Table　1

　

NOTE：　Care　should　be　taken　on　equipment　operating　below　60　V　and　on　semiconductor　devices　to　ensure　that　no　damage　is　sustained　due　to　the　application　of　excessive　test　voltages.

　

When　an　insulation　test　is　made　on　a　circuit　incorporating　capacitors　of　a　total　capacitance　exceeding　2　microfarads,　an　insulation　tester　of　the　constant-voltage　type　should　be　used　in　order　to　ensure　that　accurate　test　readings　are　obtained.

The　periodic　testing　of　insulation　resistance　throughout　the　life　of　the　installation　and　comparison　with　previously　recorded　test　results　will　assist　with　detecting　deterioration　in　the　condition　of　a　circuit　or　apparatus.

　

(2)　A　test　for　insulation　resistance　should　be　applied　to　all　permanent　wiring　of　communications,　lighting　and　power　circuits　between　all　insulated　poles　and　earth　and,　where　practicable,　between　poles.　The　installation　may　be　sub-divided　to　any　desired　extent　and　appliances　may　be　disconnected　if　tests　give　results　lower　than　those　in　Table　2.

　

Table　2

　

NOTE：　Attention　is　drawn　to　the　importance　of　recording　the　temperature　of　windings　of　rotating　machines　at　the　same　time　as　the　insulation　resistance.　The　insulation　resistance　of　machine　windings　varies　considerably　with　temperature.　Corrected　values　may　be　obtained　by　reference　to　Figure　1.

　

3　High　Voltage　Tests

Equipment　rated　at　or　above　1　kV　and　assembled　on　site　should　be　subjected　to　a　high　voltage　dielectric　test　after　assembly.　Test　voltages　should　be　those　recommended　for　site　conditions　given　in　the　relevant　British　Standard.

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