# Alternator on a long transmission line

1. Feb 27, 2010

### samieee

Could it be dangerous to connect an alternator to a long transmission line,if the line has high capacitance?if dangerous then why? plz explain...

2. Feb 27, 2010

### sophiecentaur

How long, what frequency and what operating power?
If you connect a quarter wavelength of open circuit transmission line to your alternator, then it will look like a short circuit. This is only relevant for very long transmission lines (trans continental style) at 60 or 50 Hz.
A 'short' / regular length of transmission line will be, effectively, a capacitor, with a value of a few tens of pF per metre of line. This will affect the Power Factor of the load seen by the alternator. You would need to know what PF the particular alternator can cope with and at what output power.
The problem is that, to deliver a given Power, a PF which is less than unity (1) will require more current for a given voltage than the 'Power =Volts times Amps' would suggest. This is because the capacitor will need to charge and discharge, requiring current to flow in addition to the current in the (resistive) load. This current is not in phase with the voltage so there is no 'useful power' involved - just extra current handling demand on the cables and alternator windings.

Last edited: Feb 27, 2010
3. Feb 27, 2010

### Staff: Mentor

What is the context of your question? What kind of alternator? Is this for schoolwork?

4. Feb 27, 2010

### dlgoff

Last edited by a moderator: Apr 24, 2017
5. Feb 28, 2010

### samieee

any kind of alternator,any frequency (let assume it as supply frequency).Any way i got the answer,the anser is :It is dangerous,because at high capacitance(leading power factor) the stator MMF will aid the rotor MMF thus the voltage will increase at large magnitude.which is not desired.

6. Feb 28, 2010

### Jobrag

One of the problems with long transmission lines and capacitance is that even if the line is isolated there is the posibility of lethal voltages still being present in the lines. Put into circuit earth and prove dead.