ABB RER670 - Compensated Earthing Systems

The ZRWPDIS application function is designed to detect and clear the faults
mentioned in Table 14 with reliability in order to maintain the system stability.
Table 14: Earthing systems and possible faults
Earthing system Types of fault
Compensated earthing systems • Single phase earth fault of short duration
• Sustained single phase earth fault
•
Cross country double earth faults
• Two phase short circuit with and without
earth connection
Solidly earthing systems • Single phase earth fault
• Two phase short circuit with and without
earth connection
High impedance earthing systems •
Single phase earth fault
• Cross country double earth faults
•
Two phase short circuit with and without
earth connection
7.2.2.1 Compensated earthing systems
GUID-630CAFB0-1838-4670-A8A5-20910322BEAE v2
In compensated grids, a distinction must be made between the following types of
faults:
•
Single earth fault, short-term (< 5sec)
•
Single earth fault, sustained (> 5sec) (= sustained earth fault)
• Double cross country line-to-earth faults with separate earth contact points
• Phase-to-phase short-circuit, earthed and unearthed
When the single earth faults occurs, the fault currents are reduced by the earth-fault
neutralizers or the active compensation facility level decreases until the flashovers
are neutralized automatically. The concerned phase is not to be tripped. However,
the faulty phase has to be identified and indicated (earth-fault protection/
determination of the earth fault direction).
When the cross country phase-to-earth faults occurs, the two phases have to be
handled with different time grading so that a delayed disconnection of the L2 phase
enables elimination of the fault via the earth-fault neutralizing function. The L2
phase is tripped only if the neutralization after a cross country line-to-earth fault
and a trip of the L1 phase has failed.
Phase preference logic
In compensated earthing systems, phase preference logic is used to achieve the
correct phase selective tripping during two simultaneous single phase earth faults
in different phases on different line sections.
Due to compensated earthing, the earth faults in these systems involve very low
fault currents, typically below 25A. At the same time, the system voltage on the
Section 7 1MRK 506 375-UEN A
Impedance protection
98 Railway application RER670 2.2 IEC
Application manual