50N Instantaneous Earth Fault – Derived
Overview of the Function (50N)
The Instantaneous derived earth fault protection is used to provide:
•
Short-circuit detection in electrical equipment
•
High-speed protection where appropriate to its location in the power system network and/or network
impedances
•
Backup or emergency protection in addition to other protection functions or devices
•
Coordinated operation with other devices using time graded settings
Structure of the Function (50N)
The instantaneous earth fault protection function element has group-dependent settings. These settings can
be different in each settings group – group numbers (Gn) 1 and 2.
The function monitors the primary system earth current by calculating the sum of the 3-phase CT inputs for
example CT1/2/3.
The basic instantaneous derived earth fault function (50N) is characterized by the following:
•
Current measurement is based on the fundamental current.
•
Elements operate with a Definite Time Lag (DTL) characteristic.
•
LED operations are provided for earth fault. A general pickup and 50N-n output are also provided.
Logic of the Function (50N-n)
[lo_7sr46_50N_TimeDelayedDerivedEFFn, 1, en_US]
Figure 3-2
Logic Diagram of the Instantaneous Earth Fault Protection - Derived (50N)
Application and Settings Notes
Gn 50N-n Element
Default setting: Disabled
3.3
Functions
3.3 50N Instantaneous Earth Fault – Derived
Reyrolle, 7SR46 Device, Manual 41
C53000-G7040-C103-1, Edition 10.2022
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