After many years of pilot projects and technological advancements in the industry, quantitive technical documentation about the viability of Powerline technology for Access networks has yet to be produced. There is a lack of evidence of the scale of bandwidth that BPL technology can provide in real world environments. So how does the technology fare over Medium Voltage (MV) utility lines in urban areas, complete with noise?
Yamaha Network Receivers
Noise on the MV lines is often caused by faulty capacitor banks, loose hardware, cracked insulators, etc. and is typically very large in cities. Utilities and system integrators need to determine how to deploy BPL technology to maximize performance in high noise environments.
Utilities are careful about deploying new technologies and conduct thorough tests in the worst parts of their grid prior to mass rollouts. Such tests were conducted at CenterPoint Energy, in Houston, Texas at the request of their careful and experienced project management team. The system integrator partner for the field tests was IBM. CenterPoint Energy and IBM identified the worst parts of the MV grid, characterized by the highest noise and oldest part of the network, for the testing. The results of the field measurements are summarized in this article and represent a positive contribution to the advancement of BPL technology
Additional factors limiting the performance of BPL access technology is FCC part 15G regulations which severely limits the output power of BPL technology. Unfortunately, the FCC rules were not available when silicon maker, DS2, released its Wisconsin technology to the market which set the frequency bands used in today’s BPL equipment.
The theory behind the situation we are facing when deploying BPL access technology is shown in figure 1.
Figure 1 â€“ BPL Communications Theory
The red line in figure 1 shows the noise floor of BPL equipment. The light yellow line shows the noise we expect on the MV line, however, due to the inherent ability of BPL technology to essentially ignore a certain amount of noise, we see the dark yellow line. The light green line shows the power output of BPL devices, however due to insertion loss of couplers and other accessories, we lose some power, hence the dark green line. The area between the dark yellow and dark green lines is the Signal to Noise Ratio (SNR) and determines the performance of our BPL network. Notice that we are anticipating higher noise at the lower end of the frequency spectrum (mode 1).
In reality what was measure on CenterPoint Energy’s grid in an urban environment is shown in figure 2. The lines have the same meaning, however, we see the yellow line, MV noise, is much higher than we expected, due to the factors mentioned earlier. We also see that the lower frequencies are somewhat noisier than the higher frequencies, as expected.
Figure 2 â€“ BPL Communications Theory
The situation gets worse however after implementing. FCC part 15G regulations that cap the power output levels of BPL equipment and ensure the protection of amateur radio frequency bands. Once the FCC power mask is applied to the situation, the real maximum power of BPL equipment, based on the Wisconsin reference design used by BPL manufacturers, is lowered significantly. The result of this is less SNR, meaning less bandwidth and less propagation distances. In some parts of the highest frequency band (mode 3) we can not even transfer data as the power of the equipment is actually below the level of the noise (green line at or below yellow line on right hand portion of chart). Figure 3 displays the problem.
Figure 3 â€“ Effects of FCC Part 15G
2 years ago Corinex introduced the concept of a pure Frequency Division Duplexing scheme for MV and LV BPL deployments, revolutionizing the cost and performance of BPL networks. To address the noise and technology problems after implementing FCC limits mentioned above, Corinex went to work developing a noise resistant version of the technology. After an iterative process involving 18 designs, lab testing and field testing, they introduced a new BPL device which performs better under high noise conditions, called the Corinex Noise Resistant (NR) MV Gateway. Corinex also filed 2 patents to protect the intellectual property they developed in this process.
Figure 4 shows the SNR available under the NR Gateway. One notices the increased resistance to MV line noise resulting in increased SNR (area between yellow and green lines) and a balanced signal transmission across all 3 frequency bands.
Figure 4 â€“ Effects of Corinex Noise Resistant technology
Corinex then compared the results of their standard MV Gateway versus their new NR Gateway in regards to distances and throughputs measured in the field. The area chosen was the Kirby substation in Houston, Texas where measured noise was -100dBm on average but above -85dBm (very high) between the first 4 nodes in the network. Figure 5 below shows the results.
Figure 5 â€“ Comparing Corinex Standard and NR technology
The Corinex NR Gateway performance was stable and achieved up to double the throughput and double the propagation distance of the Corinex Standard MV Gateway. In many areas of the Kirby circuit the Gateway count was reduced from 5 per mile down to 3.5 per mile. This means that less Gateways can be used in a given network, while delivering better performance, reduced hardware costs and reduced installation costs.
What about HAM operators you might ask? A representative from the Amateur Radio Relay League (ARRL) was on site and set up his equipment (antennas and other measuring equipment) underneath one of the Corinex devices. The HAM confirmed that Corinex technology is HAM friendly and did not impact HAM communications.
A new feature available in all Corinex MV Gateways is internal automatic frequency filters which reduce the complexity of installation and eliminate the possibility of linemen making an installation mistake. Corinex MV Gateways also have a battery backup option which ensures the BPL network stays online to deliver outage management information even when the power grid goes down. The battery option includes the ability to remotely monitor the health of the battery as well.
Although the Corinex hardware performs well under noisy conditions, the role of the system integrator is becoming even more important for utility customerers. Deployment of BPL technology may now be easier, with Corinex’s 2nd generation of 200Mbps FCC optimized hardware, but network planning is still essential given the different environmental conditions, applications, integration into other utility systems, budget, and the large number of product options the system integrator can tailor a solution from.
With 4 models of MV Gateways and 7 types of Access products in total, system integrators experienced with Corinex technology can make efficient BPL based proposals to benefit their customers. Over time the system integrators that spend the time to develop expertise with the technology will be fast and effective enough to design and deploy winning solutions for the market.
Utility environments do not consist of 100% high noise areas of course, they are typically a mix of high and low noise areas. The optimal topology for the network will thus comprise of a combination of various Corinex products addressing the utilities requirements, including applications and cost.
The two major application areas for BPL Access networks are for Broadband Access networks and for core Utility Applications like Automatic Meter Reading, Outage Management and Grid Optimization. The density of BPL Access products is determined by these applications, with Broadband networks requiring more devices and therefore higher infrastructure costs. An experienced integrator once again can help build an efficient BPL network.
With the latest enhancement to BPL technology presented in this article, it becomes obvious that system integrators must have a comprehensive understanding and experience in Access technology on one type of equipment. This focus will lead system integrators to specialize in the technology, enabling them to offer the broadest range of easily deployable solutions to their customers. The presented results in this article document that the newest generation of BPL technology, from Corinex Communications, deployed on 4 continents, delivers high flexibility and performance options for the benefit of all utilities regardless of the noise environment.
For more information on these field trials and Corinex technology, please contact:
Brian Donnelly VP Marketing and Business Development
+1 778 371 7697