open delta transformer
open delta transformer
(OP)
hi
we have vt transformer Y/y/d 33kv/110/110
now d is connected open to detection earth fault true?
the end for open delta is connected to damping resistance
now
1- Why take advantage for using damping resistance?
2- how calculated value damping resistance?
3-when not using damping resistance i mean the end for open delta isn't connected to damping resistance this effect to transformer primary ?
we have vt transformer Y/y/d 33kv/110/110
now d is connected open to detection earth fault true?
the end for open delta is connected to damping resistance
now
1- Why take advantage for using damping resistance?
2- how calculated value damping resistance?
3-when not using damping resistance i mean the end for open delta isn't connected to damping resistance this effect to transformer primary ?






RE: open delta transformer
thread238-87156: Potential transformer open delta measurements
RE: open delta transformer
but can you help me for calculation damping resistance?
RE: open delta transformer
derived from experience, are shown in Table 7.1.
from "Protective Relaying Principles and Applications" by J. Lewis Blackburn and Thomas J. Domin
But maximum primary voltage in this table is only 13.8 [not 33 KV as you need].I think nevertheless 85 ohm 510 w will be ok even for 33 KV/120 V transformer.
The potential transformer manufacturer has to know more.
The required rated power will be P=Vo^2/R
Vo=3*120/sqrt(3)[if 120 V is VT secondary rated voltage.]
RE: open delta transformer
www.basler.com/downloads/pc-59n01.pdf
RE: open delta transformer
The normal secondary voltage during unfaulted conditions on each leg of the delta will be = 110 Volts. During a line to ground fault, secondary voltage on the two unfaulted phases rises to 190.52V (=33,000/173.2)
The maximum broken delta voltage will be:
Vbroken delta = 3 x Vpri L-N /turns ratio = 3(19,052)/173.2 = 330 volts.
Assuming the VT tertiary VA is 600VA, the VT secondary current if delta is closed will be:
CODE
I sec(rating) = -------------
VSEC
200VA
I sec(rating) = ------- = 1.82 amps
110
The loading resistor will be:
CODE
R = --------------- = ------- = 181 ohms
I 1.82
PR = I x V = 1.82 x 330V = 600 W
RE: open delta transformer
sorry dear ratio for transformer (33kv/1.73)/110/1.73
RE: open delta transformer
Cahier technique n° 190 Ferroresonance schneider-electric.com
http:/
VT Guard from ABB is a electronic device
ht
RE: open delta transformer
With a thermal rating of 600VA, your loading resistor will be 105 ohms
PR = (200/110)2 x 105 = 347W, say 400W