2.4.3.7
Modular Inverter Isolation
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NOTE: Delete for single module UPS system.
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Each inverter in the UPS system shall have fault sensing and static
isolation as well as an output protective device, to remove a faulted
module from the system without affecting the critical load bus beyond the
stated limits.
2.4.4
External Protection
UPS module shall have built-in self-protection against undervoltage,
overvoltage, overcurrent and surges introduced on the ac input source
and/or the bypass source. The UPS system shall sustain input surges
without damage in accordance with IEEE C62.41. The UPS shall also have
built-in self-protection against overvoltage and voltage surges introduced
at the output terminals by paralleled sources, load switching, or circuit
breaker operation in the critical load distribution system.
2.4.5
Internal Protection
UPS module shall be self-protected against overcurrent, sudden changes in
output load and short circuits at the output terminals. UPS module shall
be provided with output reverse power detection which shall cause that
module to be disconnected from the critical load bus when output reverse
power is present. UPS module shall have built-in protection against
permanent damage to itself and the connected load for predictable types of
failure within itself and the connected load. At the end of battery
discharge limit, the module shall shut down without damage to internal
components.
2.4.6
Parallel Operation
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NOTE: Delete for single module UPS system.
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For parallel operation, the protection system shall have control logic
capable of isolating only the faulted module, and shall not shut down the
entire UPS system upon a fault in one module. Open protective devices
shall be indicated by an alarm and indicator light.
2.5
STATIC BYPASS TRANSFER SWITCH
A static bypass transfer switch shall be provided as an integral part of
the UPS and shall consist of a static switch and a bypass protective device
or bypass switch. The control logic shall contain an automatic transfer
circuit that senses the status of the inverter logic signals and alarm
conditions and provides an uninterrupted transfer of the load to the bypass
ac power source, without exceeding the transient limits specified herein,
when a malfunction occurs in the UPS or when an external overload condition
occurs. The power section of the static bypass transfer switch shall be
provided as a plug-in type assembly to facilitate maintenance. The static
bypass transfer switch shall be used to connect the bypass ac power source
or the UPS inverter output to the critical load when required, and shall
have the following features:
SECTION 16265A
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