Voltage Protection 27, 59; Measurement Principle - Siemens 7SC80 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 available each for overvoltage protection and undervoltage protection. The pickup
voltages and time delays can also be set specifically for an element or phase.
Additionally, you can use a 3-element displacement voltage protection. The elements use the measured or
calculated displacement voltage.
Applications
•
Higher voltages often occur, e.g. on long transmission lines under low load conditions.
•
The undervoltage protection function detects voltage dips on transmission lines and prevents inadmis-
sible operating states and a possible loss of stability.

Measurement Principle

2.6.1
Connection/Measured Values
The voltages supplied to the device can be either the three phase-to-ground voltages V
phase-to-phase voltages (V
has been specified during the configuration in parameter 213 VT Connect. 3ph (see Section
2.1.3.2 Setting
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
threshold must be set. All voltages are fundamental frequency values.
The overvoltage protection with negative-sequence voltage is described in Section
Sequence Overvoltage.
Table 2-11
Function Three-phase connec-
(Parameter 213
Overvoltage
Van, Vbn, Vcn
Vab, Vbc, VGnd
Vab, Vbc
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017
, V ), and the displacement voltage (ground voltage V
A-B B-C
Notes).
2.1.3.2 Setting
Voltage Protection, Selectable Voltages
tion
Vphph (largest phase-to-phase voltage)
Vph-n (largest phase-to-ground voltage) Phase-to-ground voltage
V1 (positive sequence voltage)
Vphph selective (phase-specific
phase-tophase voltage)
Vph-n selective (phase-specific
phase-to-ground voltage)
Vphph (largest phase-to-phase voltage)
V1 (positive sequence voltage)
Vphph selective
Notes). Furthermore, it is indicated to which value the
Selectable voltage
(Parameter 613/614
Functions
2.6 Voltage Protection 27, 59
, V , V or two
A-N B-N C-N
). The connection type
N
2.7 47 Negative Phase
Threshold to be set as
Phase-to-phase voltage
Positive sequence voltage
calculated from phase-to-
ground voltage or phase-to-
phase voltage/√3
Phase-specific phase-to-
phase pickup voltage
Phase-specific phase-to-
ground pickup voltage
Phase-to-phase voltage
Positive sequence voltage
Phase-specific phase-to-
phase pickup voltage
187