Project Description
Electrical tests / measurements
RENEWABLE ENERGY PARKS – HIGH VOLTAGE SUBSTATIONS
Earth resistivity measurement
The measurement of the earth resistivity (IEEE Std. 81) constitutes the first and primary stage for the optimal design of a grounding system. This kind of measurement is conducted upon multiple axes on the ground surface and in multiple soil depths in order to approach the multilayer earth structure at the site of interest before the installation of grounding systems.
- Ground resistance measurement
The ground resistance measurement (IEEE Std. 81, ANSI IEEE Std. 80:2013, HD 637) is conducted after the full installation of a grounding system and, combined with the step and touch voltage measurements, indicates a sign of the grounding system efficiency. This particular measurement is usually necessary for receiving the functional certificate of the facilities and, in many cases, construction specifications and state-actors standards raise particular requirements for this resistance value.
- Step & touch voltage measurement
The measurement of step and touch voltages (IEEE Std. 81, HD 637) is conducted after completing the construction of the facilities and aims to ensure personnel safety. Both the step voltage values developed at the facility area and the touch voltage values near to accessible grounded metallic structures must not exceed specific safety limits defined by national standards and requirements.
CABLES – TRANSFORMERS
Dielectric strength under impulse voltage test on cables and transformers (20 kV – 1.4 ΜV)
This procedure includes type tests (Standards IEC 60502-2, IEC 60840, IEC 62067, BS 7870-4.10, BS 7870-4.20, BS 7835, BS 6622, SANS 1339) for testing the insulation strength against impulse voltages (1.2/50μs). The acceptance criterion is the non-perforation of the insulation upon the tested cable or transformer.
- Field testing of medium voltage shielded power cables using very low frequency (VLF) (40kV/0.1Hz)
VLF testing (Standards IEEE Std 400.2, ELOΤ HD 620, ELOT ΕΝ 60229) aims to note and confirm the successful field installation of the tested cable, so that the cable can be energized without any problems or restrictions. During the procedure:
a) the cable is tested for any mechanical stress during the installation which could cause degradation of the cable insulation and
b) the successful installation of the cable joints and terminations along its length are tested, so that the cable can be energized and serve according to the current specifications.
CRITICAL HOSPITAL AREAS
Measurement of resistance to earth
Measurement of resistance to earth, surface and vertical resistance (Standard ELOT ΕΝ 1081) of resilient floor coverings and installed floors in critical hospital areas (Surgeries, Intensive Care Units, CT / MRI etc.) for the safety of patients, doctors and nursing staff as well as for trouble-free functioning of equipment.
POWER TRANSMISSION LINES, SUBSTATIONS, HIGH VOLTAGE CENTERS
Measurement of low frequency magnetic and electric fields
Power transmission and distribution lines and all the types of the equipment of the ultra-high voltage centers, of the high voltage sub-stations and of the distribution centers of the electricity network are arrangements producing Extremely Low Frequency (ELF) electric and magnetic fields. The measurement of the electric and magnetic field intensity (Standards ELOT ΕΝ 61786-01, IEC 61786-2, ANSI IEEE Std. 644) in locations where there is human access to transmission lines and sub-stations of the electric network assures the compliance with the safety limits set by international organizations for the exposure of the public to such fields.
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