Short Circuit and Coordination Studies

Short Circuit and Coordination Studies
Ensure the
Integrity of
Your Electrical
Avoid unnecessary
damage to equipment
For Business-Critical Continuity™
An Evaluation of Your Electrical System’s
Protective Devices
Short Circuit and Coordination Studies from Emerson Network
Power Service are ideal for facilities undergoing power infrastructure
enhancements or facilities that have experienced load changes.
Inadequately rated or uncoordinated protective equipment can cause
extensive damage to your systems, lead to prolonged downtime, and
even result in personnel injury.
Ensure personnel safety
Reduce downtime when a
fault does occur
Isolate faulty circuits
without loss of power to
other parts of the system
Identify under-protected
equipment before it’s
too late
Short Circuit Study — Determines the magnitude of fault current
and whether equipment is properly rated to interrupt or withstand the
short circuit.
Protective Device Coordination Study — Determines characteristics,
settings and sizes to evaluate whether protective devices are coordinated
to isolate faulty equipment in a manner which will maintain a balance
between equipment protection and selective device operation.
Ensuring the
Safety and
Reliability of Your
Critical Power
4. Bringing Down Your Entire Operation
Due to poor breaker coordination the
short circuit trips all the way back to the
main breaker – shutting power down to
your entire facility.
Your critical electrical distribution system is the
foundation of your entire operation. Knowing you
have an accurate picture of your power system’s
ability to safely handle fault conditions is key to
achieving the level of availability that is necessary to
sustain business continuity.
With our Short Circuit and Coordination Studies,
Emerson Network Power Service will provide a
comprehensive, detailed and accurate assessment of
your power system’s protective device capabilities.
Utility Source
3. Causing Equipment Damage
At minimum, the short circuit destroys
the improperly rated breaker. At
worst, the arc causes damage to other
equipment including switchgear.
1. A Fault Occurs
A faulty piece of equipment in one of
your mini-computer rooms creates a
Short Circuit.
2. An Improperly Rated Breaker Arcs
The distribution breaker designed to
localize the risk and de-energize the area
is improperly rated. The short circuit arcs
through the breaker, and escalates up
the facility.
A short circuit can create unforeseen,
unacceptable problems for your
facility. Ensuring the proper rating and
coordination of your breaker systems
reduces unexpected downtime and the
risk of equipment damage from short
circuit risks.
Short Circuit Study
Protective Device Coordination Study
Determine the short circuit current available at each
component of the electrical system and confirm
whether the component is rated to withstand and/or
interrupt the current. Analyze all possible operating
scenarios influenced by additions or changes to the
electrical system.
Coordination Studies are performed to ensure
minimum service interruption under overload and
short circuit conditions.
What We Do:
Review panel and device data, feeder sizes and
lengths, transformer nameplate information,
generator and automatic transfer switch data
(where they exist) and utility source information.
Perform short circuit analysis, protective device
evaluation and protective device coordination.
Studies will be performed using SKM PowerTools
for Windows software.
Identify any suspect equipment, recommended
corrective action and device settings to allow
for selective coordination of protective devices
consistent with system operation.
Provide a summary table that compares the
available fault currents to the withstand rating of
the equipment and devices within the study.
Test the devices at the recommended settings to
assure operation within the manufacturer’s tolerances.
It will ensure the protective device closest to the
overload or short circuit condition is the one that
operates in order to isolate the failure as quickly as
possible. If the circuit breaker or other protective
devices are improperly set too low, or not rated for
the available in-rush current from an upstream feeder,
then the protective devices may trip unnecessarily
causing critical loads to be dropped. Conversely, if
protective devices are improperly set too high then the
protective device closest to the failure may not trip at
all, causing another protective device further upstream
to trip –- the result, an outage to a much larger part of
your distribution system and possibly even a complete
blackout of your facility.
What We Do:
Evaluate and select proper settings or sizes for
relays, breakers and fuses.
Compare the operating levels and times of the
protective devices to withstand levels and times
that the equipment can sustain without damage
or failure.
Identify and recommend corrective action for
under-protected equipment.
What You Get:
A detailed report that includes:
A full description of the basis, purpose and scope
of the study.
Tabulations of the data used to model system
components and a corresponding one-line diagram.
Descriptions of the scenarios evaluated and
identification of the scenario used to evaluate
equipment short circuit ratings.
Tabulations of equipment short circuit ratings
versus available fault duties. The tabulation
identifies percentage of rated short circuit and
clearly note equipment with insufficient ratings.
Conclusions and recommendations.
What You Get:
A detailed report that includes:
The basis, description, purpose and scope of the
study plus a corresponding one-line diagram.
Time-current curves demonstrating the coordination
of time-overcurrent protective devices.
Tabulations of protective devices identifying
circuit location, manufacturer, type, range of
adjustment, IEEE device number, current
transformer ratios, recommended settings or
device size, and referenced time-current curve.
Conclusions and recommendations.
The Largest Service Organization
in the World Dedicated to Maximizing
Availability of Infrastructure Required for
Mission-Critical Systems
Emerson Network Power
Liebert Services
610 Executive Campus Drive
Westerville, Ohio 43082 USA
614 841 6400 Phone
614 841 6405 FAX
[email protected] Email
DC Power
Customer Resolution Center
Mission Critical
While every precaution has been taken to ensure
accuracy and completeness in this literature,
Emerson Network Power, Inc. and Emerson
Electric Power Co. assume no responsibility, and
disclaim all liability for damages resulting from use
of this information or for any errors or omissions.
Emerson Network Power, Inc. is a division of
Emerson Electric Power.
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