Voltage fluctuation test

Voltage Fluctuation Testing Service – Accredited ISO/IEC 17025 Electrical Quality and Immunity Assessment for the Croatian Market

Voltage fluctuation testing is a critical electrical performance evaluation method used to assess the ability of equipment, systems, and components to withstand and operate reliably under variations in the supply voltage. These variations, which include voltage dips, swells, short‑term interruptions, and continuous deviations from the nominal voltage, are common in power distribution networks and can cause malfunction, data loss, reduced performance, and premature failure of sensitive electronic and electrical equipment. Voltage fluctuation testing is essential for a wide range of products, including industrial control systems, consumer electronics, medical devices, automotive electronics, telecommunications equipment, and renewable energy systems. In the Croatian market, where the Hrvatski zavod za norme (HZN), the Ministarstvo gospodarstva i održivog razvoja, the Državni inspektorat, the Hrvatska regulatorna agencija za mrežne djelatnosti (HAKOM), and the Carinska uprava enforce strict quality, safety, and electromagnetic compatibility (EMC) standards aligned with EU directives and HRN EN (Croatian standards based on European norms), the accurate evaluation of voltage fluctuation immunity is essential for product certification, CE marking, supplier qualification, quality control in manufacturing, and import‑export processes. Our laboratory offers a comprehensive voltage fluctuation testing service, applying standardized methods such as IEC 61000‑4‑11, IEC 61000‑4‑14, IEC 61000‑4‑34, EN 50160, and HRN EN 50160 to simulate voltage fluctuations and evaluate the performance of the test item under controlled conditions. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Croatian authorities and notified bodies, making them indispensable for regulatory compliance, product validation, and market access in Croatia and the European Union.

Test Samples and Equipment We Regularly Examine

Our laboratory receives a wide variety of products, components, and systems for voltage fluctuation testing. Typical samples include:

• Industrial control and automation equipment – programmable logic controllers (PLCs), variable speed drives (VSDs), sensors, actuators, and industrial computers.
• Consumer electronics and household appliances – televisions, computers, power supplies, audio equipment, washing machines, and refrigerators.
• Medical devices and healthcare equipment – patient monitors, ventilators, infusion pumps, and diagnostic imaging systems.
• Automotive electronics – engine control units (ECUs), sensors, infotainment systems, and lighting control modules.
• Telecommunications and networking equipment – routers, switches, base stations, and power over Ethernet (PoE) devices.
• Renewable energy and power conversion equipment – solar inverters, battery storage systems, and uninterruptible power supplies (UPS).
• Prototype and new product designs – submitted by manufacturers for validation of voltage fluctuation immunity before series production.
• Field‑retrieved equipment – for failure analysis and remaining life assessment.

Voltage Dips and Short‑Term Interruptions Testing – Simulating Grid Disturbances

Voltage dips (also known as sags) and short‑term interruptions are the most common power quality disturbances. Our tests simulate these events and evaluate the ability of the equipment to ride through them without malfunction or damage. The test methods follow IEC 61000‑4‑11 and IEC 61000‑4‑34, which are harmonized with Croatian standards.

• Voltage dip test (IEC 61000‑4‑11 / HRN EN 61000‑4‑11 / NTC 5800 – for equipment with input current ≤ 16 A) – we connect the test item to a voltage dip generator (or a power source with dip simulation capability). The voltage is reduced from the nominal voltage (230 V, 50 Hz) to a specified test level (e.g., 0 %, 40 %, 70 %, or 80 % of the nominal voltage) for a specified duration (e.g., 10 ms, 100 ms, 500 ms, or 1000 ms). The test is performed at different phase angles (e.g., 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°) to simulate the worst‑case condition. The equipment is monitored for any malfunction, reset, or data loss. We report the test level, the duration, the phase angle, and the performance of the equipment (pass/fail).
• Short‑term interruption test (IEC 61000‑4‑11 / NTC 5801 – for power supply interruptions) – we reduce the voltage to 0 % of the nominal value for a specified duration (e.g., 10 ms, 50 ms, 100 ms, 250 ms, 500 ms, 1000 ms, or 5000 ms) and then restore the voltage. The equipment is monitored for the correct restart, the retention of data, and the absence of damage. We report the interruption duration and the equipment performance.
• Voltage dip test for equipment with higher current ratings (IEC 61000‑4‑34 / NTC 5802 – for equipment with input current > 16 A) – for industrial equipment with a higher current rating, we use the IEC 61000‑4‑34 method, which uses a different test setup (with a source impedance of 0.1 Ω or 0.2 Ω) and a slightly modified test profile. We report the test level, the duration, the phase angle, and the equipment performance.
• Voltage dip test at different voltage levels (NTC 5803 – for the test severity variation) – we perform the voltage dip test at different test levels (e.g., 0 %, 20 %, 40 %, 50 %, 70 %, 80 %) to evaluate the equipment's tolerance to different dip depths. We report the performance at each test level.
• Voltage dip test under different load conditions (NTC 5804 – for the effect of the equipment load) – we perform the voltage dip test with the equipment operating at no‑load, half‑load, and full‑load conditions, to evaluate the effect of the load on the immunity. We report the performance at each load condition.

