Voltage Protection 27, 59; Measurement Principle - Siemens SIPROTEC 4 User Manual

2.6

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.
2.6.1

Measurement Principle

Connection/Measured Values
The voltages supplied to the device can be the three phase-to-ground voltages V
phase voltages (V
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
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
the threshold must be set. All voltages are fundamental frequency values.
Table 2-11
Function Connection, three-phase
Parameter 213
Overvoltage
Van, Vbn, Vcn
Van,Vbn,Vcn,VGn
Van,Vbn,Vcn,VSy
Van,Vbn,Vcn,Vx
Vab, Vbc, VGnd
Vab, Vbc, Vx
Undervoltage
Van, Vbn, Vcn
Van,Vbn,Vcn,VGn
Van,Vbn,Vcn,VSy
Van,Vbn,Vcn,Vx
Vab, Vbc, VGnd
Vab, Vbc, Vx
SIPROTEC 4, 7SJ62/64, Manual
C53000-G1140-C207-8, Edition 08.2016
, V ) and the displacement voltage (ground voltage V
A-B B-C
Voltage protection, selectable voltages
Vphph (largest phase-to-phase voltage)
Vph-n (largest phase-toground-voltage)
V1 (positive sequence voltage)
V2 (negative sequence voltage)
Vphph (largest phase-to-phase voltage)
V1 (positive sequence voltage)
V2 (negative sequence voltage)
Vphph (smallest phase-to-phase voltage) Phase-to-phase voltage
Vph-n (smallest phase-to-ground-
voltage)
V1 Positive (positive sequence voltage)
Vphph (smallest phase-to-phase voltage) Phase-to-phase voltage
V1 (positive sequence voltage)
2.26 Protection for Single-phase Voltage Transformer
2.1.3.2 Setting Notes). Furthermore, it is indicated to which value
Selectable voltage
(Parameter 614 / 615
2.6 Voltage Protection 27, 59
, V , V or two phaseto-
A-N B-N C-N
) or, in case of a single-phase
N
Threshold to be set as
Phase-to-phase voltage
phase-ground-voltage
Positive sequence voltage
Negative sequence voltage
Phase-to-phase voltage
Positive sequence voltage
Negative sequence voltage
Leiter-ground-Spannung
Positive sequence voltage·
√3
Positive sequence voltage·
√3
Functions
127