In an ideal electrical installation, the three phases are perfectly balanced: the voltages are equal in amplitude and the phase angles are exactly 120 degrees to each other. Practice, however, is unruly. Voltage imbalance (or voltage asymmetry) is a common Power Quality phenomenon that often goes unnoticed until components fail.
Especially in industrial environments and data centres, imbalance causes unexplained wear and tear. A small voltage imbalance can lead to a disproportionate power imbalance in running machines, resulting in overheating and efficiency loss. Where engineers often first think of mechanical faults or overloading, the cause regularly lies in voltage quality. HyTEPS analyses the source of the imbalance and advises on the right mitigating measures to ensure your operational reliability.
What is it: A situation in a three-phase grid where the phase voltages are unequal in magnitude and/or the phase angle deviates from 120 degrees.
The risk: Motors and transformers should no longer be fully loaded (derating) to prevent overheating and damage. In addition, high currents arise in the neutral conductor.
The cause: usually an uneven distribution of single-phase loads (such as lighting or IT equipment) or faults in the feeding network.
The solution: load redistribution, deployment of Active Harmonic Filters for load balancing, or consultation with the grid operator in case of external causes.
This information is crucial for professionals responsible for the continuity and safety of heavy electrical installations:
Technically defined, we speak of voltage imbalance when in a three-phase system the RMS values of the phase voltages (L1, L2, L3) are not equal to each other, or when the phase shifts between the phases deviate from the ideal 120 degrees.
A comparison: Imagine three horses pulling a heavy cart (the load) together. If all three horses are equally strong and run in the same rhythm, the cart goes straight ahead and the power is distributed efficiently. If one horse is weaker or pulling in a different direction (imbalance), the other two horses have to work harder and the cart starts swaying (vibrations). Energy is lost to friction and correction instead of progress.
Engineering background (Symmetrical components): For engineers, the theory of symmetrical components (Fortescue) is relevant. Imbalance introduces a 'negative sequence' component into the voltage field. In an electric motor, this negative sequence generates an opposing torque. The motor tries to turn forward and backward at the same time, as it were. This does not result in motion, but purely in heat.
Standardisation: According to standard EN 50160, the voltage imbalance in public low-voltage networks may not exceed 2% (measured over 10 minutes, 95% of the week). In industrial environments (IEC 61000-2-4), stricter requirements may apply for Class 1 equipment.
Voltage imbalance is often underestimated because the installation usually keeps running. However, efficiency and safety decrease drastically. The consequences can be divided into three categories:
This is the most critical consequence. A small voltage imbalance of just 2% can lead to a current imbalance of as much as 15% to 20% in the windings of an asynchronous motor.
In a perfectly balanced grid, the vectorial sum of currents is zero; no current flows through the neutral conductor. In case of imbalance (caused by uneven load), an equalising current passes through the neutral.
Equipment such as variable frequency drives (VFDs) and inverters have rectifier bridges at the input. With voltage unbalance, the diodes are loaded unevenly. One phase may have to supply most of the current, overloading these diodes and causing the drive to fail or break down.
The symptoms are often subtle until it is too late. Be alert to:
The cause may be external (grid operator) or internal (your own installation).
Solving imbalance always starts with insight. Blindly replacing components makes no sense.
Only measure average current: Many panel meters show an average. At 100A, 100A and 160A, the average of 120A may seem acceptable, but phase 3 is heavily overloaded. Always look at the values per phase.
Confusion with harmonics: Zero current is often directly attributed to harmonic contamination (3rd harmonic). However, imbalance is an equally, if not greater, cause of zero currents. A Power Quality analysis makes the distinction.
Ignoring derating: Running a motor 'on the edge' while there is imbalance is asking for trouble. The NEMA derating curve should be strictly followed.
Looking for cause outside the door: "It's down to the grid operator." This is often incorrect. Although the incoming voltage has an influence, the majority of imbalance problems are caused by the internal distribution of the installation.
Confuse voltage vs current: A small voltage imbalance (source) causes a large current imbalance (load). Don't just focus on the voltage; the current imbalance is what does the damage.
Want to know if your installation is at risk? Follow these steps:
In complex situations, simply "switching groups" is not possible or sufficient. Engage HyTEPS' engineers when:
Symptoms are often subtle until things go wrong. Look out for unexplained machine failures, flickering lights, cables getting hot or transformers buzzing. Also, if electronics (PLCs, drivers) fail earlier than the service life indicates, chances are that the power quality is insufficient. A Power Quality measurement provides the answer.
This is possible, provided you have a high-quality Power Quality Analyzer (according to IEC 61000-4-30 Class A) and the knowledge to interpret the data. Collecting data is easy; analysing the correlation between events, harmonics and your specific business processes requires specialist engineering knowledge. We are happy to support you in the analysis.
Not by definition. NEN-EN 50160 describes the minimum requirements for voltage at the grid operator's transfer point. However, modern equipment can be more sensitive and malfunction even if the voltage is within this standard. We therefore look beyond the standard: we look at the compatibility between your power supply and your connected load.
Peace of mind, certainty and insight. You get a clear diagnosis of the 'health' of your electrical installation. We pinpoint the cause of faults, enabling you to avoid unplanned downtime and reduce fire risks or unnecessary energy losses. You receive a concrete advisory report with practical points for improvement.
No, that is a misconception. A filter is a powerful tool, but not a panacea. Sometimes the solution lies in changing transformer settings, redistributing loads or adjusting cabling. HyTEPS always recommends a thorough analysis and simulation before we recommend hardware, to avoid unnecessary investments.
Yes, significantly. Solar panel inverters and LED lighting drivers are non-linear loads that cause harmonics and sometimes supraharmonics. This can lead to interference with other equipment or overloading of the neutral conductor. When renovating or preserving, a Power Quality check is essential to ensure operational reliability.
We call this phenomenon 'nuisance tripping'. Often the cause is not the total amount of current, but the distortion of the current (harmonics) or short peak currents that your measuring equipment misses. This contamination can extra heat up thermal protections or confuse electronic protections, causing them to switch off wrongly. A specialised measurement can find out exactly why a protection reacts.
For a reliable picture, we usually measure at least one to two weeks. This is necessary to capture a full duty cycle, including weekends and peak loads. For specific acute failures, we can also take short-term measurements or deploy 'continuous waveform recording' to capture transients.
Your installer is an expert in installation and maintenance (the 'general practitioner'). HyTEPS is the specialist (the 'Power Quality Doctor'). We have advanced measuring equipment, simulation software and in-depth knowledge of theoretical electrical engineering and regulations. We often work together with installers to solve complex puzzles that fall outside standard knowledge.
After the measurement, you receive a report with conclusions in understandable language as well as technical details. If necessary, we simulate the possible solutions in our software. So you know exactly what the effect of a measure will be in advance. We then supervise the implementation and verify the result with a follow-up measurement.
Don't wait for components to fail. Speak to an engineer from HyTEPS to discuss your situation or request a Power Quality survey. We will give you insight into the exact state of your installation and offer a solution with guaranteed results.
HyTEPS
Beemdstraat 3
5653 MA Eindhoven
