22
6.6 Synchronization sensor
A resistive voltage divider must be connected to the unit in
order to transmit a correct synchronization voltage signal to the
control unit. The voltage sensor must be installed upstream of
the DS1 switch and connected to phase R.
The resistive divider is used for its linearity characteristics (the
output voltage is directly proportional to the input voltage).
Figure 17. Voltage divider principle
The following characteristics are required:
Highest voltage for equipment
24
kV
Rated power frequency test voltage
50
kV
Rated lightning impulse test voltage
125
kV
Rated primary voltage
22/
√
3
kV
The standard model is the KEVA sensor by ABB.
The voltage reduction ratio is 1:10000.
You are strongly advised to use ABB’s Keva sensor. This was
the sensor used for
testing DS1. If a different sensor is used,
the voltage output must not exceed 1.2 Vpp
.
Figure 18. KEVA 24 A3 voltage divider
Wiring of the Keva sensor.
If there is an inrush reactor in the circuit,
make sure that the Keva sensor is wired
directly to the input terminal of DS1, after the
inrush reactor itself.
Install the voltage sensor with a clean layout in the compart-
ment. Comply with the required insulation clearance, the shape
of the connections (rounded) and use screws with round
shapes.
Make sure that the GROUND of the sensor is effective. Take
care of the paint in the compartment, since it can produce in-
sulation and compromise sensor grounding. The 4 holes at the
base of the sensor provide the grounding function. Remove the
paint or add an additional cord in at least one of the holes in
the compartment.
IMPORTANT
Install the voltage sensor by connecting it
to phase R upstream. All other connections
are forbidden. Switching timing is built into
the control system program.
Make sure that the layout of the low voltage
output of the sensor is clean. Keep it as
far as possible from the live bus bars and
use all the available metal ducts. If none of
the ducts is available, install an additional
duct (always respecting the insulation
clearance from the bus bars. Even if the
sensor cable is shielded is always a good
rule to provide proper protection for the LV
equipment.
HV input to be connected on the
upstream voltage bus bar
Low Voltage output
Connector RJ-45
Provided
by
Northeast
Power
Systems,
Inc.
(NEPSI)
