The RKSTP-3.3/4000 three-post disconnector with polymer insulation, 3.3 kV, is designed for making and breaking, with no load, live but unloaded sections of the DC overhead contact line of electrified railways. When operated by a motor drive it can also interrupt, at the highest service voltage, currents of auxiliary machines of rolling stock, coach heating currents, and-under emergency conditions-back-feed currents of adjacent substations.
The RKSTP-3.3/4000 is manufactured for outdoor installation (placement category 1) in temperate/cold climates. Environmental categories are specified in EN/IEC 60721-3-4; operability is ensured under the following conditions:
- altitude up to 1000 m above sea level;
- upper working ambient temperature +40 °C;
- lower working ambient temperature -60 °C;
- no ice accretion with maximum wind pressure 1000 Pa (equivalent wind speed 40 m/s);
- with ice accretion up to 20 mm and wind pressure 140 Pa (equivalent wind speed 15 m/s).
The RKSTP-3.3/4000 provides mechanical robustness suited for outdoor OCL structures; vibration resistance corresponds to heavy-duty service for pole-mounted equipment.
Regarding thermal performance, the disconnector allows the following duty in terms of temperature rise:
- continuous current 4000 A with connection to eight copper conductors type M120 or eight aluminium conductors type A185 per GOST 839-80;
- cyclic overload duty with the same connections:
2 min – 6000 A
4 min – 5000 A
Operation is normally by a motor drive unit type PDM-G (UHL1). Interfacing to other drive types with technical parameters equivalent to PDM-G is permitted.

Technical data

Purpose and application

RKSTP-3.3/4000 is used in 3 kV DC traction power systems for operational sectioning of the overhead contact line (OCL) on open line, stations, traction substations and sectioning posts. The device provides a visible break and ensures safe creation of working zones when servicing pantograph and contact wires, catenary/messenger, return feeders, jumpers and take-offs. The three-post arrangement provides simultaneous action on all live parts of the section, which is important for by-pass schemes, backup switching and clearing faulted conditions.
With a motor drive the unit can be integrated into remote control and telemechanics/SCADA (DPR, ASDU) for fast restoration of normal supply, isolation of faulty sections and execution of switching programs without sending crews trackside. In manual mode the unit ensures reliable operation within local control schemes on OCL structures and in traction substation distribution yards. RKSTP is effective for:
- sectioning inter-substation and inter-feeder spans;
- creating neutral sections where high return currents occur;
- isolating areas for scheduled or emergency works;
- fast reconfiguration of yards, sidings and depot power schemes;
- establishing jumpers and by-passes in case of OCL damage or adjacent device outage.

Service conditions

The disconnector is intended for outdoor installation (placement category 1), including regions with temperate and cold climates. The design withstands long-term exposure to UV, precipitation, icing, wind loads and flying ice/snow typical for OCL structures and open-air distribution gear. Polymer post insulators are made of UV-, tracking- and weather-resistant material with a hydrophobic surface that promotes self-cleaning and maintains creepage distance in pollution. Operation is permitted in dusty areas, marine aerosol and railway de-icers provided the inspection/cleaning regimen is observed.
The unit resists vibration and shock from rolling stock and wind-induced mast sway, and temperature cycles from -60 °C to +40 °C. Base and fasteners have anti-corrosion protection; installation is possible on steel or reinforced-concrete poles, gantries and substation structures. A reliable earthing point is provided on the base, and a weather shield protects the open-gap zone from direct precipitation.

