Hermetic cable bushings (penetrations)

Hermetic cable bushings (HCB) also known as Hermetic cable penetrations / Sealed cable bushings / Sealed cable inlets are intended for the linking of different zones with an assurance of full mutual separation of specific environments. These bushings ensure a zone separation also in the case of both extreme effects (an overpressure, a flooding, an explosion etc.) and also in premises affected by radiation. They are used mainly in nuclear energetics where it is possible to monitor the tightness continuously, in premises protection  during floods or in cable ducts between the fire sectors of premises with an assurance of these premises with various pressure and thermic effects.

HCB ensure penetration seals of cable lines by pressure dividing lines and by pressure-proof and gas-proof engineering constructions. They can be used also for cables with metallic elements (power, HV, communication) and for optical cables as well.

Division of HCB

KABEX® 2002 M bushing is intented for a seal of pressure dividing lines for nuclear power plants (NPP). It is intedend for a seal of cabling passing through a containment building of the hermetic zone of a NPP.

Low voltage hermetic cable bushing (LVHCB) up to 1 kV: the bushing is composed by a body and separate modules, so called a module system:

-    1 modular HCB with a body diameter of 70 mm (LVHCB-DI – a bushing for diagnostic cables)
-    7 modular HCB with a body diameter of 168 mm
-    14 modular HCB with a body diameter of 325 mm

High voltage hermetic cable bushing (HVHCB) is intended for power circuits of high voltage with the values of operational, starting and short-circuit currents at a very high level:

-    for 1 conductor and for 3 conductors for a body with the diameter of 168 mm
-    for 3 conductors and for 4 conductors for a body with the diameter of 508 mm

Bushings for nuclear energetics
HCB from our production are intended for a cable duct through a hermetic zone boundary of a NPP and are constructed so that they maintain the hermeticity of a containment building, inhibit a radiation leakage and serve as firestops even in the case of project accidents. HCB from the production of Kabelovna Kabex® are labelled as HCB Kabex® 2002.

Main advantages of HCB Kabex® 2002:

Maintanance free and unification of HCB
HCB is constructed as a maintenance free equipment. For operation it is not necessary to maintain an operational overpressure inside the HCB. However, this can serve as monitoring information.
Kabex® solution is unified both for the type VVER 440 and VVER 1000. It means only one training and one process for both types of power plants. During certification the bushing was tasked with two LOCA profiles without interruption (first profile for VVER 400 overpassed to second profile of VVER 1000).  

Modern solution
HCB was constructed in the year 2000 ensuring the modernity of a solution and an avoidance of failures arising in the case of previous types of HCB.

Pressure monitoring
Kabex® HCB have double pressure monitoring. It is possible to monitor the pressure in a pressurized body and to monitor a pressurized space between a bushing body and a containment wall through a pressure gauge. It is an essential safety element because it is possible to find out the joint quality on a protective tiling at the beginning and all the time it is possible to monitor so far a „dead zone“.
During operation of HCB it is not neccessary to pressurize an inner space of the bushing body. It depends completely on an operator of a nuclear unit if he demands an overpressure in the HCB during operation.
Manometric system is intended for completing control tests (revisions) and for an overpressure monitoring if this operating mode requires different regulation. 

Cable tightness
Into its bushings Kabelovna Kabex® inserts axially tight certified cables that substantially support a hermeticity of the whole duct. This solution is patented by Kabelovna Kabex®.
Standardly, in the bushing on the cable core it is required to use a sealing lock by removing of a core insulation. However, this requirement is mistaken. In this case an insulation property of the bushing is substantially decreased in a very short period of time. This requirement has not been realized by Kabelovna Kabex®. The Kabex® solution rests on a high-pressure extrusion of insulation materials on a cable core. It is verified by the Nuclear Research Institute Řež plc. 

Multiple assurance of hermeticity
HCB Kabex® 2002 is constructed as a double-sided system of hermetic barriers with a middle space that is used mainly for monitoring or inspection of a hermeticity. Each system is constituted by three separate hermetic components that ensure a hermeticity separately in all the project modes of a run of a production unit of a NPP. A hermetic zone of a NPP is thus separated out from other spaces by six hermetic components.

Module seal
An embedding is implemented in the whole length with separation of a prime and a secondary part as prescribed by a norm.

Module placing
Single modules can be disassembled independently of each other only by unfastening of the nuts according to an immediate need without the need for disassembling other cable connections or of the whole HCB. This solution does not require any intervention into a containment wall. It means that an owner only defines which type (cable) out of seven cable assemblies he wants to change and Kabelovna Kabex® will supply the whole already sealed module ready for an immediate installment without a supplementary seal and without useless intervention into a bushing body. It is only inserted, tightened by a torque wrench and connected to an existing cabling through cable sets. The time required for realizing of the module replacement essentially decreases and therefore employees are spending shorter periods of time in a hermetic zone.

Level of biological protection
LOCA was developed on the basis of the measurement from NPP Dukovany (VVER 440) and NPP Temelín (VVER 1000). The Kabex® solution uses a combination of multiple materials  exceeding demands of all NPP operations with the possibility of expanding it for overproject status. The whole screening feature is intensified by a construction element – oblique module placement against “penetration” of neutrons.

