In tunnels and underground structures, we provide the layer between the power supply and the loads: enclosures and cabinets housing electrical apparatus, solid-state switching devices for ventilation, drainage pumps and heating circuits, energy and network-parameter metering in facility switchboards, and identification systems for cables and apparatus. Conditions are harsher than in a station building: humidity up to 100%, dust, vibration from passing trains, restricted service access and the electromagnetic field of the 3 kV DC traction system.
Volume V of the PKP PLK Technical Standards defines the framework for selecting these components. Equipment is kept outside the 5 m zone from the centreline of an electrified track; where this is impossible, metal structures and enclosures are bonded directly to the rails when resistance to reference earth is above 20 Ω and indirectly when it is below 20 Ω (PN-EN 50122-1), while conductors are routed in protective systems suitable for exposure to 3 kV DC. Protection against stray currents is governed by PN-EN 50122-2. Ventilation in enclosed and underground facilities is a load requiring enhanced continuity of supply - two independently supplied feeders are switched by an automatic transfer system. Circuits supplying distribution cabinets operate in a TT system with residual-current devices; sockets up to 20 A that are accessible to portable equipment use IΔn ≤ 30 mA protection. Varistors or protective diodes are used against supply-side overvoltages; permissible temporary overvoltages are Un + 250 V for disconnection times above 5 s and Un + 1200 V for times up to 5 s. Equipment status is reported to the local control centre using the states: ready, on, off and fault.
Products used here from our range include: the Varistar CP EMC & Signaling cabinet for trackside technical rooms (shielding up to 18 GHz, IP55, LSZH materials in accordance with EN 45545-2, resistance to trackside shock in accordance with EN 50125-3), AISI 304L/316L stainless-steel trackside enclosures rated IP66 and IK10, IP-PRO Alu EMC aluminium enclosures rated IP67 and IK09 with shielding from 30 MHz to 4 GHz and EN 61373 category 2 resistance, RGC2 and RGC3 solid-state relays for contactless switching of fans, pumps and heaters, WM20/WM30/WM40 network analysers for switchboard measurements, and PATG HF markers and metal plates for durable identification of cables and apparatus throughout the service life of the facility.
