Arrangement and method for protecting a power supply circuit component

A transportation system, which comprises a power supply circuit of the transportation system;

• and said system comprising an arrangement for protecting a fuse in the power supply to the transportation system;
• said arrangement comprising determination of the current flowing through the fuse;
• which current through the fuse is determined repeatedly while the fuse is exposed to a load;
• and said arrangement comprising estimation of instantaneous load capacity of the fuse;
• said estimation of instantaneous load capacity being performed using a limitation criterion set for the load capacity of the fuse;
• wherein:
• the aforesaid limitation criterion indicates the longest possible operating time of the fuse under a given loading condition;
• and that, for the limitation criterion, a representation with respect to the current flowing through the fuse is provided;
• and a limitation criterion corresponding to the defined fuse current is derived repeatedly from the said representation while the fuse is exposed to a load;
• and that the estimate of instantaneous load capacity of the fuse is determined on the basis of both the limitation criterion defined substantially at the instant of estimation and the limitation criteria defined before this;
• and that the fuse current is adapted to be limited to a given boundary current value, which boundary current value is determined according to the estimated load capacity of the fuse.

A method for protecting a component in a power supply circuit, in which method:

• the component is fitted in the power supply circuit
• an electric quantity constituting a load on the component is defined repeatedly while the component is subject to loading
• instantaneous load capacity of the component is estimated using a limitation criterion
• wherein:
• the aforesaid limitation criterion is set to indicate the longest possible operating time of the component under a given loading condition;
• for the limitation criterion, a representation with respect to the electric quantity constituting a load on the component is provided
• a limitation criterion corresponding to the defined electric quantity constituting a load on the component is derived repeatedly from the aforesaid representation while the component is subject to loading
• an estimate is determined for the instantaneous load capacity of the component on the basis of both the limitation criterion defined substantially at the estimation instant and the limitation criteria defined before this.