Metrosil is a product of M&I Materials, manufactured in Manchester, UK and has a strong history in electrical engineering.
At Metrosil, we prioritise safety, reliability, and adherence to industry standards in our product designs. Our Current Transformer Protection Units (CTPUs) are meticulously engineered to comply with the requirements set forth by the Institute of Electrical and Electronics Engineers (IEEE).
Metrosil is the original CTPU device known for its exceptional performance and reliability. Metrosil CTPUs offer an extremely fast transient response, high thermal conductivity, and low residual leakage current. They experience no degradation over time and boast an impressive service life of 30+ years. Our reputation as the pioneer of CTPU devices underscores our commitment to quality. Not all SiC varistors are the same and some copies of the original Metrosil CTPU do not adhere to their specifications when subject to type testing so beware of imitations!
Understanding IEEE Standard C57.13-2008
The IEEE establishes rigorous standards to ensure the safe and efficient operation of electrical equipment. The IEEE C57.13-2008 standard specifically addresses the protection of instrument transformers, section 6.7.1 emphasises the following key requirements:
- Avoiding Open Secondary Circuits: Instrument transformers should never be operated with the secondary circuit open because hazardous crest voltages may result.
- Emergency Conditions: Transformers conforming to this standard shall be capable of operating under emergency conditions for 1 minute with rated primary current times the rating factor with the secondary circuit open if the open-circuited voltage does not exceed 3500V crest.
- Voltage Limiting Devices: When the open-circuit voltage exceeds 3500V peak, the secondary winding terminals should be provided with voltage limiting devices (varistors or spark gaps.)
- Device Durability: The voltage limiting devices should be able to withstand an open-circuit situation for a period 1 min without damage to the secondary circuit. The voltage limiting device may need to be replaced.
Metrosil CTPUs: Designed for Compliance and Superior Performance
- Full Compliance with IEEE C57.13-2008: Metrosil CTPUs are designed to not only meet but exceed the above standard. Silicon carbide varistor based units are engineered to adhere strictly to section 6.7.1 of the IEEE C57.13-2008 standard, providing reliable voltage limiting to prevent hazardous crest voltages.
- Protection Against Insulation Damage: Metrosil CTPUs provide very fast acting overvoltage clamping, protecting the insulation of CTs and preventing damage and potential fire caused by this condition and enhancing longevity of the operation of the CT and its connected asset.
- Maintaining Characteristics: Unlike other voltage limiting devices, Metrosil CTPUs do not alter their characteristics, even under prolonged heat cycles.
- No Electromagnetic Interference: Our units are designed to operate without creating electromagnetic interference.
- Optional Metrosil CTPU Enclosures: Our factory pre-wired CTPU enclosures offer flexible fitting options, are certified to IEC 61439 Parts 1 and 2 and are CE compliant.
The Metrosil division at M&I Materials is factory audited by major electrical OEMs and are awarded:
- GE Vernova ‘Class A’ Supplier,
- Siemens Energy ‘Class A’ Supplier,
- ABB/Hitachi Energy ‘Critical Supplier Status’
These are accolades that M&I Materials are extremely proud to hold.
Advantages Over Traditional Spark Gaps
While traditional spark gaps are also used for voltage limiting, Metrosil CTPUs offer several distinct advantages over this technology:
- No Immediate Replacement Required: Unlike spark gaps, which often need immediate replacement after an overvoltage event, Metrosil CTPUs remain operational and do not require user intervention following an open circuited fault condition.
- Enhanced Durability: Metrosil CTPUs can withstand many heat cycles and open-circuit conditions without degradation for days, ensuring long-term reliability and consistent performance. This exceeds the IEEE standard.
Metrosil CTPU testing
We conduct extensive testing for our CTPUs. For Metrosil CTPUs we use a custom test circuit for condition testing devices (please see image 1) We test our CTPUs by replicating the in-application protection condition, we commissioned this equipment to allow us to re-create the same open circuit, real world fault condition our Metrosil CTPUs would experience. We are the only supplier to uniquely provide this.
Our extensive testing has revealed numerous benefits of Metrosil CTPUs including:
- Metrosil CTPU’s maintain their ratings over time.
- Metrosil shows no temperature peaks during testing.
- Superior construction using high quality materials and components.
- Metrosil CTPUs do not incur damage to varistor discs and assemblies during heat-cycling and ageing tests.
These results underscore the superior performance and reliability of Metrosil CTPUs.
Conclusion
Our dedication at Metrosil, and adhering to IEEE standards, particularly in our CTPUs, underscores our commitment to providing safe, reliable, and efficient overvoltage protection for electrical power systems. By choosing Metrosil CTPUs, you ensure that your electrical assets not only comply with industry standards but also benefit from our advanced protection and reduce your maintenance requirements.
We’re here to help! For more detailed information on our CTPUs and how they can benefit your operations, visit our website or contact our team of experts.
For a detailed step by step guide to selecting the correct Metrosil CTPU for your CT, please follow the link below:
https://metrosil.com/wp-content/uploads/2023/02/CTPU-Data-Sheet-1.pdf
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