Section R 4. Installation - GE PVDB-28kV Instructions Manual

Section 4. Installation
adequate protection. A poor ground may be worse than
no grolmd at all, since it gives a false feeling of safety to
those working around the equipment and may result in
lutimate loss of life or damage to the apparatus.
General
The installation of the breaker will be facilitated by a
sllidy of these instnlctions and a review of the approved
drawings which supplement these instnlctions. The
drawings show the general arrangement, dimensions
(Fig. 8), location of foundation bolts, provisions for
conduit connections, electrical connections and other
information necessary for the proper installation of the
breaker. These drawings consist of the requisition sum-
mary, outline of the Imit with its operating mechanism
and housing, and the connection diagrams.
4-4 Control and Secondary Wiring
The breaker is shipEed in the closed Eosition.
4-1 Location and Mounting
The tmit shotud be located so that it is readily accessible
for manual operation and inspection. Care should be
taken when lifting the tmit not to allow the lifting device
to come in 'contact with the bushing. Two lifting holes
are ~rovided on the to~ of the unit for lifting ~uwoses.
The total weight of the tmit is given on the nameplate
and should be taken into consideration when selecting a
lifting device for the breaker.
Concrol and bushing clUTent cransformer connections
are made inside the operating mechanism hOllsing
where suitable terminal boards are provided. Con-
nection diagrams are supplied for each unit showing the
proper connections for the operating mechanism and
the bushing current transfmmers. All bushing cun-ent
cransformer terminal boards are shipped shorted and
grolmded. These connections sholud be changed upon
selecting the bushing ClU"I"ent transformer ratio.
Legs for the basic tmit as indicated on the outline
drawing come in 12 inch to 36 inch lengths and are
shipped separately, ready for assembly. Mter assembly,
fasten the breaker in position on its foundation. The
fotmdation should be firm and level; if it is not, shims
sholud be used tInder the motmting pad of the leg to
level the unit. The motmting bolts recommended are
0.625 inch diameter minimum (0.75 inch diameter bolt
can also be used) and their locations are shown on the
breaker outline drawings.
4-5 Primary Connections
Leads should be bought down from above if possible.
Ample electrical clearance must be provided between
these leads and parts of the station, such as wall,
channels and framework. Leads sholud be properly
supported so that the breaker bushings are not subjected
to unnecessary strains. The bushings sholud not carry
cable or bus bar strains. To avoid overheating, the
connecting leads must be of a current-<:arrying capacity
at least equal to the maximum operating current of the
circuit which sholud not exceed the breaker rating.
4-2 Connections
Mt~r the breaker has been located, electrical
connections can be made. Before making these, every
precaution must be taken to see that all leads to be
connected to the tmit are dead.
Connections to the breaker are made by the bolted
connectors fastened to the ends of the bushings and
must be securely tightened to assure good contact. All
joints must be clean and bright.
4-3 Ground Connections
The framework of each breaker should be permanently
grounded. The usual practice is to connect a heavy
cable to the framework and to the grolmd. Provisions
for a bolted connector is provided on the framework to
which the grolmd cable can be attached.
4-6 Inspection Before Operation
After the unit has been installed with all mechanical and
electrical connections completed, the following in-
spections and test sholud be made before operation. If
any question arises concerning the lmit during the
following inspection procedure, refer to Section 6,
Measurements and Adjustments.
The cable sholud be able to carry 25 per cent of the
current rating of the breaker, but should not be smaller
than MIO.
A good permanent low resistance ground is essential for
All control wires should be run in conduit insofar as it is
practicable. Control wires must be rtm separately and
remote from high tension leads tmless the distance
separating the two sets of wires is sufficient to prevent
possible commtmication between them as a restut of
short circuits' Control wiring of adequate size should be
used so that with nul operating current flowing to the
operating mechanism, the voltage across the terminals
of the mechanism will be within the limits specified as
standard for the control voltage as specified on the
nameplate. It is recommended that all conduits
entering the mechanism housing be sealed off at their
entrances to the housing.