**2.2 WAMS definition**

There exists a precise and comprehensive definition of WAMS, which has been introduced by Hauer from BPA/Pacific NW National Labs (Taylor, 2006):

"The WAMS effort is a strategic effort to meet critical information needs of the changing power system".

It can be mentioned that a WAMS needs an infrastructure to perform its tasks. This is also defined by Hauer (Taylor, 2006) as follows:

The WAMS infrastructure consists of people, operating practices, negotiated sharing arrangements and all else that are necessary for WAMS facilities to deliver useful information.

In recent years, PMU measurements are commercially available and are widely used in power systems. On the other hand, high speed and low cost communication systems; which are worked based on a layer model, are also well-established in power systems. As a result, the definition of WAMS is slightly different from past. Nowadays, a general definition of WAMS may be presented as follows: The WAMS combines the data provided by synchrophasor and conventional measurements with capability of new communication systems in order to monitor, operate, control and protect power systems in wide geographical area (Junce & Zexiang, 2005).
