Page 715 - Industrial Power Engineering and Applications Handbook

Temporary overvoltages and system grounding 201675
Arc suppression coil or ground fault neutralizer I, = required level of the ground fault current in
Amperes
To substantially offset the capacitive current by the power
frequency inductor current
Grounding of generators
(i) When all the machines are inclividiially grounded
1- = inductor coil inductance in henry
= ground capacitance per phase in farad and
I' = system fi-eclucncy in Hz
u = p.u. voltage of generator
s;' =positive phase sequence ~.LI. (sub transient) rcaclance
Ground fault factor x2 = negative phase sequence p.u. rexIance
(ii) When only one machine is grounded a1 ;I time

(20.8)
I/, = highest voltage to ground (r.m.s)

Selecting a ground fault protection scheme .q, = zero phase sequence p.u. reactatice
/I = no. of machines operating in parallcl
z= \', Q (20.6)
II 1000 kVA Further reading
kVA = rated capacity of the supply source
C I = system rated line voltage in volts
I, = system rated full load line current in Amperes
/I = unit of /,
Z1 impedance ofthe grounded neutral circuit in Ohms
=