- Why High Voltage Laboratory?
- Why Virtual High Voltage Laboratory?
- Learning Objective
- Features
Today, the quality of life has reached such a state, that our living is practically unthinkable without electricity. Electricity is, perhaps, the third most important commodity, coming next only to air and water, for the existence of life. All of us are aware that load centers are usually far away from the generating stations, which are located in remote areas depending on the type of generation. To avoid unnecessary losses over long distances, power is invariably transmitted at higher voltages.
In fact, the country is entering a stage where transmission has reached Ultra High-Voltage (UHV) levels. All this necessitates the development of appropriate insulation materials and their use in High Voltage power apparatus. There assessment calls for a High-Voltage laboratory.
A high-Voltage laboratory needs to be established to carry out fundamental studies on insulating materials, to carry out the performance evaluation of proto types and also to assess the condition of High-Voltage power apparatus before their erection and installation. So what comprises a High-Voltage Laboratory? 
As most of the power generation, transmission and utilization employ alternating voltages, any laboratory should have a high voltage alternating source with associated measuring equipment. Moreover, any power apparatus faces transient over voltages, which could be external (atmospheric or lightning) or internal (System generated or switching), and therefore needs to be assessed for them. This aspect is studied by having Impulse Voltage Generators (IVG) and Impulse Current Generators (ICG). Fig. 1 shows the typical waveforms of impulse voltages produced in the laboratory.
As already mentioned the high-voltage tests are usually carried out to assess the quality of insulation of the power apparatus; hence it becomes necessary to have a facility for measuring the capacitance and the loss tangent of the power apparatus insulation. Further, a facility for assessing cables high-voltage DC test source is preferred as they tend to draw large charging current on AC. Of late Partial discharge (PD), testing is gaining importance in the form of a Non Destructive Test. As the name suggests PD connotes a partial breakdown within the bulk of the insulation without a complete breakdown across the two electrodes. In fact, the corona phenomenon, which is very well known, is also a form of PD. Hence it is necessary to have a facility for PD testing also.
Last but not the least is to have High-Voltage meggars of various voltage ratings. Thus, we note that any high-voltage laboratory must at the least have the following:
• high voltage AC test source with the associated measurement setup
• Impulse voltage generator along with requisite measurement setup
• High voltage capacitance and loss tangent measurement bridge; usually a Schering bridge
• High voltage DC test source
• Partial discharge measurement system
• Meggar (of atleast 1 kV)
Now, it becomes necessary for us to know the special requirements of the laboratory building. Needless to say, a high-voltage laboratory should have a very good earth, which serves the two purposes of safety and reference potential, just as in any other electrical system. Unlike other laboratories, space requirements are very large for a high-voltage laboratory. Considering any point at high-voltage, an all round clearance decided by the electric field is to be maintained. Further, in order to have minimum interference from external electromagnetic sources on the tests being conducted inside and also to make the tests not disturb the electromagnetic environment elsewhere, the lab is specially shielded by having iron wire mesh embedded all through the walls. This mesh is connected preferably by brazing to the roof and the ground mat, thus acting as a near continuous magnetic conducting earthed enclosure. The principle of shielding can be very well understood by applying Guass’ theorem to such a continuous surface. In order to have adequate clearance and possibility of any power apparatus to be brought in and taken out, the roof of the laboratory is built in trusses and is made self-supporting on the walls without any pillars anywhere else. Facilities for material handling are a must. Any openings provided are for entry/exit of power or signal cables and power apparatus. Typically the test voltages are of the order of 2.0 pu for ac power frequency, 6.0 pu for lightning impulse and at the most 3.0 pu for switching impulses. One important thing to be borne in mind is that there is a likelihood of failure of apparatus in which case test source faces a dead short circuit. So, provision must be made to take care of such an eventuality by way of current limiting resistors. Further, the test voltage depends on the rating of the apparatus and so there must be a provision to vary the test voltage from 0 to 100 %. Test results depend very much on the atmospheric conditions and hence a high-voltage laboratory is invariably provided with a hygrometer and a barometer.
