One new area of possible development within international standards is to integrate requirements for energy efficiency into IEC 60364 (the international standard that the wiring regulations (BS 7671) are based on). In this second article we take a closer look at energy efficiency of low-voltage electrical installations.
In order to make improvements we need to be able to measure the amount of electrical energy consumed and monitor and control energy effectively.
Energy measurement is essential for energy management. Therefore, the design of the electrical distribution system needs to be carried out in such a way that will allow the metering and control of the various electrical loads in an installation.
A further key point when designing a new installation includes determination of the most energy-efficient location of the transformers and switchboards in an installation in order to reduce the electrical losses within the electrical distribution system.
The objective is to locate the transformer and switchboard at the centre of the group of loads they are feeding. Also, in order to have an energy efficient installation, losses in equipment need to be as low as possible.
Maintenance is also important. For example, a lighting installation should be maintained to keep its visual performance within the design limits. The lighting designer will have selected a certain illumination level for the particular activity and presumed a frequency of lamp replacement and a frequency of cleaning.
Measurement and control
It is understood that there is no obligation on an electricity supplier to provide any other metering than that required to obtain the basic data to enable tariff charges to be applied.
While this may be adequate for the smaller installation, it does not give sufficient information to allow a larger consumer to allocate costs to various facilities or to control consumption.
Therefore, to be able to measure the amount of electrical energy consumed and monitor and control energy effectively metering equipment needs to be allowed for at the planning stage. Although this will increase the initial cost of the switchboards, it will prove more economical than having to add metering at a later date.
How metering information will be used needs careful consideration. The system may be required to measure power quality, voltage levels and loads. It may also produce alarms, control loads or change tariffs if preset limits are exceeded.
Consideration should be given to the environment where the meter is installed which should be in accordance with the manufacturer’s instructions. Metering needs to be installed in an area that is accessible for the meter reader and where the display can easily be read.
Areas where the instrument is likely to be subjected to excessive heat, moisture, and vibration should be avoided. Meters are available that provide pulse generation. These can be linked to building management systems to provide an electrical pulse proportional to a unit of measurement.
To view the full article from the IET's Wiring Matters Summer 2012, download the attachment at the end of this article.
View the full Summer 2012 Issue of Wiring Matters by visiting the IET website here.
Summer 2012 Issue of Wiring Matters Features:
Energy efficiency
Lifts for Firefighters
In-service Inspection and Testing Code of Practice changes
Unlawful killing
Protective Equipotential Bonding