Impulse Voltage Test System

Impulse voltage test systems are used to generate impulse voltages simulating lightning strokes and switching surges. Main applications include impulse voltage tests on HV apparatus like Power Transformers, Instrument Transformers, Switchgears, Circuit Breakers, HV Cables etc. according to IEC, ANSI/IEEE as well as other national standards.

Impulse Voltage Test Systems are modular in construction, flexible and cover testing application according to IEC, ANSI/IEEE and other national standards. The basic system can be upgraded in various ways to allow optimization of Impulse Test System for tests on different high voltage equipments. The system operation is user friendly and incorporates all the necessary features of Impulse Voltage Test. These systems meet all the requirements of industry, research and development centres, educational institutes and third party test labs

W Series Impulse Generators models are designated as (WX-YIG) where X stands for voltage rating X kV and Y stands for energy rating Y kJ. There are 100kV per stage Impulse Generators with energy options of 5kJ or 10kJ per stage and are typically available upto 1600kV, 160kJ. In special case can be up-graded to higher ratings as well.

V Series Impulse Generators models are designated as (VX-YIG) where X stands for voltage rating X kV and Y stands for energy rating Y kJ. There are 200kV per stage Impulse Generators with energy options of 10kJ or 20kJ or 30kJ per stage and are typically available upto 6000kV, 900kJ.

The Impulse Voltage Generators consist of a number of capacitors, connected to sphere gaps and front & tail resistors. Capacitors are charged in parallel up to maximum of 100kV per stage in W series and up to to 200kV per stage in V series, and discharged in series. The output voltage is delivered via some wave shaping resistor. After the set voltage is reached, a trigger pulse initiates firing of the first spark gap. The result over trigger successive stages, thus connecting them in series and multiplying the charging voltage.

This is the generation  of required impulse. An impulse voltage divider reduced such impulse voltage to a safe level that the measuring instrument requires. Chopping sphere gap connected in parallel with the Impulse Generator may also be triggered through microprocessor control to obtain chopped lightning impulse of desired duration. All the coupling sphere gaps are mounted in a FRP enclosure, and every stage of sphere gaps is equipped with spark observation window. The capacitor is less than 0.2µH. The waveform resistors are epoxy moulded and have non-inductive winding. Spring loaded connections make them easier to change.

Applications :

  • Power & Distribution Transformers
  • Cables
  • Surge Arresters
  • Insulators
  • Bushings
  • GIS
  • Instrument Transformers
  • Switchgear

 

Features :

  • Low internal inductance ensure high efficiency.
  • Easy and quick reconfiguration to meet different testing requirements. Front and Tail resistors being of same length can be interchanged, thus allowing more flexibility and wider range of load testing.
  • User friendly operation through computer controlled hardware.
  • Equipped with wave shaping resistors for performing full lightning chopped, lightning and switching impulse tests on a wide range of loads. Special resistors can be supplied for any impulse shape or load testing.
  • Automatic steel & insulating tape grounding device and security grounded system.
  • Alarm annunciation to display all fault conditions.
  • Filtered clear, hot air is constantly supplied through the closed sphere gaps while the system is operational, to reduce misfires.
  • Reliable, accurate and fail-safe triggering circuitry.
  • Load range can be extended using Glaninger Circuit, overshoot compensation, termination resistors and special wave shaping resistors.
  • The electronic measurement and control devices are designed are manufactured to meet electro-magnetic compatibility requirements of electronic devices in high voltage test bays which ensure trouble-free operation.

 

Main components of the System :

  • Impulse Generator
  • Charging Rectifier
  • Impulse Voltage Divider
  • Multiple Chopping Gap
  • Shunts
  • Glaninger Circuit
  • Impulse Control System
  • Impulse Analyzing System
  • Overshoot Compensation Device

 

Overshoot Compensation Device : An overshoot compensation device allows to test higher capacitive loads according to the standard Impulse shapes.

Glaninger Circuit : For testing low voltage windings of transformers, an additional circuit can be added on the output of Impulse Generator. The Glaninger inductance (LG) is connected in parallel to the generator serial resistor (RS). The rapid rise at the impulse front (high frequency component) is not influenced by the additional Glaninger inductance (LG).
Therefore, the front of the impulse is mainly defined by the serial resistor (RS). Conversely, the slow decay (Low Frequency Components) at the tail of the impulse is influenced by the parallel connection of LG & RS. The result is less damping in the overall test circuit and an increased time to half value. This external circuit allow to test low inductive loads which are generally prevalent while testing LV windings of large MVA transformers. This external circuit is designed to be used in 1Ss2p configuration.


V Series Impulse Voltage Test System

W Series Impulse Voltage Test System