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close this bookElectrical Installation - Basic Vocational Knowledge
close this folder8. Testing of installed plants
View the document(introduction...)
View the document8.1. Visual inspection
View the document8.2. Testing the insulation resistance
View the document8.3. Functional testing
View the document8.4. Summary

8.3. Functional testing

Part of functional testing is the current flow test being carried out in dead condition. Current flow testers rendering an optical or acoustic signal on the current flow are almost exclusively operated by torch batteries of 1.5 resp. 4.5 V!

Handling of current flow testers is very simple. By means of two test prods the test voltage will be applied to the conductor of the cable to be tested.

If there is no interruption in the conductor the current flow tester will give an optical or acoustic signal.

If there is no signal, there is an interruption in the conductor or in the plant.

By systematic encircling and searching the fault will have to be found and remedied.


Fig. 8.2. Current flow tester

1 cable (switch line), 2 conductor bridging (switch), 3 test line, 4 current flow tester

After applying the mains voltage the voltage condition of the plant will be established.

For that purpose two-pole voltage testers are employed. During testing the glow lamp will light, warning of the applied voltage. Similarly as in case of the insulation value check, testing by the voltage tester is done subsequently between the phase conductors and then between phase conductors and protective conductor resp. earth. It will be very important to ascertain functioning of the protective measure against too high a contact voltage. Function of neutralization, protective earthing and current-operated earth-leakage protection is being established by a loop measurement (of the protective conductor’s resistance). Also in this case testing is performed in live condition. This measurement is carried out between each phase conductor and the protective conductor. Connecting and disconnecting the measuring lines should, however, take place in dead condition.

Table 8.1. Testing and measuring devices

Current flow tester (bell, buzzer, glow lamp 4,5 V, telephone)

plant to be dead

current flow test

Hand generator

plant to be dead

insulation test

Voltage tester two-pole (load testing button or voltage meter)

plant to be live

functional test ascertaining voltage condition

Phase-sequence indicator

plant to be live

functional test ascertaining sequence of phase conductors

Test plug Loop measuring device

plant to be live

functional test, testing function of protective measure