Explanation

This simulator has 3 sliders which allow you to alter the supply voltage from 0 to 240V and the resistances of the supply cables and a load on a circuit.

Sliders can be dragged to approx positions and then fine tuned by using left and right arrows.

Checkboxes also allow the values of the circuits equivalent resistance and drawn current to be shown (as per resistors in series calcs). Two others show what the voltage drops would be across these cables and load along with the power consumed by the cables and load.

By changing these parameters you can investigate the effects of various combinations of cable resistaOn changing these sliders the values in the Ohms Law triangle in the top right adjust automatically and a graph changes.

It has two purposes

1. Investigating what happens to volt drop and power consumed in the cables feeding a circuit when their resistances are very low compared with the resitance of the load and how these change when the resistance of the cables approach those of the load they are feeding.
2. As away of self testing by unchecking the answer boxes. Setting up questions with various combinations, calculating your answers and comparing against the answers the toold provides when they are unchecked.

Ohms Law

At a constant temperature, the electrical current flowing through a fixed linear resistance is directly proportional to the voltage applied across it, and also inversely proportional to the resistance.

"The electrical current flowing through a fixed linear resistance is directly proportional to the voltage applied across it" means that as the voltage increase by a certain percentage so will the current.

"inversely proportional to the resistance" means that as the resistance increases the current will decrease..

Tasks

The following steps should be carried out and notes taken on what you notice.

1. Click all checkboxes to reveal circuit resistance, current drawn, volt drops and wattages of each part of the circuit.
2. Reduce cable resistance towards zero or 0.01 to mimic a very short run of high CSA cable Calculate the current using Ohms Law triangle and covering over the bottom left corner to reveal that you need to divide the voltage by the resstance.
3. Set voltage to 230V.
4. Alter the load resistance value until the load wattage reaches a value such as 3kW (Imm Heater) or 9kw (shower). The resistance values of these common resistive loads are handy to know for detecting healthy states of elements and identifying between faults and appliances left connected during IR tests.
5. Gradually increase the cable resistance slider noting the effect it has on the volt drop and power wasted or given off in the cables.
6. Continue sliding until you get to the point where Volt Drop reaches the permitted limit (dont forget to halve the allowed limit as the allowed limit represents that than can be dropped on Phase and Neutral whereas this tool shows them separately.
7. Note how when you are at this limit of Volt Drop in the cables how the appliance is now no longer consuming as much power as before (meaning an Immersion Heater will take longer to heat the water or a shower will runn cooler) and how the cables are now consuming power.
8. This power consumed by the cables is not dangerous at these Volt Drop limits as it is spread along long lengths but tends to demonstrate that cables for a circuit will run warmer or hotter if drawing to much current for their CSA.
9. Reduce the cable resistance to between 0.6 and 0.66 of its resistance value (This value roughly represents the resistance drop when increasing CSA to the next size up when length of circuit and current drawn stay the same).
10. Note that along with a reduction in volt drop in the cables the load now draws more power and the cables draw less.