Setting Notes - Siemens SIPROTEC 7SA522 Manual

2 Functions
2.9.2.2

Setting Notes

Echo Enable
Phase Selection
Non-delayed Trip-
ping
202
Applications with a transmission channel used by both the distance and the earth fault
protection spurious trippings may occur, if distance protection and earth fault protec-
tion create an echo independently from each other. In this case parameter
(FKR FKDQQHO (address  ) has to be set to <(6. The default setting is 12.
Phase selection is accomplished via undervoltage detection. For this purpose no ab-
solute voltage threshold in volts is parameterized but a factor (address  8SKH
)DFWRU), which is multiplied with the measured phase-phase voltage, and yields the
voltage threshold. This method accounts for operational deviations from the rated
voltage in the undervoltage threshold and adjusts them to the prevailing conditions.
Since a sound positive phase-to-phase voltage is not available in the event of a fault,
the undervoltage threshold is delayed. Thus changes in the phase-to-phase voltage
affect the threshold only slowly. The time constant can be set at address  7LPH
FRQVW τ. The undervoltage is determined for all 3 phases.
If the measured phase-to-phase voltage falls below the threshold (address 
3ROH2SHQ9ROWDJH), undervoltage is no longer detected in this phase.
Figure 2-91 Undervoltage Detection for U
An undelayed TRIP command is issued if a receive signal ´!:, UHFHSWLRQµ is
present and an undervoltage condition is detected simultaneously. If another protec-
tion function capable to detect faults has picked up in the relay, the corresponding
phases in the weak-infeed function are blocked. The receive signal is prolonged at
address  5HF ([W, so that a trip command is still possible in the event of a
quick dropout of the transmitting line end.
To avoid a faulty pickup of the weak infeed function following tripping of the line and
reset of the fault detection, the function cannot pick up any more once an inverse-time
overcurrent fault detection in the affected phase was present.
If a receive signal applies and no undervoltage is detected but the zero sequence
current threshold ,! 7KUHVKROG is exceeded, (address ) a fault on the line
can be assumed. If this state (receive signal, no undervoltage and zero sequence cur-
rent) applies for longer than 500 ms, 3-pole tripping is initiated. The time delay of "3I0>
exceeded" is set at address  7 ,! ([W. If the zero sequence current
exceeds the threshold ,! 7KUHVKROG for longer than the set time 7 ,! DODUP
(address ), the annunciation ´, GHWHFWHGµ is issued.
The non-delayed stage operates only if binary input ´!:, UHF 2.µ reports the
proper functioning of the transmission channel.
Moreover, the phase-selective block signals BLOCK Weak Inf affect the non-delayed
logic. Faulty pickups are thus prevented, especially after the dedicated line end was
shut down.
L1–E
7SA522 Manual
C53000-G1176-C155-3