Siemens siprotec 7SA6 User Manual page 604

Installation and Commissioning
Blocking Scheme
8-60
The function of the permissive overreach transfer schemes is described in
Subsubsections 6.4.1.4 to 6.4.1.6.
In the case of these release schemes, a simple check of the transmission paths from
one line end is possible using the echo function. The echo function must be activated
at both line ends, i.e. address  )&7 :HDN ,QIHHG = (&+2 RQO\; with the
setting (&+2 DQG 75,3 a trip may result at the line end opposite to the test location!
A short-circuit is simulated outside Z1, with the 3HUPLVVLYH 2YHUUHDFK or
81%/2&.,1* inside Z1B, with the 'LUHFWLRQDO &RPSDULVRQ 3LFNXS
somewhere in forward direction. This may be done with secondary injection test
equipment. As the device at the opposite line end is not picked up, the echo function
comes into effect there, and a trip command at the line end initiating the test, results.
If no trip command results, the transmission path must be checked again, in particular
that the echo signals are assigned to the transmit outputs.
In case of a phase-segregated transmission the above-mentioned checks are carried
out for each phase. The correct phase allocation must also be checked.
The tests must be executed at both line ends. For three terminal lines, it must be done
at each line end, for each transmission path.
The functioning of the echo delay time and the derivation of the circuit breaker
switching status should also be tested at this time (the functioning of the protection at
the opposite line end is tested):
The circuit breaker of the feeder to which the protection belongs must be open, as is
the circuit breaker at the opposite end of this line. As described above, a fault is again
simulated. A receive signal impulse delayed by a little more than twice the signal
transmission time, should appear via the echo from the opposite line end; the device
should also issue a trip command.
The circuit breaker at the opposite line end should now be closed (with open isolators).
After simulation of the same fault, a receive signal again appears and a trip command
is again issued. However this time the receive signal is additionally delayed by the
echo delay time of the device at the opposite line end (0,04 s presetting, address 
7ULS(FKR '(/$<).
If the echo delay response is opposite to the above description, the mode of operation
of the corresponding binary inputs (H–active/L–active) at the opposite line end must
be corrected (refer to Sub-section 5.2.4).
The circuit breaker is opened again.
The tests must also be carried out at both line ends, in the case of three terminal lines,
at each end, for each transmission path. Please take note of the last margin heading
"Important for All Schemes"!
Prerequisites are: 7HOHSURWHFWLRQ IRU 'LVWDQFH SURW 7HOHSURW
'LVW in address  (section 5.1) is set to the overreach transfer with a blocking
signal i.e. %ORFNLQJ; furthermore, the setting in address  must be set to )&7
7HOHS () 21. Naturally, the corresponding send and receive signals must also be
assigned to the corresponding binary output and input.
For more details about the function of the blocking scheme refer to Subsubsection
6.4.1.7. In the case of the blocking scheme, communication between the line ends is
necessary.
On the transmitting end, a fault in the reverse direction is simulated, while at the
receiving end a fault in Z1B but beyond Z1 is simulated. This may be achieved with
secondary injection test equipment at each end. As long as the transmitting end is
7SA6 Manual
C53000-G1176-C133-1