Voltage sag is one of the major components of power quality of an electric power system. In Malaysia, transmission system's disturbance becomes a dominant source. Voltage sag affects every customer, however, industrial customers are the most affected. Tenaga Nasional Berhad (TNB) has encountered this issue since the first case was reported in 1990. Since then, measurements have been conducted at strategic locations in the transmission system and at customer installations. Statistics indicated that about 42% and 28% of sag occurrences were weather related and transient respectively. Thus far, sag at adjacent bus of a faulted line can be up to 66.57%. Electric utilities cannot be expected to deliver a perfect power supply, however, they shall disseminate sag characteristics to a potential customer in view of reducing the effect on a customer's production. Customers on the other hand must be knowledgeable enough on the load sensitivity to fit into the 'electrical environment'