Comparative Performance Study of Dissolved Gas Analysis (DGA) Methods for Identification of Faults in Power Transformer

Table 3

Fault classification using Roger’s ratio codes [2].

Ratio codes				Identification of faults
0	0	0	0		Normal
5	0	0	0	Partial discharge
1/2	0	0	0	Thermal fault , °C
1/2	1	0	0	Thermal fault , 150°C < Temp < 200°C
0	1	0	0	Thermal fault , 200°C < Temp < 300°C
0	0	1	0	Overheating in conductors
1	0	1	0	Circulating currents in winding
1	0	2	0	Circulating currents in tank and core, overheated joints
0	0	0	1	Flashover without power follow-through
0	0	1/2	1/2	Arcing (high energy)
0	0	2	2	Continuous sparking to floating potential
5	0	0	1/2	Partial discharge with tracking (CO), involving solid insulation