Howard Small Power - Manual (Page 15)

Small Power Substation Transformers
Document 2.4.54 Revision 0
July 2006
15
!
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 issues 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 transformer maintenance.
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 9 (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’s “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