123kV Inductive Voltage Transformer

123kV PT

123kV Inductive Voltage Transformer (IVT), also known as a Potential Transformer (PT) or Voltage Transformer (VT), is a high-voltage instrument transformer designed to accurately reduce transmission system voltages up to 123 kV to standardized low-voltage outputs for metering, protection, monitoring, and control. It provides galvanic isolation between the high-voltage network and secondary equipment, ensuring safe and reliable operation of electrical systems.

Working Principle

A 123kV inductive voltage transformer operates on the principle of electromagnetic induction. The primary winding is connected across the high-voltage system, while one or more secondary windings produce a proportional low-voltage output based on the transformer turns ratio.

Main Components
·High-voltage primary winding
·Metering and protection secondary windings
·Laminated silicon steel magnetic core
·Oil-paper insulation system
·Porcelain or composite silicone rubber insulator housing
·Expansion chamber or bellows (oil-filled types)
·Primary terminal
·Secondary terminal box
·Earthing terminal
·Pressure relief device
·Galvanized steel mounting base

Typical Technical Specifications
·Highest System Voltage: 123 kV
·Rated Primary Voltage: 110 kV or 115 kV
·Rated Secondary Voltage: 100 V, 110 V, 100/√3 V, 110/√3 V
·Frequency: 50 Hz / 60 Hz
·Accuracy Class: 0.1, 0.2, 0.5, 3P, 6P
·Rated Burden: 25–300 VA
·Rated Voltage Factor: 1.2 continuous, 1.5 for 30 s (typical)
·Insulation Level: 230/550 kV (Typical)
·Cooling: Oil Natural Air Natural (ONAN)
·Installation: Outdoor

Applications
A 123kV inductive voltage transformer is widely used in:
·High-voltage transmission substations
·Grid interconnection substations
·Utility switchyards
·Power generation facilities
·Industrial transmission systems
·Wind power substations
·Solar power substations
·Railway electrification substations

Advantages
·High measurement accuracy
·Excellent dielectric performance
·Reliable long-term operation
·High insulation strength
·Low maintenance requirements
·Excellent resistance to environmental conditions
·Suitable for both metering and protection applications

Typical Secondary Outputs
Common secondary voltages include:
·100 V
·110 V
·100/√3 V
·110/√3 V

These outputs are commonly connected to:
·Revenue energy meters
·Protective relays
·Synchronizing relays
·SCADA systems
·Power quality analyzers
·Digital fault recorders
·Automatic voltage regulation (AVR) systems

Common Standards
A 123kV inductive voltage transformer is typically designed and tested according to:
·IEC 61869-3 – Instrument Transformers – Additional requirements for Inductive Voltage Transformers
·IEC 61869-1 – General requirements
·IEEE C57.13 – IEEE Standard Requirements for Instrument Transformers
·IEC 60044-2 (legacy standard, superseded by IEC 61869)

Typical Applications in a 123kV Substation
·Busbar voltage measurement
·Transmission line voltage monitoring
·Revenue metering
·Distance, overvoltage, and synchronization protection
·SCADA and remote monitoring
·Fault recording and disturbance analysis
·Automatic voltage regulation (AVR)
·Power quality monitoring

A 123kV Inductive Voltage Transformer is a critical component in high-voltage substations, providing an accurate and isolated representation of system voltage for protection relays, metering devices, and automation systems. Its high insulation performance, measurement precision, and long service life make it indispensable in modern transmission and power distribution networks.