# Voltage Drop Between Generator and Main Switchboard on an Ocean Going Vessel

[1] A new 1.2 MW, 415V, 50 Hz diesel generator has its voltage dropped between its TB and Main switchboard, by more than 6 V (415 down to 409 V) at 100% Resistive load (P.F=1.0).

[2] The distance between the Generator and the MSB is 129 Mtrs. Single core cables of 1x240 sq mm - each 6 runs are laid for each of the 3 phases- total single core cables are 18 nos.

[3] Trefoil configuration of the single core cable is done on the cable trays starting from the Generator room to the MSB room except for small areas in the Bulkhead coamings.

[4] The currents in the individual cores differ by a maximum variation of 10 A for each phase.

All copper lugs are connected tight at both ends and we did not observe any abnormal temperature increase at the lugs end with temperature thermometer.

The voltage drop progressively increases from 1 volt to 6 volts at 100% resistive loading using a sea water based rheostat.

I need to get the voltage drop down to less than 4 volts between Generator and MSB at 100% load which I am unable to achieve for the trial agencies to agree to pass the test.

We observed more volt drop and wide variations in individual core currents when trefoil combination was not done. Now after trefoil is done, the currents between individual cores of a single phase have come to a new average value and the volt drop has come down a bit.
But it is is still not enough.

Can anyone help me to identify what more can be done?

The cables used are EBXL cables. Does additional 3x185 sq mm cable if laid between MSB and Generator solve my problem? Or- should I completely remove all single core cables and lay only 3 core cables?

The supplier is Cummins in India.

my email address is [email protected].
--
Regards,
Surya
India

R

#### RoyMatson

>[1] A new 1.2 MW, 415V, 50 Hz diesel generator has its
>voltage dropped between its TB and Main switchboard, by more
>than 6 V (415 down to 409 V) at 100% Resistive load

I presume the Voltage regulator senses the Voltage at the generator terminals. Would it be practical to sense the Voltage at the Main Switchboard end of the cables? That way it could compensate for the Voltage drop.