instruction manual - BHEL Bhopal

2.4.2 SUPPLY AND TESTING
The transformer oil is despatched directly to site from oil refinery. The
oil is thoroughly inspected and tested at oil supplier's works in presence of
BHEL and/or customer's representative or their authorised representatives.
Test certificate giving values obtained for all characteristics is issued.
2.4.3 HANDLING
The oil drums should be carefully handled at site, details of which are
given in Clause 9.1of IS:1866.
2.4.4 RECONDITIONING
Transformer oil is usually contaminated during handling, transport and
storage due to ingress of moisture and solid impurities. Hence, oil shall be
vacuum filtered separately at 50 0 C to 60 °C using a suitable filtration machine
and a spare clean tank before filling in the transformer. Details of filtration are
given in Clause 9.2 of IS:1866. Oil treatment shall be terminated when the
following parameters are attained.
TABLE 2.1
kV Class of transformer Recommended Permissible limit
Electric Strength Moisture Content
(BDV) in kV (Min) ppm (Max)
Upto 145 60 20
245 65 15
420 70 15
Storage tank shall be as per typical arrangement shown in Fig 2.2
Electric strength and moisture content shall be determined following
the test procedure of IS: 335.
2.5 OIL FILLING UNDER VACUUM
2.5.1 APPLICATION
Transformers and Reactors with vacuum-proof tanks shall be filled with
oil according to this method.
2.5.2 STORING TIME
Generally it applies that Transformers and reactors which during transport
are filled with dry nitrogen on arrival at the site shall be evacuated and oil
filled. Before storing, the equipment shall be inspected according to the
directions given in Clause 2.1 "Reception and assembling of transformer/reactor
despatched partly dissembled and filled with nitrogen". During the storing
time, overpressure shall be maintained, and nitrogen consumption checked
according Clause 2.2.
Prepared By Samvet Lahari, Bhopal. Phone- 5277412