Smart Meter to HAN Connectivity

What Interface is Best for Your Deployment?

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