In fairness to the original designers and manufacturers, these ACBs were well designed and very well made – so much so that many have kept working perfectly for decades. In expectation of long usage, they were often used in critical, continuous operation facilities, such as data centers. However, replacing a failed overload or older generation STR protection unit has frequently proved problematical because most original manufacturers no longer provide support. Instead, they typically recommend simply replacing the old ACB with their current production model. This can be expensive in terms of the equipment required and, often much more significantly, demands significant downtime as the switchgear has to be replaced as well as the breakers.
Nuisance tripping is, by definition, a false alarm, a fault of the STR protection unit, not an indication of an indication of a genuine problem. Unfortunately, identifying that it is the protection unit, not the wider system, that is at fault, is not easy, especially as we are all trained to assume the worst – ie a more serious, wider problem. Repeated power outages are a major problem in themselves though, which is why many operators with older units look for a preventative solution, rather than wait for older units to start ‘playing up’.
Happily, preventing nuisance tripping can be much simpler and less expensive, thanks to the development of product specific upgrades by reputable manufacturers.These allow old ACBs to be updated with sophisticated electronic controls which allow the rest of the unit to continue to function reliably.
Most power circuit breakers presently in use have already been retrofitted with older generation solid state trip units, but many users are choosing to upgrade these breakers with the state of the art units, such as PS Electrical’s Amp-Safe-Pro, because it provides improved metering and selectivity and has many features unavailable on lesser units. Most importantly, it significantly improves safety for the operator with features such as duplication of all the original trip curves, ‘Quick-Trip’ arc flash reduction system, an OLED display showing data for the last eight trip events and a GUI for uploading settings and downloading trip data via a USB.
A typical upgrade includes an electronic trip unit with display module, current sensors, automatic reset actuator, wiring harness, mounting brackets and/or copper shunts. The remote mountable display can be installed outside the switchgear so workers do not need to ‘suit up’ to view loads, settings and trip history. The backlight displays function as an accurate 3-phase ammeter, displaying ground fault current in real time. No controls, redundant displays or batteries are inside of the cubicle. This eliminates most of the instances where workers would need to open the door on racked-in breakers.