Thytronic NG10 User Manual

FUNCTION CHARACTERISTICS
46
NG10 - Manual - 04 - 2022
Residual overcurrent / High impedance restricted ground fault - 50N/51N-87NHIZ
Preface
The use of either depends solely on the protection method of connecting its residual current input to
measuring CT. If used as a differential protection of high-impedance restricted earth, outside of the
relay and in series to the amperometric current residual a stabilization resistor must be provided; if
required, an externally a nonlinear METROSIL resistor must be provided for overvoltages limitation
in the event of a fault inside the zone of restricted earth fault differential protection. When used
as high-impedance restricted differential protection, the CTs of the two sides must have the same
transformation ratio.
Three operation thresholds, independently adjustable with adjustable delay.
The first one may be programmed with definite or inverse time according the IEC and ANSI/IEEE
standard, as well as with EM curve.
The second and third thresholds with independent time.
For each threshold a reset time can be set useful to reduce the clearing time for intermittent faults.
The first threshold trip may be inhibited by start of the second and/or third threshold.
Similarly the second threshold trip may be inhibited by start of the third threshold.
Operation and settings
The residual fundamental frequency current is compared with the setting values (I
E
>, I
E
>>, I
E
>>>);
current above the associated pickup value is detected and a start is issued. After expiry of the as-
sociated operate time (t
E
>, t
E
>>, t
E
>>> ), a trip command is issued; if instead the current drops below
the threshold, the element is restored.
The first threshold (I
E
> for IE1 input) may be programmed with definite 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
t
E
>
inv
: operate time setting
I
E
>: threshold setting
For all inverse time characteristics, following data applies:
• Asymptotic reference value (minimum pickup value) 1.1I
E
>
• Minimum operate time: 0.1 s
• Range where the equation is valid:
[1]
1.1 ≤ I
E
/I
E
>
inv
≤ 20; if I
E
>
inv
pickup ≥ 0.6 I
En
, the upper limit is
12 I
En
For all definite time elements the upper limit for measuring is 12 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 \ Profile A(or B) \ Residual
overcurrent or high impedance differential restricted earth fault 50N/51N - 87NHIZ \ IE> Element
(IE>> Element, IE>>> Element) \ Setpoints menu.
The first element can be programmed with definite 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 \ Profile A(or B) \ Residual overcurrent or high im-
pedance differential restricted earth fault 50N/51N - 87NHIZ \ IE> Element \ Setpoints menu
The trip of IE> element may be inhibited by the start of the second and/or third element (IE>>,
IE>>>) by setting ON the Disable IE> by start IE>>, Disable IE> by start IE>>> (IE>disbyIE>>,
IE>disbyIE>>>) parameters available inside the Set \ Profile A(or B) \ Residual overcurrent or high
impedance differential restricted earth fault 50N/51N - 87NHIZ \ IE>> Element (IE>>> Element) \ Set-
points menu.
Note 1 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
I
E
I
E
>> I
E
>>>
t
E
>
t
E
>>
t
E
>>>
I
E
>
t
General operation time characteristic for the measured residual overcurrent elements - 50N/51N
TRIP

Thytronic NG10 Specifications

General

Brand	Thytronic
Model	NG10
Category	Protection Device
Language	English