DEMIKS has developed Automated temperature rise test systems that allow for continuous primary current injection up to 10,000A. These systems are engineered to perform under the most stringent thermal loading conditions. Heavy-duty oil-immersed induction voltage regulators and multi-channel 4-wire Pt100 thermal logging provide verified compliance to IEC 62271-1, IEC 61439-1, and IEC 60947-1, without issues like carbon brush wear or electromagnetic noise drift.
Temperature rise testing is the final thermal qualification test for power transmission and distribution equipment. High-voltage gas-insulated switchgear (GIS) equipment, medium-voltage air-insulated switchgear (AIS) equipment, low-voltage switchboard assemblies, busbar trunking systems and power transformers must carry their rated normal currents continuously without exceeding standard temperature rise limits. During the testing, laboratories and electrical manufacturers usually experience serious operational bottlenecks with the conventional heat run tests.
Traditional primary injection sets employ contact autotransformers (Variacs) with carbon brush sliders. When driving continuous currents above 3,000A for 8 to 24 hours, contact friction and localized overheating cause severe brush pitting, arcing, and sudden voltage drop, forcing test aborts and specimen re-cooling.
Thousands of amperes generates significant stray alternating magnetic fields. Standard thermocouple sensors deployed inside switchgear compartments are subject to magnetic induction loops, EMI and reference junction drift, giving false temperature spikes of 3°C to 8°C.
According to IEC 62271-1 and IEC 61439-1, the heat run must continue until the rate of temperature rise does not exceed 1 K per hour. Manually logging thermometer readings across 32 or 64 channels is time-consuming, error-prone and invites either a premature shutdown or unnecessary waste of energy.
These testing failure points are eliminated because our automated temperature rise test benches incorporate heavy-duty induction voltage regulation and multi-channel isolated platinum resistance data acquisition.
System Configuration Inquiry
The source of the heat generated in electrical switchgear is resistive losses (P = I²R) along the main busbars, disconnect blade contacts, circuit breaker tulip contacts, drawout socket jaws, high-current connector links, and cable connection terminals. As conductors heat up, the resistivity of copper increases according to ρT = ρ20 × [1 + α(T - 20)], where α = 0.00393 / K. With a 60 K temperature increase, the resistance of electrical increases by approximately 23.6%, resulting in an increase of the load impedance of the primary injection loop during testing.
DDL-WS Technical Configuration Inquiry
Sagging current is a problem if the primary injection source operates in an open loop or motor-driven carbon brushes. The test current decays as bus bars heat up. A 5% drop in test current results in a 9.75% reduction in Joule heating power (heating power proportional to I²), corrupting thermal equilibrium data and invalidating type test certification under IEC 62271-1.
Our DDL-WS series incorporates continuous closed-loop current feedback controlled by programmable logic controllers (PLCs). This ensures precise regulation of loop current over long periods of time. The system continuously samples real-time loop current via precision class 0.2 current transformers, executing smooth voltage micro-adjustments within 50 milliseconds to keep output current stable within ±0.5% throughout 24-hour heat runs.
To maintain continuous testing under IEC 62271-1, the core regulator is the most essential reliability element in any of our temperature rise test equipment. We strictly prohibit the use of Dry-type sliding carbon brush Variacs in our high current systems. We standardize on heavy-duty Oil-Immersed Induction Voltage Regulators (IVR) in these systems. Carbon brush variacs are not interchangeable with induction regulators; saving capital on carbon brushes costs you continuous maintenance and downtime, making the engineering trade-off clear. Cheap slide-wire designs do nothing for heavy duty cycles.
| Engineering Parameter | DEMIKS Oil-Immersed Induction Regulator (IVR) | Conventional Contact Variac (Carbon Brush) |
|---|---|---|
| Regulation Mechanism | Electromagnetic induction via rotor angular rotation; zero sliding contacts | Mechanical friction carbon brush sliding directly on exposed copper windings |
| Continuous Duty Cycle | 100% continuous duty rating at full rated load for 24+ hours | Limited continuous duty; carbon brushes overheat after 4 to 6 hours |
| Mechanical Wear & Pitting | Zero wear parts; immersed in transformer insulation oil | Frequent brush replacement, contact surface pitting, and copper grooving |
| Waveform Distortion (THD) | Sinusoidal output with total harmonic distortion ≤ 3.0% | Harmonic distortion often exceeds 5.0% due to brush contact resistance nonlinearity |
| Cooling & Environmental Protection | Sealed oil tank cooling (ONAN); immune to dust, humidity, and chemical vapors | Air-cooled open frame; highly susceptible to ambient industrial dust and moisture |
| Service Life Expectancy | Exceeds 20 years with periodic oil dielectric testing | Requires carbon brush replacement every 300 to 500 running hours |
By rotating a cylindrical wound rotor within a stator core, our induction regulator smoothly alters magnetic flux coupling to deliver stepless, spark-free voltage regulation from 0V to maximum output. Because our regulator produces a spark-free variation of magnetic flux coupling, it produces a smoother transition from 0V to maximum output than mechanical regulators. The voltage regulator provides fundamental sinusoidal current waveforms necessary for electromagnetic verifications according to the IEC standards.
