RND-35 series visible-break, center-break air-break switches (disconnectors) are intended for operational switching of de-energized 35/36 kV circuits and for earthing/grounding isolated sections when supplied with integrated earthing switches. The kinematics is a horizontal-rotary, center-break design: one or two rotating post insulators turn 90° to produce a clearly visible isolation gap and stable, high contact pressure. Each pole uses a double-column scheme: the blades (moving knives) are mounted on the upper flanges of the post insulators; the separable (female) contact is protected by a hood for reliable operation under icing. Inter-pole synchronization is via adjustable tie-rods; the leading pole connects to the operating mechanism, followers are linked via inter-pole rods. The contact system employs laminated finger contacts with spring pressure, flexible copper braids, and adjustable rods with angle scales for field alignment. Mechanical interlocks “main circuit/earthing switch” are provided, plus auxiliary limit switches for remote status indication “CLOSED/OPEN/EARTHED”.

RND-35 units are supplied in single-, two-, and three-pole configurations. Environmental/service conditions: outdoor AIS application per IEC 62271-1 normal/special service conditions; the equipment is engineered for ambient -60…+40 °C, altitude ≤ 1000 m, wind and icing as specified below (temperatures beyond IEC “normal” are treated as special service conditions by agreement). Standard mechanisms include manual PR-2B and PRG, and a motor-operated PD-14 with remote control and dry contacts. Insulators can be porcelain station-post (IEC) or polymeric/composite with extended creepage distance for polluted/coastal sites. Corrosion protection: hot-dip galvanizing of steel structures and protective finishes on current-carrying interfaces. Typical external conditions: altitude ≤ 1000 m; ambient -60…+40 °C; radial ice up to 10 mm; wind ≤ 40 m/s (no ice) or ≤ 15 m/s (with ice). Permissible terminal mechanical tension from connected conductors up to 500/780 N depending on current rating. Mechanical endurance meets/exceeds the requirements typically applied to IEC 62271-102 disconnectors in the 36/40.5 kV class. In North America, the device corresponds to a visible-break, center-break air-break switch per IEEE nomenclature.

International notes for specifiers: In IEC practice, rated voltage 36 kV (Um = 40.5 kV) aligns with the parameters below; “3-s thermal withstand current” corresponds to I_th(3 s) and “peak dynamic withstand” to I_peak. Selection of external insulation/creepage follows IEC/TS 60815 (pollution levels). For US projects, ratings/application shall be coordinated to IEEE C37.30.1 (and associated guides), in addition to IEC 62271-1/-102.

Technical Data

Explanatory notes: values follow common 36 kV practice per IEC 62271 series. The 3-second thermal withstand applies to short-circuit duty without damage; the peak dynamic value refers to first half-cycle electromagnetic forces. Earthing switch short-time rating (1 s) is for intentional grounding under fault conditions. Terminal mechanical limits consider wind/ice loading and shall be coordinated with conductor tension/span.

Application and Intended Use

RND-35 is an outdoor, line-type disconnector for AIS 35/36 kV switchyards (incoming feeders, line bays, bus section and transfer bus positions, bypass circuits, taps and sectionalizing points, and disconnection of shunt reactors/capacitor banks per local operating rules). The visible isolation gap provides an unambiguous point of isolation for safe work under permit-to-work procedures. With integrated earthing switches (RNDZ variants), crews can establish equipotential earthing without portable grounds.

The mechanical design is optimized for frequent, short-duration operations, withstands electrodynamic forces during short-circuit events, and allows straightforward SCADA/DCS integration via auxiliary limit switches and dry contacts. Important: like all IEC/IEEE disconnectors/air-break switches, RND-35 is not intended to make or break load current; switching of negligible charging or magnetizing current shall follow owner procedures and surge-control measures.

Layout and Construction Features

Each pole is a channel-section steel frame with rotating post insulators on bearing supports, shafts and cranks. Blades are copper bars with laminated, spring-loaded finger contacts; terminals accept strap/tube bus with flexible copper braids. Separable contacts are hooded to shed ice/contamination; OPEN/CLOSED positions are positively defined by stops/latches. Inter-pole rods are field-adjustable, with angle scales on cranks for phase alignment.

