The chosen area provides opportunities for numerous tests. The goal in the field test is to install GridBox measuring instruments with a complete coverage of all nodes in the network area in order to be able to extensively and reliably validate the concept. As illustrated in Fig. 6, there are several controllable loads and PV plants with controllable inverters in the ewz pilot grid area. GridBox devices can send control signals to the PV inverters so that they provide reactive power for voltage control. Furthermore, tests for active power curtailment of the PV plants are carried out. In addition, there is a battery energy storage system (BESS) installation in the pilot grid area with a power rating of 120 kW and a nominal capacity of 720 kWh.
Most of the GridBox devices at ewz are placed within the distribution grid, either in transformer stations or in distribution cabinets. Some GridBox devices are installed next to house connection boxes. Data security is a crucial issue. The handling of the measured data has to be considered carefully, especially where the GridBoxes are installed at house connection boxes and the measurement data could be attributed to individuals. Therefore, adequate measures for guaranteeing the protection of customers privacy have been adopted.
In the low-voltage network, GridBoxes have been installed at almost all accessible points, i.e. on the low-voltage feeders of the transformer stations, the cable distribution cabinets in the streets, and the house connection boxes of the end customers. Figure 8 shows a GridBox installation in a distribution cabinet. In the medium-voltage network, GridBoxes have been installed in selected transformer stations along one substation feeder. While the GridBox base modules can be connected directly to the LV connection points for voltage measurement and power supply, the MV switchgears have been equipped additionally with sensored cable terminations, housing a resistive voltage sensor and a Rogowski-type current sensor.
At BKW, both voltage levels (MV and LV) are characterized by a radial structure. In accordance with a considerable share of overhead lines and pole-mounted transformers, this network was chosen as it is typical for rural areas. Furthermore several DG units, here photovoltaic systems and one small hydro plant, and controllable loads like water boilers are available. Due to the low customer density in the chosen grid area, the technical options for high volume data communication are very limited. The choice was between the landline DSL and the mobile phone network. In order to be as independent as possible from end customers and because this communication channel is already in use inside the company for remote meter reading, data is sent via the mobile phone network.
Accuracy for all measurement channels was verified by means of a laboratory installation with defined frequency, voltage, current and harmonics content. It can be highlighted that the total vector error for the voltage phasor measurement at nominal frequency and nominal voltage is in the range of 0.04 %, dominated by the magnitude error.
Какая разница? - подумал. - Я должен выполнять свои обязанности. Он поднял телефонную трубку и набрал номер круглосуточно включенного мобильника Джаббы. ГЛАВА 45 Дэвид Беккер бесцельно брел по авенида дель Сид, тщетно пытаясь собраться с мыслями.