HV AC Series Resonant Test System

AC Series Resonant Test Set is a system designed to test capacitive loads using reactive voltage and reactive power primarily. It draws very little power from the mains supply just sufficient to feed the losses of the test circuit. KVTEK can also supply a trailer mounted mobile test system for on-site testing.

The Series Resonant Test Systems are designed for high voltage testing of capacitive test object such as Power Cable, Generators, Bushings, Capacitors, Transformers and SF6 Gas Insulated equipments.

These systems are available in two designs; Modular Design & Tank Type Design. Modular Series Resonant Test is designated as is designated as (RSX-YM) and Tank Type Series Resonant Test Set is designated as (RSX-YT) where X stands for output voltage rating in KV and Y stands for power rating in KVA.

Modular Series Resonant Test is typically used for voltages higher than 200kV and Tank Type design is used for voltages up to 350kV. Tank type design it is possible to have multiple taps which are not possible in Modular design. Modular test set can be stacked one upon the other to generate as high as 1600kV.

Principle of Operation:

Practical Series Resonant Test System consists of a voltage regulator, exciter transformer, HV Variable reactor and the capacitive test object. The voltage regulator is connected to the mains through a main circuit breaker. This component supplies a variable voltage to the exciter transformer which permits the output voltage to be adjusted to the proper value for the test.

The exciter Transformer supplies the necessary power to the high voltage circuit consisting of the HV variable Reactor and the test object. The exciter Transformer also provides galvanic isolation between the mains connected primary and the high voltage circuit in the secondary. These Transformers are designed with shielding to further isolation line conducted electrical noise from the output circuit.

The HV Variable Reactor is the heart of the resonant circuit. (This device is designed with means to adjust its inductance to precisely compensate for the capacitance in the high voltage circuit thereby tuning the system to resonance). This variation in inductance is accomplished by building an air gap into the core of the reactor. The length of the air gap is adjusted by motor driven mechanism controlled from the control panel through Laptop of PC.

The capacitance load represents the combined effects of the test object, voltage divider, filter capacitors (if used) and stray capacitance due to the test set up. A capacitive load is required for proper operation of the system in the series resonant mode.

Features & Benefits

  • Very low (real) input power is required for large output (reactive) power.
  • The output voltage has suppressed harmonic level due to its natural filtration ability.
  • In the event of a fault in test object, the system de-tunes itself and the power follow from the mains is eliminated, thus limiting damage to the fault.
  • The system is operated in a controlled resonant condition so accidental resonant cannot occur.
  • Lower Test equipment cost for system rated 250kVA and above.
  • Reduced costs because of the substantially reduced input KVA required.
  • Lower installation cost for the power service because the load is at unity power factor.
  • Operating costs are reduced because input KVA requirement is low and mains unbalance is minimized.


Main components of the systems:

  • Double Shielded Isolation Transformer
  • Voltage Regulator Unit
  • Low Voltage Filter
  • Exciter Transformer
  • High Voltage Reactor
  • HV Filter/ Voltage Divider
  • Control Unit
Modular Type Resonance Test Set

Tank Type Resonant Test Set