The Impact of Load Altering Attacks on Distribution Systems with ZIP Loads (2311.06429v4)

Abstract: Load-altering attacks (LAAs) pose a significant threat to power systems with Internet of Things (IoT)-controllable load devices. This research examines the detrimental impact of LAAs on the voltage profile of distribution systems, taking into account the realistic load model with constant impedance Z, constant current I, and constant power P (ZIP). We derive closed-form expressions for computing the voltages of buses following LAA by making approximations to the power flow as well as the load model. We also characterize the minimum number of devices to be manipulated in order to cause voltage safety violations in the system. We conduct extensive simulations using the IEEE-33 bus system to verify the accuracy of the proposed approximations and highlight the difference between the attack impacts while considering constant power and the ZIP load model (which is more representative of real-world loads).

• The paper presents a novel closed-form framework that quantifies the impact of load altering attacks on voltage profiles in systems with ZIP loads.
• It employs a graph-based, radial power system model and simulates scenarios on an IEEE-33 bus system using MATPOWER for validation.
• Results show that attack location critically influences voltage drops, emphasizing vulnerabilities in IoT-controllable devices.

The Impact of Load Altering Attacks on Distribution Systems with ZIP Loads

The paper focuses on analyzing Load Altering Attacks (LAAs) in distribution systems integrated with ZIP loads, a realistic load model encompassing constant impedance, current, and power components. The research seeks to understand the effects of LAAs on the voltage profile within these distribution systems, emphasizing the need for voltage-dependent load consideration in cybersecurity analyses.

Introduction and Motivation

Load Altering Attacks pose substantial threats to power systems particularly due to the increased presence of IoT-controllable devices. These devices, such as smart air conditioners or electric vehicle chargers, introduce new vulnerabilities since they are significantly less secure than traditional SCADA systems but can be manipulated by attackers to alter power demand.

Historically, studies have concentrated on the influence of LAAs on transmission grid frequency and power balance. However, there is a gap in understanding their effect on distribution grids, especially regarding voltage profiles influenced by voltage-dependent load models like ZIP loads.

System and Load Models

The power system model adopted uses a graph-based approach with a radial structure capturing the relationships between buses and branches. Key elements are characterized, including node buses and branch impedance and power flows.

Different load models are implemented, focusing primarily on the ZIP load model that reflects real-life load characteristics due to its voltage-dependent nature. The ZIP model is contrasted with the constant power (CP) load model, demonstrating the voltage effects across distribution systems.

Analytical Framework for LAAs

The analytical framework developed considers two main factors affecting the distribution system's voltage profile post-LAA: load model dependency and attack location. Closed-form expressions are derived to quantify the LAA impact using assumptions like LinDistFlow for voltage calculation and the ZP approximation for ZIP loads.

For constant power loads, simplified expressions advocate for understanding how manipulating load demands can disrupt system voltages. Comparatively, the ZIP model introduces complexity due to its quadratic voltage dependence, necessitating iterative solution approaches but providing improved voltage resilience.

Closed-form Approximation Techniques

To address the complexity with ZIP loads, the paper introduces a closed-form approximation based on the ZP model. This approximation simplifies the load model while preserving necessary characteristics for accurate impact assessment. The resulting system of linear equations facilitates bus voltage calculations efficiently.

Numerical Analysis and Results

The IEEE-33 bus system serves as the simulation base, leveraging MATPOWER for execution. Comparisons between calculated voltages using the closed-form approximation and those from the robust BFS method establish the approximation's efficacy and precision.

The simulations reveal the LAA effect's severity based on attack location, stressing attacks on leaf buses result in deeper voltage dives. Practical implications emerge for strategic device manipulation during attacks, with numerical results outlining critical scenarios leading to voltage safety violations.

Conclusion and Future Directions

The investigation successfully outlines LAA impacts on distribution systems with ZIP loads, offering valuable analytical tools and insights into voltage dependency effects. Future work will extend this framework to more comprehensive systems incorporating distributed generation and will seek to devise efficient mitigation strategies against LAAs.