Post on 04-Jun-2018
transcript
Smart Meter to HAN Connectivity: What Interface is
Best for Your Deployment?
By Networked Energy Services Corporation (NES)
Smart meter to Home Area Network (HAN) connectivity is an
important requirement driving customer engagement and allowing
utilities to get more value out of their smart meter investment. HAN
connectivity enables utilities to offer new services to customers
beyond simple billing applications. These higher value applications
include dynamic pricing, in home load control and energy monitoring
which have the potential to drive new revenue opportunities for grid
operators.
The two most popular ways to achieve HAN connectivity is through
the use of either the Multipurpose Expansion Port (MEP) interface or
Universal Serial Bus (USB) interface available in smart meters.
Utilities considering HAN connectivity should make sure the inter
face they choose complies with the following requirements:
• Hot-pluggable
• Ability to supply limited amounts of power directly to the device
• Data uplink / downlink implemented through the full stack of the
architecture independent of the attached device
• Protocol is not proprietary and an open published specification
• Protocol has to implement at last two levels of authentication
with a read only access and a read/write access
• Protocol has to implement data payload encryption
This article evaluates these popular interfaces with case examples
from three recent utility MEP deployments in Austria and Finland.
MEP and USB Interoperability with Smart Meters and
Smart Grid Devices
What makes MEP different to a standard serial port is that this
interface was designed to enable developers and utilities to extend
the functionality of smart grid devices and smart meters. MEP is a
flexible, open and powerful interface which allows smart meters with
a MEP option to be integrated into any kind of HAN including MBus
(Wireless or Wired MBus), ZigBee, LonWorks,, etc. The MEP
protocol is a session-less, bi-directional protocol built on ETSI GS
OSG 001, the Open Smart Grid Protocol with authentication and
encryption of all message exchanges.
When provided on smart meters, in general MEP is just a four wire
hot-pluggable serial port, optional offering +12V on a fifth wire to
power attached devices. The total energy consumption of a MEP
device cannot exceed 1W.
Figure 1
USB interfaces, on the other hand, were not specifically designed
for smart meters. The meter’s software must have a suitable driver
for the attached device and then must implement the functionality
to establish and receive communication over that interface. Even if
some general purpose drivers will work for a group of devices, the
meter has to implement communication stacks for those and it will
not be able to take advantage of the device’s specific features.
Considering this, the broad variety of available USB devices and
the openness of the system shrink down to only a few devices
with already implemented driver stacks embedded in the meter
firmware. Adding new generic USB devices will result in going
back to the meter vendor for a software update of the smart
meter. Implementing new drivers and functions in the meter
firmware will also result in a new homologation certification for
that firmware, which in turn means that adding some new USB
device will take a lot more time, effort and investment. In the case
of smart meters, the concept of having standard USB connectivity
turns out to be more costly in the end.
MEP works the other way around. The connectivity and
functionality implemented in the MEP device when attached to the
meter is shown in figure 2. In this example, there is no need to
change anything on the meter’s firmware when a MEP device is
replaced by some other MEP device. This ability to have 100%
interoperability means meters are future upgradable which lowers
the risks of deploying technology that becomes outdated over the
life of the investment. Because MEP even allows new firmware to
be downloaded directly to the MEP device, field service costs and
the cost of replacing hardware is dramatically reduced. Because
MEP was designed for smart meters and grid devices, the cost and
effort of the investment are dramatically reduced when compared
to the USB interface option.
Figure 2
MEP Case Studies and Real Deployments NES has implemented many successful HAN projects using MEP on behalf of their utility customers. The picture below shows how a hot-pluggable ZigBee modem was used to communicate with GEO In Home Devices (IHDs) for a successful HAN project Eltel completed for a utility in Denmark.
A second successful deployment is shown in figure 4 that demonstrates the success of having MEP as a truly open and flexible interface for a smart meter project in Linz, Austria. In this scenario, MEP is used in combination with a MEP to BPL and Wi-Fi gateway which opens up consumption data information updates for the end customer every second, in house electricity usage monitoring and control as well as interfacing with micro generation devices like solar panels.
A third successful deployment in Finland uses MEP with an integrated C-Band communication module as well as another option model with an integrated ZigBee modem. Using these modems Fortum Finland provides IHDs either connected via C-Band or ZigBee to work as a consumption monitor as well as energy control gateways.
Figure 4
All these projects can be used for reference visits showing that these solutions are real and working under real life conditions. To date, we have not been able to find similar large scale, real life deployments designed around a smart meter with a USB host that offers the same level of integration and success.
Figur