36kV Voltage Transformer (Indoor type)

36kV Voltage Transformer

36kV Indoor Voltage Transformer (VT), also known as an Indoor Potential Transformer (PT), is an instrument transformer designed to accurately step down medium-voltage system voltages up to 36 kV into standardized low-voltage outputs for metering, protection, monitoring, and control. These transformers are widely installed in indoor metal-clad switchgear, substations, and industrial power distribution systems.

Main Functions
·Voltage Measurement: Converts high primary voltage to standardized secondary voltages (typically 100 V or 110 V) for measuring instruments and revenue metering.
·Protection: Provides accurate voltage signals to protection relays for overvoltage, undervoltage, directional, synchronization, frequency, and distance protection.
·Electrical Isolation: Electrically isolates secondary measuring and protection circuits from the high-voltage network, ensuring personnel and equipment safety.

Typical Applications
·Indoor medium-voltage switchgear
·Utility substations
·Industrial substations
·Ring Main Units (RMUs)
·Commercial buildings
·Renewable energy plants (wind and solar)
·Mining, oil & gas, and heavy industries
·Railway traction power systems

Typical Technical Specifications
·Rated Voltage: 36 kV
·Highest System Voltage: 36 kV or 40.5 kV
·Rated Frequency: 50 Hz / 60 Hz
·Rated Primary Voltage: 33 kV, 35 kV, 36 kV, or 33/√3 kV
·Rated Secondary Voltage: 100 V, 110 V, 100/√3 V, 110/√3 V
·Accuracy Class: 0.1, 0.2, 0.5, 1.0, 3P, 6P
·Rated Burden: 10 VA, 15 VA, 30 VA, 50 VA, 100 VA
·Insulation Type: Vacuum-cast epoxy resin
·Cooling Method: Natural Air (AN)
·Installation: Indoor

Construction
A typical 36kV indoor voltage transformer consists of:
·High-voltage primary winding
·One or more secondary windings
·High-grade laminated silicon steel core
·Vacuum-cast epoxy resin insulation
·High-voltage terminal
·Secondary terminal box
·Mounting base
·Earthing terminal

The epoxy resin encapsulation provides:
·Excellent dielectric strength
·High mechanical robustness
·Moisture and contamination resistance
·Low partial discharge
·Maintenance-free operation
·Long service life

Common Types
·Single-phase inductive voltage transformer
·Double-pole insulated voltage transformer
·Three-pole insulated voltage transformer
·Withdrawable (plug-in) voltage transformer
·Fuse-protected voltage transformer
·Dual-secondary voltage transformer (metering and protection)

Advantages
·High measurement accuracy
·Excellent insulation reliability
·Compact design suitable for metal-clad switchgear
·Maintenance-free throughout its service life
·High resistance to humidity, dust, and pollution
·Low partial discharge characteristics
·High thermal and mechanical strength
·Reliable long-term performance

Applicable Standards
·IEC 61869-1 – Instrument Transformers – General Requirements
·IEC 61869-3 – Additional Requirements for Inductive Voltage Transformers
·IEEE C57.13 – IEEE Standard Requirements for Instrument Transformers

Typical Wiring
Primary Side
·Connected phase-to-phase or phase-to-earth on a 33–36 kV medium-voltage system.

Secondary Side
·Energy meters
·Voltmeters
·Protection relays
·Power quality analyzers
·SCADA and automation systems
·Synchronizing equipment

Typical Applications by Industry
·Utility Substations: Revenue metering and feeder protection
·Industrial Plants: Transformer, motor, and feeder protection
·Commercial Buildings: Medium-voltage distribution monitoring
·Wind Farms: Collector system voltage measurement
·Solar Power Plants: Inverter and feeder monitoring
·Mining: Distribution switchgear and process power
·Oil & Gas: Medium-voltage process power systems
·Railway Systems : Traction substation voltage measurement

Key Features
·Rated system voltage up to 36 kV
·Suitable for systems with a highest voltage of 40.5 kV
·Indoor epoxy resin cast insulation
·High dielectric strength and low partial discharge
·Accurate voltage transformation for metering and protection
·Multiple secondary winding configurations available
·Compact, lightweight, and maintenance-free design
·Fully compliant with IEC 61869-1, IEC 61869-3, and IEEE C57.13 standards