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Section 16
Scheme communication
16.3.3
716
requires a detection of the fault by an independent tripping zone 1. To avoid
sequential tripping as described, and when zone 1 is not available, weak-end infeed
tripping logic is used. The weak end infeed function only works together with
permissive overreach communication schemes as the carrier send signal must cover
the complete line length.
The WEI function sends back (echoes) the received signal under the condition that
no fault has been detected on the weak-end by different fault detection elements
(distance protection in forward and reverse direction).
Also, the WEI function can be additionally extended to trip the breaker in the weak
side. The trip is achieved when one or more phase voltages are low during an echo
function.
In case of single-pole tripping, the phase voltages are used as phase selectors
together with the received signal CRLn.
When used with the blocking teleprotection scheme some limitations apply:
•
Only the trip part of the function can be used together with the blocking
scheme. It is not possible to use the echo function to send the echo signal to
the remote line IED. The echo signal would block the operation of the distance
protection at the remote line end and in this way prevents the correct operation
of a complete protection scheme.
•
A separate direct intertrip channel must be arranged from the remote end when
a trip or accelerated trip is given there. The intertrip receive signal is connect
to input CRL.
•
The WEI function shall be set to WEI=Echo&Trip. The WEI function block
will then give phase selection and trip the local breaker.
Avoid using WEI function at both line ends. It shall only be activated at the weak-
end.
Setting guidelines
The parameters for the current reversal logic and the weak-end infeed logic (WEI)
function are set via the local HMI or PCM600.
Common base IED values for the primary current (IBase), primary voltage (UBase)
and primary power (SBase) are set in global base values for settings function
GBASVAL.
GlobalBaseSel: Selects the global base value group used by the function to define
IBase, UBase and SBase as applicable.
1MRK 506 369-UEN B
Line distance protection REL670 2.2 IEC
Application manual
IP15024-1 v1
M13856-4 v6
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