Functions
2.8 Undervoltage and Overvoltage Protection 27/59 (Optional)
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
125
Overvoltage Phase-to-Ground
The phase voltage elements can be switched ON or OFF in address 3701 59-Vph-g Mode. In addition to this,
you can set Alarm Only, i.e. these elements operate and send alarms but do not generate any trip command.
The setting V>Alarm V>>Trip creates in addition also a trip command only for the 59-2 element (V>>).
The settings of the voltage threshold and the timer values depend on the type of application. To detect steady-
state overvoltages on long lines carrying no load, set the 59-1-Vph PICKUP element (address 3702) to at
least 5 % above the maximum stationary phase-to-ground voltage expected during operation. Additionally, a
high dropout to pickup ratio is required (address 3709 59-Vph RESET = presetting). This parameter can only
be set in DIGSI at Display Additional Settings. The time delay 59-1-Vph DELAY (address 3703) should be
a few seconds so that overvoltages with short duration do not cause tripping.
The 59-2 phase (V
ph
>>) element (address 3704) is provided for high overvoltages with short duration. Here an
adequately high pickup value is set, e.g. the 1
1
/
2
-fold of the nominal phase-to-ground voltage. 0.1 s to 0.2 s are
then sufficient for the time delay 59-2-Vph DELAY (address 3705).
Overvoltage Phase-to-Phase
Basically, the same considerations apply as for the phase undervoltage elements. These elements may be
used instead of the phase voltage elements or be used additionally.. Accordingly set address 3711 59-Vph-
ph Mode to ON, OFF, Alarm Only or V>Alarm V>>Trip.
As phase–to–phase voltages are monitored, the phase–to–phase values are used for the settings 59-1-Vpp
PICKUP (address 3712) and 59-2-Vpp PICKUP (address 3714).
For the time delays 59-1-Vpp DELAY (address 3713) and 59-2-Vpp DELAY (address 3715) the same con-
siderations apply as above. The same is true for the dropout ratios (address 3719 59-Vpp RESET). The latter
setting can only be altered in DIGSI at Display Additional Settings.
Overvoltage Positive Sequence System V
1
The positive sequence voltage elements can be used instead of or in addition to previously mentioned over-
voltage elements. Accordingly set address 3731 59-V1 Mode to ON, OFF, Alarm Only or V>Alarm
V>>Trip.
For symmetrical voltages an increase of the positive sequence system corresponds to a logical AND combina-
tion of the phase voltages. These elements are particularly suited to the detection of steady-state overvoltages
on long, weak-loaded transmission lines (Ferranti effect). Here too, the 59-1-V1 PICKUP element (address
3732) with a longer time delay 59-1-V1 DELAY (address 3733) is used for the detection of steady-state ov-
ervoltages (some seconds), the 59-2-V1 PICKUP element (address 3734) with the short time delay 59-2-
V1 DELAY (address 3735) is used for the detection of high overvoltages that may jeopardize insulation.
Please note that the positive sequence system is established according to its defining equation
V
1
=
1
/
3
·|V
A
+a·V
B
+a
2
·V
C
|. For symmetrical voltages the amplitude equivalent to a phase-to-ground voltage.
The dropout to pickup ratio (address 3739 59-V1 RESET) is set as high as possible with regard to the detec-
tion of even small steady-state overvoltages. This parameter can only be set in DIGSI at Display Additional
Settings.
Overvoltage Negative Sequence System V
2
The negative sequence voltage elements detect asymmetrical voltages. If it is desired that such voltages cause
tripping, set address 3741 59-V2 Mode to ON. To only signal such states, set address 3741 59-V2 Mode to
Alarm Only. If only one element is desired to generate a trip command, choose the setting V>Alarm
V>>Trip. With this setting a trip command is output by the 2nd element only. If negative sequence voltage
protection is not required, set this parameter to OFF.
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