Howard Medium Power Substation - Manual (Page 14)

Document 2.4.06, Revision 4
June 2013 Medium Power Substation Transformers
14
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 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 new fluid should be 30 kv or greater when
tested in accordance with ASTM D877.
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 is 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. Measure
the winding resistance of each winding and
compare results to factory test values. An
increase of more than 10% could indicate a
loose internal connection.
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 to should be made with care to
avoid placing undue stress on the bushings.
Refer to bushing connection information on
Pages 12 and 13.
7. Tap Changer Setting. Check the tap changer
setting to ensure it is set to the proper position
for the required voltage.