[CENTER]Very improtant Concepts
in this subject i will examine some important concepts in transmission and distribution systems .
Demand: it’s the averaged load of the receiving terminals at specific interval of time. Usually loads is given by KA , KVA , KVAR , KW to get the current , because we build all our consideration on the current so we can choose : C.B or fuse , switch and wires.
Demand interval : the period over which the load is averaged t.
Demand variation curve : it’s a curve that shows that changeable of the load over a specified interval of time like : daily , weekly , monthly and annually.
Demand duration curve: it’s a curve that shows the duration of each demand where the x-axis is the duration period of different levels of demands.
Maximum demand: it’s the greatest of all demands which have occupied during the specified interval of time.
Diversified demand (coincident demand):
It’s a demand of composite group of loads which are unrelated at specific interval of time.
It’s a sum of the demands of a group of loads with no restriction on the interval to which each demand is applicable.
Very important factors:
1- Demand factor : it’s the ratio between maximum demand of a system to the total connected load of the system.
DF= Dmax/Dconn. <1
It’s indicator of the simulitaneous operation of the total connected load.
Connected loads: the sum of the continues rating of the load consuming apparatus connected to the system or any part .
2- Load factor : it’s the ratio of the average demand over a specific interval of time to the peak load occurring to that period.
3- Diversity factor : it’s the ratio of the sum of the individual maximum demands of subdivisions of a system to the maximum demand of awhole system.
Fd= sigma(i=1 to n) (Dimax) / Dmax
We know Dmax = Dconn. * DF.
So : Fd = sigma (i=1 to n)(Diconn. DFi) / Dmax.
4- Coincident factor : it’s invert of diversity factor
5- Load diversity : it’s the difference between the peak of individual different loads and peak of the whole system or the peak of the all loads.
LD = sigma(i=1 to n) (Dimax) – Dmax
6- Contribution factor : it’s agiven in per-unit
Dmax = c1D1max + c2D2max+……+cn*Dnmax
Fc = sigma (i=1 to n) (Ci Di max ) / sigma (Dimax)
7- Loss factor : it’s the ratio of the average power loss to the peak (Maximum) load power loss during a specified period of time
Fls = Pavls/Pmaxls [/center]