في البدايه أحب أن أشكر كل من دعم موضوعي المتواضع في توزيع الكهرباء وأتوجة بالدعاء الي الله لأخونا الحبيب عبد الرحمن بالرحمة والمغفرة وتوسعة القبر وأن يكون روضة من رياض الجنة


وسنبدأبعن الله بشرح الحلقة الثانية :

Types of distribution system

*( A ) Depending upon the type of supply :

1. A.C single phase ( single phase loads only ) .

2. ( 3-phase ) , ( 3-wire ) 3-phase loads only .

3. ( 3-phase ) , ( 4-wire ) all types of loads.


*( b ) Depending upon the connection :

1. Radial system .

2. ring system .

3. inter – connection . >>( two or more generating station are
connected together)


* The advantages of radial system :

1. Its simplicity .

2. Low cost .

3. The amount of switching equipment is small and the protective relay simple .


* classification of distribution system :

>> According to the current :

1. D.C distribution

2. A.C distribution


>> According to the character of service :

1. General light and power .

2. Industrial power .

3. Railway .

4.Street lighting .


>> According to the type of construction :

1. overhead distribution system .

2. undergrond distribution system .


Disadvantages of radial system :

1. lack of security of supply :
When afault occurs on any section of the feeders anumber of consumers will be without supply for considerable period . " Singele feeder"


2. the end of the distributor nearest to the supply would be heavy loaded :
Using >> the radial system is normally used for rural distribution


Ring system

advantages :
1. less couper
2. Reduce the voltage drop between the points to which it is connected .
3. continuity of supply " more reliable" in the event of fault on any one section the continuity of supply to all consumer can be maintained by isolating the faulty section :
Using >> the supply bulk loads such as :

1. Industrial loads

2. medium or large commercial building

Primary Distribution Systems. It is that part of ac distribution system which operates at voltages (such as 3.3, 6.6, 11 kV or higher even) somewhat higher than that of general utility (400/230 V) and handle large blocks of power. As already mentioned in chapter
1. the primary distribution is universally carried out by 3-phase, 3-wire system.
Electric power from the generating station is transmitted, through extra high tension transmission lines at voltages from 33 to 400 kV, to various substations located in or near tht city. At these substations, called the secondary substations, the -/oltage is stepped down to 11, 6.6 or 3.3 kV with the help of power transformers for primary distribution.
The 33/11 kV secondary substations are usually located in the area having load requirement of the order of 5 MVA and normally a primary distribution line or a feeder is designed to carry a load of 1 - 2 MVA, so the number of feeders emanating from a secondary substation of 33.''11 kV i.s 3-4. For the load exceeding 8 MVA the secondary transmission is earned out at 66 kV so as to reduce the line losses and, therefore, secondary substations are 66/11 kV.
The number of feeders emanating from a 66/11 kV secondary substation is 6 — 8. The feeders may be radial, parallel, ring or inter-connected.


1. Radial Feeders. It derives its name from the fact that the feeder radiates from the secondary substation and branches into subfeeders and laterals which extend into all parts of the area served. The distribution transformers (11 kV(41;5)V) are connected to the primary feeders, subfeeders and laterals, usually through. fuse-cutouts. Radial feeder is the simplest, most economical and most commonly used one. It is advantageous for supplying power to heavy industrial load near the secondary substation, isolated loads, such as tubewells, and areas of low load density such as villages.
However, it suffers from the following drawbacks:









1. Poor reliability. When a fault occurs at any point on the feeder, supply to all consumers beyond the fault point towards the tail end gets interrupted.
2. In case of increase in load demand, the length of the feeder has to be extended and it may result in a greater voltage drop. It may cause the voltage towards the tail end to reach a value below the permissible value. This can be avoided by bifurcating the feeder but it will not prove economical.
2. Parallel Feeders. In a parallel feeder system, two radial feeders originating from the same or different secondary substations are run in parallel. Each feeder, though capable of supplying the entire load, shares the total load equally in normal conditions. Though this system is expensive but reliability is increased as in case of fault on one feeder, the total load can be supplied by the healthy feeder. Interruption of supply is only for the time duration, that i? taken in transferring the load from the faulty-feeder to healthy one either by manual or automatic switches. Such a system is employed wherever the continuity of supply is of greater importance.

3. Loop Feeders. In a loop feeder system, two or more radial feeders originating from the same or different secondary substations are laid on different routes of load areas. The arrangement having the ends of two feeders tied together through normally open switching devices is known as open-loop system while the arrangement having the ends of two feeders tied together through normally closed switching devices is called the ring main feeder or the ring-loop. This system is by far the most reliable for continuity of supply and gives better voltage regulation and less power losses.
The use of this system is prohibitive on account of very large investment involved. It is used where continuity of supply is the priority factor and thus large investment may be warranted.
Feeders and loop components must have sufficient reserve capacity to handle the load that may be transferred under abnormal conditions.

4. Inter-connected Network System. When the feeder ring main is energized from two or more than two generating stations or substations it is called the inter-connected network system, Because of inter-connected feeders, power can be supplied to all the distribution transformers even though a part of network may be out of service. Such a system provides better reliability and flexibility and is employed in large metropolitan cities where continuity of supply is the most important.

أعدكم بالمزيد في المواضيع الاخري انشاء الله

ما شاء الله عطاء متواصل وجهد تشكر عليه مهندس الشامي.......اسأل الله ان يجزيك خيرا......
ومثل ما وعدتنا ننتظر مواضيعك الجديدة........

|أقترح أن يقوم الاخوة الذين يقدمون المواضيع بترجمتها . حتى يستفيد منها الاخوة غير المتخصصين عند الاطلاع عليها . :crying:

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Thanks a lot