Vamp Ltd. (Vassa, Finland) has delivered the VAMP 255 Feeder Manager relays for AIL Elettricitá's (Lugano, Switzerland) 150/16-kV substations. The Feeder Managers are installed in the substation's incoming feeders for fault-location function. Before the investment decision, AIL Elettricitá thoroughly tested the performance tolerances of the VAMP Feeder Manager relays. Test results have been positive, and AIL Elettricitá has found the performance accurate both in the primary tests and laboratory environment.

AIL is a utility managing the distribution of the electricity, gas and water at the southern part of Switzerland near the Italian border. With 250 employees, AIL is the biggest distribution utility in the Italian-speaking part of Switzerland. AIL Elettricitá, AIL's electricity distribution department, has interconnection from the 220-kV network to its seven substations with secondary voltage levels of 150, 50 and 16 kV. They have 104 medium-voltage (MV) feeders supplying a 635-km (58- mile) cable and overhead line network at 16 kV and 1412 km (878 miles) of low-voltage (LV) network. AIL Elettricitá supplies 90,000 customers with 100 GWh annually.

The project was identified by the need to quickly locate and restore the faults on the MV overhead line network. Installing the new fault locators enable AIL Elettricitá to transfer the fault-reactance values directly to the duty officer's GSM phone by SMS messaging. AIL Elettricitá has already installed a distribution management system (DMS) for its high-voltage (HV) network and plans to further expand the DMS system to include the MV distribution system. The installation of the fault-location units should support the future expansion of the DMS system.

When planning the investment, AIL Elettricitá went through a thorough testing procedure of the VAMP 255 Feeder Manager relay's fault-location function.

Marco Veri, head of the substation department at AIL Elettricitá, says, “The tests were performed both as primary tests at the substation and in the laboratory environment. At the primary testing, the VAMP 255 unit was connected to the 10 MVA, 150/16-kV transformer feeder at the Mendrisio Substation, a feeder comprising cable and overhead conductors. A two-phase short circuit was created at the sectionalizing point with the reactance of 3.21 Ω (distance of 11.13 km [6.92 miles]). VAMP 255 calculated a reactance of 3.29 Ω corresponding to 11.33 km (7.04 miles), thereby resulting in an accuracy of 2% and fault position within and 200 m (654 ft).

Furthermore, the performance verified in the laboratory using NEPLAN network simulation program resulted in an accuracy similar to primary testing with the error margin at the remote end faults being 3%; thus resulting in a very satisfactory performance.”

The fault reactance is transferred to the control system using communications. VAMP 255 Feeder Manager relays are communicating with existing RTUs by Modbus protocol.

Veri finds the VAMP relays communications capabilities beneficial. “All of our substations are equipped with the Ethernet connection, and the fault registers and disturbance recorder files of the VAMP 255 units are transferred via TCP/IP connection directly to our office PCs.”

Vamp Ltd., member of Vaasa Electronics Group, is a Finnish manufacturer of arc-protection systems, numerical protection relays and power-monitoring units.
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