Guides · Faisalabad, Lahore, Punjab

Grid Voltage Rise: Why Your Inverter Trips on Sunny Afternoons

Short answer

If your inverter trips with a grid overvoltage or "grid voltage high" alarm around midday on sunny days, the usual reason is voltage rise: when your system exports power, the voltage at your connection point goes up, and if the local grid is already high, it crosses the inverter's safety limit and the inverter disconnects. It then waits, reconnects, and may trip again. The fix is an engineering job: checking the grid voltage, the AC cable, the inverter settings and how load is spread across phases.

Safety first

This is a diagnosis guide, not a repair guide. Voltage measurement at the distribution board involves live mains and must be done by a qualified electrician.

Diagram

Voltage rise at midday

Your export

Pushes local voltage up

Weak line

Long service cable, shared transformer

Trip

Inverter disconnects to protect the grid

Protection limits are not an owner setting.

How voltage rise works

Electricity flows from higher voltage to lower voltage. To push power out to the grid, your inverter has to raise the voltage at its output slightly above the grid's. Every cable between the inverter and the transformer has some resistance, so the more current you export, and the longer or thinner the cables, the bigger that rise.

In simple terms:

Most of the time the rise is small and harmless. The trouble starts when the grid voltage is already near the top of its allowed range before your system adds anything.

Why sunny afternoons are the problem

Around midday, three things happen together in many Punjab neighbourhoods:

  1. Solar output is at its peak, so export is at its highest.
  2. Other homes on the same transformer are also exporting. Every rooftop system pushes the local voltage up a little.
  3. Local load may be lower than in the evening, so less of that export is used nearby.

The result is that voltage on the low-voltage network climbs through the middle of the day. Inverters are built to disconnect when grid voltage goes outside a set window, to protect equipment and the network. When the limit is crossed, the inverter trips with a grid overvoltage alarm, waits for the voltage to settle, reconnects, exports again, and the cycle repeats.

What the grid voltage should be

The nominal low-voltage supply in Pakistan is 230 V single-phase and 400 V three-phase. NEPRA's 2024 draft distribution performance standards required DISCOs to keep voltage variation within ±5% of nominal at the point of supply under normal conditions, which for a 230 V supply is roughly 218 V to 241 V.

Your inverter's trip limits are set by the grid standard selected during commissioning and can differ by model and setting. If the grid at your meter regularly sits near or above the upper end of the range before your system exports, voltage rise from solar can push it over.

Signs that voltage rise is the cause

Grid faults during load-shedding are a different issue, explained in inverter shows grid fault during load-shedding and anti-islanding. For other alarm types, see our solar inverter faults guide.

Safe owner checks

  1. Record the alarm text and time. Photograph the inverter screen.
  2. Check the alarm history in the app. Note the voltage reading at the time of the trip if the app shows it.
  3. Look at the pattern. Note whether trips happen on sunny days, at midday and on low-load days.
  4. Compare with a high-load day. If trips are fewer when the house is using more power at midday, export-driven rise is likely.
  5. Ask neighbours on the same transformer whether their inverters trip.
  6. Share the evidence with your installer: screenshots, times and photos.

You will lose some generation each time the inverter trips, so this problem also appears as lower solar production than expected.

What an engineer can do

Measure the grid voltage properly

The first step is to find out whether the grid is high on its own. An electrician measures voltage at the main board with solar switched off around midday, and ideally logs it over a day. If the grid alone is above the allowed range, the evidence goes to your DISCO, because the fix may be on the network side, such as a transformer setting.

Check the AC cable and connections

If the grid is acceptable but the voltage at the inverter climbs too much when exporting, the cable from the inverter to the connection point may be too long or too thin, or a joint may be loose. Upgrading the AC cable, shortening the run or remaking connections reduces the rise. Our solar cable size guide explains why size matters.

Balance the phases

On a three-phase connection with single-phase inverters, putting all the solar on one phase raises that phase much more than the others. Spreading capacity evenly across phases, or using a three-phase inverter, reduces the rise on any one phase. See three-phase vs single-phase solar inverters and converting from single-phase to three-phase.

Use the inverter's voltage response settings

Many modern inverters can reduce output gradually as voltage rises (often called volt-watt), or adjust reactive power (volt-var), instead of tripping outright. Whether these modes are available and allowed depends on the inverter and the grid standard. An engineer sets them; owners should not.

Use more solar on site, or limit export

Every unit used on site is a unit that does not raise the voltage by being exported. Running pumps, washing machines and other flexible loads at midday helps. Our solar load management guide has practical ideas. Where export is not needed or not approved, an export limit removes the cause; see our zero export device guide. Under net billing, self-use is usually worth more than export anyway, as explained in our net metering and net billing guide.

Voltage protector or voltage rise?

A voltage protector on the house incomer protects appliances from bad grid voltage. It does not stop voltage rise from your inverter, and if set too tight it can trip on normal export. The two need to be designed together. See do you need a voltage protector with solar? and our breakers and protection page.

How Solar Works handles voltage-rise trips

We size AC cables, choose single-phase or three-phase inverters and set grid protection as part of in-house design, and we check voltage behaviour during commissioning. For systems we install, our own engineering staff handle after-sales complaints. Once a complaint is registered, we target sending service personnel within 48 hours to begin diagnosis; if the cause is on the network side, resolution depends on the DISCO. See our solar installation services.

We can also inspect and diagnose systems installed by other companies, as a chargeable service, across Punjab.

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Inverter tripping every sunny afternoon? Send us screenshots of the alarm history and the daily generation curve.

We serve customers throughout Punjab. See our Faisalabad and Lahore pages, or contact us.

Frequently asked questions

Why does my solar inverter trip only on sunny afternoons?

That is when your system and your neighbours' systems export the most, which pushes local grid voltage up. If the grid is already high, the extra rise crosses the inverter's limit and it disconnects to protect itself and the network.

Is grid overvoltage a fault in my inverter?

Usually not. The inverter is doing its job by disconnecting. The cause is normally high grid voltage, cable resistance, phase imbalance or settings, which an engineer should check.

Can I raise the inverter's voltage limit myself?

No. Grid-protection limits are safety settings tied to the grid standard for your connection. Changing them without authority can be unsafe and may breach your DISCO's interconnection requirements.

Will a thicker AC cable fix voltage rise?

It can, if the cable is the main cause. A larger or shorter cable reduces resistance and therefore the rise. If the grid is already too high without solar, the DISCO side also needs attention.

Does a three-phase inverter help with voltage rise?

On a three-phase connection, yes, because it spreads export across all three phases instead of loading one. Balancing single-phase inverters across phases has a similar effect.

Should I complain to my DISCO?

If an electrician measures grid voltage above the allowed range with your solar switched off, yes. Share the readings, dates and times in writing with your DISCO sub-division and keep a copy.

Sources

  1. NEPRA, Draft Performance Standards (Distribution) Regulations, 2024 (voltage variation within ±5% of nominal, 400/230 V class)
  2. Solis, documentation on grid overvoltage (OV-G-V) alarms, causes and solutions
  3. SolarQuotes, explanation of voltage rise and inverter trips (Australian context, used for the general mechanism only)

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