ABB Relion 670 Series Applications Manual page 612

Section 25
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
25.2 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.
25.3 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.
25.4 PTP requirements
For PTP to perform properly, the Ethernet equipment that is used needs to be compliant with
IEEE1588. The clocks used must follow the IEEE1588 standard BMC (Best Master Algorithm)
and shall, for instance, not claim class 7 for a longer time than it can guarantee 1us absolute
accuracy.
25.5 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
606
> ×
0.75 (max imum of E
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according to IEC 61869-2. Therefore, the CTs
al
kneeANSI
)
alreq
1MRK 511 401-UEN Rev. K
that is
kneeANSI
normally has a
kneeANSI
can approximately be
kneeANSI
that fulfills the following:
(Equation 206)
GUID-588FCD12-C494-445E-8488-8287B34EFD9A v4
GUID-741CC863-D760-49D6-85B2-AFECA222A8C3 v1
GUID-0A9F36AF-3802-42FE-8970-4662798C19D1 v3
Bay control REC670
Application manual
M11608-3 v5