Load Characteristic PDF

Load Characteristic  Load Characteristic Demand: “The demand of an installation or system is the load at the receiving terminals averaged over a specified interval of time. Here, the load may be given in kilowatts, kilovars, kilovoltamperes, kiloamperes, or amperes. Demand interval...

Load Characteristic  Load Characteristic Demand: “The demand of an installation or system is the load at the receiving terminals averaged over a specified interval of time. Here, the load may be given in kilowatts, kilovars, kilovoltamperes, kiloamperes, or amperes. Demand interval: It is the period over which the load is averaged. This selected ∆t period may be 15 min, 30 min, 1 h, or even longer. Of course, there may be situations where the 15 and 30 min demands are identical. Maximum demand: “The maximum demand of an installation or system is the greatest of all demands which have occurred during the specified period of time” Load Curve Load Duration Curve 4/24*100 = 16.67 % 2.00 pm 337 MWh =14.04 MW  Diversified demand (or coincident demand): It is the demand of the composite group, as a whole, of somewhat unrelated loads over a specified period of time. Here, the maximum diversified demand has an importance. It is the maximum sum of the contributions of the individual demands to the diversified demand over a specific time interval.  Utilization factor: It is “the ratio of the maximum demand of a system to the rated capacity of the system. Therefore, the utilization factor (Fu ) is  Plant factor: It is the ratio of the total actual energy produced or served over a designated period of time to the energy that would have been produced or served if the plant (or unit) had operated continuously at maximum rating. It is also known as the capacity fact or the use factor. Therefore, It is mostly used in generation studies. For example  Load factor: It is “the ratio of the average load over a designated period of time to the peak load occurring on that period. Therefore, the load factor FLD is :  Diversity factor: It is “the ratio of the sum of the individual maximum demands of the various subdivisions of a system to the maximum demand of the whole system. Therefore, the diversity factor (FD) i For example, an oversized motor 20 kW drives a constant 15 kW Demand Factor load whenever it is ON. The motor demand factor is then 15/20 =0.75= 75 %. Demand Factor is expressed as a percentage (%) or in a ratio (less than 1). The load factor is closely related to and often confused with the demand factor. The major difference to note is that the denominator in the demand factor is fixed depending on the system. Coincidence factor: It is “the ratio of the maximum coincident total demand of a group of consumers to the sum of the maximum power demands of individual consumers comprising the group both taken at the same point of supply for the same time. Therefore, the coincidence factor (Fc ) is Load diversity: It is “the difference between the sum of the peaks of two or more individual loads and the peak of the combined load. Therefore, the load diversity (LD) is  Contribution factor: Ci is defined as “the contribution factor of the ith load to the group maximum demand.” It is given in per unit of the individual maximum demand of the ith load. Therefore, We have  Loss factor: It is “the ratio of the average power loss to the peak-load power loss during a specified period of time Therefore, the loss factor (FLS) is  Example 2.3 There are six residential customers connected to a distribution transformer (DT), as shown in Figure 2.5. Notice the code in the customer account number, for example, 4276. The first figure, 4, stands for feeder F4; the second figure, 2, indicates the lateral number connected to the F4 feeder; the third figure, 7, is for the DT on that lateral; and finally the last figure, 6, is for the house number connected to that DT. Assume that the connected load is 9 kW per house and that the DF and diversity factor for the group of six houses, either from the NL&NP Company’s records or from the relevant handbooks, have been decided as 0.65 and 1.10, respectively. Determine the diversified demand of the group of six houses on the DT DT427.  Example 2.4 Assume that feeder 4 of Example 2.3 has a system peak of 3000 kVA per phase and a copper loss of 0.5% at the system peak. Determine the following: a. The copper loss of the feeder in kilowatts per phase b. The total copper losses of the feeder in kilowatts per three phase Solution  Example 2.5 Assume that there are two primary feeders supplied by one of the three transformers located at the NL&NP’s Riverside distribution substation, as shown in Figure 2.6. One of the feeders supplies an industrial load that occurs primarily between 8 AM and 11 PM, with a peak of 2000 kW at 5 PM. The other one feeds residential loads that occur mainly between 6 AM and 12 PM, with a peak of 2000 kW at 9 PM, as shown in Figure 2.7. Determine the following: a. The diversity factor of the load connected to transformer T3 b. The load diversity of the load connected to transformer T3 c. The coincidence factor of the load connected to transformer T3  Example 2.6 Use the data given in Example 2.1 for the NL&NP’s load curve. Note that the peak occurs at 4 PM. Determine the following: a. The class contribution factors for each of the three load classes b. The diversity factor for the primary feeder c. The diversified maximum demand of the load group d. The coincidence factor of the load group Solution Solution