DENUNCIAS DE ABUSO SEXUAL EN UN CENTRO EDUCATIVO

This chapter provides a closer description of the system that has been chosen for the LCA and the parts that have been defined to be included. Figure 15 gives an overview of the system components and communication systems involved and their locations.

Central System, DSO

Database server Reading server Household Electronic meter Switch Communication module MV/LV substation Concentrator

Data transfer with PLC Data transfer with GSM Network

Figure 15: System solution chosen for the LCA

3.1.2.1 Electronic meter

An electronic meter’s main function is to meter and show electricity consumption as kWh. This was in the past done with mechanical meters that consisted of a spinning disk and a mechanical counter, and manual reading of the metered values was necessary. The meters used for smart metering technologies are digital and have the functionality of digitalizing the metered values, and then use two-way communication to transmit them.

The development of digital meters started several years ago and the term smart meter came into existence as a consequence of the technology changes on the field. The term “smart metering” is not universally defined and several definitions exist in literature. The European Smart Metering Alliance’s (ESMA) definition of smart metering is (Koponen, 2008):

• Automatic processing, transfer, management and utilization of metering data • Automatic management of meters

• 2way data communication with meters

• Provides meaningful and timely consumption information to the relevant

actors and their systems, including the energy consumer

• Supports services that improve the energy efficiency of the energy consumption

and the energy system (generation, transmission, distribution and especially end use)

In the meter, the metered values are digitalized and received by a microprocessor. The microprocessor can either be accessed directly from the surrounding communication system, or an additional unit, a terminal, works as an interface. Depending on its complexity,

terminals can analyze the signals to obtain for example voltage and active and reactive power. Internal software runs the circuits in the meter. The possibility of remotely update of the software is one of the advantages two-way communication provides (Amundsen, 2006).

-29-

The term “integrated meter” is often used when a meter and a terminal are integrated in the same component. If the terminal and meter are two separate components, an additional communication level is required (Amundsen, 2006). As integrated meters are the most common on the market nowadays the term “meter” will from now be used for “integrated meter”.

The Measuring Instruments Directive (MID) specifies the minimum requirements for all utility meters used for billing purposes in Europe, in addition to the quantities that meters must be able to measure. For electricity this is kWh of active energy. Other quantities that are possible to measure are for example reactive energy, instantaneous power, and maximum demand and consumption data. These are additional services compared to what a mechanical meter can provide. A meter today generally comes with additional functionalities and they support several interfaces. Examples are digital inlets and outlets that can be used for sensors for water and alarms, and the performance of remote load control.

3.1.2.2 Communication module

The communication module is specific for the communication system used. The function is to transmit the data stored in the meter through the selected communication system. Depending on if the communication solution is 1-n or 1-1, the communication is to a concentrator or DSO. The module itself can be an integrated part of the meter or it can be put in place in the meter during the installation at the household. The possibility to choose between different communications systems is a key point to provide flexibility, and this is made possible when the meters support several communication modules.

3.1.2.3 Switch

A switch provides the opportunity to remotely switch on and off power supply, for example if a customer’s residence is empty for a period of time. It can be delivered separately or

preassembled to the meter. The switch is connected to a semi-conductor relay in the meter, which receives data from the system at central level. During operation, the system at central level can either control the electricity consumption of the customer completely or partially. If partially control is performed, the customer has the opportunity to push a button on the meter to turn on the power supply.

3.1.2.4 Concentrator

The concentrator is a central part of a 1-n network structure and connects to meters in several households. Its function is to receive data from household’s meters and transmit the data further through to the DSO. It can also store the data for later retrieval by the system at central level.

3.1.2.5 Power Line Communication (PLC)

PLC is a well-known technology for the transmitting of data and it can be used for

communication over all levels in the system. The technology uses existing infrastructure for electricity distribution to send data. The solution can be used at all voltage levels of the grid and can be separated in three different parts with respect to this; communication on high voltage grid (HV), medium voltage grid (MV) and low voltage grid (LV).

-30-

The principle for sending data is modification of the frequency of the signals. There are several techniques available for the modification and different system suppliers often have different choices. One technique is to modulate the signal between two defined frequencies, known as frequency shift keying. Another way is phase shift keying, which modulates the phase of the carrier signal, normally with 180̊.

The components necessary to use PLC will vary depending on the voltage of the transmission grid and number of metering points in the system. In this analysis a low voltage distribution grid between concentrator and households is chosen. The concentrators are installed in MV/LV substations.

3.1.2.6 GSM network

Global System for Mobile communication (GSM) is a digital cellular system used for connecting two devices and exchanging data, in Norway operating at radio frequencies 900 MHz and/or 1800 MHz (Amundsen, 2006). General Packet Radio Service (GPRS) is a data extension of GSM, using the existing infrastructure of GSM to send data. The GSM network has a good coverage in Norway and is accessible from most locations. 99,9% of the

population is covered by the leading provider of mobile communications (Telenor, 2011).

Related to the communication system, the central system usually has GSM modem pool, which is a communication solution for contacting the concentrators and request data. The concentrator has a GSM modem to communicate with the central system (Amundsen, 2006).

3.1.2.7 Central system components

The central data system is the interface between the communication system towards the metering points and other adjacent systems to exchange information with. The central system’s task is to collect data from the metering points and transfer it to the adjacent systems. The adjacent systems are for example customer information system, information about the network and a database for meter values.

Hardware components and setup for the central system depends on the system solution and requirements, but it will at least involve two types of servers, database server and reading server, and a communication setup. Some system solution examples are shown inFigure 16, based on example solutions provided from a supplier of smart metering technology (Aidon, 2011).

-31-

Figure 16: Some possible system solutions for central system, adapted from (Aidon, 2011)

The figure shows that the number of metering points affects the number of necessary components in the system and it will be scaled after this parameter. Additional components such as back-up servers are also possible to include. The communication setup included also depending on the number of metering points. Such a setup can include an additional server and a collection of communication modems adjusted to the system involved.

-32-