Eaton’s Digital NZM Moulded Case Circuit Breaker.
Zone Selective Interlocking (ZSI) is a communication scheme used with digital MCCBs to improve the level of protection in a power distribution system. Through using ZSI across the power distribution zones, enhanced levels of protection can be achieved by ensuring the MCCB closest to a fault trips first, ensuring that power to the other circuits remains unaffected. This is paramount for critical infrastructure where a complete blackout could have severe financial, as well as human implications – such as hospitals.
How ZSI limits the stress on the electrical distribution system and guarantees selectivity?
ZSI works in a coordinated distribution system to limit stress on itself by reducing the time it takes to clear the electrical fault while maintaining system coordination between overcurrent and protective devices.
By introducing time-delays within protective devices, signals are sent via the trip units ZSI function upstream to identify a fault and remain closed for the pre-set time delay, this coupled with not having a time delay on the final circuit protection, ensures that the device closest to the fault will trip without a time delay, therefore reducing the fault clearing time and reducing the stress on the distribution system.
How does ZSI introduce cost savings?
ZSI can aid cost savings by ensuring that any fault occurring within the system, is limited to the singular affected area, ensuring that any downtime caused by the fault, and associated costs, are minimized to the affected area.Find out more by downloading our webinar here.