Stacked chart method

One of the very important steps in designing an enterprise power system is determining the design loads instead of simply adding installed capacities.

Estimated maximum power consumption electrical receivers enterprises, is always less than the sum of the nominal powers of these receivers. This is due to the incomplete use of the capacity of the electrical receivers, the different time of their operation and the provision of working conditions for the service personnel.

The degree of capital investment in the organization of the power supply depends on the correct assessment of the expected electrical loads. Overestimation of expected loads leads to higher construction costs, overspending of materials and an unjustified increase in delivery capacity.

Underestimating the loads or designing the power supply without taking into account the future growth of production capacity can lead to additional energy losses, equipment overload or the need for radical restructuring of the power supply system.

To determine the design loads, the most commonly used method of stacked diagrams.

The method is applicable when the nominal data of all electrical receivers of the enterprise are known, taking into account their location on the territory of the enterprise.

Determine the average load of the receiver groups for the maximum busy shift Pcm and the calculated half-hour maximum Pp: Pcm = kiRnom.

Expected maximum load: Rr = kmRcm,

where km is the maximum coefficient, in this case the active power obtained according to the graphs, depending on the utilization coefficient and the effective number of energy consumers.

A maximum coefficient characterizes the excess of the maximum load over the average for the maximum loaded shift. The inverse of the maximum coefficient is called the filling coefficient of the load curve kzap:

Load calculations are performed for active and reactive power.

The disadvantage of the stacked chart method is that it does not include a load prediction element.

Calculation procedure using the stacked diagram method:

1) all electrical consumers are divided into groups that are homogeneous in terms of operating mode with the same values ​​of utilization factors and power factors,

2) in each group of electrical receivers and for the node as a whole, the limits of their nominal powers and the reduced number of receivers are found, while all electrical receivers are reduced to PV = 100%,

3) count nominal power of the node,

4) is determined for groups of electrical consumers utilization factor and power factor cosφ according to the reference tables and the characteristics of the equipment,

5) determines the active and reactive energy consumption for the busiest shift: Qcm = Pcmtgφ,

6) determines the total active and reactive load for the node for different groups of electrical receivers,

7) define a weighted average value of node utilization power factor from tgφuz:

8) determines the effective reduced number of energy consumers np,

9) taking into account the maximum coefficient, determine the calculated maximum load,

10) determine the total power:

and rated current: