108 Chapter 7 • Measuring instruments Te monthly tariffs include;


1. the price for kWh used, and 2. a price based on maximum demand.


Te supply authorities encourage consumers to spread the load more evenly by making use of this reward versus penalty method (paying according to maximum demand).


7.6.4 Load management


Large industrial consumers can shed some of their heavy load equipment during peak periods and make use of them during off peak periods. For example, furnaces and other high energy equipment can be used during nightshiſts when electricity is considerably cheaper. When a gold mine exceeds its maximum demand, it will stop hoisting the heavy rocks and switch to lighter loads such as moving equipment and supplies.


(a) Maximum demand monitors


Maximum demand monitors are used for monitoring the load consumption of industrial consumers, to prevent the power demand from exceeding limits laid down by the maximum tariffs, which would result in additional high costs. Te monitor switches off parts of the plant which can be spared for a short time.


(b) Time switches


Time switches is another method which can be used to switch off certain non- essential loads at certain times. Tey work on very much the same principle as the timer that controls a school bell. Te time switches can be programmed in advance according to time as well as days, e.g. Saturdays, Sundays and public holidays and according to seasons (e.g. winter and summer).


(c) Power factor control


Another method of keeping within maximum demand limits, is to keep the power factor of the installation as close to unity as possible.


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