Siemens siprotec 7SA522 User Manual

2.8 Teleprotection for earth fault overcurrent protection (optional)
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7SA522 Manual
C53000-G1176-C155-3
The preset value should be sufficient in most cases.
Echo Function In the case of line ends with weak infeed, or not sufficient earth current, the echo func-
tion is sensible for the permissive scheme so that the infeeding line end can be re-
leased. The echo function at address  )&7:HDN,QIHHG can be activated
((&+2RQO\) or deactivated (2))). By means of this “switch” the weak infeed tripping
function can also be activated ((&+2DQG75,3, refer also to Section 2.9.1).
Please do not fail do read the comments regarding the setting of the current stage
,R0LQ7HOHSURW (address ) in the above margin heading “Earth Fault Pro-
tection Prerequisites”.
The echo delay time 7ULS(FKR'(/$< (address ) must be set long enough to
avoid incorrect echo signals resulting from the difference in fault detection pick-up time
of the earth fault protection functions at all line ends during external faults (through-
fault current). Typical setting is approx. 40 ms (presetting). This setting is only possible
via DIGSI
®
at Additional Settings.
The echo impulse duration 7ULS(;7(16,21 (address ) may be matched to the
configuration data of the signal transmission equipment. It must be long enough to
ensure that the receive signal is recognized even with different pick-up times by the
protection devices at the two line ends and different response times of the transmis-
sion equipment. In most cases approx. 50 ms (presetting) is sufficient. This setting is
only possible via DIGSI
®
at Additional Settings.
An endless echo signal between the line ends can be avoided (e.g. interference cou-
pling in the signal path) by blocking after each output of an echo signal a new echo for
a certain time (FKR%/2&.7LPH (address ). The typical setting is approx. 50
ms. After the earth fault protection signal was sent, the echo is equally blocked for the
time (FKR%/2&.7LPH. This setting is only possible via DIGSI
®
at Additional Set-
tings.
If the distance protection and earth fault protection use a common transmission chan-
nel, spurious tripping may occur when the distance protection and the earth fault pro-
tection create an echo independently of each other. For this scenario, parameter
(FKRFKDQQHO (address ) must be set to <(6. The default setting is 12.
Note
The ´(&+26,*1$/µ (FNo 4246) must be allocated separately to the output relays
for the transmitter actuation, as it is not contained in the transmit signals of the trans-
mission functions. On the digital protection data interface with permissive overreach
transfer trip mode, the echo is transmitted as a separate signal without taking any
special measures.
The echo function settings are common to all weak infeed measures and summarized
in tabular form in Section 2.9.1.

Siemens siprotec 7SA522 Specifications

General

Brand	Siemens
Model	siprotec 7SA522
Category	Protection Device
Language	English