Problems

Problem

Assume that the loading data given in Table 2-2 belongs to one of the primary feeders of the No Light & No Power (NL&NP) Company and that they are for a typical winter day. Develop the idealized daily load curve for the given hypothetical primary feeder.

Problem

Assume that annual peak load of a primary feeder is 2000 kW, at which the power loss, i.e., total copper, or I2R, loss, is 80 kW per three phase. Assuming an annual loss factor of 0.15, determine:

(a) The average annual power loss.

(b) The total annual energy loss due to the copper losses of the feeder circuits.

Solution

(a) Average power loss

= power loss at peak load x FLS = 80 kW x 0.15

= 12 kW

(b) The total annual energy loss is

TAELc = average power loss x 8760 h/yr = 12 x 8760

= 105,120 kWh

Problem

Assume that there are six residential customers connected to a distribution transformer.

Assume that the connected load is 9 kW per house and that the demand factor 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 distribution transformer DT427.

Solution

The diversified demand of the group on the

distribution transformer is

Problem

Assume that feeder 4 of Example 2-3 has a system peak of 3000 kVA per phase and a copper loss of 0.5 percent 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

(a) The copper loss of the feeder in kilowatts per phase is

I2R = 0.5 % x system peak

= 0.005 x 3000 k VA

= 15 kW per phase

(b) The total copper losses of the feeder in kilowatts per three-phase is 3128 = 3 x 15

= 45 kW per three-phase

Problem

Assume that there are two primary feeders supplied by one of the three transformers. One of the feeders supplies an industrial load which occurs primarily between 8 A.M. and 11 P.M., with a peak of 2000 kW at 5 P.M. The other one feeds residential loads which occur mainly between 6 A.M. and 12 P.M., with a peak of 2000 kW at 9 P.M., as shown in Fig.

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

(a) From Eq. the diversity factor of the load is

(b) From Eq. the load diversity of the load is

(c) From Eq. the coincidence factor of the load is

Problem

Use the data given in Problem 1 for the NL&NP's load curve. Note that the peak occurs at 5 P.M. 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