245kV Capacitor Voltage Transformer

245kV CVT

245kV Capacitor Voltage Transformer (CVT), also known as a Capacitive Voltage Transformer or Capacitor Potential Transformer (CPT), is an extra-high-voltage (EHV) instrument transformer used in 220kV-class transmission systems to reduce high system voltage to standardized low-voltage outputs for metering, protection, control, synchronization, and power system automation.

A 245kV CVT combines a capacitive voltage divider with an intermediate electromagnetic transformer unit to provide accurate voltage transformation, electrical isolation, and reliable operation in high-voltage transmission substations.

Working Principle
A 245kV CVT operates through two main stages:
1. Capacitive Voltage Divider
The high transmission voltage is reduced by a series capacitor divider:
·C1 – High-voltage capacitor section
·C2 – Low-voltage capacitor section

2. Intermediate Transformer
·The intermediate transformer converts the divided voltage into standard secondary voltage outputs required by protection and measuring devices.

Main Components
·High-voltage capacitor stack
·Capacitive voltage divider unit
·Intermediate transformer
·Compensation reactor
·Ferroresonance suppression circuit
·Damping resistor network
·Oil-paper insulation system
·Porcelain or composite silicone rubber insulator
·High-voltage terminal
·Secondary terminal box
·Grounding terminal
·Oil expansion chamber
·Mounting support structure

Typical Technical Specifications
·Highest System Voltage: 245 kV
·Rated Primary Voltage: 220 kV or 230 kV
·Rated Secondary Voltage: 100 V, 110 V, 100/√3 V, 110/√3 V
·Frequency: 50 Hz / 60 Hz
·Accuracy Class: 0.2, 0.5, 1.0, 3P, 6P
·Rated Burden: 25–500 VA
·Voltage Factor: 1.2 continuous, 1.5 short time
·Insulation Level: 460/1050 kV (Typical)
·Installation: Outdoor
·Insulation Type: Oil-paper / composite insulation

Applications
A 245kV CVT is widely used in:
·220kV transmission substations
·Extra-high-voltage switchyards
·Utility grid substations
·Power generation plants
·Renewable energy transmission stations
·Industrial EHV substations
·HVDC converter stations (AC side)

Main Functions
1. Voltage Measurement
Provides accurate voltage signals for:
·Revenue metering
·Energy management systems
·Digital meters
·Power quality monitoring

2. Protection Applications
Provides voltage inputs for:
·Distance protection
·Overvoltage protection
·Undervoltage protection
·Synchronizing protection
·Auto-reclosing systems
·Fault recording equipment

3. Power System Communication
Many CVTs can support:
·Power line carrier (PLC) coupling
·Teleprotection communication
·Transmission line communication systems

Advantages
·Compact compared with large inductive voltage transformers
·Suitable for EHV transmission applications
·High insulation strength
·Excellent outdoor environmental performance
·Good transient response
·Supports protection and metering functions
·Long operating life
·Low maintenance requirements

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

Connected equipment:
·Protection relays
·Revenue meters
·Synchronizing devices
·SCADA systems
·Digital fault recorders
·Substation automation systems

Common Standards
A 245kV capacitor voltage transformer is designed and tested according to:
·IEC 61869-5 – Additional Requirements for Capacitor Voltage Transformers
·IEC 61869-1 – General Requirements for Instrument Transformers
·IEEE C57.13 – Instrument Transformer Standards

Typical Applications in a 245kV Substation
·Busbar voltage measurement
·Transmission line voltage monitoring
·Protection relay voltage input
·Grid synchronization
·SCADA voltage acquisition
·Energy metering
·Power system automation
·Fault and disturbance recording
·Power line carrier communication

Key Features
·Designed for 245kV EHV transmission networks
·High dielectric strength and mechanical reliability
·Multiple secondary windings available
·Suitable for harsh outdoor environments
·Supports both protection and measurement applications
·Compatible with modern digital substations

A 245kV Capacitor Voltage Transformer (CVT) is a key component in modern extra-high-voltage transmission systems. It provides accurate voltage measurement, reliable protection signals, and electrical isolation for 220kV-class substations, helping ensure stable operation, effective grid monitoring, and dependable power system protection.