Predictive Maintenanc

Off line:	Dissolved Gas Analysis (DGA) Electrical Faults - Arcing - Sparking - Corona - Partial discharge Thermal Faults - Over heating - Hot Spot - Hot Metal
Trending & Monitoring of key parameter DGA & oil analysis
On Line	Evolved Hydrogen (Key fault Gas) monitoring by Sensofast™
- Analyst™ software	On site monitoring of key parameters. OTI, WTI, LOAD Evolved Hydrogen Sensofast™
Ageing	- Furan Analysis in oil - De Polymerization of paper in oil

Preventive Maintenance
Transformer’s life mainly based on insulation

-	Oil Quality	IS : 1866
-	Core & Winding	Improvement of IR value
-	High vacuum filtration	Improvement of IR value
-	Bushing	Tan delta & Capacitance
-	Overt hauling	Life & Power loss improvement
-	Protection System	Testing & Calibration

Breakdown Maintenance
NDL believes in providing Zero breakdown

-	By Regular online trend monitoring
-	By key predict & preventive action

Schedule for diagnostic, condition monitoring & life assessment of transformers
For Predictive Maintenance:-

Test On	Tests	References	Recommended for Key & Critical Transformer	Recommended for General Purpose Transformers
Transformer Oil	Breakdown Voltage	IS 1866	6 monthly	Yearly
	Water Contents	IS 1866	6 monthly	Yearly
	Tan Delta	IS 1866	6 monthly	Yearly
	Resistively	IS 1866	6 monthly	Yearly
	Flash Point	IS 1866	6 monthly	Yearly
	Inter Facial Tension	IS 1866	6 monthly	Yearly
	Neutralization Value	IS 1866	6 monthly	Yearly
	Sediments and Sledge	IS 1866	6 monthly	Yearly
	Dissolved Gas Analysis	IS 10593	3 monthly	6 monthly
Transformer Insulation Paper	DP Of Paper	IEC 450	5 Yearly after 15 years of age.	5 Yearly after 15 years of age.
Transformer Solid Insulation	Furan Analysis	IEC 1198	Yearly after 15 years of age	2 Yearly after 15 years of age
	Insulation Resistance		Yearly	2 Yearly
	Polarization Index		Yearly	2 Yearly
	Capacitance & Tan Delta Tests		Yearly	2 Yearly
	Leakage Current Test		Yearly	2 Yearly
Conductor & Tap Changer	DC Winding Resistance		Yearly	2 Yearly
	Ratio Test & Phase Angle Error Tests		Yearly	2 Yearly
	Knee Point Voltage Tests		Yearly	2 Yearly
Core	Excitation Current Tests		Yearly	2 Yearly
	Magnetic Current Test		Yearly	2 Yearly
HV Bushing	Capacitance & Tan Delta Tests		Yearly	2 Yearly

Preventive Maintenance

Test on	Tests	References	Recommended. for Key & Critical Transformer	Recommended for General Purpose Transformers
Transformer	I.R Value Improvement (High Vacuum Filtration)	IS 10028	Yearly	Yearly
	Filtration	IS 10028	Yearly	Yearly
	Reclamation	IS 10028	Based on Oil Test	Based on Oil Test
	Overhauling	IS 10028	5 Yearly	7 Yearly