Washington, D.C. - Shortly before 1 p.m. Tuesday we experienced a dip in voltage in the Washington D.C. area.  This was caused by an issue with a transmission line. There was never a loss of permanent supply of electricity to customers. The dip in voltage caused equipment at some customer facilities to transfer to their backup systems.  The momentary outage occurred because of customer equipment responding to a dip in voltage.  Customers should be able to operate their own equipment at this time.  There are no current supply problems. We have crews onsite investigating the cause.