Siemens SIPROTEC 7SD610 Manual page 165

In addition, the compounding feature needs the line data which have been set in the General Protection
Data (Power System Data 2) (Section 2.1.4.1): Address 1111 x', address 1112 c' and address 1113
Line Length, as well as address 1105 Line Angle. These data are vital for a correct compounding calcu-
lation. If the values provided here do not correspond to real conditions, the compounding may calculate an ex-
cessively high voltage at the remote end causing the protection to pick up immediately as soon as the mea-
sured values are applied. In this case, the pickup state can only be reset by switching off the measuring voltage.
Compounding can be switched ON or OFF separately for each of the U1 stages: for the U1> stage at address
3736 U1> Compound and for the U1>> stage at address 3737 U1>> Compound.
The dropout to pickup ratio (address 3739 U1>(>) RESET) is set as high as possible with regard to the de-
tection of even small steady-state overvoltages. This parameter can only be altered in DIGSI at Display Addi-
tional Settings.
Overvoltage negative sequence system U
The negative sequence voltage stages detect asymmetrical voltages. If such voltages should cause tripping,
set address 3741 U2>(>) to ON. Or you can set address 3741 U2>(>) to Alarm Only. In this case the con-
dition will be reported but no trip signal will be generated. If only one stage is desired to generate a trip com-
mand, choose the setting U>Alarm U>>Trip. With this setting a trip command is output by the 2nd stage only.
If negative sequence voltage protection is not required, set this parameter to OFF.
This protection function also has two stages, one being U2> (address 3742) with a greater time delay T U2>
(address 3743) for steady-state asymmetrical voltages and the other being U2>> (address 3744) with a short
delay time T U2>> (address 3745) for high asymmetrical voltages.
Note that the negative sequence system is calculated according to its defining equation
U = ·|U + a
1
/
2 L1
3
phase-to-earth voltage value.
The dropout to pickup ratio U2>(>) RESET can be set in address 3749. This parameter can only be altered
in DIGSI at Display Additional Settings.
Overvoltage zero-sequence system
The zero-sequence voltage stages can be switched ON or OFF in address 3721 3U0>(>) (or Ux). They can
also be set to Alarm Only, i.e. these stages operate and send alarms but do not generate any trip commands.
If a trip command of the 2nd stage is still desired, the setting must be U>Alarm U>>Trip. This protection func-
tion can be used for any other single-phase voltage which is connected to the fourth voltage measurement input
U . Also refer to Section 2.1.2.1 and see margin heading „Voltage Transformer Connection".
4
This protection function also has two stages. The settings of the voltage threshold and the timer values depend
on the type of application. Therefore, no general guidelines can be established. The 3U0> stage (address
3722) is usually set with a high sensitivity and a longer delay time T 3U0> (address 3723). The 3U0>> stage
(address 3724) and its delay time T 3U0>> (address 3725) enables a second stage to be implemented with
less sensitivity and a shorter delay time.
Similar considerations apply if this voltage stage is used for a different voltage at the measuring input U
The zero-voltage stages feature a special time stabilisation due to repeated measurements allowing them to
be set rather sensitive. This stabilisation can be disabled in address 3728 3U0>(>) Stabil. if a shorter
pickup time is required. This parameter can only be altered in DIGSI at Display Additional Settings. Please
consider that sensitive settings combined with short pickup times are not recommended.
The dropout to pickup ratio 3U0>(>) RESET can be set in address 3729. This parameter can only be altered
in DIGSI at Display Additional Settings.
SIPROTEC, 7SD610, Manual
C53000-G1176-C145-6, Release date 02.2011
2
2
·U + a·U |. For symmetrical voltages and two swapped phases this is equivalent to the
L2 L3
2.11 Undervoltage and Overvoltage Protection (optional)
Functions
.
4
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