Howard Medium Power Substation - Manual (Page 20)

Document 2.4.06, Revision 4
June 2013 Medium Power Substation Transformers
DANgER : THE TRANSFORMER MUST BE
DE-ENERGIZED BEFORE BEGINNING ANY
MAINTENANCE WORK. FAIlURE TO DO SO COUlD
RESUlT IN SEvERE PERSONAl INJURY, DEATH, OR
PROPERTY DAMAGE.
It is the responsibility of the owner to inspect, maintain,
and keep the transformer in proper operating condition.
Report all failures during the warranty period to the
Howard Substation Transformer Division. All warranty
repairs must be made or approved by the Howard
Substation Transformer Division.
WARNINg : TANK lEAKS MUST BE REPAIRED
IMMEDIATElY UPON DISCOvERY. FAIlURE TO
DO SO COUlD RESUlT IN SEvERE PERSONAl INJURY,
DEATH, OR PROPERTY DAMAGE.
Periodic Tests and Inspections
The following periodic tests and inspections are
recommended for routine maintenance of the
transformer.
1. Gauge readings (one month after initial
energization and annually thereafter). Gauge
readings, ambient temperature, and kvA
load should be measured and recorded. Any
abnormal reading suggests that further
diagnostic testing or inspection should be
done. If pressure/vacuum gauge and/or
fluid level gauge readings suggest a possible
tank leak, perform a pressure test according
to instructions found on Page 14 (Pre-
energization Tests and Checklist). Tank leaks
must be repaired immediately to prevent serious
damage to the transformer and danger to life.
2. Cooling fans (annual). Check the cooling fans
(if any) by setting the fan “auto/manual” control
switch to the “manual” position. The fans
should rotate at full speed within approximately
five seconds. The fans should rotate smoothly
with minimal vibration.
3. Control wiring (annual). Control wiring should be
checked to insure that wire insulation is in good
condition. The control cabinet and associated
conduit should be inspected to ensure that
weather seals are intact. Control power supply
voltage should be checked and compared to the
voltage stated on the wiring diagram.
4. Paint finish (annual). Inspect the paint finish for
damage or weathering that exposes the primer
coat or bare metal. Repair any paint damage
that might be found.
5. Fluid dielectric test (annual). Sample the
insulating fluid as described below. The
dielectric strength of the insulating fluid should
measure at least 26 kv.
6. Bushing and surge arrester insulators (annual).
Bushing and surge arrester insulators should be
clean. If the surfaces are excessively dirty, they
should be cleaned while the transformer is not
energized.
7. Bushing terminals (one month after initial
energization and annually thereafter). If the
transformer is energized and under load,
measure bushing terminal temperatures
using an infrared scanner. Excessive bushing
terminal temperature indicates a loose or dirty
connection. If the transformer is not energized,
use a torque measuring device to make sure
terminal connections are tight.
Sampling of Insulating Fluid
Transformers are filled with insulating fluid, which
provides electrical insulation within the transformer
tank and transfers heat generated in the coils to the
tank wall and radiators. The fluid is either conventional
transformer oil (mineral oil), Envirotemp ® FR3 fluid, or
silicone fluid.
Periodically check the transformer for proper fluid level
by reading the fluid level gauge. Add fluid if necessary.
When adding fluid, add only the same type fluid that is in
the transformer.
It is also recommended that a fluid sample be drawn
annually and tested for dielectric strength. Samples
should be drawn from the bottom of the tank. Use
proper sampling procedures to prevent erroneous test
results. Dielectric strength should measure 26 kv
minimum.
MAINTENANCE
20