PR S 40023 Flashcards
Insulation Testing
What is the purpose of insulation testing
to check for degradation or insulation defects which could potentially result in irregularities due to current leakage cutting out one or more control elements of a circuit.
what are methods to detect electrical leakage paths
monitoring of busbars using earth leakage detectors
measuring busbars to earth using test instruments
testing conductor insulation with test instruments
function testing of signalling circuits
visual examination of cables etc.
Responsibilities of signalling personnel regarding insulation testing
recording busbar to earth voltage, ELD testing and IR testing, visual inspection an reporting deterioration to the maintenance signal engineer
What are the requirements for the insulation test instrument
Type approved/ calibrated and in date/ good working condition. 500VDC 3mA.
What is the test earth normally used for insulation testing
the main earth bus in the location or a subsidiary earth bus bonded to the main earth.
what must be done to the test earth before using it for testing
a check to prove the test earth is satisfactory by measuring the test earth to an alternative temporary test earth.
what can the alternate earth used to check the test earth be
the ELD test earth, galvanised steel troughing, or a temporary electrode
can you use the rail as a test earth
no
what reading is ideal for a reference earth
less than 10k ohm, or a short circuit.
what is to be conducted before insulation testing of cables
a visual inspection for damage or deterioration as far as practical. correlation and ensure test equipment is working properly.
what needs to be done to replacement equipment before being installed
inspected to be in good condition and order
what are the ideal conditions to insulation resistance test cables and where is it recorded
in wet or damp conditions. on the insulation test record sheets
can wires or cable cores be removed from their terminals for testing
only when absolutely necessary, and only one wire should be removed at a time. the reconnection is to be tested.
list some equipment to be disconnected before testing begins
transformers, surge arrestors, timers, electronic track circuit equipment, computer based interlocking equipment
Should circuits be tested complete or in sections
the preference is divide circuits into internal wiring in locations, cables between locations and tail cables from trackside control equipment to trackside apparatus.
what are the methods to inspect ELDs being set off
insulation testing suspect circuits
operate signals/points to reproduce the fault
waiting for a train to reproduce the fault
inspect for water ingress or defect
what must be fitted to the fluke meter when testing
a 100k ohm shunt
how do you test bus bars with and without ELDs and how often
by busbar voltage to earth or operation of the test switch. performed every maintenance visit
what is classified internal wiring
wiring contained in relay rooms, signal boxes, level crossing huts, walk in enclosures, equipment location and cupboards.
how often is internal wiring tested with and without ELDs
without ELDs 4 years for PVC and 2 years for anything else.
with ELDs testing is not required.
method of insulation resistance testing for internal circuits
circuit to be disconnected at both ends. tested complete with all relays closed. tested to the same earth of racks or cupboards.
which cores are the preference to be tested in a multicore cable
the outer layer of cores
how often does non vital wiring require inspection and testing
every maintenance visit if connected to a bus bar.
every 2 years if connected into vital signalling ciruits
Minimum insulation reading for signal and train working telephone circuits
500k ohm
