56
DMC3S - Manual - 08 - 2021
—
Residual overvoltage - 59N
Preface
This function has two adjustable thresholds 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 first threshold can be selected with definite or inverse time per IEC
60255-3/BS142.
The trip characteristic for the second threshold is definite time.
Each protection threshold can be enabled or disabled.
The first threshold can be inhibited by the start of the second threshold.
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
measured
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 thresholds
(
U
E
>,
U
E
>>) and violating either threshold starts (START) the threshold and its counter (
t
UE
>,
t
UE
>>).
If the threshold violation persists, when its set trip time expires, the threshold trips (TRIP), otherwise
the threshold is reset.
The first threshold
U
E
> can be set to definite or inverse time with a trip characteristic of the type:
t
=0.5
t
UE
> / [(
U
E
/
U
E
>
inv
) - 1] o
t
=0.5
t
UE
> / [(
U
EC
/
U
E
>
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
E
> and
t
UE
> 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 thresh-
old. 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
UE> Curve
in the menu
Set \ Protections \ Residual overvoltage - 59N \
Threshold UE>
\ Parameters
.
Each protection threshold can be enabled or disabled by setting to
ON
or
OFF
the parameter
UE>
Enable
in the menu
Set \ Protections \ Residual overvoltage - 59N \
Threshold UE>
\ Parameters
and/or
State
in the menu
Set \ Protections \ Residual overvoltage - 59N \
Threshold UE>> \ Definite
time
.
The type of residual voltage measurement (direct or calculated) can be set in the menu
Set \ Protec-
tions \ Residual overvoltage - 59N \
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|
t-int-F59N.ai
UE
UE>>
tUE>
tUE>>
UE>
t
General characteristic of the operating time of the residual overvoltage function (59N)
TRIP
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