Siemens SIPROTEC 4, User Manual

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Voltage Protection 27, 59
Voltage protection has the task to protect electrical equipment against undervoltage and overvoltage. Both
operational states are abnormal as overvoltage may cause for example insulation problems or undervoltage
may cause stability problems.
There are two 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
machines and prevents inadmissible operating states and a possible loss of stability.
Measurement Principle
Connection/Measured Values
The voltages supplied to the device can be the three phase-to-ground voltages V
A-N
, V
B-N
, V
C-N
or two phaseto-
phase voltages (V
A-B
, V
B-C
) and the displacement voltage (ground voltage V
N
) or, in case of a single-phase
connection, any phase-to-ground voltage or phase-to-phase voltage. The devices 7SJ623/624/625/626 and
7SJ64 provide the option to detect three phase-to-ground voltages and additionally the ground voltage. With a
multiple-phase connection, the connection type was specified during configuration of parameter213
VT
Connect. 3ph
.
If there is only one voltage transformer, the device has to be informed of this fact during configuration via
address 240
VT Connect. 1ph
(see also Section 2.26 Protection for Single-phase Voltage Transformer
Connection ).
The following table indicates which voltages can be evaluated by the function. The settings for this are carried
out in the
P.System Data 1
(see Section 2.1.3.2 Setting Notes ). Furthermore, it is indicated to which value
the threshold must be set. All voltages are fundamental frequency values.
Table 2-11 Voltage protection, selectable voltages
Function Connection, three-phase
Parameter 213
Selectable voltage
(Parameter 614 / 615
Threshold to be set as
Overvoltage
Van, Vbn, Vcn
Van,Vbn,Vcn,VGn
Van,Vbn,Vcn,VSy
Van,Vbn,Vcn,Vx
Vphph
(largest phase-to-phase voltage) Phase-to-phase voltage
Vph-n
(largest phase-toground-voltage) phase-ground-voltage
V1
(positive sequence voltage) Positive sequence voltage
V2
(negative sequence voltage) Negative sequence voltage
Vab, Vbc, VGnd
Vab, Vbc, Vx
Vphph
(largest phase-to-phase voltage) Phase-to-phase voltage
V1
(positive sequence voltage) Positive sequence voltage
V2
(negative sequence voltage) Negative sequence voltage
Undervoltage
Van, Vbn, Vcn
Van,Vbn,Vcn,VGn
Van,Vbn,Vcn,VSy
Van,Vbn,Vcn,Vx
Vphph
(smallest phase-to-phase voltage) Phase-to-phase voltage
Vph-n
(smallest phase-to-ground-
voltage)
Leiter-ground-Spannung
V1
Positive (positive sequence voltage) Positive sequence voltage·
√3
Vab, Vbc, VGnd
Vab, Vbc, Vx Vphph
(smallest phase-to-phase voltage) Phase-to-phase voltage
V1
(positive sequence voltage) Positive sequence voltage·
√3
2.6
2.6.1
Functions
2.6 Voltage Protection 27, 59
SIPROTEC 4, 7SJ62/64, Manual 127
C53000-G1140-C207-8, Edition 08.2016