1. LINKS SURVIVAL POWER AUX POWER VOLTAGE LIMITS LINE CHARGE MVAR LINE
CURRENTS
AUX
POWER

2. Permissible Voltage Limits
Voltage Under Normal
Condition
Max permissible Voltage
at the far end of lines
normally kept energized
from one end
Nominal
(kV)
Max
Min kV
132
148
145
120
245
220
245
200
420
400
420
360
735/765
800
700
800

3. Line Charging MVAR Voltage Conductor used Line Charging MVAR
800kv Class Four Bersimis 2.91MVAR/km
400kV Twin Moose MVAR/km
220kV Zebra MVAR/km

4. Approx. Fault Contribution at HV Bus of GT by:-
Approximate Voltage rise at Recieving end per 100km of uncompensated line
0.75 kV for 132kV S/C panther
1.5 kV for 220kV S/C Zebra
3.0kV for 400kV Twin Moose
Approx. Fault Contribution at HV Bus of GT by:-
60 MW ( Hydro) 280 MVA
120 MW (Thermal) 490 MVA
210 MW (Thermal) 735 MVA
500 MW (Thermal) MVA
Approx. %Voltage rise/fall at a bus due to removal/addition
of a reactor of cap. dQ MVAR
= dQ*100 / Fault MVA of the Bus
300 MVAR INJECTION ON A 5000 MVA BUS WOULD CAUSE A
24 KV RISE!

5. Some Important and Useful Thumb Rules
Approx. Line Charging MVAR
132kV Panther: 5 MVAR/100km/ckt
220kV Zebra : 14 MVAR/100km/ckt
400kV Twin Moose: 55 MVAR/100km/ckt
Approx. Line Current
132kV: A/MVA
220kV: A/MVA
400kV: A/MVA
Approx. Voltage drop per 100kM per 100Amp flow at 0.9 p.f. Lag
5 kV for 132kv S/C Uncompensated Line
3 kV for 220kV S/C Uncompensated Line
1.5kV for 400kV S/C Uncompensated Line

6. SURVIVAL POWER REQUIREMENT
The survival power requirement of 120 MW unit is of the order of KW while the requirement of 210 MW unit is of the order of KW and for 500 MW unit, it is in the order of KW. As a general rule, the survival power requirement would be around % of the unit capacity.

7. AUXILLARY REQUIREMENT
The start up power is the power required for the auxiliaries while the generating unit is restored. The requirement of start up power by various units is as follows :
Nuclear & Thermal: 7 to 8% of the unit capacity
Hydro : 0.5 to 1% of the unit capacity
Gas : 1.5 to 2%of the unit capacity
The start up power requirement for starting the thermal units is considerably high as the major auxiliaries like BFP, ID Fan. FD fan, CW pumps etc. are of bigger size and the starting torque is considerable. In case of hydro units, the requirement of start-up power is not significant as there are very few auxiliaries.