Faults to ground occur generally in one of two ways: (1) An energized conductor will contact a grounded point, creating sparks, smoke or fire. This will usually trip the over current protection, either a circuit breaker or fuses. But metal will incandence with a fault of just 500 milliamps. (2) Insulation deteriorates causing low level current to pass to earth. This failure will seldom create enough fault current to trip a breaker or blow a fuse. The former fault occurs instantaneously, but the latter often occurs very slowly, and it occurs very frequently. This creates hazardous conditions putting operators and maintenance personnel at risk for electrocution, and increasing the probability the equipment will be damaged, resulting in production stoppage.
AGT Ground Fault Indicators Use Proven Zero Sum Technology to Detect Earth Leakage
NK Technologies’ new loop powered sensor for monitoring earth leakage is based on proven, zero sum current technology. This new sensor produces a constant signal proportional to the leakage current. The industry standard 4-20mA output can be connected to a PLC or data logger, with the 4mA signal representing no earth leakage, and 20mA representing fault current of either 50 or 100mA (dependant upon choice of unit).
As the insulation degrades the fault current increases. The controller can be programmed to alarm at one level, for example, 15 mA and disconnect the load if the fault increases over 30mA. These parameters can be established in advance by the design engineer, and are easily programmed in the controller.
Monitoring residual earth leakage current is required in many applications, from electrical heating elements to water fountain pumps. Using a constant signal proportional to the fault current will help protect any electrically driven machine or process.
Ground Fault Monitoring
Current Leakage Detection
- Monitoring heating or other loads to detect increasing leakage current
- Pass all current carrying conductors through aperture to sense zero-sum current
Monitoring Very Light Loads
- Measure very small, critical loads accurately
- Current measurement gives faster response
than temperature measurement