concrete encased duct bank with multiple voltages

Concrete encased duct bank with multiple voltages how to#

However, if this is not possible due to design limitation, rebars should be ensured not to form a closed electromagnetic path/circuit, this will reduce the losses greatly.Įxtra heating may be dissipated by increasing the overall duct dimensions and/or pvc pipes spacing.Įddy current losses are usually very small compared with circulating currents. I assume that the duct is under construction.Ī duct with trefoil formation pipes with a ring rebars encircling them will avoid that (current summation = 0). RE: HV cable installation 7anoter4 (Electrical) 30 Jan 17 11:42Ĭirculating currents in flat formation ductbank won't be eliminated by transposition along the trefoil route.ġ- short flat formation for a ductbank will cause some rebars circulating currents in addition to eddy currents.Ģ- heating due to rebars circulating currents.

Please share your experience and provide suggestion to mitigate the problem. The basic concern is too much heat inside the busduct due to the induced circulating currents.

Concrete encased duct bank with multiple voltages how to#

How to eliminate/reduce the circulating current which will flow in the PEC cable? I would like to know whether there will be any circulating currents in the rebars due to the magnetic field and eddy current caused by the phase conductor in the PVC pipes.If yes is there any method to calculate this current?Īlso since the PEC cable is laid in parallel together with the single core cable in inside the PVC pipe, there will be some circulating currents to flow in the PEC cable as well (PEC is earthed at both end)due to the same reason as mentioned above.

The trefoil formation is 2km (cross bonding done at 3 intervals along this length)and flat formation inside the duct bank is 15m. There will be a PEC cable installed inside each pipe sleeve for the single core cables. The cable is laid in trefoil formation up to the concrete duct bank where cables are laid in flat formation in the PVC pipe sleeves (6nos) 1 pipe/single core cable. The cable is 275kV single core AWA 1Cx1000mm2, 2 runs per phase with total lenghth up to 2.04km. I'm having an issue with high voltage underground cable installation in a current project.