A partial discharge test was carried out on Generator Transformer 1 at an NTPC power plant from May 6-7, 2014 by experts from Logic ++ India Pvt Ltd. The test found partial discharge at four locations on the transformer ranging from 20-30 microvolts. Based on the partial discharge measurements and dissolved gas analysis results, Logic ++ opined that the partial discharge activity was not alarming in nature and would not affect transformer operation. They recommended keeping the transformer in service with continued monitoring and retesting in two months.

1. Record Notes of Partial Discharge Test Carried out by MIS Logic ++ Naida
Date:07.05.2014
Mis. NTPC LTD Mis. LOGIC PLUS PLUS INDIA PVT. LTD.
Shri B.Maharana, AGM (EM) I/C Shri.Sunil Kumar Bhami (Manager)
Shri.K. Ravinder, AGM (EM)
Shri.Ch.Venkateswara Rao, DGM (EM)
Shri.M.V. Reddy, Manager (EM)
1. Generator Transformer-1 has developed H2 gas In DGA. the level of H2 has gone up to
293PPM.
2. The DGA report indicates different gas levels as below:
H2-293ppm,N2-1.11%, 02-0.2%, CH4-14ppm, C2H4-1ppm, C2 H6-1ppm, C2H2-0ppm, CO-88ppm,
C02-1009ppm & TGC-1.45% (DGA Trend chart attached)
Seeing the critica lity of H2 level in DGA which may be because of P.D, P.D has been planned to
identify the location of P.O.
-I:
3. Mis Logic ++ Naida, who are t he exper.s in this field oft P.D analysis has been contacted for
carring out the test . Mr. Sunil Kumar Bhami, Manager of Mis Logic plus Plus visited to Mis NTPC Ltd
from 06.05.2014 to 07.05.2014 for measurement of Partial Discharge in Generator Transformer#l.
4. Partial Discharge measurement was carried out with the help of TP SOOA Power PO Test
Equipment by using AE Sensors & HFCT Sensor. AE Sensors were mounted at various locations to
find out the location of PO inside the transformers & HFCT was clamped at the grounding of the
transformers & data acquired for analysis.
5. The Partial Discharge observations of GT#l are as follows.
A. Side-1 (HV side) R-ph near to lead connection with P.D amplitude-20Il volts.
B. Side -2 west side of transformer P.D amplitude-30Il volts.
e. Side-3 (LV side) R-ph LV connection area P.D amplitude-251l volts.
D. Side-4 Radiator sideof the transformer P.D amplitude-20Il volts.
E. No P.D observed in other locations of the transformer.
Based on t he above PO test & the DGA results, Mis Logic ++ Pvt Ltd opined that the PO activities
observed in GT-1 is not of alarming nature & it will not affect the operation of the transformer.
Hence the transformer may remain in service with further monitoring. Mis logic ++ Pvt Ltd
recommended for re testing of PO test after 2 months.
6. Testing of the transformers is completed on 07th May, 2014.
7. The detailed report shall be submitted by 20.05.14.
NTPC LOGIC PLUS PLUS INDIA PVT. LTD.