G99 Voltage Rise/Drop Quick Estimator – Free Grid Connection Tool

Understanding Voltage Rise and Drop in Distributed Generation

When connecting distributed generation to the electricity network, one of the key considerations is the potential impact on local voltage levels. Voltage rise or drop can occur due to the impedance of the connection cable and the power injected by the generator. This quick estimator tool helps developers assess whether their project is likely to face voltage issues, based on a simplified calculation.

What Causes Voltage Rise and Drop?

Voltage rise or drop is primarily influenced by three factors:

1. Generator Size: The larger the generator’s output (in kVA), the greater the potential for voltage change.
2. Cable Length: Longer connection cables have higher impedance, leading to more significant voltage changes.
3. Voltage Level: The impact of a given generator and cable setup will vary depending on the voltage level (e.g., LV, 11 kV, 33 kV).

When a generator exports power, it can cause a local voltage rise at the point of connection. Conversely, when a large load is connected, it can cause a voltage drop. The challenge is to keep these voltage changes within acceptable limits, typically ±3% of the nominal voltage.

Using the Voltage Rise/Drop Quick Estimator

To use the estimator, simply enter your generator size (in kVA), the length of the connection cable (in meters), and select the appropriate voltage level. Click “Calculate” to see the estimated voltage change as a percentage of the nominal voltage.

The tool will also provide a preliminary compliance assessment, indicating whether the voltage change is within typical limits (±3%) or if further studies are recommended.

Limitations and Disclaimer

It’s important to note that this tool provides a simplified estimation based on assumed cable impedance values. In reality, voltage changes depend on various factors, including:

• The specific cable type and configuration
• The existing network conditions and background voltage levels
• The presence of other generators or loads in the area
• The operation of voltage control devices (e.g., on-load tap changers, voltage regulators)

As such, this tool should be used for initial screening purposes only. It does not replace the need for detailed voltage rise/drop studies, which consider the specific characteristics of your project and the local network.

Always consult with your Distribution Network Operator (DNO) and a qualified electrical engineer to conduct a comprehensive assessment of voltage compliance. They will use advanced power system modeling software to analyze your project’s impact and recommend any necessary mitigation measures (e.g., cable sizing, reactive power compensation).

Next Steps

If the Voltage Rise/Drop Quick Estimator indicates potential issues, don’t worry – there are solutions available. Work with your DNO and a power systems expert to explore options such as:

• Increasing the cable size to reduce impedance
• Installing voltage control devices (e.g., step voltage regulators)
• Implementing active power curtailment or reactive power compensation
• Connecting at a higher voltage level

By identifying voltage challenges early and collaborating with industry professionals, you can ensure a smooth and compliant connection process for your distributed generation project.