47 Negative Phase Sequence Overvoltage; Description; Setting Notes - Siemens 7SC80 Manual

Functions

2.7 47 Negative Phase Sequence Overvoltage

2.7 47 Negative Phase Sequence Overvoltage
The negative-sequence system overvoltage protection has the function to protect electrical equipment against
overvoltage. It evaluates the negative-sequence voltage.

Description

2.7.1
With a 3-phase voltage transformer connection, the negative-sequence voltage V2 can be evaluated as meas-
urand. The negative-sequence system detects voltage unbalance and can be used to stabilize the definite time
overcurrent protection. In backup protection of transformers or generators, the fault currents are only slightly
higher than the load currents in some cases. To obtain maximum sensitivity of the pickup threshold of the
definite time overcurrent protection, it must be stabilized by the voltage protection to avoid unwanted trip-
ping.
The negative-sequence system overvoltage protection uses phase-to-phase voltages or phase-to-ground
voltages. Depending on the connection type (parameter VT Connect. 3ph = Van, Vbn, Vcn or Vab,
Vbc, VGnd), the voltages are measured or calculated. When set to Vab, Vbc, the function is disabled.
The negative-sequence system overvoltage protection has 2 elements. The pickup threshold and the trip delay
times of the definite time elements V2> and V2>> can be set separately. The negative-sequence system over-
voltage protection is time-graded as a result.
When the negative-sequence voltage exceeds the set threshold, the element picks up. Tripping takes place
after the set delay time has expired. The time delays do not depend on the magnitude of the overvoltage.
The negative-sequence system overvoltage protection works in the frequency range from 25 Hz to 70 Hz.
Outside this range, the function is blocked.
[ueberspg-gegensystem-20130115, 1, en_US]
Figure 2-54

Setting Notes

2.7.2
General
At address 2250 FCT 47NPS, you can switch the negative-sequence system overvoltage protection ON or
OFF.
202
Logic Diagram of Overvoltage Protection with Negative-Sequence Voltage
SIPROTEC Compact, 7SC80, Manual
E50417-G1140-C486-A8, Edition 07.2017