ABB REC650 - Single Breaker Line Bay, Single or Double Busbar, in High Impedance Grounded Network

• Close in line short circuits: For close in faults the instantaneous phase overcurrent
protection should be used. As the fault current is often high at this fault case fast
tripping is essential. It is however important to base the setting on fault calculations
considering different operational states.
• Short circuits on the whole line length. For these faults the four step phase overcurrent
protection should be used. The four step phase overcurrent protection has the
possibility of directional function as well as different time delay characteristics. It is
important to base the setting on fault calculations considering different operational
states as well as time delay co-ordination with other protections in the system.
• Close in line phase-to-ground faults: For close in faults the instantaneous residual
overcurrent protection should be used. As the fault current is often high at this fault
case fast tripping is essential. It is however important to base the setting on fault
calculations considering different operational states.
• Phase-to-ground faults on the whole line length. For these faults the four step residual
overcurrent protection should be used. The four step residual overcurrent protection
has the possibility of directional function as well as different time delay
characteristics. It is important to base the setting on fault calculations considering
different operational states as well as time delay co-ordination with other protections
in the system.
• Failure of the circuit beaker to interrupt fault current after protection trip. The breaker
failure protection function is essential in a protection system using local redundancy.
• Autoreclosing is normally used on overhead power lines as most faults are transient,
that is, the arcing fault will extinguish after a short zero voltage interval.
2.3.3 Single breaker line bay, single or double busbar, in high
impedance grounded network
Normally the following fault scenarios require back-up protection functions:
• Close in line short circuits: For close in faults the instantaneous phase overcurrent
protection should be used. As the fault current is often high at this fault case fast
tripping is essential. It is however important to base the setting on fault calculations
considering different operational states
• Short circuits on the whole line length. For these faults the four step phase overcurrent
protection should be used. The four step phase overcurrent protection has the
possibility of directional function as well as different time delay characteristics. It is
important to base the setting on fault calculations considering different operational
states as well as time delay co-ordination with other protections in the system
• Phase-to-ground faults. In high impedance grounded networks the fault current at a
single phase-to-ground fault is small. For these faults the sensitive residual
overcurrent protection should be used. The sensitive residual overcurrent protection
has the possibility of directional function. It is important to base the setting on fault
1MRK 511 286-UUS A Section 2
Application
33
Application manual