Maintenance Technology July 2017 - 11

PLANT PROFILE

WHEN ELECTRIC CURRENT flows through an air
gap between conductors, it creates an arc flash. Sparks
fly, equipment can explode, and anyone who happens
to be nearby can be injured-or even killed.
"The heat and light energy radiating from an arc
flash is so intense it can do extensive damage to the
equipment and can pose a very dangerous hazard for
workers who are exposed to it," explained Randall
Sagan, an electrical engineer who is responsible for
designing the power system for the 8.5-million-sq.-ft.
Mercedes-Benz U.S. International Inc. (MBUSI) facility
in Vance, AL. "The faster a breaker can trip to turn off
power and extinguish the arc, the less energy is emitted
and, therefore, the risk from injury is reduced."
The risk of an arc-flash event is one of the reasons
power-system maintenance is the single most
dangerous activity technicians perform in a year's time
at this facility. "The maintenance teams don't normally
work on the power system very often," Sagan said.
"When you consider utility substation crews working
on substation equipment every day-they are very
good at it because they practice the same types of
activities over and over. Our maintenance teams may
be working on chillers, air compressors, pumps, or air
filters most of the time. And then once a year, they go
do power-system maintenance. Now they need to open
and close breakers, rack breakers out of their cubicles,
and put safety grounds on the cables. This is not
something they do every day. The danger is real and
these guys understand the risks involved."

Historic Alabama plant
Mercedes-Benz is a global automobile manufacturer-
a division of the German company Daimler AG,
headquartered in Stuttgart, Baden-W├╝rttemberg. The
brand is known for its luxury vehicles, buses, coaches,
and trucks.
In 1994, the company broke ground in Vance, AL, to
build its only North American manufacturing facility.
The company chose the 1,000-acre spot between
Tuscaloosa and Birmingham because of its proximity
to the interstate, a railroad, and utilities. Alabama
Power worked as a partner and built an on-site substation to provide power only to this Mercedes-Benz
plant, which produces more than 300,000 vehicles
annually. The facility manufactures models GLS, GLE,
GLE coupe, and some C-class sedans.
The company hired Sagan for his experience
designing power systems at Kentucky Utilities and the
Georgetown, KY, Toyota Motor Manufacturing facility.
"When I got here [MBUSI], this was just a big muddy
field, and the power system was a blank sheet of white
paper," he recalled. "You talk about an engineer's dream
come true!"
JULY 2017

A need for redundancy
For Sagan, the main focus for the original powersystem design was redundancy. "I knew that this would
give us more flexibility for performing maintenance, as
well as providing a more-reliable system in the event of
a failure," he said.
Sagan explained that mechanical systems typically
use "N+1" redundancy. "If you need three pumps, then
you install four. That way if one of the pumps fails, you
turn on the backup," he said. But for a power-distribution system to be fully backed up, "2N" redundancy is
required. This means every major piece of equipment
has a backup installed-one-for-one.
"Alabama Power fed the plant with two substation
transformers," Sagan said. "We essentially designed
two complete power-distribution systems in the plant.
Each one is a mirror image of the other and is fed from
each of the Alabama Power transformers. This 2N
redundancy approach was carried all the way down to
the 480-volt bus duct distribution systems in each of
the shops."
Tie breakers at the main switchgear and at each
unit substation provide the ability to back feed a
section if something fails or needs to be shut down for
maintenance.

