Howard Small Power - Manual (Page 9)

Small Power Substation Transformers
Document 2.4.54 Revision 0
July 2006
9
Installation of Surge Arresters
Surge arresters should be installed according to the
following instructions and the outline drawing.
!
WARNING: FAILURE TO FOLLOW THESE
INSTRUCTIONS COULD RESULT IN SEVERE
PERSONAL INJURY, DEATH, OR EQUIPMENT
DAMAGE.
1. Carefully unpack and inspect surge arresters
for damage.
2. When installing arresters, all mounting feet
must be flush with the mounting surface before
tightening bolts. Use shims if necessary.
3. Do not climb or stand on arrester. Do not place
undue mechanical stress on arrester.
4. Use only the lifting devices provided on the
arrester for lifting.
5. Arrester exhaust ports (if supplied) must be
oriented so that exhaust will be directed away
from other arresters and other equipment.
Installation of Air Terminal Chamber and
15 KV and 5 KV Switchgear Adapters
Air terminal chambers are designed to protect
personnel from high voltages and to provide a clean,
dry environment for bushings. Air terminal chambers
must be installed according to instructions on the
drawing. Refer to transformer outline drawing, detail
drawing, and station plan drawing.
!
WARNING: IMPROPER INSTALLATION OF
CONNECTING CHAMBERS AND ADAPTERS
MAY ALLOW WATER OR OTHER CONTAMINANTS
TO CONTACT LIVE PARTS, POSSIBLY RESULTING IN
SEVERE PERSONAL INJURY, DEATH, OR PROPERTY
DAMAGE.
Securely attach the flexible connectors supplied by
the switchgear manufacturer to the switchgear bus
bars. The number of flexible connectors supplied
is determined by the transformer current and not
by the current rating of the bus bar. Check the
length of flexible connectors and ensure that there
is approximately 0.375 inch (10 mm) of slack. This
will permit some movement of the bus bars to allow
for expansion and contraction and possible settling
of the transformer. Securely attach the ground bus
connection between the transformer and switchgear.
Before reinstalling the adapter housing, check for
adequate electrical clearances as indicated on the
outline drawing and check tightness of connections and
supports. Complete the installation by assembling the
housing. Install the adjustable plate and ensure proper
gasket sealing of the switchgear throat.
Pre-energization Tests and Checklist
The following tests and checks should be performed at
a minimum to ensure that the transformer is ready to
be energized. Do not energize the transformer without
performing these tests and checks.
1. Insulating Fluid Test. Draw a fluid sample and
test its dielectric strength. Dielectric strength
of the new fluid should be 26 kV or greater.
2. Pressure Test. Check the transformer tank for
leaks by pressurizing the tank with dry air or
dry nitrogen through the pressure test fitting
to a pressure of 3 to 4 PSIG. Let the tank
stand under pressure for one to two hours,
then examine the tank and fittings for leaks.
Leaks above the fluid level can be detected
by applying soap solution to all welds, joints,
pipe fittings, and cable connections. Upon
completion of this test, reduce the internal
pressure to 1 or 2 PSIG.
3. Insulation Megger Test. Perform a 1000-Volt
Megger test and a power factor test to ensure
that none of the windings are grounded.
4. Ratio Test. Perform a ratio test at each tap
position to ensure that transformer coil ratios
and tap changer connections are correct.
5. Continuity Test and Resistance Test. Perform a
continuity check on each winding.
6. Line Connections. In preparation for making
line 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.
Connections should be made with care to avoid
placing undue stress on the bushings.
7. Tap Changer Setting. Check the tap changer
setting to ensure it is set to the proper position
for the required voltage.