Icos Phi / Isin Phi Characteristic; Figure 59: Operating Characteristic For Icos - GE P24DM Technical Manual

P24xM
where:
f = Angle between the Polarising Voltage (-Vres) and the Residual Current
●
f
= Relay Characteristic Angle (RCA) Setting (ISEF> Char Angle)
●
c
● V = Residual Voltage
res
I = Residual Current
●
res
V = Zero Sequence Voltage
●
o
I = Zero Sequence Current
●
o
The action of setting the PN> threshold to zero would effectively disable the wattmetric function and the device
would operate as a basic, sensitive directional earth fault element. However, if this is required, then the SEF option
can be selected from the SEF/REF Options cell in the menu.
Note:
The residual power setting, PN>, is scaled by the programmed Transformer ratios.
A further point to note is that when a power threshold other than zero is selected, a slight alteration is made to the
angular boundaries of the directional characteristic. Rather than being ±90° from the RCA, they are made slightly
narrower at ±85°.
The directional check criteria is as follows:
Directional forward: -85° < (angle(IN) - angle(VN + 180°) - RCA) < 85°
Directional reverse: -85° > (angle(IN) - angle(VN + 180°) - RCA) > 85°
8.4.2

ICOS PHI / ISIN PHI CHARACTERISTIC

In some applications, the residual current on the healthy feeder can lie just inside the operating boundary
following a fault condition. The residual current for the faulted feeder lies close to the operating boundary.
Reverse
Operation
E00618

Figure 59: Operating characteristic for Icos

P24xM-TM-EN-2.1
Icos( 1)
Polarising
Voltage
Forward
Operation
Icos( 2)
Chapter 6 - Current Protection Functions
Faulted
Feeder
1
2
Reverse
Operation
Healthy
Feeder
133