Voltage Transformer Requirements; Sntp Server Requirements; Sample Specification Of Communication Requirements For The Protection And Control Terminals In Digital Telecommunication Networks - ABB RELION 650 Series Applications Manual

Section 21
Requirements
A CT according to ANSI/IEEE is also specified by the knee point voltage U
graphically defined from an excitation curve. The knee point voltage U
lower value than the knee-point e.m.f. according to IEC and BS. U
estimated to 75 % of the corresponding E
according to ANSI/IEEE must have a knee point voltage U
V
kneeANSI
EQUATION2101 V2 EN-US
21.2

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.
21.3

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.
21.4 Sample specification of communication requirements
for the protection and control terminals in digital
telecommunication networks
The communication requirements are based on echo timing.
Bit Error Rate (BER) according to ITU-T G.821, G.826 and G.828
•
<10
Bit Error Rate (BER) for high availability of the differential protection
•
<10
•
<10
364
> ×
0.75 (max imum of E
-6
according to the standard for data and voice transfer
-8 -9
-10 during normal operation
-6
during disturbed operation
according to IEC 61869-2. Therefore, the CTs
al
kneeANSI
)
alreq
1MRK 505 363-UEN A
that is
kneeANSI
normally has a
kneeANSI
can approximately be
kneeANSI
that fulfills the following:
(Equation 178)
GUID-588FCD12-C494-445E-8488-8287B34EFD9A v4
GUID-0A9F36AF-3802-42FE-8970-4662798C19D1 v1
Application manual
M11608-3 v5