
“If the only new thing we have to offer is an improved version of the past, then today can only be inferior to yesterday. Hypnotised by images of the past, we risk losing all capacity for creative change.”
—Robert Hewison (b. 1943)