How does the LVRSys® low voltage regulation system mitigate PV-related voltage rise?

LVRSys® regulates voltage locally in the affected feeder, reducing PV-related voltage rise and keeping limits according to EN 50160. This allows inverters to operate without curtailment while maintaining power quality for connected customers.

When is LVRSys® preferable to an on-load tap changer (OLTC)?

LVRSys® is particularly effective in asymmetric low-voltage networks with one PV-dominated feeder. An OLTC regulates centrally at the transformer, whereas LVRSys® acts directly in the critical feeder and therefore addresses local overvoltage more precisely.

Can LVRSys® avoid or postpone grid reinforcement?

In many cases LVRSys® allows DSOs to solve voltage rise issues without immediate civil works. By stabilising the voltage in the problematic feeder, cable reinforcement or additional transformer stations can often be postponed or avoided.

Does the LVRSys® system require excavation work?

No. LVRSys® is usually installed in existing cabinets using a compact two-cabinet layout. This minimizes construction work, avoids excavation and reduces project duration compared with classic reinforcement measures.

What regulation range does LVRSys® provide in low-voltage networks?

In the described application LVRSys® offers a ± 10 % regulation range at 144 kVA feeder power. This range is suitable for typical PV and load scenarios in European low-voltage distribution networks.

Which operators benefit most from LVRSys®?

LVRSys® is designed for DSOs, municipal utilities and industrial grid operators who face PV-related voltage rise in low-voltage networks and need a fast, technically robust and cost-efficient alternative to traditional grid reinforcement.

LVRSys® Voltage Regulation in Low-Voltage Networks - Solving Pv-Related Overvoltage Issues

The LVRSys® low voltage regulation system ensures reliable voltage control in low-voltage networks with high photovoltaic penetration. Increasing PV generation often leads to voltage rise and curtailment according to EN 50160. LVRSys® low voltage regulation system provides decentralized regulation directly in the affected feeder, offering a fast, efficient and excavation-free alternative to grid reinforcement.

Key Takeaways

Real-world example from Kärnten Netz GmbH: significant voltage rise caused by high PV feed-in.
KNG deliberately chose LVRSys® instead of grid reinforcement.
A. Eberle and KNG jointly developed a compact two-cabinet LVRSys® solution for existing networks.
LVRSys® regulates voltage locally in the affected feeder, ideal for asymmetric grid conditions.
PV systems were able to inject power again in compliance with EN 50160.
No excavation, no costly reinforcement measures - immediate stabilization

Short Introduction

Within the regional energy transition, Kärnten Netz GmbH experienced substantial growth in private PV installations. In one low-voltage network, the resulting feed-in caused notable voltage rise. Instead of investing in cable reinforcement or additional transformer stations, KNG sought a fast and economical solution. Together with A. Eberle, the LVRSys® low-voltage regulation system was implemented - using a specially developed, space-saving two-cabinet design perfectly suited for the existing environment.

Applications and Use Cases

The rapid expansion of private PV systems creates new feed-in situations in many low-voltage networks. Combined PV generation can locally exceed the allowable voltage limit of +10 % according to EN 50160, causing inverters to reduce or stop generation..

Private households with rooftop PV systems – increasing photovoltaic feed-in in low-voltage networks. — Figure 1: Rapid increase of private rooftop PV installations (Photo: Kelag).

LVRSys® Low Voltage Regulation System in Pv-Dominated LV Networks

High simultaneous feed-in leads to voltage rise, especially at the end of the feeder. LVRSys® enables localized voltage regulation without influencing the distribution transformer.v

Network topology with a PV-dominated feeder in the Kärnten Netz GmbH low-voltage grid. — Figure 2: Network topology showing a PV-dominated feeder (KNG).

In the examined network, the transformer supplies three feeders. The upper feeder was clearly feed-in dominated, while the other two mainly carried load. A central on-load tap changer (OLTC) would not have been sufficient to solve this asymmetric situation.

KNG identified:

1 feeder → strongly feed-in dominated
2 feeders → predominantly load-dominated

A central OLTC would not have been able to address this local issue effectively.

