1 © A. Kwasinski, 2015 Cyber Physical Power Systems Fall 2015 Security

2 © A. Kwasinski, 2015 Cyber-physical power system Cyber security Part 1

3 © A. Kwasinski, 2015 To find the power flow along lines we need to calculate: To calculate the above equation we need to solve This is an undetermined system of equations (the matrix is singular) then, the voltage (magnitude and angle) at a bus (called slack or swing bus) is set (usually a relative per unit voltage of 1 with an angle of 0). As a result, the equation for the slack bus replaced by this set voltage value and the real and reactive power at this bus are now unknown. Other knows and unknowns are: In a PQ (load) bus: P and Q are known, voltage is unknown In a PV (generator) bus: P and V are known, reactive power and voltage angle are unknown. Review from 1 st week

4 © A. Kwasinski, 2015 Review from 1 st week Operation of a power grid is controlled from a dispatch center. Responsible for monitoring power flow and coordinating operations so demand and generation are match in an economically optimal way. That is, from a stability perspective demand (plus losses) needs to equal generation but from an operational perspective, such match needs to be achieve in an economically optimal way. Source: Scientific American

5 © A. Kwasinski, 2015 Review from 1 st week Operation and monitoring of electric power grids is usually performed with a SCADA (supervisory control and data acquisition) system. At a basic level a SCADA system includes: Remote terminals Central processing unit Data acquisition (sensing) units Telemetry Human interfaces (usually computers). SCADA systems require communication links but, usually, these are dedicated links separate from the public communication networks used by people for their every day lives.

6 © A. Kwasinski, 2015 Hierarchical control: At the highest level an economical optimization algorithm is run in order to produce a set point for power generation units. Local autonomous controllers at the power generation units use droop controls that uses the set point inputs produced by the higher level controller. Additional controllers exist at the power transmission and distribution levels to ensure electric power is delivered according to the specified power quality parameters. The economic dispatch algorithm implies solving power flow equations and also knowing other information (e.g. market conditions, prices from each unit, etc.). In addition to considering economic profitability, stable system operation needs to be ensured by the controller. Also power flow and other constrains exist…… All of these factors affect control decisions Control Architecture

7 © A. Kwasinski, 2015 Control decisions require state estimation. I.e. knowing voltages and angles. State estimation, in turn, requires measuring real, reactive powers or current flows. It also require knowing system parameters (e.g. lines data). Measured data needs to be transmitted to the dispatch center so a cybernetic infrastructure is needed. This cyber infrastructure includes sensors and communications infrastructure. Additionally, system parameters need to be stored so they can be accessed and used when running the economic dispatch algorithm. Hence, optimal operation requires communication Limited operation of a power grid can still be performed without communications thanks to the droop controllers. However, this operation will be economically suboptimal and with reduced stability margins. Control Architecture

8 © A. Kwasinski, 2015 In general, power grids use dedicated networks so intrusive access is difficult. However, some legacy equipment may still use resources from public communication networks. Communications Architecture

9 © A. Kwasinski, 2015 Smart grids, Internet of things and other increasingly used technologies (e.g., demand response or electric vehicles), may motivate increased used of public communication networks or the Internet as a result of the need for more bandwidth or more access points. Communications Architecture

10 © A. Kwasinski, 2015 PMUs may be another potential point of entry or a piece of equipment that can be acted upon directly leading to state estimation errors. Additional entry points: Renewable energy sources generation location. Smart meters Home energy management systems Electric vehicles Internet of Things equipment (e.g. appliances). Supply chain (e.g. firmware in new equipment, memory sticks, etc.) Cyber dependencies create vulnerabilities. Examples of cyber dependencies include: GPS systems Weather and other important external data. Control Architecture

11 © A. Kwasinski, 2015 Cyber attacks may directly target: State estimation Parameter database Act directly by sending commands to equipment (e.g. relays controlling circuit breakers). Indirect cyber attacks: those targeting cyber-lifelines directly and leading to power grids operation disruptions indirectly. Type of cyber attacks: Reconnaissance Denial of Service Command injection Measurement injection Control Architecture