Hipot Tests Research Articles

Configuration of instrumentation wire extraction for ITER magnet feeder system

For the quench detection, the high voltage (HV) instrumentation wires should be led out from the electrical insulation layers of ITER magnet feeders. Based on the latest design, at least four HV instrumentation wires need to penetrate from the busbar joint, which break the integrity of the intact insulation layer. A perforated crack may generate along the instrumentation wire in the insulation layer. At some specific ambient pressure and operational voltage, the crack will cause Paschen discharge inevitably, which is the most serious risk threatening the safe and steady operation of the feeders. There are over 200 busbar joints with the instrumentation wires penetration need to be manufactured on the ITER site, and a reliable and durable insulation structure and technology need to be developed for the extracting HV instrumentation wires of ITER magnet feeder. In this paper, the HV instrumentation wire extraction and the specimen design are presented. The electrical properties of the specimen, including the DC hi-pot test, Paschen test and Partial Discharge (PD) test, are reported and discussed.

Medium Voltage Converter Inductor Insulation Design Considering Grid Requirements

Medium voltage (MV) SiC devices facilitate direct (without 50-/60-Hz transformer) connection of the power electronics converter to the MV grid using simple topology. Compared to the insulation design of MV inductors that have been widely used in the power system, the insulation design of the MV converter filter inductors has new challenges. Particularly, the grid impact on insulation requirements on converter filter inductors is rarely discussed. This article introduces the insulation design of a grid-side filter inductor for a 13.8-kV power conditioning system converter. The grid insulation requirements, including the short-duration power frequency overvoltage and the lightning impulse voltage, are considered in the design. To meet the requirements, the layer-to-layer insulation, winding-to-core/ground insulation, the air gap discharge between the winding and the core, the local electric field, as well as the interturn transient voltage distribution are considered. The designed inductors are validated by the 46 kV (>1 min) dc hi-pot test, 12-kV ac partial discharge test, one-hour single-phase converter full rating test, as well as three-phase converter full rating test.

Highly isolated switching mode power supply for solid-state transformers in railway vehicles

This paper discusses an isolated switching mode power supply (SMPS) with an AC 30 kVrms insulation capability for application to the solid-state transformers (SSTs) in railway vehicles. The insulation capability of the SMPS should be higher than AC 25 kVrms for application at the SSTs in railway vehicles. The proposed highly isolated SMPS is superior to commercial isolated power supplies with low insulation capability, which is normally less than 20 kV. The input side of the proposed isolated SMPS is physically separated from its output side by a specially designed miniature high-frequency (HF) transformer to obtain high insulation capability. The core of the miniature HF transformer is separated by insulation material. The primary and secondary coils are wound around each separated core. A CLLC resonant converter that consists of a primary resonant capacitor (C), two inductors (LL), and a secondary resonant capacitor (C) is applied as the proposed isolated SMPS topology to improve the output voltage regulation performance, which varies due to a large leakage inductance derived from the airgap of the proposed miniature HF transformer. Experiments are carried out to verify the CLLC resonant converter of the proposed isolated SMPS. Electrostatic finite element method (FEM) simulations and high potential (HiPot) tests are carried out to verify the AC 30 kVrms insulation capability of the proposed isolated SMPS. The electrostatic FEM simulations demonstrate the DC 42.43 kV insulation capability, and the HiPot tests verify the insulation capability from AC 5 kVrms to AC 30 kVrms.

Electrical and Thermal Characterization of 3D Printed Thermoplastic Parts with Embedded Wires for High Current-Carrying Applications.

Fabrication of parts exhibiting multi-functionality has recently been complemented by hybrid polymer extrusion additive manufacturing in combination with wire embedding technology. While much mechanical characterization has been performed on parts produced with fused deposition modeling, limited characterization has been performed when combined electrical and thermal loads are applied to 3D printed multi-material parts. As such, this work describes the design, fabrication, and testing of 3D printed thermoplastic coupons containing embedded copper wires that carried current. An automated fabrication process was used employing a hybrid additive manufacturing machine that dispensed polycarbonate thermoplastic and embedded bare copper wires. Testing included AC and DC hipot testing as well as thermal testing on as-fabricated and heat treated coupons to determine the effect of porosity in the substrate. The heat-treated parts contained reduced amounts of porosity, as corroborated through scanning electron microscopy, which led to 50 % increased breakdown strength and 30 to 40 % increased heat dissipation capabilities. The results of this research are describing a set of design protocol that can be used as a guideline for 3D printed embedded electronics to predict the electrical and thermal behavior.

