Blinding power is energy that flows through your cables and transformers but is not converted into useful work such as running motors or light. A poor ratio between this reactive power and actual power is called a low Power Factor (or Cos Phi).
This seems like a theoretical concept, but the consequences are concrete: unnecessarily high energy bills due to fines from the grid operator, overloaded cables and transformers, and unexplained trips of protection devices. By reducing reactive power, you instantly create extra capacity on your existing connection and increase operational reliability. In this article, we explain how it works, how to measure it and what you can do about it.
What is it? Blinding power (kVAr) is 'shuttling' energy required to build up magnetic fields (e.g. in motors), but which does not perform any work.
The problem: Excess reactive power puts extra strain on your installation and often leads to penalties on energy bills (bad Cos Phi).
The solution: reactive current compensation (such as capacitor banks or active filters) can solve this locally.
The risk: Compensating reactive power without taking harmonic contamination into account can lead to resonance and dangerous situations.
The result: After optimisation, current drops, penalties disappear and power space is freed up on the transformer.
This article is specifically written for professionals responsible for the continuity and safety of critical electrical installations:
To understand reactive power, the beer analogy is often used. Imagine a glass of beer.
Liquid beer (kW - Actual Power): This is the part you pay for and what you actually 'use'. In electrical engineering, this is the energy that makes a motor run or a lamp light up.
The foam (kVAr - Blind Power): This is in the glass and takes up space, but you don't drink it. In your installation, this is the energy needed to make magnetic fields (in transformers and motors). It shuttles back and forth between source and consumer.
Total capacity (kVA - Apparent Power): This is the sum (vector) of beer and foam. Your transformer and cables should be large enough for the total glass, i.e. including the foam.
The Power Factor The ratio of actual power (kW) to apparent power (kVA) is called the Power Factor.
Nuance: In practice, Cos Phi is often referred to. In a pure sinusoidal network, the Power Factor is equal to the Cos Phi. However, in modern installations with a lot of contamination (harmonics) this differs. More on this later.
Ignoring reactive power has a direct impact on costs and continuity.
1. Financial penalties Grid operators charge their network on the basis of kVA (power factor). If your Power Factor is low, the grid operator transports a lot of 'useless' power. If your cosine phi falls below a certain value (often 0.85 or 0.9, depending on your contract), you pay a blind current penalty. This can amount to thousands of euros per month.
2. Capacity issues (The 'hidden' space) Suppose you have a 1000 kVA transformer. With a Power Factor of 0.7, you can only connect 700 kW of machines. If you improve the Power Factor to 0.95, you can suddenly connect 950 kW to the same transformer. Blind current compensation is often cheaper than installing a heavier transformer.
3. Energy losses and heat Blind current physically flows through your cables. Each ampere causes heat (I²R losses). Unnecessary reactive current therefore causes hotter cables, additional energy losses and faster component ageing.
4. Voltage dips High reactive current demand can lead to larger voltage drops across your cabling, compromising the stability of sensitive equipment.
You don't need to be a specialist to recognise the first signs. Be alert to:
Not every reactive power is the same. We distinguish between two types, which counteract each other (and can therefore cancel each other out).
Inductive Blind Power (Most common) Occurs in devices that use coils to create a magnetic field. Here, the current lags behind the voltage.
Capacitive Blind Power This involves current running ahead of voltage. This used to be rare, but today we see it more often.
Distortion Blinding power
Power factor optimisation is called Cos Phi improvement or reactive current compensation. The approach depends on the dynamics of your load.
1. Static Capacitor Banks (Conventional) Large capacitors are added in steps to compensate for inductive reactive power.
2. Static Var Generators (SVG) Modern, power electronics-based systems. They respond steplessly and at lightning speed (within milliseconds).
3. Active Harmonic Filters (AHF) This is the most advanced solution. An AHF can simultaneously reduce harmonics, eliminate imbalance and compensate for reactive power.
HyTEPS advice: Never simply install a capacitor bank in a modern installation. If harmonic contamination is present (caused by inverters/drives), the capacitor bank forms a vibration circuit with the transformer. This leads to resonance, which can cause fire or explosion of the capacitors. Measuring is knowing.
Blind sailing on the energy meter: the power company's meter gives an average. Short spikes in reactive current you do not see, but do put a strain on your installation.
Confusion between Cos Phi and Power Factor: Cos Phi only looks at the 50Hz keynote. 'True Power Factor' also takes pollution (harmonics) into account. So a good Cos Phi does not automatically mean an efficient installation!
Installing capacitors in dirty grids: as mentioned above, this is asking for resonance problems.
Overcompensation: Overcharging capacitors leads to a capacitive grid, which can cause dangerous overvoltages during off hours (e.g. weekends).
Forgetting maintenance: Capacitors age and lose capacity. A bank installed 10 years ago may now be delivering only 60% of its power.
Check your bill: Are you paying for reactive current or kVArh?
Inventory your load: do you have a lot of motors that start direct-on-line (inductive) or, on the contrary, a lot of modern electronics/LED (harmonics)?
Measurement: Have a Power Quality measurement (or quick scan) carried out. Ask specifically about the load in kVA versus kW and the presence of harmonics (THDu/THDi).
Simulation: For complex installations, we simulate what the effect of compensation will be, to exclude resonance.
Selection: choose conventional banks (if safe), SVG or Active Filters.
Verification: After installation, measure whether the Power Factor has actually improved and remains stable under varying loads.
Not every blind current problem requires our intervention. A simple motor running the same 24/7 can be compensated just fine by your in-house installer. Engage HyTEPS when:
In doubt about the efficiency of your installation or paying penalties to the grid operator? Speak to an engineer from HyTEPS. We will analyse your situation (from billing to metering) and come up with a substantiated plan to safely optimise your Power Factor.
HyTEPS
Beemdstraat 3
5653 MA Eindhoven
