High Voltage Eye Bolt Type Current Transformer · 36kV–245kV

High Voltage Eye Bolt Type Current Transformers

A high voltage eye bolt current transformer (HV eye bolt CT) transforms primary currents up to 4000A into standardised 1A or 5A secondary outputs for revenue metering, relay protection, and current monitoring. It is available across voltage classes from 66 | 69 | 110 | 115 | 132 | 138 | 150 | 154 | 161 | 220 kV up to 245 kV, including 132kV / 220kV current transformer for substation applications. Built as a high voltage current transformer for outdoor duty, it uses oil impregnated paper (OIP) with condenser-graded (capacitive) OIP insulation for uniform voltage stress distribution, available with polymer or porcelain external insulation and nitrogen-free SS bellows for oil volume variation. In this eye-bolt design, the primary conductor is bent into a U-shape (hair-pin construction) and passed through the cores within a tank-type construction, without compromising the unit's insulation systems or sealing integrity. This makes it well suited for integration with relay protection networks across substations operating under harsh outdoor environmental conditions.

As a trusted manufacturer of Outdoor Instrument Transformers, Straton Electricals engineers every Eye bolt type CT to IEC 61869-1 & 2 / IS 16227 standards for reliable performance across India's power infrastructure. Manufactured in Hyderabad, India, Straton Electricals' certifications and approvals include CPRI type-tested current transformers, ERDA approval, and approved-vendor status with APTRANSCO and TGTRANSCO.

High Voltage Eye Bolt Type Current Transformers

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Certifications

Certified and Approved For

CPRI
Type-Tested
ISO 9001:2015
Certified
ISO 14001:2015
Certified
IS 16227
Compliance
IEC 61869-1 & 2 / IS 16227 IEC 61869-1 & 2 /
IS 16227
ERDA
Approved
APTRANSCO Approved APTRANSCO
Approved
TGTRANSCO Approved TGTRANSCO
Approved
Technical Specifications

High Voltage Eye Bolt Type Current Transformers: Technical Specifications

InstallationOutdoor
DesignEye-Bolt Type
InsulationOil-Impregnated Paper (OIP)
System Voltage66 | 69 | 110 | 115 | 132 | 138 | 150 | 154 | 161 | 220 kV up to 245 kV
Primary CurrentUp to 4000 A
Secondary Current1 A or 5 A
Number of CoresUp to 5 cores (Metering + Protection)
Accuracy ClassMetering: 0.2S / 0.2 / 0.5S / 0.5 / 1 · Protection: 5P / 10P / PS
Rated Burden5 VA to 30 VA per core
Short-Time Thermal Current (Ith)Up to 63 kA for 1 s / 3 s
Dynamic Peak Current (Idyn)2.5 × Ith
External InsulationPolymer or Porcelain
Primary CasingAluminium Casing
HousingAluminium or MS Fabricated
Housing FinishHot-Dip Galvanized or Polyurethane Paint
Oil Volume CompensationNitrogen-Free SS Bellows
Partial DischargeFree up to power-frequency withstand voltage*
Thermal Stability TestingAvailable as per customer requirements
Temperature Coefficient TestingAvailable as per customer requirements
Secondary TerminalsStud-Type DIN Terminals
StandardsIEC 61869-1 & 2 / IS 16227 (Part 1 & 2)
WarrantyUp to 3 Years*
DeliveryWithin 2–3 Weeks*
Product Types

HV Eye Bolt Current Transformer: Product Series & Technical Variants

As part of a comprehensive high-voltage CT series, the eye-bolt current transformer range is engineered as an industrial current-transformer solution for air-insulated substations and outdoor deployments across varying voltage classes. Each variant in this switchyard CT lineup is built with the same core insulation and mounting design, scaled to suit different transmission voltage levels within a utility power system.

As a trusted Instrument Transformer Manufacturer, Straton Electricals manufactures each series on ISO-certified production lines, with in-house dielectric and routine testing carried out before dispatch to ensure every unit complies with IEC 61869-1 & 2 / IS 16227. This utility metering transformer range has been deployed across utility and EPC projects, supporting reliable current sensing within demanding transmission protection network environments.

066OC-E

Designed for 66kV class outdoor switchyards requiring compact, reliable current sensing.

110OC-E

Built for 110kV class networks, offering stable metering and protection performance.