Last but not the least is the provision of safety interlocks to disable any accidental charging of the test sources, when the gates between the test area and the control area are open. The salient features of HV laboratory at IIT Kharagpur are:
• Laboratory of 75ft* 50ft*45ft
• H.V. a.c power frequency test source of 200 kV, 10 kVA along with a peak voltmeter
• Impulse voltage generator, 600 kV,18kJ, along with a divider and a 100 MHz, 200 MS DSO
• H.V.D.C source 80 kV,80 mA
• PD meter along with 1000 pf, 200 kV coupling capacitors
• H.V Schering Bridge along with 100 pf, 200 kV standard nitrogen filled capacitor
• Meggar (500 kV, 1 kV, 5 kV)
• Rectangular Pulse Current Generator 200 A, 15 ms
It must be mentioned, that there are several industrial applications of High-Voltage Engineering:
• Photocopying (cannot dream of any modern office without it)
• Electrostatic Precipitator
• Electrostatic Coating
• Electrostatic separation of minerals
• X-rays
As most of the power generation, transmission and utilization employ alternating voltages, any laboratory should have a high voltage alternating source with associated measuring equipment. Moreover, any power apparatus faces transient over voltages, which could be external (atmospheric or lightning) or internal (System generated or switching), and therefore needs to be assessed for them. This aspect is studied by having Impulse Voltage Generators (IVG) and Impulse Current Generators (ICG). Fig. 1 shows the typical waveforms of impulse voltages produced in the laboratory. As already mentioned the high-voltage tests are usually carried out to assess the quality of insulation of the power apparatus; hence it becomes necessary to have a facility for measuring the capacitance and the loss tangent of the power apparatus insulation. Further, a facility for assessing cables high-voltage DC test source is preferred as they tend to draw large charging current on AC. Of late Partial discharge (PD), testing is gaining importance in the form of a Non Destructive Test. As the name suggests PD connotes a partial breakdown within the bulk of the insulation without a complete breakdown across the two electrodes. In fact, the corona phenomenon, which is very well known, is also a form of PD. Hence it is necessary to have a facility for PD testing also.
Last but not the least is to have High-Voltage meggars of various voltage ratings. Thus, we note that any high-voltage laboratory must at the least have the following:
• high voltage AC test source with the associated measurement setup
• Impulse voltage generator along with requisite measurement setup
• High voltage capacitance and loss tangent measurement bridge; usually a Schering bridge
• High voltage DC test source
• Partial discharge measurement system
• Meggar (of atleast 1 kV)
Now, it becomes necessary for us to know the special requirements of the laboratory building. Needless to say, a high-voltage laboratory should have a very good earth, which serves the two purposes of safety and reference potential, just as in any other electrical system. Unlike other laboratories, space requirements are very large for a high-voltage laboratory. Considering any point at high-voltage, an all round clearance decided by the electric field is to be maintained. Further, in order to have minimum interference from external electromagnetic sources on the tests being conducted inside and also to make the tests not disturb the electromagnetic environment elsewhere, the lab is specially shielded by having iron wire mesh embedded all through the walls. This mesh is connected preferably by brazing to the roof and the ground mat, thus acting as a near continuous magnetic conducting earthed enclosure. The principle of shielding can be very well understood by applying Guass’ theorem to such a continuous surface. In order to have adequate clearance and possibility of any power apparatus to be brought in and taken out, the roof of the laboratory is built in trusses and is made self-supporting on the walls without any pillars anywhere else. Facilities for material handling are a must. Any openings provided are for entry/exit of power or signal cables and power apparatus. Typically the test voltages are of the order of 2.0 pu for ac power frequency, 6.0 pu for lightning impulse and at the most 3.0 pu for switching impulses. One important thing to be borne in mind is that there is a likelihood of failure of apparatus in which case test source faces a dead short circuit. So, provision must be made to take care of such an eventuality by way of current limiting resistors. Further, the test voltage depends on the rating of the apparatus and so there must be a provision to vary the test voltage from 0 to 100 %. Test results depend very much on the atmospheric conditions and hence a high-voltage laboratory is invariably provided with a hygrometer and a barometer.
Last but not the least is the provision of safety interlocks to disable any accidental charging of the test sources, when the gates between the test area and the control area are open. The salient features of HV laboratory at IIT Kharagpur are:
• Laboratory of 75ft* 50ft*45ft
• H.V. a.c power frequency test source of 200 kV, 10 kVA along with a peak voltmeter
• Impulse voltage generator, 600 kV,18kJ, along with a divider and a 100 MHz, 200 MS DSO
• H.V.D.C source 80 kV,80 mA
• PD meter along with 1000 pf, 200 kV coupling capacitors
• H.V Schering Bridge along with 100 pf, 200 kV standard nitrogen filled capacitor
• Meggar (500 kV, 1 kV, 5 kV)
• Rectangular Pulse Current Generator 200 A, 15 ms
It must be mentioned, that there are several industrial applications of High-Voltage Engineering:
• Photocopying (cannot dream of any modern office without it)
• Electrostatic Precipitator
• Electrostatic Coating
• Electrostatic separation of minerals
• X-rays
Digital computers are universal machines that can simulate any machine or any process that can be precisely described. Engineers use advanced computer systems to build and study working simulations. Laboratory experiences are essential to learning in all areas of engineering. Most of the benefits of a traditional laboratory can be captured in a virtual laboratory. Moreover, the virtual laboratory has some educational advantages not available in the traditional laboratory. Virtual High Voltage Laboratory (VHVL) is an implementation of this concept in the field of high voltage engineering. VHVL deals with standard voltage & current generation (DC and AC both), insulation tests of various power apparatus viz. impulse voltage testing (power cables, power and instrument transformers), impulse current testing (surge arresters, power transformers) and rectangular impulse current testing (surge arresters).
