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NVA100X-D - Manual - 02 - 2016
FUNCTION CHARACTERISTICS
As typical application an internal and external selective block can be used for protection of parallel
power transformers. On occurrence of a fault inside the transformer T2, the directional phase or
ground directional overcurrent element concerning the P2 relay trips to open the CB2. The 50 and
50N elements of both relays should trip if no grading margin is set in order to provide selectivity with
the directional elements. Thanks to internal (Block4) and external selective block (Block2) this grad-
ing margin can be avoided.
The 50 and 50N element on the P1 relay are blocked by means of external selective block (Block2)
coming from P2.
The 50 and 50N element on the P2 relay are blocked by means of internal selective block (Block4.
With the following setting for P1 and P2 protection relay:
I>>BLK4IN IN
(I>> Internal selective block input)
IPD>>BLK4IN OUT
(IPD>> Internal selective block output)
IE>>BLK4IN IN
(IE>> Internal selective block input)
IED>>BLK4IN OUT
(IED>> Internal selective block output)
IPD>>BLK2OUT ON
(IPD>> External selective block output)
IED>>BLK2OUT ON
(IED>> External selective block output)
I>>BLK2IN
(I>> External selective block input)
IE>>BLK2IN
(IE>> External selective block input)
ModeBLIN1 ON Iph/IE
(BLIN1 Selective block operating mode)
ModeBLOUT1 ON Iph/IE
(BLOUT1 Selective block operating mode)
the time diagram of internal (Block4) and external (Block2) selective block concerning the phase and
residual overcurrent thresholds (I>> and IE>>) are shown in the following page.
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logica_block1.ai
Block4
Block4
Block2 Iph/IE
BLOUT1
BLIN1
BLIN1
BLOUT1
Block2 Iph/IE
50N
50
CB1
T1
P1
P2
TRIP
T2
CB2
67N
NVA100
NVA100
67
50N
50
67N
67
Logic selectivity example