Thytronic DMC3S - Residual Emergency Overvoltage - 59 N(Eme)

58
DMC3S - Manual - 08 - 2021
— Residual emergency overvoltage - 59N(Eme)
Preface
This function has one adjustable threshold with programmable trip time.
Since only the fundamental component of the residual voltage is measured (direct or calculated), the
protection is not sensitive to the components of the third harmonic and its multiples.
The trip characteristic for the threshold can be selected with definite or inverse time per IEC 60255-3/
BS142.
The protection can be enabled or disabled; the function is automatically enabled if the amperometric
measurement chain fails (function 74CT tripped).
Measurement criterion
Two separate measurements of the residual voltage are available:
• Direct.
• Calculated.
In the first case, the protection uses the fundamental component of the residual voltage U
E
meas-
ured at the residual voltage input, while in the second it uses the fundamental component of the
residual voltage U
EC
resulting from the vectorial sum of the phasors of the three phase voltages
measured at the voltmetric phase inputs.
Operation and settings
The protection compares the above residual voltage measurement (U
E
or U
EC
) with the set thresh-
olds (U
Eeme
>) and violating the threshold starts (START) the threshold and its counter (t
UEeme
>). If the
threshold violation persists, when its set trip time expires, the threshold trips (TRIP), otherwise the
threshold is reset.
The threshold U
Eeme
> can be set to definite or inverse time with a trip characteristic of the type:
t=0.5 t
UEeme
> / [(U
E
/U
Eeme
>
inv
) - 1] o
t=0.5 t
UEeme
> / [(U
EC
/U
Eeme
>
inv
) - 1]
where t is the trip time, U
E
and U
EC
are the direct and calculated measurements of the residual volt-
age respectively, and U
Eeme
> and t
UEeme
> are the set threshold and operating time. The set operating
time refers to a voltage of 1.5 times the set threshold. The minimum trip voltage is 1.1 times the set
threshold. The characteristic is defined between 1.1 and 4 times the set threshold.
The minimum operating time t is 0.1 s.
The definite or inverse time characteristic is selected with the parameter UEeme> Curve in the
menu Set \ Protections \ Residual overvoltage - 59N(Eme) \ Threshold UEeme> \ Parameters.
The protection threshold can be enabled or disabled by setting to ON or OFF the parameter
UEme> Enable in the menu Set \ Protections \ Residual overvoltage - 59N(Eme) \ Threshold
UEeme> \ Parameters and/or State in the menu Set \ Protections \ Residual overvoltage - 59N(Eme)
\ Threshold UEeme>> \ Definite time.
The type of residual voltage measurement (direct or calculated) can be set in the menu Set \ Protec-
tions \ Residual overvoltage - 59N(Eme) \ Common configurations, by setting 3Votype59N; the
available settings are UE (direct) and UEC (calculated).
When set to UE (direct measurement), the thresholds are expressed in p.u. U
En
; when set to UEC
(calculated voltage) the thresholds are expressed in p.u. U
ECn
.
UEC=|UL1+UL2+UL3|
UE
tUEeme>
UEeme>
t
General characteristic of the operating time of the maximum emergency residual voltage
function 59N(Eme)
TRIP