Siemens siprotec 7SA522 User Manual

2.7 Earth fault overcurrent protection in earthed systems (optional)
165
7SA522 Manual
C53000-G1176-C155-3
Inverse Time Stage
with IEC
Characteristic
Also for the inverse time overcurrent stage the operating mode is initially set: address
 2SPRGH,S. The stage can be set to operate )RUZDUG (usually towards
line), 5HYHUVH (usually towards busbar) or 1RQ'LUHFWLRQDO (in both directions).
If the stage is not required, set its mode to ,QDFWLYH.
For the inverse time overcurrent stage 3I
0P
it is possible to select from a variety of
curves depending on the version of the relay and the configuration (Section 2.1.1.2,
address ) that was selected. If an inverse overcurrent stage is not required, set
address  (DUWK)DXOW2& = 'HILQLWH7LPH. The 3I
0P
–stage can then be
used as a fourth definite time stage (refer to “Definite Time Stages” above) or deacti-
vated. With the IEC characteristics (address  (DUWK)DXOW2& = 72&,(&) are
available at address  ,(&&XUYH:
1RUPDO,QYHUVH (inverse, type A according to IEC 60255–3),
9HU\,QYHUVH (very inverse, type B according to IEC 60255–3),
([WUHPHO\,QY (extremely inverse, type C according to IEC 60255–3), and
/RQJ7LPH,QYHUVH (longtime, type B according to IEC 60255–3).
The characteristics and equations they are based on are listed in the Technical Data.
The setting of the pickup threshold ,S3,&.83 (address ) is similar to the
setting of definite time stages (see above). In this case it must be noted that a safety
margin between the pickup threshold and the set value has already been incorporat-
ed. Pickup only occurs at a current which is approximately 10 % above the set value.
The time multiplier setting ,S7LPH'LDO (address ) is derived from the
grading coordination chart which was set up for earth faults in the system.
In addition to the inverse current dependant time delay, a constant (fixed length) time
delay can also be set if this is required. The setting $GG7'(/$< (address ) is
added to the time of the set curve.
During the selection of the current and time settings, regard must be taken as to
whether a stage should be direction dependent and whether it uses teleprotection.
Refer also to the margin headings “Determination of Direction” and “Teleprotection
with Earth Fault Protection”.
Inverse Time Stage
with ANSI
Characteristic
Also for the inverse time overcurrent stage the operating mode is initially set: address
 2SPRGH,S. The stage can be set to operate )RUZDUG (usually towards
line), 5HYHUVH (usually towards busbar) or 1RQ'LUHFWLRQDO (in both directions).
If the stage is not required, set its mode to ,QDFWLYH.
For the inverse time overcurrent stage 3I
0P
it is possible to select from a variety of
curves depending on the version of the relay and the configuration (Section 2.1.1,
address ) that was selected. If an inverse overcurrent stage is not required, set
address  (DUWK)DXOW2& = 'HILQLWH7LPH. The 3I
0P
–stage can then be
used as a fourth definite time stage (refer to “Definite Time Stages” above). With the
ANSI characteristics (address  (DUWK)DXOW2& = 72&$16,) are available at
address  $16,&XUYH:
,QYHUVH,
6KRUW,QYHUVH,
/RQJ,QYHUVH,
0RGHUDWHO\,QY,
9HU\,QYHUVH,

Siemens siprotec 7SA522 Specifications

General

Brand	Siemens
Model	siprotec 7SA522
Category	Protection Device
Language	English