Suhail - it is not clear what exactly u want to generate.

In general if u want to generate a disturbance to the original signal there are lot of options. probably u try with the in-build m-function 'awgn'. this function adds a white gaussian noise to the actual signal based on the parameter given by the user, this will be considered as the disturbance to the original signal.

U can generate the current distortion and voltage distortion in terms of faults and u can use the switching of circuit breakers for that

Thanks very much for your reply. I want to generate a sinusoidal signal with different disturbances at 50 or 60Hz frequency.

I suggest you the SimPowerSystems MatLab module. this module has a controlled voltage source. You can generate the desired signal using this source.

You might have already gotten the answer to your question, but in the interest of future researchers :

You may use my code for the same. It models 8 different types of power quality disturbances

http://www.mathworks.com/matlabcentral/fileexchange/52190-model-power-quality-disturbances---