Siemens 7SC80 Manual page 196

Functions
2.6 Voltage Protection 27, 59
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 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.
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) ≤ 120 V with connection of phase-to-phase voltages and phase-to-ground
voltages) or
r· (configured pickup threshold) ≤ 210 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.
NOTE
i
i
If a setting is selected such that the dropout threshold (= pickup threshold · dropout ratio) results in a
greater value than 120 V/210 V, it will be limited automatically. No error message occurs.
Phase-specific Pickup Voltages Undervoltage Protection
The phase-specific pickup voltages of the two undervoltage protection elements are set at the following
addresses:
27-1 PhA Pickup
27-1 PhB Pickup
27-1 PhC Pickup
27-2 PhA Pickup
27-2 PhB Pickup
27-2 PhC Pickup
The selectable voltage range depends on the type of connection phase-to-phase voltage or phase-to-ground
voltage (parameter 213).
Phase-specific Time Delays Undervoltage Protection
The phase-specific times for tripping delay of the two undervoltage protection elements are set at the
following addresses:
196
(5113 27-1 DOUT RATIO or 5114 27-2 DOUT RATIO). The following marginal condition
Adresse 5130 or 5131
Adresse 5132 or 5133
Adresse 5134 or 5135
Adresse 5136 or 5137
Adresse 5138 or 5139
Adresse 5140 or 5141
2.6 Voltage Protection 27, 59,
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
Table 2-11).