AccuTuro Zen temperature monitoring employs sensors and signal conditioning devices that are resistant to high-density magnetic flux. In a 5,000A busbar loop, stray magnetic fields can exceed 15 milliteslas, which creates significant common-mode and normal-mode noise voltages in sensor wiring. DEMIKS engineers resolve this instrumentation challenge because thermocouples do nothing for heavy electromagnetic noise immunity, whereas four-wire Pt100 RTDs provide reliable common-mode rejection with NIST traceable calibration in demanding OEM switchgear testing applications on the bench.
A DWS-700 multi-channel temperature recorder uses industrial Class A 4-wire Pt100 resistance temperature detectors (RTDs). Two leads supply a stable 1mA excitation current, while the other two leads measure the voltage drop directly across the platinum resistor. Lead wire resistance and temperature gradients along the test cable bundle are completely eliminated.
Each measurement channel features 1,500V RMS galvanic isolation and differential delta-sigma analog-to-digital conversion. When used with 1,500V RMS galvanic isolated sensor probes, dangerous ground loops across long switchgear lines and potential test instrumentation damage are eliminated.
Our measurement system achieves an absolute temperature accuracy of ±0.5°C with a display resolution of 0.1°C across a measurement range of -50°C to +200°C. Data logging intervals are user-configurable from 1 second to 60 minutes, with real-time temperature curves plotted dynamically across all active channels.
"A temperature rise test is considered complete when the rate of temperature rise at all monitored measurement points does not exceed 1 K per hour over a continuous observation period."
— IEC 62271-1 Standard DefinitionThe international standards IEC 62271-1 (High-Voltage Switchgear and Controlgear), IEC 61439-1 (Low-Voltage Switchgear and Controlgear Assemblies), and IEC 60947-1 (Low-Voltage Switchgear and Controlgear Appliance Testing) give exact mathematical ways to determine when a test specimen has attained thermal steady state.
The heat run test will continue until the temperatures stabilize at the monitored points. The steady state is considered to be reached when the temperature rise does not increase by more than 1 K per hour over a consecutive observation interval of one to two hours. This will also be considered stable if the temperature rise averages 0.5 K for a 2 hour period.
Our supervisory control software automates this determination by continuous regression analysis:
The software continues to calculate the thermal rate of change (dT/dt) for every individual sensor channel over 60 minute rolling windows.
When all of the critical monitored locations satisfy dT/dt ≤ 1 K/h, the system will generate an audible signal and records the final equilibrium temperatures. The system also executes an automated safe ramp down of the primary current.
The system supports immediate 4-terminal DC resistance measurement of electrical coils and transformer windings to calculate average internal winding temperatures via the resistance method.
On completion of a test the system generates detailed test records containing channel assignment tables, peak temperature logs, ambient temperature curves, and standard compliance pass/fail assessments which are exportable to PDF and Excel.
Diverse joint plating technologies and insulating media are rated for maximum allowable temperature rises. Our test benches are designed to monitor these, compare them to the threshold values, and perform an automated benchmarking function against them.
| Component / Material Type | Applicable Standard | Max. Permissible Temperature Rise (ΔT) | Max. Absolute Operating Temperature |
|---|---|---|---|
|
01
Bare Copper Busbars & Conductors
|
IEC 62271-1 / GB/T 11022 | 60 K | 100 °C |
|
02
Silver-Plated or Nickel-Plated Contacts
|
IEC 62271-1 / IEC 61439-1 | 75 K | 115 °C |
|
03
Tin-Plated Bolted Joints & Terminals
|
IEC 62271-1 / IEC 60947-1 | 65 K | 105 °C |
|
04
External Cable Connection Terminals
|
IEC 61439-1 Clause 10.10 | 70 K | 110 °C |
|
05
Operating Handles & Manual Controls (Metallic)
|
IEC 62271-1 / IEC 61439-1 | 30 K | 70 °C |
|
06
Enclosure External Accessible Surfaces
|
IEC 62271-1 / IEC 61439-1 | 30 K (Metallic) / 40 K (Insulating) | 70 °C / 80 °C |
|
07
Liquid-Immersed Transformers (Top Oil / Windings)
|
IEC 60076-2 Clause 7 | 60 K (Top Oil) / 65 K (Winding Average) | 100 °C / 105 °C |
In compliance with IEC 62271-1, each temperature rise test system is engineered to specific requirements of testing capacity, test bay floor layout, and utility power supply. Our standard, modular product families include:
Extensive factory acceptance testing (FAT) is conducted on all temperature rise test systems in our Shanghai manufacturing facility. All voltage regulators, current sensors, and temperature acquisition channels are calibrated to the national metrology standards traceable to the National Institute of Metrology (NIM) and CNAS accredited calibration laboratories, equivalent to NIST traceability.
