Powell FlexTrol Class E2, Instruction Bulletin

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01.4IB.46300
Installation
FlexTrol
™
Class E2 Medium Voltage Controllers with
Eaton Contactor
H. g
rounDing
Before power connections can be made, the
switchgear vertical sections must be grounded.
A ground bus is furnished with lugs at each
end for connection to the station grounding
system. It is arranged so that connections to
the station ground can be made in any unit.
Where equipment is shipped in more than one
group, the sections of ground bus must be
connected by using the splice plates furnished
with the equipment (Figure 10).
Assemble the ground bus joints as outlined
under Ch 4 Installation, I. Connections . The
switchgear ground bus must be connected to
the station ground bus by a conductor having
a current carrying capacity equal to that of the
switchgear ground bus. It is very important
that the equipment be adequately grounded
to protect the operator from injury when
short circuits or other abnormal occurrences
take place and to ensure that all parts of the
equipment, other than live parts, are at ground
potential.
It is recommended that the connection to the
station ground have a cross section of 500,000
circular mils (240 mm
2
) or greater if the soil
in which it is buried is of such character as to
cause appreciable corrosion. This is especially
true where electrolysis from stray currents
or contact with dissimilar metals exists. The
resistance of the soil surrounding a station
ground depends on the condition of the soil, as
well as its chemical content. Dry, loose, sandy,
or frozen soils will have a high resistance as
compared with moist soils or soils containing
ashes, cinders, or salt solution.
The IEEE Standard 142 states that grounding
impedance in the range of 1 to 5 ohms is
generally acceptable for industrial substations.
Ground resistance testing is recommended to
verify that the ground resistance falls within
this range.
Figure 16 shows the grounding connection
for the 400A controller equipment. Figure 17
shows the grounding connection for the 800A
controller.
Table C General Guideline for Outgoing Feeder
Cables
Construction
Type
Continuous
Current
(Amperes)
Maximum
Cable Size
Cable
per
Phase
One-High
Vertical
Section
360 500 mcm 1
Two-High
Vertical
Section
360 500 mcm 1
One-High
Vertical
Section
720 500 mcm 2
i . c
onnections
The main bus bars and other connection bars
are copper. The connection surfaces are silver
surfaced or equivalent. The silver plating used
on bolted contact surfaces is approximately
0.0001" thick. All field assembled joints in
primary conductors, regardless of method of
insulation, should be made as follows:
1. Wipe the surface clean with a lint-free cloth.
Do not use sandpaper or any abrasive
on the plated surface. Avoid handling of
cleaned surface as much as possible. If
the surface is tarnished, clean it with silver
polish and then wash it with denatured
alcohol.