Function Block - ABB Relion Technical Manual

1MRK 502 048-UUS A
6.2.3
6.2.4
Technical manual
high sensitivity and high speed tripping as it protects each winding separately and thus
does not need inrush stabilization.
The low-impedance function is a percentage biased function with an additional zero
sequence current directional comparison criterion. This gives excellent sensitivity and
stability during through faults. The function allows the use of different CT ratios and
magnetizing characteristics on the phase and neutral CT cores. Unlike high impedance
restricted ground fault it allows for mixing with other functions and protection IEDs on the
same CT cores.

Function block

REFPDIF (87N)
I3P* TRIP
I3PW1CT1* PICKUP
I3PW2CT1* DIR_INT
BLOCK BLK2H
IRES
IN
IBIAS
IDIFF
ANGLE
2NDHARM
ANSI09000275-1-en.vsd
ANSI09000275 V1 EN
Figure 43: REFPDIF (87N) function block
Signals
Table 31: Input signals for the function block REFPDIF (REF1-)
Signal
I3P
I3PW1CT1
I3PW2CT1
BLOCK
Table 32: Output signals for the function block REFPDIF (REF1-)
Signal
TRIP
START
DIROK
BLK2H
IRES
Table continues on next page
Differential protection
Description
Group signal for neutral current input
Group signal for primary CT1 current input
Group signal for secondary CT1 current input
Block of function
Description
General trip signal
General start signal
Directional criteria has operated for internal fault
Block due to 2-nd harmonic
Magnitude of fundamental frequency residual current
Section 6
119