Impulse Current Test Laboratory

Given the significance of ZnO arresters, which are being utilized by more and more utilities, the Impulse Current Laboratory was founded in 1996 as a comprehensive testing facility for testing zinc oxide elements and ZnO arrester pro-rated sections up to 12 kV rating in accordance with IS 15086-4 & IEC 60099-4. Its unique computer-controlled impulse current generator, which combines all possible characteristics into a single consolidated design and has a rating of 100kV and 300kJ (Upgraded in 2017), is what makes it superior. At the time of commissioning, it may have been the only one of its kind in this region of the world. 

The following impulse current wave shapes specified by national and international standards can be produced by the generator.

An advanced Dr. Strauss make impulse recording system (TRAS 100-12, 4 channel, 100 MS/s, 12 bit) with customised software for recording and analysing impulse current, voltage and impulse current superimposed with AC voltage at dynamically varying time base (a unique feature required for recording voltages and currents in Operating Duty tests on arrester nonlinear elements) is a part of the Impulse Current Laboratory. 

Generator Capability  

The generator is capable of generating following impulse currents of wave shapes stipulated in the National / International standards.

This Laboratory can undertake the following NABL accredited type tests as per National & International Standards:

• Residual Voltage Tests on ZnO element
  • Steep Current Impulse residual voltage
  • Lightning Current Impulse residual voltage
  • Switching Impulse residual voltage
• Test to verify long term thermal stability under continuous operating voltage/Accelerated ageing test
• Repetitive charge transfer rate
• Heat Dissipation behaviour of test sample
• Operating duty test on prorated sections/Switching surge energy rating
• Power frequency vs time test / TOV test
• High current short duration test
• Low current long duration test
• Reference voltage measurement
• Power loss measurement
• Leakage current measurement
• Artificial pollution test
• Weather ageing test on polymer arresters (1000 hours)
• Accelerated ageing test on polymer arresters with exposure to salt fog (1000 hours)

Test set up for NABL Accelerated Ageing test for 1000 hours on ZnO element :  

The accelerated ageing test set up is shown below. It consists of a 8kV, 1Amp harmonics free uninterrupted High voltage Transformer with regulator, three independent ovens with temperature sensors to maintain the temperature at 115 ± 4ºC to age three samples at a time as per standard, and a computerized Data Acquisition and Analysing system to compute the power loss using measured voltage and current signals. Using this test set up, the 1000 Hour ageing test can be carried out on ZnO elements up to 6kV rated voltage, which is accredited by NABL.