Massive power, reliability, safety
A recent plant expansion to accommodate an increase
in production capacity created a need for increased
power. The original power system Sagan designed has
operated efficiently and effectively for the past 23 years,
but the increased load was going to exceed the capacity
of the main "M1" switchgear and require a new lineup
of medium-voltage switchgear, "M2." Sagan used this
opportunity to implement a safer and more reliable
protection and control scheme.
"The original concept was to copy what we had on
M1 and make M2 match," explained Sagan. "I met
with relay manufacturers and asked them to show
me what features were available in this day and age.
There was some pretty impressive stuff, but it seemed
like everything was focused more on reliability. I was
more interested in improving safety. While reliability
is certainly important, a lot of the protection schemes
they were showing me were way more complicated
than what I thought I needed for a car plant."
During an internal presentation, a sales engineer
mentioned how faster circuit-breaker tripping times
improved power-system reliability. That caught Sagan's
attention, and he asked about the impact on arc-flash
mitigation. From that point forward, the discussion
focused on a protection scheme that emphasized safety.
"Of the hundred or so different options available,
I picked out the six or seven that made sense for this
MAINTENANCETECHNOLOGY.COM | 11


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Table of Contents for the Digital Edition of Maintenance Technology July 2017

Editorial
Uptime
On The Floor
Powering Auto Production
Following The North Star
Flying Inspections
Untangle Compressed Air Misconceptions
Change Your Lubrication Mindset
HMI-Design Essentials For Today's SCADA Systems
SAP: Tips and Tricks
Cybersecurity Best Practices
Bearing Storage
Interpreting IP Code
Noisy Pumps
Move From Time- to Condition-Based Lubrication
CMMS Energizes Maintenance Efforts
Products
Ad Index
Showcase
Final Thought
Maintenance Technology July 2017 - 1
Maintenance Technology July 2017 - Cover1
Maintenance Technology July 2017 - Cover2
Maintenance Technology July 2017 - 1
Maintenance Technology July 2017 - 2
Maintenance Technology July 2017 - 3
Maintenance Technology July 2017 - Editorial
Maintenance Technology July 2017 - 5
Maintenance Technology July 2017 - Uptime
Maintenance Technology July 2017 - 7
Maintenance Technology July 2017 - On The Floor
Maintenance Technology July 2017 - 9
Maintenance Technology July 2017 - Powering Auto Production
Maintenance Technology July 2017 - 11
Maintenance Technology July 2017 - 12
Maintenance Technology July 2017 - 13
Maintenance Technology July 2017 - 14
Maintenance Technology July 2017 - Following The North Star
Maintenance Technology July 2017 - 16
Maintenance Technology July 2017 - 17
Maintenance Technology July 2017 - Flying Inspections
Maintenance Technology July 2017 - 19
Maintenance Technology July 2017 - 20
Maintenance Technology July 2017 - 21
Maintenance Technology July 2017 - Untangle Compressed Air Misconceptions
Maintenance Technology July 2017 - 23
Maintenance Technology July 2017 - 24
Maintenance Technology July 2017 - Change Your Lubrication Mindset
Maintenance Technology July 2017 - 26
Maintenance Technology July 2017 - HMI-Design Essentials For Today's SCADA Systems
Maintenance Technology July 2017 - 28
Maintenance Technology July 2017 - 29
Maintenance Technology July 2017 - SAP: Tips and Tricks
Maintenance Technology July 2017 - Cybersecurity Best Practices
Maintenance Technology July 2017 - Bearing Storage
Maintenance Technology July 2017 - Interpreting IP Code
Maintenance Technology July 2017 - Noisy Pumps
Maintenance Technology July 2017 - Move From Time- to Condition-Based Lubrication
Maintenance Technology July 2017 - 36
Maintenance Technology July 2017 - 37
Maintenance Technology July 2017 - 38
Maintenance Technology July 2017 - CMMS Energizes Maintenance Efforts
Maintenance Technology July 2017 - 40
Maintenance Technology July 2017 - 41
Maintenance Technology July 2017 - Products
Maintenance Technology July 2017 - 43
Maintenance Technology July 2017 - 44
Maintenance Technology July 2017 - 45
Maintenance Technology July 2017 - Ad Index
Maintenance Technology July 2017 - Showcase
Maintenance Technology July 2017 - Final Thought
Maintenance Technology July 2017 - Cover3
Maintenance Technology July 2017 - Cover4
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