bug fix: ° not in unicode

doc/elements/trafo_par.csv

@@ -17,8 +17,8 @@ tp_mid;integer;;rated tap position
 tp_min;integer;;minimum tap position
 tp_max;integer;;maximum tap position
 tp_st_percent;float;:math:`>` 0;tap step size for voltage magnitude [%]
-tp_st_degree;float;:math:`\geq`  0;tap step size for voltage angle [�]
+tp_st_degree;float;:math:`\geq` 0;tap step size for voltage angle
 tp_pos;integer;;current position of tap changer
 max_loading_percent**;float;:math:`>` 0;Maximum loading of the transformer with respect to sn_kva and its corresponding current at 1.0 p.u.
-df;float;1 :math:`\geq` df  :math:`>`0;derating factor: maximal current of transformer in relation to nominal current of transformer (from 0 to 1)
+df;float;1 :math:`\geq` df :math:`>`0;derating factor: maximal current of transformer in relation to nominal current of transformer (from 0 to 1)
 in_service*;boolean;True / False;specifies if the transformer is in service.