# Gaussian Mixture Modeling for Detecting Integrity Attacks in Smart Grids
## 4 Experimental Set-Up and Results
### The Platform  
The experimental framework is shown in Figure 3 and includes simulation of border gateway routing protocol, SCADA servers, and the corporate network. The specific representation enables studying of the failures appearing on each component of the cyber layer while simplifying the energy network due to the existence of accurate models. MATPOWER [30] and Matdyn [31] were employed at this phase while the simulation step was carefully chosen so as to realize the real-world process as  
Figure 2: A representative paradigm where the proposed system applies the detection scheme to correlated bus voltages.  
accurately as possible. To this end, the simulation step was set equal to 20 ms after verifying that the output of real-time simulation reproduces as accurately as possible the real-world process. The case of IEEE 30 Model Bus was used which is considered to be representative of a portion of the American Electric Power System (in the Midwestern US) as of December, 1961 [32]. The equivalent system has 15 buses, two generators, and three synchronous condensers, while it is worth mentioning that the 30-bus test case does not have line limits. The dynamic data of the model were used by the Matdyn software while the optimal power flow problematic was addressed by Matpower. The integrity attacks were performed on the real values of the bus voltages at randomly chosen time intervals as well as buses. It should be mentioned that, during the nominal state, the load fluctuates between margins predefined by the IEEE model while the sampling period is 20 ms.  
A relatively recently developed platform is called the Assessment platform for Multiple Interdependent Critical Infrastructures (AMICI) [33]. Here, the physical components are simulated while the cyber layer is emulated for obtaining a more realistic representation of the part where the cyber attacks take place. Emulab [34; 35] includes the border gateway routing protocol, SCADA servers, and the corporate network. The specific representation (Figure 3) enables studying of the failures appearing on each component of the cyber layer while simplifying the energy network due to the existence of accurate models.  
One of the most important issues of the specific set-up is achieving synchronization between the simulated parts. In order to ensure that the simulated model runs at the same rate as the actual physical system, we employed PCs with multitasking OSs for execution. There are five Dell PCs with AMD 2 GHz Athlon processor and 2 GB RAM, running FreeBSD 10.1. Simulink graphical programming was used here along with [30] and Matdyn [31] while the simulation step was carefully chosen so as to realize the real-world process as accurately as possible.  
AMICI framework facilitates the simulation of Programmable Logic Controllers (PLCs) including their interaction with software models by transforming model values to measured voltage [34] was employed in this work. More specifically, the messages from Remote Procedure Calls (RPC) are sent to Modbus and vice versa in the form of measured voltage. It should be emphasized that the implementation of client-side calls may offer realization of the interactions with other simulation units. The merit of the specific approach is that the data exchange is realized by an emulated network, thus closing the gap between real world conditions and the experimental platform.  
Figure 3: The experimental architecture showing the cyber, cyber-physical and physical layer.