Fault Type Determination; Fault Location - GE D90 Plus Instruction Manual

FAULT REPORT

Fault type determination

Fault location

508
has not been reset (the OR gate output is still high), the fault report is not triggered again.
Considering the reset time of protection elements, there is very little chance that fault
report can be triggered twice in this manner.
Each fault report is stored as a file, and the relay capacity is 15 files. A 16th trigger
overwrites the oldest file. The 16th report overwrites the first one regardless of which fault
report feature produced the 16th and the first records.
The EnerVista software is required to view all captured data. The front panel interface can
be used to view the following information:
• Prefault and fault current and voltage phasors
• Active setting group
• Date and time of trigger
• Reclose shot number
• Fault type
• Distance location of the fault
Fault type determination is required for calculation of fault location. The fault
determination algorithm uses the angle between the negative-sequence and positive-
sequence components of the relay currents. To improve accuracy and speed of operation,
the fault components of the currents are used. That is, the pre-fault phasors are subtracted
from the measured current phasors. In addition to the angle relationships, certain extra
checks are performed on magnitudes of the negative-sequence and zero-sequence
currents.
The single-ended fault location method assumes that the fault components of the currents
supplied from the local and remote systems are in phase. The figure shows an equivalent
system for fault location.
Figure 441: Equivalent system for fault location
The following equation describes the voltage at the local bus for this equivalent system,
where m represents the required per-unit distance to the fault and Z represents the
positive-sequence impedance of the line:
The currents from the local and remote systems can be parted between their fault (F) and
pre-fault load (pre) components as follows:
Neglecting the shunt parameters of the line, as follows:
CHAPTER 10: DIGITAL FAULT RECORDER
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Eq. 46
Eq. 47
Eq. 48