The homeowners PV system want to maximize the total energy harvesting from their installed resident PV system (RPS), especially if there is a feed-in tariff (FIT) in play. In this regard, fault detection in solar photovoltaic (PV) arrays allows to expedite PV system recovery time. On the other hand, one of the most common fault in RPS is partial shading and fault diagnosis effort and interpreting this type of fault is motivated us to propose this paper. I-V curve of shaded string included notched and steeped points which are related to signature of shaded cells. In fact, the value of the vertical height in I-V curve represented of percentage of shading. Likewise, the horizontal or voltage distance from Voc of the notched point is related to the number of cells strings within modules those have been bypassed by diodes (Number of bypassed modules). In this work, for first time discrete wavelet transform (dwt) is used to interpret traced I-V curve of PV system and defining these coordinated points in related diagnosis effort.