ABB Relion 670 Series Applications Manual page 128

Section 7
Differential protection
Pos
1
2
3
4
5
6
7.1.4 Setting guidelines
The setting calculations are individual for each application. Refer to the different application
descriptions below.
7.1.4.1 Configuration
The configuration is done in the Application Configuration tool.
7.1.4.2 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 certain percentage
of the selected Trip level. A typical setting is 10% of
scheme CT supervision.
tAlarm : Set the time delay for the alarm. A typical setting is 2-3 seconds.
TripPickup : Set the trip level according to the calculations (see examples below for a guidance).
The level is selected with margin to the calculated required voltage to achieve stability. Values can
be within 20V - 400V range dependent on the application.
R series : Set the value of the used stabilizing series resistor. Calculate the value according to the
examples for each application. Adjust the resistor as close as possible to the calculated value.
Measure the value achieved and set this value for this parameter.
122
Description
Scheme grounding point
Ensure that only one grounding point exists in this scheme.
One-phase plate with stabilizing resistor and metrosil. Protective ground is a separate 4 mm screw
terminal on the plate.
Necessary connection for the metrosil.
Position of optional test switch for secondary injection into the high impedance differential IED.
Necessary connection for stabilizing resistor.
How to connect the high impedance restricted earth fault protection scheme to one CT input in IED.
The value shall always be high impedance. This means for example, for 1A circuits
say bigger than 400 ohms (400 VA) and for 5 A circuits say bigger than 100 ohms
(2500 VA). This ensures that the current will circulate and not go through the
differential circuit at through faults.
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TripPickup. This alarm stage can be used for
1MRK 511 401-UUS F
IP14945-1 v1
M13076-3 v2
M13076-5 v4
M13076-10 v6
Bay control REC670
Application manual