Here at Virtual High Voltage Lab the user will use this property of digital computers to "learn by discovery" . Virtual High Voltage Laboratory is a "virtual laboratory" where the user will discover scientific principles which can be discovered by performing simulated laboratory experiments. These simulations can supplement actual experiments in student laboratories or serve as traditional homework. Sometimes the experiments performed by the user will be tightly controlled and lead the user by hand as user interrogates simulations,complete tables and graph results.
Most exercises in Virtual High Voltage Laboratory are divided into two sections: "Experiments" and "Models". "Experiments" display what appears to be actual laboratory equipment that can be manipulated with the keyboard and mouse to perform a simulated experiment. "Models" permit use of standard problem-solving tools to build users own simulations. It can act as a good tool for teaching and enable a student to understand the influence of circuit parameters on the output waveshape. Also it can serve as a guide for the testing engineer to arrive at the values of the generator parameters for impulse testing of various power apparatuses and simulate tests.
While accessing Virtual High Voltage Laboratory user will have the feel of real laboratory because of the animation of the experiments performed, user can take help of manual, user can ask his problems to VHVL developers via e-mail and in the end of every experiment user will face a brain teaser quiz.
Objectives: A web-based virtual high voltage laboratory for elementary engineering science courses is established to examine the effectiveness and its influence on learning habits.
Here at Virtual High Voltage Lab the user will use this property of digital computers to "learn by discovery" . Virtual High Voltage Laboratory is a "virtual laboratory" where the user will discover scientific principles which can be discovered by performing simulated laboratory experiments. These simulations can supplement actual experiments in student laboratories or serve as traditional homework. Sometimes the experiments performed by the user will be tightly controlled and lead the user by hand as user interrogates simulations,complete tables and graph results.
Most exercises in Virtual High Voltage Laboratory are divided into two sections: "Experiments" and "Models". "Experiments" display what appears to be actual laboratory equipment that can be manipulated with the keyboard and mouse to perform a simulated experiment. "Models" permit use of standard problem-solving tools to build users own simulations. It can act as a good tool for teaching and enable a student to understand the influence of circuit parameters on the output waveshape. Also it can serve as a guide for the testing engineer to arrive at the values of the generator parameters for impulse testing of various power apparatuses and simulate tests.
While accessing Virtual High Voltage Laboratory user will have the feel of real laboratory because of the animation of the experiments performed, user can take help of manual, user can ask his problems to VHVL developers via e-mail and in the end of every experiment user will face a brain teaser quiz.
Objectives: A web-based virtual high voltage laboratory for elementary engineering science courses is established to examine the effectiveness and its influence on learning habits.
•To build the confidence of the user to work in an actual high voltage laboratory.
•To realize importance and necessity of a High Voltage Laboratory.
•To understand various types of high voltages (viz. ac, dc and impulse) and their importance.
•To understand and assimilate the concepts of high voltage engineering.
•To provide an effective platform to study the effect of variation of circuit parameters on any high voltage circuit.
•To provide an easy access to experimental applications anytime, anyplace, independent of platform making learning a pleasure.
•To realize importance and necessity of a High Voltage Laboratory.
•To understand various types of high voltages (viz. ac, dc and impulse) and their importance.
•To understand and assimilate the concepts of high voltage engineering.
•To provide an effective platform to study the effect of variation of circuit parameters on any high voltage circuit.
•To provide an easy access to experimental applications anytime, anyplace, independent of platform making learning a pleasure.
•Not all institutions can afford a very costly physical High voltage laboratory.VHVL offers a unique experience which can be experienced by any institution from a common server.
•Unlike testing on physical High voltage circuit, practically any type of circuit parameter rating can be simulated using a VHVL.
•It serves as a compact analyzing platform for R&D institutions.
•Unlike testing on physical High voltage circuit, practically any type of circuit parameter rating can be simulated using a VHVL.
•It serves as a compact analyzing platform for R&D institutions.