Calculating bus loading amounts to summing up all the loads that are connected a specific bus.
Circuit Mode
The calculation of bus load summary depends on the mode of the circuits. The circuit mode property can be Connected or Disconnected and it controls whether the loads are connected or disconnected to the bus. You set the circuit mode on the Circuit Common Properties dialog or in the Properties window. Setting the circuit mode to Connected means that power flows through the circuit and it acts as a connecting line between the power source and the consumer device. Setting the circuit mode to Disconnected interrupts the circuit connectivity and it means the power is not flowing therefore, the downstream connected loads or buses are not taken into account in the calculation.
The following situations can arise when identifying the buses that are connected to a particular bus:
Loads Connected Directly to a Bus
As shown in the diagram below, the loads are connected directly to the bus, which means that they are connected to the bus via a circuit or directly even without a cable. A load can be connected via a junction box or any other connecting item such as a panel, bus way, and so forth, all of which are transparent to the bus load association. Example:
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In the Electrical Engineer:
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In a single line diagram:
The software also takes into account loads that are connected in parallel and loads
that are connected in a daisy chain. For details, see Configuration H: loads connected in parallel and Configuration J: loads connected in a daisy-chain pattern.
Loads Connected Indirectly to a Bus (Via Converting Equipment)
In this case, the loads are connected to a bus indirectly. That is, the loads are connected through a transformer, a variable frequency drive, or any other converting equipment item within the circuit internals or external to the circuit.
In a single line diagram:
Buses Connected Via Feeder-Incomer Circuits
The image below shows a configuration of buses that feed downstream buses through a pair of feeder-incomer circuits.
As shown above, the loads that connect the upper bus are the direct loads as well as all the downstream connected buses which in turn also have loads that are connected to them directly. Any calculation of the upper bus also takes into account the downstream connected loads. Note that the software does not set any limitation on the number of downstream levels of buses for a network. The software makes a recursive calculation.
Buses Connected Via Coupler-Riser Circuits
Buses can also be connected to each other by sets of coupler-riser circuits. Such a connection is usually used for connecting buses of the same voltage level mainly for redundancy and backup purposes when one bus can take over the loads of the coupled bus in case there is a power source loss in one of the adjacent buses.
Bus 400V, 500A, 3PH and bus 120V, 500A,3PH are coupled (connected) by the coupler and riser circuits which in principle serve as mutual backups for power supply.