Some Common Terms used with meanings
1) ONAN - Oil Natural, Air Natural (For Transformer Cooling)
2) ONAF - Oil Natural, Air Forced (For Transformer Cooling)
3) OFAF - Oil Forced, Air Forced (For Transformer Cooling)
4) WTI - Winding Temperature Indicator
5) OTI - Oil Temperature Indicator
6) PRV - Pressure Relief Valve
7) OSR - Oil Surge Relay
8) OLTC - On Load Tap Changer
9) RTCC - Remote Tap Change Control
10) MOG - Magnetic Oil Level Gauge
11) IDMT - Inverse Definite Minimum Time (For Relay)
12) NO - Normally Open Contact
13) NC - Normally Closed Contact
14) LILO - Loop In Loop Out (Used for defining Substation)
15) CRP - Control Relay Panel
16) TTB - Test Terminal Block
17) ACDB – A.C. Distribution Board
18) DCDB – D.C. Distribution Board
19) MB – Marshalling Box (For Breaker, Transformer control)
20) AVR – Automatic Voltage Control (For Tap Changing on RTCC Pan