132OC-E

Engineered for 132kV class installations across regional transmission and distribution networks.

220OC-E

Rated for 220kV class systems, built to handle higher fault currents at major transmission and grid interconnection points.

Key Features

Eye Bolt High Voltage CT: Key Features

Accurate current transformation up to 4000 A with reliable current ratio configuration
Standard secondary outputs of 1A or 5A for compatibility with metering and protection equipment
Designed and tested in compliance with IEC 61869-2 current transformer standards (IEC 61869-1 & 2 / IS 16227), aligned with recognised electrical transformer standards
Built as a reliable OIP CT (oil impregnated paper current transformer) suited for demanding outdoor substation applications
Eye-bolt (hair-pin) type primary construction, with the primary conductor passed through the cores in a compact tank design, built for high short-time current withstand and reliable outdoor performance
Partial discharge-free insulation system supporting effective partial discharge control and long-term dielectric insulation reliability
Nitrogen-free stainless-steel bellows for thermal expansion compensation across varying outdoor conditions
Available with porcelain or polymer external insulation to suit diverse outdoor transformer parameters
Custom CT ratio and burden configurations available for utility and EPC project requirements, supporting seamless relay protection integration
Available in CT ratios such as 400–200/1-1-1A to suit metering and protection needs
BIL ratings up to 650 kVp (132kV) and 1050 kVp (220kV) for reliable insulation performance
Voltage Ratings: 66 | 69 | 110 | 115 | 132 | 138 | 150 | 154 | 161 | 220 kV up to 245 kV

As a utility grade current transformer, the eye bolt HV CT range complements Straton Electricals' broader current transformer portfolio, including High Voltage Wound Type Current Transformers, offering utilities and EPC contractors flexible options across different HV CT technical features and system requirements.

Applications

High Voltage Eye Bolt Type Current Transformers: Applications

High voltage eye bolt current transformer applications span electrical grid infrastructure, supporting HV current transformer use cases as a dependable outdoor utility CT, complementing Straton Electricals' High Voltage Rigid Bar Type Current Transformers for heavier-duty needs.

Transmission & Distribution (T&D) Substations
High-Voltage Switchgear (AIS & GIS)
Utility Power Transmission Networks
Renewable Energy Plants (Solar, Wind & Hybrid)
Industrial Power Distribution Systems
Power Generation Plants
Protection Relay & Control Systems
Revenue & Energy Metering
Smart Grid Infrastructure
Grid Monitoring and Power Quality Applications

Eye Bolt Type CT vs Rigid Bar Type CT

The table below highlights the key differences between eye bolt type and rigid bar type current transformers across primary conductor configuration, construction, and typical application areas.

Parameter Eye Bolt Type CT Rigid Bar Type CT
Primary Conductor U-shaped (hair-pin) construction Straight busbar-type conductor
Construction Compact tank design Rigid, fixed bar through core window
Primary Resistance Low Higher, due to bar geometry
Short-Time Current Withstand High High, suited to heavy-duty ratings
Installation Flexibility Better conductor routing flexibility Limited routing; mechanically rigid
Typical Application Outdoor substations, varying voltage classes Heavy-duty, direct switchgear integration

Both configurations support accurate electrical measurement, metering, and protection within a power distribution system, with selection driven by primary conductor configuration and substation layout requirements.

FAQ

Frequently Asked Questions

In an eye-bolt type current transformer, the primary conductor is bent into a U-shape (also called hair-pin construction) and passed through the cores within a tank-type design, offering strong short-time current withstand and stable insulation performance.
They are typically available for voltage classes ranging from 66 | 69 | 110 | 115 | 132 | 138 | 150 | 154 | 161 | 220 kV up to 245 kV and above, depending on system requirements.
They provide reliable insulation performance, accurate metering, fault monitoring, and long service life in outdoor environments.
Most high voltage CTs comply with IEC 61869-2 current transformer and IS standards for electrical safety, metering accuracy, and protection performance.
They support relay protection, current monitoring, and safe energy transmission across utility infrastructure systems.
Common insulation technologies include oil impregnated paper (OIP) with condenser-graded (capacitive) OIP insulation, offering excellent uniform voltage stress distribution and widely used in high-voltage outdoor CTs.
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Technical Datasheet

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GA Drawing

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Type-Test Summary

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