Voltage Swell and Overvoltage Testing – Simulating Voltage Increases

Voltage swells (temporary increases in the voltage above the nominal value) can occur due to sudden load changes or faults in the network. Our tests simulate these events and evaluate the ability of the equipment to withstand overvoltage without damage. The test methods follow IEC 61000‑4‑11 and the relevant Croatian EMC standards.

• Voltage swell test (IEC 61000‑4‑11 / NTC 5810 – for overvoltage conditions) – we increase the voltage from the nominal value to a specified test level (e.g., 120 %, 140 %, or 160 % of the nominal voltage) for a specified duration (e.g., 10 ms, 100 ms, 500 ms, or 1000 ms). The test is performed at different phase angles. The equipment is monitored for any damage, overheating, or malfunction. We report the test level, the duration, the phase angle, and the equipment performance.
• Overvoltage withstand test (NTC 5811 – for the dielectric strength of the power supply) – we apply a voltage swell of 140 % of the nominal voltage for 500 ms and verify that the equipment's power supply (e.g., the input filter, the rectifier, and the capacitor) does not fail. We report the test level, the duration, and the equipment condition.
• Voltage swell at different phase angles (NTC 5812 – for the worst‑case phase angle) – we perform the voltage swell test at different phase angles (e.g., 0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°) to identify the phase angle that causes the highest stress on the equipment. We report the performance at each phase angle.
• Voltage swell test under different load conditions (NTC 5813 – for the effect of the equipment load) – we perform the voltage swell test with the equipment operating at different load levels, to evaluate the effect of the load on the overvoltage tolerance. We report the performance at each load condition.
• Combined voltage dip and swell test (NTC 5814 – for the sequential test) – we perform a sequence of voltage dips and swells (e.g., a dip to 40 % for 100 ms, followed by a swell to 120 % for 100 ms) to simulate a more realistic power quality disturbance profile. We report the performance during the combined test.

Voltage Variation and Fluctuation Testing – Simulating Slow Voltage Changes

Slow voltage variations (ranging from seconds to minutes) can occur due to load changes in the distribution network or due to the operation of voltage regulation equipment. Our tests simulate these variations and evaluate the stability and the performance of the equipment under continuous voltage changes. The test methods follow IEC 61000‑4‑14 and the Croatian EMC standards.

• Voltage variation test (IEC 61000‑4‑14 / HRN EN 61000‑4‑14 / NTC 5820 – for slow voltage changes) – we vary the supply voltage from the nominal value to a specified limit (e.g., 85 % to 110 % of the nominal voltage) at a specified rate (e.g., 1 % per second). The equipment is monitored for any malfunction, instability, or performance degradation. We report the voltage range, the rate of change, and the equipment performance.
• Voltage fluctuation test (NTC 5821 – for periodic voltage variations) – we apply a sinusoidal voltage variation (with an amplitude of ±5 % of the nominal voltage) at a specified frequency (e.g., 0.1 Hz, 0.5 Hz, 1 Hz) to simulate the effect of fluctuating loads (such as arc furnaces or motor starts). The equipment is monitored for any flicker, instability, or malfunction. We report the amplitude, the frequency, and the equipment performance.
• Voltage ramp test (NTC 5822 – for the gradual voltage change) – we apply a linear voltage ramp (from 0 % to 110 % of the nominal voltage, or from 110 % to 0 % of the nominal voltage) over a specified duration (e.g., 10 seconds, 60 seconds). The equipment is monitored for any malfunction during the start‑up or the shut‑down. We report the ramp rate and the equipment performance.
• Voltage variation with different load conditions (NTC 5823 – for the effect of the equipment load) – we perform the voltage variation test with the equipment operating at different load levels, to evaluate the effect of the load on the stability. We report the performance at each load condition.
• Flicker measurement (IEC 61000‑4‑15 / NTC 5824 – for the flicker severity) – for equipment that is sensitive to voltage fluctuations (such as lighting equipment), we measure the flicker severity (the short‑term flicker severity, Pst, and the long‑term flicker severity, Plt) using a flicker meter. We report the Pst and Plt values and the compliance with the EN 50160 limits.

Frequency Variation Testing – Simulating Grid Frequency Deviations

The grid frequency is normally maintained at 50 Hz, but it can vary (typically within ±1 Hz) under abnormal conditions. Our tests simulate these frequency variations and evaluate the performance of the equipment under off‑frequency operation. This is especially important for equipment with synchronous motors, clock circuits, or grid‑synchronized power converters.

