Siemens NXPLUS Switchgear

NXPLUS switchgear is Siemens’ factory-assembled, type-tested, metal-enclosed, SF₆-insulated medium-voltage circuit-breaker switchgear line, offered as NXPLUS C for fixed-mounted, single- and double-busbar indoor applications up to 36 kV. This article explains the NXPLUS C product family, its construction principles, its published electrical ratings, typical industrial and utility applications, and the governing IEC/IEEE/CSA standards, for buyers sourcing gas-insulated MV switchgear across the Middle East and Gulf region (including Egypt and Saudi Arabia), North Africa, CIS countries, and Sub-Saharan Africa.

What Is NXPLUS Switchgear?

NXPLUS C is a hermetically sealed, gas-insulated switchgear system built around welded stainless-steel switchgear vessels that keep the busbars, cable terminations, and instrument transformers isolated from ambient air and mechanical damage. Because the primary circuit is protected inside a sealed SF₆ vessel, the design is described by Siemens as maintenance-free under normal indoor service conditions in accordance with IEC 62271-1. The switchgear vessel and the sealed pressure system are also designed to comply with the sealed-for-life provisions of IEC 62271-200.

The switchgear uses a three-position switch functioning simultaneously as busbar disconnector and feeder earthing switch, combined with a vacuum circuit-breaker that provides make-proof earthing capability. This arrangement, together with logical mechanical interlocking, is intended to prevent maloperation sequences such as closing an earthing switch onto a live busbar.

Types and Panel Variants

NXPLUS C is delivered as fixed-mounted circuit-breaker panels rather than withdrawable truck-type breakers, which simplifies the enclosure design while still allowing panel replacement without SF₆ gas work. The catalog structure covers:

• Single-busbar panels — the standard configuration for most substation and industrial feeder applications.
• Double-busbar panels — used where source/feeder transfer flexibility or n-1 busbar redundancy is required.
• Circuit-breaker panels in multiple widths — available in 450 mm, 600 mm, and 900 mm variants shown in the catalog, in addition to a 300 mm option.
• Air-insulated metering panel — used for block-type current and voltage transformers where dielectric stress considerations differ from the gas-insulated primary panels.
• Auxiliary transformer panel — houses a three-phase or single-phase dry-type transformer rated at 40 kVA or 10 kVA, with Dyn1, Dyn5, or Li0 connection symbols.

Both single- and double-busbar panel families are covered by dedicated panel-dimension and electrical-data sections in the manufacturer catalog, allowing engineers to align panel selection with substation layout and busbar architecture.

Selection Criteria for Buyers

When specifying NXPLUS-type gas-insulated switchgear, procurement and engineering teams typically evaluate the following criteria:

1. Rated voltage class. NXPLUS C covers a rated voltage range from 7.2 kV up to 36 kV, with an additional 38 kV rating listed for certain national requirements. Select the voltage class matching the incoming or distribution network level.

2. Short-circuit performance. Rated short-time withstand current and rated short-circuit breaking current values differ across the voltage range — buyers should match panel short-circuit ratings to prospective fault levels at the installation point, not just to nominal voltage.

3. Continuous current requirements. Busbar and feeder continuous-current ratings must be checked against expected load and future load growth, since feeder current ratings can differ from busbar current ratings at the higher end of the voltage range.

4. Enclosure protection and site environment. The standard degree of protection is IP65 for the high-voltage primary parts and IP3XD for the switchgear enclosure according to IEC 60529. This is relevant for sites with saline air, dust, humidity, or condensation risk, such as coastal, offshore, or desert installations.

5. Internal arc classification. Panels are tested for resistance to internal faults up to 31.5 kA, an important criterion for personnel safety compliance in enclosed switchrooms.

6. Circuit-breaker duty cycle. The vacuum circuit-breaker is rated for up to 10,000 operating cycles as standard, with an option extending this to up to 30,000 operating cycles for higher-duty applications.

7. Expected service life. Under normal service conditions the expected service life of the gas-insulated switchgear is at least 35 years, and potentially 40 to 50 years, limited mainly by the maximum number of switching-device operating cycles.

8. Environmental compliance. SF₆ has a documented Global Warming Potential of 24,300 according to IPCC AR6 GWP100 methodology, a figure buyers should weigh in sustainability procurement policies.

