299.435 Electrical system design.§ 299.435 Electrical system design.
(a) Overhead collector systems. (1) Pantographs shall be so arranged that they can be operated from the driver's normal position in the cab. Pantographs that automatically rise when released shall have an automatic locking device to secure them in the down position.
(2) Each overhead collector system, including the pantograph, shall be equipped with a means to electrically ground any uninsulated parts to prevent the risk of electrical shock when working on the system.
(3) Means shall be provided to permit the driver to determine that the pantograph is in its lowest position, and for securing the pantograph if necessary, without the need to mount the roof of the trainset.
(4) Each trainset equipped with a pantograph operating on an overhead collection system shall also be equipped with a means to safely lower the pantograph in the event of an emergency. If an emergency pole is used for this purpose, that part of the pole which can be safely handled shall be marked to so indicate. This pole shall be protected from moisture and damage when not in use. Means of securement and electrical isolation of a damaged pantograph, when it cannot be performed automatically, shall be addressed in the railroad's operating rules.
(b) Circuit protection. (1) Each auxiliary circuit shall be provided with a circuit breaker or equivalent current-limiting devices located as near as practicable to the point of connection to the source of power for that circuit. Such protection may be omitted from circuits controlling safety-critical devices.
(2) The 25-kV main power line shall be protected with a lightning arrestor, automatic circuit breaker, and overload relay. The lightning arrestor shall be run by the most direct path possible to ground with a connection to ground of not less than No. 6 AWG. These overload protection devices shall be housed in an enclosure designed specifically for that purpose with the arc chute vented directly to outside air.
(3) Auxiliary power supply (440 VAC), providing power distribution, shall be provided with both overload and ground fault protection.
(c) Main battery system. (1) The main batteries shall be isolated from the cab and passenger seating areas by a non-combustible barrier.
(2) If batteries have the potential to vent explosive gases, the batteries shall be adequately ventilated to prevent accumulation of explosive concentrations of these gases.
(3) Battery chargers shall be designed to protect against overcharging.
(4) Battery circuits shall include an emergency battery cut-off switch to completely disconnect the energy stored in the batteries from the load.
(d) Capacitors for high-energy storage. (1) Capacitors, if provided, shall be isolated from the cab and passenger seating areas by a non-combustible barrier.
(2) Capacitors shall be designed to protect against overcharging and overheating.
(e) Electromagnetic interference (EMI) and electromagnetic compatibility (EMC). (1) The railroad shall ensure electromagnetic compatibility of the safety-critical equipment systems with their environment. Electromagnetic compatibility can be achieved through equipment design or changes to the operating environment.
(2) The electronic equipment shall not produce electrical noise that interferes with trainline control and communications or with wayside signaling systems.
(3) To contain electromagnetic interference emissions, suppression of transients shall be at the source wherever possible.
(4) Electrical and electronic systems of equipment shall be capable of operation in the presence of external electromagnetic noise sources.
(5) All electronic equipment shall be self-protected from damage or improper operation, or both, due to high voltage transients and long-term over-voltage or under-voltage conditions. This includes protection from both power frequency and harmonic effects as well as protection from radio frequency signals into the microwave frequency range.
(f) Insulation or grounding of metal parts. All unguarded noncurrent-carrying metal parts subject to becoming charged shall be grounded or thoroughly insulated.
(g) High voltage markings: doors, cover plates, or barriers. External surfaces of all doors, cover plates, or barriers providing direct access to high voltage equipment shall be conspicuously and legibly marked “DANGER-HIGH VOLTAGE” or with the word “DANGER” and the normal voltage carried by the parts so protected. Labels shall be retro-reflective.
(h) Hand-operated switches. All hand-operated switches carrying currents with a potential of more than 150 volts that may be operated while under load shall be covered and shall be operative from the outside of the cover. Means shall be provided to show whether the switches are open or closed. Switches that should not be operated while under load shall be conspicuously and legibly marked with the words “must not be operated under load” and the voltage carried.
(i) Conductors; jumpers; cable connections. (1) Conductor sizes shall be selected on the basis of current-carrying capacity, mechanical strength, temperature, flexibility requirements, and maximum allowable voltage drop. Current-carrying capacity shall be derated for grouping and for operating temperature.
(2) Jumpers and cable connections between trainset units shall be located and guarded to provide sufficient vertical clearance. They may not hang with one end free.
(3) Cable and jumper connections between trainset units may not have any of the following conditions:
(i) Broken or badly chafed insulation;
(ii) Broken plugs, receptacles, terminals, or trainline pins; and
(iii) Broken or protruding strands of wire.
(j) Traction motors. All traction motors shall be in proper working order, or safely cut-out.