The Grid is BLIND without CTs

The Grid is BLIND without CTs

by Jordan (The Electric Brit) · View the channel on PSI

Applied Sciences & Engineering Energy THEnergy technology and engineeringTHRElectrical engineering
🎙 Jordan (The Electric Brit) 👥 24K 📅 September 12, 2026 ⏱ 32 min 👁 20 📄 tutorial 🧭 2026-09-12
Available in: English (current) Français

Keywords

CTcurrent transformerprotectioncommissioningpower grid

Summary

The video, presented by Jordan, a UK transmission engineer, offers a comprehensive technical overview of high-voltage AC current transformers (CTs). It starts by explaining the fundamental purpose of CTs: to scale down large primary currents (e.g., 5000 A) to safe, measurable secondary currents for relays and meters, while providing galvanic isolation. The presenter covers CT ratios and the importance of polarity, highlighting that incorrect polarity can cause relay misoperation or failure to trip. He distinguishes between metering and protection CTs, explaining accuracy classes including 0.5, 5P, and PX, and clarifies concepts such as accuracy limit factor (ALF), composite error, and saturation. The role of burden—the impedance of the secondary circuit—is discussed, along with how it affects CT performance and the risk of early saturation. The knee point or excitation characteristic is explained as the saturation limit beyond which accurate measurement fails. Various CT constructions are described: toroidal, bar, bushing, split-core, core balance, summation, air-gapped (transactor), overdimensioned, anti-remanence, and linear CTs, each with their specific applications and trade-offs. The video also covers insulation types (oil and SF6) and associated safety concerns. The testing section demonstrates commissioning procedures: polarity tests using batteries and analog meters, CT analyzer tests (e.g., Omicron) that verify ratio, winding resistance, accuracy, and plot excitation curves, and secondary/primary injection methods to validate the entire secondary circuit up to the relay. The presenter emphasizes real-world pitfalls, like factory mislabeled CTs, and the importance of rigorous testing to ensure protection functions correctly. The video concludes with the idea that CTs are the ’eyes’ of the protection system, and without them the grid would be blind.

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Critical Evaluation

Value of the Information & Strength of the Argument

The video provides valuable, practical insights for protection engineers and electrical engineering students. Its main strength lies in combining theoretical concepts with field experience: the presenter shares anecdotes (mislabeled CTs, blast walls) that illustrate real-world challenges and reinforce the importance of proper testing. The argumentation is clear and logical, progressing from basic operation to advanced specifications and testing. The use of examples, such as the 5000 A primary and the 2500:1 ratio, helps ground the explanation. However, the content is mostly descriptive and does not delve into mathematical derivations or complex fault analysis, so it serves as an excellent introduction rather than a deep theoretical treatment. The presenter’s stance is that CTs are indispensable and that meticulous testing is non-negotiable, a point convincingly supported throughout.

Scientific Rigor, Source Quality, Title Accuracy

The video demonstrates solid technical rigor. The presenter references IEC standards (IEC 60044-1 for composite error, IEC 60044-6 for anti-remanence CTs) and mentions tools like Omicron CT analyzers and primary injection sets (Omicron CPC 100, Megger). He also notes the importance of verifying CT polarity through testing rather than trusting labels. The title ‘The Grid is BLIND without CTs’ is catchy and accurate, effectively summarizing the essential role of CTs in grid protection. While the content is not formally peer-reviewed, it is consistent with established electrical engineering principles. A minor commercial mention of Refoss energy monitoring equipment is made, with transparent disclosure that it is an affiliate link, but this does not affect the technical content. Overall, the title and content align well, and the technical information appears reliable.

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Title / Content Match

The title accurately reflects the core message that CTs are essential for grid protection; without them the protection system is blind. It effectively captures the video's focus.

Quality & Reliability

8/10

The author is a UK transmission engineer with practical commissioning experience. The content aligns with IEC standards (IEC 60044-1, 60044-6) and covers both theory and real-world testing procedures. No obvious factual errors, though it is an informal educational video rather than a peer-reviewed source.

Key Moments

Markers derived by PSI from the transcript: the creator did not define chapters.

Cited Sources

Contribution & Novelties

The video’s novelty lies in its practical, field-oriented perspective on CT testing and commissioning, which is rarely covered in academic texts. It bridges the gap between theoretical standards and actual substation work, sharing experiences like factory polarity mislabels and the use of blast walls around failing CTs. This fills a niche for engineers seeking realistic insights. The presentation of various CT types—including less common ones like transactors and anti-remanence CTs—provides a broad survey that is both instructive and engaging.

Pour aller plus loin :

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Radar Profile

The radar profile shows high scores across all dimensions, indicating a well-rounded educational resource. The strongest points are the quantity and quality of information, with slightly lower but still respectable scores for technical level and reliability, reflecting the informal yet expert nature of the content.

Reliability 7/10