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SOLVING EMC PROBLEMS IN THE DESIGN OF NEW HV TEST LABORATORY

Ivo Uglešić ; University of Zagreb, Faculty of Electrical Engineering and Computing Croatia
Miroslav Krepela ; EXOR d.o.o., Bani 73A 10010 Zagreb, Croatia
Viktor Milardić ; University of Zagreb, Faculty of Electrical Engineering and Computing Croatia

Sažetak

The paper deals with solving electromagnetic compatibility (EMC) problems in the design of a new,
case study, industrial high voltage test laboratory, intended to be used for testing of transformers and
other apparatus up to 550 kV rated voltage. Modern high voltage test facilities are equipped, apart
from primary test devices like AC, DC and impulse voltage generators etc., also with sophisticated
numerical measuring instruments and informatics technology. Since such devices are sensitive to
transient overvoltages, the highest degree of EMC is to be secured. This can be achieved by proper
earthing and screening of test laboratory, what shall be designed in a way to satisfy all requirements
conditioned by building lightning protection, personal protection and system earthing, avoiding
electromagnetic compatibility disturbances at the same time. One of the main tasks is solving
electromagnetic compatibility problems caused by outdoor electromagnetic disturbances originating
from various unknown sources. Those disturbances and interferences may seriously influence
measuring accuracy and readings of test devices, what consequently leads to false results. The stated is
especially relating to partial discharge measurements. As to avoid such disturbances, the laboratory
shall be completely screened with a net forming optimally designed Faraday cage. On the other hand,
at high voltage tests with impulse voltages, especially with chopped tail waves, steep transient
overvoltages may be generated. As a consequence, high transient potential differences between
particular points along the earth electrode may occur, what can even lead to flashovers between parts
of it. Therefore is of utmost importance to provide proper earthing and low inductance current return
path for impulse high voltage test equipment where high frequency transients are to be anticipated.
Improper earthing and bonding may result, apart from mentioned flashovers, in severe induced
voltages in secondary cables with consequential influence on test results, possible destruction of
measuring instruments and hazardous touch voltages for personnel. For analyzing transient potential
differences, it is important to model, with maximum accuracy, impulse test circuit (impulse generator,
chopping spark gap, voltage divider, Faraday cage, fundament earth electrode, earthing strips, earthing
rods etc.). Magnitude of transient potential difference between particular points is proportional to earth
electrode inductance, i.e. low inductance of earth electrode will result in decrease of transient potential
difference.

Ključne riječi

EMC - Earthing - Bonding - Transient - Disturbance - Testing - Measuring

Hrčak ID:

198418

URI

https://hrcak.srce.hr/198418

Datum izdavanja:

19.6.2017.

Posjeta: 555 *