\begin{center}
\begin{tabular}{ c c c c c c c c c }
& & Line Winding & Valve Windiing & Valve Windiing \\
Rated Voltage & & & Star & Delta \\
Rated voltage at tap \ddag 0, phase to earth & {$kV_{rms}$} & {$525/\sqrt3$} & {$210.4/\sqrt3$} & 210.4\\
Rated power {$(S_{N2w})$} & MVA & 297.5 & 297.5 & 297.5\\
Current ratings, bipolar operation & & & &\\
Rated continuous current, without redundant & {$A_{rms}$} & 982 & 2449 & {$2449/\sqrt3$}\\
cooling in service, at nominal tap & & & & \\
Line winding tap changer regulating range & & & & \\
Number of steps & & +25/-5 & & \\
\end{tabular}
\end{center}
Antwort1
Damit Ihre Tabelle besser aussieht, schlage ich vor, dass Sie den Code wie im folgenden Beispiel gezeigt ändern. Er sollte sich unter pdfLaTeX, LuaLaTeX und XeLaTeX gleichermaßen gut kompilieren lassen.
\documentclass{article}
\usepackage[english]{babel}
\usepackage{geometry,booktabs,siunitx,amsmath,ragged2e,tabularx}
\newcolumntype{C}{>{$}c<{$}} % automatic inline math mode
\newcolumntype{Y}{>{\RaggedRight\hangafter=1\hangindent=1em}X}
\begin{document}
\noindent
\begin{tabularx}{\textwidth}{@{} YlCCC @{}}
Rated Voltage &
& {\text{Line Winding}} & {\text{Valve Winding}} & {\text{Valve Winding}} \\
& & & {\text{Star}} & {\text{Delta}} \\
\midrule
Rated voltage at tap $\ddag0$, phase to earth
& $\si{\kilo\volt}_{\mathrm{rms}}$ & 525/\sqrt3 & 210.4/\sqrt3 & 210.4\\
Rated power $(S_{N2w})$
& \si{\mega\watt} & 297.5 & 297.5 & 297.5\\
\addlinespace
Current ratings, bipolar operation\\
Rated continuous current, without redundant cooling in service, at nominal tap
& $\si{\ampere}_{\mathrm{rms}}$ & 982 & 2449 & 2449/\sqrt3\\
\addlinespace
Line winding tap changer regulating range \\
Number of steps & & +25/{-}5 & & \\
\end{tabularx}
\end{document}