Overcurrent Protection, 1-Phase
Function Overview
The Overcurrent protection, 1-phase function (ANSI 50N/51N):
•
Detects and monitors the current measured in a transformer neutral point grounding
•
Can operate as sensitive tank leakage protection
•
Detects and monitors the circulating current between the neutral points of 2 capacitor banks
•
Switches off high-current faults instantaneously
Structure of the Function
The Overcurrent protection, 1-phase function is used in protection function groups with 1-phase current
measurement. 2 function types are offered:
•
Overcurrent protection, 1-phase – advanced (50N/51N OC-1ph-A)
•
Overcurrent protection, 1-phase – basic (50N/51N OC-1ph-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, 1-phase – advanced the following stages can be operated
simultaneously:
•
Maximum of 3 stages Definite-time overcurrent protection (UMZ)
•
1 stage Inverse-time overcurrent protection (AMZ)
•
1 stage User-defined characteristic curve overcurrent protection
•
1 Fast stage
In the function type Overcurrent protection, 1-phase – basic, the following stages can operate simultane-
ously:
•
Maximum of 3 stages Definite-time overcurrent protection
•
1 stage Inverse-time overcurrent protection
The non-preconfigured stages in Figure 7-121 and Figure 7-122 are shown in gray. Apart from the operate-
delay characteristic curve, the Definite-time overcurrent protection stage, the Inverse-time overcurrent
protection stage, and the User-defined characteristic curve-time overcurrent protection stage are struc-
tured identically.
The Fast stage uses a fast tripping algorithm. It is therefore suited in particular for sensitive ground-fault
detection according to the high-impedance principle.
7.8
7.8.1
7.8.2
Protection and Automation Functions
7.8 Overcurrent Protection, 1-Phase
746 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017
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