Medium Voltage Instrument Transformers

Medium Voltage Instrument Transformers are core sensing and measuring units for 10–17.5kV power distribution systems. They accurately step down high currents and voltages into standard low-level signals for energy metering, system monitoring and protective relaying. Serving as vital links between high-voltage power circuits and low-voltage control systems, they comply with international standards and provide solid data support for safe, efficient and stable grid operation.

Primary Field Applications

Metering and Protection Circuits in Outdoor Substations

Installed in metering and protection loops of 10–17.5kV outdoor substations, they collect current and voltage signals synchronously to meet high-precision energy metering requirements. Fully compliant with IEC 60044-1 and ANSI C57.13, they achieve highly precise and stable data collection for power billing and grid operation management.

Protection Circuits for Distribution Lines and Equipment

Applied to protection circuits of medium-voltage distribution lines, power transformers and capacitor banks, these transformers withstand a rated short-time thermal current of 80In for 1 second and a rated dynamic current of 2.5×80In. They rapidly capture fault signals to support overload and short-circuit protection for power equipment.

Accessory for Outdoor Electrical Equipment

Customized as matching integrated components for outdoor pole-mounted switches, ring main units and other outdoor power equipment, they are equipped with CPE-type outdoor wall bushings. This structure enables stable outdoor operation without additional protective housings or auxiliary structures.

Space-Constrained Compact Distribution Installations

Ideal for space-limited compact distribution stations and box-type substations, these integrated cast-type transformers combine 3CT and 3PT into a single unit to greatly reduce installation space. With a 600V terminal insulation level, they fit perfectly in densely arranged power equipment layouts.

Compelling Technical Advantages

Medium-voltage instrument transformers feature five prominent technical strengths, making them ideal products for modern medium-voltage distribution networks:

Integrated Design Saves Space and Reduces Costs

The all-in-one cast structure integrating 3CT and 3PT eliminates separate installation of current and voltage transformers. It effectively minimizes installation space, simplifies on-site wiring and reduces overall project construction costs.

Superior Outdoor Adaptability and Operational Reliability

Adopting high-performance cast resin insulation with an insulation level of 17.5/38/95kV, they offer excellent weather resistance and are suitable for direct outdoor installation. They can withstand severe thermal and electrodynamic impacts caused by short circuits, featuring an ultra-low long-term failure rate.

Exceptional Overload Capacity for Complex Operating Conditions

They support continuous operation at 120% of rated current (1.2In), and can operate under 130%~150% rated current overload for up to 8 hours. Excellent overload adaptability meets frequent load fluctuation demands of modern distribution networks.

Dual Reliability for Measurement and Protection Functions

With an instrument security factor of FS=5 and a stable secondary winding voltage of 3kVef, they ensure precise signal transmission. They satisfy high accuracy standards for energy metering and output reliable tripping signals for protection devices. Fully compliant with IEC 61869-1 and IEC 61869-4, they feature wide compatibility with global grid facilities.

Easy Installation, Low Maintenance, Long Service Life

Their compact pre-calibrated design requires no complex on-site commissioning and allows outdoor installation without extra protection. The cast resin enclosure provides excellent moisture-proof, dust-proof and anti-aging performance, requiring almost no routine maintenance. Only regular visual inspections are required to ensure long-term stable operation, delivering high practicality and cost-effectiveness.