Match the following

$$(P)$$ single phase fully controlled $$ac-dc$$ converter
$$(Q)$$ Voltage commutated $$dc-ac$$ chopper ($$E$$ = input $$dc$$ voltage)
$$(R)$$ Phase voltage of a star connected balanced three-phase load fed from a three-phase inverter with $${180^ \circ }$$ conduction (input $$dc$$ voltage=$$E$$)
$$(S)$$ Line voltage of a six stepped inverter with input dc voltage $$E$$
$$(T)$$ Three-phase diode bridge rectifier.

The insulation level of a $$400$$ kV, EHV overhead transmission line is decided on the basis of

The insulation resistance of a cable of length $$10$$ km is $$1$$ $$M\Omega $$. For a length of $$100$$ km of the same cable, the insulation resistance will be

The surge impedance of a $$400$$ km long overhead transmission line is $$400$$ $$\Omega $$. For a $$200$$ km length of the same line, the surge impedance will be