Distribution companies of electric systems must measure the voltages and currents to deliver to the customers the option of buying medium voltage energy and obtain information about the customer’s consumed energy. This is the reason why they must have a Measure Metering Outfit, to measure electric variables, voltage and current, in medium voltage, three phase and single-phase electric systems of distribution, to measure voltages and currents in distribution networks of 15 or 25 [kV]. They must also dispose of an energy meter to deliver the consumed energy values of an installation to do the billing of the consumer’s consumed energy.


Metering outfits must have current transformers and potencial transformers manufactured according to the International Norms. They must be robust and invariable to withstand high-short circuits, transitory over voltages and other possible unexpected problems in the system, protecting the associated energy meter.

In addition, they work at a high level of accuracy on measuring voltages and currents of the supplier, to minimize de error of magnitude and angle, and so they may guarantee exactitude, even when measures vary, from 10% to 110% of its nominal value.


Each Distribution company of electric supply determines, according to the internal norms, which type of metering outfit the user must connect on its network. In correlation of the normative, it will need one element-metering outfit if it is monophasic or one of two or three elements if it is three phase.

Current and Potential Transformers required are installed in a unique metallic tank, with a rucksack hang in a pole, immersed in mineral oil. The lids of these tanks dispose medium voltage insulators and a sealed box that insulated the secondary ones of the measure transformers, so the measure transformers’ secondary connections cannot intervene while the system is energized.

Accuracy is tested and certified on these electric systems, so the factors of error correction may be introduced to the energy meter to measure correctly, and after do a fair billing.