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ABB Control OyLow Voltage Systems
Manual 1TFL 328 232
Responsible department:
KLS/KTDate:
31-08-01Language:
enProduct: Revision index: Page:
1/2
Prepared:
EsKChecked: Approved: File No:
INSTALLATION, OPERATION AND MAINTENANCE INSTRUCTIONS
MEASURING OF INSULATION RESISTANCE
Insulation resistance of the electrical equipment is measured
prior to the commissioning. Direct voltageis used for the measuring
with the minimum values shown in the table underneath.
Rated voltageof circuit
Test voltage
V
Insulation resistance
M
SELV and PELV 250 0,25
500 V except the a.m.systems
500 0,5
Over 500 V 1000 1,0
Resistance is measured using a megger on a dead switchboard and
it can be carried out withoutconnection of the current-using
equipment to the network.Megger must be capable to feed the a.m.
test voltage with a current of 1 mA.
In the TN-S network phase and neutral conductors can be
connected in parallel and carry out themeasuring between the
connected conductors and earth. In the TN-C network the
PEN-conductor isearthed and the measuring is carried out between
the connected phase conductors and earth.
For the comprehensive measuring of the switchboard or its part,
all mechanical switches, e.g. mainswitch and MCBs for outgoing
cables, must be in I-position and fuses in place.
If any circuit or part of circuit is equipped with a contactor
or analogous device, which disconnects allthe poles of the circuit
from the measuring circuit, the circuit after the contactor must be
measuredseparately.
Use a megger for measurings. Insulation resistance is to be 1
M
NOTE!
Measuring of insulation resistance must be performed only on
dead equipment.
Be sure that supply is switched off
control voltage is switched off
relays are switched off
Be careful not to damage electronic equipment in the measuring
circuit (as a rule, new devicesendure). Insulation resistance can
be measured only between connected phases and neutrals
andearth.
Do not touch terminals or wires of the gauge during the
measuring!
Object with capacitance, e.g. a long cable, is charged up to
voltage 500 V during the measuring. Donot forget to discharge it,
if the gauge does not discharge it automatically!
Follow the instructions of the manufacturer of the gauge.
8/13/2019 1tfl 328 232
2/2
ABB Control OyLow Voltage Systems
Manual 1TFL 328 232
Responsible department:
KLS/KTDate:
31-08-01Language:
enProduct: Revision index: Page:
2/2
Prepared:
EsKChecked: Approved: File No:
INSTALLATION, OPERATION AND MAINTENANCE INSTRUCTIONS
MEASURING OF INSULATION RESISTANCE
Procedure Required measurement Remarks
1 Between the outer conductorsand the protective conductor
2 Between the neutral andprotective conductor
Separate PE- and N-conductors!
This procedure is not requiredin the TN-C network
3 Between the outer conductors This procedure is not
required:
if the cable includes anearthed conductor or shield
for switching leads oflighting circuits
4 Between the outer conductorsand neutral conductor
