vt guard for ferroresonance
TRANSCRIPT
-
8/19/2019 VT Guard for FerroResonance
1/10
© A B B
s . r . o .
- 1
5 / 1 4 / 2 0 0 7
Insert imagehere
ABB s.r.o.VT Guard
-
8/19/2019 VT Guard for FerroResonance
2/10
© A B B s . r . o .
- 2
5 / 1 4 / 2 0
0 7
Damping resistor
Parallel conection
Lower resistance means betterdamping of resonanceoscillation.
Higher resistance - to providepower safety, when one phase isgrounded.
ResistanceR – 22 Ohm PR-500W
R – 27 Ohm PR-500W
-
8/19/2019 VT Guard for FerroResonance
3/10
© A B B
s . r . o .
- 3
5 / 1 4 / 2 0
0 7
Damping resistor - Conflict
Ferroresonace appears =>low resistance needed
Phase grounded =>high resistance needed
Damping resistor – only a particular solution
N
A
n
a
dn
da
N
A
n
a
dn
da
N
A
n
a
dn
da R1
R
S
T
VT1 VT2 VT3
U0
FDC
R2
1
2
R
-
8/19/2019 VT Guard for FerroResonance
4/10
© A B B
s . r . o .
- 4
5 / 1 4 / 2 0 0 7
Solution is called - VT guard
For damping low resistance cca. 15 OhmFor one phase grounded resistance high >> 200 Ohm
VT Guard - conneted in open delta (with VT’s residual windings)
-
8/19/2019 VT Guard for FerroResonance
5/10
© A B B
s . r . o .
- 5
5 / 1 4 / 2 0 0 7
VT guard basic function
Fig. 1. Oscillating voltage and currentdiagram when ferroresonance appears.
Fig. 2. Experimental demonstrationof the VT guard effectiveness.
-
8/19/2019 VT Guard for FerroResonance
6/10
© A B B
s . r . o .
- 6
5 / 1 4 / 2 0 0 7
VT guard
Size according DIN – You can put it inlow voltage side in switchgear.
-
8/19/2019 VT Guard for FerroResonance
7/10
© A B B
s . r . o .
- 7
5 / 1 4 / 2 0 0 7
VT Guard installation
VT Guard
-
8/19/2019 VT Guard for FerroResonance
8/10
© A B B
s . r . o .
- 8
5 / 1 4 / 2 0 0 7
Comparison: Resistor vs. VT Guard
No significant temperature increaseHigh temperature increase
Reliable ferroresonance security deviceNot reliable (depending onnetwork conditions)
Complex solution
Phase grounded – high resistanceFerroresonace appears – low resistance
Particular solution
Fast dampingSlow damping
Mounted in the low-voltage part on DIN-railMounted in the near of the voltagetransformers in the primary part
VT GuardResistor
-
8/19/2019 VT Guard for FerroResonance
9/10
© A B B
s . r . o .
- 9
5 / 1 4 / 2 0 0 7
VT Guard : features and benefits
Effective ferroresonance dampingdue to low resistance
No thermal hazard to VT (realthermal protection)
Nonsensitive to natural networkasymmetry
Small size (DIN –rail mounted)
Applicable to any type of voltagetransformers equipped with residualwindings
New solution – no competitor
-
8/19/2019 VT Guard for FerroResonance
10/10
© A B B
s . r . o .
- 1 0
5 / 1 4 / 2 0 0 7