High Voltage Equipment
The High Voltage Laboratory testing facilities are based around two major pieces of equipment, namely an impulse generator and a HVac testing transformer. These allow controlled testing of equipment and material insulation, such as under dry and wet conditions. While testing can be undertaken according to standards requirements, staff specialize in developing testing requirements for specific customer requirements and more explorative research.
The University of Canterbury impulse generator is an inverted Marx multi-stage unit. It has 14, variable 0 - 100 kV stages with a maximum peak voltage of 1.4 MV. It can be used to generate standard lightning impulses of the form 1.2 µs rise time with a 50 µs decay to 50% of the peak voltage. By placing a resistor across the object under test, the generator can also be used to provide non-standard impulses. Two sma ller impulse units, with outputs of 20 kV and 2 kV respectively, provide a wider range of pulse lengths. Actual values depend on loading.
HVac Testing Transformer
The HVac transformer has a dual rated output voltage, either 150 kV or 300 kV at the secondary. The power rating of the transformer is 100 kVA on a continuous basis and 200 kVA on a 5 min on, 15 min off duty cycle. The basic unit is a fixed turn power frequency (50 Hz) transformer. The design of this unit is similar to power transformers except that the insulation is graded and the windings are designed to withstand forces associated with overcurrents as a result of flashovers under test. A voltage regulator supplies the HVac transformer, so that voltages from 0 up to rated value can be applied to a test object. A number of smaller distribution and testing transformers allow for testing over a variety of lower power and lower voltage levels.
By the use of a diode rectifier circuit rated to 200 kV, the output of the HVac testing transformer can be used to generate either +ve or -ve HVdc. This is necessary for testing HVdc equipment.
Variable Frequency High Voltage
A 100 kVA, 3 phase motor speed controller has been modified to produce a spectrum of harmonics for a single phase output. This can be put into transformers to give high voltage harmonics up to about 1 kHz. Also, the motor controller can be used to drive a ripple frequency generator to give a single frequency output up to about 1 kHz.
A Tesla coil is a radio frequency, quarter-wavelength antenna. The lab = s Tesla coil operates at 150 kV. It is generally used as a demonstration of high frequency, high voltage arcing.