SURGE ARRESTERS SPECIFICATION FOR 132 KV & 33 KV LINE

Surge Arrester Specification

Surge Arrester Requirements for 132kV and 33kV Underground Cable Line Projects

 

Surge arresters shall be of the type employing non-linear metal oxide resistors without spark gaps. The Contractor shall demonstrate by calculations that the surge arresters will adequately protect the switchgear arrangement proposed.

Arresters shall be designed and tested in accordance with the requirements of IEC 99 4. Any departure shall be the subject of agreement between the Engineer and the Contractor. Routine tests shall be carried out in accordance with the requirements of Section 15 of this Specification.

Surge arresters shall be housed in porcelain insulators designed to withstand extremes of the environment described. The insulation shall have a minimum creepage distance of 25 mm/kV rated system phase-to-phase voltage. Porcelain shall comply with IEC 233. The method of sealing against the ingress of moisture shall be of a type well proven in service and the manufacturing procedures shall include a practical leak test which can be demonstrated to the inspecting engineer if required.

The internal components of arresters shall be arranged to minimize radial voltage stresses, and internal corona and to ensure minimal capacitive coupling with any conducting layer of pollutant on the outside of the porcelain housing except where approved, organic materials are not permitted.

Good electrical contact shall be maintained between resistor blocks, considering any thermal expansion and contraction of the block or mechanical shock during transport and erection, by installing a well-proven clamping system.

Metal oxide arresters installed outdoors shall be able to dissipate when new, twice the energy generated in the resistor blocks when energized at their maximum continuous operating voltage immediately having been subjected to the discharge duties specified in IEC 99 4 and assuming that the porcelain housing and the surrounding air is at least 5˚C higher than the maximum ambient air temperature specified.

Good quality control of the manufacturing process of the resistors shall be ensured by rigorous testing procedures. The procedures shall ensure that the characteristics of the blocks are, and will remain, within the specified limits when new and throughout the anticipated life of the arresters. Samples may be selected at random by the Engineer for special tests to be agreed upon with the manufacturer.

All surge arresters shall be fitted with a pressure relief diaphragm which shall prevent explosive shattering of the porcelain housing in the event of an arrester failure and the arrester shall have been tested according to the high and low current tests specified in IEC 99 1.

Arresters shall be supplied completely for installation in an outdoor switchyard, including supporting structures, insulating bases, and surge counters, one per phase, and, if applicable, grading rings. The material used for terminals shall be compatible with that of the conductors to which they are to be connected.

Each arrester shall be identified by a rating plate in accordance with the requirements of IEC 99 4. In addition, an identification mark shall be permanently inscribed on each separately housed unit of a multi-unit arrester so that units can be replaced in the correct position in the event of them being dismantled.

Surge counters shall have an internal assembly that is matched to the line discharge capability of the arrester and shall include a leakage current meter with a bilinear scale for ease of reading. Auxiliary contacts are to be provided to signal remote indications of the counter operation.

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Technical Data Schedule for 132 kV and 33 Surge Arrester

Sl. No.	Item no.	Unit	Nominal System Voltage
			132 kV	33 kV
1.	Manufacturer
2.	Model Number
3.	Type:
4.	Continuous operating voltage	kV RMS
5.	Rated voltage	kV RMS
6.	Standard nominal discharge current	kV
7.	Reference current at ambient temperature	mA
8.	Reference voltage for above	kV RMS
9.	Steep current impulse residual voltage	kV pk
10.	Lightning impulse residual voltage at
	5 kA	kV pk
	10 kA	kV pk
	20 kA	kV pk
11.	Duty Class
12.	Discharge Class
13.	Pressure relief class
14.	Nominal Diameter of resistor blocks	mm
15.	Number of resistor blocks connected electrically in parallel
16.	Number of separately housed units pre-phase
17.	Overall height of arrester (without supporting structure)	m
18.	Overall height of arrester including grading ring if applicable	mm
19.	Clearances:
	Phase to earth (from center line)	mm
	Phase to phase (center line to center line)	mm
20.	Overall height of arrester (without supporting structure)	kg
21.	Maximum cantilever strength	Nm
22.	Maximum force due to the wind (at maximum specified gust speed)	Nm
23.	Minimum creepage distance over the insulator	mm