106
NVA100X-D - Manual - 02 - 2016
FUNCTION CHARACTERISTICS
The alarm threshold has a defi nite time characteristic.
If the inverse sequence current drops below the threshold, the element it is restored after a delay
time t = K
cool
/(I
2
>>/I
B
)
2
; in this way, the device makes use of a memory which allows the integration
of subsequent periods of excess and relapse of the trip threshold prior to reaching the trip time.
The maximum (t
2max
) and minimum (t
2min
) operating time are adjustable; the counter may be cleared
by means an external command (serial communication, MMI or binary input).
The Reset timerI2 function must be assigned to the selected binary inputs inside the Set \ Board
1(2) inputs \ Binary input IN1-1...(IN1-x) menus.
All overcurrent elements can be enabled or disabled by setting ON or OFF the I2AL> Enable
and/or I2>> Enable parameters inside the Set \ Profi le A(or B) \ Negative sequence overcurrent
- 46G \ I2> Element (I2>> Element) menus.
The trip of I
2AL
> element may be inhibited by the start of the second element (I
2
>>) by set-
ting ON the Disabling I2> by start I2>> (I2>disbyI2>>) parameter available inside the
Set \ Profi le A(or B) \ Negative sequence overcurrent-46G \ I2>> Element menu.
All the parameters can be set separately for Profi le A and Profi le B menus.
Breaker failure (BF)
The trip element can produce the Breaker Failure output if the I2>> BF parameters are set to ON.
The parameters are available inside the Set \ Profi le A(or B) \ negative sequence overcurrent - 46G
\ I2>> Element menu.
[1]
CT supervision (74CT
The protection element is blocked off whenever the CT supervision function is active, so
that no unwanted trip can arise if any fault on the CTs secondary circuits are detect;
[2]
the Block functions enable from 74CT parameter (74CT-BK-EN) is available inside the
Set \ VT supervision - 74VT, and Set \ CT supervision - 74CT menus.
Note 1 The common settings concerning the Breaker failure protection are adjustable inside the Breaker Failure - BF menu.
Note 2 The exhaustive treatment of the VT and CT supervision function may be found inside the CONTROL AND MONITORING section.
Operating time for the negative sequence overcurrent element - 46G
Start I
2
>>
Trip I
2
>>
RESET
Conteggio
temporizzatore
I
2
>>
I
2
I
B
t
START
t
t
2MAX
K
heat
K
cool
K
cool
K
cool
K
cool
Operating time for the negative sequence overcurrent element - 46G
Start I
2
>>
Trip I
2
>>
RESET
Conteggio
temporizzatore
I
2
>>
I
2
I
B
t
START
t
t
2MAX
K
heat
K
cool
K
cool
K
cool
K
cool
all-F21.ai
I
2
>> Element
I
2AL
Element
Block1
Block1
I
2
I
2
Block3
Block1
Block3
I
2
>>
BF
Block1
I
2
>>
Enable
I
2AL
>
Enable
I
2
>>
inv
t
2MIN
K
heat
K
cool
t
2MAX
I
2AL>def
t
2AL>def
I
2AL
> inhibition
I
2
>>
Start
I
2
>>
Trip
I
2
>>
Trip
I
2AL
>
Start
I
2AL
>
Trip
Logic diagram concerning the negative sequence overcurrent element - 46G
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