17th
Edition Installation Testers Glossary - Testing the Safety of Electrical Installation
All in one insulation testing A full automated procedure where the resistance between L-N, L-PE and N-PE are all performed with the single press of the test button.
Autosequence
Autosequencing is a method by which a series of installation tests are performed with a single press of the test button. By pressing the test button, the instrument will auto- matically start working through the list of tests, pausing where appropri- ate. Autosequence testing can be up to 5 times faster than conventional methods.
Continuity resistance test A 200 mA resistance test to ensure that the resistance between two points is suffi ciently low for the application.
Dead testing Testing on circuits that do not have a voltage applied to them (e.g. a conti- nuity or insulation test).
Electrical Installation safety testing This is a combination of dead circuit and live testing.
The dead circuit tests are: Continuity. Insulation.
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Earth resistance testing.
Live testing includes: Voltage measurement. Phase sequence.
Line impedance measurement. Loop impedance measurement. RCD testing.
These tests are performed in order to ensure that the requirements are met for the protection of persons, livestock and property against the risk of electric shock and to ensure that the automatic disconnection of the supply is performed correctly.
Earth resistance testing
Earth resistance testing is used on TN, TT and IT systems to ensure that
1. 2 Insulation resistance
The insulation is intended to pre- vent any contact with live parts and withstanding mechanical, chemi- cal, electrical and thermal stresses. The insulation resistance test is performed with a D.C. voltage on a dead system and the resistance must be above the minimum limit set out in the appropriate standards and regulations.
Loop impedance test
This is a live test used to measure the fault loop impedance between the line and earth conductor (some- times the neutral is required to pre- vent an RCD/RCBO from tripping during the test). This function can be used for both Z(e) and Z(s) testing.
Live testing
Performing tests on circuits that have a voltage applied to them (e.g. an RCD trip time test)
Line impedance test
This is a live test used to measure the impedance between the line and neutral conductor or between lines on a 3-phase system.
Loop impedance tables Various RCDs, fuse types and rat- ings can be selected on the test instrument. When a loop test is performed, the measured value is automatically compared to the maxi- mum values set out in the standards (BS7671:2008) and either a PASS or FAIL symbol will appear on-screen to inform the user if the measurement is within the required limits.
Phase rotation
A test used for determining the phase sequence of a 3-phase sys-
Accessories: page 1.35
the resistance of the earth electrode is suffi ciently low so that, in the case of a fault, a dangerous voltage does not appear on any parts of the instal- lation or on any appliances which have a connection to earth.
tem. Example results displayed on the tester are (1.2.3), (2,1,3).
RCD Auto
An automated function which per- forms RCD testing at x1/2, x1 and x5 current multipliers at both 0° and 180° automatically. This removes the need to walk repeatedly between the RCD and the test instrument to measure trip-times.
RCD Ramp test
A test which slowly ramps up the cur- rent between line and PE conductor until the RCD/RCBO trips. After this test, the current required to trip the RCD is displayed which can then be used to fi nd the cause of nuisance tripping occurring in a circuit.
Structure building
Design buildings in the instrument as they are laid out in the installation. This includes the distribution boards, circuits, sub-distribution boards and earth connections. This visual inter- pretation of the electrical installation makes the saving and recalling of test results quick and simple.
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