This paper presents the analysis on hidden node due to multiple transmission power level and its potential impact to system performance of White Space radio operating in the TV bands, a.k.a TV white space (TVWS). For this purpose, a generic interference model for determining the hidden node occurrence probability based on realistic physical (PHY) layer model is developed. Firstly, the generic hidden node interference model is constructed considering typical TVWS radio network deployment scenario. Emphasis is given on cases where the hidden node scenario involves multiple transmission power level. Secondly, the PHY layer design and channel propagation are modeled to analyze the realistic operating range of the TVWS radio. By combining the hidden node interference model and the PHY layer/propagation models, the realistic probability of hidden node occurrence is calculated. Finally, the performance degradation in the victim receiver due to interference generated by the potential hidden node is quantified. As a result, for urban environment, it is found that for networks consisting of devices with multiple transmit power level, the probability of hidden node occurrence is similar to that of networks consisting of devices with uni-transmit power level, provided that the interferer-victim separation distance in the former is 800m farther apart. Furthermore, this number may increase to a maximum of 1.1km in a suburban environment. Also, it is found that if the hidden node actually occurs, a co-channel interference (CCI) of -15dB typically causes a degradation of 2dB in the victim receiver.