Setting Notes - Siemens 7SK80 Manual

2.5.4

Setting Notes

General
Voltage protection is only effective and accessible if address 150 27/59 is set to Enabled during configuration
of protection functions. If this function is not required, then Disabled is set.
The voltage to be evaluated is selected in Power System Data 1 (see Chapter 2.5, Table 2-7).
Overvoltage protection can be turned ON or OFF, or set to Alarm Only at address 5001 FCT 59.
Undervoltage protection can be turned ON or OFF or set to Alarm Only at address 5101 FCT 27.
With the protection function ON, tripping, the clearing of a fault and fault recording are initiated when the thresh-
olds are exceeded and the set time delays have expired.
With setting Alarm Only no trip command is given, no fault is recorded and no immediate fault annunciation
is shown on the display.
Overvoltage Protection with Phase-to-phase or Phase-to-Ground Voltages
The largest of the applied voltages is evaluated for the phase-to-phase or phase-to-Ground overvoltage pro-
tection.
The threshold values are set in the value to be evaluated (see Chapter 2.5, Table 2-7).
The overvoltage protection has two elements. The pickup value of the lower threshold (address 5002 or 5003,
59-1 PICKUP, depending on the phase-to-Ground or the phase-to-phase voltages, can be assigned a longer
time delay (address 5004, 59-1 DELAY) and the upper threshold Element (address 5005 or 5006, 59-2
PICKUP) a shorter (address 5007, 59-2 DELAY) time delay. There are no specific procedures on how the
pickup values are set. However, as the function is mainly used to prevent high insulation damage to system
components and users, the threshold value 5002 , 5003 59-1 PICKUP lies generally between 110 % and
115 % of the nominal voltage and setting value 5005 , 5006 59-2 PICKUP at approximately 130 %.
The time delays of the overvoltage elements are entered at addresses 5004 59-1 DELAY and 5007 59-2
DELAY, and should be selected in such manner that they make allowance for brief voltage peaks that are gen-
erated during switching operations and also enable clearance of stationary overvoltages in due time.
The choice between phase-to-Ground and phase-to-phase voltage allows voltage asymmetries (e.g. caused
by a ground fault) to be taken into account (phase-to-Ground) or to remain unconsidered (phase-to-phase)
during evaluation.
Overvoltage Protection - Positive Sequence System V1
In a three-phase voltage transformer connection the positive sequence system can be evaluated for the over-
voltage protection by means of configuring parameter 614 OP. QUANTITY 59 to V1. In this case, the threshold
values of the overvoltage protection must be set in parameters 5019 59-1 PICKUP V1 or 5020 59-2
PICKUP V1.
Overvoltage Protection - Negative Sequence System V2
In a three-phase transformer connection, parameter 614 OP. QUANTITY 59 can determine that the negative
sequence system V2 can be evaluated as a measured value for the overvoltage protection. The negative se-
quence system detects voltage unbalance and can be used for the stabilization of the time overcurrent protec-
tion. In backup protection of transformers or generators, the fault currents lie, in some cases, only slightly above
the load currents. In order to obtain a pickup threshold of the time overcurrent protection that is as sensitive as
possible, its stabilization via the voltage protection is necessary to avoid false tripping.
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
Functions
2.5 Voltage Protection 27, 59
115