Sheath Voltage Limiters | Ensto Varisil HC 4kV – 14.4kV Cable Sheaths

Sheath Voltage Limiters

Ensto Varisil HC are sheath voltage limiters suitable for 4kV – 14.4kV cable sheaths for connection to single point bonded sections dedicated to the protection of DC powered equipment in substations or on trains. HC surge arresters are designed for overvoltage protection of Power Transmission & Distribution underground cable sheaths.

The design of Ensto Varisil HC sheath voltage limiters are in accordance with CIGRE recommendations and IEC 60099-4 principles.

• Part Number : ENSTO 7250041
• Sheath Voltage Limiters SVL : ENSTO VARISIL HC
• Rated voltage Ur : 1 kV up to 18 kV
• Nominal discharge current : 10 kA
• High current impulse withstand : 65 kA
• Long duration current impulse withstand : 150 A
• High resistance to climatic stresses
• Optimized electrical performance
• Long creepage distance
• Maintenance-free Sheath Voltage Limiters SVL

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Varisil HC Sheath Voltage Limiter

Technical Specification

Temperatures

Max. operating temperature:	+70 °C
Ambient temperature :	-50°C to +50°C
Humidity:	100% at 25 °C (max)
Storage temperature:	-50 … +80 °C

 

Electrical Values

Operating voltage:	4 to 14,4kV
Rated discharge current:	10 kA
Dry lightning impulse withstand voltage:	≥ 95 kV
Wet power frequency withstand voltage:	≥ 35 kV

 

Mechanical

Tightening torque:	30 N.m
Max. continuous load:	1200 N
Highest permitted load in use:	1.5 kN

 

Ratings

Rated voltage:	5 … 18 kV
Degree of protection:	IP67
Rated frequency:	50-60Hz
Fire resistance class:	HL3-R23 / EN 45545-2

 

Short-circuit Characteristics

Rated short time withstand current:

31,5kA rms / 0,2

 

Sheath Voltage Limiters SVL Specification	HC05	HC10	HC12	HC15	HC18
Rated voltage Ur	5	10	12	15	18
Continuous operating voltage Uc	4	8	9.6	12	14.4
Nominal discharge current In (kA 8/20)	10	10	10	10	10
High current impulse withstand (kA 4/10)	65	65	65	65	65
Long duration current withstand (A 2000 µs)	150	150	150	150	150
Short circuit withstand (kA eff/0,2s)	31.5	31.5	31.5	31.5	31.5

 

Dimensions	HC05	HC10	HC12	HC15	HC18
Ho (mm)	195	195	195	195	195
H1 (mm)	255	255	255	255	255
H2 (mm)	290	290	290	290	290
Poids version NO (kg) Weight No version (kg)	1.4	1.6	1.7	1.8	1.9

1. Stainless steel top stud
2. Securing nut
3. Stainless steel top cap
4. Aluminium electrode
5. Metal oxide varistor
6. Synthetic tape
7. Composite wrappings
8. Silicone rubber housing
9. Stainless steel bottom cap
10. Stainless bottom stud

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Selecting the correct Sheath Voltage Limiter

The choice of the Sheath Voltage Limiters must be made according to the application :

• RNL HC range for the mounting in cabinets with cross bonding
• VARISI HC for mounting at ends of single point bonded sections

The selection of the appropriate Sheath Voltage Limiters within the range is based on two considerations having opposite impacts :

• The 1.2/50 lighting impulse withstand level of the sheath, which depends on the external insulation of the cable tends to minimize the required protective level
• The voltage induced at the connecting point of device in case of short circuit on the main conductor, which depends on the short circuit power and on the length of the cable to be protected, leads to maximize the rated voltage

A protective margin greater than 20% is recommended between the protective level of the surge arrester (Up) and the lightning impulse withstand level of the sheath (Uw).

On the other hand, the level/time values (Usc/T) of the voltage induced on the sheath in case of short circuit must be below the minimum voltage vs time characteristic curve of the surge arrester.

Whenever several references meet both requirements, the final choice will be made by the user with respect to operation requirements and priorities.

Basically, the surge arrester with lower rated voltage will provide improved protection whereas the surge arrester with higher rated voltage will better withstand short circuit stresses. Any surge arrester in-between will be a compromise.

Should no reference fulfil both requirements, the protection should be achieved at shorter intervals so as to allow the use of a surge arrester having a lower rated voltage.

Example : Cable features:

• Single point bonded cable
• Uw = 55 kV
• usc = 300 V/kA/km
• sc = 31.5 kA / T = 1 s
• L = 1.8 km

Selection of Sheath Voltage Limiter :

1. VARISIL™ HC
2. 20% protective margin : Up < Ut/1.2 thus Up < 46 kV
3. Voltage withstand under short circuit conditions : Ucs = usc x lcc x L = 17 kV and U (T = 1s) = 1.2 x Ur gives 1.2 x Ur > 17 so that Ur > 14.2 kV

Here, the calculation leads to Ensto VARISIL™ HC 15 model.

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 See also: Surge Diverters MV HV

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Electrical Safety Equipment for Low, Medium & High Voltage Cables & Power Systems

Thorne & Derrick are leading Specialist Distributors of Electrical Safety Equipment for working on Underground Cables and Overhead Lines at low, medium and high voltages – we are the largest UK stockist of CATU Electrical Safety Equipment & Products for working at LV, 600v 11kV, 33kV, 66kV, 132kV and up to EHV 400kV.

We provide electrical safety equipment to substation engineers, cable jointers, overhead linesmen and utility workers with PPE and electrical equipment including insulating gloves, voltage detectors, insulating matting and portable earthing to ensure worker safety when carrying out maintenance on LV-HV switchgear, substations, cables and electrical equipment – providing working protection during the pulling, jointing, termination and commissioning of medium/high voltage power systems.

Data Sheets

• Sheath Voltage Limiters Ensto Varisil HC 4kV – 14.4kV Cable Sheaths
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