CLiP Concept

CLiP® (Current Limiting Protector) has provided unparalleled system protection, around the world, for over  25 years. It offers the advantages of current limitation for systems rated to 38kV with high continuous current ratings up to 5000A. Fault interruption beyond 300kA rms symmetrical at 15.5kV has been achieved.

The CLiP is an electronically sensed and triggered, commutating form of current limiter, sometimes referred to generically as an Is-Limiter, where a continuous copper bus bar path carries the continuous current. This path is opened under overcurrent conditions to introduce a parallel mounted current limiting fuse which interrupts the fault.



With the ever-increasing demand for electrical energy, distribution systems have been forced to expand and grow. Stiffened transmission systems, increased substation capacity, onsite and distributed generation all contribute to subsequent increases in available fault currents imposed on equipment. This short circuit current may exceed its thermal, mechanical and interrupt capability, potentially causing a catastrophic failure. The CLiP is a tool to prevent this.

Current limitation is a key benefit because it yields a significant reduction in the magnitude of the peak let-thru current. Also, since electromechanical forces and fault energy are related to the mathematical square of the current value, limitation of the peak current has a dramatic affect. This can lead to substantial savings by reducing damage, and may also prevent the catastrophic failure of oil filled equipment, or greatly limit arc flash exposure.


Traditionally, the current limiting fuse has provided good overcurrent protection on systems with normal continuous currents up to a few hundred amperes. Their current limitation capability, speed of operation, compact size and low cost make them ideal solutions for certain applications . Expulsion fuses also fill a need. Yet, while these devices are relatively fast acting, they are unable to limit the destructive forces related to the peak currents. Electromagnetic forces and fault energy are related to the square of these unlimited peak current values.


For higher continuous currents, circuit breakers are most commonly used. However, circuit breakers are not current limiting and are relatively slow interrupting devices (3-5 cycles). The application of a CLiP for protection of  under-rated circuit breakers can provide significantly improved protection at a substantial cost savings over replacement of those circuit breakers. For applications where available fault currents have increased due to expanding power requirements, simply replacing the circuit breakers may not be adequate protection for other under-rated equipment on the system.

Another device is the current limiting reactor. Reactors have high continuous current capabilities and are current limiting. However, they require an auxiliary device to do the actual fault interruption. Reactors are inherently costly to operate because they introduce substantial losses to the system and impose an undesirable regulating voltage.

CLiP is the successful result of a project sponsored by the Electric Power Research Institute (EPRI), to develop a cost effective, single-shot, high continuous current, medium voltage current limiter for use indoors or out. These are five highly desirable elements never before available in one overcurrent protection device.

Clip Brochure