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440V protection for solar inverter


What causes 440V in single phase?

440V in single phase is an accident and can happen due to following reasons:

  1. Neutral open or floating neutral
  2. Trees falling on over head wire causing double phasing
  3. Transformer blast/ transformer fault

Neutral open or floating neutral

In all premises we have star connected system, phase to phase voltage is 415V,  and Phase to neutral voltage is 230V

Figure above shows distribution system of typical facility with equally distributed load. Points A, B, C show possible places of neutral open

If neutral breaks at point A:

The voltage will continue to be normal till such time that the load are equal in all phases. Any imbalance in the load will cause changes in the voltage in phases. Technically all the phases are connected together and the currents cancel out so neutral is formed.

If neutral breaks at point B:

B phase will have 415 V. R & Y will still complete path through each other and effective voltage between then being 415V which will be equally dived across both loads. If the load changes the effective voltage across the loads can be calculate using the voltage divider rule

eg: voltage  across L3 can be calculated as (L3/(L2+L3))x 415V

If neutral breaks at point C:

R phase will have no continuity and Y&B phases will have voltage based on conditions discussed in above points
Trees falling on over head wires

Trees falling on over head wires or tree growing through them can cause phase to phase short circuit. Ideally there are breakers installed on lines for safety in such situation, but some times they do not operate due to rusting and non maintenance or some times lineman themselves bypass the breakers . this can cause 440V in secondary side of transformer or trigger Transformer blasts.

Transformer blast/ fault

These are generally  maintenance issues, and they can some time result in double phasing and 440V in single phase. In sept 2021, there was an incident in sangli where 400-500 homes experienced 440V in their homes and all equipments ON at that time like  TV, refrigerators, etc were damaged.

Other than this routine maintenance  or upgradation work involving underground cables can also trigger neutral open situation causing 440V even in city areas.

There will always be arguments on the probability of such accidents happening in cities being low, but if you look at even a district in general, there are atleast 10-15 incidents daily in different pockets of the region

Problem with solar inverters

Most solar inverters have over voltage protection, but in situation like neutral open , trees falling on over wires and transformer blasts, voltage can shoot up to 440V in any phase till the situation is corrected. In such situations all such solar inverters will get damaged in less than 2 mins.

We offer solutions for protection of solar inverters in such situations, which can withstand 440V for more than 24 hours.

You can get in touch with us over the Whatsapp on 9769996205 or write to us by filling up the form

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