| Subsystem / Module | Factory Acceptance Verification Protocol | Delivered Compliance Document |
|---|---|---|
| Induction Voltage Regulator | Dielectric breakdown voltage test (oil withstand ≥ 40kV), winding insulation resistance (≥ 1000 MΩ), continuous heat run at 100% rated kVA | Factory Dielectric & Thermal Routine Test Report |
| Primary Current Transformers | Ratio error and phase displacement calibration against Class 0.05 standard CT from 5% to 120% of rated current | Traceable Calibration Certificate (Accuracy Class 0.2) |
| DWS-700 Thermal Recorder | Multi-point temperature simulation calibration (-20°C to +150°C) against precision Class 0.01 resistance decade box | Individual Channel Calibration Certificate (±0.5°C Verified) |
| Integrated Safety Interlocks | Zero-start interlock, overcurrent trip within 20ms, emergency stop loop, specimen overtemperature trip verification | Safety Functional Logic Test Record |
Shanghai DEMIKS Electric Power Technology Co., LTD (DEMIKS) was established in 2025 and is based in the Lingang Special Area of the China (Shanghai) Pilot Free Trade Zone. We supply high-voltage test equipment and provide technical support for factory, laboratory, and field testing.
Our product range includes primary injection test sets, multi-channel temperature recorders, switchgear temperature rise test systems, AC/DC withstand test equipment, series resonant test systems, impulse generators, and thermal cycling test systems.
DEMIKS has exported equipment to Brazil, Peru, Argentina, the United States, Canada, Bulgaria, France, and Italy; we help customers select and configure equipment for their test requirements. Every test system includes a traceable factory calibration report, electrical schematics, and an available overseas engineering team for on-site installation, commissioning, and operator training. On-site service fees depend on the number of engineers and the time required.
Our engineers support clients with test bay electrical layouts, primary low-inductance busbar loop routing, and design of busbar connection clamps. Further, we assist clients with alignment to local authorities’ requirements for compliance and methodology, and local accreditation audits.
Below are our formal terms and conditions governing response to quotations, manufacturing schedules, shipping, and payment. ?
For three-phase switchgear enclosures, busbar trunking systems, and multi-pole circuit breakers, our systems incorporate three independently motorized single-phase induction voltage regulators that are linked to a centralized PLC controller. Independent phase regulation is necessary because spatial conductor geometry and asymmetric magnetic coupling between phases results in unequal loop impedances. The automated closed-loop feedback dynamically trims primary voltage on each phase separately, maintaining balanced continuous current within ±0.5% across phase A, phase B, and phase C simultaneously throughout 24-hour test runs without manual operator rebalancing.
The Thermocouple outputs only produce tens of microvolts per degree Celsius of temperature difference, making them susceptible to temperature difference noise and electromagnetic interference from heavy alternating current (AC) magnetic fields. In contrast, 4-wire Pt100 RTDs operate with constant current excitation to compensate for lead wire resistance variations. Together with shielded twisted-pair cabling and differential galvanic isolation, our instrumentation achieves stable channel accuracy of ±0.5°C in measurement when exposed to strong AC magnetic fields.
Each system is equipped with factory issued Routine Test Certificates, traceable Calibrations for current transformers and temperature loggers, electrical schematics, PLC ladder logic, and a complete Operation manual.
Hardware-based multi-layer safety interlocking with zero-start protection (preventing voltage energization unless regulator is at zero position) and overcurrent fast-trip relays (trips within 20 milliseconds) are included in our design. So is emergency shutdown due to specimen overtemperature, cooling fan airflow interlocks, and emergency stop circuits. The system logs an event if any of the monitored points goes above the programmed emergency limits, and safe-trips the main primary power in the process.
When you purchase equipment, you can request on-site commissioning service, and we will send commissioning engineers to your facility around the world. Our engineers will supervise equipment positioning, link high current busbar connections, commission utility power supplies, calibrate thermal channels, and give hands-on training to your test operators using your production switchgear specimens in full accordance with IEC 62271-1 standards. On-site engineering service fees are determined by the number of engineers and duration of service required.
