Cover story t SponSored FeATUre


Figure 1. DC energy metering in the EV fuel station of the future.


charging the colocation customer by power use. The two most popular ways to charge colocation customers for power usage are:


Per whip (flat fee for each outlet)


Consumed energy (metered outlet - power charged for each kWh consumed) With a view toward encouraging power


efficiency, the metered output approach is gaining popularity and customer pricing can be described as:


Recurring cost = space fee + (meter reading for IT equipment × PUE)


dc conversion and, consequently, billing is inaccurate for the end customer. Since 2019, new EU regulations are forcing energy providers to bill the customer only for the energy transferred to the EV, making the power conversion and distribution losses borne by the energy supplier. While state-of-the-art SiC EV converters can reach efficiency above 97 per cent, there is a clear need to enable accurate billing on the dc side for fast and ultrafast chargers, where energy is transferred in dc when directly connected to the battery of the vehicle. In addition to public EV charging metering interests, private and residential peer-to-peer EV charging schemes might have even more incentive for precise energy billing on the dc side.


DC Distribution - Microgrids What is a microgrid? In essence, a microgrid is a smaller version of a utility power system. As such, safe, reliable, and efficient power is required. Examples of microgrids can be found in hospitals, on military bases, and even as part of the utility systems where renewable generation, fuel generators, and energy storage are working together to make a reliable energy distribution system. Other examples of microgrids can be found in


buildings. With the wide deployment of renewable energy generators, buildings can even become self- sufficient, with rooftop solar panels and small-scale wind turbines generating as much energy as is used, independent but backed up by the grid. Moreover, as much as 50 per cent of a


building’s electric loads run on dc. Currently each electronic device must convert ac to dc power, and up to 20 per cent of energy is lost in the process, with a total savings estimated up to 28 per cent vs. traditional ac distribution. In a dc building, energy consumption can be decreased by converting ac to dc all at once and feeding dc directly to the appliances that need it, such as LED lights and computers. Interest in dc microgrids is rapidly growing, as is the need for standardisation. IEC 62053-41 is a pending standard that


indicates requirements and nominal levels for residential dc systems and enclosed type meters similar to the ac equivalent for dc energy metering.


Instrumentation Monthly August 2021


Continued on page 10... 9


The dc microgrid segment is valued at around $7 billion as of 2017 and will see further growth from the emerging dc distribution trend.


DC Data Centre Data centre operators are actively considering different technologies and solutions to improve the power efficiency of their facilities, as power is one of their largest costs. Data centre operators see relevant benefits in


dc distribution as the minimum number of conversions required between ac and dc decreases, and the integration with renewable energy is easier and more efficient. The reduction of conversion stages is estimated as:


Five per cent to 25 per cent energy savings: increase in transmission and conversion efficiencies, and less heat generation


2× reliability and availability


Thirty-three per cent floor space reduction Distribution bus voltages range up to around


380 VDC, and accurate dc energy metering is gaining interest since many operators are


switching to the more measurable approach of


Figure 2. DC energy metering in a sustainable microgrid infrastructure.


Space fee: fixed, includes security and all the building operational costs


Meter reading for IT equipment: the number of kWh consumed by the IT equipment multiplied by the cost of energy


Power usage effectiveness (PUE): takes into account the efficiency of the infrastructure behind IT, such as cooling


A typical modern rack consumes up to 40 kW of dc power. Therefore, currents up to 100 A are required to be monitored with billing- grade dc meters.


Challenges in PreCision DC energy Metering


In the early 1900s traditional ac energy meters were entirely electromechanical. The combination of a voltage and a current coil was used to induce eddy currents in a rotating aluminium disc. The resulting torque on the disc was proportional to the product of the magnetic flux generated by the voltage and current coils. Finally, the addition of a breaking magnet for the disc made the rotational speed directly proportional to real power consumed by the load. At this point, measuring the energy consumed is simply a matter of counting the number of rotations over a period of time.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78