Overcurrent Protection, Ground
Overview of Functions
The Overcurrent protection, ground function (ANSI 50N/51N):
•
Detects short circuits in electrical equipment
•
Can be used as backup overcurrent protection in addition to the main protection
Structure of the Function
The Overcurrent protection, ground function is used in protection function groups. 2 kinds of functions are
available for the 3-phase overcurrent protection:
•
Overcurrent protection, ground – advanced (50N/51N OC-gnd-A)
•
Overcurrent protection, ground – basic (50N/51N OC-gnd-B)
The function type Basic is provided for standard applications. The function type Advanced offers more func-
tionality and is provided for more complex applications.
Both function types are pre-configured by the manufacturer with 2 Definite-time overcurrent protection
stages and with 1 Inverse-time overcurrent protection stage.
In the function type Overcurrent protection, ground – advanced the following stages can be operated
simultaneously:
•
Maximum of 3 stages Definite-time overcurrent protection – advanced
•
1 stage Inverse-time overcurrent protection – advanced
•
1 stage User-defined characteristic curve overcurrent protection
In the function type Overcurrent protection, ground – basic the following stages can be operated simultane-
ously:
•
Maximum of 3 stages Definite-time overcurrent protection – basic
•
1 stage Inverse-time overcurrent protection – basic
The non-preconfigured stages are shown in gray in the following figures. Apart from the tripping delay charac-
teristic, the stages are identical in structure.
The measured-value selection (only advanced stage) is general functionality and has a uniform effect on the
stages (see Figure 6-32 and chapter 6.5.3.1 Description). This ensures that all stages of the function receive
the same measured current value.
The group-indication output logic generates the following group indications of the protection function by the
logical OR of the stage-selective indications:
•
Pickup
•
Operate
6.5
6.5.1
6.5.2
Protection and Automation Functions
6.5 Overcurrent Protection, Ground
378 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
To Next Page
Loading...
