Saqib Hassan
New member
- Location
- Karachi
I am new at this forum, It will be very helpful, if i can get answer for the following queries:
We have a system of 4 machines of following denominations:
1. 2x24 MW, 60 Hz, 13.8KV (for industrial plant supply)
2. 1x10 MW, 60Hz, 13.8KV (for industrial plant supply)
3. 1x60MW, 50 Hz, 11KV (for Power Export to National Grid)
The 60 MW, 50Hz machine is being used to export to national grid at 132 KV through a 11/132 kV 80 MVA transformer. The fault level of grid at 132 KV is 8KA from the short circuit report.
Please note, all Generators are installed in a turbine hall and 132 KV Grid station is 250m away from the Generator/turbine hall/industrial plant.
Whereas, the 3 remaining machines of 60 Hz are being used to supply internal/industrial plant having motors and Transformers of different ratings. The different levels of faults are as under at different voltage levels for the internal plant from the short circuit report are as follows:
13.8KV: 10 kA
6.6kV: 23kA
480V: 72kA
Q1: Please advice which fault current (8KA@132KV, 10KA@13.8KV, 23KA@6.6KV, 72KA@0.48kV) to be used while calculating Step and Touch potential, please inform the step and touch potential for our system, if the earthing system is being designed for achieving earthing resistance of 0.4 ohm. Further, please also advice if there is a need of lesser earthing resistance.
Q2: Further, I want to know, if there is any recommendations of having different earth system for 50 Hz and 60 Hz.
Q3: Please also suggest, if we need to have a separate earthing for DCS/control system and Power system.
We have a system of 4 machines of following denominations:
1. 2x24 MW, 60 Hz, 13.8KV (for industrial plant supply)
2. 1x10 MW, 60Hz, 13.8KV (for industrial plant supply)
3. 1x60MW, 50 Hz, 11KV (for Power Export to National Grid)
The 60 MW, 50Hz machine is being used to export to national grid at 132 KV through a 11/132 kV 80 MVA transformer. The fault level of grid at 132 KV is 8KA from the short circuit report.
Please note, all Generators are installed in a turbine hall and 132 KV Grid station is 250m away from the Generator/turbine hall/industrial plant.
Whereas, the 3 remaining machines of 60 Hz are being used to supply internal/industrial plant having motors and Transformers of different ratings. The different levels of faults are as under at different voltage levels for the internal plant from the short circuit report are as follows:
13.8KV: 10 kA
6.6kV: 23kA
480V: 72kA
Q1: Please advice which fault current (8KA@132KV, 10KA@13.8KV, 23KA@6.6KV, 72KA@0.48kV) to be used while calculating Step and Touch potential, please inform the step and touch potential for our system, if the earthing system is being designed for achieving earthing resistance of 0.4 ohm. Further, please also advice if there is a need of lesser earthing resistance.
Q2: Further, I want to know, if there is any recommendations of having different earth system for 50 Hz and 60 Hz.
Q3: Please also suggest, if we need to have a separate earthing for DCS/control system and Power system.