ABB 615 series Technical Manual page 436

Section 4
Protection functions
430
Neutral
No load
Full load
Normal operation
V
3H_N
Neutral
Fault at neutral
V
3H_N
Neutral
No load
Full load
Fault at terminal
V
3H_N
GUID-B85C3CE6-129D-4B09-8B77-2FE59D9DA1B9 V1 EN
Figure 207: Typical example of the third-harmonic voltage measured at the generator
neutral and terminals under different conditions
The operating equation of the protection is described in the following equation.
V V Beta
+ −
3 H T _ 3 H N _
GUID-50A69B54-0D20-45BE-92BB-DE939C62A1C5 V1 EN
The third harmonic voltages
parts. is approximately in the opposite direction to that of the
V
3H T _
actual no-fault angle between those two phasors depends on the type of generator
V
3H_T
Full load
No load
Terminal
V
3H_T
Full load
No load
Terminal
V
3H_T
Terminal
V
0
⋅ =
3 H N _
and are the phasor with its real and imaginary
V V
3H T 3H N
_ _
1MAC059074-MB A
(Equation 50)
, however the
V
3H N _
615 series ANSI
Technical Manual