Space Constraints or Ownership Restrictions

Conventional reinforcement - e.g., installing 350 m of additional cable - would require permits, construction, and high costs. Due to ownership restrictions, enlarging the existing cabinet was not possible. The compact LVRSys® two-cabinet solution, however, fit seamlessly into the location.

Functions and Advantages of LVRSys® in Low-Voltage Networks

Decentralized voltage control directly in the affected feeder
±10 % regulation range, suitable for PV and load situations
Fully compliant with EN 50160
No civil engineering or major structural modifications
Maintenance-free and immediately operational
Modular two-cabinet setup for confined locations
Proven in field operation (e.g. at KNG)

In contrast to an OLTC, LVRSys® regulates exactly where the voltage becomes unstable — at the network periphery.

Practical Implementation

Figure 3: Voltage profile before and after commissioning LVRSys® (example data).

Measurements clearly showed that only one feeder exceeded the voltage limit regularly. LVRSys® regulated this feeder precisely - without affecting the others unnecessarily.

Measurement and Network Assessment

Detailed voltage recordings enabled the identification of the critical feeder.

Decision for LVRSys® Instead of Grid Reinforcement

Cable reinforcement or additional transformer stations would have been costly and slow, especially with uncertain PV expansion.

Outdoor LVRSys® two-cabinet solution installed at a Kärnten Netz GmbH distribution point. — Figure 4a: Compact LVRSys® two-cabinet outdoor solution at a KNG network site.

Internal layout of the LVRSys® two-cabinet design showing separate control and distribution sections. — Figure 4b: Internal LVRSys® layout with separated control and distribution cabinets.

The two-cabinet design was jointly developed by A. Eberle and KNG to separate regulation and distribution. This makes the system extremely space-efficient, flexible, and ideal for retrofit environments.

Results and KPI Impact

LVRSys® provides:

Scalable performance for future PV growth
Stable voltage in the feed-in dominated feeder
Full PV injection without curtailment
Improved voltage quality under load
No excavation required

LVRSys® low-voltage regulation system in an open street cabinet for voltage control in low-voltage distribution networks — Figure 5: Interior view of the LVRSys® low-voltage regulation system installed in a street cabinet for stable voltage control in low-voltage distribution networks.

Conclusion from Practice

“For Kärnten Netz GmbH, the low voltage regulation system LVRSys® is the optimal solution to specifically address voltage issues in the local distribution network. It improves voltage quality exactly where instabilities occur and resolves bottlenecks quickly and reliably. Compared to a regulated distribution transformer or extensive grid reinforcement, LVRSys® operates directly in the affected network section, without costly civil works and without long project lead times. This allows grid expansion to be avoided or postponed into the future.”

~ Michael Pink, Grid Planning Electricity, KNG Kärnten Netz GmbH

FAQ

How does LVRSys® compare to an OLTC?

An OLTC regulates centrally at the transformer, while LVRSys® regulates locally in the critical feeder, which is essential in asymmetric grid situations.

Can LVRSys® reduce or eliminate PV curtailment?

Yes. By actively lowering voltage in the affected feeder, PV systems can operate within their designed power range again.

Does LVRSys® require excavation work?

The installation of the LVRSys® low-voltage regulation system is carried out in the same way as the installation of a street distribution cabinet using a concrete base. Civil engineering works, for example in the roadway, are not required, as the system is simply connected to the existing grid connection point.

What is the regulation range of LVRSys®?

The system can be adapted to the specific application. In this case, a ±10% regulation range was selected, which is ideally suited to solving voltage issues caused by photovoltaic feed-in and load situations in low-voltage distribution networks.

Who benefits from LVRSys®?

DSOs, municipal utilities, industrial networks, and any operator facing PV-related voltage rise.

Autoren

Thomas Schwarz - Product Manager Low-Voltage Regulation LVRSys® (A. Eberle GmbH & Co. KG)
Josip Greiner - Control Engineering (KNG-Kärnten Netz GmbH)
Michael Pink - Grid Planning (KNG-Kärnten Netz GmbH)