UniGear ZS1 metal clad switchgear is ABB’s mainline air-insulated medium-voltage switchgear platform, built for primary power distribution up to 24 kV with metal partitions segregating internal compartments and air-insulated live parts. This article covers the platform’s design, apparatus options, electrical ratings, applicable standards, and selection guidance for buyers in the Middle East and Gulf region including Egypt and Saudi Arabia, North Africa, CIS markets, and Sub-Saharan Africa, where UniGear ZS1 is widely specified for utility, industrial, and marine electrification projects.
What Is UniGear ZS1 Metal Clad Switchgear?
UniGear ZS1 is manufactured worldwide and forms part of ABB’s global distribution solutions portfolio, with a very large installed base and a manufacturing footprint spanning multiple continents. The switchgear has been installed in more than 100 countries, reflecting its status as a well-established global product line.
Each UniGear ZS1 panel is built as a single functional unit that can house a circuit-breaker, a contactor, or a switch-disconnector, along with the accessories typically expected in conventional switchgear units. A defining operational feature is that installation, operation, and maintenance are performed entirely from the front of the unit, with no rear access required — a practical advantage in installations built back-to-wall or in space-constrained rooms.
Panel Architecture and Compartmentation
Internally, each switchgear unit is divided into three power compartments — circuit-breaker, busbars, and cables — plus a separate low-voltage compartment that houses auxiliary instruments. These compartments are segregated from one another by metallic partitions, consistent with the platform’s Partition Metallic (PM) classification.
The main busbar system, made of copper with a flat cross-section, connects to the upper isolating contacts of the circuit-breaker through branch connections; higher-current variants use an open D-shaped busbar cross-section instead. Busbars and branch conductors rated at the higher voltage classes are insulated using shrink-on sleeves, and bolted connections are covered with insulating covers for additional protection. The cable compartment houses flat electrolytic-copper connections to the lower contacts of the circuit-breaker, and can be fitted with an earthing switch for cable earthing.
Arc-proof designs are typically equipped with a duct for evacuating gases generated by an internal arc event.
Types and Configuration Variants
UniGear ZS1 is offered in several busbar and space arrangements to match project layout and continuity requirements:
- Single busbar — the standard configuration, combinable with other units in the UniGear family.
- Double busbar system — for applications requiring source or bus redundancy.
- Back-to-back arrangement — for efficient use of switchroom floor area.
- Double-level design — a compact solution that stacks functional units to reduce footprint.
- A 500 mm wide panel option is also part of the ZS1 24 kV third-generation family, aimed at further reducing switchroom width.
On the apparatus side, ABB offers what is described as one of the most complete ranges on the market for this platform:
- Withdrawable vacuum circuit-breakers with mechanical or magnetic actuator.
- Withdrawable gas (SF6) circuit-breakers.
- Withdrawable vacuum contactors with fuses (ConVac).
- Fixed switch-disconnector units.
This shared apparatus platform allows the same switchgear-user interface and the same operating and maintenance procedures across a project regardless of which apparatus type is fitted. Additional design features include protection and control units, standard and ultra-fast earthing switches, IS-limiter fault-current limitation devices, integrated capacitor banks, and bay control and protection units.
Electrical Characteristics
The table below summarizes the rated electrical characteristics across the UniGear ZS1 voltage classes.
| Parameter | 7.2 kV | 12 kV | 17.5 kV | 24 kV |
|---|---|---|---|---|
| Rated insulation voltage | 7.2 kV | 12 kV | 17.5 kV | 24 kV |
| Rated power frequency withstand voltage (1 min) | 20 kV | 28 kV | 38 kV | 50 kV |
| Rated lightning impulse withstand voltage | 60 kV | 75 kV | 95 kV | 125 kV |
| Rated frequency | 50/60 Hz | 50/60 Hz | 50/60 Hz | 50/60 Hz |
| Rated short-time withstand current (3 s) | up to 50 kA | up to 50 kA | up to 50 kA | up to 31.5 kA |
| Rated short-time withstand current (1 s) | 63 kA | 63 kA | 63 kA | — |
| Peak withstand current | up to 164 kA | up to 164 kA | up to 164 kA | up to 80 kA |
| Internal arc withstand current (1 s) | up to 50 kA | up to 50 kA | up to 50 kA | up to 31.5 kA |
| Main busbar rated current | up to 4000 A | up to 4000 A | up to 4000 A | up to 3150 A |
Circuit-breaker rated current steps offered across the range include 630 A, 1250 A, 1600 A, 2000 A, 2500 A, and 3150 A, with forced-ventilation variants extending up to 3600 A and 4000 A on the lower voltage classes. Panels equipped with a contactor are rated at 400 A. A GB/DL variant is available with enhanced dielectric performance up to 42 kV and extended short-time withstand duration. A CSA-compliant version is available up to 27.6 kV.
LSC and Partition Classification (IEC 62271-200)
Under IEC 62271-200, switchgear is classified by Loss of Service Continuity (LSC) and partition type rather than by the older metal-enclosed/compartmented/cubicle categories. The most common UniGear ZS1 panel classification is LSC2B, PM — meaning the cable compartment, adjacent functional units, and main busbars can remain energized while a main-circuit compartment on one unit is opened for maintenance, with metallic partitions (PM) separating live compartments.
Front access to high-voltage compartments is interlock-controlled, while rear-side compartments (not intended for normal operation) are tool-based access only, requiring special procedures. Depending on panel type — incoming/outgoing, bus-tie, riser, measurement, contactor, or switch-disconnector units — the assigned LSC category ranges from LSC1 to LSC2B across the different rated-current and short-circuit variants.
Safety and Internal Arc Performance
UniGear ZS1 functional units are guaranteed arc-proof in accordance with IEC 62271-200, Appendix AA, class A accessibility criteria 1 to 5. The switchgear carries the internal arc classification IAC AFLR, and both the switchgear and its earthing switches are operated from the front with the door closed. When specifying arc-fault protection for a project, fault current levels of 16 to 63 kA and fault durations of 0.1 to 1 second must be considered, along with gas-evacuation escape routes and room dimensions.
Standard ingress protection is IP4X for the outer enclosure and IP2X for internal compartment partitions, with higher degrees of protection available on request. Circuit-breaker racking is performed with the door closed, and other safety interlocks are built into the design.
Environmental and Site Conditions
Rated characteristics are guaranteed within an ambient temperature range of −5 °C to +40 °C. Humidity limits are specified as a maximum 24-hour average relative humidity of 95% RH and a maximum monthly average of 90% RH, with corresponding water vapour pressure limits of 2.2 kPa (24h) and 1.8 kPa (monthly). Normal operating altitude is up to 1000 metres above sea level, with higher altitudes requiring consultation with ABB.<!– 🔴 idd
Related guides
See also our guides on gas-insulated switchgear, ring main units and air-insulated switchgear.
What is Unigear ZS1 Metal Clad Switchgear?
Unigear ZS1 Metal Clad Switchgear is a medium-voltage solution; see the definition and feature sections above for full detail.
What should I consider when selecting unigear zs1 metal clad switchgear?
Key factors include the rated voltage class, rated current, short-circuit withstand, installation environment and the applicable standards, all discussed above.
Where is unigear zs1 metal clad switchgear typically used?
Typical applications include utility, industrial and infrastructure medium-voltage distribution, as covered in the applications section.
Looking for Unigear ZS1 Metal Clad Switchgear?
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