Megger frax 101 - Page 77

73
Appendices
© 2011 Megger Sweden AB
stabilizing windings that are earthed at one corner in service, the earth shall be removed if
possible without removing liquid or gas. Always make notes about actual set-up used in the
notes section of nameplate
Zig-zag connected windings shall be measured as star windings with a neutral connection (if
accessible).
Phase shifting transformers: The standard measurement shall be from input terminal to
output terminal on each phase and from the neutral of the shunt winding to the output
terminal on each phase, each on neutral tap and on each extreme tap, a total of 18
measurements. If the phase shifting transformer is of the two core type that has external
interconnections that can be removed on site then it shall be treated as two separate
transformers.
Series reactors shall be measured from input terminal to output terminal on each phase, a
total of three measurements for a three-phase reactor. Shunt reactors shall be treated as a star
winding on a transformer, a total of three measurements for a three-phase reactor without
taps and six for a reactor with taps.
Sample Connections:
IEC and ANSI/IEEE
Alternative ANSI/IEEE
End-to-End Open
Open Circuit Self Admittance (OC)
End-to-End Short-Circuit
Short Circuit Self Admittance (SC)
Capacitive Inter-Winding (CIW)
Inter-Winding (IW)
Inductive Inter-Winding (IIW)
Transfer Admittance (TA)
IEC and ANSI/IEEE
Example IEC
Example ANSI/IEEE
End-to-End Open
1u-1n [open]
H1-H0 [open]
End-to-End Short-Circuit
1u-1n [short]
H1-H0 [short]
Capacitive Inter-Winding (CIW)
1u-2u [CIW]
H1-X1 [IW]
Inductive Inter-Winding (IIW)
1u-2u [IIW, GND 1n, 2n]
H1-X1 [TA, GND H0,X0]