NX Fuses
NX Indoor Current Limiting FuseS
GENERALCooper Power Systems Type NX current-limiting fuses provideoverload protection for all indoor and underground cable distribution systems 2.4 through 34.5 kV. NX fuses are noiseless and expel no hot gases or burning particles while interrupting currents from minimum melt to maximum fuse rating (50,000 A through 23 kV, 35,000 A through 27 and 38 kV). Their currentlimiting capability greatly reduces the momentary duty on protected equipment, extending the life and, in some cases, reducing the original cost of that equipment.
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The ability of an NX fuse to interrupt low-current faults eliminates the need for auxiliary devices to handle these
troublesome current levels. An NX fuse extends system coordination because it is fast clearing and current-limiting
– conductor and equipment damage caused by high currents is virtually eliminated.
CLIP-STYLE NX FUSE
The basic NX fuse unit is designed to mount in a clip-style mounting. Basic clip-style NX fuses are available in 4.3, 5.5, 8.3, 15.5, 23, 27, and 38 kV ratings.
NX FUSE WITH ARC-STRANGLER LOADBREAK DEVICE
An NX fuse with an Arc-Strangler loadbreaking device, (see Figure 2) that mounts in a hinge-style mounting is available on 4.3, 5.5, 8.3, and 15.5 kV fuses. All current magnitudes from excitation current through 200 A can
be interrupted positively and safely by opening the fuse with a switch disconnect stick.
These units have the same operating characteristics as the basic clipstyle fuse, along with loadbreaking capabilities.
Arc-Strangler Switchblade
Switchblades with the Arc-Strangler
loadbreaking device are available in 8.3 and 15.5 kV, 200 A.
NX® Companion® Il Back-up Current-Limiting Fuse |
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GENERALThe Cooper Power Systems NX® Companion® ll fuse is designed to be conveniently applied as an add-on, back-up, currentlimiting fuse. The Companion II back-up fuse will interrupt high fault current and at the same time, limit the amount of energy that is let-through to the protected equipment. This fuse is designed to be applied in series with an expulsion or other type of weak link fuse. This series connected fuse must be capable of interrupting both excessive overload currents and low to intermediate fault currents up through the minimum interrupting rating of the Companion II fuse. If the expulsion fuse is applied within the recommended guidelines, enough current will be let-through to melt the expulsion fuse. When the expulsion fuse is in a cutout, the resulting drop open action provides, in any fault situation, a positive blown fuse indication for operating personnel. |
The majority of faults on distribution systems are of low magnitude (such as transformer overloads or incipient faults), and normally only the lower cost expulsion fuse melt and clear the fault. The available fault current on many overhead distribution systems, however, has grown beyond the interrupting ratings of the expulsion fuse. When
the Companion II fuse is used, and a higher magnitude fault current occurs, the possibility of eventful transformer failure is greatly reduced.
The Companion II fuse offers major advantages over other back-up, current-limiting fuses in the industry. This design offers a small, compact, reliable fuse that is easier to handle in field installations. The modular design also offers greater flexibility in the selection of terminal options and the ability to re-use the terminals after a fuse operation.
Every Companion II fuse is I2t tested. This assures operation of the fuse only at published minimum melt I2t levels and above, guaranteeing that a Companion II fuse will not be susceptible to nuisance operations at lower I2t levels. This Cooper Power Systems patented quality-control test detects defects that cannot be identified by any
other test procedure, including resistance checks and x-rays. The standard 8.3 kV and 17.2 kV, 25 K Companion II fuse is also manufactured as a “Tandem ELF™ Ready” fuse and can be used in the Cooper Power Systems Tandem
ELF fuse product. The Tandem ELF fuse combines the series fuse link and Companion II fuse in one hookstick
removable design which eliminates the need to separately connect the Companion II fuse.
MINIMIZES EQUIPMENT DAMAGE
The Companion II back-up currentlimiting fuse will interrupt high magnitude fault currents while also limiting the amount of current and energy let-through to the transformer. The back-up current-limiting fuse will limit the let-through current to minimize the possibility of transformer tank rupture from high magnitude internal faults or to minimize damage to the tank or bushing that might result from bushing flashovers.ENHANCED POWER QUALITY AND IMPROVED SERVICE CONTINUITY
The operation of the Companion II back-up current-limiting fuse will enhance power quality of the system and improve service continuity during high magnitude faults. The duration of the voltage dip associated with system short circuits will be limited to the short melt time of the Companion II fuse. Immediately after melting, the arc voltage generated by the current-limiting fuse will support system voltage until the fault is interrupted by the fuse. For high fault currents, the duration of the voltage dip associated with the melt time of the Companion II fusewill be well within the allowable limits for sensitive electronic equipment as defined by CBEMA curves.
Isolation Link
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GENERALCooper Power Systems isolation links provide extra protection during refusing and switching operations when used in series with a Bay-O-Net type fuse or MagneX Interrupter.Isolation links are not fuses and do not have an interrupting rating. During a transformer failure, the isolation link will melt so that the opened primary circuit of a faulted transformer cannot be re-energized by the line crew. |
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APPLICATIONS - BAY-O-NET ASSEMBLIES
Isolation links are used in series with Cooper Power Systems Bay-O-Net type expulsion fuses to provide extra
protection during re-fusing operations. They are coordinated to operate at high current levels that are typical of a
transformer failure.