• • Frequency variation test (IEC 61000‑4‑28 / HRN EN 61000‑4‑28 / NTC 5830 – for the frequency immunity) – we vary the supply frequency from the nominal value (50 Hz) to a specified limit (e.g., 47 Hz to 52 Hz) at a specified rate (e.g., 1 Hz/s). The equipment is monitored for any malfunction, loss of synchronization, or performance degradation. We report the frequency range, the rate of change, and the equipment performance.
  • Frequency step test (NTC 5831 – for the sudden frequency change) – we apply a sudden frequency step (e.g., from 50 Hz to 48 Hz, or from 50 Hz to 52 Hz) and monitor the equipment's response. The transient behavior and the settling time are measured. We report the frequency step, the response time, and the equipment performance.
  • Frequency ramp test (NTC 5832 – for the gradual frequency change) – we apply a linear frequency ramp (from 47 Hz to 52 Hz, or from 52 Hz to 47 Hz) over a specified duration (e.g., 60 seconds). The equipment is monitored for any malfunction during the frequency change. We report the ramp rate and the equipment performance.
  • Frequency variation under different load conditions (NTC 5833 – for the effect of the equipment load) – we perform the frequency variation test with the equipment operating at different load levels, to evaluate the effect of the load on the frequency tolerance. We report the performance at each load condition.
  • Frequency deviation and grid‑tied inverter test (NTC 5834 – for the renewable energy systems) – for grid‑tied inverters, we evaluate the response to a frequency deviation (e.g., a frequency rise above 50.2 Hz) to verify that the inverter trips (or reduces the output power) in accordance with the grid code. We report the frequency threshold and the inverter response.

Performance Monitoring and Data Analysis – Evaluating the Equipment's Functionality

During the voltage fluctuation tests, it is critical to monitor the equipment's functional performance in real time to detect any malfunction, reset, or degradation. Our data acquisition systems continuously record the supply voltage, the current, and the key functional parameters (e.g., the output voltage, the speed, the temperature, and the communication status) of the test item.

• Continuous voltage and current monitoring (NTC 5840 – for the power quality analysis) – we use a high‑speed power analyzer (with a sampling rate of > 10 kHz) to record the voltage and the current during the tests. The waveform, the RMS values, and the harmonic content are recorded. We report the power quality parameters and the voltage profile.
• Functional parameter monitoring (NTC 5841 – for the equipment's output and status) – we monitor the key functional parameters of the equipment (e.g., the motor speed, the temperature, the output voltage, the communication status, and the error flags) during the voltage fluctuation tests. Any deviation from the normal operating range is recorded. We report the functional parameter evolution and any anomalies.
• Data logging and event recording (NTC 5842 – for the failure detection) – we use a dedicated data logger to record the events (e.g., the occurrence of a reset, a shutdown, or an error message) and the time of the events. The event log is used to identify the failure mode. We report the event log and the failure analysis.
• Thermal monitoring (NTC 5843 – for the temperature rise during the test) – we use thermocouples or an infrared camera to monitor the temperature of the critical components (e.g., the power semiconductors, the transformers, and the capacitors) during the voltage fluctuation tests. An excessive temperature rise indicates a potential failure. We report the temperature profile and the maximum temperature.
• Post‑test functional verification (NTC 5844 – for the compliance check) – after the voltage fluctuation test series, we perform a full functional verification of the equipment (e.g., a performance test, a calibration check, or a safety test) to ensure that it has not suffered any permanent damage. We report the post‑test functional test results and the pass/fail status.

Test Report and Recognition in the Croatian Industrial, Commercial, and Energy Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (voltage dip generators, power analyzers, data loggers, and thermal cameras) and traceability to international standards (NIST, PTB). Our test reports are issued in English (with a Croatian summary available on request) and include:

• Full identification of the test item (manufacturer, model, serial number, power rating, and intended application).
• Detailed description of the test methods applied (IEC/HRN EN/NTC standards, test levels, durations, phase angles, and frequency ranges).
• Numerical results: voltage dip levels (%), interruption durations (ms), swell levels (%), frequency deviation (Hz), flicker severity (Pst and Plt), and functional performance (pass/fail).
• Graphical data: voltage vs. time curves, current vs. time curves, and functional parameter vs. time curves.
• Comparative tables against the values specified by the client or against the limits of the relevant standards (IEC 61000‑4‑11, IEC 61000‑4‑14, EN 50160, HRN EN 50160, and the requirements of the HZN, HAKOM, and Državni inspektorat).
• Event logs and failure analysis (if any).
• Photographs and thermal images of the test setup and the equipment.
• Recommendations for design improvement (e.g., the addition of a hold‑up capacitor, the improvement of the control loop, or the use of a wider‑input‑voltage power supply) to enhance the voltage fluctuation immunity.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98‑3 Guide.

These reports are fully accepted by the Hrvatski zavod za norme (HZN) for the verification of product conformity, by the Ministarstvo gospodarstva i održivog razvoja for industrial and energy compliance, by the Državni inspektorat for market surveillance, by the Hrvatska regulatorna agencija za mrežne djelatnosti (HAKOM) for telecommunications equipment, and by the Carinska uprava (Croatian Customs) for tariff classification and quality verification in the import of electrical and electronic equipment. Additionally, we offer consulting services for the design of power‑supply systems with high voltage fluctuation tolerance, the selection of appropriate power supplies, and the implementation of EMC and power quality improvement programs, contributing to the reliability, safety, and performance of electrical and electronic products in the diverse and growing Croatian market, from the industrial manufacturing and energy sectors to the commercial and consumer electronics industries.