5. Transformers Rated (kVA) Power Loss/Hour
(KWH) to
Energize the
Transformer
Power
Loss/Month
(KWH) to
Energize the
Transformer
T1 1000 11 7920
T2 1000 11 7920
POWER LOSS
6. OBSERVATION
There is a usage of VFD in different shades, because of that harmonics occur
in the system which creates a line losses in a network and also increases
Core loss in a transformer.
Harmonic analysis shows that the
current harmonics in the system are
lies between 10% to 20% which is so
high, because these harmonic are not
in permissible limit as documented by
IEEE-519-1992 standard.
9. CONSEQU
ENCES
• Due to the under-load
condition of transformer,
the transformer windings
dissipates heat and
creates a Copper Losses in
itself.
• As we conclude that the
electrical energy is
converted into heat
energy of the transformer,
so this energy is loss in
the form of dissipation of
heat.
10. Critical
Observation
Transformers Rated (kVA) Maximum Operating
Level (kVA) in a day
Percentage (%)
T1 1000 240 30.312%
T2 1000 163.5 20.59%
This was found that transformers are
operating at highly under-loaded
conditions. A transformer gives maximum
efficiency when iron losses equal to the
copper losses. This is critical, lower
loading in a transformer result in poor
efficiency.
Furthermore, theses losses are not
accountable in LT panels meter and only
recorded in KE-meter, which results in
energy unit difference among the three
meters. This is also worthwhile to mention
that harmonics in a current also results
in increase copper and core losses of the
transformer (as discussed earlier), but
these losses are also accountable in KE
meter only which is also resulting in unit
difference. Loading condition of
11. Recommenda
tions
1) Transformer is operating
at under-load conditions; this
is resulting in higher core
losses and also copper losses.
This is desirable to increase
the load on one transformer
and second transformer can
be shut down (till more load
is added). The solution of this
recommendation can be
seen. This arrangement will
also provide the flexibility to
control sixteen different
feeders in case of a fault in
any one of the transformers.
12. 2) It is suggested that CT analysis of three CTs can be carried out. For instance CT
connected with KE meter and CTs connected with two LT panels (LT panel 1 and 2).
The error in three CTs must be equal, different errors may result in different energy
meter recording. Due to unavailability and permission from KE we were not able to
see the CT connected with the KE line.
3) It is seen that the current harmonics in the system are so high, this is causing
additional losses in the system. Higher frequency harmonics in current can cause
additional core losses which results in excessive heating. There are two types of
harmonic filter Active & Passive Harmonic Filter which were needs to be installed
on all VFDs to minimize the harmonics in a system.
4) Due to under-loading of transformer from very long time, the transformer
health can be deteriorated which can be checked by performing certain test on
transformer.
a) Winding Resistance Test
b) Turns Ratio Test
c) Insulation Resistance Test
d) Dielectric Test of Transformer Oil
