Masterclass about Power Grid Faults
Ever wondered what happens when the lights flicker or a blackout strikes?
Well, in the next blog post, we’re diving into the everyday hiccups of power systems. No need for an engineering degree — we’re breaking it down in simple words. Learn about the glitches, like short circuits, that power systems face and find out why blackouts happen. It’s like peeking behind the curtain of electricity — simple, fascinating, and coming your way soon! ⚡️👀
Fault Types
A power failure in the power network is classified as a shunt fault (short circuit fault) or a series fault (open circuit fault). An open circuit fault occurs when one or more conductors (phases) open in the system due to a broken line. The short circuit fault occurs when two or more conductor lines come into contact with each other or to the ground. 75 − 80% of power failures are either a line-to-ground short circuit or a transient fault. Moreover, short circuit faults are classified as symmetrical faults (balanced faults) or as unsymmetrical faults (unbalanced faults) [1].
- Open circuit fault: it occurs when a low-resistance path is created between two points in the electrical system, causing an excessive flow of current. These faults usually happen due to common problems such as joints failing in overhead lines and cables, issues with a circuit breaker phase, and the melting of a conductor or fuse in one or more phases.
- Short Circuit Fault: this type of fault occurs when there is an unintended break or discontinuity in a circuit, preventing the normal flow of current. Short-circuit faults primarily occur due to insulation failure between phase conductors and the ground. When insulation fails, it creates a path for short-circuit current, leading to the activation of short-circuit conditions in the circuit.
Moreover, short circuit faults are classified as symmetrical faults (balanced faults) or as unsymmetrical faults (unbalanced faults) [2].
a. Symmetrical Faults: these are very severe faults and occur infrequently in the power systems. The main symmetrical fault is three-phase line-to-line (LLL). Only 1 - 2% of faults are of this kind. If these faults occur, the system remains balanced (same current in all three phases) but results in severe damage to the electrical power system equipment.
i. LLL fault: a three-phase line-to-line fault is an electrical fault in which three phases of a power system are simultaneously short-circuited and the ground is not involved.
b. Unsymmetrical faults: These are very common and less severe than symmetrical faults. Asymmetrical faults create different current magnitudes in each phase. There are three types. LG, LL, and LLG fault [2].
i. LL fault: A line-to-line fault mainly occurs once two conductors are short-circuited and also due to heavy wind. The L-L fault results in a high current flow that causes power system components to be damaged immediately.
ii. LG fault: Single line-to-ground fault occurs when one phase comes into contact with the ground, creating an imbalance in the current distribution. This type of fault has two major effects on an electrical system: first, there is a significant voltage drop at the point of fault (due to high current draw), and second, most of the current flow through one phase conductor instead of all three phases.
iii. LLG fault: a double line fault takes place where two or more phases of a three-phase system come in direct contact with the ground, leading to an uneven distribution of current. Since current flows primarily in the faulted phase(s) and not equally in all three phases, a three-phase line-to-ground fault is considered an asymmetrical fault.
Causes
Time to talk about the causes behind those grid disruptions!
The magnitude of the cause will affect the resulting consequences. A minor cause leads to a small fault that affects only a few houses and can be quickly repaired, possibly within hours. However, a large-scale cause like a hurricane or terrorist attack can cause a widespread fault, such as a blackout or cascading failure, impacting a large area and taking days or even weeks to recover from. Large-scale outages have significant economic and social consequences that impact consumers. In such cases, a robust system is expected to recover and restore to its original state [3].
Main causes reported in the literature:
- Natural Causes: different types of natural disasters that could lead to a fault in the EPG, such as hurricanes, storms, flooding, earthquakes, tornados, heat waves, or solar flares.
- Errors: causes related to human faults or equipment technical malfunction.
- Attacks: cyber-attacks such as denial of service (most common), or human attacks such as terrorism.
Analyzing Figure 2, based on the literature review done by [3], shows that 84% of articles mention faults due to natural causes. The most referenced natural causes are hurricanes and storms, with 22% of articles mentioning these causes, followed by other natural events such as heat waves or thunderstorms, which were studied in 20% of all articles reviewed in 2019. Still, in the natural causes cluster, windstorms and tornados represent 14% percentage of the articles, and earthquakes appear in 11% of the studies. Nowadays, grid failures caused by RES are minimal but increasing due to synchronous machines’ decommission and more intermittent power integration.
Impact of Renewables on the Grid
Ensuring the reliability and stability of a Smart Grid System involves considering various factors. One key aspect is integrating Renewable Energy Resources (RERs) into the power grid. When RERs are incorporated at a low voltage level, it increases the likelihood of faults due to bidirectional power flow. The location of RERs in the system also plays a crucial role, influencing dispatch modes based on penetration levels and their rapid response. Additionally, fluctuations in current and voltage, caused by variations in active and reactive power due to RERs, impact the overall stability and reliability of the system.
The topology of inverters associated with RERs is another factor influencing the system’s reliability. Control parameters, including gains of real and reactive power, can alter the damping ratio of RERs, impacting system oscillations. Furthermore, frequency deviation occurs during post-fault conditions when the Smart Grid System transitions from grid-connected to islanded mode. This frequency deviation can lead to generator tripping, resulting in dropped loads [1].
Recap
We’ve clarified the nuances of disturbances that may affect and disrupt the electricity flow. From short circuits to open circuits, we’ve examined the causes, providing insight into the inner workings of our power systems.
But our exploration doesn’t stop there. We’ve also delved into the impact of renewable energy on the power grid. As clean energy sources gain momentum, understanding their integration is crucial. We’ve unveiled the challenges that come with the increasing penetration of renewables, providing insights into the evolving landscape of our energy future.
As we conclude this blog post, I invite you to continue this enlightening journey with me on Medium. Follow for more deep dives into the dynamic realms of power markets, grid resilience, and energy storage. Let’s stay connected as we navigate the energy landscape together! 👏🏻👏🏻👏🏻
References
- M. Mousa, S. Abdelwahed, and J. Kluss, “Review of Diverse Types of Fault, Their Impacts, and Their Solutions in Smart Grid,” 2019 SoutheastCon, Huntsville, AL, USA, 2019, pp. 1–7, doi: 10.1109/SoutheastCon42311.2019.9020355.
- Gaurav, J. (2023, April). Different Types of Faults in Power System | Explained | TheElectricalGuy [Video]. YouTube. https://www.youtube.com/watch?v=UE3OYs5oO74&t=78s
- Mar, Adriana, Pedro Pereira, and João F. Martins. 2019. “A Survey on Power Grid Faults and Their Origins: A Contribution to Improving Power Grid Resilience” Energies 12, no. 24: 4667. https://doi.org/10.3390/en12244667.
