Grid Overvoltage Tripping in Pakistan: Why Your Solar Inverter Shuts Down at Noon and How to Fix It

8/30/2026

You step outside at 1:00 PM on a scorching afternoon. The sun is blazing, your roof is soaked in solar radiation, and your solar panels should be generating peak power. Yet, when you check your inverter app or digital display, you see a red warning light or a zero-watt output reading accompanied by an error code: "Grid Voltage Out of Range" or "AC Voltage High."

This issue—known as grid overvoltage tripping—has become one of the most widespread headaches for solar system owners across Pakistan. Ironically, the problem occurs precisely when solar generation conditions are at their absolute best.

If your inverter turns off or repeatedly restarts between 11:00 AM and 3:00 PM, your system isn't necessarily faulty. Here is a clear breakdown of why grid overvoltage happens in Pakistani residential and commercial areas, and the exact steps you can take to fix it.

Why Does Your Inverter Trip When the Sun is Brightest?

To export electricity back into the grid via net metering, your solar inverter must push current upstream through your service cables and into the local distribution transformer. For current to flow out from your property to the street grid, the inverter must generate an AC voltage slightly *higher* than the incoming grid voltage.

For example, if your local electric supply company (such as LESCO, MEPCO, or IESCO) is supplying 235V at your main breaker, your inverter might push output at 240V to export energy.

However, two major factors cause this voltage to dangerously spike during peak afternoon hours:

  1. Localized Neighborhood Solar Saturation: In many urban areas across Lahore, Islamabad, Multan, and Karachi, dozens of properties on the same feeder line now have solar installations. At midday, all these inverters simultaneously push power back into the same neighborhood transformer. This collective power feed raises the voltage of the local grid—sometimes pushing line voltage up from a normal 220V–230V to 255V or higher.
  2. Undersized AC Cabling: If the copper cable connecting your inverter to your main Distribution Board (DB)—or from your DB to the utility net meter—is too thin or too long, it creates high electrical resistance. When your inverter attempts to output full current, this resistance causes a steep voltage rise along the line. Your utility line at the street might be 240V, but the voltage right at the inverter terminals hits 255V due to cable loss.

The Safety Limit: Understanding the Cutoff Thresholds

According to NEPRA regulations and standard inverter safety certifications (such as IEC 61727), grid-tied and hybrid inverters are programmed to shut down automatically if grid voltage exceeds safe operating parameters.

Most inverters operating on the Pakistani grid use two primary protection thresholds:

Once the inverter disconnects, its export current stops, the local voltage drops back to normal, and the inverter undergoes a 60-second countdown before reconnecting—only to trip again minutes later when output ramps back up.

4 Solutions to Fix Inverter Overvoltage Tripping

If you are losing valuable generation units during peak sunlight hours, follow this systematic troubleshooting process:

#### 1. Measure Cable Voltage Drop and Upgrade AC Wiring Before assuming the local grid is at fault, test your internal wiring resistance. During peak solar generation, measure the AC voltage directly at your main utility meter, and simultaneously measure the AC voltage at your inverter terminals.

If the voltage difference between the two points is greater than 2 to 3 Volts, your AC cabling is under-specified. Upgrading your AC wire size (for example, moving from a 10mm² cable to a 16mm² or 25mm² pure copper cable on a 10kW or 15kW system) lowers resistance, effectively dropping the terminal voltage at the inverter into the safe zone.

#### 2. Enable Volt-Watt Control Mode Modern tier-1 inverters (including Solis, Huawei, Growatt, Nitrox, and Deye) feature a smart grid function called Volt-Watt Response.

When configured by your installer, the inverter will not abruptly trip off when line voltage reaches 252V. Instead, it dynamically throttles back its power output by a small percentage (e.g., reducing generation from 100% to 88%). This slight reduction in current lowers the voltage spike, allowing the inverter to stay online and continuously export power rather than shutting down completely to 0 kW.

#### 3. Rebalance Phases on 3-Phase Systems On 3-phase net-metered connections, utility grid voltage is frequently unbalanced across the three lines. Phase A might sit at an elevated 256V while Phase B and Phase C sit at a stable 232V. Because 3-phase inverters export current across all three phases equally, the highest single phase will trigger an all-phase safety shutdown.

Have your installer measure all three phases under load. If one phase is disproportionately high, contact your local DISCO line staff to request a phase swap at the pole to connect your system to a less congested line.

#### 4. Request a DISCO Transformer Tap Adjustment If your baseline voltage is sitting at 250V+ early in the morning when no solar is generating, the local distribution transformer's tap setting is set unnecessarily high.

You can submit a formal written application to your local DISCO Sub-Divisional Officer (SDO). Requesting a transformer tap adjustment lowers the transformer's baseline output by 5V to 10V, providing sufficient voltage headroom for all solar systems on the street to export power smoothly.

Final Thoughts

Unnecessary inverter tripping quietly erodes your return on investment by discarding your highest-yielding generation hours of the day. At ApnaSolar, every installation undergoes strict AC voltage-drop modeling to prevent cable-induced trips before they happen. If your current system is constantly disconnecting at midday, perform a voltage audit or reach out to our engineering team to help you stabilize your system.