Summation meters are other special categories of meters that are used for recording the total consumption of a consumer fed at more than one point. The major purpose for connecting a summation meter is to facilitate the correct recording of the Simultaneous Maximum Demand, because adding up of the MDs recorded through the individual meters, arithmetically might not be correct since of the possible diversity in their periods, even by the total unit consumption could be worked out arithmetically. There are a number of techniques for summing up the consumptions through one meter, some of that are as indicated below:
- Paralleling of the CT leads on the secondary side before linking them to the meter current coil.
- Providing for every phase, one intermediate CT, known as summation CT, along with a number of primary windings for connections to the secondaries of individual CTs and only one secondary winding to feed the meter current coil.
- Use of multiple current coils in the similar meter for direct connections to the individual CTs, the measuring elements being general to all for the similar phase.
- Having independent components for all CTs mounted on a general shaft of the similar meter so in which the shaft gets the total torque and records total consumption thereby.
- Divide elements to measure the consumption independently as in the preceding technique but having separate driving shafts connected to a general one through differential gears to record the total consumption
- Divide meters, every fitted with an electrical impulse transmitting device, to record the consumption at several points independently and pass on the impulses concurrently to a common meter that then records the total consumption.