346
FUNCTION CHARACTERISTICS
The block output can be enabled or disabled; the 74VT-BK-EN parameter is available inside the Set
\ Profile A (or B) \ VT supervision - 74VT menu.
The alarm output goes ON after an adjustable delay (t
VT-AL
>); it may be assigned to the selected
74VT-AL-K output relays inside the Set \ Profile A (or B) \ VT supervision - 74VT menu; the same for
addressing the LED indicators 74VT-AL-L.
U
VT
<
Fun_74VT.ai
U2
U2 ≥ U
2VT
>
74VT-AL-K
74VT-AL-L
74VT-BK-K
74VT-BK-L
“1”
≡
CB TV open
“1”
≡
CB CLOSED
I2
I2 ≥ I
2VT
>
Max(UL1...UL3)
≤ U
VT
<
Max(IL1...IL3)
≥ I
VT
>
Min(UL1...UL3)
≥ U
VT
<
|IL1(k)-IL1(k-1)|
|IL2(k)-IL2(k-1)|
≤ ΔI
VT
<
|IL3(k)-IL3(k-1)|
&
&
&
&
&
&
&
&
&
S
R
Q
S
R
Q
&
≥1
≥1
≥1
t
VT-AL
T0
RESET
BLOCK 27/67/67N
U
2VT
>
I
2VT
>
t
VT-AL
I
VT
>
ΔI
VT
<
≤ ΔI
VT
<
≤ ΔI
VT
<
(ON=1≡Autoreset enabled)
(ON=1≡Reset key)
Self-reset 74VT
CB closed
MCB VT open
Reset key
Reset ThyVisor
Remote Reset
(ON=1≡remote reset)
(Remote interface reset)
Reset LEDs
74VT Block out
TRIPPING MATRIX
(LED+RELAYS)
ON≡Enable 74VT
74VT Enable
A
A
B
C
D
E
F
G
H
E
F
G
H
D
B
C
VT supervision logic diagram - 74VT
Alarm 74VT
Block 74VT
Enable (ON≡Enable)
Block1 input (ON≡Block)
Activates 74VT if one or two phase voltages are lost in the absence of negative sequence current (to discriminate asymmetrics hort circuits).
Activates 74VT if all phase voltages are lost with loaded generator.
Activates 74VT if all phase voltages are lost during commissioning of the line voltage (TV not connected), checking that no of the three currents exceeds I
VT
>.
In order to avoid trigger at the closure on polyphase short-circuit, I
VT
> should be set to a value less than I
CC
(but higher than the max inrush current).
In any case, the circuit breaker must be closed, otherwise the 74VT function is activated with standing generator.
Inhibits the 74VT activation of the polyphase short-circuitss, setting the flip-flop when impulsive variation of currentin at least one phase change arises.
Inhibition resets automatically when all three phase voltages goes above threshold and negative sequence voltage goes below the threshold.
The activation of the 74VT is maintained when at least one of conditions A, B, C is true.
The reset function can be performed manually (as long as the conditions are verified in the automatic reset D) or automatically if user defined.
The 74VT activation can occur only for circuit breaker opening to protect the VTs secondary circuit.
The 74VT activation can be inhibited by a 74VT block command applied to a binary input.
The 74VT activation is always detected. If the user can also be set the voltage-dependent protection blocking.
Block1
BLK1 74VT
Block1
Binary input INx
T 0
Logic
INx
t
ON
INx
t
ON
INx
t
OFF
T0
n.o.
n.c.
INx
t
OFF
XMR-D EQUIPMENT MANUAL
Ed. 2.9 - 02/2021
To Next Page
Loading...
Need help?
General
