Wattmetric Characteristic; Figure 45: Types Of Directional Control; Figure 46: Resistive Components Of Spill Current - GE MiCOM P40 Agile Technical Manual

P14D
Solidly Earthed Systems
Directional SEF
High Impedance Fault
V00655

Figure 45: Types of directional control

The device supports standard core-balanced directional control as well as Isin(f), Icos(f) and Wattmetric
characteristics.
If you are using directional SEF protection, you select the required polarisation using the SEF Options setting in the
SEF PROTECTION column.
8.4.1

WATTMETRIC CHARACTERISTIC

Analysis has shown that a small angular difference exists between the spill current on healthy and faulted feeders
for earth faults on compensated networks. This angular difference gives rise to active components of current
which are in anti-phase to one another.
Active component
of residual current:
Faulted Feeder
Active component
of residual current:
Healthy Feeder
E00617

Figure 46: Resistive components of spill current

Consequently, the active components of zero sequence power will also lie in similar planes, meaning an IED
capable of detecting active power can make discriminatory decisions. If the Wattmetric component of zero
sequence power is detected in the forward direction, then this would indicate fault on that feeder. If power is
detected in the reverse direction, then the fault must be present on an adjacent feeder or at the source.
For operation of the directional earth fault element, all three of the settable thresholds must be exceeded; namely
the current ISEF>, the voltage ISEF>VNpol Set and the power PN> Setting.
P14D-TM-EN-8
Unearthed Systems
(insulated systems)
Directional SEF
Core-balanced INsin(j)
CT characteristic
Directional
Wattmetric
Earth Fault
VN x IN sin (j)
(reactive power)
(HIF)
Core-balanced
Vres = -3Vo
IR3
IR1
Compensated Systems
(Petersen coil)
Directional SEF
INcos(j)
characteristic
Wattmetric
VN x IN cos (j)
(active power)
CT
IH1
IH2
Zero torque line
for 0 RCA
Key:
IR3
IR1
IH1, IH2
IL
Chapter 6 - Current Protection Functions
Resistance-Earthed Systems
Directional SEF
INcos(j)
characteristic
Core-balanced
CT
Directional
Earth Fault
High Impedance Fault
(HIF)
Operate
IL
Restrain
- Residual current on faulty feeder
- Residual current on healthy feeder
- Charging current from rest of system
- Current through earthed coil
109