As sure as the sun rises in the east and sets in the west, a big part of an electrician’s job is being called out to fix repeated faults. However, a repeated fault in a commercial installation should be treated as a pattern before it is treated as another replacement job. Sometimes faults do re-occur, but nuisance tripping, overheating, flickering, electronic resets, premature component failure or unexplained downtime may point beyond a failed accessory or protective device. They may also point to an issue with power quality.
Let’s look at this and some more detail.
What Is A Power Quality Issue?
A power quality issue is a problem with the underlying electrical supply or installation that means the electricity delivered to equipment is not behaving as expected. This is different from a power cut. Power quality describes characteristics of the electrical supply such as voltage magnitude, frequency, waveform, voltage unbalance, fluctuations, dips, swells, transients and interruptions, and whether those characteristics are suitable for the equipment being supplied. For example, a commercial kitchen might keep reporting that their refrigeration controls reset during busy service. Replacing the controller may not solve the problem if the actual cause is a voltage dip when several high-demand appliances start at the same time.
Power Quality Issues And Solutions
Symptoms of power quality issues can be wide and varied, including voltage dips, transient voltages or surges, or voltage unbalance in a three-phase system. This can make them tricky to diagnose, as the symptoms are easy to mistake for component or appliance failures.
The solution therefore starts with the evidence, such as when the problem occurs, what equipment is operating, which circuits are affected, whether the issue follows new equipment, and whether the public supply, the installation or connected equipment needs further investigation.
So, How Do You Approach A Power Quality Issue?
First, assess the electrical infrastructure on site. Commercial sites often combine LED lighting, IT equipment, variable-speed drives, refrigeration, heating, ventilation, catering appliances, charging equipment, lifts and building management systems. Those loads behave differently. Some create high starting currents. Some introduce harmonics. Some are sensitive to voltage dips or swells, and some interact only when several systems operate at once.
A useful first assessment records:
- The time and frequency of the issue
- Whether it occurs at start-up, peak load or shutdown
- Whether affected equipment is on one distribution board or across several
- Whether protective devices operate consistently or randomly
- Whether flicker, resets, overheating or noise are reported
- Whether new loads were added before the pattern began
- Whether other tenants or areas experience the same event.
This prevents the common failure of replacing the visible failed component while leaving the underlying electrical condition unchanged.
Separate Installation Issues From Supply Quality Issues
BS EN 50160 provides the standards context for voltage characteristics of electricity supplied by public networks. It is relevant because many power quality issues and solutions sit between the installation and the supply.
Ofgem’s RIIO-2 Electricity Distribution Annual Report shows how reliability is formally measured, tracking Customer Interruptions, the number of supply interruptions per 100 customers, and Customer Minutes Lost, the duration of interruptions customers experience. The same report, published in January 2026, recorded £50.9 million in cumulative RIIO-ED2 penalties under the Interruptions Incentive Scheme after several distribution network operators missed reliability targets.
These figures show that interruption and continuity are measurable electrical performance issues in commercial installations. If a customer is losing production time, experiencing repeated resets or reporting flicker, the evidence should be gathered in a way that can support either installation-side investigation or escalation to the network operator.
Know When Standard Fault-finding Approaches Are Too Narrow
A standard repair approach may be enough where there is a clearly failed device, loose connection or overloaded circuit. It is not enough where the fault pattern suggests:
- Harmonics from nonlinear loads
- Voltage dips during motor starts or heavy load events
- Voltage fluctuation linked to network or site demand
- Poor load distribution across phases
- Neutral conductor concerns
- Thermal stress at terminations
- Equipment sensitivity to waveform distortion
- Repeated protective device operation without a clear fault
At that point, the next stage may involve data logging, thermal imaging, power quality analysis, load measurement, review of distribution arrangements or contact with the DNO. This is where electrical safety training should give you more than general hazard awareness. It should also strengthen the decision about when to stop replacing parts and start collecting wider electrical evidence. A competent diagnostic report should state what has been observed, what has been tested, what is outside the scope of the first visit, and what further investigation is required.
Find Out More
Our advanced training courses for electricians can help you sharpen your diagnostic process when commercial faults point to load behaviour, voltage quality or supply interruption. To find out more, please contact one of our training advisers today by clicking here.
