Figure. 5.2.2 - 70. Example connections for voltage line-to-line measurement.
If only two line-to-line voltages are measured, the third one (U
L31
) is calculated based on the U
L12
and
U
L23
vectors. When measuring line-to-line voltages, the line-to-neutral voltages can also be calculated
as long as the value of U0 is measured and known.
The voltage measurement channel U4 can also be used to measure either the zero sequence voltage
(U0) or the side 2 voltage of the circuit breaker (Synchrocheck). If the 2LL+U3+U4 mode is selected,
the third channel (U3) can be used for this purpose. Please note that U0 can only be measured by
using a single channel.
In the image below is an example of 2LL+U0+SS, that is, two line-to-line measurements with the zero
sequence voltage and voltage from side 2 for Synchrocheck. Since U0 is available, line-to-neutral
voltages can be calculated.
Figure. 5.2.2 - 71. 2LL+U0+SS settings and connections.
The image collection below presents the relay's behavior when nominal voltage is injected into the relay
via secondary test equipment. The measurement mode is 3LN+U4 which means that the relay is
measuring line-to-neutral voltages. The VT scaling has been set to 20 000 : 100 V. The U4 channel
measures the zero sequence voltage which has the same ratio (20 000 : 100 V).
A
AQ
Q-F205
-F205
Instruction manual
Version: 2.04
72
© Arcteq Relays Ltd
IM00013
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