ABB UniGear ZS1, ZS2, UniGear 550 and UniSec Switchgear

Short answer

UniGear is ABB's family of air-insulated medium-voltage switchgear for primary distribution: UniGear ZS1 up to 24 kV and 63 kA, UniGear ZS2 and ZS3.2 up to 36 kV, and the compact UniGear 550 up to 17.5 kV. UniSec is ABB's range for secondary distribution and ZX2 the gas-insulated one. They are installed in distribution substations and industry.

What it is and where it is used

ABB UniGear ZS1 is ABB’s air-insulated metal-clad switchgear for primary distribution, and it is the reference of a family that includes UniGear ZS2, UniGear ZS3.2, UniGear 550 and UniGear Digital. For secondary distribution ABB offers UniSec, and for installations where space is the priority, gas-insulated switchgear such as ZX2. UniGear switchgear remains under ABB Electrification; it did not move to Hitachi Energy.

It is installed in distribution substations, heavy industry, mining, oil and gas, generation and data centers: transformer incomers, feeder outgoing circuits, bus ties, motors and capacitor banks. For the general principle, see medium-voltage switchgear.

Variants: UniGear ZS1, ZS2, ZS3.2, UniGear 550, UniGear Digital, UniSec and ZX2

Model	Application	Main difference
UniGear ZS1	Primary distribution	Up to 24 kV; the catalog consulted publishes up to 4,000 A and 50 kA, and ABB announces higher values in recent versions
UniGear ZS2	36 kV primary distribution	Up to 36 kV, 3,150 A and 31.5 kA for 3 s
UniGear ZS3.2	36 kV primary distribution	Up to 36 kV; 46 kV on request
UniGear 550	Compact primary distribution	Up to 17.5 kV, narrower width
UniGear Digital	Switchgear with sensors and IEC 61850	Current and voltage sensors instead of conventional instrument transformers
UniGear MCC	Motor control centers	Version for motor starters
UniSec	Secondary distribution	Modular air-insulated switchgear
ZX2	Gas primary distribution	Gas-insulated switchgear (GIS)

The values are those ABB publishes for each range. Installed switchgear may have lower values: those on its nameplate are the ones that count.

Main features

Withdrawable breaker, vacuum (for example, VD4) or SF6 (HD4), with service, test and disconnected positions. See ABB VD4 breaker.
Separate compartments for busbars, breaker, cables and low voltage, with internal arc classification according to IEC 62271-200.
Instrument transformers or sensors inside the switchgear, wired to the relay (Relion 615 and 620 are common).
Interlocks between breaker, truck, earthing switch and door. See withdrawable truck and switchgear interlocks.

Communications and integration

Communication is handled by the relay of each cubicle. In UniGear Digital ABB combines sensors and relays with IEC 61850, including GOOSE message exchange between cubicles for interlocking and logic selectivity. In conventional switchgear Modbus or DNP3 is also used. See ABB Relion 615 relay and IEC 61850 GOOSE.

UniGear ZS1 catalog data

The UniGear ZS1 catalog we consulted (2017 edition) defines it as primary distribution switchgear up to 24 kV, with single busbar, double busbar, back-to-back configuration or double level. The values it publishes are the following.

Rated voltage	7.2 kV	12 kV	17.5 kV	24 kV
Power-frequency withstand voltage, 1 min	20 kV	28 kV	38 kV	50 kV
Lightning impulse withstand voltage	60 kV	75 kV	95 kV	125 kV
Short-time current, 3 s	up to 50 kA	up to 50 kA	up to 50 kA	up to 31.5 kA
Peak current	up to 125 kA	up to 125 kA	up to 125 kA	up to 80 kA
Internal arc, 1 s	up to 50 kA	up to 50 kA	up to 50 kA	up to 31.5 kA
Busbar current	up to 4,000 A	up to 4,000 A	up to 4,000 A	up to 3,150 A

The breaker current reaches 3,150 A at 12 and 17.5 kV, and 2,500 A at 24 kV; with forced ventilation, ABB publishes up to 4,000 A at 12 and 17.5 kV and up to 3,150 A at 24 kV. In contactor switchgear, the rated current is 400 A. ABB’s current page publishes higher values than this catalog for recent versions, so the nameplate of each unit and the catalog from its purchase date are the ones that count.

