Hitachi Relion 670 Series Applications Manual page 291

1MRK506375-UEN Rev. N
IEC99000044 V3 EN-US
Figure 140:
To handle this the send signal CS or CSLn from B2 is held back until the reverse zone IRVLn has
reset and the tDelayRev time has been elapsed. To achieve this the reverse zone on the distance
protection shall be connected to input IRV and the output IRVL shall be connected to input BLKCS
on the communication function block ZCPSCH.
The function can be blocked by activating the input IRVBLK or the general BLOCK input.
13.2.2.2 Weak-end infeed logic
Permissive communication schemes can only operate when the protection in the remote IED can
detect the fault. The detection requires a sufficient minimum fault current, normally >20% of I
fault current can be too low due to an open breaker or low short-circuit power of the source. To
overcome these conditions, weak-end infeed (WEI) echo logic is used. The fault current can also be
initially too low due to the fault current distribution. Here, the fault current increases when the breaker
opens at the strong terminal, and a sequential tripping is achieved. This 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.
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.
13.2.3 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.
Railway application RER670
Application manual
L1
A1 B1
L2
A2 B2
IEC99000044-2.vsd
Current distribution for a fault close to B side when breaker B1 has opened
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Section 13
Scheme communication
M13895-16 v8
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IP15024-1 v1
M13856-4 v6
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