Classification of High Voltage Laboratories:
Classification of High Voltage Laboratories depending on the purpose for which they are intended and the resources (finances) available, can be classified into four types.
Medium size laboratories
Large general purpose laboratories
Some salient features of these various types of laboratories are discussed below.
A small laboratory is one that contains d.c. or power frequency test equipment of less than 10 kW/10 kVA rating and impulse equipment of energy rating of about 10 KJ or less. Voltage ratings can be about 300 kV for a.c., single unit or 500 to 600 kV a.c. for cascade units, ±200 to 400 kV d.c. and less than 400 kV impulse voltage. Normally the equipment is meant for housing in a room or hall of size 15 m x 10 m x 8 m. Sometimes the equipment ratings are limited such that they can be accommodated in a room of height 5 m to 6 m only. Such laboratories are meant for engineering colleges and universities who decide to build such a facility with small resources for doing high voltage tests or research or for imparting training. In such a case, it is preferable that the engineering college or university associate with a local industry or R and D organization. It is important to device and define the responsibilities of the parties concerned as to how the test facilities and time can be shared. Another idea is to have the university to decide to own the laboratory fully but throw open the facilities of regular technical training and high voltage testing for the clients. Here it may be mentioned that many Classification of High Voltage Laboratories problems can be solved by tests at moderate voltage levels. Such laboratories can be built with an investment of 2 to 10 million rupees (at 2000 prices).
2.Medium Size Laboratory – An Industrial Laboratory:
In case of medium size laboratories, their main function will be for doing routine tests. The demand on future tests and test resources will be known to the same extent as that of the future production targets. Careful planning of such laboratories should include
- ground transport,
- handling equipment like cranes etc.,
- rationalization of test procedures by making instruments easily accessible, and
- providing room for the possibility of increasing the maximum voltage rating etc.
Such a laboratory may initially contain a power frequency testing facility in the range of 200 to 600 kV depending on the ratings and the size of the equipment being manufactured and proposed to be tested, such as cables, transformers etc., but its kVA rating will be much higher (100 to 1000 kVA). The impulse voltage generator required would have a rating of 20 to 100 kJ or more. Other test equipments like the impulse current generator for testing surge arresters and d.c. test facilities for testing cables and capacitors can also be made available. In industrial laboratories not much emphasis is generally given for undertaking research work and little flexibility may be available for incorporating new equipments.
3.Large Size Laboratories:
This type of laboratories are meant to carryout testing and undertake research work as envisaged and 11.3 and will contain almost all Classification of High Voltage Laboratories and high current test equipments and facilities. The basic facilities available will be
- One or more h.v. test halls,
- Corona and pollution test chambers,
- Outdoor test area for tests on large sized equipment, transmission lines and towers etc.,
- Controlled atmospheric test rooms/chambers,
- Computer facilities, conference halls, library etc. with good office facilities, and
- Provision for overnight tests and stay.
The size and ratings of the test equipment will be quite large. The building and equipment include the workshop, material handling equipment like cranes, ladders, air cushion platforms etc. and large control and electric supply facilities (up to few kVA or MVA). The personnel connected with such a laboratory will include a director or manager, few group leaders, and section heads separately for research, testing, measurements, electronics and computer facilities etc. In addition, there will be supporting staff comprising test engineers, technicians, librarians, office staff and skilled and semi-skilled workmen
UHV laboratories are intended for carrying out tests which help in the basic design of experimental transmission lines of voltage ratings of 765 kV and above and for full scale outdoor testing of conductors and insulation structures. In addition there should be an indoor laboratory for doing basic research. A UHV laboratory should therefore comprise:
- an outdoor experimental line for conducting corona and vibration studies,
- an outdoor corona test cage,
- an erection bay,
- a pollution test chamber, and
- indoor laboratories for basic research.