Thytronic DMC3S - Residual Emergency Overcurrent - 51(Eme)

50
DMC3S - Manual - 08 - 2021
— Residual emergency overcurrent - 51(Eme)
Preface
This function has one adjustable threshold with programmable trip time.
The trip characteristic can be selected with definite or inverse time per IEC 60255-3/BS142.
A constant reset time can be set to reduce the time for eliminating intermittent faults (while being no
less than the protection start time).
The threshold can be enabled or disabled; the function is automatically enabled if the voltmetric
measurement chain fails (function 74VT tripped).
Operation and settings
The residual overcurrent protection compares the fundamental component of the residual current
(I
E
) with the set threshold (I
Eeme
>); violating the threshold starts (START) the threshold itself and the
corresponding timer (t
Eeme
>). If the threshold violation persists, when its trip time expires, the thresh-
old trips (TRIP), otherwise the threshold is reset.
The threshold can be set to definite or inverse time with the following characteristic curves:
• IEC 255-3/BS142 type A or SIT, inverse time: t = 0.14 · t
Eeme
>
inv
/ [(I
E
/I
Eeme
>
inv
)
0.02
- 1]
• IEC 255-3/BS142 type B or VIT, very inverse time: t = 13.5 · t
Eeme
>
inv
/ [(I
E
/I
Eeme
>
inv
) - 1]
• IEC 255-3/BS142 type LTI, long time inverse: t = 120 · t
Eeme
>
inv
/ [(I
E
/I
Eeme
>
inv
) - 1]
• IEC 255-3/BS142 type C or EIT, extremely inverse time: t = 80 · t
Eeme
>
inv
/ [(I
E
/I
Eeme
>
inv
)
2
- 1]
Where:
t: operating time
I
Eeme
>: trip threshold
t
Eeme
>
inv
: operating time regulation
The following applies to all inverse time characteristics:
• The minimum trip current is 1.1 times the set threshold (asymptotic reference time).
• The minimum operating time t is 0.1 s.
• The characteristics are defined between 1.1 and 20 times the set threshold;
[1]
if threshodl regula-
tion exceeds 2.5 I
n
, the upper limit of the measurement range is 10 I
En
.
For definite time trip characteristics, the upper limit of the measurement range is 10 I
En
.
The threshold can be enabled or disabled by setting to ON or OFF the parameter IEeme> Ena-
ble in the menu Set \ Protections \ Residual emergency overcurrent - 51N(Eme) \ Threshold IEeme>
\ Parameters.
The first threshold can be set to definite or inverse time with parameter IEeme>Curve (INDIP-
ENDENTE, NIT, VIT, EIT, LIT) in the menu Set \ Portections \ Residual emergency overcur-
rent - 51N(Eme) \ Threshold IEeme> \ Parameters.
In the same way, the first threshold can be inhibited by the start of the second threshold with Deac-
tivation INe> by start INe>> (INe>>disbyIE>>) in the menu Set \ Protections \ Residual emer-
gency overcurrent - 51N(Eme) \ Threshold IEeme> \ Parameters.
A constant reset time can be set for each of the thresholds t
Eeme>RES
.
Shrink time
If the threshold is programmed with definite time characteristic you can set the contracted time by
setting to ON the parameter EnTcIEeme>def and regulating the contracted time (tcIEeme>-
def) and the operating time (tatcIEeme>def).
Once the breaker closes, during the operating time (e.g.: tatcIEeme>def), the value of the trip
time (e.g.: tEeme>def ) is replaced by the contracted time (e.g.: tcIEeme>def ); when the oper-
ating time expires the trip time is reset (e.g.: tEeme>def ).
The related parameters are available in the menu Set \ Protections \ Residual emergency overcur-
rent - 51N(Eeme) \ Threshold IEeme>\ Definite time.
Note 1 For input values greater than 20 times the threshold, the operating time is limited to the value corresponding to 20 times the threshold
IE
tEeme>
IEeme>
t
Trip characteristic of the threshold of the maximum emergency residual current protection -
51N(Eme)
TRIP