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Author: K. C. Agrawal ISBN: 81-901642-5-2

Author: K. C. Agrawal isbn : Philosophy of quality systems 32 assurance 32 of testing 32 Recommended tests 32 tests 32 tests 32 disturbances 32 tests 32 Procedure for type tests 32 of insulation resistance or measurement of theleakage current 32 of dielectric properties 32 voltage withstand test 32 of temperature rise limits (or rated continuouscurrent capacity) 32 of short-circuit strength 32 of momentary peak or dynamic current 32 of protective circuits 32 of clearance and creepage distances 32 of degree of protection 32 Measurement of resistance and reactance 32 Endurance of trunking system with trolley-type tap-offfacilities 32 Safety measures new tests by IEC 32 EMC/EMI tests 32 Routine tests 32 Field tests 32/1098 Relevant Standards 32/109932 Testing a metal-enclosed bussystem32/1091 Author: K. C. Agrawal isbn : 81-901642-5-2 Author: K. C. Agrawal isbn : 81-901642-5-2 Testing a metal-enclosed bus system32/1093 Testing a bus system is generally along similar lines tothose for a switchgear assembly, discussed in Chapter14.

Author: K. C. Agrawal ISBN: 81-901642-5-2 Testing a metal-enclosed bus system32/1095 Table 32.1(a) For series I voltage systems: Insulation levels, power frequency and impulse withstand voltages for metal-enclosed bus systems Nominal system Rated max. system One-minute power frequency voltage withstand Standard lightning impulse,

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Transcription of Author: K. C. Agrawal ISBN: 81-901642-5-2

1 Author: K. C. Agrawal isbn : Philosophy of quality systems 32 assurance 32 of testing 32 Recommended tests 32 tests 32 tests 32 disturbances 32 tests 32 Procedure for type tests 32 of insulation resistance or measurement of theleakage current 32 of dielectric properties 32 voltage withstand test 32 of temperature rise limits (or rated continuouscurrent capacity) 32 of short-circuit strength 32 of momentary peak or dynamic current 32 of protective circuits 32 of clearance and creepage distances 32 of degree of protection 32 Measurement of resistance and reactance 32 Endurance of trunking system with trolley-type tap-offfacilities 32 Safety measures new tests by IEC 32 EMC/EMI tests 32 Routine tests 32 Field tests 32/1098 Relevant Standards 32/109932 Testing a metal-enclosed bussystem32/1091 Author: K. C. Agrawal isbn : 81-901642-5-2 Author: K. C. Agrawal isbn : 81-901642-5-2 Testing a metal-enclosed bus system32/1093 Testing a bus system is generally along similar lines tothose for a switchgear assembly, discussed in Chapter14.

2 In this chapter we discuss additional tests that arespecifically for a metal-enclosed bus Philosophy of quality systemsThis has been covered in Section Quality assuranceTo fulfil the quality requirements, the material inputsgoing into the making of a bus system must be properlychecked as soon as they are received, Aluminium or copper sections and sheets (for theircross-sectional areas, thickness of sheet, surface finish,bending properties and conductivity etc.) Hardware (for proper size, quality of threads and tensilestrength etc.) Insulators and supports (for sizes and quality ofmaterial) Other materials, components or equipment used formaking, inter-connections and bondings of suchsystems Cooling systems (in large current rating systems).All these items must be properly checked and recordedaccording to the manufacturer s internal quality checksand formats before they are used in the manufacture of abus system.

3 This will eliminate any inconsistency in amaterial or component at the initial stage. Similarly, stageinspections are necessary during the course ofmanufacturing to ensure quality at every stage and toeliminate incorrect construction and assembly or poorworkmanship. And thus assure a product of desiredspecifications and Purpose of testingThe purpose of testing of a bus system is to ensure itscompliance with design parameters, material inputs andmanufacturing Recommended testsThe following are the recommended tests that may becarried out on a completed bus duct, as in IEC 62271-200, ANSI C-37/20C, IEC 60694 and BS 159 for bothLV and HV Type testsType tests are conducted on the first assembly (bus system)of each voltage, current rating and fault level todemonstrate compliance with the electrical andconstructional design parameters. The tests provide astandard reference for any subsequent assembly withsimilar ratings and constructional details.

4 The followingtests are conducted:1 Verification of insulation resistance or measurementof the leakage current, both before and after thedielectric test (no longer a prescribed test but can beretained as an in-house screening test)2 Verification of dielectric properties:(i) Power frequency voltage withstand or HV test(ii) Impulse voltage withstand test for all LV andHV system voltages3 Verification of temperature rise limits (for ratedcontinuous current capacity)4 Verification of short-circuit strength:(a) For straight lengths and tap-offs(b) For the tap-offs in a power-generating station,connecting a UAT through the main bus sectionbetween the generator and the generatortransformer.(c) For the ground bus in isolated phase bus (IPB)systems5 Verification of momentary peak or dynamic current6 Verification of protective circuit7 Verification of clearance and creepage distances8 Verification of degree of protection:(a) Enclosure test(b) Watertightness test for all outdoor parts of anybus system (but for outdoor as well as indoorparts for isolated phase bus (IPB) systems)(c)Air leakage test, for isolated phase bus (IPB)systems9 Measurement of resistance and reactance10 Endurance of trunking system with trolley type tap-off facilitiesAs safety measures new tests added in the latest Standards,11 Verification of structural strength12 Verification of crushing resistance (force)13 Verification of resistance of the insulating materialsto abnormal heat14 Verification of resistance to flame propagation15 Verification of fire barriers in building penetration16 Electromagnetic compatibility (EMC) or immunitytest and electromagnetic interferences (EMI) oremission test on an IPB enclosure to satisfyelectromagnetic interference (EMI) requirements(Section ) for radio influence as in *NEMA-107.

