Safety Testing / Surge Testing Description

There are a variety of Electrical Safety Testing and Surge Testing Equipment available that enables the user or manufacturer to test the integrity of electrical insulation, electrical isolation, component specifications, cable / connection bonding or electrical isolation. These instruments are commonly used to verify the specifications of a manufactured product as well as confirm the safety for the user, installer and operator of an installed or repaired system. Tests are typically performed on wire, cable, motor windings, switchgear, insulators, components, incoming service, transformers and any electrical device that must meet safety standards.

Typical industries required to test according to safety standards:

Industrial Residential Component Safety Repair Contractor, HVAC, Electrical

Medical Energy Telecommunication Agency Approval (i.e. IEC, UL, CSA, OSHA, ANSI, CE, etc.)

Hipot Testers, Ground Bond Testers, Leakage Current Testers or Impulse/Surge Testers are required tests for product and system evaluation and are accepted tests in order to meet Industry Electrical and Safety Standards.

Hipot Testers (High Voltage Testers aka Dielectric Tester)

One of the primary differences between a Hipot Tester and an Insulation Resistance Tester is that the Hipot Tester will be used for evaluation and destructive testing. An IR Tester (Insulation Resistance Tester) is primarily used for insulation evaluation only. Hipots are also referred to as High Voltage Testers, Dielectric Testers, Dielectric Withstand, or Breakdown Testers. They are High Voltage testing instruments used predominately to test and confirm product specifications, as well as electrical breakdown limits.

Although the instrument is used for testing insulation in finished electrical equipment and cables, it may also be used to check the electrical integrity and quality of motors, switchgear, transformers and capacitors. The primary purpose of using a Hipot Tester is confirming whether the insulation is within specification. It is a requirement of most safety regulation agencies like IEC, UL, CSA, OSHA, ANSI, and CE  that manufactured electrical products and systems meet specified safety standards. The safety of all personnel, consumers or homeowners is the primary objective. It is a required test for industrial and consumer appliances and electrical products and very commonly found on a production lines.

Types of Hipot Testers

• AC Hipot Test
• DC Hipot Test

Test voltages are selected based on the equipment being tested and the type of test being applied. Voltage ranges extend from as low as 500 Volts to over 50KV. The choice of voltage range is based on both the product being tested and specific application. The primary test requires a high voltage (higher than the normal operating voltage) be applied and a constant current. The outcome of the test is to evaluate the acceptable specification ranges, as well as possible breakdown ranges.

When selecting a Hipot tester, both the maximum voltage and maximum current required to meet the safety standards that have been predetermined for the product class and product category must be known. Trip-current ranges are normally between 20 and 100 milliamps. Some special order units can be made to fit the exact requirements of your test.

Comparing DC Hipot vs AC Hipot (While AC Hipots may be more popular, when is a DC Hipot needed?)

DC Hipot Test Advantages

• Since a DC Hipot applies exactly the recommended voltage and does not cycle between positive and negative peak voltages, it is effective regardless of the product or system capacitance.
• In highly capacitive circuits, DC testing will charge the capacitor where it might trip with an AC tester and not be possible to test at all.
• In order to protect the system, "Y" capacitors are frequently used by instrument/appliance manufactures to protect DC electronics. They protect controls and computers against high frequency surges and RF noise in the AC line by shunting noise to ground. An AC Hipot that normally charges from positive voltage to zero and then negative voltage will have a harder time providing the test with Y capacitors in the ciurcuit, than a DC Hipot.

• The current trip for the leakage may be set on a significantly lower value. The manufacturer may then identify and remove products with marginal insulation that may have otherwise passed.

DC Hipot Test Disadvantages

• Only one direction of polarity can be tested with DC
• Not all test standards consider DC testing to be on the same par as AC testing. While most standards allow either, testing of large motors is still by AC Hipots. There are some very old legacy standards that predate the availability of DC Hipots
• Unlike its AC counterpart, the DC Hipot test cannot replace the test for line voltage leakage

AC Hipot Test Advantages

• AC testing checks both polarities of voltage. Products that use AC for normal operation should not be tested by a DC Hipot
• Information with an AC Hipot is instantaneous. DC Hipot testers require a few seconds at the end of each test to discharge the internal capacitor. Although not normally a problem, it may be a consideration when testing time is of the essence, as in a production line
• AC testing is accepted by all test standards

AC Hipot Test Disadvantages

• Since an AC source for testing produces a peak positive and negative signal, highly capacitive circuits may reduce the accuracy and timing of the test and interfere with leakage and tripping current. (see first bullet for DC Hipot Advantages)
• Since AC testing actually applies a peak positive voltage as well as a peak negative voltage and then cycles between each, the current produced during testing is greater and may actually weaken the insulation being tested. This in turn may cause failure of the product either in normal use. We welcome your comments on your experience.

Insulation Resistance Test (High Resistance Test aka IR Tester, Megaohm Meter, Megger)

Please note that an IR Tester is NOT a substitute for a Hipot Tester, but the IR test may be included as an optional test capability on selected Hipot Units. If you require both tests, review your product selection.

The safety of electrical wiring insulation is tested using Megohmmeters / Insulation Resistance Testers (IR Testers). Equipment damage, electrical shock, and fires can occur as electrical insulation breaks down. This is a high resistance test to see if the insulation on equipment is in good condition or in a possibly damaged and deteriorated condition. The test evaluates the condition of insulation or electrical isolation. The typical test applies a specified or calculated voltage at low current and measures the resistance in ohms. The ranges of resistance for a passing value can be from a few megohms to teraohms.  Often this test is done to provide predictive maintenance for failure of equipment, wire, and cable.