Final Assembly and Factory Testing of the Jefferson Lab SHMS Spectrometer Quadrupole and Dipole Superconducting Magnets

Jefferson Lab is constructing an 11-Gev/c electron spectrometer called the super high momentum spectrometer (SHMS) as part of the 12-GeV JLAB upgrade for experimental Hall C. Three of the five superconducting SHMS magnets are under construction at SigmaPhi in Vannes, France, as a result of an international competition for design and fabrication. The three magnets Q2 and Q3 60 cm bore quadrupoles and the 60 cm warm bore dipole are complete or near complete and have many design features in common. All three magnets share a common superconductor, collaring system, cryostat design, cold to warm support, cryogenic interface, burnout resistant current leads, dc power supply, quench protection, and instrumentation and controls. The three magnets are collared, installed in cryostats and welded up, and in various stages of final testing. The Q2 quadrupole is due to ship from France to America in August arriving during this ASC conference and has passed all final hipot, leak, and pressure tests. The dipole is in leak and pressure testing as of July 2016, whereas the Q3 quadrupole requires some outer vacuum vessel assembly. Delivery of the Q3 and dipole magnets will follow the Q2 at about one month intervals. Factory testing has included hipot and electrical tests, magnetic tests at low field, mechanical alignments to center the coils, leak tests, and ASME code required pressure tests. Upon installation in Hall C at JLAB cold testing will commence.

Design of an Integrated Mechanical Fatigue Test Apparatus for S-Bend Busbar

An integrated test apparatus was designed and constructed in a cryostat in order to qualify the performance of high-voltage (HV) insulation on a mockup ITER TF feeder S-bend (S-shaped) busbar after mechanical fatigue tests at room temperature and low temperature, respectively. The force generator was designed and developed with a hydraulic cylinder as a source of cyclic load. The traveling distance of the hydraulic cylinder can be adjusted between 10 and 100 mm in order to meet different displacement requirements. The fatigue tensile load is transmitted by a reciprocating ball-end shaft at the free end of the S-bend. Welded diaphragm bellows was applied as a flexible vacuum envelope for the transmission rod. The fatigue test displacement and the stretching frequency were set according to the theoretical analysis result. The leakage current in the hipot test of the S-bend busbar after thermal and mechanical cycles was 13.7 μA at 30-kV dc, less than the ITER requirement of 60 μA. The integrated test apparatus has been fully commissioned and is ready for the qualification tests of the HV insulation of the ITER S-bend busbar affected by mechanical and thermal fatigue loads.

High-Voltage Stacked Diode Package

The Army is moving to a more electric force with a number of high-voltage applications. To support this transition, there have been efforts to develop high voltage (15–30 kV) single-die 4H-silicon carbide (SiC) bipolar switches and diodes. However, packaging these high-voltage devices has proven to be challenging since standard packaging methods cannot withstand the high voltages in a compact form. Therefore, this work aims to develop a compact prototype package with improved size, weight, and power density by stacking diodes. The stacked diode approach allows elimination of almost half of the wirebonds, reduces the board size by 45%, and reduces the package inductance. A module has been designed, fabricated, and tested which is the first 30 kV module reported in the literature to stack two high-voltage diodes in a series configuration. The package has a number of features specific to high-voltage packaging including (1) two fins that extend the perimeter of the package to mitigate shorting, and (2) all the leads were designed with rounded corners to minimize voltage crowding. Hi-pot tests were performed on the unpopulated package and showed the package can withstand 30 kV without breaking down. The completed package with the stacked diodes showed avalanche breakdown occurring at 29 kV. The complete package was then compared to an equivalent discrete diode module and showed a 10X reduction in size. During a clamped-inductive load test the stacked diodes showed lower parasitic capacitance, faster reverse recovery time, and lower turn on energy as compared to the discrete diode packages.

