R series: Set the value of the stabilizing series resistor. Calculate the value according to
the examples for each application. Adjust the resistor as close as possible to the
calculated example. Measure the value achieved and set this value here.
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.
T-feeder protection
In many busbar arrangements such as breaker-and-a-half, ring breaker, mesh corner,
there will be a T-feeder from the current transformer at the breakers up to the current
transformers in the transformer bushings. It is often required to separate the zones so
the zone up to the bushing is covered from one differential function and the
transformer from another. The 1Ph high impedance differential HZPDIF (87) function
in the IED allows this to be done efficiently, see figure
40.
3·87
ANSI05000739-2-en.vsd
ANSI05000739 V2 EN
Figure 40: The protection scheme utilizing the high impedance function for the T-
feeder
Normally this scheme is set to achieve a sensitivity of around 20 percent of the rated
current so that a low value can be used on the resistor.
1MRK504116-UUS C Section 3
IED application
145
Application manual
To Next Page
Loading...
Need help?
General
