Turbo Alternator Rotor bars arcing

[data74]

We've got a 38 year old Brush Electrical Turbo alternator with the following equipment.

Control & Protection

• GE MULTILIN SR489, differential protection system (87/2G 1200:1 Class X).
• AVR has 1250/5 CT on A1 - A2 winding, Earth fault protection is through a floating 600/1 Neutral CT

Excitation System

Pilot Exciter is a 90Volt 1.35kVA 190Hz shaft mounted
Main Exciter is a 90kW, 1220V 407A with a field exciter of 27V, 5.4A

Main Alternator
23.375 MVA, 18.7 MW, 1225A, 11 KV , pf 0.8

The problem is that the rotor bars have extensive arcing marks on the copper bar windings. Also the end retaining rings show marks of pitting.

 

[data74]

Thanks everyone, i've sent a request to Brush for a relay setting sheet.....i know it will cost a bit of $$$$ to get the archives.