As mentioned before, during its service a transformer produces heat due to losses. This heat must be dissipated from the room where the transformer is installed. For this purpose, one must ensure that there is adequate natural ventilation in the … read more
When selecting the type of transformer correctly electrical engineer needs to know its different electrical and thermal properties and the resistance to stresses due to faults or normal service of the transformer itself. This is crucial to know. Source: … read more
Temperature rises depend not only on the load and the overcurrents which may be detected by the protection devices, but also on environmental factors (inefficiency of the cooling system, fault on the forced ventilation and increase of the room temperature) … read more
Zones are used to divide the sections and are designed in such a way that they are overlapping across the section switches, so the whole system is protected as shown in Figure 7 below. In a double busbar layout system … read more
quires dedicated CTs which adds extra cost. During iting varistor that is utilized to absorb energy. phase and earth fault settings to be identical. High Impedance Differential Protection High impedance differential protection scheme has been in use for over fifty … read more
The Modifications for the scheme to suit substation extension are easy. It utilizes overcurrent elements that are already supplied by the feeder protection relays. It requires minimal cost in comparison with the differential protection scheme. It has faster … read more
The first are generally used in the air distribution system. The second are generally more widely used because of their capacity of response to high currents within a few milliseconds.The high response speed is the parameter which offers the capacity … read more
The disadvantage for this arrangement is when a fault is at the short zone: the circuit breaker will open but the fault current will still be flowing if there is a source of power in the circuit. This is not … read more
A fault on the low-voltage side near the transformer terminals causes a thermal stress and a mechanical stress on the transformer itself which are functions of the values and duration of the fault. Transformers are designed to withstand short-cir- cuits … read more
the threshold of 3°K. When there are two monitoring systems, one gives the alarm signal and the other the release. The temperature values of the two systems deviate by 20°K. When the protection relay is fed by the mains … read more
As previously stated, overload, is fundamentally associated to a temperature rise which is the real component to be kept under control, because its effects could lead to the rapid deterioration of the insulation materials and to … read more
For correct protection against overloads the current values absorbed by the system must not exceed a threshold between 110 and 150% of the rated current. Protection against overload may be provided on both the medium-voltage side and the low-voltage … read more
For cast resin transformers, the cooling component is air and thus it takes longer to reach the operating temperature. In these conditions cast resin transformers may be more overloaded and thus may be used in systems with loads where there … read more
In an industrial installation, the overload can last for a short or long time. In these installations the main distribution board equipped with protective circuit breakers against overload and short-circuit is always immediately downstream of the transformers. Management of … read more
Frame Earth Protection Frame earth protection for busbars has been extensively used in the past. This method can be applied to various layouts of busbar protection, each having certain capability. Frame earth protection schemes are still in existence and … read more
This system divides the busbar into sections and the protection is also done separately. This is done by dividing the frame in to sections each using a dedicated earth conductor. Each section consists of a separate CT and a protection … read more
There are estimated digitally (block 3) and the differential (block 4) and restraining (block 5) signals are calculated. The magnitude of the differential signal is compared with a threshold and an appropriate flag indicating operation of the unbiased bus … read more
Differential protection operation directly uses the Kirch- hoff’s Current Law where it is required that the currents going into a node are equal to current leaving the node. When the sum of the currents is not equal to zero by … read more
The temperature may be checked using Pt 100 temperature sensors or thermometers. An alternative solution is to use PTC sensors, which however has the disadvantage that the temperature cannot be displayed. These systems are used to check the temperature of … read more
This will lead to a complete blackout. Precision and reliability are important factors when designing a busbar protection scheme. Literature review has shown that small distribution substations used for medium Figure system with time dfecrimlrata, voltage make use of … read more
Busbars in T&D substations Source: EEP Busbars play an important role in power trans- case of a fault, current on the busbar becomes mission and distribution. They are employed as high, resulting to mechanical destruction which a central distribution … read more
Faults caused by overvoltages concern the insulation of the transformer and its components and may be divided into: Faults between the turns of the-same winding (most frequent case); Faults between windings; Faults between the stressed winding and a touching conductor … read more
The first step in managing your building’s energy is to understand exactly how much you use and where you use it. With this information at hand, you can highlight areas for improvement, which in turn will help you become more … read more
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المقالات منقوله من مصادر اخرى يرجي التحقق من صحه المعلومات الوارده بها
المقالات منقوله من مصادر اخرى يرجي التحقق من صحه المعلومات الوارده بها
