Substations and Maximum Demand

From the information you provided you can not get the max demand. The max demand is the sum of the two demands but they must occur at the same time. You will have to check your data and determine the maximum sum of the substations.

I believe a simultaneous reading of both with a minute by minute time scale would get you a very realistic load rate map to reference from. There could be peaks way above what you mentioned that only last a few minutes that could point out critical system limits or weaknesses you may need to be aware of.

You have a number of ways to do what you want to do which is to determine the maximum load on your substation. You will need to determine the load on your feeders and then balance the load on the feeders as well as balance the load on the substations by switching your feeders to equalize the load on your station transformers.

What I have done in the past is to install three or more sets of digital, clip-on recording amp meters on the phases at equidistance on your feeders. Ideally this will be done when your temperature is at or near maximum for three or four days in a row so that everything is reaching its maximum load on your system. Read your amp meters at the end of the three day period and plot your readings on your system feeder map. You can then begin switching your feeders to balance the loads on your station transformers as well as balanceing the load on your feeders. Remember to leave enough capacity on each transformer to asorb the load from at least one of the feeders from the other station transformer for emergency outages.

The second way to do this is similiar to the method above but it uses manpower and radios to accomplish the same thing. With your cost of labor in India you may want to use men with "hot sticks" and ammeters to check the load on the feeders at pre-determined locations. Again, do this in the middle of a hot period so that every customer is running their systems to a maximum load. Locate your engineer at the substation with an assistant to operate the mobile radio. Station your men with the ammeters and an assistant at the pre-determined locations on the feeder lines. At 15 minutes intervals for two hours during the hottest portion of the afternoon have the engineer at the substation write down the temperature and request an amp reading from each of the teams in the field. This will give you a simultaneous overview of your system load at a certain temperature. Once you have this you can model your distribution system to balance your load and to plan for emergency switching to restore service to your customers.

Dear,

you must be having a common tvm - tri vector meter on the incomer of 11kv receiving power. this meter must be recording the total power consumption of the plant.

Maximum demand is the maximum of average demand in kva recorded in every 30 miniutes interval.

What you have recorded were at different times : 9 am / 14 pm. So, sum of 400 + 350 may not be the correct demand of plant on the system .

Every 30 min. time slot - average of demand recorded for both substations.

Sum of these demand for every 30 min. time slot.

graph - demand vs. time slot.

Maximum reading recorded is the total demand of your plant.

Hi Friend,

Can u give example on how to calculate the maximum demand if I have to 2 MSB?

Regards,

Raj,

There are several factors that intervene in calculating power/load:

1. Demand factor: ratio of maximum demand/total connected load, always <=1

2. Diversity factor: ratio of maximum demand of the system components/maximum demand of the system, always > 1

3. Load diversity: difference between peak of coincidental and noncoincidental load for a certain period of time; (measured in kW or kVA, etc)

4. Load factor: ratio of average load/peak load over a certain period of time, always <=1

5. Demand: power requirement at a certain moment or average power required over a certain period of time (kW,kVA, etc)

6. Connected load: Power obtained by adding all connected component load, equal to noncoincidental peak load for the system (kW,kVA, etc)

In your case you have the maximum demand for MSB1 (measured) and the maximum demand for MSB2 (measured). The system consists of 2 components. The max demand (non-coincidental) is the sum of the 2 loads. For the max coincidental, add the load of MSB1 and MSB2 at different times and see which the maximum is (It might be at another time, not necessarily when one of them is max).