Lesson 6

Voltage Do we need to MEASURE it? OR Do we need to DETECT it?

Test Lamps Test Lamps Neon Test Pencils/Screwdrivers Neon Test Pencils/Screwdrivers Voltage Probes Voltage Probes Steinel Combi-Check Steinel Combi-Check AC Voltage Probe AC Voltage Probe

Voltmeter Voltmeter Multimeter Multimeter Clamp meter Clamp meter Analogue Analogue Digital Digital Digital simulated Analogue Digital simulated Analogue

Last known earthly residence of automotive fuse used to replace original fuse Test leads survived intact

13.8 kV arced over to test probes Test leads destroyed

250V fuse didn’t open in time Poor quality leads and probes led to injury. Probe tips burned off Fingerprints burned into probes

Arc from transients (lightning, load switching) Voltage contact while in continuity or resistance Measuring voltage with test leads in current sockets Shock from accidental contact with live components Using meter or tester above rated voltage

Protection Independent certification to meet CAT III-1000 V or CAT IV 600 V

Overload protection in Ω up to the meter’s volt rating

Protection High fault current rated fuses Use meters / testers without current sockets

Protection Double insulated Recessed / shrouded Plugs/Sockets Finger guards CAT III – 1000 V Replace when damaged Test Leads

IEC New standard for low voltage “test, measurement and control equipment”. Provides much improved protection against “overvoltage impulse transients” - voltage spikes. Basis for: ANSI/ISA-S (US) CAN C22.2 No (CAN) EN :1993 (EUR) AS :2003 (Testers) AS :2004 (Leads)

The closer the location is to the power source, the higher the available fault current, the higher the category CATEGORIES: CAT I to CAT IV The greatest danger from transients is in the high categories, because they could trigger an arc blast IMPULSE TESTING: No failure allowed Meters must be tested by being hit with a specified number of transients, with specified peak voltages

CAT IV CAT III CAT II CAT I “Origin of installation” Supply Authority level and any outside cable runs Distribution wiring, including Consumer mains and Sub-circuits; permanently installed loads. Socket Outlets; plug-in loads. Protected electronic circuits

WITHIN each Category: There are designated “working voltages” (50, 150, 300, 600, 1000 V). A higher voltage has a higher transient withstand

CAT IV CAT III CAT II CAT IV – 600 V: 8 kV impulse CAT III – 600 V: 6 kV impulse CAT III – 1000 V: 8 kV impulse CAT II – 600 V: 4 kV impulse CAT II – 1000 V: 6 kV impulse

CAT III-600 V = 6 kV impulse 2 ohm test source CAT II-1000 V = 6 kV impulse 12 ohm test source The greater the source impedance, the lower the category: A CAT III-600 V 6k V test impulse has 6 times the current of a CAT II-1000 V 6 kV test impulse!

First know the category you are working in, then choose the appropriate voltage rating If you ever measure power circuits, you should use: CAT III-600 V OR CAT IV 600 V CAT III-1000 V OR AND CAT IV 600 V ORCAT III-1000 V test leads

CAT III-1000 V CAT IV-600 V CAT III-1000 V CAT III-600 V No meter is safe when improperly used

Don’t let test leads be a weak point CAT III-1000 V or CAT IV 600 V/CAT III 1000 V rating Double insulation Shrouded connectors Finger guards Insulation not damaged: not melted, cut, cracked, stretched Connectors: no insulation pulled away from end connectors Probe tips: not loose or broken off (too short)

Safe practices include but are not limited to: Whenever possible, work on de-energized circuits. Follow proper Isolation procedures. Use well maintained tools and appropriate safety gear Safety glasses, insulated tools, insulating gloves, flash suits, insulating mats, etc. Don’t work alone. Practice safe measurement techniques. Always connect the EARTH FIRST, ACTIVE SECOND. Disconnect the ACTIVE lead first, EARTHED lead second.