Setting Guidelines; Configuration; Settings Of Protection Function; T-Feeder Protection - ABB RELION 670 Series Applications Manual

1MRK 505 343-UEN B
6.1.4

Setting guidelines

The setting calculations are individual for each application. Refer to the different application
descriptions below.
6.1.4.1

Configuration

The configuration is done in the Application Configuration tool.
6.1.4.2

Settings of protection function

Operation : The operation of the high impedance differential function can be switched On or
Off .
U>Alarm : 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.
U>Trip : 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.
SeriesResistor : 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.
6.1.4.3

T-feeder protection

In many busbar arrangements such as one-and a half breaker, ring breaker, mesh corner, there
will be a T-feeder from the current transformer at the breakers up to the current transformers
in the feeder circuit (for example, in the transformer bushings). It is often required to separate
the protection zones that the feeder is protected with one scheme while the T-zone is
protected with a separate differential protection scheme. The 1Ph high impedance differential
HZPDIF function in the IED allows this to be done efficiently, see Figure 36.
Application manual
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.
That the settings of U>Alarm, U>Trip and SeriesResistor must be chosen such
that both U>Alarm/SeriesResistor and U>Trip/SeriesResistor are >4% of
IRated of the used current input. Normally the settings shall also be such that
U>Alarm/SeriesResistor and U>Trip/SeriesResistor both gives a value
<4*IRated of the used current input. If not, the limitation in how long time the
actual current is allowed to persist not to overload the current input must be
considered especially during the secondary testing.
U>Trip This alarm stage can be used for
Section 6
Differential protection
IP14945-1 v1
M13076-3 v2
M13076-5 v4
M13076-10 v6
M16850-4 v7
101