The most important specifications to consider when searching for hipot testers include AC and DC output voltage, AC and DC output current, resistance range, insulation limit, and test time. Output voltage can either be AC or DC. The type of test will determine what level of voltage will be supplied. For example: in hipot testing the output voltage is usually very high. Output current can either be AC or DC. The type of test will determine what level of current will be supplied. For example: in hipot testing the output current is usually very low. Testers can also measure the resistance range. The insulation limit specification determines the voltage range the insulator can withstand. Many tests performed for electrical safety have a test time requirement. This is the overall time of the test.

The testing method for hipot testers can be automatic, semi-automatic, and manual. Some test instruments are fully automated to store and perform testing from a program. They may also have the ability to perform a series of electrical safety tests. Semi-automatic is a combination of automatic and manual testing capability. Manual testing requires that an operator be present to make physical changes to the test parameters.

Displays and interfaces are also important to consider when searching for hipot testers. Display choices include analog meters, digital meters, and LED indicators. Interfaces include GPIB, RS232, printer ports, scanner ports, and printouts. Safety agency ratings that can be applied to hipot testers include CE conformity marks, CSA, IEC, IPC, TÜV Rhineland (US, C, US & C), UL listing, and VDE. Common features for hipot testers include built-in calibration, buzzer or annunciator, front panel lockout, memory or storage, multiple test setup, PLC interface, rapid cutoff, remote control, selectable output frequency, and warning indicator lights.

Most people know what a continuity test is. A continuity test checks for good connections. Continuity tests are done by seeing if currents flow from point to point. If the currents flows easily the points are connected. “Hipot” is short for high potential => high voltage. Hipot testing checks that isolation is good. A hipot test is done to ensure that no current will flow from point to point.

Contnuity test = ensure current does flow from point to point.

Hipot test = turn up the voltage to ensure current does not flow from point to point.

Why test using high voltage?

A  hipot test is done to ensure that isolation is secure ie that no current is leaking out of the circuit. Good isolation guarentees safety to the user of electrical products.

Obviously this safety is a requirement in photovoltaic technology as well.

Common high voltage tests

1. Dieelectric Breakdown Test
2. Dieelectric Withstanding Test
3. Insulation Resistance Test

10.3.1 Purpose
To determine whether or not the module is sufficiently well insulated between current carrying parts and the frame or the outside world.
10.3.2 Apparatus

• a) A d.c. voltage source, with current limitation, capable of applying 500 V or 1 000 V plus twice the maximum system voltage of the module (as marked on the module – see Clause4) according to item c) of 10.3.4.

• b) An instrument to measure the insulation resistance.

10.3.3 Test conditions
The test shall be made on modules at ambient temperature of the surrounding atmosphere (see IEC 60068-1) and in a relative humidity not exceeding 75 %.

10.3.4 Procedure

• a) Connect the shorted output terminals of the module to the positive terminal of a d.c. insulation tester with a current limitation.

• b) Connect the exposed metal parts of the module to the negative terminal of the tester. If the module has no frame or if the frame is a poor electrical conductor, wrap a conductive foil around the edges and over the back of the module. If the module does not have a glass superstrate, also wrap the foil around the front of the module. Connect the foil to thenegative terminal of the tester.

• c) Increase the voltage applied by the tester at a rate not exceeding 500 V⋅s–1 to amaximum equal to 1 000 V plus twice the maximum system voltage (i.e. the maximumsystem voltage marked on the module by the manufacturer, see Clause 4). If the maximum system voltage does not exceed 50 V, the applied voltage shall be 500 V.Maintain the voltage at this level for 1 min.

• d) Reduce the applied voltage to zero and short-circuit the terminals of the test equipment to discharge the voltage build-up in the module.

• e) Remove the short circuit.

• f) Increase the voltage applied by the test equipment at a rate not to exceed 500 V⋅s–1 to 500 V or the maximum system voltage for the module, whichever is greater. Maintain the voltage at this level for 2 min. Then determine the insulation resistance.

• g) Reduce the applied voltage to zero and short-circuit the terminals of the test equipment to discharge the voltage build-up in the module.

• h) Remove the short circuit and disconnect the test equipment from the module.

10.3.5 Test requirements

• no dielectric breakdown or surface tracking during step c);

• for modules with total area less than 0,1 m2, the insulation resistance shall not be less than 400 MΩ;

• for modules with total area larger than 0,1 m2 the measured insulation resistance times the area of the module shall not be less than 40 MΩ⋅m2.