Case study 3

Fortum is a leading electricity distribution company in Northern Europe. It operates and manages regional and distribution grids in Finland, Sweden, Norway and Estonia, giving service to approximately 1.6 million customers. Fortum is a growing company constantly developing future energy solutions and focuses on investing in network maintenance and automation, further improving reliability and quality of the supply of electricity to its customers.

The target of this specific pilot project was to verify the functionality of the automatic FDIR concept. The pilot project is divided into two phases. In the first phase, 4 new line disconnectors and 2 new reclosers were incorporated into the distribution network and substation level distributed intelligence into the primary substation. The disconnectors are equipped with current sensors, which can support fault location indication to the DMS 600, in order to determine accurate fault locations. The devices are equipped with current sensors, which can supply data for the substation system and for the distribution manage-ment system, for determining fault locations. Locations of the new devices were selected based on feasibility calculations made with Luova reliability analysis tool (ABB´s relia-bility analysis software) and on the basis of historical fault data. [150]

Additionally, the substation protection equipment was renewed using IEC 61850 compli-ant 615 protection relays of the ABB Relion product family to provide improved protec-tion and fault distance calculaprotec-tion capabilities, especially for earth faults. The replaced static protection relays that initiated in the 1970´s were not able to accomplish the new requirements when it comes to fault data recording, modern TCP/IP communication and earth-fault protection. [150]

In the system illustrated in Figure 5-1, control and automation functions can be found at both local, substation and control center levels. A system that keeps track of the existing loads at various locations and supply capability of alternative network configurations sup-ports fast implementation, fully automatic fault location, fault isolation, network recon-figuration and power restoration functionality, i.e. the creation of a self-healing power distribution network. The latest advance has made it possible to locate some functionality also to the substation level.

Figure 5-1: Automation functionality at different locations in a distribution network using a combined approach [150]

MicroSCADA Pro DMS 600

MicroSCADA Pro DMS 600 is a distribution network management system (DMS), which is able to extend traditional SCADA competences by providing geographically based net-work views and advanced distribution management functions over the entire medium voltage network. DMS 600 integrates static information stored in the network database (NIS) with real-time process data acquired through the SCADA system. DMS 600 fea-tures tools for comprehensive network topology management providing maintenance of switching status data, connectivity analysis and topology representation via feeder color-ing, rapid and precise fault location, analysis and advanced outage planncolor-ing, which es-sentially reduces outage duration.

Automatic Fault Detection, Isolation and Restoration (FDIR)

In the first phase of the pilot project, the DMS had a central role in order to provide the FLISR functionality. DMS enabled accurate and reliable information regarding the net-work situation. When a switching sequence was created, information about netnet-work loads, open connections, occasional earthings, ongoing construction work, etc. had to be considered. Solutions in networks including DER and demanding data maintenance con-cerns are somewhat easier to handle in a reliable and dependable way in the centralized DMS system.

In the second phase of the pilot, though, the feasibility of running the FDIR functionality in the substation system (COM600) is verified. With this decentralized DMS/FDIR ap-proach the central system is not required to be directly involved in the process related to a specific substation. The feasibility of such solution depends on the capabilities of the selected systems as such and their ability to work together [150].

The DMS gives information on both the number of outages and their duration.The oper-ation sequence of the FDIR functionality incorporated in the DMS system follows that the distributed intelligence in the substation serves the DMS with a fault report. The SCADA system delivers to the DMS system the position indication of the disconnectors and recloser, also including the status of possible fault indicators. Then, the DMS system locates the fault and creates a switching sequence for isolation of the fault and for resto-ration of the power supply to make use of alternative supply routes (back feed). The switching sequence is sent to the SCADA system for fulfillment and the SCADA puts it automatically into practice. This is done step by step so that the sequence does not proceed to the next stage until the site indication has been received from the switching device.

Tripping of a breaker during the sequence will stop the sequence.

The communication means for the project uses the public network (GPRS) for the net-work automation devices via IEC 60870-5-104 communication with the SCADA system, which cooperates with the DMS system. The substation level distributed intelligence (running on the COM600 grid automation controller) and the substation RTU communi-cate with the control center by means of a private fiber optic TCP/IP network.

Lastly, in the fault management process the following levels of the distribution network take place:

- Bay level in the substation: modern protection and control relays offer versatile protection algorithms for earth fault detection. The protection functions allow fast and selective protection. The start signals of protection functions are triggered into a disturbance data recording using the COMTRADE format. The data recording admit prediction of non-permanent earth faults in the network. Furthermore, the recordings include status indications of the circuit breaker and auto-reclosings based on the events.

- Protection zone level: the reclosers in the line feeder enable automatic isolation of the fault into the dedicated protection isolation zone. The status indications of the circuit breaker and the auto-reclosings are directed to the upper level. The disconnectors equipped with fault indicators are able to transmit status indications and measurement data from the fault indicators.

- Distributed intelligence in the substation: disturbance data recordings are stored in a grid automation controller. The controller calculates distance estimations of network faults immediately after a fault situation (semi-online). The grid automa-tion controller creates a fault report containing the distance estimaautoma-tion informaautoma-tion and sends it to the DMS.

The results and considerations learnt from this project are described in Table 5-1. As it was mentioned in other practical experiences of the self-healing concept, this pilot case had also the target of improving the reliability of the electricity distribution network as well as to significantly enhance the power quality experienced by the customers located among the concerned feeders in the Kirkkonummi area. Major driving factors for the in-vestment were, on one hand, strengthening the Finnish regulatory influence, and, on the other hand, the necessity to shorten and improve fault location times, reliability and ac-curacy, especially for earth faults [150].

Table 5-1. Effects of the pilot case on the reliability of the distribution network

Function Decrease of SAIFI Decrease of SAIDI Comments

New protection zone 30-40% 20-30% Downstream faults not

affected

Fault location - 50-60% Trial connections can

be omitted

Fault forecasting 20% - Permanent fault

proba-bility reduced