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INSTRUCTION
MANUAL #105
THREE PHASE POLE MOUNTED DISTRIBUTION TRANSFORMER
ERMCO | 2225 Industrial Road | Dyersburg, TN 38024 | (800)238‐5587
INTRODUCTION
This instrucon manual provides general informaon for the
installaon, operaon, and maintenance of ERMCO three‐phase, pole
mounted transformers. These transformers are to be applied and used
per the “usual service condions” describes in IEEE C57.12.00 (General
Requirements for Liquid‐Immersed Distribuon, Power and Regulaon
Transformers).
RECEIVING AND INSPECTION
ERMCO pole transformers are shipped filled with insulang
transformer oil. Immediately upon receipt, and before being put in
service, transformers should be inspected for any external damage or
loose parts caused by shipping and handling. Damage presumed to
have occurred during shipment should be noted, and your ERMCO
sales representave contacted.
Extreme care is taken at the factory in the processing and sealing of
the transformer to insure that it is clean and dry, and of adequate
dielectric strength. Normally, therefore, it is not recommended that
the transformer seals be broken for internal inspecon. If it is decided,
nevertheless, that the transformer be opened, adequate precauons
should be taken as outlined elsewhere in these instrucons.
HANDLING AND INSTALLATION
Transformers should be lied by the liing lugs only. The transformer
bushings should not be used for liing or moving the transformer into
posion. The transformer should be kept upright at all mes and not
pped over on its side for any reason. This will prevent air bubbles
from entering the coil which could degrade the dielectric strength.
Support lugs for direct pole mounng are provided in accordance with
IEEE standards. Hangers and kickers for cross arm mounng is to be
provided by the user. When installed, transformers should be
protected from dangerous overloads, over voltages and lightning by
suitable, approved devices.
OIL
Transformers are thoroughly dried at the factory and filled with
ERMCO inhibited mineral oil having a minimum dielectric strength of
30 kV at 60 Hz when tested per ASTM D‐877. ERMCO inhibited mineral
oil contains less than 1 ppm of PCB's at me of manufacture. The
transformer should never be energized unless it is filled with oil.
If it should be found necessary to add to or replace the oil in the
transformer, only clean dry oil having the minimum dielectric strength
of 30 kV and less than 1 ppm PCB's should be used. Before opening
the transformer, sufficient me should be allowed for the transformer
to come to temperature equilibrium with the air in the room to
eliminate the possibility of moisture condensa
on from the air.
A recommended procedure for opening the transformer is to first
bring the interior of the transformer to atmospheric pressure by
venng the automac pressure relief valve furnished on all ERMCO
transformers. The cover may then be removed. Natural rubber hose
should not be used in the transfer of oil. The correct oil level at 25°C is
marked on the inside of the tank.
Care should be taken to re‐seal the transformer so that moisture is
permanently excluded from the interior. A pressure test using dry air
or nitrogen, may conveniently be made through the pressure‐vacuum
fing, aer removing the pressure relief valve, to be sure all seals are
ght. Pressurize the transformer to 5 psig and hold for 30 minutes. A
drop in pressure during this me would indicate the transformer is not
properly sealed and the tank and fings should be checked and the
leak repaired. Finally, the pressure relief valve should be installed and
carefully ghtened.
CONNECTIONS
Refer to the transformer nameplate for the kVA rang and the
permissible connecons. No connecons other than those shown on
the nameplate should be made; and none of the connecons should
be changed while voltage is applied to the transformer. Provision is
made for grounding the tank by means of a tapped pad or ground
connector.
OVERLOAD AND OVERVOLTAGE PROTECTION
Transformer protecon against overloads and over voltages may be
obtained by suitable devices applied in the field to convenonal
transformers, or by use of protected transformers (ERMCO CSP or CP
types) as supplied from the factory.
1. Fuses: High voltage fused cutouts are recommended for
protecon of convenonal transformers against overloads and to
protect the line against outages. On ERMCO CSP and CP
transformers, a fusible protecve link, mounted inside the tank,
is provided in series with each HV terminal. In case of internal
failure of the transformer, the protecve link disconnects the
transformer from the line without affecng line fuses or breakers.
When the available fault current exceeds the maximum
interrupng rang of the protecve link, a current liming fuse
should be used in series with the protecve link.
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