CPRI has established the Impulse Current Laboratory as a comprehensive facility for testing of Zinc Oxide ZnO arrester elements and pro-rated sections of rated voltage from 3kV to 12 kV as per IEC 60099-4 Edition-3, 2014, IEC 60099-8, IS 3070 Part III and IEEE C62.11, 2012 Edition.

The laboratory with dimensions of 13 m x 17 m x 7 m is equipped with a unique Computer controlled Impulse Current Generator of rated 100 kV, 300 kJ incorporating all conceivable features in a single consolidated design and is perhaps the only one of its kind in this part of the world.

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.

With these wave shapes, the following type tests on SH, SM, SL and class-1 to class-5 ZnO arrester elements of 3kV to 12 kV voltage rating used in station, distribution class Heavy, Medium and Light duty arresters can be carried out as per National / International Standards (IEC 60099-4, IEC 60099-8, IS 3070 Part III and IEEE C62.11, IEC 60099-8 latest editions).

NABL accredited Type tests that can be carried out in the Impulse Current Laboratory  

List of NABL accredited tests on ZnO Blocks / prorated sections as per IEC 60099-8  

List of NABL accredited tests on complete arrester from 9kV upto 400kV rating as per IEC60099-4, IS 3070 Part III and IEEE C62.11.  

Test set up for NABL Accelerated Ageing test for 100 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 upto 6kV rated voltage which is Accredited by NABL.

Thermo Mechanical Test Chamber (Vertical)  

The laboratory is equipped with thermo mechanical chamber (vertical) for carrying out bending moment test on arrester units. The dimensions of the chamber are 2.2 m x 300 mm and temperature control range is from -40ºC to +60ºC with accuracy of ± 1 ºC after stratification. The rate of heating / cooling is 1ºC per minute. The chamber temperature is controlled by microprocessor based auto time programmable controller with RS 232 interface and software for configuring and monitoring. The chamber has hydraulic system provided externally and load cell with 20kN capacity. It has got a special mounting and loading arrangement with rotating table so as to enable load application in all four directions to carryout bending moment test on surge arrester units of voltage rating varying from 9kV to 156kV (maximum unit length of 2000 mm approximately). The arrangement is shown below: