A realistic appraisal of reliability attributes of electricity supply must also take into account an appropriate modelling and analysis of protection system response scenarios of transmission lines. Due to the prevailing transmission line backup protection coordination schemes, there exist several functional dependencies in their operation. Transmission protection schemes are thus amenable to the propagation of failures due to such dependencies. Neglecting the failure dependency impact would be an oversimplification, leading to the consequent underestimation of the various reliability indices. The scope of studies concerning the impact of protection system reliability on power system reliability is usually restricted to the theoretical domain. This is due to the lack of a suitable methodology and the pertinent input data parameters such as protection system failure rates and probability attributes of missing and unwanted operations of protection systems. The objective of this paper is to present a practical case study based on a Norwegian power system, which effectively accounts for the due consideration of the various transmission protection system response scenarios in the reliability analysis of electricity supply. The methodological evolution towards an integrated approach is first presented. It is then followed by a brief chronicle of the theoretical developments initiated by us in this field, and the subsequent application to a practical case study.