Tag Archives: digital twin

IEEE TPWRS paper on fire-detecting digital twin of overhead line, News

IEEE TPWRS Paper on Digital Twin of Overhead Lines for Fire Detection

March 2022

Extending some of my previous work, I developed a digital twin for overhead conductors that detects an approaching forest fire and de-energizes the affected lines in a timely manner and not preemptively. The work has just been accepted in the IEEE Transactions on Power Systems (preprint here).

In California (CA) and elsewhere, the risk of overhead conductors igniting forest fires or adding seats to on-going ones is very real and extensive. In CA, PG&E’s overhead conductor equipment was determined to be the reason for the 2018 Camp fire, leading to law suits that caused the utility’s bankruptcy. After restructuring, the company updated its practices with preemptive disconnections of large parts of its grid during days of high risk of fire. The new practice disrupted service to thousands of customers, in most cases unnecessarily. Hundreds of new suits threatened PG&E with a second bankruptcy in 3 years.

Phasor Measurement Units (PMUs) have been widely adopted across grids. PMUs may be installed along a line in distances as close as a 1-2 miles in between. This gives rise and basis to the idea of real-time monitoring of line impedance for any reasons of variation. As resistance increases with ambient temperature (not proportionally), steep decreases in the inductance/resistance ratio (tangent of the impedance phasor – tanδ in the figure) of an overhead conductor may indicate that a forest fire burns near said conductor and it should, thus, be disconnected.

Behavior of moving average of impedance phasor as a forest fire approaches an overhead conductor and affects its resistance. Such a behavior should control the disconnection of this conductor.

The in silico testing under numerous worst case scenario conditions (no solar heating effect, broad measurement error intervals, synchronization errors, etc.), showed that the proposed method detects some cases of a forest fire approaching a conductor, in sub-second times and at extremely low false positive rates. In the next steps, I plan a collaboration with interested utilities and the US Forest Service for field testing.

I want to thank CMU ECE’s MSc student (at that time) and co-author Uday Sriram for his help in setting up the tests, Dan Dietmeyer from SDG&E for informing me about PMU deployments in CA, Farnoosh Rahmatian from NuGrid Power for lending his expertise on instrument transformers and Jeff Dagle from PNNL for his crucial comments in the earlier stages of this work.

Blog, Electrical Grid Digital Twin

Digital Twins of Electrical Grid Assets

January 2022

A few months ago, my work with Omid Mousavi from DEPsys SA on the Digital Twin of the Medium Voltage side of a Distribution Transformer based on Low Voltage side measurements was published in the IEEE Transactions on Power Delivery (preprint). I have been getting numerous hits on that paper plus some invitations for collaboration, so I thought I should blog a few thoughts about the subject a bit more broadly.

Let me start by describing the idea of this specific publication first. We want to monitor harmonics and system faults with adequate accuracy and, preferably, in real time throughout an electrical grid. However, medium and high voltage  measurement equipment is costly and might require network disruptions to be installed.  Using measurements on the lower voltage side of transformers (T/F) – LV for distribution T/F and MV for substation T/F – and relying on a model of its operation can answer both challenges, while serving the monitoring purposes. As you may read in the paper, the MV side behavior of a distribution T/F may be captured through LV measurements with the delay of a mere sample step (e.g. 0.2 ms at 5 kHz rate). Talk about real-time, right?

The bigger picture is that digital twins are purpose-driven. We define the needs of monitoring a phenomenon or range thereof, any challenges in the process, and engineer the infrastructure and the models required in that framework. The essence of digital twins lies in their ability to respond to real-time inputs and adjust the depiction of the asset or phenomenon in real-time, too. Some might say that they resemble a feedback control system, but for the purpose of monitoring.

The term “real-time” here though, is tricky. If the scope of the monitoring is electrical phenomena (e.g. transient faults), then the term implies sub-second detail. On the other hand, if the purpose is equipment ageing, then granularity of months might suffice. That been said, it is the subtext of real-time which is actually more important. The user or control process relying on the digital twin must be informed in-time to act upon the information. In the case of a T/F suffering an uncleared single phase fault to ground, there is a system operator or local utility that must respond and restore full operational capacity after the fault has occurred, yet fast enough. If the insulation of a breaker is nearing its replacement time, a few days (at least) of advance notice are necessary to plan maintenance actions.

At the moment, I am considering another digital twin for overhead transmission lines that are approached by a forest fire and must get disconnected in time. Unlike, the distribution T/F digital twin, the electrical model was not sufficient for the purpose and needed to be enhanced with additional details that made it ever more challenging and interesting. Still it seems to be able to detect the forest fire in sub-second times, thus meeting the monitoring purpose. I hope to be telling you more about it soon.

Active Distribution Seminar at Texas A&M, News

Seminar at Texas A&M on Active Distribution Grids

December 2021

On Friday January 28th, 2022 I will be heading out to Texas A&M to offer a seminar to the Power & Energy Group at the Dept. of Electrical & Computer Engineering. I want to thank Prof. Mladen Kezunovic for the kind invitation and Dr. Birchfield for organizing the seminar. I am excited to talk about how smart grid control and digital twins can enable distribution systems to host greater capacities of renewables, while improving customers’ service by reducing interruption times.

If you are going to be attending or are in the area and want us to talk, reach out to arrange some meeting on that day/afternoon.

Active distribution seminar at NYU, News

Seminar at NYU on Active Distribution Grids

October 2021

I am very grateful to Dr. Yury Dvorkin for honoring me with an invitation to offer an ECE seminar at the Tandon School of Engineering at NYU coming Thursday Oct. 28th! I will talk about how our interest in distribution systems has been revived and, especially, in the challenges these networks face on a daily basis. I will point out the deep-rooted technical issues that remain unresolved when operating a distribution grid and the problematic incentives that have failed to make all end-customers more active within them. The digital twin of distribution transformers for detecting grid faults and the value proposition of hybrid photovoltaic-battery systems behind the meter of residential end-customers are two of the proposals I will discuss to address the aforementioned concerns.

The seminar will be held remotely, but if you are NYU faculty, researcher or student, feel free to reach out to arrange some online meeting on that day/afternoon.

Active distribution seminar at Stevens, News

Seminar at Stevens Institute of Technology on Improving Distribution System Operation

September 2021

I am humbled by Prof. Wu‘s invitation to offer a Research Seminar at the  Dept. of Electrical and Computer Engineering at Stevens Institute of Technology on November 17th. I will be discussing the criticalities in the operation, maintenance and development of the distribution systems in electrical grids. Even though widespread black-outs are infrequent, customers in the US and elsewhere still suffer service interruptions that add up to many hours per year. The reasons lie in the poor monitoring of the distribution system, the limited use cases for distributed generation and storage in practice, and the lack of any resilience proposition. I will go over some of my recent and past works on the digital twin of distribution transformers, improving voltage profiles along feeders and actively controlling behind-the-meter photovoltaics and batteries of residential customers for improving energy costs and reducing line congestion.

The seminar will be held remotely, but I will be delighted to meet virtually with any student, researcher or faculty at Stevens for a one-on-one before or after the seminar. Feel free to reach out to arrange it!