Download Modeling of transformer internal faults

Problem: 1
Modeling of transformer internal faults
Power transformer is common equipment in power system, yet it is very important. A fault in
power transformer can lead to huge damage in terms of equipment loss and power system
disruption. It is required that any internal fault in transformer in detected quickly and the
transformer is disconnected immediately to prevent extensive damage to the transformer and the
neighbouring system.
Modeling the internal faults in power transformer for electromagnetic transient study will help in
proper analysis of the fault situation and then lead to development of better ways to detect such
faults through terminal current measurements.
There is a well established model for transformer for doing electromagnetic transient studies. The
present scope of the problem is to extend the model to also include the capability to model internal
faults of the transformer, and still maintain the model compatible with the existing electromagnetic
transient calculation program.
An already available method is selected to study the modeling of transformer internal faults. It
relies on calculation of ‘leakage factors’ of the transformer windings. The first aim of the study
group workshop is to understand the modeling that leads to calculation of ‘leakage factors’. The
next aim is to model it in some simplified manner and see if the modeling errors are within
acceptable limits to select the simpler method.
The basic method for calculation of ‘leakage factors’ is to calculate first the leakage inductance
between to concentric coils. This calculation is based on application of Amperes law for calculation
of magnetic field intensity. The following two figures show the calculation of leakage inductance
for intact coils and a coil with a single earth fault.
Problem: 2: Planning of Loop type Power Distribution System
1. Background
An electric distribution system is an important part of a power system. It connects
all loads in an area to transmission lines. It takes power from few sites and delivers it to
large numbers of consumers scattered through out whole service area in to use form. There
are three major parts of distribution system:
• Sub-transmission lines
• Distribution substations
• Primary feeders
Sub-transmission lines
Sub transmission lines receive power from bulk power sources i.e. generating
stations or receiving end substation. Their capacity ranges from 30 MVA to 250 MVA and
operating voltage ranges from 33 kV to 132 kV.
Distribution Substations
Distribution substations are the meeting place between transmission grid and the
distribution feeder system. Substation feed its own load area, which is a part of whole
distribution system. Each substation consists of transformer and its supporting switchgear
e.g. circuit breakers, isolators, control and buswork.
Primary Feeders
Feeders are basic building blocks of distribution system. Feeders are delivery
circuits, which route power from distribution substation to the vicinity of consumers. Each
feeder has its own service area, which is a part of substation service area. The diagram of
primary feeders is shown in Figure-1.1.
132 kV
Distribution
substation
transformer
Isc 10,000A
Feeder breaker
Open
switch
Lateral 1
Distribution
transformer
R
3 ph- Recloser
Figure 1.1 Schematic of Primary Feeder
Types of Distribution System
•
There are three types of distribution system, which are as follows:
Radial configuration
•
Loop configuration
•
Network configuration
Loop
Radial
Network
Figure 1.1 Types of distribution systems
1.1 PROBLEM STATEMENT
Electric power is distributed to end consumers through a network of electric conductors and
cables. This network is called power distribution network.
The electrical power distribution layout can be classified as urban and rural distribution
system. According to type of situation that confronts the planner in laying out the distribution
system the urban distribution, system presents many challenges to the planner.
The urban distribution system has loop-based layout as it requires much higher reliability to
be inbuilt in the design itself.
The aim of this project is to plan a loop type distribution feeder for a given urban area in such
a way to attain lowest capital cost, lowest electrical losses, and lowest loss of revenue due to
breakdown (highest reliability). Technical constraints taken are voltage drop, economic capacities
of conductors, maximum line loading. Physical constraints are obstacles, high cost passages. For
easy modeling it is preferred that the layout is constrained by a grid. In practice, the grid can be
taken from the Geographical Information System (GIS).
The input for this model is substation location, load location & magnitude, unit length of GIS
grid, energy costs, costs of losses, initial cost of conductors, resistance and reactance/km of
conductor set. The outputs are following:
 Optimal route of feeder reaching every load location.

Optimal power flow through each segment of feeder.

Optimal conductor selection in each segment of feeder.
Problem: 3 : Analysis
of the Analogue Signal Generated by
Atom Emission Spectrometer
An Atom-Emission spectrometer is used to identify the various elements present in a metallic
sample. The metallic sample is placed on a support so that it is exposed to a heat source generated
by igniting an electrode as shown in the figure.
Lens
Sample
Entrance Slit
Concave
Grating
Electrode
Photomultiplier
Exit Slit
Focussing Mirror
Figure 1 Schematic of the System
Due to this heat, there will be micro-melting of the sample and an optical signal is generated which
is a combination of signals of various frequencies, ranging from 160nm to 410nm depending on
elements present in the sample. This optical signal is projected on a holographic diffraction grating
through an entrance slit. This diffraction element splits the composite light source into spectral
components. Then a transducer is used to convert the optical information to an electrical signal,
which is captured in the analogue form, as shown in the figure 2, whose resolution depends on the
pixel configuration of the CCD used in the system.
Figure 2
The system under consideration has 3648 linearly placed sensors with a pitch of 8 micrometers.
The various peaks observed in a signal are then compared with the known responses of the standard samples
having known composition of elements and the given sample is analyzed. The interpretation depends on
how accurately these peaks are identified. It is possible that the actual peak or height of the line information
is not the same as the maximum peak observed by the CCD as shown in the following figure 4.
Figure 3
Figure 4
The actual peak is missed out due to the peak falling on the gap between two pixels. There may be
other reasons due to which the peak line information is not obtained correctly. In the proposed
project this hidden information is to be obtained, using Mathematical Techniques.