Function Block - ABB RELION Series Technical Manual

1MRS758755 A
4.2.4.2
4.2.4.3
REC615 and RER615
Technical Manual

Function block

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Figure 165: Function block
Functionality
The admittance-based earth-fault protection function EFPADM provides a selective
earth-fault protection function for high-resistance earthed, unearthed and
compensated networks. It can be applied for the protection of overhead lines as well
as with underground cables. It can be used as an alternative solution to traditional
residual current-based earth-fault protection functions, such as the IoCos mode in
DEFxPDEF. Main advantages of EFPADM include a versatile applicability, good
sensitivity and easy setting principles.
EFPADM is based on evaluating the neutral admittance of the network, that is, the
quotient:
Yo Io − / Uo
=
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The measured admittance is compared to the admittance characteristic boundaries in
the admittance plane. The supported characteristics include overadmittance,
oversusceptance, overconductance or any combination of the three. The directionality
of the oversusceptance and overconductance criteria can be defined as forward,
reverse or non-directional, and the boundary lines can be tilted if required by the
application. This allows the optimization of the shape of the admittance characteristics
for any given application.
The function supports two calculation algorithms for admittance. The admittance
calculation can be set to include or exclude the prefault zero-sequence values of Io and
Uo. Furthermore, the calculated admittance is recorded at the time of the trip and it can
be monitored for post-fault analysis purposes.
To ensure the security of the protection, the admittance calculation is supervised by a
residual overvoltage condition which releases the admittance protection during a fault
condition. Alternatively, the release signal can be provided by an external binary
signal.
The function contains a blocking functionality. It is possible to block function outputs,
timers or the function itself, if desired.
Section 4
Protection functions
(Equation 10)
325