Rogowski Coils for Design of Energy Meters for Nigeria Power Market

Proper metering of electricity consumption is the optimal way for effectively recovering revenues for power supplied to the consumers by the distribution companies (DISCOs). In Nigeria, the situation is quite problematic due to inadequate metering of the consumers. As a result, huge amount of revenues due to the DISCOs are left uncollected leaving the DISCOs to resort to estimated billing system. To solve this problem, this paper proposes a locally made digital energy meter built from locally available materials in Nigeria. Specifically, this work proposes to use an inexpensive rogowski coil wound from made-in-Nigeria wire on an improvised air core material as the current sensing element to be used in the meter. Two rogowski coil samples wound from SWG 36 and SWG 25 wires having resistances of 50ohm and 1.3 Ohms respectively were subjected to repeated experimental tests in order to study their characteristic behavior under varying load current scenarios. The results obtained were used to characterize the coils behaviors by using the basic fitting tool in MATLAB graphing window to generate the optimal equation representing the coils’ behaviors. The equations so obtained are intended to be used to program the microcontroller for implementation of the Digital Energy Meter algorithm adopted in the proposed design. Results from the experiment showed that the coil with lower resistance exhibited better linear response while the coil with higher resistance was better optimized by quadratic and cubic polynomials. These findings serve as design guide for local fabrication of the rogowski coils to be used in the proposed digital energy meter being developed for the Nigerian power market.