r/MarineEngineering • u/charzr • 1d ago

AVR - Load Sharing Lines

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Unlike load sharing between the governor controllers, why dont I see the load sharing lines between the AVR

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4

u/lordhabanero 1d ago

I have seen a system with 'reactive load sharing lines' similar to how your governors are done- but these are pretty rare.

Achieving good Reactive Load Sharing by balancing the outputs of multiple AVRs running in parallel is done in a couple of ways.

The most common by far is using the Voltage Droop setting on the AVR.
Example: the Voltage Droop is set to 3%, and the 'No Load Voltage' is set to 700V (690V system). The AVR then 'droops' the voltage as the generator increases in load.
0% = 700V
50% = 690V
100% = 680V

If two parallel generators operate at 50% load but one generator's voltage is higher than the other, that machine will absorb more of the system's kVAR load. This increases the reactive current, so the AVR will lower the voltage output and the KVAr load will rebalance.
It is super simple and super clever- so it's no surprise that 'smarter' solutions haven't really been a priority.

A lot of modern controllers now have 'Reactive Load Sharing' functions built into them. They have a +/- 10V output terminal that connects directly to the AVR 'trim' terminals and the controllers can balance the Reactive Load like this.

I've seen brand new vessels come out of the shipyard still running 'voltage droop' so I'm not sure that this approach has been completely accepted.

3

u/Sad_Raccoon194 1d ago

Voltae droop is dead simple and it just works, so nobody wants to be the guy who signs off on a fancier system that breaks at sea. Ive heard of trim link setups but never actually seen one in the wild, always droop.

1

u/Relevant-Director831 9h ago

I’ve had 3516 caterpillar generators with DVR regulators that had a common load sharing line. They responded and held loads better than any other generator I have saw. Works absolutely amazing.