Page 986 - Industrial Power Engineering and Applications Handbook

An isolated phase bus system 31/931
HV side - Y B
R

400 kV (y)
Generator transformer (GT)
(arrangement illustrates when
3,l-9 transformers are used)
LV side (D )-

IPB bends and
inter connections
Metering CTs Enclosure shorting points
Metering CTs
Bends
IPB tap-offs

Unit switchgear Unit switchgear
CTs for
AVR
IPB tap-offs
Cubicle for VTs' and
surge protection
differential -
CTs for
Line side protection
GeneratorAd '1 "L\
_. ~~~

CTs for diffe - c2 !- Enclosure shorting points
a, , , --b2 . . . . . . . . . . . . . . . . . . . . . . . . . . .

A little distance away to
be out of IPB proximity
area on a ground fault
Stator neutral grounding
transformer (NGT)
Gen. voltage GFF
Li3
~ -~ Neutral grounding
transformer with enclosure
- -
'It may be supplemented with a surge capacitor, to suppress the steepness of a t.r.v. and diminish its r.r.r.v, (Section 17.10.1)
"Typical
Figure 31.2(b) Typical layout of an IPB system in a thermal power station, illustrating enclosure end shortings for continuous
enclosures

Section 28.7). One more advantage of a tubular section radially. The thermal effects of the conductors are taken
is that it exerts equal forces at all points of the enclosure care of by the expansion joints (Figure 31.4(a)) and
and relieves it and the conductor from any undue stresses. those of the enclosure by the bellows (Figure 3 1.4(b)
Octagonal and hexagonal sections are also used as they and (c)).
also have near-symmetry. 0 Naminal current ratings: Some typical current ratings
for the stator voltages considered in Table 13.8 are
Insulating medium: Dry air or SF, gas 10 000 A for a 250 MVA generator to 40 000 A for a
0 Insulators: The conductors are resilient mounted on 1000 MVA generator. (See item 3 of the table for the
post insulators, to hold them in the centre (Figure 31.3) normal current ratings for different MVA ratings and
and dampen the forces, during normal operation or on stator voltages of generators.) The preferred ratings
fault. The conductors are held in position to have free may follow series R-10 of IEC 60059 as in Section
movement axially but they have almost no movement 13.4.1(4).