Siemens siprotec 7SA522 User Manual

2 Functions
202
7SA522 Manual
C53000-G1176-C155-3
2.9.2.2 Setting Notes
Echo Enable 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 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
L1–E
Non-delayed Trip-
ping
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.

Siemens siprotec 7SA522 Specifications

General

Brand	Siemens
Model	siprotec 7SA522
Category	Protection Device
Language	English