Relay 60FL (VT Fuse Loss)

Unit Load Rejection caused by generator VT (voltage Transformer) fuse loss (broken) is luckless. First detected was coming from MW sensor A and B was different reading more than 10MW and the different reading will be increase until fuse totally burn or blown.

VT fuse broken should be detected by Relay 60FL. This relay is not protection function but only detection to inform the operator.

Usually we have 3 peaces of VT and 2 signals is transffered to DCS. We could de-selected any instrument which got VT fuse broken.

The Unit still in service eventhough Relay 60FL active but next 10 minutes Relay 24 V/F active to energize 86G generator lock out relay to open Generator CB (GMCB)and the Unit got Load Rejection (House Load).


Generator Protection Relay 60FL & 24V/F


















Generator Protection Relay Scematic Diagram
from http://www.gedigitalenergy.com/multilin/images/products/489/489-block.gif



















House Load Event.
Load rejection signal should be following House Load Operation but has limitation less than 40min for avoid LP Exhaust overheat and blade fatigue with vibration in lower steam flow condition.



In order to prevent Turbine and Generator over-speed caused by PLU (Power Load Unbalance) between Steam Turbine output and generator load different 40%, all Turbine control valves will close quickly.