Medium Voltage Fuses Medium Voltage Fuses Section Contents Page Introduction ............................. 72 E-Rated Fues For transformers & feeders .75 CL-14 & bolt-in 76 CL-14 . 77 For potential & small power transformers 78-79 R-Rated fuses for motor circuit protection . 80-82 British IEC fuses for motor circuit protection . 83 DIN IEC fuses for transformer protection ...... 84 Potential transformer fuses ................. 85 British IEC fuses for oil-filled switchgear ...... 86 Fast-acting fuses ......................... 87 EEI-NEMA Type K & T and Type H & N fuses . 88 BBU Boric acid fuses ................... 89-90 Fuseclips for medium and high voltage fuses . 91 71Medium Voltage Fuses Medium Voltage Fuses 2. General Purpose defined by ANSI C37.40 as a fuse Worldwide Circuit Protection Solutions capable of interrupting all currents from the maximum rated Cooper Bussmann is a world-leading supplier of medium interrupting current down to the current that causes melting voltage fuses. Each product is backed by an efficient of the fusible element(s) in one hour. Not all currents fall worldwide distribution network with unrivaled service and within this range. It is possible for the fuse to be exposed to technical support. Cooper Bussmann circuit protection an overcurrent lower than the value given by the one hour solutions comply with major international standards: ANSI, criteria. In that case, a different overcurrent protection device BS, DIN, IEC and UL. would be required to interrupt the overcurrent. 3. Back-up defined by ANSI C37.40 as a fuse capable of Fuse Types interrupting all currents from the maximum interrupting rating current down to the minimum interrupting current. Medium voltage fuses generally fit into two categories The minimum interrupting current is the lowest current that expulsion fuses and current limiting fuses. The definitions per the fuse will be able to clear properly. This creates a need to ANSI C37.40 are: place a low current interrupting device, such as motor overloads, in series with the back-up rated fuse. Expulsion Fuse: A vented fuse in which the expulsion effect of the gases produced by internal arcing, either alone or E- and R-Rated Fuses aided by other mechanisms results in current interruption. Expulsion fuses will limit the duration of an overcurrent In North America, current limiting fuses typically fall into the event, but they will not limit the magnitude of fault current. category of E-Rated fuses and R-Rated fuses. Cooper Cooper Bussmann offers two types of expulsion fuses: Bussmann also offers a wide range of current limiting fuses replacement fuse links for fused cutouts and boric acid designed to BS, DIN and IEC standards. fuses. E-Rated fuses are used to protect feeder circuits, power Current Limiting Fuse: A fuse unit that, when in its current- transformers and potential transformers. E-Rated fuses have responsive element is melted by a current within the fuses defined current response times specified by ANSI C37.46. specified current-limiting range, abruptly introduces a high E-Rated fuses 100A and below must melt in 300sec at an resistance to reduce current magnitude and duration, rms current within the range of 200% to 240% of the resulting in subsequent current interruption. A current continuous current rating. E-Rated fuses above 100A must limiting fuse will reduce the magnitude a fault current as well melt in 600sec at an rms current within the range of 240% to as limit the duration of the overcurrent event when operating 264% of the continuous current rating of the fuse. Cooper in its current limiting range. Cooper Bussmann offers a broad Bussmann offers a wide variety of full range and general range of current limiting fuses for protection of feeders, purpose E-Rated fuses from 2.4kV up to 38kV. transformers and motor circuits designed to ANSI, BS, DIN and IEC standards. R-Rated fuses are back-up fuses that provide short-circuit protection for motor circuits. They are applied with MV motor Medium Voltage Current Limiting Fuses starters which provide the overload protection for the circuit. R-Rated fuses also have defined current response times Current limiting fuses are classified into three categories: specified by ANSI C37.46. R-Rated fuses will melt in a range of 15 35sec at a current equal to 100 times the R rating. Cooper Bussmann offers 2.4kV, 5.08kV, 7.2kV and 8.3kV 1. Full Range defined by ANSI C37.40 as a fuse capable R-Rated fuses for motor circuit protection. of interrupting all currents from the maximum rated interrupting current down to the minimum continuous current that causes the melting of the fusible element(s), when the fuse is applied at the maximum ambient temperature specified by the manufacturer. It is able to interrupt any current that will melt its element. For detailed information, visit the Electrical IEC section at www.cooperbussmann.com 72