9. Standards and certification requirements. For projects requiring North American compliance, NXPLUS C switchgear conforms to IEEE STD C37.20.9 and is certified to CSA STD C22.2 No. 31, in addition to marine/offshore type approvals.

Electrical Ratings Table

The table below summarizes representative maximum electrical ratings across the NXPLUS C voltage range, as published in the manufacturer catalog.

The full catalog also lists intermediate voltage classes (15 kV, 17.5 kV, and 38 kV) with corresponding withstand and current values, and notes alternate national ratings of 32 kV/60 kV and 42 kV/75 kV for some markets.

Construction and Personnel Safety Features

NXPLUS C keeps all high-voltage parts — cable terminations, busbars, and voltage transformers — inside earthed, metal-enclosed compartments, which corresponds to the “metal-clad” classification under the former IEC 60298 standard. A capacitive voltage detecting system allows operators to verify safe isolation from supply before accessing compartments, and operating mechanisms plus auxiliary switches remain accessible from outside the sealed primary enclosure, so routine operation never requires opening the gas-filled vessel.

Instrument transformers are designed to minimize dielectric stress on current transformers, which are of the ring-core type and mounted outside the SF₆ vessel for straightforward replacement, while voltage transformers are metal-coated and plug-in for easy disconnection during maintenance work elsewhere in the panel.

Interlocking follows IEC 62271-200 principles: the three-position disconnector/earthing switch cannot select the READY-TO-EARTH function while in the DISCONNECTING position and vice versa, and the circuit-breaker can only be operated with the disconnector in its defined end position and the operating lever removed. Padlock-based locking options give additional operational control over which switching function is available at any given time.

Siemens reports that more than 500,000 switchgear panels of this general design family are in operation worldwide, supporting the long service-life expectation for the product line.

Digitalization and Condition Monitoring

NXPLUS C can be integrated with Siemens Xcelerator, an open digital platform aimed at grid stability management, cyber and asset security, CAPEX/OPEX optimization, and distributed energy resource integration. Condition monitoring functionality is positioned to extend the resilience and availability of the maintenance-free, gas-insulated switchgear over its expected multi-decade service life, referencing the design and empirical data basis defined under IEC 62271-1.

Secondary systems can include customary protection, measuring, and control equipment, or an optional numerical multifunction protection relay combining protection, control, communication, operating, and monitoring functions integrable into process control systems. Current and voltage sensing can also be implemented via inductive current transformers with precision shunts and resistor-divider voltage sensors, used in combination with devices such as SICAM FCM or 7SJ81 relays.

Applications

NXPLUS C fixed-mounted circuit-breaker switchgear is applied across a broad range of transformer and switching substations, including power supply companies, power stations, cement plants, automobile manufacturing, iron and steel works, rolling mills, mining operations, textile/paper/food processing, chemical and petroleum industries, pipeline installations, offshore platforms, electrochemical and petrochemical plants, shipbuilding, diesel and emergency power supply installations, lignite open-cast mines, and traction power supply systems.

The switchgear has also received type approval from classification societies DNV GL and the American Bureau of Shipping (ABS), making it suitable for marine and offshore platform applications where recognized class certification is a procurement requirement. This combination of industrial versatility and marine certification makes NXPLUS-type gas-insulated switchgear a relevant specification option for buyers across the Middle East and Gulf region (including Egypt and Saudi Arabia), North Africa, CIS countries, and Sub-Saharan Africa, where projects frequently span onshore industrial plants, offshore oil and gas platforms, and utility distribution networks with challenging ambient conditions.

Standards and Certifications

NXPLUS C switchgear design and testing references multiple IEC provisions relevant to gas-insulated MV switchgear:

• IEC 62271-1 — general requirements for high-voltage switchgear and controlgear, referenced for maintenance-free operation under normal service conditions.
• IEC 62271-200 — metal-enclosed switchgear standard, referenced for interlocking requirements and the sealed pressure system/sealed-for-life design.<!– 🔴 iddia: interlocks according to IEC 62271-200 and sealed pressure system design per IEC 62271-200 — kaynak Siemens NXPLUS Type MEDIUM-VOLTAGE SWITCHGEAR Fixed-Mounted Circuit-Bre

Related guides

See also our guides on ring main units, metal-clad switchgear and air-insulated switchgear.