Directional Negative-Sequence Protection; Overview Of Functions; Structure Of The Function; Function Description - Siemens 7SJ82 Manual

Protection and Automation Functions

6.18 Directional Negative-Sequence Protection

6.18 Directional Negative-Sequence Protection

Overview of Functions

6.18.1
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

6.18.2
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.
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Figure 6-156
If the device is equipped with the Inrush-current detection function, the tripping stages can be stabilized
against tripping due to transformer-inrush currents.
6.18.3

Function Description

Stage Control
The following figure shows a stage control. It is available separately for each stage.
642
Structure/Embedding of the Function
SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017