Medium voltage switchgear (MV) type Rotoblok Air

New generation of Rotoblok Air switchgear

Rotoblok Air is a medium-voltage switchgear for up to 24 kV, which uses dry air insulation switches.

This is a response to the growing market demand for reducing the use of fluorinated gases in switchgear, while maintaining high reliability and operational safety.
Thanks to the modular design of the bays, Rotoblok Air allows for flexible configuration tailored to specific technical requirements. Each bay is an independent module, which facilitates the design, assembly and operation of the switchgear.

Switchgear is used in many industry sectors, from commercial power engineering and industry to municipal infrastructure. It is the ideal solution for facilities where reliability, safety and the ability to adapt the system to specific operating conditions are important.

Characteristics

General characteristics

The Rotoblok Air switchgear is a two-compartment indoor medium-voltage switchgear for up to 24 kV, made in air insulation (AIS – Air Insulated Switchgear), in a galvanised sheet metal enclosure, with a single busbar system. The switchgear design is based on clearly separated compartments: busbar and cable, which ensures clarity of layout and operational safety.

The switchgear uses modern solutions without the use of SF₆ gas. All switchgear is housed in hermetic stainless steel tanks, which ensures their durability, tightness and resistance to environmental influences. The insulating medium is dry air under overpressure, which is characterised by high dielectric strength and stable parameters throughout its entire service life. Depending on the configuration of the field, the switchgear may contain: a three-position disconnector-earthing switch equipped with a vacuum chamber system, a three-position disconnector-earthing switch or a vacuum circuit breaker.

Distribution boxes have the following properties:

reduced dimensions compared to switchgear with air-insulated devices while maintaining high electrical parameters such as insulation level, rated currents and short-circuit current resistance,
two-compartment field design ensuring separation of the main rail track from the part used to connect power cables,
high operational reliability,
long service life, without troublesome maintenance procedures,
high corrosion resistance, switchgear construction made of zinc-coated sheet metal,
versatility in implementing various switchgear systems, taking into account any number of fields,
use of modern, reliable switching equipment such as GT Air (ZPUE) disconnectors and isolators, and VCB Air (ZPUE) circuit breakers with isolators and earthing switches, or equipment from other manufacturers,
adapted for the installation of modern security and control equipment,
the possibility of wall-mounted installation of the switchgear, which allows for economical use of the switchgear room, which is particularly important in the modernisation and expansion of existing switchgear rooms,
easy and quick access to switchgear devices for supervision and maintenance,
simple operation.

Security and locking system

arc-resistant design – resistance to the effects of internal short circuits,
specially reinforced field construction (covers, locks, hinges),
mechanical locks preventing incorrect switching operations and preventing contact with live equipment,
access to devices and control circuits is provided without the possibility of touching parts of the main circuits,
use of control systems, signalling systems, mechanical and electrical position indicators and sight glasses,
use of three-position ‘on-off-earth’ disconnectors and isolators with mechanical position indicators,
use of fast-acting earth switches with a step drive, guaranteeing safety in the event of incorrect switching on a short circuit.

Standards

PN-EN62271-1 - „High-voltage switchgear and controlgear – Part 1: Common provisions”,
PN-EN 62271-200 - „High-voltage switchgear and controlgear – Part 200: AC switchgear in metal enclosures for rated voltages above 1 kV up to and including 52 kV”,
PN-EN 62271-100 - „High-voltage switchgear and controlgear – Part 100: High-voltage alternating current circuit breakers”,
PN-EN 62271-102 - „High-voltage switchgear and controlgear – Part 102: High-voltage AC disconnectors and earthing switches”,
PN-EN 62271-103 - „High-voltage switchgear and controlgear – Part 103: Disconnectors with a rated voltage exceeding 1 kV up to and including 52 kV”,
PN-EN 62271-105 - „High-voltage switchgear and controlgear – Part 105: AC fuse-switch assemblies”,
PN-EN 62271-213 - „High-voltage switchgear and controlgear – Part 213: Voltage detection and indication system”.

