Technical articles
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ENP
Secondary Injection Testing of Protection Relays: Method, Criteria and Reporting
Secondary injection is the most common way to verify protection relays before energisation. We review the steps, curve formulae, tolerances and safety points.
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Comprehensive Substation Commissioning Checklist Before Energisation
Which checks and tests are required before energising a substation? A staged commissioning checklist from documentation and earthing to phasing, protection and handover.
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Testing Current and Voltage Transformers (CT and VT): Ratio, Polarity, Excitation Curve and Burden
CTs and VTs are the eyes and ears of the relay. A practical review of the required tests, accuracy classes such as 5P20 and PX, knee-point voltage and burden calculation.
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Testing Medium-Voltage Cables: Insulation Resistance, VLF, Partial Discharge and Tan Delta
Which test suits a new cable and which one an ageing cable? Comparing insulation resistance, VLF, partial discharge, tan delta and sheath tests, and how to run them safely.
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