EHV Test Laboratory

The EHV test laboratory consists of an indoor laboratory and an outdoor laboratory test bay. Indoor laboratory is a high voltage test hall of dimensions 50mX40mX35m housing a 3MV, 150kJ impulse generator, a rain making equipment and power frequency testing transformers of ratings a) 150kV, 75kVA. b) 100kV, 50mA and c) 600kV, 2000kVA.

The outdoor test bay consists of a 1800kV, 2000kVA cascade transformer comprising of three 600kV, 2000kVA transformer units. All these transformer units and the 600kV, 2000kVA transformer located in the indoor test hall are all similar for the convenience of inter changeability. The AC test voltage up to 800kV from the outdoor bay can be taken into the high voltage test hall by means of a wall bushing. Suitable arrangements are available to mount all types of 550kV class insulator strings on conductors for testing. Material handling facility includes a 24 ton (boom end max), 1 ton (with boom in telescopic mode) mobile crane & 5 ton fork lift.

Major test, measurement and calibration equipment available are:

• Impulse voltage generator of 3 million volts. 150 kJ
• Power frequency Cascade Transformers setup of 1800kV(ie. 3 nos. of 600 kV each)
• Power frequency Transformers one each of 50 kV & 100 kV, 150 kV
• 550 kV Partial discharge free coupling capacitor
• 400kV, 2400pF RIV free coupling capacitor
• High Resolution impulse Analysing system of 120 M samples/ sec per channel. (Totally 4 channels).
• 1GHz Steep front impulse measuring system.
• One meter sphere gap capable of measuring of 1MV (Impulse & Power frequency voltages) as per standards.
• Artificial rain equipment (small & big)
• 50 tonne Universal Testing Machine
• 500 KN Thermo mechanical chamber
• Hot & Cold bath for temperature cycle test upto 220kV
• Reference voltage divider 180 kV, AC/DC, 500 kV LI/SI
• Reference Impulse calibrator.

600kV, 2000kVA Power Frequency Testing Transformer

This setup is used for conducting power frequency voltage tests (Dry & Wet) and RIV & corona tests up to and including 500kV.

1800kV, 2000 KVA, Power Frequency Testing Transformer

This cascade transformer setup is used for carrying out power frequency voltage tests (Dry & Wet) and pollution tests. Facilities are also available for taking supply into the main laboratory for indoor tests.

3 Millionvolt, 150 kJ, Impulse Voltage Generator

This 3MV,150kJ capacity Impulse Voltage Generator has 15 stages and is generally used for dielectric testing. The generator is also suitably configured with series and parallel combinations of capacitors, resistors and an additional inductor to generate the impulse currents necessary to be passed through the surge arrester for measuring the residual voltage.

Thermo Mechanical Test Chamber (Horizontal)

The thermo mechanical chamber for carrying out thermal mechanical load cycle tests is shown below. The temperature control range is from -60ºC to + 60ºC. The tensile strength is ranging from 10 to 500Kn (2 Channels). This chamber is used to carry out the tests on composite long rod insulators and porcelain insulator strings.

With the equipment installed at present, it is possible to undertake following tests on all major electrical equipment like power transformers, current transformers, potential transformers, air break switches, isolators, cables, bushings, insulators power line accessories etc. up to and including 550 kV system.

Types of Tests :

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

• Lightning impulse voltage tests up to 2,400 kV (Peak) level.
• Switching Impulse Voltage Dry & Wet Tests up to 1.5 MV peak level.
• Steep front impulse voltage test on polymer insulators of length up to 500mm and porcelain insulators up to and including 33 kV insulators.
• Corona Inception and Extinction Test and RIV measurements up to & including 500 kV system
• Power frequency voltage Dry & Wet withstand tests up to 1,000 kV (rms) level
• Porosity test on porcelain insulator fragments.
• Mechanical performance/Electro-Mechanical test up to 40 tonnes on porcelain insulators.
• Mechanical performance/mechanical test up to 40 tonnes on polymeric insulators.
• Thermal mechanical load cycle tests.
• Under oil puncture test for porcelain insulators up to and inclusive of 33kV rating.
• Temperature cycle test on insulators up to & including 220kV rating.
• Ferro Resonance tests on CVT at rated voltage up to 220 kV.
• Surge withstand test.
• Voltage distribution tests on insulator strings
• DC withstand & flashover tests under dry condition up to 280 kV.
• Performance check on high voltage dividers as per IEC 60060-2.
• Performance check of digitizers used for impulse measurements as per IEC 1083-1.