Industrial Systems – Distribution
General Electric Current Limiting Power Fuses
Medium-voltage distribution systems that supply industrial plants, shopping centers, hospitals, schools, office buildings and underground residential service often require special types of overcurrent protection. This is of particular importance because, in the event of a fault, these types of systems frequently produce high short-circuit currents that may result in damage to busway, motors, switches and other equipment. Current-limiting power fuses are widely used in these applications because they afford excellent over-current protection and noiseless operation, and because they can be used in confined spaces. The amount of damage in the faulted area and the mechanical stress and strain on busway, switches and other apparatus carrying the fault current is proportional to the square of the current and to the length of time the fault persists. By limiting the letthrough energy at the fault, properly applied current-limiting fuses assist in limiting or preventing short-circuit damage to busway, circuit breakers, switches, and other electrical components. Current-limiting power fuses are manufactured in ratings ranging from 0.6 kV through 38 kV and in continuous current ratings from 0.5 amperes through 900 amperes. Various designs are available for use with motors, transformers, capacitors, and circuit-protection equipment.
Current-limiting power fuses offer significant advantages for protecting electrical power systems and equipment. Advantages include:
- High interrupting capacity
- Noiseless operation, since the interruption is totally contained
- Fast current-limiting operation when troublesome high available fault currents are encountered
- No pressure build-up, therefore, no vents or special reinforced compartments are required
9F60 Series, EJO-5 9F60, Suitable for use indoors or outdoors
Backup Capacitor current-limiting fuses are designed for individual capacitor protection. The EJO-5 can be used in any location (indoor or outdoor). The major purposes of such fusing are: (a) to protect the systems from failed capacitor units, and (b) to prevent damage to adjacent capacitors and associated equipment.
General Purpose Fuses
9F62 Series, EJO-1 General Purpose, UL Listed, Suitable for use indoors or outdoors
General Purpose current-limiting fuses are designed to interrupt the high-fault currents and also the low-fault currents down to approximately 1.6 to 2.2 times their continuous current rating. This fuse is defined in the IEEE Std C37.40 -1993 (3.1.57) as “A fuse capable of interrupting all currents from the rated interrupting current down to the current that causes melting of the fusible element in no less than one hour.” These fuses can be used outdoors without any protecting enclosure. Available from 5.5 to 15.5kV and 20 to 900A.
Power Distribution Fuses
9F60 Series, “E” Rated, EJ-1, Suitable for use indoors or in an enclosure only
Backup power distribution current-limiting fuses are designed not only to interrupt the high-fault currents but also to interrupt low-fault currents down to approximately 3 times their continuous rating.
9F60 Series, “E” Rated, EJO-1, Suitable for use indoors and outdoors
Backup power distribution current-limiting fuses are designed not only to interrupt the high-fault currents but also to interrupt low-fault currents down to approximately 3 times their continuous rating. The EJO-1 models can be used outdoors without any protecting enclosure.
Potential Transformer Fuses
9F60 Series, “E” Rated, EJ-1, Suitable for use indoors or in an enclosure
Backup current-limiting fuses are designed to interrupt the high-fault currents and also the low-fault currents down to approximately 3 times their continuous current rating. Available from 0.625 to 15kV, from 0.5 to 3 Amps.
Motor Starter Fuses
9F60 Series, “R” Rated, EJ-21, Suitable for use indoors or in an enclosure
Backup motor starter current-limiting power fuses are designed to provide short-circuit protection of individual motors. These fuses are designed to interrupt from 100 times the R-rating current up to 50kA rms symmetrical at rated voltage. The element of these fuses is designed to withstand the cyclic motor-starting application. By definition, a back-up current-limiting fuse is “A fuse capable of interrupting all currents from the rated maximum interrupting current down to the rated minimum interrupting current.” Standard IEEE C.37.40-1993 (3.1.8). Available from 2.54 to 7.20kV, From 70 to 700A (2 to 50R).
Fuse Supports and Disconnecting Switches
9F61 Series, EK-1, EKO-1, EK-3, EKO-3
Fuse supports, non-disconnecting, are used primarily in potential transformer circuits, or where there is some other disconnecting or isolating device in series with the fuse in the circuit. Fuse supports can be mounted vertically or horizontally. The EKO-1 models are designed to be installed outdoors. Disconnecting switch devices have the additional feature of serving to isolate the equipment they protect. It should be noted that disconnecting switches are not load-breaking devices, therefore, the circuit must be open prior to the fuse disconnection. The EKO-3 models are designed to be installed outdoors.
External Transformer Protection (ETP) Fuses
Backup current-limiting fuses designed to protect transformers are used in series with another protective device (such as an expulsion fuse). This combination limits the high-fault current to a safe level, thus providing protection through the complete range. As its name implies, the “ETP” is for External Transformer Protection. For conventional transformers protected by expulsion-fuse cutouts, the ETP can be installed in series with the cutout. For self-protected transformers, the ETP can be applied on the high-voltage bushing in series with the internal transformer expulsion fuse. From 8.3kV to 23kV and from 8T to 80K. Interrupting rating 50 kA Sym.