Any electrical scheme for premise( home/ office/ factory) generally includes current sensing products like MCB, ELCB, RCCB, RCBO, which do not react to voltage changes
If the voltage was to change from 230V to above 300V, the current protections will not react and as such there will be no protection available for over voltage. In such situation, one of weakest equipment in the line will get damaged, resulting in internal short circuit in components, which would then trigger the MCBs to trip and shut the supply preventing further damage. One equipment will be sacrificed to save other equipment and larger catastrophe.
While this happens there is possibility of sparking and any plastic covering, curtains, or wooden item can catch fire and whole premise is gutted down.
An incident like this has happened in Mumbai, some years back when a TV on standby mode got damaged and curtains beside the TV caught fire and whole apartment was up in flames. As there was no one at the house, tragedy could not be averted. This is true for many working professional with working spouses. Also with home automation systems adopted in homes, most of equipment will always be on standby.
One more striking information about the incident was that in the same building 8-10 other flats had issue of TV, refrigerator damage at the same time. This is classic case of neutral open or floating neutral which caused 440V in one of the phases and everything ON was damaged.
Just like short circuit 440V can also happen in any electrical circuit, however unlike short-circuit, there are no safeguards for 440V in any homes office or factories.
What causes 440V in single phase?
440V in single phase is an accident and can happen due to following reasons:
- Neutral open or floating neutral
- Trees falling on over head wire causing double phasing
- 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
Spikes & surges
Even if one ignores accidental issues like neutral open or in general over voltage, every premise( home/ office / factories / shops etc) experiences min 100-200 spikes every day
Every switching operation (both ON & OFF) creates spikes. Some equipment switching every day
- Lights – 2-3 times
- Fans- 5-6 times
- AC thermostat- once every hour
- Refrigerator- once every 2 hours
- Lifts – 15-20 time in one hour
- Geysers- 4-5 times a day
List goes on. 100-200 is conservative estimate. Multiply this with no of apartments/ galas/ offices in the building. All of them are getting supply from the same incoming cable in the building. Each individual premise is generating spike which is experienced by other premises in same building.
These spikes damage the electronics over a period of time. Also electronics now a days are designed to last for only 5-6 years. After this period the support for particular model is removed and spares are difficult to get. With easy EMIs available , one opts for buying new product instead and get a buy back. This also contributes to e waste
Most of people assume that lightning rod on the roof makes our premises safe. This is only partially true, Lightning rod prevents structural damage and gives a safe path to lightning to go to ground. While it travels down through the wire to earth pit, the magnetic flux gets created and any metal surface or utility wire in flux will conduct the lightning impulse in the main line. This can damage the electronics.
We have solutions for all the above mentioned issues which are generally ignored by most.