1
INSTRUCTION
MANUAL #105
THREE PHASE POLE MOUNTED DISTRIBUTION TRANSFORMER
ERMCO | 2225 Industrial Road | Dyersburg, TN 38024 | (800)238
‐
5587
INTRODUCTION
This instruc on manual provides general informa on for the
installa on, opera on, and maintenance of ERMCO three
‐
phase, pole
mounted transformers. These transformers are to be applied and used
per the “usual service condi ons” describes in IEEE C57.12.00 (General
Requirements for Liquid
‐
Immersed Distribu on, Power and Regula on
Transformers).
RECEIVING AND INSPECTION
ERMCO pole transformers are shipped
fi
lled with insula ng
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 representa ve 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 inspec on. If it is decided,
nevertheless, that the transformer be opened, adequate precau ons
should be taken as outlined elsewhere in these instruc ons.
HANDLING AND INSTALLATION
Transformers should be li ed by the li ing lugs only. The transformer
bushings should not be used for li ing or moving the transformer into
posi on. 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 moun ng are provided in accordance with
IEEE standards. Hangers and kickers for cross arm moun ng 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
fi
lled 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
fi
lled 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, su
ffi
cient 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
fi
rst
bring the interior of the transformer to atmospheric pressure by
ven ng the automa c 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
fi
ng, a er 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
fi
ngs 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 ra ng and the
permissible connec ons. No connec ons other than those shown on
the nameplate should be made; and none of the connec ons 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 protec on against overloads and over voltages may be
obtained by suitable devices applied in the
fi
eld to conven onal
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
protec on of conven onal transformers against overloads and to
protect the line against outages. On ERMCO CSP and CP
transformers, a fusible protec ve link, mounted inside the tank,
is provided in series with each HV terminal. In case of internal
failure of the transformer, the protec ve link disconnects the
transformer from the line without a
ff
ec ng line fuses or breakers.
When the available fault current exceeds the maximum
interrup ng ra ng of the protec ve link, a current limi ng fuse
should be used in series with the protec ve link.
