Integrid - Bridging the Gap

51 SRS is located in the central area of Stockholm with a typical new urban structure with double cable system. The typical customer in the area is residential, there are also PV-installations and EV-charging stations connected to secondary substations. The focus has been to increase the reliability and operation of the medium voltage distribution grid by collecting more data and implementing a higher level of monitoring. The secondary substations are all of highmeasurement and monitoring level and wireless. There is current and voltage measurement on both the medium and low voltage side as well as temperature measurement. Moreover, alarm, events and fault indicator information from the stations are sent to the operation centre. The stations included in InteGrid all have double cable systems with automatic switchover if a fault occurs in the cable. Furthermore, dry transformers are used with temperature measurement on windings. The number of parameters measured or calculated varies between the stations, and the values are updated every 15 minutes with min, max and average RMS values for each parameter. Figure 4.27 – The grid structure for line 1 and line 2 Cable Trol Line Trol Switch Cable Trol Line Trol Switch The Ekerö demo site is situated in the outskirts of Stockholm and part of the grid is called Ekerö. The grid layout can be regarded as a typical rural network with a radial structure and a mix of both overhead and underground cables. There are a number of primary substations in the Ekerö grid, but in the scope of InteGrid, two primary substations are considered, and more specifically one line for each substation, as can be seen in Figure 4.20. The two lines where selected because they have already been subject to a pilot project with the aim of evaluating the performance and gains of using fault indicators in the grid. The primary substation is indicated with a dot enclosed by a circle and secondary substations by dots. The placement of fault indicators and disconnectors is also shown. A total of twelve indicators were mounted in the networks, eight in overhead lines and four on underground cables. Communication between the fault indicators and the SCADA system is through SMS via GSM to a GSM link router up to Ellevio’s SCADA. Fault location technology at Ekerö will reduce repair time, costs and lost customer minutes, and customer total service restoration time. The Kyrkviken primary substation is located in Lidingö in Stockholm. The station has two parallel 20 MVA, 70/10 kv transformers with 18 outgoing bays and around 22,000 LV customers, who are mainly residential together with a few larger plants and factories. Transformers are equipped with tap-changers with 19 steps, regulating the voltage by 1.67 %. In 2014, the station was retrofitted with a Centralized Protection and Control system (CPC) which runs in shadow mode to the old protection and control system. The CPC system uses one central CPU for protection and control instead of using distributed intelligent electronic devices (IEDs) in each bay on 10 kv and partly on 70 kv. An overview of the centralized system can be seen in Figure 4.21. The focus in Kyrkviken for the InteGrid project has been on asset health and voltage regulation. Several protection functions have been developed for the system to have equivalent or increased protection when compared to the existing protection system. The CPC protection functions are compared with the existing conventional system. The outcome of InteGrid is expected to be applied to the next generation of substations and Ellevio will build a 10/0.4 kv substation based on InteGrid results. The new stations built will have high monitoring level and flexible communication solutions, wireless or wire, depending on the actual environment. We expect load and generation forecasting as well as the implementation of DR, which is important when hosting DER as well as the development of a charging infrastructure for EV. Amore detailed overview of the demo-sites can be found in InteGrid public deliverables and Public CIRED papers. SRS report and master thesis papers describe the demo site in more detail from different perspectives. Please see the reference list.