Basic electrical data

Rotoblok Air
Maximum voltage of devices	25 kV
Rated voltage	24 kV
Rated frequency / Number of phases	50 Hz / 3
Rated short-time withstand voltage at mains frequency	50 kV / 60 kV
Rated withstand lightning impulse voltage 1.2/50 μs	125 kV / 145 kV
Rated continuous current	630 A
Rated short-time withstand current	up to 20 kA (1s)
Rated peak current withstand	up to 50 kA
Resistance to internal bowing	16 kA (1s)
IP protection rating	IP4X

Operating conditions
Ambient temperature
- peak short-term	+ 40°C
- highest average over a 24-hour period	+ 35°C
- highest annual average	+ 20°C
- lowest long-term	- 25°C¹⁾
Relative air humidity
- highest average over a 24-hour period	95%
- highest average during the month	90%
- highest average vapour pressure during the day	2,2 kPa
- highest average vapour pressure during the month	1,8 kPa
Atmosphere at the installation site	no significant contamination with salt, vapours, dust, smoke, flammable or corrosive gases, and no icing, frosting or fogging
Installation height	up to 1000 m a.s.l. ²⁾
Vibrations	vibrations caused by external factors or earthquakes are negligible

Note!

¹⁾ Provided that the manufacturer of the control, measurement and safety equipment has not specified otherwise.
²⁾ Above 1,000 metres above sea level, the impact of reduced air density on the insulating properties of the switchgear must be taken into account. When installing at altitudes between 1000 and 3000 metres above sea level, a correction factor must be applied to reduce the values of the withstand impulse voltage and the withstand mains frequency voltage.

Transformer capacities that can be switched on and off by GT Air 2V disconnectors depending on the voltages on the MV side
Nominal mains voltage	Rated current	Max. transformer power
6 kV	77 A	800 kVA
10 kV	57,7 A	1000 kVA
15 kV	61,6 A	1600 kVA
20 kV	57,7 A	2000 kVA

For transformers with higher power ratings, please contact the manufacturer.
Rotoblok Air switchgear uses standard fuse links in accordance with IEC 282-1 and DIN 43625 standards with thermal protection.

Connecting devices

GT Air 1 - three-position disconnector with earthing switch,
GT Air 4 - three-position disconnector with earthing switch,
GT Air 2V - three-position switch with earthing switch and fuses,
VCB Air - multifunctional device with a built-in vacuum switch and a three-position disconnector with an earthing switch.

Method of constructing a cable duct under Rotoblok Air MV switchgear

Drawings No. 1 and 2 show a proposal for the construction of a cable duct under the switchgear. The depth of the duct for dry and oil-filled cables should be selected taking into account the minimum bending radius specified in the technical documentation for the cable type, depending on its external diameter. It is possible to reduce or completely avoid the need for a recessed duct by using a raised plinth or technical floor, which can be particularly useful in facilities with limited installation space.

If it is necessary to use fields with equipment not included in this study or with modified dimensions, the scope of equipment and installation requirements should be agreed with the manufacturer on a case-by-case basis to ensure proper structural and functional compatibility.

Fig. 1 Proposed cable duct design

Note! Minimum distance from the wall: 30 mm
¹⁾ Example fields with widths of 1000, 500, 500 mm (from left to right, respectively)
²⁾ Channel under the switchgear

Fig. 2 Proposed cable duct depth

Single-core dry cable
cable cross-section (mm²)	bending radius (mm)	channel depth k (mm)
50	370	400
70	400	430
95	440	470
120	470	500
150	500	550
185	540	600
240	590	700

Making cable connections in the Rotoblok Air switchgear

Line disconnectors and circuit breakers
Cable type	Cable head			Note
Cable type	Manufacturer	Typ	Cable cross-section [mm²]
Single-core plastic cable, e.g. YHAKXs, YHKX, XUHAKXs, XRUHKs, ...	Cellpack	CHE-I 24kV	25-240	Cable cross-section > 240 mm², more cables per phase, other types of cable heads consult the manufacturer.
		CAE-I 24kV	35-240
		CHESK-I 24kV	25-240
		CAESK-I 24kV	35-240
	Nexans (EUROMOLD)	ITK224	25-240
		AIP20	25-240
		AIS20	25-240
		AIN20	25-240
		24MONOi1	25-240
	TYCO ELECTRONIC	POLT-24D	25-240

Transformer fields
Single-core plastic cable, e.g. YHAKXs, YHKX, XUHAKXs, XRUHKs, ...	As in linear fields

Note!
In all cases, a cable duct is required under the switchgear. Optionally, the switchgear can be placed on a pedestal or on a technical floor.

Switchboard field variants

Side view

Stainless steel tank filled with dry air gas with switching apparatus
Drive compartment
Feedthrough insulators
Safety valve

Note!
The drawings shown on the following pages are only examples of field equipment. It is possible to adapt the field configuration to the specific requirements of the end user. In this case, please contact the manufacturer for drawings.

AL2 (line field)

Electrical diagram