Thytronic NA11 User Manual

59
NA11 - Manual - 02 - 2009
FUNCTION CHARACTERISTICS
Residual overcurrent - 50N/51N
Preface
Three operation thresholds, independently adjustable (I
E
>, I
E
>>, I
E
>>>) with adjustable delay (t
E
>,
t
E
>>, t
E
>>>).
The fi rst one (I
E
>) may be programmed with defi nite or inverse time according the IEC and ANSI/IEEE
standard, as well as with EM curve.
The second and third thresholds (I
E
>>, I
E
>>>) with independent time.
For each threshold a reset time can be set (t
E>RES
, t
E>>RES
, t
E>>>RES
) useful to reduce the clearing
time for intermittent faults.
The fi rst threshold trip may be inhibited by start of the second and/or third threshold (I
E
>>, I
E
>>>).
Similarly the second threshold trip may be inhibited by start of the third threshold (I
E
>>>).
Operation and settings
The residual fundamental frequency current)
[1]
is compared with the setting value. Current above
the associated pickup value is detected and a start is issued. After expiry of the associated operate
time a trip command is issued; if instead the current drops below the threshold, the element it is
restored.
The fi rst threshold (I
E
>) may be programmed with defi nite or inverse time according the following
characteristic curves:
Standard Inverse Time (IEC 255-3/BS142 type A or SIT): t = 0.14 · t
E
>
inv
/ [(I
E
/I
E
>
inv
)
0.02
- 1]
Very Inverse Time (IEC 255-3/BS142 type B or VIT): t = 13.5 · t
E
>
inv
/ [(I
E
/I
E
>
inv
) - 1]
Extremely Inverse Time (IEC 255-3/BS142 type C or EIT): t = 80 · t
E
>
inv
/ [(I
E
/I
E
>
inv
)
2
- 1]
Moderately Inverse (ANSI/IEEE type MI): t = t
E
>
inv
· {0.01 / [(I
E
/I
E
>
inv
)
0.02
- 1] +
0.023}
Very Inverse (ANSI/IEEE type VI): t = t
E
>
inv
· {3.922 / [(I
E
/I
E
>
inv
)
2
- 1] + 0.098}
Extremely Inverse (ANSI/IEEE type EI): t = t
E
>
inv
· {5.64 / [(I
E
/I
E
>
inv
)
2
- 1] + 0.024}
Electromechanical (EM): t = t
E
>
inv
· {0.28 / [-0236 · (I
E
/I
E
>
inv
)
-1
+ 0.339]}
Where:
t: operate time
I
E
>: pickup value
t
E
>
inv
: operate time setting
For all inverse time characteristics, following data applies:
Asymptotic reference value (minimum pickup value): 1.1 I
E
>
Minimum operate time: 0.1 s
Range where the equation is valid:
[2]
1.1 ≤ I
E
/I
E
>
inv
≤ 20
If I
E
>
inv
pickup ≥ 2.5 I
En
, the upper limit is 10 I
En
For all defi nite time elements the upper limit for measuring is 10 I
En
.
All residual overcurrent elements can be enabled or disabled by setting ON or OFF the IE> En-
able, IE>> Enable and/or IE>>> Enable parameters inside the Set \ Profi le A(or B) \ Residual
overcurrent-50N/51N \ IE> Element (IE>> Element, IE>>> Element) \ Setpoints menus.
The fi rst overcurrent element can be programmed with defi nite or inverse time
characteristic by setting the IE>Curve parameter (DEFINITE, IEC/BS A,
IEC/BS B, IEC/BS C, ANSI/IEE MI, ANSI/IEE VI, ANSI/IEE EI, EM) available inside the
Set \ Profi le A(or B) \ Residual overcurrent-50N/51N \ IE> Element \ Setpoints menu.
Note 1 The measured residual current I
E
is employed for NA11 protection relays equipped with standard CT sensor inputs
The computed residual current I
EC
(vector sum of the phase currents) is employed for NA11 protection relays equipped with LPCT sensor
inputs
Note 2 When the input value is more than 20 times the set point , the operate time is limited to the value corresponding to 20 times the set point
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t-int-F50N-51N.ai
I
E
I
E
>> I
E
>>>
t
E
>
t
E
>>
t
E
>>>
I
E
>
t
TRIP
General operation time characteristic for the residual overcurrent elements - 50N/51N
t-int-F50N-51N.ai
I
E
I
E
>> I
E
>>>
t
E
>
t
E
>>
t
E
>>>
I
E
>
t
TRIP
TRIP
General operation time characteristic for the residual overcurrent elements - 50N/51N

Thytronic NA11 Specifications

General

Brand	Thytronic
Model	NA11
Category	Relays
Language	English