Electrification of Prague line 140

The electrification of bus line 140 in Prague is one of the unique pilot projects of the future. It aims to bring trolleybus lines back to Prague after 50 years.  In total, the Prague Public Transport Company is preparing the electrification of 11 bus lines to replace diesel buses and make public transport in Prague more environmentally friendly and sustainable.

NKT has supplied an innovative type of 3-AHKCY cable with HEPR type cross-linked insulation material, which due to its properties enables higher current carrying capacity of the cables compared to traditional types of 3 kV cables.

One of the main reasons for the electrification of additional bus lines is primarily to meet the City's Climate Commitment, which aims to reduce CO₂ emissions by 45% by 2030 compared to 2010. The transport company must also comply with European and national legislation, which specifies a mandatory share of low-emission or locally emission-free vehicles in the fleet of carriers, and the related need to ensure the continuous renewal of the bus fleet with locally emission-free vehicles. The intention to electrify additional bus lines contributes to ensuring the energy security of the capital city of Prague and the Czech Republic by reducing dependence on fossil fuels supplied from countries with low levels of democracy and human rights protection, DPP says.

Just as the Prague City Transport Company is modernising the transport network with a positive impact on the environment, NKT's mission is to connect a greener world.

A greener, healthier and safer world for us and the next generation is a priority for NKT, which is why we are delighted to have been able to supply AHKCY cables for this project, developed by us, which meet safety standards and which support our shared environmental vision.

The main advantage of the AHKCY cable over conventional AYKCY is its better insulation properties due to the use of HEPR (Hard Grade Ethylene Propylene Rubber) material for the core insulation. Increased current carrying capacity and longer life are its other advantages.

In the past, only cables of type 3-AYKCY with PVC insulation system were produced, which NKT replaced with a cable with insulation made of the aforementioned HEPR material.

As such, the insulation resistance is strongly temperature dependent. If some routes have to be shut down, other routes are overloaded and the temperature of the conductors rises significantly. This factor was the reason for changing the insulation system in the first place.

Based on these facts, NKT has developed a completely new type of cable, 3-AHKCY, with an insulating cross-linked material of the HEPR type, which, thanks to its properties, allows the operating temperature of the cores to be raised to 90°C and thus the current carrying capacity of the cables to be increased. The temperature dependence of its dielectric properties is much more favourable than that of PVC and exceeds the required minimum insulation resistance of 5 MΩ.km by several orders of magnitude.

In terms of production, the increase in the price of the insulating material is compensated by the simplification of the cable construction.

Environmental aspects were also taken into account when developing the new cable type. The materials used for the production of 3-AHKCY cables according to TP-NKT-01/07 have changed very significantly compared to the original construction of 3-AYKCY cables. The PVC contained in the cable has been eliminated. The HEPR material is halogen-free, with less environmental impact.

NKT is a major global supplier of customized cable solutions to a variety of industries, and public transport is no exception. NKT also supplies cables for the Prague metro, for example, and has references on a wide range of other transport projects.

(Photo by Honza Tran.)