Functions
2.40 DC Voltage/Current Protection (ANSI 59NDC/51NDC)
SIPROTEC, 7UM62, Manual
C53000-G1176-C149-7, Release date 03.2010
272
Earth Fault Detection in the Startup Converter
If an earth fault occurs in the startup converter circuit, a current flows through all earthed parts of the system
because of the DC voltage. As earthing and neutral transformers have a lower ohmic resistance than voltage
transformers, the thermal load is the highest on them.
The DC current is converted into a voltage in a shunt, and fed via a shunt converter to the measuring transducer
of the device.
Shunt converters can be measuring transducers such as the 7KG6131. For short distances between the shunt
converter and the protective device, a voltage input may be used. For longer distances, use the version with
current input (-20 to 20 mA or 4 to 20 mA).
Figure 2-126 DC Voltage Protection for Detecting an Earth Fault in the Startup Converter
Figure 2-127 Logic Diagram of the DC Voltage Protection
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