P Rotection F Eatures - GE 745 Instruction Manual

INTRODUCTION
2.1.2 Protection Features
Symbol Common protection element
59/81-1 Volts-per-hertz 1
59/81-2 Volts-per-hertz 2
81U-1 Underfrequency 1
81U-2 Underfrequency 2
81U-R1 Frequency decay rate 1
81U-R2 Frequency decay rate 2
81U-R3 Frequency decay rate 3
81U-R4 Frequency decay rate 4
81-H5 5th harmonic Level
81O Overfrequency
87 Differential (percent)
50/87 Instantaneous differential
AN-1 Analog input level 1
AN-2 Analog input level 2
--- Insulation aging: aging factor, hottest spot limit,
and total accumulated life
--- Tap changer monitor
2–2
• Dynamic CT ratio mismatch correction which monitors the on-load tap position and
automatically corrects for CT ratio mismatch
• FlexLogic™ which allows PLC style equations based on logic inputs and protection
elements to be assigned to any of the 745 outputs.
The 745 also includes a powerful testing and simulation feature. This allows the protection
engineer the ability to test the relay operation based on captured or computer generated
waveform data which can be converted to a digitized format and downloaded into the
745's simulation buffer for "playback". A waveform capture function that records waveform
data for fault, inrush, or alarm conditions is also provided.
The auto-configuration function eliminates the need for any special CT connections by
having all CTs connected in wye.
The following table outlines the protection features available for windings 1, 2, and 3, as
well as the common protection elements.
Symbol Winding 1 protection elements
150/46 Negative sequence instantaneous overcurrent
151/46 Negative sequence time overcurrent
150P1 Phase instantaneous overcurrent 1
150P2 Phase instantaneous overcurrent 2
150N1 Neutral (3I ) instantaneous overcurrent 1
0
150N2 Neutral (3I ) instantaneous overcurrent 2
0
150G1 Ground instantaneous overcurrent 1
150G2 Ground instantaneous overcurrent 2
151P Phase time overcurrent
151N Neutral (3I
) time overcurrent
0
151G Ground time overcurrent
187TG Ground differential (restricted ground fault)
1THD Total harmonic distortion level
1AD Current demand
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 2: OVERVIEW