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Among all electric disturbances, flicker is not the most harmful one resulting in malfunction of grid equipment and customer appliances, because flicker phenomena is evidently visible, all twinkling lamps may lead to often LV customer complaints. For utilities, flicker estimation is one of the necessary tasks in assessment of emission level for the connection of fluctuating installations to electric power systems. Two main grid access contracts have been put into service in France between utilities and customers. These grid connection contracts not only fix power quality commitments for system operators but also set customer disturbance emission limits. The practice of these contracts is to emphasize that a good overall electric power quality can only be achieved by respecting commitments and doing effort from both of grid and customer sides. The system operator is responsible for specifying requirements for the connection of fluctuating installations to the system. Some simplified methods used by utilities have been presented in this article. System operators have to perform pre-connection study before a customer is connected to their grid. In order to comply with flicker commitments and some relevant IEC standards in emission limits for fluctuating installations, adequate methods under scope of IEC rules have been used in estimating customer flicker emission level prior to load connection. For flicker assessment in the sophisticate network and with irregular load changes, the method based on electric circuit simulation including flicker source models and IEC flicker meter emulator is presented. Case studies show this method is very appropriate in pre-connection studies.