Thytronic NA20, Manual, Page: 77 / 208

FUNCTION CHARACTERISTICS
77 NA20 - Manual - 04 - 2022
Phase overcurrent (50/51) - Third element logic diagram (I>>>)
Fun_50-51S3.ai
t
>>>RES
T 0
RESET
t
>>>def
0 T
≥ 1
t
>>>def
t
>>>RES
Start I>>>
Trip I>> >
CB-State
Start I
2ndh>
ON ≡ Enable 3rd overcurrent element
Block1, Block2
&
I>> > TR-K
I>> > TR-L
I>> > ST-L
I>> > ST-K
T 0
t
CLP>>>
&
2nd harmonic restraint enable (ON ≡ Enable)
I>>>2ndh-REST
ICLP>>>Mode
t
CLP>>>
BF Enable (ON ≡ Enable)
I>>>BF
towards BF logic
I>>> BF
&
Trip I>>>
TR
IP
PIN
G
M
AT
RIX
(
LE
D+R
EL
AY
S)
A
B
C
Output
t
CLP>>>
I >>> Enable
I>>> overcurrent element (50/51) Block diagram
t
CLP>>>
Output t
CLP>>>
CB State CB OPEN CB CLOSED CB OPEN
t
0.1 s
HIGH THRESHOLD/
BLOCK
LOW THRESHOLD/
UNBLOCK
HIGH THRESHOLD/
BLOCK
A = ON - Change setting
B = OFF
C = ON - Element blocking
&
(ON ≡ Inhibit)
Start I>>>
Start I>>>
Start I>>>
(ON ≡ Inhibit)
I> inhibition
I> disbyl>>>
&
I>> inhibition
I>> disbyl>>>
≥ 1 CLP I>>>
I
L1
I
L2
≥ 1
(Pickup within CLP)
(Pickup outside CLP)
I
CLP>>def
I
CLP>>inv
I
L1
≥ I >>>
A =“1” A =“0 or OFF”
I
L3
&
State
I
L1
≥ I >>>
def
I >>>
def