Directional Negative-Sequence Protection
Overview of Functions
The function Directional negative-sequence protection with current-independent time delay (ANSI 46)
serves as the backup short-circuit protection for unbalanced faults.
With the negative-sequence system, various supervision and protection tasks can be realized, for example:
•
Recording of 1 or 2-phase short circuits in the system with a higher sensitivity than in classic overcurrent
protection. The pickup value can be set under the rated object current.
•
Recording of phase conductor interruptions in the primary system and in the current-transformer secon-
dary circuits
•
Location of short circuits or reversals in the connections to the current transformers
•
Indication of unbalanced states in the energy system
•
Protection of electrical machines following unbalanced loads that are caused by unbalanced voltages or
conductor interruptions (for example, through a defective fuse)
Structure of the Function
The Directional negative-sequence protection with definite time delay function can be used in protection
function groups with 3-phase current and voltage measurement.
The function comes factory-set with 1 stage. A maximum of 6 tripping stages can be operated simultaneously
in the function.
[dwnspdir-271112-01.tif, 1, en_US]
Figure 6-156 Structure/Embedding of the Function
If the device is equipped with the Inrush-current detection function, the tripping stages can be stabilized
against tripping due to transformer-inrush currents.
Function Description
Stage Control
The following figure shows a stage control. It is available separately for each stage.
6.18
6.18.1
6.18.2
6.18.3
Protection and Automation Functions
6.18 Directional Negative-Sequence Protection
642 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
To Next Page
Loading...
