Demystifying Current Transformers (CTs): A Beginner’s Guide

Are you curious about the hidden mechanics behind electrical power measurement? Perhaps you've heard the term "current transformers" but aren't quite sure what they are or how they work. Fear not! In this beginner's guide, we'll unravel the mysteries surrounding current transformers (CTs), exploring their principles of operation, construction, and performance characteristics.

Understanding Current Transformers (CTs)

At its core, a current transformer is a specialised device that measures electric current in power systems. Unlike conventional transformers, and I don't mean the toy, CTs don't directly connect to the circuit being monitored. Instead, they work on the principle of electromagnetic induction to produce a secondary current proportional to the primary current flowing through the conductor they encircle.

How They Work

Imagine a miniature transformer tailored to scale down (transform) high currents into manageable levels for measurement and protection purposes. CTs typically consist of primary and secondary windings and protection(e.g. 2000A Primary to 1A Secondary typically shown as 2000/1A) wound around a magnetic core. As the primary current flows through the conductor encircled by the CT, it induces a corresponding secondary current in the secondary winding, maintaining a proportional relationship.

Exploring Construction

Delving deeper, let's peek inside the construction of a CT. The primary winding, typically a single turn or a few turns of a conductor, carries the current to be measured. Surrounding this primary winding is the secondary winding, which generates the scaled-down current output. The core, usually made of Grain-Oriented Silicon Steel (GOSS), enhances the magnetic coupling between the windings.

Performance Characteristics

CTs exhibit various performance characteristics critical to their effectiveness. Accuracy, burden, ratio, and saturation are key factors to consider. Accuracy refers to how closely the secondary current matches the primary current. Burden signifies the load imposed on the secondary winding by connected devices. The ratio determines the transformation ratio between primary and secondary currents. Saturation occurs when the core reaches its magnetic limits, affecting accuracy at high currents.

Why It Matters

Understanding CT fundamentals is essential for anyone involved in electrical engineering, power systems, or even those intrigued by the world of electricity. CTs play a vital role in power monitoring, equipment protection, and maintaining the stability of electrical systems. By grasping their basics, you embark on a journey toward mastering the intricacies of electrical power measurement.

Ready to Learn More?

This beginner's guide is just the tip of the iceberg when it comes to current transformers. Stay tuned for upcoming posts where we'll delve into advanced topics and practical applications. Remember, every expert was once a beginner. Embrace your curiosity, and let's unravel the wonders of current transformers together!

#ElectricalEngineering #PowerMeasurement #CurrentTransformers #BeginnersGuide #LearningJourney #UnderstandingElectricity #ITL-UK #ITL #InstrumentTransformersLimited

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The European Union (EU) Has Released A Report On The Replacement Of The SF6 Gas In Switchgear

On September 30, 2020, the EU released a detailed report outlining alternatives to SF6 for use in switchgear and related equipment.
You can find full EU report from this link : https://ec.europa.eu/clima/sites/clima/files/news/docs/c_2020_6635_en.pdf
The report also extensively covers market impact and cost issues. This is the latest in a series of indications that the pressure is on to phase out SF6, as part of the EU’s mission to cut harmful greenhouse gas (GHG) emissions by two-thirds between 2014 and 2030. Replacing SF6 would be a significant contribution by the energy distribution industry as it the biggest GHG contributor for this sector.

Environmental Issues SF6 gas:

The September 2020 EU report forms part of the EU’s review of the F-Gas Regulation, which is in a public consultation period until the end of December 2020, and EU Commission adoption is planned for the fourth quarter of 2021. Tighter regulation around SF6 in the energy industry is one of the expected outcomes.

Even before the September 2020 report, the spotlight was already on SF6, for instance it is listed in the Kyoto Protocol. With a global warming potential (GWP) of 23,500, SF6 is considered the most potent of greenhouse gases. A recent study by the University of Antwerp (5) also suggests that reported SF6 emissions are underestimated and provides a projection of potential CO2 equivalent savings for a SF6 phase out, using the example of 145kV gas insulation switchgear (GIS).

SF6 gas alternatives:

Given that evaluating and implementing alternatives will take several years for an energy provider, there is no time to lose. The biggest challenge is to find a solution that lives up to SF6’s performance legacy, as well as meeting environmental requirements. The good news is that through the collective R&D of experienced switchgear manufacturers and other experts, today power utilities have several alternatives to SF6.

There are three main alternative approaches to SF6 replacements in play today: based on 3M Novec 5110 Insulating Gas which is a C5-Fluoroketone; based on 3M Novec 4710 which is a C4-Fluoronitrile; and dry air based in combination with a vacuum interrupter. These are all outlined in the EU report, as well as another report published in February 2020, by T&D Europe (6), the European association of the electricity transmission and distribution equipment and services industry.

For more infomation about SF6 alternative gas in switchgears please see this article.

Switchgear Manufacturers Pushing the Boundaries:

Switchgear manufacturers behind these alternatives continue to push the boundaries of what is possible and nearly all of them have also responded to the EU roadmap for the F-gas revision with detailed proposals for an SF6 phase out.

In addition, some manufacturers have also published their development road map or objectives to extend their SF6-free portfolio.

GE Grid Solutions is using a gas mixture based on 3M Novec 4710 Insulating Gas in its g3 (pronounced “g cubed”) technology. GE has announced a g3 roadmap until 2025 to extend its SF6-free portfolio up to 420kV which also includes an EU Life funded project.

AirPlus is a gas mixture using Novec 5110 Insulating Gas from 3M and is used by ABB in MV equipment, and by Hitachi ABB Power Grids in HV equipment. ABB has also announced its objective that up to 90% of its GIS portfolio variants will be SF6 free. Hitachi ABB Power Grids has an ongoing project with German utility TransnetBW to upgrade a 380kV substation with its eco-efficient, SF6 free technology.

Additional switchgear manufacturers, such as Siemens Energy and Schneider Electric, have made similar announcements expanding their SF6 -free portfolios.

Regardless of the chosen approach to replacing SF6, the EU report estimates that — depending on the voltage class — a full commercialization of alternative solutions is already realistic after a transition period of two to five years, for example for MV, and for HV GIS up to 145kV. The report also evaluates potential cost increases and concludes that “in general, where the SF6-free alternatives are more costly than switchgear containing SF6, policy intervention is likely to be needed to trigger a transition.”

In the meantime, switchgear manufacturers will continue to develop SF6 replacements beyond current voltage levels, and as the clock is ticking, now is the time for utility companies to start planning for an SF6-free future. After all, rather than wait to be forced to act, it is better to have sufficient time to evaluate alternatives and phase-out strategies, in the interests of utility firms and the planet alike.

Source: T&D world website & Switchgearcontent.com