Electrical System Protection Grading Program

PROTECTION GRADING PROGRAM

The program below is the program that to determine the setting for the HT or LV electrical system from downstream onward. The program will automatically generate the graph of the setting that has been set or select for the design system.

HOW TO READ THE CALCULATION SHEET

1. The grading program starts first with the most downstream relay.


2. Column A - Protection relay name or number


3. Column D/E - CT Ratio


4. Column F - Maximum demand in amperes


5. Column H - Fault level in amperes


6. Column I - Highset current


7. Column J - Type of IDMT curve: NI = normal inverse, VI = very inverse, EI = extreme inverse


8. Column L - Plug setting in percentage of CT ratio


9. Column M - Plug setting in ampere Plug setting = maximum demand + spare


10. Column O - Calculated grading margin in seconds The margin shown is the margin between the corresponding relay with immediate downstream relay, ie the relay shown one row up.


11. Column P - Relay operating time in seconds


12. Column R - TMS setting in per unit


13. The full-load current stated for RT01 or RT03 is the actual MD required (without any spare).


14. The full-load current stated for the TNB relay is the preliminary MD applied.

Following the Codes for relay type used in this Program

CDG - manufactured by GEC Measurements, UK
MCGG - manufactured by Alstom, UK (for NI and VI curves)
KCGGEI -manufactured by Alstom, UK (for EI curve)
KCGG - manufactured by Alstom, UK (for NI and VI curves)
KCGGEI - manufactured by Alstom, UK (for EI curve)
2TJM - manufactured by NEI Reyrolle, UK (electro-mechanical type)
SPAJ - manufactured by ABB
DCD - manufactured by VA Tech Elin (Reyrolle), UK (numerical type)

The Result / Graph that generated by the Program

Recommendations

This program suitable for all engineer for their checking and designing. This Software has been used for my project such as Megasteel project at Olak Lempit, Banting. Cold Rolled Steel Factory. Refer to my Construction Site.

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