EN 50163: Europe’s Blueprint for Rail Power Interoperability

Understanding EN 50163: Supply Voltages of Traction Systems

EN 50163 is a fundamental European standard that specifies the main characteristics of supply voltages for traction systems used in railway applications. Its primary purpose is to define the nominal voltages and their permissible ranges of variation at the terminals of the substation and at the pantograph of electric rolling stock. This standard is crucial for ensuring technical compatibility, safety, and interoperability across different railway networks.

By establishing a common framework for AC and DC traction power supplies, EN 50163 enables infrastructure managers and rolling stock manufacturers to design, build, and operate equipment that can function reliably and safely together. It addresses both the permanent voltages and the short-duration variations that can occur during normal operation, including events like regenerative braking.

Core Objectives and Principles of EN 50163

The standard is built upon several key objectives that are essential for the functioning of modern electrified railways. These goals ensure a harmonized approach to traction power, which is the lifeblood of the system.

• Interoperability: To allow trains to operate seamlessly across national borders and different network sections, the power supply characteristics must be standardized. EN 50163 provides this common language for voltage.
• Equipment Protection: By defining the highest and lowest voltage limits, the standard ensures that both onboard train equipment (inverters, motors) and trackside infrastructure (transformers, rectifiers) are protected from damaging over-voltages or under-voltages.
• System Performance: It guarantees a minimum voltage level at the pantograph, ensuring that a train has sufficient power to meet its designed performance specifications (e.g., acceleration and speed) under various load conditions.
• Safety: Standardized voltage levels and their limits are a cornerstone of the overall electrical safety concept for the railway system, protecting both personnel and equipment.

Key Technical Specifications of EN 50163

The technical depth of EN 50163 lies in its detailed classification of voltage levels and its recognition of different traction systems. It provides a precise and unambiguous set of parameters for engineers.

Standardized Traction Voltage Systems

EN 50163 defines the most commonly used traction supply systems in Europe and worldwide. These are categorized into Direct Current (DC) and Alternating Current (AC) systems:

• DC Systems: 1500 V (1.5 kV) and 3000 V (3 kV) are prevalent for urban, suburban, and some mainline routes. A lower 750 V DC system is also referenced, typically for trams and metros.
• AC Systems: 25 000 V (25 kV) at 50 Hz is the most common system for high-speed and modern mainlines. 15 000 V (15 kV) at 16.7 Hz is also widely used, particularly in Central Europe.

Voltage Classification and Limits

Perhaps the most critical aspect of the standard is its definition of voltage ranges. It specifies several key values to describe the acceptable voltage at the pantograph, which is the contact point between the train and the overhead line (catenary).

• U_n (Nominal Voltage): The reference value of the system (e.g., 25 kV AC).
• U_min1 (Lowest Permanent Voltage): The minimum voltage that can be present for an unlimited duration. The system must be designed to not fall below this level permanently.
• U_min2 (Lowest Non-Permanent Voltage): The absolute minimum voltage allowed, but only for very short durations (as defined in other standards like EN 50388). Operation below this level may lead to a traction shutdown.
• U_max1 (Highest Permanent Voltage): The maximum voltage that can be present for an unlimited duration. Equipment must be able to withstand this continuously.
• U_max2 (Highest Non-Permanent Voltage): The absolute maximum voltage allowed, typically occurring for short durations due to events like regenerative braking from multiple trains. Equipment must be insulated to withstand this peak without damage.

Regenerative Braking and Voltage Rises

Modern trains use regenerative braking, where the traction motors act as generators during braking, sending power back to the overhead line. If this generated power is not consumed by other nearby trains, it can cause the line voltage to rise significantly. EN 50163 defines the upper limits (U_max1 and U_max2) to account for these events, ensuring the system remains stable and equipment is not damaged by over-voltage.

Comparison Table of Standard Traction Supply Voltages

The following table summarizes the voltage limits at the pantograph as specified by EN 50163 for the most common mainline systems. These values are the design targets for both infrastructure and rolling stock.

Application and Significance in the Railway Industry

EN 50163 is not just a theoretical document; it has a direct and profound impact on the entire railway sector.

For Infrastructure Managers

Network operators use the standard to design and maintain their electrical infrastructure. This includes the spacing and power output of substations, the design of the overhead catenary system, and the configuration of protection systems to ensure the voltage at any point on the network stays within the specified U_min1 and U_max1 limits under normal conditions.

For Rolling Stock Manufacturers

Train builders rely on EN 50163 to design the electrical systems of locomotives, EMUs, and other electric vehicles. All onboard components, from the main transformer and power converters to auxiliary systems, must be designed to operate reliably across the entire voltage range from U_min2 to U_max2. This ensures the train can draw sufficient power to operate and can withstand the voltage fluctuations inherent in the system.

Conclusion

EN 50163 serves as a cornerstone for the electrification of railways. By providing a clear, detailed, and harmonized specification for traction supply voltages, it underpins the safety, reliability, and interoperability of the entire system. It creates a stable and predictable environment where infrastructure and rolling stock can work together effectively, enabling the efficient movement of passengers and freight across increasingly interconnected networks.