
SEBU8219-01 39
Product Information Section
Product Identification Information
12 Lead
g00669312
Illustration 38
12 L ead Delta Configuration
Terminals T6 and T9 become the neutral connection when the
terminals are tied together and grounded. This reflects the terminal
T2 and T10 connection as the high phase.
Grounding the Frame
In any generator set installation, the frame of the
generator must be positively connected to an earth
ground or to the hull of a vessel. This connection is
the first connection that is made at the installation.
This connection is the last connection that should be
removed. If the generator set is on flexible pads or on
resilient pads, the ground connection must be flexible
in order to avoid possible breakage in later operation.
Ground connection cable or ground connection straps
should have at least the current carrying capacity of
the largest line lead to the connected load. Joints in
cables or in straps must be clean, free of electrical
resistance, and protected from possible oxidation.
Bolted ground connection joints eventually oxidize.
The joints are frequent sources of radio frequency
interference (RFI). Silver soldered joints and bolted
joints are electrically and mechanically sound.
Neutral Connections
The generators with Wye Configuration usually
have the neutral ground when the generator is
installed. However, there are some cases when
definite measures should be taken in order to
prevent grounds on the load side. The purpose of
the grounding of the neutral is to prevent load side
equipment damage.
If the neutral w
ire is grounded and one of the phase
leads becomes grounded, the excessive current will
open a load circuit breaker. The excessive current
will also coll
apse the generator voltage. The result
depends on the following items: particular generator
electrical characteristics, type of fault, and trip rating
of the circui
t breaker. An undervoltage device may be
required in order to provide an adequate short circuit
protection.
There are some instances in which it is undesirable
to ground the neutral wire. In other applications, it is
acceptable
to have an ungrounded generator neutral
lead. Definite measures should be taken in such
applications in order to prevent grounds to the phase
leads. An ex
ample of such measures are ground fault
protective circuits. Ground fault protection requires
that the entire group of distribution circuits should
be studied
. The entire group of distribution circuits
should be treated as a system. The owner should
engage a certified, registered consult ant if a new
distribu
tion system is being developed. The owner
should also engage a certified, registered consultant
if an existing system should be modified for the
ground fa
ult protection.
Single Un
its
In a three-phase, four-wire system, the neutral wire
should be
grounded according to local wiring codes.
In applications in which definite measures are taken
in order t
o prevent grounds to the load leads, an
ungrounded neutral can be used. Be sure to check
your local wiring codes.
Multiple Units
Operation of multiple generators in parallel that have
all neutrals grounded, may result in the circulating
current
through the neutral connections. In order
to eliminate the possibility of circulating currents,
ground the neutral of only one generator. If multiple
genera
tors are alternated on line, a switch should
be installed in the neutral ground circuit of each
generator. In this case, all neutral ground circuits
except
one circuit can be opened. Be sure that one
of the neutral ground circuits is closed.