ELCI stands for "Equipment (sometimes "Earth") Leakage Circuit Interrupter", and is a device intended to mitigate ground fault leakage specifically for the protection of equipment. A "GFCI" (Ground Fault Circuit Interrupter) is essentially the same as an "ELCI", but for the most part differ in trip threshold of leakage current and/or circuit voltage. A "GFCI" indicates that "Personnel" protection is being provided. This calls for a trip threshold of 4 to 6 mA with a maximum response time of 25ms and circuit voltage from any single current carrying conductor to Ground cannot exceed 150V. Thus, even if a 4 to 6 mA trip threshold is employed, on a 480V circuit, or even a 240V elevated (L1, N), providing personnel protection is not feasible. In order to provide personnel the greatest level of protection given circuit criteria, use of an "ELCI" is prescribed for personnel protection. Other applications for "ELCI" devices may call for higher trip thresholds of 10, 30, or even 100mA as baseline leakage as some of these applications may well exceed 6mA when a load device is functioning properly.
Safety concerns have been raised over the last decade over the Electrical Shock Hazards that have been associated with municipal and roadway lighting systems. Insulation breakdown from aging infrastructure has been documented from coast to coast (see these articles for reference), along with missing access covers, animal penetration, wind damage, water damage, and salt corrosion. Implementing the use of an ELCI will help eliminate these hazards and reduce the liability associated.
An ELCI can easily be employed or retrofitted into existing systems. The image to the far left shows an ELCI incorporated into a PCDS.
The ELCI in the photo is designed for a 480V system with a 6mA Trip threshold for protection against electrical shocks. (click images to enlarge)