Get in Range (CLM, power correction)

15 March 2010

The harmonisation of European voltages in the 1990’s has created a wide variation in supply voltages. Paul Caddick describes why it is important for energy efficiency in building services to make some voltage checks

THERE ARE REAL FINANCIAL GAINS to be made from power correction measures applied to property services plant. It will also increase the efficiency and, therefore, both the reliability and longevity of service.
One of the main reasons for any potential problems goes back to January 1995, when the British Standard stated that the nominal voltage for the UK should be 230V to harmonise with other participating EU countries such as France, Germany and Spain. Permitting a tolerance of +10 percent to –6 percent, translates as between 216.2V to 253V - which is said to have changed nothing.
Because the other countries’ nominal supply voltages were 220V, the decision was made to meet in the middle, hence the 230V nominal voltage. However, in reality, the UK’s supply voltages are still around the old value of 240V, because this is within the permitted range.
There appears to be no official records of regional supply voltages to check out in relation to your own sites, other than the Electrical Safety, Quality & Continuity Regulations 2002 (ESQCR). CLM always begins its power analysis using individual engineers’ records and from mains reports. Voltages reaching as high as 260V are found in various locations around the UK, dependent upon the proximity of a substation.
Appendix 12 of BS 7671:2008 now has two limits for voltage drop. These limits are further subdivided, dependent on the origin of the supply whether it is a private or public supply. While lighting circuits are considered more susceptible to voltage drop and therefore attributed a limit of 3 percent, other circuits such as for heating, air conditioning, any water pumps or escalators now have a higher limit of 5 per cent. Energy efficiency technology is now, however, applied to the newest of lift designs.
Outside these ranges, neither the equipment nor indeed its effect on the installation can be guaranteed. Resistive loads would not operate efficiently when subjected to an undervoltage and consequently any resultant processes may be compromised. Overvoltages would result in a greater demand placed on the equipment and a subsequent unwanted and unnecessary increase in billing.
The reliability, safety and longevity of rotational equipment such as motors would be at risk, evident in overheating and excessive wear on bearings, commutator and brush – as well as associated damage to the installation and its wiring. Correctly designed installations would typically incur financial penalties from the effects of either under or overvoltage, but the secondary effects would be physical damage.
To check a building’s service plant, CLM engineers use the Fluke 435 three-phase power quality analyser to locate, predict, prevent and troubleshoot problems in three- and singlephase power distribution systems. Troubleshooting is faster with on-screen display of trends and captured events, even while background recording continues.
The Fluke’s menu-driven interface allows our engineers to hook up and record in minutes. It records everything on the screen automatically, monitors a quick diagnosis of system performance against user defined limits, logs multi-parameters and measures interference levels from ripple control signals at specific frequencies. These features help to quickly diagnose problems and build benchmarks for predictive maintenance.
The new IEC standards for flicker, harmonics and power quality are built in to take the guesswork out of analysis.
With a CAT III, 1000 V/CAT IV, 600V safety rating, the Fluke 435 can measure all phases, neutral and ground on virtually every connection in a low voltage electrical distribution system. The meter's measurement capabilities encompass all power system parameters including true-rms voltage and current, frequency, power, power consumption (energy), unbalance and flicker. They also automatically capture events like transients as fast as 5 microseconds and as high as 6kV, interruptions, rapid voltage changes and dips and swells.
Optimised for mobile applications, these rugged instruments operate up to seven hours on a single battery charge, so our engineers have no problem covering a large site over a day. The 16 MB data memory stores up to 50 screens. This is enough memory to record 400 parameters with one-minute resolution for up to a month, all of which can be transferred to a PC via FlukeView software for analysis or use in reports.
A detailed, user-configurable long-time recording gives the MIN, MAX and AVG readings of up to 100 parameters on all three phases with selectable averaging time down to 0.5 seconds. Using the reports, the suitable correction technology can be identified. With our experience and knowledge, CLM can recommend corrective action to eliminate inflicting any side effects elsewhere.
If the electric heating is of the convector type in which a current is passed through a resistive element that heats up, a fan is then employed to distribute the warm air via convection around the premises. Then a typical scenario would involve collation of data to include equipment specifications, design specifications and actual real time readings of the energy use.
With particular reference to the equipment, its future use should be measured against age, deterioration, reliability availability of parts accessibility and service time, to mention but a few.
The cumulative results of what can be analysed, can be amazing. A council head office monitored for a week was reported to consume 95.1kWh, which could be reduced by 20.2 percent to 75.9kWh utilising voltage optimisation and power factor correction devices. Based on average electricity prices, this translates into financial savings of nearly £3,500 over a year – and therefore full payback within two years.
● Paul Caddick is managing director of CLM