Functions
2.11 Undervoltage and Overvoltage Protection (optional)
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
167
If the voltage transformers are located on the line side, the measuring voltages will be missing when the line is
disconnected. To avoid that the undervoltage levels in these cases are or remain picked up, the current criterion
CURR.SUP.Uphph< (address 3768) is switched ON. With busbar side voltage transformers it can be switched
OFF. However, if the busbar is dead, the undervoltage protection will pick up and expire and then remain in a
picked-up state. It must therefore be ensured in such cases that the protection is blocked by a binary input.
Undervoltage positive sequence system U
1
The positive sequence undervoltage stages can be used instead of or in addition to previously mentioned un-
dervoltage stages. Depending on your choice, set address 3771 U1<(<) to ON, OFF, Alarm Only or
U<Alarm U<<Trip.
Basically, the same considerations apply as for the other undervoltage stages. Especially in case of stability
problems, the positive sequence system is advantageous, since the positive sequence system is relevant for
the limit of the stable energy transmission.
To achieve the two-stage condition, the U1< stage (address 3772) is combined with a greater time delay T U1<
(address 3773), and the U1<< stage (address 3774) with a shorter time delay T U1<< (address 3775).
Note that the positive sequence system is calculated according to its defining equation
U
1
=
1
/
3
·|U
L1
+a·U
L2
+a
2
·U
L3
|. For symmetrical voltages this is equivalent to a phase-to-earth voltage.
The dropout to pickup ratio U1<(<) RESET can be set in address 3779. This parameter can only be altered
in DIGSI at Display Additional Settings.
If the voltage transformers are located on the line side, the measuring voltages will be missing when the line is
disconnected. To avoid that the undervoltage levels in these cases are or remain picked up, the current criterion
CURR.SUP.U1< (address 3778) is switched ON. With busbar side voltage transformers it can be switched OFF.
However, if the busbar is dead, the undervoltage protection will pick up and expire and then remain in a picked-
up state. It must therefore be ensured in such cases that the protection is blocked by a binary input.
2.11.4 Settings
Addresses which have an appended "A" can only be changed with DIGSI, under Additional Settings.
Addr. Parameter Setting Options Default Setting Comments
3701 Uph-e>(>) OFF
Alarm Only
ON
U>Alarm U>>Trip
OFF Operating mode Uph-e overvolt-
age prot.
3702 Uph-e> 1.0 .. 170.0 V; ∞ 85.0 V Uph-e> Pickup
3703 T Uph-e> 0.00 .. 100.00 sec; ∞ 2.00 sec T Uph-e> Time Delay
3704 Uph-e>> 1.0 .. 170.0 V; ∞ 100.0 V Uph-e>> Pickup
3705 T Uph-e>> 0.00 .. 100.00 sec; ∞ 1.00 sec T Uph-e>> Time Delay
3709A Uph-e>(>) RESET 0.30 .. 0.99 0.98 Uph-e>(>) Reset ratio
3711 Uph-ph>(>) OFF
Alarm Only
ON
U>Alarm U>>Trip
OFF Operating mode Uph-ph overvolt-
age prot.
3712 Uph-ph> 2.0 .. 220.0 V; ∞ 150.0 V Uph-ph> Pickup
3713 T Uph-ph> 0.00 .. 100.00 sec; ∞ 2.00 sec T Uph-ph> Time Delay
3714 Uph-ph>> 2.0 .. 220.0 V; ∞ 175.0 V Uph-ph>> Pickup
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