Link Belt is a leader in the design, manufacturing, and sales of telescopic and lattice boom cranes. They have been very progressive in their efforts to adopt arc flash mitigation measures.
Low voltage switchgear and switchboards can be subjected to dangerous levels of arc flash incident energy when fed directly from a power transformer such as a unit substation. A virtual main system reduces the arc flash energy on the entire low voltage switchgear, including the main incoming section. A virtual main system consists of a digital relay and overcurrent sensing that is added to the low voltage side of the service transformer and is designed to trip an existing upstream fault breaking device.
Link Belt chose to add this system to three existing unit substations in their main manufacturing facility. Parsons partnered with Square D Services to design and install this system on the selected substations.
An engineering study to evaluate the optimum settings for the relays and circuit breakers in the substations was undertaken.
A switching device with fault interruption capability on the high voltage side of the service transformer was added on each of the three substations. Three relaying class current transformers were installed on the secondary side of the transformer. A self-contained relay package including a microprocessor-based relay and the necessary terminal blocks, pilot lights, and selector switches were also included.
