Power subsystems

Although the original ALIS paper [Steen, 1989] stated that some stations would have to generate their own power, all GLIPs deployed so far have been located close to commercial power lines.

In Sweden, a typical electricity account gives access to $3 \times 16$ A at $230/400$ V AC which provides much more than sufficient electrical power (about 11 kW) for heating and powering the GLIP. Thus only the energy cost has been of concern.

The electrical installation in the GLIP has more fuses than a typical household installation in order to minimise the loss of function caused by blown fuses.

The incoming power lines pass through the mains switch, energy meter and surge protection circuits before entering the main fuse box. There is a relay box for remote-controlling the heaters, defrosters, etc. (see Section A.2) from the housekeeping unit (Section A.4). Three thermostats are used for fail-safe temperature control if the housekeeping unit should fail to control the temperature properly. There are a number of outlets (230 V/10 A) for equipment and a three-phase outlet ( $3 \times 10$ A $230/400$ V). Figure A.5 shows some of this equipment.

Figure A.5: The electrical installation of a GLIP. The cooling fan is seen in the upper-middle part of the image, below it is the environmental control unit (ECU) with thermostats and relays. To the right is the main fuse box and far right the main fuses and mains switch.

The Power Distribution Unit (PDU) (Figure A.6) distributes

Figure A.6: Rear view of the Power Distribution Unit. The fuses are seen on the front panel (top), the relays for remote control are on the upper row, below them are surge filters and a terminal board. The bottom row contains the power sensors. The outlets are mounted on the back panel.

mains power to most subsystems at the station. The PDU contains eight independent outlets (230 V/10 A) with a power sensor and additional surge protection on each outlet as well as on the three incoming lines, thus enabling the housekeeping unit to monitor power failures on any of the incoming three phases as well as power distribution problems related to the PDU itself.

There is also a 12 V 75 Ah lead-acid battery with an automatic charger powering the housekeeping unit and other devices requiring an uninterrupted 12 V DC supply, such as the GPS receiver, etc.

A GLIP consumes up to 10000 kWh annually. Most of this energy is used by the heating and defrosting equipment. Some sites have had a rather large number of power failures, and it has been suggested that an Uninterrupted Power Supply (UPS) should be installed at each station to prevent the loss of measurements due to transients and short-term power outages.

If GLIPs are to be mounted in remote areas with no commercial power, they might have to generate their electrical power on site and therefore might require other solutions for heating and defrosting the dome.