Cos Phi Compensation

Cos Phi Compensation: Optimise the power factor of your installation

The ratio of useful power to apparent power determines the efficiency of your electrical installation. A low Cos Phi (power factor) causes unnecessary energy loss, limits your available power capacity and often leads to high penalties from the grid operator. By applying Cos Phi compensation, you reduce reactive current and relieve transformers and cabling. However, in modern installations with many power electronics, a standard capacitor battery is rarely the safe solution. A thorough analysis is required to avoid resonances and defects.

For whom is reactive current compensation relevant?

This topic is critical for organisations with large consumer connections working with inductive loads.

• Technical Managers & Installation Managers: Who have to deal with heat build-up in distributors, unexplained trips of protection devices or a transformer reaching its limit.
• Facility Managers: who seek space on the current connection for expansions (e.g. charging stations or heat pumps) without investing in a heavier transformer.
• Financial Controllers: Who see a "reactive current" or "excess kVAR" item on monthly energy bills and want to eliminate this cost item.

Why is low Cos Phi a problem?

Poor power factor has direct consequences on both operational costs and the technical condition of your installation.

• Financial penalties: Grid operators charge large consumers for the transmission of reactive current if the Cos Phi drops below a certain value (often 0.85 or 0.9). These charges can amount to thousands of euros per year.
• Capacity loss: Blinding current "clogs" your cables and transformers. A 1000 kVA transformer loaded with a cos phi of 0.7 can only deliver 700 kW of useful power. Improving the cos phi to 0.95 suddenly frees up 250 kW of "free" capacity for new machines or expansions.
• Unnecessary energy losses: Although reactive power does not perform any work, it does cause power transport. This leads to I²R losses (heat) in cables and distributors. Compensation reduces these losses and lowers the carbon footprint.
• Voltage drop: A high reactive current component causes greater voltage drops across cables, which can lead to unstable processes at the end of long lines.

How to optimise Cos Phi (and the risks)

The standard solution for low Cos Phi is to install capacitor batteries. These supply the required reactive power locally, eliminating the need to transport it through the grid. However, there are different methods, depending on the quality of your voltage and current(Power Quality).

• Static capacitor batteries (Conventional) Suitable for installations with a very constant load and without harmonic contamination. This is rare in today's industry anymore.
• Automatic capacitor banks These banks switch stages on and off based on current demand.
  • Risk: In an installation with harmonic contamination (due to frequency drives, LED, etc.), the capacitor forms a resonant circuit together with the transformer. This can lead to capacitors exploding or fire in the distributor.
• Drossed capacitor batteries (Detuned) In this process, a coil (drossel) is put in series with the capacitor. This prevents resonance at specific harmonic frequencies. This is the minimum safety standard in most modern environments.
• Hybrid or Active Solutions (SVG / Active Filter) For highly dynamic loads (e.g. spot welding robots or cranes), capacitors are too slow. A Static Var Generator (SVG) or an Active Harmonic Filter can compensate steplessly and within milliseconds for reactive power, whether inductive or capacitive. This is also the best solution to reduce harmonics as well.

Common errors in reactive current compensation

• Blind installation: Buying a capacitor bank based on the energy bill, without measuring for harmonics. This is the number one cause of fire in compensation cabinets.
• Too-slow control: use of contactors with rapidly changing loads (such as lifts or welding equipment), resulting in compensation always being 'behind the times'.
• Overcompensation: Turning on too many capacitors, causing the grid to become capacitive, which can lead to dangerous voltage surges (especially at night at low load).
• Forgetting maintenance: Capacitors age and lose capacity. A bank installed 5 years ago may now be delivering only 70% of its power.
• Confusion Cos Phi vs Power Factor: In modern installations, the Power Factor (which includes harmonics) is leading, not just the Cos Phi (which only looks at 50Hz).

When do you call on HyTEPS?

Installing standard capacitor batteries is risky in modern, dirty networks. Engage HyTEPS' engineers when your situation calls for more than just a product delivery:

• For harmonic contamination: Your installation contains many variable speed drives, LED lighting or EV chargers. A standard capacitor bank here will resonate and possibly catch fire. HyTEPS calculates the exact crossover or recommends active filtering.
• In case of capacity problems: Your transformer is full and you want to expand without heavy investment in new infrastructure. We analyse how many kVA can be freed up by Power Quality optimisation.
• In case of unexplained failures: Previous compensation systems have failed, fuses jump spontaneously or controllers fail. This indicates complex interactions in the grid that need to be measured first.
• With dynamic loads: You are dealing with cranes, welding robots or lifts. Conventional (slow) compensation does not work here; HyTEPS implements real-time solutions (SVG) that respond within milliseconds.
• For guaranteed results: You want assurance that the cos phi will be penalty-free (e.g. >0.95) and that the solution complies with the grid code, substantiated by simulations and a validation measurement afterwards.