Analyzation of power supply for cranes

Due to frequent problems with electrical equipment on cranes it was necessary to inspect quality ofpower connected to cranes.

We coordinated team effort together with other company to measure current, voltage andharmonics.

Measuring was done using Fluke 435-II

Measuring was done on crane 104 JB A200 while crane was in 2 positions:

1. while crane was at main isolator junction box column 7 where cables are connected to bus bars

2. while crane was between main isolator and parking area around column 10

Following was concluded:

Voltage varied from 457 to minimum of 430 volts when crane was at column 10. whichequals to around +- 4% of voltage variation.

Current varied from 0 to 650, highest peak had value of 1146 A. Permanent current wasstabilized around 450A per phase( 2 magnets and 2 hoists working at same time) . 260 A ofpermanent current with 2 magnets working .

Inspection of current collectors revealed that current collectors installed have maximum permanentcurrent of 350 A.

Current harmonics measurement using 2 magnets and 2 hoists revealed TDD total demandeddistortion was around 85% on average . 3rd 23% 5th 44% 7th 33%

IEEE standards for industrial networks limits TDD for current to 15% or 12% per harmonic

While EAF was working THD total voltage harmonics distortion was measured at 138%

IEEE standards for industrial networks limits THD for voltage to 10% per

Current and voltage distortion using magnets

Magnet current and voltage distortion

EAF current and voltage distortion