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Extra High Voltage Cables - EHV (145-400kv)

High Voltage Cables

When planning a new supply route, considerationof the environment is becoming more and moreimportant due to regulation and public opinion.The XLPE cables are environmentally friendlyand safe.The cable system is invisible.

The required right ofway is very small and normally after the installationthe land can be used again for its original purpose.This can result in considerable savingsReducing the electrical and magneticfields is also becoming moreimportant.

The cable systemcan be designed accordingto different magnetic fieldrequirements, and theexternal electrical fieldsare zero.Cable systems offerbettersafety to bothworkers and general public,with fewer dangeroussituations due to accidentalcontacts or flashovers.Reliability of the network is an importantactor because the loss of supply has high costconsequences. Cable systems are lessvulnerablefor failures compared to overhead lines.

High Standards

Partial discharges in the cable's insulation are regarded as one of the main reasons for electrical breakdown. Most recognized national and international standards permit discharges of 5 pC. However, our policy is not to allow deliveries of cables with any detectable discharges. Our new test set-up allows testing of up to 400 kV cables at a measuring sensitivity which is considerably better than the above requirement.

We are certified according to ISO 9001 Quality and ISO 14001 Environmental Management System standards for our activities.

Completely Dry Curing and Cooling

The insulation is kept absolutely dry during the whole manufacturing process. This prevents the electrochemical treeing during the whole lifetime of the cable. Our high voltage cables are equipped with a metallic moisture barrier protecting the insulation from subsoil humidity.

The conductor screen, insulation and insulation screen are extruded at the same time, i.e. triple extruded. Curing takes place in a vulcanizing tube pressurized by nitrogen gas. Besides fully dry curing, cooling in dry conditions is another important feature. It is achieved by using nitrogen gas.

The insulation does not come into contact with water in any form during the whole manufacturing process. It is a well-known fact that high voltage insulation should be kept moisture-free and research shows that this also applies to XLPE insulation.

Vertical CDCC-lineup to 420 kV
1	Conductor preheating	5	Process control Autocure 3
2	Clean room. Gravity feedingof insulation	6	X-ray wall thicknessmeasurement
3	On-line material puritycontrol	7	Post heater
4	Triple extrusionPost heater	8	On-line relaxation

Our production line has been equipped with the unique on-line relaxation system, giving benefits as:

• increased impulse voltage withstand
• reduced internal mechanical stresses
• minimized shrinkback behaviour

The on-line relaxation unit consists of an additional heating zone located in the middle of the cooling section of the vulcanizing line. Insulation surface is heated up and cooled down again. This treatment reduces significantly both internal mechanical stresses and shrinkback of XLPE insulation.

Two samples from the same cable and the same test run.The only difference between these samples is the use of relaxation.

Integrated optical fiber unit

Optical fibers in power cables can be used for measuring the actual temperature along the cable line or for data transmission. Fiber units are normally embedded under the lead sheath or between the screen wires. Temperature monitoring provides continuous monitoring of cable temperatures, detecting hot spots, delivering operational status, condition assessment and power circuit rating data. It is immune to electromagnetic interference and provides reliable temperature measurements, ideal for use in high voltage cables. Cables with optical fibers are denoted with letter ´F´, for example HXCHBMK-2F.

Standard Specifications

to any international or national standard.The two most common standard constructionsare described on page 6-7.

HXCHBMK / AHXCHBMK

Single core XLPE insulated powercable with copper wire screen andfoil laminate szsheath

HXCHBMK / AHXCHBMK
1	Conductor Longitudinally watertight segmental stranded and compacted copper or aluminium	6	Bedding Semiconducting waterblocking tapes
2	Binder tapes Semiconducting waterblocking tapes and bindertapes	7	Metallic screen A layer of copper wire helix and a copper contact tape counter helix
3	Conductor screen Extruded semiconducting copolymer compound	8	Separation tape Semiconducting waterblocking tapes and binder tapes
4	Insulation Extruded superclean XLPE compoundr	9	Radial water barrier Aluminium or copper foil laminate
5	Insulation screen Extruded semiconducting copolymer compound	10	Outer sheath Extruded PE or HFFR

HXLMK / AHXLMK

Single core XLPE insulatedpower cable with lead sheath

HXLMK / AHXLMK
1	Conductor Longitudinally watertight segmental stranded and compacted copper or aluminium	5	Insulation screen Extruded semiconducting copolymer compound
2	Binder tapes Semiconducting waterblocking tapes and binder tapes	6	Bedding Semiconducting waterblocking tapes
3	Conductor screen Extruded semiconducting copolymer compound	7	Metallic sheath Extruded lead, alloy E
4	Insulation Extruded superclean XLPE compound	8	Outer sheath Extruded PE, PVC or HFFR

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