Setting Guidelines - ABB RET670 Applications Manual

Section 3
IED application
3.5.3.4
144
7 Transformer input module where this current input is located.
Note that the CT ratio for high impedance differential protection application
must be set as one.
• For main CTs with 1A secondary rating the following setting values shall be entered:
1A and CTsec = 1A
=
• For main CTs with 5A secondary rating the following setting values shall be entered:
5A and CTsec = 5A
=
• The parameter
8 Connection made in the Signal Matrix, which connects this current input to first input channel of the
preprocessing function block (9). For high impedance differential protection preprocessing function
block in 3ms task shall be used.
9 Preprocessing block, which has a task to digitally filter the connected analogue inputs.
Preprocessing block output AI1 shall be connected to one instances of 1Ph high impedance
differential protection function HZPDIF (87) (for example, instance 1 of HZPDIF (87) in the
configuration tool).

Setting guidelines

The setting calculations are individual for each application. Refer to the different
application descriptions below.
Configuration
The configuration is done in the Application Configuration tool. Signals from for
example, check if criteria are connected to the inputs as required for the application.
BLOCK input is used to block the function for example, from external check criteria.
BLKTR input is used to block the function tripping for example, from external check
criteria. The alarm level will be operative.
Settings of protection function
Operation: The operation of the high impedance differential function can be switched
Enabled or Disabled.
AlarmPickup: Set the alarm level. The sensitivity can roughly be calculated as a divider
from the calculated sensitivity of the differential level. A typical setting is 10% of
TripPickup. It can be used as scheme supervision stage.
tAlarm: Set the time for the alarm. A typical setting is 2-3 seconds.
TripPickup: Set the trip level according to the calculations in the examples for each
application example. The level is selected with margin to the calculated required
voltage to achieve stability. Values can be 20-200 V dependent on the application.
CTStarPoint shall always be left to the default value ToObject
1MRK504116-UUS C
CTprim
CTprim
Application manual