Interlocking prevents closing the main circuit with an earthing switch engaged and vice versa. Drive parts can be sealed and fitted with padlocks or captive-key (Castell/Kirk-type) interlocks on request. Joints use long-life lubricants; the maintenance program covers visual checks, torqueing of bolted joints, and insulator cleaning per site pollution level. Steelwork is hot-dip galvanized; current paths use tinned/silvered interfaces as specified.

Types and Configurations (Nomenclature)

Compatible Operating Mechanisms & Kinematics

Safety and Interlocking

Mutual mechanical interlocks exclude simultaneous closing of the main circuit and the earthing switches. A visible-break isolation gap, designated bonding points for protective conductors, and auxiliary limit switches for “CLOSED/OPEN/EARTHED” indication comply with IEC 62271-102 and IEC 62271-1. For North-American practice, interlocking and ratings coordination follow IEEE C37.30.1 (air-break switches).

Versions and Options

• Polarity: single-, two-, or three-pole sets; mechanism mounted left/right of the leading pole.
• Earthing: none (RND) / single-sided (RNDZ.1a/1b/1) / double-sided (RNDZ.2).
• Current ratings: 1000; 2000; 3150 A*; reinforced blades and terminals for high short-circuit duty.
• Insulation: porcelain station-post or polymer/composite with extended creepage sized to IEC/TS 60815 pollution level.
• Sensors/signaling: additional limit switches and microswitches; custom cable glands and terminal plans.
• Other: adapter frames/plates to replace legacy devices without changing bus elevations.

International options: galvanized coatings per ISO 1461, stainless steel fasteners for C5-M atmospheres, surge-arrester brackets, mechanism cubicle heaters (where applicable), and wiring to terminal blocks per IEC/UL practices.

Standards Compliance

• IEC 62271-102:2018 (A.C. disconnectors and earthing switches; EU adoption e.g. BS EN IEC 62271-102:2018+A1:2022).
• IEC 62271-1:2017 + A1:2021 (Common specifications for H.V. switchgear and controlgear).
• IEC/TS 60815-1/-2/-3 (Selection and dimensioning of external insulation & creepage for polluted conditions).
• IEC 60060-1 (High-voltage test techniques - general definitions and test requirements) - dielectric testing philosophy.
• IEEE C37.30.1-2022 (U.S.: Requirements for A.C. high-voltage air switches rated above 1 kV; supersedes older C37.32, C37.34, C37.35).

Note: Where IEC and IEEE practices are both applicable, ratings nomenclature and test sequences are aligned case-by-case during project specification (e.g., I_th(3 s), I_peak, dielectric test levels, pollution class and creepage).

Operational Advantages

• Stable contact pressure and reliable operation under icing thanks to hooded separable contacts and spring-pressed laminated fingers.
• Adjustable kinematics and inter-pole rods enable rapid on-site alignment and commissioning.
• Broad compatibility with common operating mechanisms and SCADA/DCS (dry contacts and limit switches).
• Porcelain or polymer insulation with creepage sized to site pollution level per IEC/TS 60815.

Additional benefits: robust hot-dip galvanized steelwork for long-term corrosion resistance, straightforward visual confirmation of isolation, and simple maintenance (periodic inspection, torque checks, insulator cleaning) that reduces lifecycle cost in AIS yards.

Documentation and Supply

We provide technical proposals and complete manufacturing documentation for series production of RND-35/RNDZ-35: schematics, bills of materials, 3D models (STEP/Parasolid), drawings (*.dwg/*.dxf), process sheets, assembly and adjustment instructions. Deliverables can be adapted to your tooling, bus elevations, and preferred mechanisms/insulators. On request: FAT procedures, routine test reports per IEC 62271-1, signal I/O lists for SCADA integration, and site installation checklists.

RND-35 FAQ (Questions & Answers)

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