2
THREE PHASE POLE MOUNTED DISTRIBUTION TRANSFORMER
INSTRUCTION
MANUAL #105
2.
Lightning Arresters:
Conven onal transformers should be
protected by properly rated lightning arresters. Ground
connec ons on the arresters should be made before connec on
to the high voltage line is made.
CSP transformers are lightning protected by gapped or direct
connected lightning arresters bolted to moun ng pads welded to
the tank wall. Gapped arresters have an adjustable electrode on
the top terminal of the arrester to obtain the proper gap se ng
to the bushing electrode.
Before the transformer is put into service, the gap type arrester
electrode should be checked for proper gap alignment and
spacing. Adjustments should be made as necessary.
3.
Secondary Breakers:
ERMCO CSP and CP transformers are
protected against secondary overloads and short circuits by an
internally mounted circuit breaker. The func on of the breaker is
to open the low voltage circuit and protect the transformer from
faults or severe overloads.
The breaker opera ng mechanism is designed to be operated by
a lineman's hot s ck. Transformers are shipped with the circuit
breakers closed.
To open the low voltage manually, move the handle fully
counterclockwise so that the pointer moves from the "C" (closed)
to "O" (open), at which point the circuit is open. Verify that the
circuit breaker is latched in the "open" posi on. To ensure the
discharge of the sta c charge which is some mes present in the
low voltage winding due to capacitance, it is recommended that
the low voltage be grounded a er opening the circuit breaker
un l a er the high voltage is disconnected.
To close the breaker, rotate the handle fully counterclockwise to
"R" (reset), which engages the latch mechanism, and then
clockwise to "C" (closed). If a fault exists or an excessive load
exists at the me the breaker is closed, the breaker will reopen
even though the handle is held in the "C" (closed) posi on.
Some breakers are provided with a red signal light which gives
warning that the load has reached a value near the tripping point
of the breaker. The signal light remains lighted un l reset (turned
o
ff
) by means of the breaker opera ng handle. Transformers
should not be operated under load condi ons that will cause the
red light to appear frequently, since it indicates an overload on
the transformer. When such a condi on exists, it is
recommended that a larger transformer be subs tuted to avoid
impairing the life of the smaller unit.
To reset the signal light without disconnec ng the load, rotate
the handle to "L" (light), and then return to "C" (closed). If the
light fails to go out, the transformer is s ll overheated. To check
the signal light bulb when the transformer is in service, rotate the
handle to "L" (light). The light should turn on. If it does not, the
bulb should be replaced.
Some circuit breakers are equipped with an emergency overload
device which can be used to restore service following a circuit
breaker opera on due to overload. The emergency overload
lever is located immediately above the breaker opera ng handle.
With the emergency lever in the normal posi on, the breaker will
trip at its normal se ng as calibrated at the factory. Moving the
lever in a clockwise direc on increases the se ng so a higher
temperature is required to trip the breaker. The emergency
se ng may be adjusted to an intermediate or extreme value.
This emergency se ng provides extra load capacity and s ll
permits manual breaker opera on, and also retains short circuit
protec on of the transformer. It is important that the emergency
se ng be used only when, and as long as, absolutely necessary
because its use will result in a reduc on of transformer life.
A meter seal is provided on the emergency lever to prevent
tampering. It is recommended that a new seal be applied to the
lever when it is returned to the normal posi on a er emergency
opera on.
The breaker is a thermal and short circuit protec ve device for
the transformer. It is not recommended that the breaker be used
for rou ne disconnect opera ons.
GASKETS
Cover and bushing gaskets are all made of Buna
‐
N Nitrile rubber.
Gaskets may be reused if not damaged. Round covers must seat
evenly on the gaskets so that pressure is distributed evenly. The cover
must be ghtened
fi
rmly to insure an e
ff
ec ve seal.
DUAL VOLTAGE AND TAPS
ERMCO transformers rated for more than one primary voltage are
equipped with a dual voltage switch or tap changer.
These switches
are externally operated, but should never be operated while the
transformer is energized. When switching from one voltage to
another, make sure the switch is in the proper posi on before re
‐
energizing the transformer. A er turning the switch, ghten the
locking device to minimize the possibility of uninten onal
movement.
STORAGE
Transformers should be stored
fi
lled with oil and in a clean dry place,
if possible where there will be no extreme temperature changes.
Before the transformer is put in service, it should be checked in the
same manner as when received.
ERMCO | 2225 Industrial Road | Dyersburg, TN 38024 | (800)238
‐
5587
