Smart Meters Help Stabilize the Grid

 

Wolfgang Bauer, Siemens AG

In the telecommunications business most telephone calling and Internet surfing is done at fixed prices; the trend favors flat rates. But, there’s no flat rate for electricity, where, to an increasing extent, the ground rule is “use more, pay more.” That rule is likely to be applied even more stringently in the future.

With time-of-use pricing, which is opposite of flat rate pricing, if a customer uses his or her washer and dryer during peak demand periods, that customer will pay a hefty surcharge. But, if the customer does his or her laundry at night when demand is low, that customer will get a discount. On weekends, electric power might even be free. Why make things so complicated when customers like them simple? The obvious reason is that the best way to get people to save energy is through their wallets. Variable rates are, therefore, a key inducement for increasing environmental awareness. Until now, for instance, most consumers in Europe have received feedback on their electric power usage only once a year on a special bill. But now, legislators are starting to act. The European Union has noted in its directive on energy efficiency and services that customers must receive more information about their energy consumption. One way for utilities to follow those directives is to implement automated metering systems that can do more than the normal smart meter installation.

 

Case Study: Arbon Energie

 

In the summer of 2007, Swiss utility Arbon Energie AG decided that new installations not only had to fulfill more stringent demands than the old Ferraris meters, but also more than the smart metering systems available so far. The Swiss were already thinking of incorporating as many functions as possible that would characterize future smart grids.

Arbon chose AMIS, the Automated Metering and Information System from Siemens. The system acquires the data of households, special contract customers and the distribution grid structure and transmits it to the control center. With this information, the distribution grid operator is able to optimize its processes and offer its power suppliers and customers specific new services for better energy utilization. With its extensive information and communications technology, the system provides a two-way information flow that already anticipates some of the smart grid’s characteristics.

All multifunctional meters have a slot for an M-bus expansion module that, when installed, conveniently permits control and billing not only of power consumption but also of gas, district heat and water consumption. In the case of larger loads such as boilers, load switching devices are installed that switch the loads according to a time program or on a command from the load management in the control center.

In Switzerland, the law prescribes replacement of the multifunctional meters on the customer’s site every 10 years. Arbon Energie AG will complete this replacement ahead of schedule. The new multifunctional meters are already deployed at 600 customers’ premises in the area. In 2009, 300 load switching devices and seven data concentrators began operating in transformer substations. During 2010, the supply grid will be expanded further. In the case of AMIS devices, they must be connected because the devices configure themselves with the higher-level transaction server.

With the new AMIS meters, the utility can bill its customers for the true energy consumption every month. Advance payments and subsequent adjustments, which have already been outlawed in some Scandinavian countries, are history. Both consumers and power suppliers have greater transparency.

 

The Benefits of the Automated Metering System

 

Automatic remote meter reading and detection and billing of variable remuneration for the various tariffs or on- and off-peak load periods are already possible with smart metering. Automated metering systems, however, also work with bidirectional data communication. This permits complex grid operation and constant matching of power consumption and grid load.

The power supplier is therefore able to offer special tariffs depending on the grid load or time of day. The power supplier can influence its customers’ power consumption during off-peak periods by switching tariffs, thus ensuring a more even grid load. All stages of the power supply up to the household meter can be automated in an integrated and clear way. Data about grid state permits fast diagnosis of faults, minimizing outage times. Distributed power producers of regenerative energy, for example, can be integrated into the grid for billing. Moreover, the automated metering system can integrate water, gas and short-distance district heating in a uniform and transparent way.

In a simplified view, a good automated metering system comprises four hierarchically stratified function levels:

1. The lowest level is the grid level where multifunctional meters acquire customer data. This is where demand and energy are measured and the flexible tariff metering transmits the data over the low-voltage power grid to the utility’s 60 transformer substations using powerline carrier technology.

2. In low-voltage transformer substations, data concentrators collect the meters’ consumption data and the grid’s telecontrol data. The concentrated data is forwarded to the control center via a fiber-optic network that encompasses six nodes to form a fiber-optic ring. The data concentrators calculate the powerline- and transformer-related load data so that the load on the network infrastructure can be controlled.

3. Further data concentrators in the higher-level transformer substations collect and concentrate the data from the lower-level transformer substations and convert it for the necessary communication interfaces.

4. In the control center, two redundant transaction servers and an operator station with a connection to the business management level of the company exist. The transaction servers acquire all data, process it and then forward it to applications such as invoicing, collection and load profile data evaluation or load management.

In the event of customer complaints, the multifunctional meters permit instant diagnosis from the control center. For example, the meter can determine whether a fault is the responsibility of the grid operator or the customer’s equipment. The control center can respond in a matter of seconds. Via the integrated two-way communication, switching commands can be transmitted and devices adapted to the power supplier’s and grid operator’s requirements by remote parameterization.

If the meter is too far from the data concentrator, the multifunctional meter automatically functions as a repeater, thus providing redundancy. For example, if the transformer fails, the field devices of an area supplied by that transformer can connect to another transformer. In this way, for example, any connections can be implemented in the low-voltage network for maintenance work.

The centralized network management system configures the telecommunications equipment and data concentrators much more efficiently than was possible by separate management systems. All parameters of the multifunctional meters are administered centrally in parameter profiles and coordinated with the customer contract data and higher-level IT systems. Redundancy at this level includes support of a “hot standby” concept in which the hardware and software are duplicated in two separate systems.

 

Additional Advantages

 

One practical advantage is that the utility can control power supply flexibly. Previously, for example, the street lighting of the area supplied could be switched only on or off in unidirectional communication via the ripple control units. Today, however, the control center can switch street lights on or off on a selection of streets. It can, for example, light up individual streets and squares for special occasions. The control center receives feedback about the current switching states, but normally it allows the load switching elements to operate autonomously according to a specification.

The automated metering system is real-time capable and permits energy consumption billing that is easy for the customer to understand. Load data can be stored for the previous 60 days. Functions not considered decisive for individual households today may become important in the future when flexible price structures encourage consumers to adjust their behavior.

Even if a customer wishes to change his or her power supplier to meet changing requirements, the necessary reprogramming can be performed from the control center. This enables the customer to purchase power from the cheapest supplier under varying load conditions. The multifunctional meter can even transmit load data via the transaction servers directly to the billing system of the other power supplier.

Additionally, the metering system can ensure long-term investment protection through a modular expansion concept at every system level. Consequently, the meters with their interfaces for expansion modules represent an open communications platform over which future home automation services can be implemented and gas, water and district heating meters can be integrated. Furthermore, a DLC modem integrated in the terminal devices and data concentrators should be realized entirely in the firmware, both with regard to the physical layer as well as the communication protocol. As a result, it can be Wolfgang Bauer is solution lifecycle manager for Siemens’ specific automated metering system: the Automated Metering and Information System (AMIS), Sector Energy, Siemens AG.

 

 

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