Residual Overvoltage Logic; Application Notes; Calculation For Solidly Earthed Systems; Figure 115: Residual Overvoltage Logic - GE P4A Technical Manual

Chapter 10 - Voltage Protection Functions
5.2

RESIDUAL OVERVOLTAGE LOGIC

VN
VN>1 Voltage Set
832
VTS Fast Block
418
VN>1 Timer Blk

Figure 115: Residual Overvoltage logic

The Residual Overvoltage module (VN>) is a level detector that detects when the voltage magnitude exceeds a set
threshold, for each stage. When this happens, the comparator output produces a Start signal (VN>(n) Start), which
signifies the "Start of protection". This can be blocked by a VTS Fast block signal. This Start signal is applied to the
timer module. The output of the timer module is the VN> (n) Trip signal which is used to drive the tripping output
relay.
5.3

APPLICATION NOTES

5.3.1

CALCULATION FOR SOLIDLY EARTHED SYSTEMS

Consider a Phase-A to Earth fault on a simple radial system.
232
&
&
IDMT/DT
P54A/B/C/E
804
VN>1 Start
700
VN>1 Trip
V00802
P54xMED-TM-EN-1