Voltage Transformer Requirements; Sntp Server Requirements - ABB RELION 650 Series Applications Manual

Section 18
Requirements
18.2

Voltage transformer requirements

The performance of a protection function will depend on the quality of the measured input
signal. Transients caused by capacitive voltage transformers (CVTs) can affect some
protection functions.
Magnetic or capacitive voltage transformers can be used.
The capacitive voltage transformers (CVTs) should fulfill the requirements according to the IEC
61869-5 standard regarding ferro-resonance and transients. The ferro-resonance
requirements of the CVTs are specified in chapter 6.502 of the standard.
The transient responses for three different standard transient response classes, T1, T2 and T3
are specified in chapter 6.503 of the standard. CVTs according to all classes can be used.
The protection IED has effective filters for these transients, which gives secure and correct
operation with CVTs.
18.3

SNTP server requirements

The SNTP server to be used is connected to the local network, that is not more than 4-5
switches or routers away from the IED. The SNTP server is dedicated for its task, or at least
equipped with a real-time operating system, that is not a PC with SNTP server software. The
SNTP server should be stable, that is, either synchronized from a stable source like GPS, or
local without synchronization. Using a local SNTP server without synchronization as primary or
secondary server in a redundant configuration is not recommended.
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