Page 1008 - Industrial Power Engineering and Applications Handbook

Testing a metal-enclosed bus system 32/953
Testing a bus system is generally along similar lines to of the leakage current, both before and after the
those for a cwitchgear assembly, discussed in Chapter dielectric test
14. In this chapter we discuss additional tests that are 2 Verification of dielectric properties:
specifically for a metal-enclosed bus system. (i) Power frequency voltage withstand or HV test
(ii) Impulse voltage withstand test for system voltages
2.4 kV and above
32.1 Philosophy of quality systems 3 Verification of temperature rise limits (for rated
continuous current capacity)
This has been covercd in Section 11.1. 4 Verification of short-circuit strength:
(a) For straight lengths and tap-offs
32.1.1 Quality assurance (b) For the tap-offs in a power-generating station,
connecting a UAT through the main bus section
To fulfil the quality requirements, the material inputs between the generator and the generator
going into the making of a bus system must be properly transformer.
checked as soon as they are received, (c) For the ground bus in isolated phase bus (IPB)
systems
5 Verification of momentary peak or dynamic current
Aluminium or copper scctions and sheets (for their
cross-sectional areas. thickness of sheet, surface finish. 6 Verification of protective circuit
7 Verification of clearance and creepage distances
bending properties and conductivity etc.) 8 Verification of degree of protection:
Hardware (for proper size, quality of threads and tensile (a) Enclosure test
strength etc.) (b) Watertightness test - for all outdoor parts of any
Insulators and supports (for sizes and quality of material)
bus system (but for outdoor as well as indoor
Other materials, components or equipmcnt used for parts for isolated phase bus (IPB) systems)
making. inter-connections and bondings of such systems (c) Air leakage test, for isolated phase bus (IPB)
Cooling systems (in large current rating systems).
systems
9 Measurement of resistance and reactance
All these items must be properly checked and recorded IO Endurance of trunking system with trolley type tap-
according to the manufacturer’s internal quality checks off faci 1 i ties
and formats before they are used in the manufacture of a I I Additional test on an IPB enclosure for radio inter-
bus system. This will eliminate any inconsistency in a ference as in NEMA-107. The maximum radio
material or component at the initial stage. Similarly, stage influence voltage (RIV) should not exceed 100 pV at
inspections are necessary during the course of manu- 1000 kHz. For test equipment and test procedure refer
facturing to ensure quality at every stage and to eliminate to the Standard.
incorrect construction and assembly or poor workmanship.
And thus assure a product of desired specifications and 32.2.2 Routine tests
quality.
Routine tests are conducted on each completed bus system,
32.1.2 Purpose of testing irrespective of voltage, current, fault level and con-
structional details and whether or not it has undergone
The purpose of testing of a bus system is to ensure its type tests. The following will form routine tests:
compliance with design parameters, material inputs and
manufacturing consistency. To check for any human error
General inspection of the bus assembly
32.2 Recommended tests Inspection of electrical wiring if there is any (such as
for space heaters, cold or hot air blowing, enclosure
pressurizing or any other protective circuit)
The following are the recommended tests that may be Verification of insulation resistance or measurement
carried out on a completed bus duct, as in IEC 60298, of the leakage current, both before and after the
ANSI C-37/20C. IEC 60694 and BS 159 for both LT and dielectric HV test
HT systems. Verification of dielectric properties - limited to power
frequency voltage withstand test or HV test
32.2.1 Type tests Additional tests for an IPB system are:
(a) Partial discharge test: On all cast resin components
Type tests are conducted on the first assembly (bus system) such as instrument transformers, bushings and
of each voltage, current rating and fault level to demon- insulators to ensure that the insulation is free from
strate compliance with the electrical and constructional defects and voids.
design parameters. The tests provide a standard reference (b) Checking of welded joints: as in GDCD-198. norms
for any subsequent assembly with similar ratings and for aluminium welding (CEGB. UK)*: All shop-
constructional detailh. The following tests are conducted:
1 Verification of insulation resistance or measurement *Central Electricity Generating Board. U K