Fire properties
Modules of HCB satisfy an insulation integrity of 180 minutes during fire according to IEC 60331 and a fire retardant property according to EN 50266-2-2 (IEC 60332-2-22). HCB ensure triple fire safety. Simultaneously, all the components satisfy a low level of corrosion and of smoke production according to IEC 60754 and IEC 61034-2.

Electrical characteristics and continuity of transmission parameters
The bushing is constructed to retain a continuity in the homogeneity of transmission parameters of the whole cable line, also from the perspective of EMC. A through cable, the transmission elements inside and performed connection respect a separation of all ground and screening potentials according to the strictest requirements of the norms. The construction when displacement of an insulation is not used for a seal ensures constant insulation statuses of the bushings in all operational modes.

Cables of various systems in one bushing
It is possible to install cables of various systems into one bushing body. Separation of circuits is ensured by a construction when each module is an individual bushing. The cable in the bushing is full-valued including all the screening layers. A module shell (corrosion-proof pipe) is another screening barrier.
HCB can vent to a connective box.

Triple fire safety
(specified for the class 1E according to IEEE 323)

1. constructional
- a separation of fire premises (sections)
- a fire resistance of HCB is minimally 90 minutes according to EN 1363-1 (EI 90)

2. the cables are fire retardant
- the supplied cables are from own production, there is ensured a fire retardant construction including conductors and connective sets

3. preservation of the insulation integrity of a circuit according to IEC 60331
Fire safety is verified already at the level of separate cables, in fact modules.

Packaging and expedition
Kabelovna Kabex® usually supplies HCB in standard plywood containers that ensure maximum product protection both during transport and during following storage.
HCB can be filled by nitrogen or an inert gas during the period of transport and storage.

High-voltage hermetic cable bushing (HVHCB)
HVHCB serve for power circuits of high voltage with values of operational, starting and short-circuit currents at a very high level:
for 1 conductor and for 3 conductors for the body with the diameter of 168 mm
for 3 conductors and for 4 conductors for the body with the diameter of 508 mm

HVHCB are constucted for a wall thickness of 400 – 3500 mm.
Partial discharges: maximum 10 pC/15kV.
According to a purchaser´s demand HVHCB can be supplied with a greater diameter of a bushing body (e.g. 25") or with different (non-circular) profiles of a bushing body (squared, rectangular etc.).

Operational voltage: 8/12 kV
Conductor cross-section: 25-1000 mm.
Bushing IP Code: IP68
HVHCB are constucted for maximum overpressure of 0,56 MPa.

Low-voltage hermetic cable bushing (LVHCB) up to 1 kV
LVHCB is composed by a body and separate modules (so called module system):

-       1 modular LVHCB with a body diameter of 70 mm (LVHCB-DI – the bushing for diagnostic cables)
-       7 modular LVHCB with a body diameter of 168 mm
-       14 modular LVHCB with a body diameter of 325 mm

Modular bushing

The bushing can be supplied by seven modules of various constructions. Our company offers these subgroups of modules:
KNC – the module is supplied by insulated Cu rods
KNK – the module is supplied by insulated Cu cores
KKK – the module is supplied by through cables (control)
KZM – the blind module

LVHCB are construed for a wall thickness of 400 – 3500 mm.
The diameter of a LVHCB body – 168 mm.
The diameter of a LVHCB-DI body – 70 mm.
Bushings with a connected cabling due cable sets of Kabelovna Kabex® are resistant to interfering – EMC according to the norms of EN 61000-4.
On the base of a customer´s demand the bushings can be supplied with a greater diameter (e.g. 25") or with different (non-circular) profiles of the bushing body (squared, rectangular etc.).
Kabelovna Kabex® produces axially tight certified cables into its bushings that significantly support the hermeticity of the whole duct. This solution is patented by Kabelovna Kabex®.


Operational voltage: 0,6 / 1 kV
Number of conductors in a module: 1 – 55
Number of pairs in a module: 1 – 19
Conductor cross-section: 0,5 – 254 mm2
The bushing IP Code: IP68
LVHCB are constructed for a maximum overpressure of 0,56 MPa.

LVHCB are usable for:

a)      power cables
b)      control and measuring cables
c)      pair cables
d)     coaxial cables
e)      extension conduct for thermocouples

Bushings for underground - KABEX® 2002 M

KABEX® 2002 M fully ensures fire separation of premises.
It is resistant to aggressive solutions (pH 4 – 11).
A cable comes through a dividing line without disconnection.
Bushing installation is realized on a device in operation.

Construction of the bushing KABEX® 2002 M is based on embedding of both sides of a cable duct  by a compound of polyurethan with a defined location.  Possible additional installation of a cable into already installed duct bedded by the bushing KABEX® 2002 M can be carried out when some openings are drilled into a polyurethan filler. The openings are filled again when the cable is put.

The bushings are set up also on dividing lines of escalator tunnels -  the KABEX® 2002 M bushing can be installed at any position, it can be used also on arc (eccentric) ducts.

Overpressure range:
- on a long-term basis: 0,6 MPa
- on a short-term basis (5 minutes): 1,1 MPa
- the bushing IP Code: IP68

The KABEX® 2002 M bushings are approved by the protocol of TŘ of Dopravní podnik hlavního města Prahy and have been installed into the Prague underground since 2003.