ABB Relion 670 Series Applications Manual page 230

Section 9
Voltage protection
set has opened and not the other (capacitor voltage is connected to input U2). It will also
ensure that a fuse failure alarm is given instead of a Undervoltage or Differential voltage alarm
and/or tripping.
Fuse failure supervision (SDDRFUF) function for voltage transformers. In many application the
voltages of two fuse groups of the same voltage transformer or fuse groups of two separate
voltage transformers measuring the same voltage can be supervised with this function. It will
be an alternative for example, generator units where often two voltage transformers are
supplied for measurement and excitation equipment.
The application to supervise the voltage on two voltage transformers in the generator circuit
is shown in figure 104.
Gen
IEC06000389 V1 EN-US
Figure 104: Supervision of fuses on generator circuit voltage transformers
9.4.3 Setting guidelines
The parameters for the voltage differential function are set via the local HMI or PCM600.
The following settings are done for the voltage differential function.
Operation : Off / On
GlobalBaseSel : Selects the global base value group used by the function to define IBase , UBase
SBase . Note that this function will only use IBase value.
and
BlkDiffAtULow : The setting is to block the function when the voltages in the phases are low.
RFLx : Is the setting of the voltage ratio compensation factor where possible differences
between the voltages is compensated for. The differences can be due to different voltage
transformer ratios, different voltage levels e.g. the voltage measurement inside the capacitor
bank can have a different voltage level but the difference can also e.g. be used by voltage drop
224
To Protection
U1
Ud>
U2
To Excitation
en06000389.vsd
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