Howard HI-110 Network Transformer - Manual (Page 10)

Document 2.4.128, Revision 2
August, 2012
10
Network Transformer Instruction Manual
depend on the transformer kVA, efficiency and
load cycle. Forced ventilation may be required
to adequately cool the transformer. Refer to the
National Electric Code for recommended vault
ventilation.
Before placing the transformer in service, remove
any shipping braces and packing material that may
have been attached at the factory.
Grounding
The transformer must be permanently grounded
according to applicable local and national codes.
Ground the transformer by using the grounding
provisions located on the exterior surface of the main
tank. Do not use hold-down bolts, pipe connections
or any other fittings for ground connections. A proper
low-resistance ground is critical for safe operation.
Transformers with a grounded-wye primary winding
and a wye secondary winding are designed for
electric distribution systems that have a grounded
neutral. All windings designed for grounded neutral
operation must be permanently and solidly grounded
to the system neutral.
WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR
SERIOUS PERSONAL INJURY AND MAY ALSO
RESULT IN DAMAGE TO THE EQUIPMENT.
The transformer must be properly grounded
at all times.
Primary and Secondary Connections
Before making primary and secondary connections,
check to make sure that all mating connector
surfaces are clean and smooth. Connections must
be tightened appropriately to prevent overheating
and possible subsequent failure of the connection.
Refer to Table 5 for torque recommendations.
Connections should be made with care to avoid
placing undue stress on the bushings.
Primary Connections
Network transformers are supplied with a high-
voltage entrance as specified by the user, usually
consisting of dead-front bushings or wiping sleeves
for connection to the high-voltage source. Dead-
front bushings may be one-piece (integral) bushings
or universal wells with or without factory-installed
inserts. One-piece (integral) bushings and bushing
inserts are designed to interface with insulated
elbow connectors, and can be supplied for either
load-break or non load-break operation.
When transformers are supplied with bushing
wells only, inserts must be installed in the field
before cable connections can be made. Bushing
well inserts must be compatible with the universal
bushing well. Do not use incompatible or improperly
rated inserts, or equipment damage might occur.
When installing bushings or cable accessories,
follow the installation instructions provided by the
equipment manufacturer.
Secondary Connections
Network transformers are normally supplied with
provisions for connection to a network protector.
These provisions consist of three externally-
replaceable bushings bolted to the main tank within
the secondary throat, three flexible connectors for
electrical connection to the network protector, and
a secondary neutral pad welded to the main tank.
When a fully-insulated neutral bushing is provided, it
must be effectively grounded to the system neutral
for proper operation.
SECTION 4: INSPECTION AND TESTING