Mexico has more than 102 million inhabitants, distributed in 200,000 communities across the 2 million km2 that constitute the national territory. In order to supply electricity to a large number of communities in Mexico, of which only 1.5% are urban, the Federal Government has nominated two decentralised parastatal companies – Luz y Fuerza del Centro (LyFC) and Comisión Federal de Electricidad (CFE). LyFC supplies electricity in the City of Mexico and surrounding areas, while CFE services the rest of the country.
The infrastructure of both companies comprises 175 generation stations, 1,700 substations (in voltages from 13.8 kV to 400 kV), almost 700,000 km of transmission and distribution lines and more than 1.06 million distribution transformers. Together they supply electricity to 95% of the population of Mexico.
A robust structure of human, material and financial resources is required to measure the consumption of 26 million clients at thousands of points, such as generation units, transmission lines, distribution circuits, voltage transformers, electricity junction points between companies, concessionaires and countries. The diversity of tariffs, such as escalating, hourly and interruptible, and other factors such as time and seasonal changes, make metering a vital part of the commercialisation process.
Fig 1. CFE Overview - customers
The meters used vary, depending on the function being carried out, and are of the following types:
- Residential and commercial customers and LV services: Electromechanical Watthour meters of one, two and three phases, 120/240 V, error class 2 percent.
- Industrial and commercial customers and MV services up to 749 kW: Solid state meters, kWh/kW/kVArh, three phase, 120/ 240/480 V, error class 0.5 percent.
- MV industrial customers with demand of 750 kW and above and HV customers: Electronic multifunction meters kWh/kW/ kVArh, three phase, 120 V, error class 0.2 percent, with memory for recording usage profile every 5 minutes, using telephone modem or Ethernet port for remote reading and measurement of energy quality.
All our meters must comply with the Normas Oficiales Mexicanas (NOM), which are based on the ANSI and IEC standards NOM-044-SCFI-1999 (Electromechanical Watthour meters) and NOM-127-SCFI-1999 (Multifunction meters).
The process of evaluation of the meters takes place in three steps. The first is the execution of tests of the prototype by the primary laboratory, using the applicable NOM standard. The second step is to undertake acceptance tests in CFE’s workshop. Finally tests are performed on installed meters already in the field, to check that they meet the standards required for the type of meter and year of manufacture.
To ensure that the meters meet national and international standards, CFE works with 13 secondary meter laboratories as well as a primary laboratory, all of which are accredited to Normas Mexicanas de Laboratorios de Calibración and are ISO 9001/2000 certified. CFE also has 116 workshops distributed around the country, for the calibration and repair of meters.
Fig 2. Energy meters installed (by type)
Fig 3. Energy meter approval process - traceability chart
Currently the possibility of using meters of one, two and three phases is being evaluated for low voltage residential and commercial customers, who account for more than 95% of all installed meters. We are also evaluating different technologies for remote meter reading (AMR) in order to determine the best option for each type of customer, given the existing geographic conditions and electricity network.
In another development, with the aim of guaranteeing the correct meter reading, CFE is undertaking a programme to replace obsolete meters. More than 600,000 meters have been replaced in the past three years. At the same time a programme of meter testing in the field has been undertaken, and some 1.7 million meters are tested annually.
Our customer base grows at an annual rate of 4.5%. The challenges which face the electricity companies in Mexico consist not only of assuring the availability of meters to supply new customers – which in the case of CFE means around 2 million new meters per year – but also ensuring that the political will exists to undertake the introduction of new technologies, oriented to the improvement of processes which will in turn improve the service to electricity customers.