5 The maximum radio influence voltage (RIV)should not exceed 100 mV at 1000 kHz. For testequipment and test procedure refer to the Routine testsRoutine tests are conducted on each completed bus system,irrespective of voltage, current, fault level andconstructional details and whether or not it has undergonetype tests. The following will form routine tests:1To check for any human error2 General inspection of the bus assembly3 Inspection of electrical wiring if there is any (such asfor space heaters, cold or hot air blowing, enclosurepressurizing or any other protective circuit)* NEMA National Environmental Management Act (South Africa).Author: K. C. Agrawal isbn : 81- 901642 -5-232/1094 Electrical Power Engineering Reference & Applications Handbook4 Verification of insulation resistance or measurementof the leakage current, both before and after thedielectric HV test. This test may be conducted onlyon partially type tested (PTT) bus systems5 Verification of dielectric properties similar to item2 under type tests6 Additional tests for an IPB system are:(a)Partial discharge test: On all cast resin componentssuch as instrument transformers, bushings andinsulators to ensure that the insulation is free fromdefects and voids.

6 (b)Checking of welded joints: as in GDCD-198, normsfor aluminium welding (CEGB, UK)*: All shop-welded joints will be subjected to dye penetrationexamination and 10% of butt-welded joints,including joints on flexibles, enclosures andconductors, will be subjected to radiographic (X-ray) Seismic disturbancesIn Section we have provided a brief account of suchdisturbances as well as the recommended tests andprocedures to verify the suitability of critical enclosuresand bus systems for locations that are this the user is required to provide the manufacturerwith the intensity of seismic effects at site of the installationin the form of response spectra (RS). (See Section ) Field testsThese are to be conducted after the installation and beforeenergizing the bus assembly at site:1 Checking for any human error2 Visual inspection of the bus assembly3 Inspection of electrical wiring if there is any (such asfor space heaters, cold or hot air blowing or enclosurepressurizing or any other protective circuit)4 Verification of insulation resistance or measurementof the leakage current, both before and after thedielectric HV test, if the HV test is to be carried of dielectric properties limited to powerfrequency voltage withstand or HV test (usually notrecommended)

7 6 Watertightness and air leakage test for isolated phasebus Procedure for type testsBelow we briefly outline the procedure for conductingtype tests at the manufacturer s Verification of insulation resistance ormeasurement of the leakage currentThe procedure and test requirements will remain the sameas that discussed in Section , for metal-enclosedswitchgear and controlgear Verification of dielectric propertiesPower frequency voltage withstand or HV testThe test voltage may be applied for one minute as shownin Tables (a) or (b) for series I and Table forseries II voltage systems. Any disruptive discharge orinsulation breakdown during the application of highvoltage will be considered to be dielectric tap-offs in a power-generating station connectinga UAT through the main bus section between the generatorand the generator transformer which are under thecumulative influence of two separate power sources, mustbe subjected to a higher withstand voltage as prescribedby IS 8084 and indicated in column 4, Table (a).

8 Impulse voltage withstand test(i)For LV systemIEC 60439-1 has now stipulated impulse voltagewithstand test for LV power as well as control andauxiliary circuits. Test procedures noted in and Tables (a and b) are applicable forbus systems also that are tested as per IEC Standards.(ii)For HV systemsThe procedure for testing will be the same as that discussedfor switchgear assemblies in Section The impulsetest voltage is applied as in Table (a) for series I andTable , for series II voltage systems with a full wavestandard lightning impulse of ms (Section ).There should be no disruptive discharge or Verification of temperature rise limits (orrated continuous current capacity)(Recommended for systems having a current rating ofmore than 400 A)This will be carried out under similar parameters ofroom condition and the type of test voltage wave to thosefor a switchgear assembly (Section ). The currentin each phase should be within 2% of the specified testvalue (rated current).

9 For LV bus systems: The length of the test piece willbe a minimum 6 m formed of two pieces of straightlengths as in IEC 60439-2 with at least two joints. Thejoints must be both in the conductor and in the enclosurein each phase. If the total length of the bus section is lessthan specified, the entire length of the bus system in thefully assembled form will then be HV bus systems: The entire length of the bus systemmanufactured for a particular installation in the fullyassembled form will be tested. Each end of the bus enclosurewill be properly sealed to eliminate any heat bus sample is located 600 mm above floor ambient temperature should be within 10 40 C asmeasured by the average value of at least four thermometers,two placed on each side of the enclosure on the centre line,at least 300 mm from it, and 600 mm from the ends. Thebus sample must be a three-phase unit as well as the testequipment for a three-phase system to account for theproximity effect.

10 This effect will not be reflected if a three-*CEGB Central Electricity Generating Board, : K. C. Agrawal isbn : 81-901642-5-2 Testing a metal-enclosed bus system32/1095 Table (a)For series I voltage systems: Insulation levels, power frequency and impulse withstand voltages for metal-enclosedbus systemsNominal systemRated max. systemOne-minute power frequency voltage withstandStandard lightning impulse,voltagevoltageat a frequency between 45 and 65 Hz for LV ms voltage withstandVrVm25 and 100 Hz for HV systems(phase to ground)12345 For a switchgearFor the tap-offs in a(a) We consider here onlyassembly and a buspower-generating station,List II, which is moresystemconnecting a UAT throughprevalent. For List I,(phase to ground)the main bus section betweenrefer to Table generator and the(b) For impulse voltagegenerator transformerwithstand across the contact(Figure ) (phase togaps of an interruptingground)device refer to IEC 60694*kV ( )kV ( )kV ( )kV ( )kV (peak) 952224505512533367075170 Based on IEC 60439-2 LV, IEC 60694 for HV and IS 8084 for tap-offs.


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