ANSI codes for Relay Identification

GEC / English Electric / Alstom /Areva identification: Labelling the model from left to right, using letter 'a' thru 'j' eg CDG31 etc a=C, b=D c=G etc: a = operating quantity C - current, D - differential, V- voltage there are 19 altogether. b = basic movement D - induction disc, M - balanced armature, T - static, there are 13 altogehter c = Application G- general or generator, E - earth, U - definite time, F - flag, M - motor, D - directional so far, CDG = current operated, induction disc general d= number of units ie CDG3x is a 3 element / unit CDG relay e = characteristic depends on relay, but for CDG, 1= std inverse (3-sec), 2= long time delay, 3=very inverse (1.55sec) f = case size 15 different cases, A=size 1 drawout, 10 terminal etc. g = case mounting F=flush etc h = identification identifies rating, contact arrangement etc. 2= 'metricated' j = sudffix where relays vary only in detail, this identifies them. '5' is for 50Hz only relays, '6' for 60Hz. Refer to publication MS/5100/2 from English Electric (now probably long out of print!

SO, CDG31EG2012JD5 is 3 element std inverse current operated induction disk general relay , size 3 drawout single ended 10 terminal, flush mounted horizontal, the 2012JD is the 'h' identification that only GEC know (but I think th D indicates hand reset flag), and the 5 at the end indicates it is a 50Hz relay.