Zero-Sequence Overcurrent Relay Testing: 51N and 51G Inverse Curves
A 51N/51G test procedure: residual versus core-balance connection, pickup, curve and time multiplier, high-set element, and coordination with the upstream...
Read ArticleVA-TEK builds high-voltage test sets, relay protection test systems and transformer diagnostic instruments for utilities, cable contractors, service companies and testing laboratories. From substation commissioning to transformer condition assessment — we deliver the accuracy, reliability, and support your critical assets demand.
Specialized electrical test equipment engineered for power industry professionals.
Very low frequency AC hipot test sets from 30 kV to 90 kV peak for after-laying, acceptance and maintenance testing of shielded power cables, generator stators and motor windings. The TD models add tan-delta diagnostics.
View VLF Test Sets →Relay test sets for commissioning, maintenance, and troubleshooting of protection systems in conventional substations. 3-phase and 6-phase models available.
View Relay Testers →Portable and laboratory-grade current transformer and potential transformer testing equipment for ratio, polarity, excitation, and burden measurement. Complete CT/PT analysis in a single test set.
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VLF Cable Testing
VLF testing applies a 0.1 Hz sinusoidal AC voltage, so the capacitive charging current is a small fraction of what a 50/60 Hz hipot would draw. That lets a portable set withstand-test long, high-capacitance shielded cables — after laying, on acceptance, and in maintenance — with a voltage distribution that stays close to service conditions.
66 kV acceptance testing needs a higher VLF test voltage than this range provides — contact our engineers before selecting a set.
Technical Guide
Test voltages by cable class, test duration and frequency, sine vs cosine-rectangular waveforms, tan-delta interpretation — and how VLF compares with DC and DAC/OWTS. Built on IEEE 400.2-2024, IEC 60502-2, IEC 60229 and GB/T 3048.8.
Read the VLF Testing GuideFrom substation commissioning to transformer lifecycle management, our solutions cover the full spectrum of electrical testing needs.
Complete testing solutions for new substation deployment and retrofit projects.
From factory acceptance to periodic maintenance — test every transformer parameter across its entire service life.
Portable, rugged instruments for on-site commissioning and troubleshooting crews.
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Start from the test object. Each application page maps the protection scheme to the injection, pass criterion and recommended VAE model.
ATS/STS transfer, generator protection, main-tie-main and UPS bypass schemes.
Motor feeders, incoming supply, cogeneration, process transformers and capacitor banks.
Interconnection protection, anti-islanding, collector feeders, BESS and VLF cable testing.
Protection panel FAT: relay settings, CT/PT wiring, trip circuits, interlocking and documentation.
Expert articles on relay protection, cable and insulation testing, and transformer diagnostics.
A 51N/51G test procedure: residual versus core-balance connection, pickup, curve and time multiplier, high-set element, and coordination with the upstream...
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