Siemens SIPROTEC 4 Manual page 129

Dropout Threshold of the Overvoltage Protection
The dropout thresholds of the 59-1 element and the 59-2 element can be configured via the dropout ratio r =
V /V at addresses 5017 59-1 DOUT RATIO or 5018 59-2 DOUT RATIO. The following marginal
Dropout Pickup
condition applies to r:
r · (configured pickup threshold) ≤ 150 V with connection of phase-to-phase voltages and phase-to-ground
voltages or
r · (configured pickup threshold) ≤ 260 V with calculation of the measured values from the connected voltages
(e.g. phase-to-phase voltages calculated from the connected phase-to-ground voltages).
The minimum hysteresis is 0.6 V.
Undervoltage Protection - Positive Sequence System V1
The positive sequence component (V1) can be evaluated for the undervoltage protection. Especially in case of
stability problems, their acquisition is advantageous because the positive sequence system is relevant for the
limit of the stable energy transmission. Concerning the pickup values there are no specific notes on how to set
them. However, because the undervoltage protection function is primarily intended to protect induction
machines from voltage dips and to prevent stability problems, the pickup values will usually be between 60 %
and 85 % of the nominal voltage.
The threshold value is multiplied as positive sequence voltage and set to √3, thus realizing the reference to the
nominal voltage.
Undervoltage protection comprises two elements. The pickup value of the lower threshold is set at address
5110 or 5111, 27-2 PICKUP (depending on the voltage transformer connection, phase-to-ground or phase-
to-phase), while time delay is set at address 5112, 27-2 DELAY (short time delay). The pickup value of the
upper element is set at address 5102 or 5103, 27-1 PICKUP, while the time delay is set at address 5106,
27-1 DELAY (a somewhat longer time delay). Setting these elements in this way allows the undervoltage
protection function to closely follow the stability behavior of the system.
The time settings should be selected such that tripping occurs in response to voltage dips that lead to unstable
operating conditions. On the other hand, the time delay should be long enough to avoid tripping on short-
term voltage dips.
Undervoltage Protection with Phase-to-phase or Phase-to-ground Voltages
In parameter 615 OP. QUANTITY 27 you can determine for undervoltage protection in a three-phase
connection that instead of the positive-sequence system V1, the smallest of the phase-to-phase voltages
Vphph or the smallest phase-to-ground voltage Vph-n is configured as a measured quantity. The threshold
values are set in the quantity to be evaluated (see Section
Undervoltage protection comprises two elements. The pickup value of the lower threshold is set at address
5110 or 5111, 27-2 PICKUP (depending on the voltage transformer connection, phase-to-ground or
phaseto- phase), while time delay is set at address 5112, 27-2 DELAY (short time delay). The pickup value of
the upper element is set at address 5102 or 5103, 27-1 PICKUP, while the time delay is set at address 5106,
27-1 DELAY (a somewhat longer time delay). Setting these elements in this way allows the undervoltage
protection function to closely follow the stability behavior of the system.
The time settings should be selected such that tripping occurs in response to voltage dips that lead to unstable
operating conditions. On the other hand, the time delay should be long enough to avoid tripping on short-
term voltage dips.
Dropout Threshold of the Undervoltage Protection
The dropout thresholds of the 59-1 element and the 59-2 element can be parameterized via the dropout ratio
r = V /V
dropout pickup
applies to r:
r · (configured pickup threshold) ≤ 130 V with connection of phase-to-phase voltages and phase-to-ground
voltages) or
r· (configured pickup threshold) ≤ 225 V with calculation of the measured values from the connected voltages
(e.g. calculated phase-to-phase voltages from the connected phase-to-ground voltages).
The minimum hysteresis is 0.6 V.
SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017
(5113 27-1 DOUT RATIO or 5114 27-2 DOUT RATIO). The following marginal condition
2.6 Voltage Protection 27, 59
2.6 Voltage Protection 27, 59,
Functions
Table 2-8).
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