Setting Guidelines - ABB RER670 Applications Manual

Section 8
Current protection
8.4.3
170
• Earth-fault protection of feeders in effectively earthed two-phase railway
supply system. Normally these feeders have radial structure.
• Back-up earth-fault protection of transmission lines.
• Sensitive earth-fault protection of transmission lines. EF2PTOC can have
better sensitivity to detect resistive phase-to-earth-faults compared to distance
protection.
• Back-up earth-fault protection of power transformers.
• Earth-fault protection of different kinds of equipment connected to the power
system such as shunt capacitor banks and others.
In many applications, several steps with different current operating levels and time
delays are needed. EF2PTOC can have up to two, individual settable steps. The
flexibility of each step of EF2PTOC is great. The following options are possible:
Non-directional/Directional: In some applications the non-directional functionality
is used. This is mostly the case when no fault current can be fed from the protected
object itself. In order to achieve both selectivity and fast fault clearance, the
directional functionality may be necessary. Note that for directional operation
additional logic in the IED configuration tool is needed.
Choice of time characteristics: There are several types of time characteristics
available such as definite time delay and different types of inverse time
characteristics. The selectivity between different overcurrent protections is
normally enabled by co-ordination between the operate time of the different
protections. To enable optimal co-ordination all overcurrent protections, to be co-
ordinated against each other, should have the same time characteristic.
Table 20: Time characteristics
Curve name
IEC Normal Inverse
IEC Very Inverse
IEC Extremely Inverse
IEC Definite Time
ASEA RI
Normally it is required that EF2PTOC shall reset as fast as possible when the
current level gets lower than the operation level.

Setting guidelines

When inverse time overcurrent characteristic is selected, the
operate time of the step will be the sum of the inverse time delay
and the set definite time delay. Thus, if only the inverse time delay
1MRK 506 375-UEN A
Railway application RER670 2.2 IEC
Application manual
IP14988-1 v1
M15282-3 v11