PTS PTS - Personal Track Safety Working Near Electrified Lines 2 — Questions and Answers
Question 1: What is the standard voltage of the 25kV AC overhead line electrification (OLE) system used on many Network Rail main lines?
- 11,000 volts AC
- 25,000 volts AC (Correct answer)
- 750 volts DC
- 1,500 volts DC
Correct answer: 25,000 volts AC
The overhead line electrification (OLE) on Network Rail AC routes operates at 25,000 volts (25kV) AC, which is lethal at any distance without proper isolation.
Network Rail's overhead line electrification (OLE) system on AC routes operates at 25,000 volts (25kV) alternating current. This is approximately 100 times domestic mains voltage and is lethal on contact or at close proximity. An electrical arc can jump significant distances from OLE conductors, meaning workers do not need to touch the wire to be electrocuted. All workers on electrified lines must receive Line Blockage and OLE isolation training (or work under the authority of an Overhead Line Engineer). PTS training covers the hazards and basic precautions for working in the vicinity of OLE.
Question 2: What is the minimum clearance distance that PTS holders must maintain from an energised 25kV overhead line?
- 0.5 metres — equivalent to arm's length
- Workers must not approach within 600mm of energised OLE equipment — and in practice should remain further away as arc distance is greater (Correct answer)
- 2 metres at all times
- Contact is safe provided it is brief and the equipment has good insulation
Correct answer: Workers must not approach within 600mm of energised OLE equipment — and in practice should remain further away as arc distance is greater
PTS holders must maintain a minimum distance from energised OLE and must not approach within the danger zone without the OLE being isolated and earthed by a qualified Overhead Line Engineer.
Energised 25kV OLE presents an arc flash hazard — high-voltage electricity can jump through air to earth via a person's body before physical contact is made. The minimum approach distance (MAD) for untrained persons near 25kV OLE is 2 metres from any live conductor. PTS holders must not work near energised OLE without an Overhead Line Possession or appropriate isolation in place, managed by a qualified Overhead Line Engineer. If inadvertent approach is possible due to the nature of the work (e.g. erecting scaffolding), OLE isolation must be obtained first. PTS training emphasises treating all OLE as live unless proven otherwise.
Question 3: What must a COSS do when planning work that may bring workers or equipment close to the 750V DC third rail?
- Train workers to jump over the third rail quickly
- Obtain a third rail isolation for the relevant section, confirmed by a qualified Traction Electrical Engineer, before allowing any work where accidental contact is possible (Correct answer)
- Mark the third rail with warning cones and proceed
- Work is safe if tools are wooden
Correct answer: Obtain a third rail isolation for the relevant section, confirmed by a qualified Traction Electrical Engineer, before allowing any work where accidental contact is possible
A third rail isolation must be obtained from a qualified Traction Electrical Engineer before any work is planned that could result in accidental contact with the 750V DC third rail.
The 750V DC third rail electrification system used on southern and suburban Network Rail routes is live at all times unless specifically isolated. The third rail presents a contact electrocution risk — 750V DC can cause cardiac arrest and severe burns on contact. Before any work that could bring workers or equipment within reach of the third rail, the COSS must obtain a formal traction electrical isolation via a Traction Electrical Engineer. The isolation must be confirmed as in place and earthed before work begins. Workers must treat the third rail as live at all times unless an isolation has been confirmed. This is a fundamental PTS requirement on electrified DC routes.
Question 4: What should a PTS holder do if they see a colleague accidentally contact the 750V DC third rail?
- Grab the colleague to pull them away immediately
- Do NOT touch them — electrical current will pass through you too. Cut or isolate the power if possible, call 999, and call for emergency assistance using SPT (Correct answer)
- Pour water on the contact point to extinguish any fire
- Wait for the electricity to stop automatically before assisting
Correct answer: Do NOT touch them — electrical current will pass through you too. Cut or isolate the power if possible, call 999, and call for emergency assistance using SPT
Never touch someone in contact with live electricity — you will also be electrocuted. Isolate power if possible, call 999, and activate SPT to stop trains.
If a worker makes contact with a live third rail, attempting to grab them will cause the rescuer to also receive the electrical current — creating two casualties instead of one. The correct response is: DO NOT TOUCH the person; if there is a means to cut or isolate the power (e.g. emergency power cut-off button, trip switch) do so immediately; call 999 giving precise location; activate SPT to stop trains; keep others clear; only once power is confirmed isolated (by a qualified person) may physical first aid begin. Cardiopulmonary resuscitation (CPR) may be required once it is safe to approach. This response is covered in all railway electrical safety and PTS training.
Question 5: Why must conductive tools and equipment be kept a safe distance from the third rail even during approved track work?
- Conductive materials can damage the third rail surface, requiring expensive repairs
- Metal tools can complete an electrical circuit between the third rail and earth or adjacent rail, causing electrocution or equipment damage even when workers do not touch the rail directly (Correct answer)
- Health and Safety regulations prohibit metal tools near railways
- Conductive tools may interfere with train detection systems
Correct answer: Metal tools can complete an electrical circuit between the third rail and earth or adjacent rail, causing electrocution or equipment damage even when workers do not touch the rail directly
Conductive tools bridging the third rail to an earthed surface create an electrical circuit — workers holding the tool can be electrocuted even without directly touching the third rail.
The 750V DC third rail is energised at all times on live sections. If a metal tool (shovel, rail gauge, fishplate spanner) contacts the third rail while the worker holds it and their body provides an earth path (e.g. standing on wet ballast or touching the running rail), the worker will receive an electric shock. Even indirect contact via a conductive medium is dangerous. During track work near the third rail, tools must be handled carefully, insulated tools used where available, and the safest working position selected to prevent inadvertent tool contact. Traction isolation is the only fully safe approach for work directly adjacent to the third rail.
Question 6: What is an 'OLE possession' and what does it enable workers to do that they cannot do under normal conditions?
- An OLE possession is a speed restriction for trains under OLE structures
- An OLE possession formally isolates and earths overhead line equipment, allowing workers to work on or near the OLE without electrocution risk (Correct answer)
- An OLE possession is an asset ownership record for overhead line infrastructure
- An OLE possession is a training session for working near electrified lines
Correct answer: An OLE possession formally isolates and earths overhead line equipment, allowing workers to work on or near the OLE without electrocution risk
An OLE possession involves the formal isolation and earthing of overhead line equipment, enabling workers to work on or near OLE that would otherwise be lethal.
An OLE possession involves a sequence of formal actions: isolating the relevant OLE circuit at the supply point; confirming isolation with test instruments; applying earthing equipment to discharge residual charge and prevent re-energisation; and formally handing the isolated section to an Overhead Line Engineer (OLE). Only then can workers approved by the OLE work on or near the equipment. An OLE possession runs concurrently with a track possession to protect against train movements. When the OLE possession is surrendered, the section is re-energised and becomes lethal again. All workers in the area must be clear before re-energisation.
PTS PTS - Personal Track Safety Working Near Electrified Lines 2
What is the standard voltage of the 25kV AC overhead line electrification (OLE) system used on many Network Rail main lines?