Spark gap surge arrester for direct current OLE line

System suitable to ensure surge protection to equipment and devices connected to (Overhead Line Electrification) OLE lines operating under direct current. Present situation At present, in railway systems, the surge protective device which protects the contact line is implemented in double technology: varistor section which is used for suppressing low-energy surges like the ones generated by transients due to switch opening during operation. The working principle is based on the change in impedance as applied voltage changes, and for this reason these devices are referred to as auto-resetting since once the transient event is over, they will return to their original condition; spark gap section which, in comparison with varistor section and on equal size, features very high heat dissipation capacity and therefore very high discharge capacity; this property is used for managing high and fast-rising energy typical of lightning surge. Gas-filled surge arresters after dissipating the thermal energy of lightning will stay short-circuited and so, once the event is over, the DC contact line will result to be at short-circuit. Usually, after discharge, energy dissipated by contact line via short-circuited surge arrester will cause unrecoverable damage of the surge arrester itself (times in the order of ms) as well as the opening of ultra-fast circuit breakers, distant even 5 km from the place of the lightning. As a consequence the section included between two adjacent substations will be powered off with inevitable detriment to the revenue service. Also in the lucky event that the surge arrester damage won t short-circuit the line, surge arrester replacement will however be required since the contact line results to be unprotected. Spark gap surge arrester by Ansaldo STS The Ansaldo STS product being dealt with concerns a surge protective device without varistor section, consisting of new technology single spark gap surge arrester characterised in the advantage of being auto-resetting for any keraunic activity which shall involve it up to 25kA current values. At test stage every single component has been tested with six discharges, one every ten seconds, with 0-350us waveforms and 25kA current, in order to check functional product quality. 2 3 4 5 At circuit level, spark gap surge arresters (identified with Fx and Fy) are located between the power substation [] or OLE cabin 3,6kVdc bus bar and the ground system. Jx and Jy: ultra-fast circuit breakers with line overload protection function. SBx and SBy: cell double pole disconnectors charged with isolating upstream and downstream the relevant ultra-fast circuit breaker for safety during maintenance operations on ultra-fast circuit breaker. Sx and Sy: first row horn disconnectors (holding) which guarantee contact line insulation during maintenance operations. Sxy: second row horn disconnector (kept normally open at current rush), which when closed implements electric substation metallic continuity required for maintenance operations. [4]: OLE contact line at risk of lightning and therefore the object of protection. [5]: rail level. [2] and [3]: two different ultra-fast circuit breaker cells.

Tests at laboratory Test measurement with 8/20us waveform and 25kA current. Measurement has been carried out according to circuit. Please note, in the blue diagram, the behaviour of the 3.6kV line voltage which persits after the discharge proving the auto-resetting of surge arrester. 2 Test with 0/350us waveform and 25kA current Test repeated six times in a minute with direct and reverse polarity, on prototype sample (Laboratory: DEHN + SÖHNE GmbH + Co.KG. Neumarkt Germany) Test measurement with 0/350 us waveform and 25kA current. Measurement has been carried out according to circuit 2. Waveforms, relevant to direct natural lightning, prove device suitability and conformity. (Laboratory : DEHN + SÖHNE GmbH + Co.KG. Neumarkt Germany) 2

Tests on site Test installation at the railway station in Bibbiena (AR). Testing started on the month of October 202. Traditional surge arrester 2 Ansaldo STS s surge arrester 2 Accessories The SPD system can be installed with an associated device referred to as «impulse counter» which is provided for counting the surge arrester reactions. The abovementioned device consists of the following components: toroidal current sensor [] specially designed for railway applications and located on surge arrester ground connection cable; impulse counting device [2] for counting impulses coming from the toroidal sensor and therefore the surge arrester reactions. Impulse counter is installed on the post which mounts the surge arrester, into an appropriate protecting container with proper protection rating (IP). If required, parameters read by the abovementioned device can be remotized via data transmission system. 2 3

Surge arrester layout General features Product name: Surge arrester for DC contact line Part number: 00A.0008 Power supply Nominal voltage: 3.600 Vdc Nominal absorbed current: negligible Power absorbed in standby: negligible Power absorbed during normal operation: negligible Lightning discharge current (0-350us waveform): 25.000A Mechanical features Size [mm]: 90 diameter x.090 height Weight [kg]: 7 approx. Environmental and climatic features IP protection class: 55 Working temperature [C]: 25 70 Storage temperature [C]: 40 70 Height: not significant Relative humidity: 90% without condensate. Copper nickel terminal. +3.6kVdc side pole 2. 750Vdc. cartridge enclosure 3. 750Vdc cartridge section. 4. Copper nickel joint for coupling adjacent cartridges 5. Copper nickel terminal. Ground side pole. In figure, 3,6kVdc models Diagnostic Maintenance tools: impulse counter module Norms & Standards Compliance: CEI EN6643-. Reliability, availability and maintainability MTBF [h]: > 250.000 MTTR max. [h]: 30 (excluding the operations for setting the subsystem under safety conditions) Safety SIL level: not applicable Safety certifications: Laboratory tests according to product standard CEI EN6643-. Available configurations Surge arrester can consist of a variable number of cartridges in series, each of which operates at 750Vdc rated voltage The table below shows the different surge arrester available configurations implemented for fulfilling the different application requirements. OLE voltage Cartridges Specific application 500Vdc Trolleybus 750/900Vdc 2 Light rails and tramways,5kvdc 3 DC railway lines (France) and metro lines 3kVdc 5 DC railway lines (Italy) 4

Ansaldo STS SpA Via Paolo Mantovani 3 5 65 Genoa Italy www.ansaldo-sts.com