Consider this example:
\definepagebreak
[saut]
[yes,header=empty]
\setuphead[part][page=saut,numberstyle= ,numbercommand={\uppercase},placehead=yes, alternative=middle,align=middle,
before=\startstandardmakeup,
after=\stopstandardmakeup,conversion=Romannumerals,style={\switchtobodyfont[60pt]}]
%
\define[1]\Dot{#1.}
\define[2]\myheadnumber{%
\startframedtext[frame=off,align=middle]
{\bf\ss\switchtobodyfont[30pt] #1 }
\vfill \blank[2cm]
{\switchtobodyfont[20pt] #2 }
\stopframedtext }
\setuphead[chapter][command=\myheadnumber,align={middle,nothyphenated, verytolerant},header=empty,footer=empty,commandbefore={\blank[0.5em]},
commandafter={\blank[2cm]},alternative=middle]
\setuphead[section][align=middle,style=\bfc ,numbercommand=\Dot]
\starttext
\completecontent[creterium=all]
\startpart[title={My part title}]
\startchapter[title={my chapter title}]
\startsection[title={My section title}]
\dorecurse{5}{\input knuth}
\stopsection
\stopchapter
\stoppart
\startpart[title={My part title}]
\startchapter[title={my chapter title}]
\startsection[title={My section title}]
\dorecurse{5}{\input knuth}
\stopsection
\stopchapter
\stoppart
\stoptext