MNS AC Low-Voltage Withdrawable Switchgear

Overview

MNS withdrawable switchgear is designed for power systems at 50/60 Hz and a rated operating voltage up to 660 V. It controls, protects and monitors equipment in generation, transmission, distribution and power conversion, and can act either as a power distribution centre (PC) or as a motor control centre (MCC).

Construction and technical advantages

• Fully modular design: the C-profile frame is made of aluminium-zinc coated or high-grade cold-rolled steel on a 25 mm basic module and is joined with self-tapping locking screws — no welding, high accuracy and rigidity.
• High space utilisation: one cubicle takes up to 36 quarter-module drawers, and more than 200 standardised assembly parts allow varied system layouts with degrees of protection from IP30 to IP54.
• Flame-retardant materials: high-strength engineering plastics with a V0 flammability rating raise the insulation level and the degree of protection against electric shock.
• Three-compartment segregation: functional-unit, busbar and cable compartments are fully separated by steel or high-strength flame-retardant barriers, preventing an arc fault from spreading.
• Interlocking: drawer units carry a mechanical interlock providing combined breaking, isolation and locking, so a drawer cannot be withdrawn while the circuit-breaker is closed.
• Interchangeability: functional units of the same rating are mechanically and electrically interchangeable, so a faulty unit can be swapped quickly; cables enter from above or below into a roomy cable compartment with standard supports.

Standardised production and service conditions

The design follows strict standardisation, commonality and series principles; assembly is simple and needs no special tools, which shortens site installation and lowers whole-life cost.

• Ambient temperature: between -5 °C and +40 °C (-25 °C in storage and transport), with a 24-hour average not above +35 °C.
• Altitude: not exceeding 2000 m; above 2000 m the assembly must be derated per GB/T 3859.1.
• Humidity: not above 50% at +40 °C; at lower temperatures (for example +20 °C) the daily average may reach 95% and the monthly average 90% — provide protection against condensation.
• Installation: tilt from the vertical not exceeding 5° and seismic intensity not above degree 9; avoid severe vibration and shock and corrosive gases or vapours.
• Special environments: state highly corrosive, heavily vibrating, dusty or outdoor conditions at the order stage so that special protection can be applied.