Design and construction

RKSTP-3.3/4000 is a vertical-break, three-post, polymer-insulated medium-voltage disconnector. Two fixed contact units and a moving blade form a visible break in the open position. To ensure dependable interruption of auxiliary-circuit currents, arcing contacts with defined make/break sequence relative to the main contact are used, reducing lamella erosion and extending life. The drive (motor or manual) transmits force via a linkage to the blade lever; fine adjustment of contact pressure, overlaps and clearances is provided. The contact zone is shielded from rain/snow, and current-carrying parts are shaped to reduce electrodynamic forces during impulse currents.
Contact surfaces are made of conductive alloys with wear-resistant coatings; spring elements maintain stable lamella pressure over temperature cycles and vibration. Overall dimensions and minimum open-gap provide the required dielectric strength. The design includes:
- earthing bolt on the base;
- terminals for multi-strand flexible conductors (Cu/Al) as per project specification;
- mounting points for limit switches/position sensors;
- adjustable stops ensuring repeatable end positions;
- convenient access for maintenance without removing the unit.

Safety and interlocking

The design provides a visible isolation gap, provisions for padlocks and mechanical interlocks in end positions, and dry-contact limit switches for remote “ON/OFF” indication. Points for sealing and handle/shaft locking are provided. Installation and operation shall follow applicable rules for operation of electrical installations. To prevent mal-operation, the disconnector can be equipped with kinematic interlocks with the drive and adjacent apparatus as per project. The base has a standard earthing bolt; terminals and live parts can be guarded/shielded to reduce accidental contact risk.

Variants and options

The disconnector can be supplied:
- with a motor drive (e.g., PDM-G UHL1) for remote control and SCADA integration;
- with a manual drive (e.g., PRZh-UHL1) for local pole-mounted control;
- with a set of limit switches / microswitches for telesignalling;
- with additional rain/snow shields, customized brackets for specific structures, and installation kits;
- with terminals for copper/aluminium flexible bars per project;
- with site-specific identification (tags, nameplates, labels).

Compliance with standards

The equipment and its use in overhead contact line systems comply with relevant international and European standards, including:
- EN/IEC 60721-3-4 - environmental conditions for stationary use at non-weather-protected locations (climate category for outdoor installation);
- EN 50119:2020 - Railway applications, fixed installations, electric traction overhead contact lines;
- EN/IEC 61992 (series) - Railway applications, fixed installations, DC switchgear (incl. outdoor d.c. disconnectors/switch-disconnectors/earthing switches);
- EN 50110-1 - Operation of electrical installations (safety of work procedures).
Where applicable, mechanical and environmental testing follows IEC 60068 methods.

Engagement with contractors, manufacturers and investors

We welcome co-operation with mechanical plants, electrical apparatus manufacturers, engineering firms and investors interested in launching the RKSTP-3.3/4000 and related OCL products. Possible co-operation models:
- licensing of design documentation with author support;
- supply of components and semi-finished parts with partner-side localization;
- split manufacturing by assemblies (mechanics, insulation, drives) with final assembly by the partner;
- turnkey tender participation with engineering support, supervision and staff training;
- product adaptation to requirements of national railways and local codes, including existing drive types, structures, brackets and telemechanics.

Documentation offered (drawings, 3D models, AutoCAD, SolidWorks, DXF, DWG, Parasolid)

On request we provide a complete design package for manufacturing and deployment of RKSTP-3.3/4000 disconnectors:
- preliminary documents for tenders and techno-commercial proposals (data sheets, diagrams, specifications, 3D views);
- working drawings, 3D models (Parasolid/STEP), DWG/DXF packages, CAM models, bills of materials;
- installation, adjustment, commissioning and operation manuals; test programs and procedures;
- passports, forms, quality control tables, lubrication charts and maintenance schedules;
- if required, adaptation of documents to your production capabilities and typical drives (including interlocking and signalling schemes).

Benefits of working with us

- No need to retain a large high-grade engineering staff - you receive a complete documentation set allowing manufacture by a mid-level engineer.
- No need to build costly prototypes - our experience allows direct launch of serial batches.
- Working to our documentation, your team will receive detailed guidance on all nuances of manufacturing RKSTP-3.3/4000 disconnectors.

For more information on RKSTP-3.3/4000 disconnectors contact: inbox@proekt-energo.com

…and, as is known, an error made at the design stage costs 10× at manufacturing and 100× in operation.

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