High Voltage Direct Current systems have been used for
transporting electrical energy for very long distances, at high
voltages (100- 1000 kv). On utilize thyristorized or transistorized
power converters, one converter is working as rectifier at s
ending
side, and the other is working as inverter at receiving side. Back to
Back Converters are used also where the rectifier and inverter are at
the same station, transmission line has hundreds of meters as long.
In our model we used non controlled three phase rectifier as
sending station and controlled three phase bridge as receiving
station (Graitze).
مبدلات التوتر و التيار
المقومات و العواكس
قدح الثيرستور
دارات توليد النبضات
إشارة التزامن
Voltage and current Converters
Power Transmission using High Voltage Direct Current systems
Rectifiers and Inverters
Thyristor firing
Synchronizing signal
نقل الطاقة الكهربائهة بالتوتر المستمر عالي التوتر
المزيد..
The aim of this study is to calculate the electrical field (EF) of some
types of high voltage insulators by using numerical methods. There
are different methods, which are used to do this, finite element is
the most important one.
It is possible
to find EF in 2D or 3D systems by using
Matlab/pdetool, which distinguishes with big capabilities in
calculation and view the results, additionally, it is available, cheap
and can save time and money for doing this important calculations
in high voltage applications .
The pollution is one of the most important problems facing the
electrical networks, especially in the Syrian Arab Republic, and
after that expanded of pollution sources on the one hand, and
because the power supply has become related to all economic
and daily life sections.
The polluted insulators problem is one of the most important cases, that faces the electrical networks especially in Syrian Arab Republic because the sources of pollution expand more and more, On the other side, the electrical power supply is related
to the operation of all commercial and daily sectors.
The environmental pollution on the insulators generally causes general breakdowns in the electrical power supply networks of wide areas, This makes great economical losses in all sectors that are related to electrical network.
In this research, the distinct values of insulators pollutions are defined. We then find the relationship between the mentioned values and flashover voltage of polluted insulators in the laboratory. The results of the tests apply on the natural polluted insulators in the outsides. Finally, comparison measurements are made on naturally polluted insulators, and the appropriated procedures to limit the pollution effects .
The problem of gliding discharges on high voltage equipment is faced in practice, coith inclined interface, such as cable terminations, bushings.
Many researches present very important results about the relationship between the applied voltages and
this partial discharge . But studies about the insulation systems that have small cross capacitor or that have air gaps are limited, considering many points, one of them: the discharge procedure looks
like the partial discharge in insulators, with longitudinal interfaces.
Achieving precise relationships for such systems and finding the actual discharge behavior gives high scientific efficiency and important application for design of high voltages devices, especially when high voltages, which are changing with time voltage like alternatring and lightning voltages, are applied.
There are tens of power transformers working in the Syrian high voltage network with rated voltage over 11 kV. and rated power over 10 MVA. These transformers have more than 15 years in service and since then only routine maintenance was carried on f
or this transformers.
IEC instructions and manufacturer instructions indicate that many tests, measurements and checking have to be done for transformers .But due to the fact that measuring apparatus and testing equipment are very sophisticated and very difficult to be found at sites where power transformers are mounted, the checking and the measuring of the transformer characteristics seem to be about impossible .
It is known that due to aging , the characteristics of electrical insulation materials used in high-voltage equipment are diminished and the probability that an electrical fault to appear is more evident .
To improve the running of power transformers in high-voltage network and to reset the characteristics of the insulation materials of power transformers to their nominal values, some new techniques are used to revitalize power transformers in their site at substations without moving them to specialized repair factory or workshop.
