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Generally any equipment will get damaged due to 3 primary reasons.
- Lightning or surges
- Temporary over voltages.
First 2 reasons are taken care of in design and considered as per worst case scenario.
However safeguards for temporary over voltage are generally not taken, certainly not considered as per worst case scenario.
In secondary side of LT transformer , worst case scenario is 440V in single phase.
It happens more often than expected.
Reasons for 440V coming in your supply
- Neutral open condition
- Double phasing
Causes of neutral open.
- Uneven load distribution
- Loose wiring.
- Accidental breakage
- Maintenance work errors
Causes of double phasing
- Trees falling on overhead wires
- Touching of overhead wires running through trees.
Majority of projects are located outside of city limits due to roof space constraints and industry requirements. Such scenarios are very common
Not one of the available solar inverter can handle a continuous over voltage of the above nature and will get damaged resulting in down time.
There is strong need of safeguard against such issue in design stage itself so that such issues can be tackled with min losses.
To illustrate, if there is short circuit or lighting strike, the system is designed to handle it. However for continuous over voltage there is not a single solution that can be offered.
There is infact no solution incorporated for 440V in single phase. Most of integrators rely on the inverters capacity of handling voltage fluctuation, and they will definitely get damaged in such a situation.
This is where it is recommended to take cognizance of potential problem that can be taken care in design stage itself.
We specialise in this area i.e. Neutral open and double phasing protection.
You can see our website www.microsystemservices.com for details on how we can add value to solar field.
AVR means Automatic Voltage Regulation.
What it does is to regulate the mains voltage within a limited range. In the case of your UPS, it boost +12% when the incoming voltage is too low. Let’s say the incoming voltage is at 200 volts, the output then goes to 224Volts, +12% of 200 volts, which is still acceptable for most UPSs. When the UPS output reaches let’s say, 230V with the boost mode on, then the UPS sends a command to a component called relay so that the +12% compensation is turned off.
Basically the voltage regulation is a series of power transformers, it can either be step-up transformers or a step-down transformers They basically do the same thing a 220V to 110V step-down transformer does, or a step-up transformer does, when it gets 110V and transforms to 220V. The UPS senses the incoming voltage and commands a series of relays to select a different transformer output or “tap”, as they call it.
An automatic voltage regulator can only work within a limited range. Their “taps” are at a fixed rate lets say, +10volts. If the UPS have a 12% voltage trimming option and the incoming voltage reaches 270 Volts, it can only trim 12% of that, which will result in 237 Volts.
Voltage regulator transformer can have as many “taps” as its developer wants, but it makes the unit much heavier, it wastes more energy and generates more heat. It doesn’t matter if the AVR has four “taps” or sixteen taps, it is still slow for suppressing voltage surges
Surge suppression is basically made to protect against high energy and fast rising surges or spikes that can be caused by lightning, electric motors being turned on or turned off, etc. Surges are essentially fast rising spikes and voltage swells are slow rising and low energy in nature. Surge suppression can in some cases reduce voltage swells, but this is not its main purpose.
Surge protection is basically comprised of a component called MOV – Metal Oxide Varistor.
An MOV works at diverting surges to ground. When operating at its nominal voltage, or the mains voltage, the varistor acts like a resistor with its resistance tending to the infinite, so it does not conduct electricity to ground at this state. When there is a fast surge, it instantaneously reacts (in nanoseconds) by decreasing its internal resistance, allowing the excess energy to flow to ground.
The voltage regulator cannot act as fast as an MOV for suppressing high power and fast rising surges and would not be capable of that because of the nature of a power transformer. High energy surges must be diverted to ground and power transformers do not do that. Compared to the speed of an MOV, the voltage regulator is like a turtle.
There are some disadvantages regarding the use of MOVs for suppressing voltage swell. MOVs degrade very fast if frequent voltage swell are imposed to it, it gets too hot and it’s internal chemistry degrades. MOVs are made to react fast and come back to it’s initial state very quickly as well, which happens when a power surge occurs. That’s why manufactures of surge protective devices use an MOV that only triggers itself when the voltage is much higher than the mains voltage. If the MOV starts to conduct too early, it will degrade itself very quickly and on all power grids a relatively high number of fast duration swells, do happen
What an MOV doesn’t do…
An MOV does not provide equipment with complete power protection. In particular, a MOV device provides no protection for the connected equipment from sustained over-voltages that may result in damage to that equipment as well as to the protector device.
An MOV provides no equipment protection from inrush current surges (during equipment start-up), from over current (created by a short circuit), or from voltage sags (also known as a brownout); it neither senses nor affects such events.
Susceptibility of electronic equipment to these other power disturbances is defined by other aspects of the system design, either inside the equipment itself or externally by means of a circuit which typically consists of a voltage-sensing circuit and a relay for disconnecting the AC input when the voltage reaches a danger threshold. See OVCD).
In nut shell…
The AVR and the surge suppression solve two different problems. They’re complimentary technologies but do not ensure total power protection.
The AVR can adjust the voltage of the line within a limited range to compensate for the voltage being too high or too low. However, the AVR does not respond quickly enough or have wide enough compensation to handle surges.
Surge protection is capable of putting huge surge voltages into ground very quickly, but won’t adjust the long-term voltage of the line as the AVR does.
Both however are ineffective against sustained high voltages. in neutral open condition , they themselves will need protection.
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How often has this happen to you… You buy a brand new Plasma TV , Refrigerator, washing machine etc. just to find that it stops working with in the warranty period.
You call up the vendor and ask for replacement / repair of that equipment. Have you considered that the quality of power at you house may be bad? Even if you knew, would you acknowledge to the vendor?
Probably not!!! because you want a free service. Thats precisely what happens when any equipment fails. Equipment vendor is in a soup!!!
Power conditions are not good at all places. Voltage fluctuations are not something you can observe, not with out a voltage recorder definitely. But that wont be feasible at all times.
Effects of voltage fluctuations are not understood until a very large catastrophe occurs and appliances are damaged.
Such a case has happen even in Metropolitan cities like Mumbai. There was a electrical fault at main distribution board of the house of very distinguished business person, wherein the neutral wire was burnt. This cause the voltage to shoot up to 440V ( this is called the neutral open condition). At this voltage all the equipment in his house got damaged. MCB/Fuse didnt react at all, and it will not. because MCB reacts to over current and not over voltage
He promptly called the appliance vendors and got the repairs done all free of cost as they were under warranty.
But here the manufacturer/ vendor had to bear the service cost. This includes salary for the day of the service technicians, changing of damaged components replacement of complete unit in some cases.
This cost is huge when you consider country-wide service.
We can help them reduce the events of such failures by more than 75%. This can improve the bottom line of the company.
Let us know in case of such problems at firstname.lastname@example.org. We will be glad to be of any assistance.
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