—T EC H N I C A L A R T I C L E The future of primary metering solutions CVC combination current and voltage transformers A CVC combination unit combines a current transformer and a voltage transformer into a single device, making installation and maintenance easier. Suitable for a variety of applications, CVC units are sure to become a staple in primary metering applications. In an increasingly power-hungry world, utilities and industry are on a continual quest for increased efficiency and cost effectiveness. From power transmission to distribution, there is almost no end to the number of strategies that can be followed. In this paper, we will focus on primary metering applications and the advantages offered by CVC “combo” units. Easier installation and maintenance A CVC (Current Voltage Combination) unit consists of a current transformer (CT) and a voltage transformer (VT) combined into one device, offering a compact solution for accurately measuring network electrical parameters. This integrated approach to measuring medium voltage characteristics provides several benefits. First, CVC units significantly reduce complexity. In practical terms, eliminating complexity reduces the chance of mistakes, offering benefits from procurement to maintenance to asset management. When using a CVC unit, only one unit needs to be ordered and stocked instead of two. Similarly, if the units are used for three- phase primary metering applications, only three units are needed instead of six. A single unit also reduces the physical space required to receive and store the equipment, making handling and processing less complex and error prone. Second, there is a practical cost savings realized with a CVC unit. Installing a single unit reduces the time and labor required to mount the unit on a rack for pole-mount applications or inside a cabinet for padmounted applications. In most instances, instrument transformers are mounted in a three-phase configuration, meaning each of the phases has a dedicated CT and VT. Each medium voltage CT has two primary terminals and medium voltage VTs have one primary terminal. Conversely, a CVC unit only has two — 01 CVC combination units halve the number of components required, allowing for faster, easier installation in space- constrained areas. primary terminals, which reduces the number of primaries and taps that need to be connected to the distribution network. Secondary wiring is also simplified due to wiring only one junction box per phase instead of two. In an illustrative example, installing a CVC unit in place of a CT/VT within a pole-mounted rack takes an estimated 25%-30% less labor to mount, wire and test. Depending on loaded labor rates and reduction of other materials, this could be a savings of between $500-$750 per rack. The compact design also takes up less space, a considerable advantage in the often-crowded environments of electrical substations or distribution points, especially inside of padmounted primary metering cabinets where the size of the cabinet can then be reduced. This saves material costs related to the cabinet manufacture as well as reduces the footprint of the cabinet. Fewer space constraints remove mounting restrictions, allowing the units to be installed upright instead of in a horizontal or cantilever position, making them easier to bolt onto the frame. Mounting all units upright also removes the challenge and potential safety risk of installing CTs and PTs cantilever or inverted. Third, with fewer connections and components to inspect, maintenance is simplified. In traditional separate installations, each CT and VT requires individual attention. However, with a CVC unit, maintenance checks can be performed more quickly and efficiently, as there is only one device to inspect. ABB’s CVC units are also pre-calibrated and designed with standardized fittings and connectors, making it quicker to replace or upgrade components as necessary. Empowering the transition to renewables Since their initial introduction into the United States more than a decade ago, CVC units have continued to evolve to meet the needs of today’s power grid requirements, particularly in renewables applications. Two primary advancements warrant special attention. Units with high accuracy and extended range mean that the unit can accurately measure a wider range of current levels, which allows for higher accuracy and flexibility in metering applications with a wide load swing. This is particularly beneficial in applications involving renewable energy where energy generation can depend on time of day, weather patterns, or other conditions. — 01 For example, ABB’s AccuRange® current transformers offer high accuracy at both low and medium voltage levels. Combining an AccuRange CT with an ABB voltage transformer in a CVC unit allows the part number to be specified in a broad spectrum of applications, such as wind, solar, and hydropower. The high accuracy helps maximize revenue by reducing metering losses in renewable applications, while the increased suitability to different applications further decreases part numbers and inventory requirements. ABB introduced transformers with ResiVolt™ technology