Turbine generator rotor and stator winding hipot testing

This article reviews the literature and international and national standards concerned with factory and maintenance hipot testing of turbine generators, although much of the article is also applicable to hydrogenerators and synchronous motors.

Basic Electronics: AC Transformers

Basic Electronics: AC Transformers

Experiences with peel strength

PurposePeel strength numbers are part of a laminate's specifications and should characterize the specific bond performance (copper adhesion) under test conditions. Unfortunately, from both a theoretical and a practical point of view they are not able to do that. This study seeks to address this issue.Design/methodology/approachThis paper has been written to show the main impacts on the measured peel strength numbers in the IPC‐TM‐650 peeling test. From an extensive database regarding peel numbers for diverse foil types, foil thicknesses and treatment roughnesses it is possible to show the influence of prepreg type, foil thickness and roughness on the measure peel strength.FindingsCopper adhesion to laminating resin is insufficiently described by peel strength data because of the impacts of foil thickness, stiffness on bending (physical bending work, stress distribution underneath the peeling line) and the treatment roughness. The latter works reinforcing regarding the (low) resin strength and this influence is measured on resin strength instead of real bond. Fracture due to peeling is cohesive, mostly with a totally intact copper‐resin interface. This is especially true in high performance laminates that show low peel strengths not because of bad copper bonding but because of brittle resins (filled and unfilled).Originality/valueUsers have to understand the limited benefit of the IPC peel test in characterizing copper‐resin bonds. Peel increase on (low bond) high performance resins by increased foil roughness is not a practical way in the field because of no bond improvement (interface) and heavy disadvantages in dielectric thickness (HiPot tests at thin core laminates), respectively.

Test results for a Nb/sub 3/Sn dipole magnet

A cosine theta type dipole magnet using Nb/sub 3/Sn conductor have been designed, built and tested. D19H is a two-layer dipole magnet with a Nb/sub 3/Sn inner layer and a recycled NbTi outer layer. Coil-pairs are connected with two of the four Nb/sub 3/Sn splices in a high field region, and compressed by a ring and collet system. The ramp-rate sensitivity and the splice resistances were pleasingly low; and the 4.4 K training was rapid. At 1.8 K, however, the unusually high frequency of outer-coil fast-motion events increased with current, effectively creating a training-ceiling at 90% of the expected outer-layer limit (10.2 T). A low end-load applied to a relatively fluffy outer layer is believed to have caused this training limit. The end-load was increased; but a retest was aborted after the magnet failed a precautionary hipot test.

Assessment of insulation condition in rotating machine stators

The authors describe an attempt to assess the condition of stator insulation in standby generators in two generating stations. The insulation condition was estimated by comparing diagnostic test results for different machines with similar insulator or for different phases of the same machine. The diagnostic tests included measurements of insulation resistance, partial discharges, and capacitance and dissipation factors as well as AC and DC hipot tests. The methods used to assess the insulation system are outlined in detail, and the assessment results are described and discussed. >

Experience with AC Hipot and Partial Discharge Tests for Commissioning Generating Station Cables and Switchgear

Experience with AC Hipot and Partial Discharge Tests for Commissioning Generating Station Cables and Switchgear

Experience with AC hipot and partial discharge tests for commissioning generating station cables and switchgear

Test equipment is described which is suitable for AC hipot and partial discharge testing of 5 and 15 kV shielded cables of lengths up to about 600 m. The equipment can be used to test 5 and 15 kV metal-clad switchgear. Ontario Hydro's experience at two nuclear generating stations using this AC test equipment is presented. The equipment can be used to assure the integrity of cable systems (less than 600 m long) already in service. The reasons for switching to AC testing of cable systems are outlined. Practical experience shows that the partial-discharge test is very effective in identifying installation problems in cables and switchgear. A number of problems are identified with the AC tests that a DC test would have missed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Resonant Surge Field Test for SF6 Switchgear

The one-minute ac hipot test has serious disadvantages as the sole criterion for commissioning of gas-insulated switchgear. The use of an ac resonant test set to generate a 60 Hz oscillating surge is described along with experimental evidence indicating the advantages of such a test as an addition to the usual one-minute ac test.