Page 848 - Industrial Power Engineering and Applications Handbook

24/802 Industrial Power Engineering and Applications Handbook

132/33 kV
Load 29.4 MVA
at 0.88 p.f.

(1) The capacitors are shown in the centre of
the line which being the best location. But
* 27 Nos. 100 kVAr each Shunt capacitors they can be provided near the receiving
end transformer also.
N, (Series group) = 3 HH 2240 kVAr per
N2 (Parallel group) = 9 phase (2) They are to be mounted on platforms,
insulated for 19.05 kV from the ground.
HH (for arrangement (3) The normal practice is to mount each
refer to Figure phase units on separate platforms,
HH 23.18b) insulated for 33 kV from each other.
HH
h)
2700 kVAr
per phase
Figure 24.27(a)
Application of series compensation on an HT distribution network
7 To provide reactive support for any power system or
6.96 kv
network, suffering from voltage fluctuations or high
carry
load
it
to
important
out
transfer
required
the
a field study first, to identify areas and suitable locations
= 20.75 kv line losses or when it is felt is that the system cannot
2.761 kV where reactive support would be more appropriate. A
17.16"
6.95" procedure along the lines of Example 24.3 to determine
11.48" V, = 19.05 kV ,oo kV the amount and type of reactive support should then
525 A be adopted.
* Series compensation
Note Above we have dealt primarily with the technical aspects
In fact E, is the fixed phasor and V, the variable But for ease of of reactive controls. For commercial implications, see
drawing, we have considered V, as the base phasor. Lakervi and Holmes.
Figure 24.27(b) Receiving-end voltage after shunt and series
comDensations
24.9 Transient stability level
6 For large concentrations of loads, such as for an
industrial or a residential area and where addition of This defines whether a system can restore normal operation
more loads in future is likely, forecasts of a realistic following a major disturbance, such as on a
loading of lines may fail. Therefore, for growing cities
particularly, it is advisable to install initially a slightly Transient phase to ground fault
larger primary distribution network to cater for the Phase to phase fault
increasing power needs. It is felt that for such load The outage or failure of a generating unit
centres, an 11 kV or even 33 kV. distribution is Failure of the overhead line or a transformer and
inadequate. The commensurate primary distribution Sudden opening of the line.
for such locations may be considered at 66 kV, and in
residential and industrial areas or public places
underground cabling should be adopted to rninimizc The highest level of power it can transmit during such
the risk of running such high tension lines in the open disturbances is its transient stability limit. Dampening
and also save the scarce load area. Underground cabling the power oscillations on such disturbances and restoring
is more expensive than an overhead system, but is the power system to stable limits are the main objectives
more safe in congested areas. The use of an overhead of reactive control. From the load curves one can observe
or underground system will depend upon the location, that an uncompensated line may have dangerous power
safety and convenience, besides consideration of cost. swings on small fluctuations of load, which may lead to
See Lakervi and Holmes in the further reading for loss of synchronism between two generators and even
more details. cause an outage of the line. To keep this system stable
during such disturbances, it must be operated at much
Note below its steady-state stability level.
Countries like the USA and Japan have adopted underground Consider a typical case during a line disturbance when
cabling for transmission of power up to 1000 MW at 550 kV. the line is not adequately compensated. A transmission