ABB PrimeGear ZX0 Product Manual page 44

44 P rimeGe ar Z X0 P R O D U C T M A N U A L
Earthing of open delta windings
If the open delta windings of the voltage
transformers are damped with a resistor, the
windings connected in an open delta are to be
earthed at one point. The circuit can be earthed.
• In the low voltage compartment (Fig.2.3.5.1.3)
or.
• On the terminal block of a voltage transformer
(Fig.2.3.5.1.4).
Perform measurements to ascertain which earthing
method applies to your system.
—
Fig. 2.3.5.1.3 Earthing
of the circuit in the low
voltage compartment
—
Fig. 2.3.5.1.4 Earthing
the circuit on the
terminal board of a
transformer
—
Fig. 2.3.5.1.3
—
Fig. 2.3.5.1.3
dn
Do not earth here!
Without earthing on
terminal "dn"
-T15L1
da
-F
dn
Do not earth here!
Without earthing
on terminal "dn"
-T15L1
da
Earth here!
With earthing screw
-F
on terminal "dn"
Remove the earthing wire of the open delta
windings from the terminal boards of the
voltage transformers in accordance with
the circuit diagrams (Fig.2.3.5.1.5) or
earth the open delta windings using the
earthing wire (Fig.2.3.5.1.6).
Earth the circuit at one point only.
Checking the wiring
Finally, check the earthing system of the
voltage transformer wiring in accordance
with table 2.3.5.1.1.
dn dn
-T15L2 -T15L3
da da
-R
dn dn
-T15L2 -T15L3
da da
-R
Earthing in the low
voltage compartment