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132
PCS100 UPS-I User Manual
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16 PROTECTION REQUIREMENTS
16.1 Input Circuit Protection
The PCS100 UPS-I relies upon upstream protection for current overload and short circuit protection. Upstream
protection should be provided by a circuit breaker.
16.2 Short Circuit Protection
The power system fault current (kA) must not exceed the fault capacity of the PCS100 UPS-I. A circuit breaker that
is set to clear a short circuit failure (within the PCS100 UPS-I's withstand period) is required. For PCS100 UPS-I
fault capacities and withstand periods refer to the model tables earlier in this catalogue.
Withstand period is not applicable to PCS100 UPS-I models that have a Utility Disconnect rated at 900 A or less.
These PCS100 UPS-I models require current limiting 'molded case circuit breakers' (MCCBs). Current limiting
MCCBs provide very fast clearing of short circuit fault currents. ABB T5 or T6 Series MCCBs or equivalents are
suitable.
16.3 Input Overload Protection – Utility Disconnect
The power system circuit breaker should be set to the overload capability stated for the utility input in the
specification section of this catalogue.
16.4 Arc Fault Protection
16.4.1
Arc Fault and Standards
Arc faults may happen due to unexpected occurrences and are often triggered by a service person with
consequently high risk of harm from the arc. Arcs can cause lethal injury from burns, pressure and flying
debris. Generally, the risk is in proportion to the energy of the fault current and time of exposure.
Safety issues in respect or arc faults are considered in the USA National Fire Protection Association NFPA 70E
Standard for Electrical Safety in the Workplace. At this time there is no equivalent European standard. In the
USA, NFPA 70E (and associated standards) mandates:
•
Assessment of whether there are arc flash hazards (if the electrical equipment was de-energized, for example,
the hazard would not be present)
•
Calculation of the energy released by the arc, if present
•
Determination the flash protection boundary
•
Provision of appropriate personal protective equipment (PPE) for the personnel working within the flash
protection boundary
•
Appropriately label the equipment. These warning labels are placed on the equipment by the plant owner and
not by the manufacturer. The labels shall indicate the minimum protective distance, the energy level which
can be released and the required personal protective equipment (PPE).
Such study is required for all US installations.
NFPA 70E Annex D (referencing references IEEE Standard 1584-2002 - IEEE Guide for Performing Arc Flash Hazard
Calculations) provides guidance on calculation of fault energies, protection boundaries, PPE and labelling.
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