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Functions
2.2 Voltage Protection 27, 59
SIPROTEC, 7RW80, Manual
C53000-G1140-C233-1, Release date 10.2010
40
2.2
Voltage Protection 27, 59
Voltage protection has the task to protect electrical equipment against undervoltage and overvoltage. Both op-
erational states are abnormal as overvoltage may cause for example insulation problems or undervoltage may
cause stability problems.
There are three elements each available for overvoltage protection and undervoltage protection.
Applications
• Abnormally high voltages often occur e.g. in low loaded, long distance transmission lines, in islanded
systems when generator voltage regulation fails, or after full load rejection of a generator from the system.
• The undervoltage protection function detects voltage collapses on transmission lines and electrical ma-
chines and prevents inadmissible operating states and a possible loss of stability.
2.2.1
Measurement Principle
Connection / Measured Values
The voltages supplied to the device may correspond to the three phase-to-ground voltages V
A-N
, V
B-N
, V
C-N
or
the two phase-to-phase voltages (V
A-B
, V
B-C
) and the displacement voltage (ground voltageV
N
) or - in the case
of a single-phase connection - any phase-to-ground voltage. The connection type has been specified during
the configuration in parameter
213
VT Connect. 3ph
(see 2.1.3.2).
The following table indicates which voltages can be evaluated by the function. The settings for this are made
in the
P.System Data 1
(see Section 2.1.3.2). Furthermore, it is indicated to which value the threshold must
be set. All voltages are fundamental frequency values.
Table 2-2
Voltage Protection (27, 59), selection of different voltages
The positive and negative sequence voltages stated in the table are calculated from the phase-to-ground volt-
ages.
Function
Connection, three-phase
(parameter 213)
Selectable Voltage
(parameter 614 / 615)
Threshold to be set as
Overvoltage
Van, Vbn, Vcn
Vphph ( Phase-to-phase voltage)
Phase-to-phase voltage
Vph-n ( Phase-ground-voltage)
Phase-to-ground voltage
V1 (positive sequence voltage)
Positive sequence voltage
calculated from phase-to-
ground voltage or phase-to-
phase voltage /
√
3
V2 (negative sequence voltage)
Negative sequence voltage
Vab, Vbc, VGnd
Vab, Vbc
Vab, Vbc, VSyn
Vab, Vbc, Vx
Vphph ( Phase-to-phase voltage)
Phase-to-phase voltage
V1 (positive sequence voltage)
Positive sequence voltage
V2 (negative sequence voltage)
Negative sequence voltage
Vph-g, VSyn
None (direct valuation of the voltage con-
nected to voltage input 1)
direct voltage quantity
Undervoltage
Van, Vbn, Vcn
Vphph ( Phase-to-phase voltage)
Phase-to-phase voltage
Vph-n ( Phase-ground-voltage)
Phase-to-ground voltage
V1 (positive sequence voltage)
Positive sequence voltage·
√
3
Vab, Vbc, VGnd
Vab, Vbc
Vab, Vbc, VSyn
Vab, Vbc, Vx
Vphph ( Phase-to-phase voltage)
Phase-to-phase voltage
V1 (positive sequence voltage)
Positive sequence voltage·
√
3
Vph-g, VSyn
None (direct evaluation of the voltage con-
nected to voltage input 1)
direct voltage quantity