If your application is not for a HiPot and instead for an IR Tester, please see our full IR department page:
Products > Micro-Ohmmeter / Milliohmmeter / Megohmmeter > Megohmmeter / Insulation Resistance Testers
And learn more from our Megohmmeter / IR Tester Buyer's Guide

Ground Bond Test or Earth Bond Test (High Current Test) Testers

Ground Bond Testers measure the resistance between ground and the equipment or surface being considered. Testing of large scale electrical installations can also be evaluated. High current is applied and the voltage drop at the measurement or connection point is measured, which in turn allows each unit to display resistance. Although acceptable resistance values depend on the standard and specification of the tested apparatus, low values such as 0.5 ohm or 0.1 ohm may meet specified standards. Please check your requirements.

Standard certification is usually required for safety. Since the test is the measurement of very low resistance, this test relates to the safety of the system. The instrument or surface is tested for electrical hazard or shock. Some key features of applications for Earth and Ground Bonding Instrumentation include:

• Perform protective continuity testing in Compliance with International Safety Standards
• Protective continuity resistance measurement for medical devices and general electrical devices
• Ground connectivity testing when installing electrical machine tools and distribution panels
• Test protective grounding and electrostatic fields such as grounding work for medical equipment
• Evaluate contact status using large currents
• Feedback control system capable of applying a stable current, even with a fluctuating load
• Provide a soft-start function which confirms the connection to the device under test before applying current

Some key product features which may enhance the capability of Earth and Ground Bonding Instrumentation may include:

• Test Sequence Memory Capability
• Ground Bond Test Capability
• Broadband Arc Detection
• 4-Wire Milli-Ohmmeter Function
• Secure Level of Operator Safety
• High Power Output
• Wide Range of Voltage Capabilities
• Built-in Phase Angle Measurement for AC Signals
• Ramp High / Dwell Low Current Limits
• Test Report capability
• Ethernet and GPIB Pico-Amp Leakage Measurement
• Cable Compensation Multi-Mode IR Test Capability
• Continuously Variable IR Test Voltage Capability

Since the testing of Earth and Ground Bonding is a measure of low resistance, the procedure may utilize a two wire system, but usually requires a four wire (Kelvin) test probe. Kelvin Probes permit resistance measurements that ensure all contact and lead resistances of the probes are compensated, leading to a more accurate result over two wire testing.
Key Users of Earth and Ground Bond Testers Include:

• Telecom Engineers
• Power Systems Engineers
• Electricians
• Electrical contractors
• Medical Test Engineers
• Consulting Engineers

Leakage Current Testers

A Leakage Current Testers primary objective is to measure leakage current before it becomes a danger to the operator or patient (medical use). Leakage Current (Touch Current) can be dangerous! Electrical devices are typically designed with sufficient insulation, so that operators do not experience electrical shock. However, insulation may deteriorate over time. One of the largest applications for a Leakage Current Tester is in the medical industry. Patient and operator safety and health, especially in a Medical environment, includes requiring leakage current testing on most equipment.

Equipment manufacturers and those doing repairs must adhere to for Leakage Current Standards. These Standards are in accordance with IEC, UL, JIS, ANSI, VDE, etc.

Markets for Leakage Current Testers

• Medical
• Industrial
• Residential
• Consumer Electronics
• Service
• Laboratory
• Production

Leakage Current Tester applications

• General Industrial Electrical Use
• Medical Standard Equipment
• Medical Emergency Equipment
• Computers
• Residential Appliances
• Electrical Toys and Monitors

The test is performed by applying a voltage across the conductor or circuit, where a leakage current is measured across the insulation. For Medical Electrical Test and Monitoring Equipment, it is recommended to always use an isolation transformer when measuring leakage current. Medical-use electrical devices use a step-up isolation transformer or similar component operating at 110% of the rated supply voltage as the power supply for the device under test.

Key features to consider for selection of Leakage Current Testers

• As a class, they are an economical tester to comply with standards governing electrical devices
• Capability for required standards IEC, JIS, UL, DIN VDE, ANSI, etc.
• Selectable test current
• Polarity switching reduces cycle time
• Rated currents to meet new Standards
• Touch panel for interactive operation.
• Complete communications functionality
• External I/O Support
• Automatic testing for production line applications
• Memory storage of programmed tests
• Memory storage of test results
• Report function capability
• Measure housing leakage current
• Single phase or three phase capability
• Capable of 120VAC or 240 VAC appliance testing
  

The safety of human life and personnel is always the first concern when using any electrical device. These devices are designed to meet many, if not all, of these safety requirements.

Impulse /Surge Testers

Impulse Generators originated from the need to test electrical equipment and surge arrestors by simulating the high voltage and current of lightning and other surges. Modern day impulse generators originate from the work of Edwin Marx in the 1920’s. You may see “Marx Generator” or “Marx Circuit” in manufacturer literature. There are two types

• Impulse Voltage Generators . High voltage pulse is generated by charging multiple capacitors in parallel then discharging in series.
• Impulse Current Generators. High current pulse is generated by charging multiple capacitors in parallel then discharged in parallel.

The generated voltage and current pulses are extremely fast, in the uSec neighborhood. Over time, different standards have been developed for various equipment, so there is no single model that will test all applications. Therefore, it is important to know first the test method you need to comply with before beginning model selection.

Medical Device Safety Testers

Medical Device Safety Testers are a class of Electrical Safety Testing and Surge Testing Equipment designed to test Medical Devices for operator and patient use. They include Hipots, Ground Bond Testers, and Leakage Current Testers, and multifunction instruments that can perform more than one test. Medical Device Safety Testers are used by equipment manufacturers, those doing repairs, and others to meet specific medical device safety standards.

Learn more about the tests and test methods elsewhere in this guide and visit the Medical Device Safety Tester department for our wide selection of models.

Browse: 926    Date: 2019/11/24