Classification according to IEC 62271-200

Loss of service continuity LSC-2B: the busbar, breaker and cable compartments are physically and electrically separated, so the breaker compartment can be opened with busbars and cables energized. With a fixed switch-disconnector, the switchgear becomes LSC-2A.
Partition class PM: the partitions between compartments are metallic.
Access: the front is interlock-controlled access; the rear, tool-based. The switchgear does not require rear access for installation or for operating switching, which is done from the front.
Internal arc IAC AFLR: the catalog notes that, to specify it, four data points must be defined. They are the fault current level (from 16 to 50 kA), the duration (from 0.1 to 1 s), the escape paths for hot and toxic gases and the dimensions of the room, especially its height.

Active arc protection

ABB describes systems that trip the breaker when an arc is detected. These are the total times it publishes. Pressure sensors in the flaps (ITH) take 75 ms. The TVOC optical system takes 62 ms and the REA system 62.5 ms. The REF615, RET615, REM615 and REF610 relays with the optional arc module take 72 ms. In all cases, 60 ms corresponds to the breaker itself. There is also an ultra-fast earthing switch (UFES) that connects the three phases to ground in less than 4 ms after the arc is detected. For the principle of light-based detection, see arc flash protection by light detection.

Special applications

The catalog declares type tests according to IEC, GB/DL, GOST and CSA, and suitability for naval, seismic and nuclear use in specific versions. The VD4G breaker exists for generator switching, and the switchgear accepts a vacuum or SF6 breaker, vacuum contactor and switch-disconnector.

Frequently asked technical questions

UniSec documentation: catalogs and manuals are in ABB’s library; the switchboard dossier states the units and options delivered.
Which manual applies to the UniGear ZS1? there are separate instructions by version and by voltage; note the nameplate reference before searching.
UniGear Digital switchgear and testing: with sensors, the instrument transformer tests change; the sensors, the relay and the communication chain are verified.
Extending an existing switchboard: requires reviewing busbars, short-circuit ratings, internal arc and compatibility of the new cubicle.

How we help

We do not sell switchgear. At Tiza Group we test medium-voltage switchgear and breakers (timing, contact resistance, insulation, interlocks and instrument transformers), verify the protection and support commissioning, in substations and industry, in Colombia, or elsewhere on request. See circuit breaker testing under testing and commissioning. Write to us through the contact page.

References

IEC 62271-200, AC metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV.
IEC 62271-100, alternating-current circuit-breakers.
ABB, UniGear Portfolio page (ZS1, ZS2, ZS3.2, UniGear 550), UniGear Digital extension news item and pages on primary air-insulated switchgear.

Frequently asked questions

What is the difference between the UniGear ZS1 and the UniGear ZS2?

Both are ABB air-insulated metal-clad switchgear for primary distribution. ABB publishes the UniGear ZS1 up to 24 kV, with 4,000 A busbars and 63 kA short-time current, and the UniGear ZS2 up to 36 kV, with 3,150 A busbars and 31.5 kA for 3 s. Some regional ABB pages give different values by version, so the data for each installation is confirmed on its nameplate.

What is ABB UniSec switchgear?

It is ABB's range of switchgear for secondary distribution, air-insulated, with switch-disconnector, circuit breaker and metering units. It is used in customer substations, buildings, industry and distribution networks.

Where do I find the UniSec or UniGear manual or catalog?

In ABB's document library, where there are technical catalogs and installation, operation and maintenance instructions by version. For an installed switchboard, the controlling document is its dossier, with the drawings and options delivered.