MAGNEX INTERRUPTER
Isolation links are also used in series with the Cooper Power Systems MagneX Interrupter to provide extra protection during switching operations. The MagneX isolation link has arc shortening tabs to reduce the arc
length and thus reduce the I2t energy released during operation. They are coordinated to operate at high current
levels that are typical of a transformer failure.
INSTALLATION
No special tools are required. Isolation links are bolted onto Bay-O-Net fuse assemblies or MagneX Interrupters inseries between the primary transformer bushing and primary coil.
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CMU Medium Voltage Power Fuses |
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GENERALThe Cooper Power Systems CMU Power Fuse is a boric acid, expulsionstyle fuse. Suitable for both indoor and outdoor applications, the CMU Power Fuse provides an economical alternative to refillable fuses. |
CMU Expulsion Power Fuses are available in 3 maximum voltage classes: 17 kV, 27 kV, and 38 kV. The replaceable
fuse unit comes in 3 speed variations: Standard “E”, Slow “E”, and “K”. Amperage sizes range from 3 A through 200 A.The CMU Power Fuse interrupting rating greatly exceeds that of conventional distribution cutouts that uses a fiber tube and fuse link design, and considerably reduces the hazards and noise of the violent exhaust common to cutouts under fault interrupting conditions. The CMU Power Fuse, employing the use of calibrated silver element, boric acid for its interrupting media and rod mechanism for arc extension, creates low arcing voltage and mild exhaust during fault interruption.
APPLICATION
The CMU Power Fuses provide effective protection for circuits and equipment which operate on system voltages up to 34,500 V. They can be used on both electric utility and industrial distribution systems. Typical applications include:
■ Power Transformers■ Feeder Circuits
■ Distribution Transformers
■ Potential Transformers
■ Station Service Transformers
■ Metal-enclosed Switchgear
■ Pad-Mount Switches
■ Overhead Capacitor Racks
CMU Power Fuses can be used in outdoor or indoor applications, and can be used to directly replace competitive
equivalent units.
When used in upstream system protection, the CMU Power Fuse operates promptly to limit the stress on electrical systems due to short circuits. It provides isolation for the faulted circuit, limiting the size of interrupted service area.
Full protection is provided for downstream equipment, even down to minimum melt current, regardless of the nature of the fault. The CMU Power Fuse acts rapidly to take transformer and feeder circuits off-line before
damage can become widespread.
It provides excellent isolation for capacitors as well in the event of a fault condition. When installed on the primary side of substation power transformers, CMU Power Fuses provide protection against small, medium or large faults.
PRODUCTION TESTS
Tests are conducted in accordance with Cooper Power Systems quality assurance requirements.■ Physical Inspection
■ Micro-Ohm Resistance Testing
■ Construction Integrity Testing
INSTALLATION
No special tools are required to install the CMU Power Fuse. The CMU Power Fuse and end fittings are designed tofit into industry standard mountings.
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JOE E-Rated Current-Limiting Power Fuses |
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GENERALThe Cooper Power Systems JOE current-limiting power fuses areE-Rated per IEEE Std C37.46™ standard, providing an excellent choice for protection of transformers, feeder circuits, high voltage switchgear, and metal-enclosed switchgear. Voltage ratings include 5.5 kV and 15.5 kV. The fuses have either 2” or 3” diameter barrels (sometimes double-barrel) as indicated, and have standard clip center distances of 12”, 15” or 18”. The fuses have ferrules for mounting in standard spring-reinforced clips, providing interchangeability with other brands of fuses. In addition, the fuses are equipped with blownfuse indicators to provide positive identification of the open fuse. Cooper’s JOE current-limiting power fuses meet the IEEE Std C37.40™ standard definition for full-range current limiting fuses, providing superior protection to general-purposefusing alternatives. Cooper’s currentlimiting |
currents. The fuses’ current-limiting capability limits both peak current magnitude and fault duration, thus
limiting the total I2t let-through energy.
fuses are designed to meet the stringent needs of industrial and utility applications. The noiseless operation
and lack of expulsion byproducts make them ideal for indoor application in confined spaces. They fit in industrystandard power fuse mountings and are suitable for both indoor and outdoor installations. These E-Rated
fuses have time-current characteristics that allow easy coordination with other upstream and downstream protective devices. Cooper’s current-limiting power fuses are used to protect transformers, feeder circuits, high
voltage switchgear, metal-enclosed switchgear and other equipment that can benefit from their energy-limiting
properties.
INSTALLATION
No special tools are required. The JOE fuse is designed for indoor and outdoor mounting in industry standard in-air clip mountings and fused disconnect switches.Back to top
For additional information on McGraw Edison Fuses contact us at 918.665.6888, or use our fuse search tab at the top of the page. You can also request a quote on any of the McGraw Edison Fuses using our quote form.