High Voltage Laboratory Equipments:
A High Voltage Laboratory Equipments is expected to carry out withstand and/or flashover tests at high voltages on the following transmission system equipment:
- Lightning arresters
- Isolators and circuit breakers
- Different types of insulators
- Line hardware and accessories
- Other equipment like reactors, etc.
Different tests conducted on the above equipment are:
- Power frequency withstand tests—wet and dry
- Impulse tests
- c. withstand tests
- Switching surge tests
- Tests underpolluted atmospheric conditions
- Partial discharge and RIV measurements
- High current tests.
In addition to the above facilities, the laboratories should also have facilities for conducting research on dielectric properties of insulation and insulating materials.
An Ultra High Voltage Laboratory Equipments should serve the long term requirements of UHV transmission system as well the immediate short term needs in the operation and strengthening of lower voltage transmission lines which are presently in use or planned for the near future. In its initial phase it can be used for testing of equipment rated at 400 kV or 525 kV, i.e. insulation strings, transmission towers/lines and hardware, transformers, bushings, disconnectors and metalclad switchgear for a.c./d.c. type testing. In addition to the above, the following test programs and research activities are carried out in an UHV laboratory.
High Voltage Laboratory Equipments, in addition to conducting tests on equipment, are used for research and development work on the equipment. This includes determination of the safety factor for dielectrics and reliability studies under different atmospheric conditions such as rain, fog, industrial pollution, etc., at voltage higher than the test voltage required. Sometimes, it is required to study problems associated with test lines and other equipment under natural atmospheric or pollution conditions, which cannot be done indoors.
Research activities usually include the following:
- breakdown phenomenon in insulating media such as gases, liquids, solids, or composite systems,
- withstand voltage on long gaps, surface flashover studies on equipment with special reference to the equipment and materials used in power systems,
- electrical interference studies due to discharges from equipment operating at high voltages,
- studies on insulation co-ordination on h.v. power systems, and
- high current phenomenon such as electric arcs and plasma physics.
The fields of research undertaken in an UHV laboratory are generally related primarily, to the design, development and testing needs of transmission lines having a.c. system voltages of 765 kV and 1100 kV, and also the needs of equipment testing at this facility. The following principal research areas can be identified:
- effect of corona and field on the performance of transmission lines.
- performance of air insulation under different voltage stresses using very long gaps.
- performance of line insulators under different weather conditions (temperature, humidity, etc.) and varying pollution conditions.
- performance of conductor bundles which are subjected to aolian vibrations.
Usually, high voltage laboratories involve tremendous cost. Hence, planning and layout have to be carefully done so that with the testing equipment chosen, the investment is not high and the maximum utility of the laboratory is made.