The Depot Plug: UIC Leaflet 554-2 Shore Supply

Introduction to UIC Leaflet 554-2

When a passenger train arrives at its destination and the locomotive is uncoupled, the power goes out. The lights dim, the air conditioning stops, and in winter, the carriages rapidly freeze. However, passengers expect a warm train (“pre-conditioned”) when they board the next morning. You cannot keep a diesel locomotive running inside a closed maintenance shed, nor can you always leave a pantograph up on a siding.

The solution is “Shore Supply” (or Pre-heating Posts). UIC Leaflet 554-2, titled “Power supply to electrical equipment on stationary railway vehicles from the local network,” defines how to plug a train into the station or depot grid. It governs the high-voltage umbilical cords used to keep the train alive when the engine is gone.

Snippet Definition: What is UIC 554-2?

UIC Leaflet 554-2 is a technical specification for the electrical supply of stationary railway vehicles. It defines the interface between the fixed infrastructure (depot power post) and the vehicle. It specifies the compatible voltages (matching UIC 552 standards), the types of connectors, and the critical Safety Interlocks that prevent the train from moving while plugged in or the cable from being energized before insertion.

The Purpose: Pre-Conditioning

The primary operational goal defined in UIC 554-2 is Pre-Conditioning.

• Heating/Cooling: Bringing the interior temperature to a comfortable level (e.g., 20°C) before service begins, without using the locomotive.
• Battery Maintenance: Keeping the 24V/110V batteries charged so the control systems and emergency lights don’t drain overnight.
• Freeze Protection: Keeping water tanks and toilets from freezing in winter storage.

Technical Interface

Since international trains travel between countries with different voltages, UIC 554-2 dictates that the depot supply must simulate the locomotive.

1. Voltage Matching

The shore supply post feeds the train’s main High Voltage (HV) train line (the heating line). Therefore, it must output one of the standard UIC voltages defined in UIC 552:

• 1000 V AC (16.7 Hz)
• 1500 V AC (50 Hz)
• 1500 V DC
• 3000 V DC

Note: The leaflet guides the depot on which voltage to provide based on the visiting rolling stock (e.g., a German depot must provide 1000V 16.7Hz or a multi-voltage output for Swiss/Austrian cars).

2. The Connection Logic

Connecting 3000 Volts by hand is dangerous. UIC 554-2 mandates a strict sequence:

1. Plug Insertion: The cable is connected to the standard UIC socket on the coach end.
2. Pilot Contact: A shorter “Pilot Pin” in the plug closes a control loop. The shore post detects this continuity.
3. Energization: Only after the pilot loop is closed does the shore post turn on the High Voltage.
4. Immobilization: The presence of voltage on the external socket triggers a relay in the train that cuts the traction circuit, making it impossible for a driver to move the train and rip the cable out.

Comparison: UIC 554-2 vs. UIC 552

The difference between the source and the distribution.

Alternative: The 400V 3-Phase Feed

Some modern maintenance sheds do not want dangerous High Voltage (HV) train lines active inside. UIC 554-2 also acknowledges systems where a separate low-voltage plug (3x400V industrial connector) is used to feed only the battery charger and cleaning sockets, bypassing the main heating system. This is safer for cleaning crews but cannot heat the train.