that offer the ability to withstand a very fast transient (VFT) voltage impulse and provide superior withstand capability against steep wave power network transients that are common in these applications near reclosers, inverters, and other switching devices. By delivering increased reliability at these critical connection points, CVC units equipped with ResiVolt technology are better suited to meet the dynamic demands of renewable energy applications. Increased reliability for outdoor applications Some CVC units have been constructed using polyurethane, but many newer units now offer an HCEP casing. HCEP (Hydrophobic Cycloaliphatic Epoxy) is a class of epoxy resin distinguished by its exceptional hydrophobic properties and robust structure, making it an ideal material for outdoor applications. Overall, reducing the corrosive and conductive effects of water, pollutants, and other environmental impacts contributes to lower maintenance requirements and extends the operational lifespan of the unit. Consequently, HCEP CVCs offer a more dependable solution for power distribution in challenging outdoor conditions, where exposure to pollution and adverse weather is a constant concern. This enhances the overall safety and efficiency of electrical systems. Grid hardening introduces new challenges Ferroresonance, or nonlinear resonance, occurs in electrical circuits when a nonlinear inductance and system capacitance interact, especially under conditions like the opening of a switch or other disturbances. This phenomenon can lead to overvoltages and overcurrents within the power system, presenting various operational challenges. IEEE C57.13 standard for Instrument Transformers The IEEE C57.13 standard defines requirements for electrical, dimensional, and mechanical characteristics of instrument transformers used in the measurement and control of electrical systems. This standard helps ensure operational accuracy, safety, and reliability. For CVC units, following the IEEE C57.13 standard means that these devices meet specified requirements for performance under various electrical conditions. The standard details critical factors such as the insulation and accuracy classes necessary for safe and efficient operation in diverse power systems environments. ABB CVC units are manufactured in the United States, and although we serve customers worldwide, we are committed to ensuring adherence to the latest standards. — We reserve the right to make technical changes or modify the contents of this document without prior notice. With regard to purchase orders, the agreed particulars shall prevail. ABB Inc. does not accept any responsibility whatsoever for potential errors or possible lack of information in this document. We reserve all rights in this document and in the subject matter and illustrations contained therein. Any reproduction, disclosure to third parties or utilization of its contents – in whole or in parts – is forbidden without prior written consent of ABB Inc. Copyright© 2025 ABB All rights reserved — ABB Inc. 305 Gregson Drive Cary, NC 27511 electrification.us.abb.com 9AKK108470A9793 REV A APRIL 2025Changes to the power grid, such as the modernization of electrical infrastructure with components that introduce nonlinear inductances and the expanded use of capacitor banks for power factor correction and voltage regulation, are designed to improve grid resiliency. However, they also increase the likelihood of ferroresonance, high-frequency impulses, harmonics, and other types of voltage anomalies. Furthermore, as the power grid evolves to integrate more renewable energy sources, the complexity of these interactions within the grid increases, raising the risk of contributing destabilizing conditions that are potentially disruptive to the network. More specifically, the challenges associated with ferroresonance are significant. This condition can cause excessive voltages, which may lead to the failure of electrical equipment, disrupt the stability of the power supply, and pose potential safety hazards to infrastructure and personnel. Moreover, ferroresonance can result in sustained overvoltage oscillations that are difficult to predict and manage, necessitating specific design considerations and protection schemes to mitigate its impact on the power grid’s operation. At ABB, we’re working with customers to overcome the challenges of ferroresonance on the grid. First introduced in power transformers, this new core and winding technology will be used in all new CVC units to make them more resistant to these types of challenges in the distribution grid. Preparing for the grid of the future At ABB, we talk about future-proofing the grid, and addressing the ferroresonance challenge is a great example. So are the features built into our lineup of CVC combination units, designed to handle increased variability and load from renewable power sources. But as difficult as it was to predict what the needs of today’s grid would be when we introduced the first CVC units 15 years ago, it is even more challenging to predict what tomorrow’s grid will require. Rest assured, our engineers are committed to — and are addressing — the challenge.